@article{aimone_giauque_hawkes_2023, title={Fungal Symbionts Generate Water-Saver and Water-Spender Plant Drought Strategies via Diverse Effects on Host Gene Expression}, ISSN={["2471-2906"]}, DOI={10.1094/PBIOMES-01-22-0006-FI}, abstractNote={Foliar fungal endophytes are known to alter plant physiology but the mechanisms by which they do so remain poorly understood. We focused on how plant gene expression was altered by six fungal strains that generated “water-saver” and “water-spender” drought physiologies in a C4 grass, Panicum hallii. Water-saver physiologies have lower plant water loss, improved wilt resistance, and higher survival compared with water-spender strategies. We expected that fungi within each functional group would have similar effects on P. hallii, and this was largely true for plant physiology but not for plant gene expression. When we focused only on genes that were differentially expressed relative to fungus-free controls, we found surprisingly little overlap in plant differentially expressed genes or gene regulatory pathways across the fungal treatments, including within and between the water-saver and water-spender strategies. Nevertheless, using lasso regression, we identified a small subset of genes that predicted 39 and 53% of the variation in plant wilt resistance and water loss, respectively. These results suggest that fungal effects on plant transcription may identify how they extend the plant phenotype, and the comparison across multiple fungi allows us to differentiate broadly fungal-responsive plant genes versus those plant genes that respond only to single fungal taxa. The genes identified here could be targeted for future study to understand their function and, ultimately, represent candidates for precision breeding efforts to increase plant drought tolerance. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license .}, journal={PHYTOBIOMES JOURNAL}, author={Aimone, Catherine D. and Giauque, Hannah and Hawkes, Christine V.}, year={2023}, month={Mar} }
 @article{heckman_rueda_bonnette_aspinwall_khasanova_hawkes_juenger_fay_2022, title={Legacies of precipitation influence primary production in Panicum virgatum}, volume={11}, ISSN={["1432-1939"]}, DOI={10.1007/s00442-022-05281-x}, journal={OECOLOGIA}, author={Heckman, Robert W. and Rueda, Austin and Bonnette, Jason E. and Aspinwall, Michael J. and Khasanova, Albina and Hawkes, Christine V. and Juenger, Thomas E. and Fay, Philip A.}, year={2022}, month={Nov} }
 @article{evans_allison_hawkes_2022, title={Microbes, memory and moisture: Predicting microbial moisture responses and their impact on carbon cycling}, volume={3}, ISSN={["1365-2435"]}, url={https://doi.org/10.1111/1365-2435.14034}, DOI={10.1111/1365-2435.14034}, abstractNote={Abstract Soil moisture is a major driver of microbial activity and thus, of the release of carbon (C) into the Earth's atmosphere. Yet, there is no consensus on the relationship between soil moisture and microbial respiration, and as a result, moisture response functions are a poorly constrained aspect of C models. In addition, models assume that the response of microbial respiration to moisture is the same for all ecosystems, regardless of climate history, an assumption that many empirical studies have challenged. These gaps in understanding of the microbial respiration response to moisture contribute to uncertainty in model predictions. We review our understanding of what drives microbial moisture response, highlighting evidence that historical precipitation can influence both responses to moisture and sensitivity to drought. We present two hypotheses, the ‘climate history hypothesis’, where we predict that baseline moisture response functions change as a function of precipitation history, and the ‘drought legacy hypothesis’, in which we suggest that the intensity and frequency of historical drought have shaped microbial communities in ways that will control moisture responses to contemporary drought. Underlying mechanisms include biological selection and filtering of the microbial community by rainfall regimes, which result in microbial traits and trade‐offs that shape function. We present an integrated modelling and empirical approach for understanding microbial moisture responses and improving models. Standardized measures of moisture response (respiration rate across a range of moistures) and accompanying microbial properties are needed across sites. These data can be incorporated into trait‐based models to produce generalized moisture response functions, which can then be validated and incorporated into conventional and microbially explicit ecosystem models of soil C cycling. Future studies should strive to analyse realistic moisture conditions and consider the role of environmental factors and soil structure in microbial response. Microbes are the engines that drive C storage and are sensitive to changes in rainfall. A greater understanding of the factors that govern this sensitivity could be a key part of improving predictions of soil C dynamics, climate change and C‐climate feedbacks. Read the free Plain Language Summary for this article on the Journal blog.}, journal={FUNCTIONAL ECOLOGY}, publisher={Wiley}, author={Evans, Sarah and Allison, Steven and Hawkes, Christine}, year={2022}, month={Mar} }
 @article{sandy_bui_aba_ruiz_paszalek_connor_hawkes_2022, title={Plant Host Traits Mediated by Foliar Fungal Symbionts and Secondary Metabolites}, volume={6}, ISSN={["1432-184X"]}, url={https://doi.org/10.1007/s00248-022-02057-x}, DOI={10.1007/s00248-022-02057-x}, journal={MICROBIAL ECOLOGY}, author={Sandy, Moriah and Bui, Tina I. and Aba, Kenia Segura and Ruiz, Nestor and Paszalek, John and Connor, Elise W. and Hawkes, Christine V.}, year={2022}, month={Jun} }
 @article{leizeaga_hicks_manoharan_hawkes_rousk_2021, title={Drought legacy affects microbial community trait distributions related to moisture along a savannah grassland precipitation gradient}, volume={109}, ISSN={["1365-2745"]}, DOI={10.1111/1365-2745.13550}, abstractNote={Ecosystem models commonly use stable-state assumptions to predict responses of soil microbial functions to environmental change. However, past climatic conditions can shape microbial functional responses resulting in a ‘legacy effect’. For instance, exposure to drier conditions in the field may shape how soil microbial communities respond to subsequent drought and drying and rewetting (DRW) events. We investigated microbial tolerance to low moisture levels (‘resistance’) and ability to recover after a DRW perturbation (‘resilience’) across a steep precipitation gradient in Texas, USA. Although differences in precipitation regime did not result in differences in resistance and resilience of soil microbes, microbial communities appeared to be generally resilient and resistant across the gradient, suggesting that frequent exposure to drought had characterised the trait distributions of microbial communities. Moreover, microbial communities from historically drier sites used carbon more efficiently during a DRW perturbation suggesting that long-term drought history leaves a legacy effect on microbial functions. This may have been due to an indirect effect of drought caused via precipitation-induced differences in primary productivity, influencing the availability of soil organic matter to microbes. Alternatively, different exposures to drought might have shaped the microbial ‘readiness’ to cope with the DRW disturbance. Microbial community composition was also linked to drought history, but was unrelated to variation in function. Synthesis. Exposure to drought can have both direct and indirect effects on soil microbial communities, which can result in lasting legacy effects on the functions they control.}, number={9}, journal={JOURNAL OF ECOLOGY}, author={Leizeaga, Ainara and Hicks, Lettice C. and Manoharan, Lokeshwaran and Hawkes, Christine V. and Rousk, Johannes}, year={2021}, month={Sep}, pages={3195–3210} }
 @article{hawkes_kjoller_raaijmakers_riber_christensen_rasmussen_christensen_dahl_westergaard_nielsen_et al._2021, title={Extension of Plant Phenotypes by the Foliar Microbiome}, volume={72}, ISSN={["1545-2123"]}, DOI={10.1146/annurev-arplant-080620-114342}, abstractNote={The foliar microbiome can extend the host plant phenotype by expanding its genomic and metabolic capabilities. Despite increasing recognition of the importance of the foliar microbiome for plant fitness, stress physiology, and yield, the diversity, function, and contribution of foliar microbiomes to plant phenotypic traits remain largely elusive. The recent adoption of high-throughput technologies is helping to unravel the diversityand spatiotemporal dynamics of foliar microbiomes, but we have yet to resolve their functional importance for plant growth, development, and ecology. Here, we focus on the processes that govern the assembly of the foliar microbiome and the potential mechanisms involved in extended plant phenotypes. We highlight knowledge gaps and provide suggestions for new research directions that can propel the field forward. These efforts will be instrumental in maximizing the functional potential of the foliar microbiome for sustainable crop production.}, journal={ANNUAL REVIEW OF PLANT BIOLOGY, VOL 72, 2021}, author={Hawkes, Christine V. and Kjoller, Rasmus and Raaijmakers, Jos M. and Riber, Leise and Christensen, Svend and Rasmussen, Simon and Christensen, Jan H. and Dahl, Anders Bjorholm and Westergaard, Jesper Cairo and Nielsen, Mads and et al.}, year={2021}, pages={823–846} }
 @article{whitaker_giauque_timmerman_birk_hawkes_2021, title={Local Plants, Not Soils, Are the Primary Source of Foliar Fungal Community Assembly in a C4 Grass}, volume={8}, ISSN={["1432-184X"]}, url={https://doi.org/10.1007/s00248-021-01836-2}, DOI={10.1007/s00248-021-01836-2}, journal={MICROBIAL ECOLOGY}, publisher={Springer Science and Business Media LLC}, author={Whitaker, Briana K. and Giauque, Hannah and Timmerman, Corey and Birk, Nicolas and Hawkes, Christine V}, year={2021}, month={Aug} }
 @article{zhalnina_hawkes_shade_firestone_pett-ridge_2021, title={Managing Plant Microbiomes for Sustainable Biofuel Production}, volume={5}, ISSN={["2471-2906"]}, url={https://doi.org/10.1094/PBIOMES-12-20-0090-E}, DOI={10.1094/PBIOMES-12-20-0090-E}, abstractNote={The development of environmentally sustainable, economical, and reliable sources of energy is one of the great challenges of the 21st century. Large-scale cultivation of cellulosic feedstock crops (henceforth, bioenergy crops) is considered one of the most promising renewable sources for liquid transportation fuels. However, the mandate to develop a viable cellulosic bioenergy industry is accompanied by an equally urgent mandate to deliver not only cheap reliable biomass but also ecosystem benefits, including efficient use of water, nitrogen, and phosphorous; restored soil health; and net negative carbon emissions. Thus, sustainable bioenergy crop production may involve new agricultural practices or feedstocks and should be reliable, cost effective, and minimal input, without displacing crops currently grown for food production on fertile land. In this editorial perspective for the Phytobiomes Journal Focus Issue on Phytobiomes of Bioenergy Crops and Agroecosystems, we consider the microbiomes associated with bioenergy crops, the effects beneficial microbes have on their hosts, and potential ecosystem impacts of these interactions. We also address outstanding questions, major advances, and emerging biotechnological strategies to design and manipulate bioenergy crop microbiomes. This approach could simultaneously increase crop yields and provide important ecosystem services for a sustainable energy future.}, number={1}, journal={PHYTOBIOMES JOURNAL}, publisher={Scientific Societies}, author={Zhalnina, Kateryna and Hawkes, Christine and Shade, Ashley and Firestone, Mary K. and Pett-Ridge, Jennifer}, year={2021}, pages={3–13} }
 @article{lee_hawkes_2021, title={Plant and Soil Drivers of Whole-Plant Microbiomes: Variation in Switchgrass Fungi from Coastal to Mountain Sites}, volume={5}, ISSN={["2471-2906"]}, url={https://doi.org/10.1094/PBIOMES-07-20-0056-FI}, DOI={10.1094/PBIOMES-07-20-0056-FI}, abstractNote={Plant-associated microbial diversity is regulated by dispersal from local and regional species pools, as well as filtering by the environment and plant host. However, few studies have simultaneously examined microbial community variation in multiple plant-associated habitats across multiple sites; thus, it is unclear what scales and filters are most important in shaping whole-plant microbiome diversity. To address this, we characterized fungal communities associated with switchgrass (Panicum virgatum L.) leaves, roots, and soils within and across 14 stands spanning mountain to coastal ecoregions of North Carolina. Niche differences at small scales (i.e., less than half a kilometer) best explained variation in fungal communities. However, the specific environmental drivers of fungal community composition differed for leaves, roots, and soils. Leaf and root fungi were both affected by plant height, whereas soil fungi were controlled by stand age. Different soil properties were important for fungi in all plant-associated habitats: K, P, and pH for leaves; clay, Mn, and pH for roots; and clay, dissolved organic carbon, total inorganic N, and Cu for soils. Climate and spatial variables were not significant, further supporting the key role of plant and soil properties. Advances such as these will help us explain, predict, and manipulate microbial assemblages that support plant growth in managed and natural systems.}, number={1}, journal={PHYTOBIOMES JOURNAL}, publisher={Scientific Societies}, author={Lee, Marissa R. and Hawkes, Christine V}, year={2021}, pages={69–79} }
 @article{kivlin_hawkes_papeş_treseder_averill_2021, title={The future of microbial ecological niche theory and modeling}, volume={231}, url={https://doi.org/10.1111/nph.17373}, DOI={10.1111/nph.17373}, abstractNote={This article is a Commentary on Davison et al . (2021), 231 : 763–776 .}, number={2}, journal={New Phytologist}, publisher={Wiley}, author={Kivlin, Stephanie N. and Hawkes, Christine V. and Papeş, Monica and Treseder, Kathleen K. and Averill, Colin}, year={2021}, month={Jul}, pages={508–511} }
 @article{lee_hawkes_2021, title={Widespread co-occurrence of Sebacinales and arbuscular mycorrhizal fungi in switchgrass roots and soils has limited dependence on soil carbon or nutrients}, volume={3}, ISSN={["2572-2611"]}, url={https://doi.org/10.1002/ppp3.10181}, DOI={10.1002/ppp3.10181}, abstractNote={Societal Impact Statement This work addresses a novel group of Sebacinales mycorrhizal fungi being considered for development as inoculants in managed ecosystems because of their potential access to nutrients in soil organic matter. By comparing the diversity, distributions, and abundances of the Sebacinales with the more common arbuscular mycorrhizal fungi in switchgrass, a biofuel crop, we demonstrate that current suggestions for a Sebacinales revolution in agriculture should be tempered by their ecology. In particular, Sebacinales are rare compared to arbuscular mycorrhizal fungi, and are only weakly associated with soil carbon, suggesting that ideas about improved soil carbon cycling associated with Sebacinales need to be sufficiently studied across a range of environmental conditions prior to their consideration for broad‐spectrum soil inoculants. Summary Arbuscular mycorrhizal (AM) fungi are widespread and important root symbionts, but recent work suggests that Sebacinales fungi may play an equally important role in both plant success and ecosystem carbon and nutrient cycling based on their worldwide occurrence and putative access to organic matter. However, the ecological impacts of Sebacinales will depend on their abundance and distribution relative to AM fungi and environmental soil carbon and nutrient patterns, which remain unexplored. We characterized Glomeromycota and Sebacinales fungi in switchgrass ( Panicum virgatum L.) roots and soils across 14 sites with diverse soil conditions. We examined group richness differences, co‐occurrence patterns, and how the relative abundance of these fungi related to soil carbon, nutrient stoichiometry, and host size. Sebacinales were widespread, but less diverse, common, and abundant than Glomeromycota. Moreover, co‐occurrences were predominantly random, suggesting relatively few interactions between these groups. Sebacinales increased relative to Glomeromycota in soils with more carbon, but explanatory power was limited. Based on our findings, we suggest that Sebacinales are likely complementary to AM fungi in roots. Expectations that Sebacinales have large effects on soil carbon and nutrient cycling may need to be reconsidered, at least based on their limited abundances relative to AM fungi in switchgrass. This is an important consideration as Sebacinales are candidates for use as inoculants in managed ecosystems.}, number={5}, journal={PLANTS PEOPLE PLANET}, publisher={Wiley}, author={Lee, Marissa R. and Hawkes, Christine V}, year={2021}, month={Sep}, pages={614–626} }
 @article{kiniry_arthur_banick_fritschi_wu_hawkes_2020, title={Effects of Plant-Soil Feedback on Switchgrass Productivity Related to Microbial Origin}, url={https://doi.org/10.3390/agronomy10121860}, DOI={10.3390/agronomy10121860}, abstractNote={A great deal of effort has been applied to maximizing switchgrass (Panicum virgatum L.) production for bioenergy by leveraging existing local adaptation to climate and via nutrient management in this perennial grass crop. However, the biotic component of soils can also affect plant production and long-term suitability at a given site. Here, we tested how productivity of four switchgrass cultivars were affected by four microbial sources from the Great Plains. All inoculum soil sources were previously conditioned by a mixture of switchgrass cultivars, allowing us to explicitly address plant-soil feedback effects. Microbial soil inocula were added to a consistent background soil to avoid physicochemical variation across the sources. We found that the soil microbial inoculum source mattered more than cultivar in determining switchgrass biomass. The addition of microbes resulted in smaller plants, with the largest plants found on control soils with no inoculum, but some inocula were less negative than others. There was no geographic matching between cultivars and soil microbial inoculum, suggesting little local adaptation to the biotic component of soils. In addition, measurements of fungal root colonization suggest that fungi are not responsible for the observed patterns. Based on these results, we suggest that switchgrass cultivation could benefit from considering effects of the soil biota. Additional work is needed to generalize these patterns over time, to a wider geographic area, and to a broader range of cultivars.}, journal={Agronomy}, author={Kiniry, James R. and Arthur, Caroline E. and Banick, Katherine M. and Fritschi, Felix B. and Wu, Yanqi and Hawkes, Christine V.}, year={2020}, month={Nov} }
 @article{hawkes_shinada_kivlin_2020, title={Historical climate legacies on soil respiration persist despite extreme changes in rainfall}, volume={143}, ISSN={["0038-0717"]}, DOI={10.1016/j.soilbio.2020.107752}, abstractNote={How soil microbial respiration responds to climate change can be constrained by historical climate. Understanding the duration of such legacy effects is key to determining how much they matter for projecting future ecosystem carbon cycling. Here, we tested whether extreme changes in rainfall could overcome constraints imposed by historical rainfall on how soil respiration responds to moisture. We predicted that larger shifts in rainfall regime would alter the magnitude or sensitivity (slope) of the respiration response to moisture compared to smaller changes in rainfall relative to historical conditions. Over 4.5 years, we imposed rain treatments ranging from extreme dry to extreme wet conditions that varied by ~400%, as well as ambient and historical mean rainfall controls. Rain treatments were applied to shortgrass or tallgrass vegetation that represented lower and higher biomass inputs, respectively, to test how shifts in soil resources might affect respiration moisture responses. We found high resistance to altered rainfall in the field, with persistent legacies indicated by no change in the respiration response to moisture among treatment and control rain treatments. The intrinsic respiration response to moisture under controlled laboratory conditions was also unaffected by field rain treatments. In response to field vegetation treatment, there was 10–30% more soil respiration in tallgrass compared to shortgrass that was paralleled by an increase in soil dissolved organic carbon, but no change in moisture sensitivity consistent with independent resource and climate effects. Soil bacteria and fungi were unchanged across all treatments and were largely generalists, suggesting high community as well as functional resistance to change. Climate legacies on soil microbial communities have the potential to modify our expectations for the rate of acclimation and adaptation to altered climate conditions.}, journal={SOIL BIOLOGY & BIOCHEMISTRY}, author={Hawkes, Christine V and Shinada, Mio and Kivlin, Stephanie N.}, year={2020}, month={Apr} }
 @article{heckman_khasanova_johnson_weber_bonnette_aspinwall_reichmann_juenger_fay_hawkes_2020, title={Plant biomass, not plant economics traits, determines responses of soil CO2 efflux to precipitation in the C-4 grass Panicum virgatum}, volume={108}, ISSN={["1365-2745"]}, DOI={10.1111/1365-2745.13382}, abstractNote={Abstract Plant responses to major environmental drivers like precipitation can influence important aspects of carbon (C) cycling like soil CO 2 efflux ( ). These responses may be predicted by two independent classes of drivers: plant size—larger plants respire more and produce a larger quantity of labile C, and plant economics—plants possessing more acquisitive plant economics strategies (i.e. high metabolic rate and tissue nutrient content) produce higher‐quality tissue that respires rapidly and decomposes quickly. At two sites in central Texas, USA with similar climates and differing soil characteristics, we examined the response of eight Panicum virgatum genotypes to three annual precipitation levels defined by the driest, average and wettest years from each site's precipitation history. We evaluated the individual and joint influence of plant genotypes and precipitation on and traits related to plant economics and plant size. We then used confirmatory path analysis to evaluate whether effects of precipitation on were in part related to effects of precipitation on plant economics traits or size (‘mediated’ effects). These genotypes exhibited variation in plant economics traits and above‐ground net primary productivity (ANPP), an above‐ground measure of plant size. Increasing precipitation increased and ANPP more than plant economics traits. At both sites, ANPP was the best predictor of . Moreover, the sites differed in the ways that plant size and plant economics traits combined with precipitation to influence . At the Austin site, the positive effect of precipitation on was mediated primarily by ANPP, offset by a smaller effect of leaf nitrogen content; no direct precipitation effect was detected. At the Temple site, increasing precipitation had positive direct and ANPP‐mediated effects on . This suggests that greater water limitation at Austin may strengthen the links between plant size and . Synthesis . Estimates of C cycling can be improved by accounting for mediation of precipitation effects on by plant economics traits and plant size in resource‐limited environments.}, number={5}, journal={JOURNAL OF ECOLOGY}, author={Heckman, Robert W. and Khasanova, Albina R. and Johnson, Nicholas S. and Weber, Soren and Bonnette, Jason E. and Aspinwall, Michael J. and Reichmann, Lara G. and Juenger, Thomas E. and Fay, Philip A. and Hawkes, Christine V}, year={2020}, month={Sep}, pages={2095–2106} }
 @article{cooperdock_hawkes_xu_breecker_2020, title={Soil Water Content and Soil Respiration Rates Are Reduced for Years Following Wildfire in a Hot and Dry Climate}, volume={34}, ISSN={["1944-9224"]}, DOI={10.1029/2020GB006699}, abstractNote={Abstract Increasing fire severity and frequency may stress ecosystems also impacted by climate change. We studied the physical limitations to regeneration after fire in an ecosystem that already experiences high summer temperatures and drought and is therefore a possible analog of the future. We compared soil respiration as an indicator of microbial activity in burned and unburned forest soils in central Texas, where two recent wildfires have occurred (2011 and 2015). We also measured soil temperature, water content, soil water δ 18 O and δD values, total C, N, pH, and δ 13 C values of total organic matter. Burned soils had lower total C and N than unburned soils; however, lab‐based respiration measurements, which controlled for temperature and water content, suggest that microbial activity in burned and unburned soils are similar. Conversely, field measurements show that during hot and dry months respiration rates in burned soils were much lower than they were in unburned soils due to differences in soil temperature and water content. Soil temperature at 5 cm reached 60°C in burned soils due to the removal of canopy cover, the removal of organic matter insulation, and the deposition of black ash on the soil surface. Higher temperatures increased evaporation as indicated by significantly lower deuterium excess of water in soils burned in 2015 than unburned soils. If the disturbance of vegetation by fire is substantial enough, the resulting perturbations to soils persist for years, most importantly increased heat absorption which results in lower water contents and ultimately reduced microbial activity.}, number={12}, journal={GLOBAL BIOGEOCHEMICAL CYCLES}, author={Cooperdock, Sol C. and Hawkes, Christine V. and Xu, Derry R. and Breecker, Daniel O.}, year={2020}, month={Dec} }
 @article{crawford_hawkes_2020, title={Soil precipitation legacies influence intraspecific plant–soil feedback}, volume={101}, url={https://doi.org/10.1002/ecy.3142}, DOI={10.1002/ecy.3142}, abstractNote={Abstract Feedbacks between plants and soil microbial communities can play an important role in structuring plant communities. However, little is known about how soil legacies caused by environmental disturbances such as drought and extreme precipitation events may affect plant–soil feedback or whether plant–soil feedback operates within species as it does between species. If soil legacies alter plant–soil feedback among genotypes within a plant species, then soil legacies may alter the diversity within plant populations. We conducted a fully factorial pairwise plant–soil feedback experiment to test how precipitation legacies influenced intraspecific plant–soil feedbacks among three genotypes of a dominant grass species, Panicum virgatum . Panicum virgatum experienced negative intraspecific plant–soil feedback, i.e., genotypes generally performed worse on soil from the same genotype than different genotypes. Soil precipitation legacies reversed the rank order of the strength of negative feedback among the genotypes. Feedback is often positively correlated with plant relative abundance. Therefore, our results suggest that soil precipitation legacies may alter the genotypic composition of P. virgatum populations, favoring genotypes that develop less negative feedback. Changes in intraspecific diversity will likely further affect community structure and ecosystem functioning, and may constrain the ability of populations to respond to future changes in climate.}, number={10}, journal={Ecology}, publisher={Wiley}, author={Crawford, Kerri M. and Hawkes, Christine V.}, year={2020}, month={Oct} }
 @article{kivlin_hawkes_2020, title={Spatial and temporal turnover of soil microbial communities is not linked to function in a primary tropical forest}, volume={101}, url={https://doi.org/10.1002/ecy.2985}, DOI={10.1002/ecy.2985}, abstractNote={Abstract The spatial and temporal linkages between turnover of soil microbial communities and their associated functions remain largely unexplored in terrestrial ecosystems. Yet defining these relationships and how they vary across ecosystems and microbial lineages is key to incorporating microbial communities into ecological forecasts and ecosystem models. To define linkages between turnover of soil bacterial and fungal communities and their function we sampled fungal and bacterial composition, abundance, and enzyme activities across a 3‐ha area of wet tropical primary forest over 2 yr. We show that fungal and bacterial communities both exhibited temporal turnover, but turnover of both groups was much lower than in temperate ecosystems. Turnover over time was driven by gain and loss of microbial taxa and not changes in abundance of individual species present in multiple samples. Only fungi varied over space with idiosyncratic variation that did not increase linearly with distance among sampling locations. Only phosphorus‐acquiring enzyme activities were linked to shifts in septate, decomposer fungal abundance; no enzymes were affected by composition or diversity of fungi or bacteria. Although temporal and spatial variation in composition was appreciable, because turnover of microbial communities did not alter the functional repertoire of decomposing enzymes, functional redundancy among taxa may be high in this ecosystem. Slow temporal turnover of tropical soil microbial communities and large functional redundancy suggests that shifts in abundance of particular functional groups may capture ecosystem function more accurately than composition in these heterogeneous ecosystems.}, number={4}, journal={Ecology}, publisher={Wiley}, author={Kivlin, Stephanie N. and Hawkes, Christine V.}, year={2020}, month={Apr} }
 @article{hawkes_bull_lau_2020, title={Symbiosis and stress: how plant microbiomes affect host evolution}, volume={375}, url={https://doi.org/10.1098/rstb.2019.0590}, DOI={10.1098/rstb.2019.0590}, abstractNote={Existing paradigms for plant microevolution rarely acknowledge the potential impacts of diverse microbiomes on evolutionary processes. Many plant-associated microorganisms benefit the host via access to resources, protection from pathogens, or amelioration of abiotic stress. In doing so, they alter the plant's perception of the environment, potentially reducing the strength of selection acting on plant stress tolerance or defence traits or altering the traits that are the target of selection. We posit that the microbiome can affect plant microevolution via (1) manipulation of plant phenotypes in ways that increase plant fitness under stress and (2) direct microbial responses to the environment that benefit the plant. Both mechanisms might favour plant genotypes that attract or stimulate growth of the most responsive microbial populations or communities. We provide support for these scenarios using infectious disease and quantitative genetics models. Finally, we discuss how beneficial plant–microbiome associations can evolve if traditional mechanisms maintaining cooperation in pairwise symbioses, namely partner fidelity, partner choice and fitness alignment, also apply to the interactions between plants and diverse foliar and soil microbiomes. To understand the role of the plant microbiome in host evolution will require a broad ecological understanding of plant–microbe interactions across both space and time. This article is part of the theme issue ‘The role of the microbiome in host evolution'.}, number={1808}, journal={Philosophical Transactions of the Royal Society B: Biological Sciences}, publisher={The Royal Society}, author={Hawkes, Christine V. and Bull, James J. and Lau, Jennifer A.}, year={2020}, month={Sep}, pages={20190590} }
 @article{giauque_connor_hawkes_2019, title={Endophyte traits relevant to stress tolerance, resource use and habitat of origin predict effects on host plants}, volume={221}, ISSN={["1469-8137"]}, url={https://doi.org/10.1111/nph.15504}, DOI={10.1111/nph.15504}, abstractNote={Summary All terrestrial plants are colonized by foliar endophytic fungi that can affect plant growth and physiology, but the prediction of these effects on the plant host remains a challenge. Here, we examined three paradigms that potentially control how endophytes affect plant hosts: habitat adaptation, evolutionary history and functional traits. We screened 35 plant–endophyte pairings in a microcosm experiment under well‐watered and drought conditions with Panicum virgatum as the host. We related the measured plant responses to fungal phylogenetic relatedness, characteristics of fungal habitats across a rainfall gradient and functional traits of the fungi related to stress tolerance and resource use. The functional traits and habitat characteristics of the fungi predicted 26–53% of endophyte‐mediated effects on measures of plant growth, physiology and survival. Overall, survival was higher for plants grown with more stress‐tolerant fungi, and aboveground biomass was enhanced by fungi from warmer and drier habitats. Plant growth and physiology were also dependent on fungal resource use indicators; however, specific predictors were dependent on water availability. Simple ecological traits of foliar endophytic fungi observed in culture can translate to symbiotic lifestyles. These findings offer new insights and key testable predictions for likely pathways by which endophytes benefit the plant host.}, number={4}, journal={NEW PHYTOLOGIST}, publisher={Wiley}, author={Giauque, Hannah and Connor, Elise W. and Hawkes, Christine V.}, year={2019}, month={Mar}, pages={2239–2249} }
 @article{ecological mechanisms underlying soil bacterial responses to rainfall along a steep natural precipitation gradient_2018, url={http://dx.doi.org/10.1093/femsec/fiy001}, DOI={10.1093/femsec/fiy001}, abstractNote={Changes in the structure and function of soil microbial communities can drive substantial ecosystem feedbacks to altered precipitation. However, the ecological mechanisms underlying community responses to environmental change are not well understood. We used an 18-month soil reciprocal transplant experiment along a steep precipitation gradient to quantify how changes in rainfall affected bacterial community structure. We also conducted an enhanced dispersal treatment to ask whether higher immigration rates of taxa from the surrounding environment would accelerate community responses to climate change. Finally, we addressed how the composition of soil bacteria communities was related to the functional response of soil respiration to moisture in these treatments. Bacterial community structure (OTU abundance) and function (respiration rates) changed little in response to manipulation of either rainfall environment or dispersal rates. Although most bacteria were ecological generalists, a subset of specialist taxa, over 40% of which were Actinobacteria, tended to be more abundant in the rainfall environment that matched their original conditions. Bacteria community composition was an important predictor of the respiration response to moisture. Thus, the high compositional resistance of microbial communities dictated respiration responses to altered rainfall in this system.}, journal={FEMS Microbiology Ecology}, year={2018}, month={Feb} }
 @article{connor_hawkes_2018, title={Effects of extreme changes in precipitation on the physiology of C4 grasses}, volume={188}, url={https://doi.org/10.1007/s00442-018-4212-5}, DOI={10.1007/s00442-018-4212-5}, number={2}, journal={Oecologia}, publisher={Springer Nature}, author={Connor, Elise W. and Hawkes, Christine V.}, year={2018}, month={Oct}, pages={355–365} }
 @article{heterogeneity in arbuscular mycorrhizal fungal communities may contribute to inconsistent plant-soil feedback in a neotropical forest_2018, url={http://dx.doi.org/10.1007/s11104-018-3777-4}, DOI={10.1007/s11104-018-3777-4}, journal={Plant and Soil}, year={2018}, month={Nov} }
 @article{legacies in switchgrass resistance to and recovery from drought suggest that good years can sustain plants through bad years_2018, url={http://dx.doi.org/10.1007/s12155-017-9879-7}, DOI={10.1007/s12155-017-9879-7}, journal={BioEnergy Research}, year={2018}, month={Mar} }
 @article{soil carbon cycling proxies: understanding their critical role in predicting climate change feedbacks_2018, url={http://dx.doi.org/10.1111/gcb.13926}, DOI={10.1111/gcb.13926}, abstractNote={The complexity of processes and interactions that drive soil C dynamics necessitate the use of proxy variables to represent soil characteristics that cannot be directly measured (correlative proxies), or that aggregate information about multiple soil characteristics into one variable (integrative proxies). These proxies have proven useful for understanding the soil C cycle, which is highly variable in both space and time, and are now being used to make predictions of the fate and persistence of C under future climate scenarios. However, the C pools and processes that proxies represent must be thoughtfully considered in order to minimize uncertainties in empirical understanding. This is necessary to capture the full value of a proxy in model parameters and in model outcomes. Here, we provide specific examples of proxy variables that could improve decision-making, and modeling skill, while also encouraging continued work on their mechanistic underpinnings. We explore the use of three common soil proxies used to study soil C cycling: metabolic quotient, clay content, and physical fractionation. We also consider how emerging data types, such as genome-sequence data, can serve as proxies for microbial community activities. By examining some broad assumptions in soil C cycling with the proxies already in use, we can develop new hypotheses and specify criteria for new and needed proxies.}, journal={Global Change Biology}, year={2018}, month={Mar} }
 @article{tropical tree species effects on soil ph and biotic factors and the consequences for macroaggregate dynamics_2018, url={http://dx.doi.org/10.3390/f9040184}, DOI={10.3390/f9040184}, abstractNote={Physicochemical and biotic factors influence the binding and dispersivity of soil particles, and thus control soil macroaggregate formation and stability. Although soil pH influences dispersivity, it is usually relatively constant within a site, and thus not considered a driver of aggregation dynamics. However, land-use change that results in shifts in tree-species composition can result in alteration of soil pH, owing to species-specific traits, e.g., support of nitrogen fixation and Al accumulation. In a long-term, randomized complete block experiment in which climate, soil type, and previous land-use history were similar, we evaluated effects of individual native tropical tree species on water-stable macroaggregate size distributions in an Oxisol. We conducted this study at La Selva Biological Station in Costa Rica, in six vegetation types: 25-year-old plantations of four tree species grown in monodominant stands; an unplanted Control; and an adjacent mature forest. Tree species significantly influenced aggregate proportions in smaller size classes (0.25–1.0 mm), which were correlated with fine-root growth and litterfall. Tree species altered soil pH differentially. Across all vegetation types, the proportion of smaller macroaggregates declined significantly as soil pH increased (p ≤ 0.0184). This suggests that alteration of pH influences dispersivity, and thus macroaggregate dynamics, thereby playing a role in soil C, N, and P cycling.}, journal={Forests}, year={2018}, month={Apr} }
 @article{brave new world_2017, url={http://dx.doi.org/10.1007/s10533-017-0316-y}, DOI={10.1007/s10533-017-0316-y}, journal={Biogeochemistry}, year={2017}, month={Mar} }
 @article{hawkes_waring_rocca_kivlin_2017, title={Historical climate controls soil respiration responses to current soil moisture}, url={https://doi.org/10.1073/pnas.1620811114}, DOI={10.1073/pnas.1620811114}, abstractNote={Significance Ecosystems’ feedback to climate change remains a source of uncertainty in global models that project future climate conditions. That uncertainty rests largely on how much soil carbon will be lost as microbial respiration and how that loss varies across ecosystems. Although there has been a large emphasis on microbial temperature responses, how soil microorganisms respond to changes in moisture remains poorly understood. Here we show that historical rainfall controls soil respiration responses to current moisture. This finding was robust, with historical climate repeatedly limiting current respiration regardless of alterations to soil moisture, rainfall, or the arrival of new taxa. This study highlights the importance that legacies in microbial responses to climate change can have in future ecosystem responses.}, journal={Proceedings of the National Academy of Sciences}, author={Hawkes, Christine V. and Waring, Bonnie G. and Rocca, Jennifer D. and Kivlin, Stephanie N.}, year={2017}, month={Jun} }
 @article{microbial tools in agriculture require an ecological context: stress-dependent non-additive symbiont interactions_2017, url={http://dx.doi.org/10.2134/agronj2016.10.0568}, DOI={10.2134/agronj2016.10.0568}, abstractNote={Core Ideas Leaf fungal symbionts represent a potential new tool in agriculture. Effective fungal application requires an understanding of their interactions. Fungal interactions resulted in non‐additive plant growth and wilt responses. Fungal metabolites indicated qualitative additive, synergistic, or antagonistic plant responses. Fungal trait dissimilarity predicted the size of plant response deviations. Fungal symbionts are increasingly targeted as tools for crop management, but their use in the field requires an understanding of how fungi interact in a community context. Fungal interactions may result in additive effects on the host plant, which could be predicted simply based on individual fungal behavior. Alternatively, interactions among fungi may result in non‐additive synergistic or antagonistic effects on plant performance that are more challenging to predict. Here, we hypothesized that the effects of fungal interactions on the plant host could be predicted from their niche overlap. To test this idea, we used foliar fungal endophytes with a range of niche overlap based on trait dissimilarities to examine the effects of six fungal species pairs compared to the corresponding individual fungal species on switchgrass ( Panicum virgatum L.) in water‐stressed and well‐watered conditions. Mixtures of endophytes had either no effect or predictable, additive effects on plant tiller number, but effects on plant growth rate and wilting were largely non‐additive. Moisture level, fungal stress, and metabolic trait dissimilarity predicted 51 to 92% of the deviation of fungal effects from additive, with less similar fungi likely to have more synergistic effects on the plant host. Furthermore, we identified indicator metabolites for fungal interaction outcomes. However, the effects of endophyte interactions on the plant host were environment dependent making single community applications more challenging. Overall, future development of microbial tools for use in agriculture must consider their interactions to optimize application.}, journal={Agronomy Journal}, year={2017} }
 @article{regardless of n-substrate, multiple fungal root endophytes isolated from pastures outgrow and outcompete those isolated from undisturbed sites_2017, url={http://dx.doi.org/10.1016/j.pedobi.2017.05.006}, DOI={10.1016/j.pedobi.2017.05.006}, abstractNote={Edaphic properties such as soil nutrients structure belowground fungal communities and alter their intimate interactions with plants. Yet little work has compared the traits of fungal root endophytes and tested if specific soil nutrients determine their growth and competition. We hypothesized that fungi isolated from particular resource environments should grow and compete better when resources matched their “home” environment. We conducted experiments to compare growth rate and competitive ability of eight fungal root endophytes, cultured from either low nutrient undisturbed sites or from sites converted to high nutrient pastures, varying the nutrient environments to match the different sites. In isolation, biomass depended on nutrient limitation and fungal identity. Pasture endophytes all had high biomass in high nitrogen environments while endophytes from undisturbed sites showed greater variation among isolates. In competition, growth differences quantitatively depended on the fungus’s identity, its competitor’s identity and nutrients, yet pasture fungi out-competed “undisturbed” fungi in nearly every case. Rapid growth and competitive ability appears to be a trait of these fungal endophytes isolated from pastures and not solely a product of high nutrients, which may inhibit successful reintroduction of fungi from undisturbed sites.}, journal={Pedobiologia}, year={2017}, month={Jul} }
 @inbook{the predictive power of ecological niche modeling for global arbuscular mycorrhizal fungal biogeography_2017, url={http://dx.doi.org/10.1007/978-3-319-56363-3_7}, DOI={10.1007/978-3-319-56363-3_7}, abstractNote={The distributions of arbuscular mycorrhizal (AM) fungal communities are driven by climate, soil nutrients, and plant community composition. However, these distributions are estimated at the community level and AM fungal taxa will respond to selection pressure of global change at the species level. Thus, ecological niche models of individual AM fungal taxa may be an informative approach to predict AM fungal composition and function under future climates at the global scale. Here we present the first attempt to model AM fungal distributions with ecological niche models for the widespread AM fungal taxon Rhizophagus irregularis (formerly Glomus intraradices). We show that despite varying the definition of the operational taxonomic unit (OTU) for R. irregularis, the predicted distributions of this species complex are consistently affected by a positive association with soil moisture. The spatial extent of ecological niche models affected the predicted distribution of R. irregularis, with climatic drivers and resources affecting its distribution more strongly in the northern and southern hemispheres, respectively. Given that AM fungi are not dispersal limited and coexist at the landscape scale relevant for ecological niche model predictions, this widely distributed fungal clade provides a robust case study to apply hypothesis-driven distributional models to predict the biogeography of microorganisms.}, booktitle={Biogeography of Mycorrhizal Symbiosis}, year={2017} }
 @article{hawkes_connor_2017, title={Translating Phytobiomes from Theory to Practice: Ecological and Evolutionary Considerations}, volume={1}, url={https://doi.org/10.1094/PBIOMES-05-17-0019-RVW}, DOI={10.1094/PBIOMES-05-17-0019-RVW}, abstractNote={The tremendous potential of the plant microbiome to improve plant growth and production means that microbes are in the process of becoming an everyday tool in agronomic practices. However, historically field applications of microbes have had low success. We propose that development and optimization of microbiome treatments will benefit from the integration of ecological and evolutionary niche theory into plant microbiome studies. Thus, we review several niche-based processes that can aid in the development and implementation of microbiome treatments. Current predictive approaches include evolutionary history, habitat origin, ecological traits, resource trade, and gene signatures, none of which are mutually exclusive. A robust predictive framework must further account for observed plasticity and context dependence in microbial function. Development of microbiome treatments that will successfully establish in the field can also benefit from a better understanding of niche-based processes such as niche partitioning to limit competitive interactions and maximize persistence, priority effects to allow establishment before resident taxa, storage effects that take advantage of temporal variation in niche availability, and local adaptation to specific environments. Using endophytic fungi as examples, we illustrate current knowledge and gaps in these areas. Finally, we address existing limitations to the broad-scale development of successful microbiome tools.}, number={2}, journal={Phytobiomes Journal}, publisher={Scientific Societies}, author={Hawkes, Christine V. and Connor, Elise W.}, year={2017}, month={Jan}, pages={57–69} }
 @inbook{climate change, microbes, and soil carbon cycling_2016, url={http://dx.doi.org/10.21775/9781910190319.07}, DOI={10.21775/9781910190319.07}, booktitle={Climate Change and Microbial Ecology: Current Research and Future Trends}, year={2016} }
 @article{ectomycorrhizal fungi slow soil carbon cycling_2016, url={http://dx.doi.org/10.1111/ele.12631}, DOI={10.1111/ele.12631}, abstractNote={Respiration of soil organic carbon is one of the largest fluxes of CO2 on earth. Understanding the processes that regulate soil respiration is critical for predicting future climate. Recent work has suggested that soil carbon respiration may be reduced by competition for nitrogen between symbiotic ectomycorrhizal fungi that associate with plant roots and free-living microbial decomposers, which is consistent with increased soil carbon storage in ectomycorrhizal ecosystems globally. However, experimental tests of the mycorrhizal competition hypothesis are lacking. Here we show that ectomycorrhizal roots and hyphae decrease soil carbon respiration rates by up to 67% under field conditions in two separate field exclusion experiments, and this likely occurs via competition for soil nitrogen, an effect larger than 2 °C soil warming. These findings support mycorrhizal competition for nitrogen as an independent driver of soil carbon balance and demonstrate the need to understand microbial community interactions to predict ecosystem feedbacks to global climate.}, journal={Ecology Letters}, year={2016}, month={Aug} }
 @article{historical and current climate drive spatial and temporal patterns in fungal endophyte diversity_2016, url={http://dx.doi.org/10.1016/j.funeco.2015.12.005}, DOI={10.1016/j.funeco.2015.12.005}, abstractNote={Horizontally-transmitted foliar endophytic fungi can moderate plant tolerance to abiotic and biotic stress. Previous studies have found correlations between climate and endophyte beta diversity, but were unable to clearly separate drivers related to long-term climate, annual weather, and host plants. To address this, we characterized endophyte communities in the perennial C4 grass, Panicum hallii, across a precipitation gradient in central Texas over 3 years. A total of 65 unique leaf endophytes were isolated and identified based on ITS and LSU regions of rDNA. Mean annual rainfall and temperature were the primary drivers of endophyte richness and community composition, followed by annual weather conditions. In contrast, little explanatory value was provided by plant host traits, vegetation structure, or spatial factors. The importance of historical climate and annual weather in endophyte distributions suggests that species sort by environment and are likely to be affected by future climate change.}, journal={Fungal Ecology}, year={2016}, month={Apr} }
 @article{historical precipitation predictably alters the shape and magnitude of microbial functional response to soil moisture_2016, url={http://dx.doi.org/10.1111/gcb.13219}, DOI={10.1111/gcb.13219}, abstractNote={Abstract Soil moisture constrains the activity of decomposer soil microorganisms, and in turn the rate at which soil carbon returns to the atmosphere. While increases in soil moisture are generally associated with increased microbial activity, historical climate may constrain current microbial responses to moisture. However, it is not known if variation in the shape and magnitude of microbial functional responses to soil moisture can be predicted from historical climate at regional scales. To address this problem, we measured soil enzyme activity at 12 sites across a broad climate gradient spanning 442–887 mm mean annual precipitation. Measurements were made eight times over 21 months to maximize sampling during different moisture conditions. We then fit saturating functions of enzyme activity to soil moisture and extracted half saturation and maximum activity parameter values from model fits. We found that 50% of the variation in maximum activity parameters across sites could be predicted by 30‐year mean annual precipitation, an indicator of historical climate, and that the effect is independent of variation in temperature, soil texture, or soil carbon concentration. Based on this finding, we suggest that variation in the shape and magnitude of soil microbial response to soil moisture due to historical climate may be remarkably predictable at regional scales, and this approach may extend to other systems. If historical contingencies on microbial activities prove to be persistent in the face of environmental change, this approach also provides a framework for incorporating historical climate effects into biogeochemical models simulating future global change scenarios.}, journal={Global Change Biology}, year={2016}, month={May} }
 @article{intraspecific variation in precipitation responses of a widespread c4grass depends on site water limitation_2016, url={http://dx.doi.org/10.1093/jpe/rtw040}, DOI={10.1093/jpe/rtw040}, abstractNote={Variation in precipitation strongly influences plant growth, species distributions and genetic diversity. Intraspecific variation in phenotypic plasticity, the ability of a genotype to alter its growth, morphology or physiology in response to the environment, could influence species responses to changing precipitation and climate change. Despite this, the patterns and mechanisms of intraspecific variation in plasticity to variable precipitation, and the degree to which genotype responses to precipitation are influenced by variation in edaphic conditions, remain poorly understood. Thus, we determined whether genotypes of a widespread C4 grass (Panicum virgatum L., switchgrass) varied in aboveground productivity in response to changes in precipitation, and if site edaphic conditions modified genotype aboveground productivity responses to precipitation. We also determined if genotype productivity responses to precipitation are related to plasticity in underlying growth and phenological traits. Nine P. virgatum genotypes originating from an aridity gradient were grown under four treatments spanning the 10th to the 90th percentiles of annual precipitation at two sites in central Texas: one site with deep, fine-textured soils and another site with shallow, coarse-textured soils. We measured volumetric soil water content (VWC), aboveground net primary productivity (ANPP), tiller production (tiller number), average tiller mass, canopy height, leaf area index (LAI) and flowering time on all plants at both sites and examined genotype responses to changes in precipitation. Across precipitation treatments, VWC was 39% lower and more variable at the site with shallow, coarse-textured soils compared to the site with deep, fine-textured soils. ANPP averaged across genotypes and precipitation treatments was also 103% higher at the site with deep, fine-textured soils relative to the site with shallow, coarse-textured soils, indicating substantial differences in site water limitation. Where site water limitation was higher, ANPP of most genotypes increased with increasing precipitation. Where site water limitation was less, genotypes expressed variable plasticity in response to precipitation, from no change to almost a 5-fold increase in ANPP with increasing precipitation. Genotype ANPP increased with greater tiller mass, LAI and later flowering time at both sites, but not with tiller number at either site. Genotype ANPP plasticity increased with genotype tiller mass and LAI plasticity at the site with deep, fine-textured soils, and only with genotype tiller mass plasticity at the site with shallow, coarse-textured soils. Thus, variation in genotype ANPP plasticity was explained primarily by variation in tiller and leaf growth. Genotype ANPP plasticity was not associated with temperature or aridity at the genotype’s origin. Edaphic factors such as soil depth and texture may alter genotype ANPP responses to precipitation, and the underlying growth traits contributing to the ANPP response. Thus, edaphic factors may contribute to spatial variation in genotype performance and success under altered precipitation.}, journal={Journal of Plant Ecology}, year={2016}, month={Apr} }
 @article{plant and root endophyte assembly history: interactive effects on native and exotic plants_2016, url={http://dx.doi.org/10.1890/15-0635.1}, DOI={10.1890/15-0635.1}, abstractNote={Abstract Differences in the arrival timing of plants and soil biota may result in different plant communities through priority effects, potentially affecting the success of native vs. exotic plants, but experimental evidence is largely lacking. We conducted a greenhouse experiment to investigate whether the assembly history of plants and fungal root endophytes could interact to influence plant emergence and biomass. We introduced a grass species and eight fungal species from one of three land‐use types (undisturbed, disturbed, or pasture sites in a Florida scrubland) in factorial combinations. We then introduced all plants and fungi from the other land‐use types 2 weeks later. Plant emergence was monitored for 6 months, and final plant biomass and fungal species composition assessed. The emergence and growth of the exotic Melinis repens and the native Schizacharyium niveum were affected negatively when introduced early with their “home” fungi, but early introduction of a different plant species or fungi from a different site type eliminated these negative effects, providing evidence for interactive priority effects. Interactive effects of plant and fungal arrival history may be an overlooked determinant of plant community structure and may provide an effective management tool to inhibit biological invasion and aid ecosystem restoration.}, journal={Ecology}, year={2016}, month={Feb} }
 @article{promises and challenges of eco-physiological genomics in the field: tests of drought responses in switchgrass_2016, url={http://dx.doi.org/10.1104/pp.16.00545}, DOI={10.1104/pp.16.00545}, abstractNote={Identifying the physiological and genetic basis of stress tolerance in plants has proven to be critical to understanding adaptation in both agricultural and natural systems. However, many discoveries were initially made in the controlled conditions of greenhouses or laboratories, not in the field. To test the comparability of drought responses across field and greenhouse environments, we undertook three independent experiments using the switchgrass reference genotype Alamo AP13. We analyzed physiological and gene expression variation across four locations, two sampling times, and three years. Relatively similar physiological responses and expression coefficients of variation across experiments masked highly dissimilar gene expression responses to drought. Critically, a drought experiment utilizing small pots in the greenhouse elicited nearly identical physiological changes as an experiment conducted in the field, but an order of magnitude more differentially expressed genes. However, we were able to define a suite of several hundred genes that were differentially expressed across all experiments. This list was strongly enriched in photosynthesis, water status, and reactive oxygen species responsive genes. The strong across-experiment correlations between physiological plasticity—but not differential gene expression—highlight the complex and diverse genetic mechanisms that can produce phenotypically similar responses to various soil water deficits.}, journal={Plant Physiology}, year={2016}, month={May} }
 @article{simulating diverse native c4 perennial grasses with varying rainfall_2016, url={http://dx.doi.org/10.1016/j.jaridenv.2016.07.004}, DOI={10.1016/j.jaridenv.2016.07.004}, abstractNote={Rainfall is recognized as a major factor affecting the rate of plant growth development. The impact of changes in amount and variability of rainfall on growth and production of different forage grasses needs to be quantified to determine how climate change can impact rangelands. Comparative studies to evaluate the growth of several perennial forage species at different rainfall rates will provide useful information by identifying forage management strategies under various rainfall scenarios. In this study, the combination of rainfall changes and soil types on the plant growth of 10 perennial forage species was investigated with both the experimental methods, using rainout shelters, and with the numerical methods using the plant growth simulation model, ALMANAC. Overall, most species significantly increased basal diameter and height as rainfall increased. Like measured volume, simulated yields for all species generally increased as rainfall increased. But, large volume and yield increases were only observed between 350 and 850 mm/yr. Simulating all species growing together competing agrees relatively well with observed plant volumes at low rainfall treatment, while simulating all species growing separately was slightly biased towards overestimation on low rainfall effect. Both simulations agree relatively well with observed plant volume at high rainfall treatment.}, journal={Journal of Arid Environments}, year={2016}, month={Nov} }
 @article{temporal and spatial variation of soil bacteria richness, composition, and function in a neotropical rainforest_2016, url={http://dx.doi.org/10.1371/journal.pone.0159131}, DOI={10.1371/journal.pone.0159131}, abstractNote={The high diversity of tree species has traditionally been considered an important controller of belowground processes in tropical rainforests. However, soil water availability and resources are also primary regulators of soil bacteria in many ecosystems. Separating the effects of these biotic and abiotic factors in the tropics is challenging because of their high spatial and temporal heterogeneity. To determine the drivers of tropical soil bacteria, we examined tree species effects using experimental tree monocultures and secondary forests at La Selva Biological Station in Costa Rica. A randomized block design captured spatial variation and we sampled at four dates across two years to assess temporal variation. We measured bacteria richness, phylogenetic diversity, community composition, biomass, and functional potential. All bacteria parameters varied significantly across dates. In addition, bacteria richness and phylogenetic diversity were affected by the interaction of vegetation type and date, whereas bacteria community composition was affected by the interaction of vegetation type and block. Shifts in bacteria community richness and composition were unrelated to shifts in enzyme function, suggesting physiological overlap among taxa. Based on the observed temporal and spatial heterogeneity, our understanding of tropical soil bacteria will benefit from additional work to determine the optimal temporal and spatial scales for sampling. Understanding spatial and temporal variation will facilitate prediction of how tropical soil microbes will respond to future environmental change.}, journal={PLOS ONE}, year={2016}, month={Jul} }
 @article{tree species, spatial heterogeneity, and seasonality drive soil fungal abundance, richness, and composition in neotropical rainforests_2016, url={http://dx.doi.org/10.1111/1462-2920.13342}, DOI={10.1111/1462-2920.13342}, abstractNote={Summary Tropical ecosystems remain poorly understood and this is particularly true for belowground soil fungi. Soil fungi may respond to plant identity when, for example, plants differentially allocate resources belowground. However, spatial and temporal heterogeneity in factors such as plant inputs, moisture, or nutrients can also affect fungal communities and obscure our ability to detect plant effects in single time point studies or within diverse forests. To address this, we sampled replicated monocultures of four tree species and secondary forest controls sampled in the drier and wetter seasons over 2 years. Fungal community composition was primarily related to vegetation type and spatial heterogeneity in the effects of vegetation type, with increasing divergence partly reflecting greater differences in soil pH and soil moisture. Across wetter versus drier dates, fungi were 7% less diverse, but up to four‐fold more abundant. The combined effects of tree species and seasonality suggest that predicted losses of tropical tree diversity and intensification of drought have the potential to cascade belowground to affect both diversity and abundance of tropical soil fungi.}, journal={Environmental Microbiology}, year={2016}, month={Dec} }
 @article{microbial-mediated redistribution of ecosystem nitrogen cycling can delay progressive nitrogen limitation_2015, url={http://dx.doi.org/10.1007/s10533-015-0160-x}, DOI={10.1007/s10533-015-0160-x}, journal={Biogeochemistry}, year={2015}, month={Nov} }
 @article{resilience vs. historical contingency in microbial responses to environmental change_2015, url={http://dx.doi.org/10.1111/ele.12451}, DOI={10.1111/ele.12451}, abstractNote={How soil processes such as carbon cycling will respond to future climate change depends on the responses of complex microbial communities, but most ecosystem models assume that microbial functional responses are resilient and can be predicted from simple parameters such as biomass and temperature. Here, we consider how historical contingencies might alter those responses because function depends on prior conditions or biota. Functional resilience can be driven by physiological, community or adaptive shifts; historical contingencies can result from the influence of historical environments or a combination of priority effects and biotic resistance. By modelling microbial population responses to environmental change, we demonstrate that historical environments can constrain soil function with the degree of constraint depending on the magnitude of change in the context of the prior environment. For example microbial assemblages from more constant environments were more sensitive to change leading to poorer functional acclimatisation compared to microbial assemblages from more fluctuating environments. Such historical contingencies can lead to deviations from expected functional responses to climate change as well as local variability in those responses. Our results form a set of interrelated hypotheses regarding soil microbial responses to climate change that warrant future empirical attention.}, journal={Ecology Letters}, year={2015}, month={Jul} }
 @article{waring_hawkes_2015, title={Short-Term Precipitation Exclusion Alters Microbial Responses to Soil Moisture in a Wet Tropical Forest}, volume={69}, url={http://dx.doi.org/10.1007/s00248-014-0436-z}, DOI={10.1007/s00248-014-0436-z}, number={4}, journal={Microbial Ecology}, publisher={Springer Science \mathplus Business Media}, author={Waring, Bonnie G. and Hawkes, Christine V.}, year={2015}, month={May}, pages={843–854} }
 @article{glinka_hawkes_2014, title={Environmental Controls on Fungal Community Composition and Abundance Over 3 Years in Native and Degraded Shrublands}, volume={68}, DOI={10.1007/s00248-014-0443-0}, number={4}, journal={Microb Ecol}, publisher={Springer Science \mathplus Business Media}, author={Glinka, Clare and Hawkes, Christine V.}, year={2014}, month={Jun}, pages={807–817} }
 @article{standish_hobbs_mayfield_bestelmeyer_suding_battaglia_eviner_hawkes_temperton_cramer_et al._2014, title={Resilience in ecology: Abstraction, distraction, or where the action is?}, volume={177}, DOI={10.1016/j.biocon.2014.06.008}, abstractNote={Increasingly, the success of management interventions aimed at biodiversity conservation are viewed as being dependent on the ‘resilience’ of the system. Although the term ‘resilience’ is increasingly used by policy makers and environmental managers, the concept of ‘resilience’ remains vague, varied and difficult to quantify. Here we clarify what this concept means from an ecological perspective, and how it can be measured and applied to ecosystem management. We argue that thresholds of disturbance are central to measuring resilience. Thresholds are important because they offer a means to quantify how much disturbance an ecosystem can absorb before switching to another state, and so indicate whether intervention might be necessary to promote the recovery of the pre-disturbance state. We distinguish between helpful resilience, where resilience helps recovery, and unhelpful resilience where it does not, signalling the presence of a threshold and the need for intervention. Data to determine thresholds are not always available and so we consider the potential for indices of functional diversity to act as proxy measures of resilience. We also consider the contributions of connectivity and scale to resilience and how to incorporate these factors into management. We argue that linking thresholds to functional diversity indices may improve our ability to predict the resilience of ecosystems to future, potentially novel, disturbances according to their spatial and temporal scales of influence. Throughout, we provide guidance for the application of the resilience concept to ecosystem management. In doing so, we confirm its usefulness for improving biodiversity conservation in our rapidly changing world.}, journal={Biological Conservation}, publisher={Elsevier BV}, author={Standish, Rachel J. and Hobbs, Richard J. and Mayfield, Margaret M. and Bestelmeyer, Brandon T. and Suding, Katherine N. and Battaglia, Loretta L. and Eviner, Valerie and Hawkes, Christine V. and Temperton, Vicky M. and Cramer, Viki A. and et al.}, year={2014}, month={Sep}, pages={43–51} }
 @article{kardol_deyn_laliberté_mariotte_hawkes_2013, title={Biotic plant-soil feedbacks across temporal scales}, volume={101}, DOI={10.1111/1365-2745.12046}, abstractNote={Summary Plant effects on soil biota can result in feedbacks affecting plant performance, with consequences for plant community and ecosystem dynamics on short and long time‐scales. In addition, the strength and direction of plant–soil feedbacks depend on temporal shifts in abiotic environmental conditions. We synthesize current knowledge on temporal aspects of plant–soil feedbacks and present new ideas to better understand and predict the effects of plant–soil feedbacks on community and ecosystem properties across temporal scales. Explaining short‐term temporal feedback dynamics requires us to better understand mechanistic linkages between plants, soil organisms and locally available resources. On the other hand, we need to refine our understanding of the context‐dependency of plant–soil feedbacks, as the strength and direction of feedback interactions are influenced by ‘external’ temporal ecosystem dynamics, such as variation in soil resource availability after disturbance or during succession. Synthesis . Based on our synthesis of temporal aspects of plant–soil feedbacks, we suggest three main avenues for future research: (i) how plant–soil feedbacks changes with ontogeny, (ii) how plant and soil organism traits drive temporal variation in plant–soil feedbacks and (iii) how environmental changes across temporal scales alter the strength and direction of plant–soil feedbacks.}, number={2}, journal={J Ecol}, publisher={Wiley-Blackwell}, author={Kardol, Paul and Deyn, Gerlinde B. De and Laliberté, Etienne and Mariotte, Pierre and Hawkes, Christine V.}, editor={Putten, WimEditor}, year={2013}, month={Feb}, pages={309–315} }
 @article{climate affects symbiotic fungal endophyte diversity and performance_2013, url={http://dx.doi.org/10.3732/ajb.1200568}, DOI={10.3732/ajb.1200568}, abstractNote={• Premise of the study: Fungal endophytes are symbionts that inhabit aboveground tissues of most terrestrial plants and can affect plant physiology and growth under stressed conditions. In a future faced with substantial climate change, endophytes have the potential to play an important role in plant stress resistance. Understanding both the distributions of endophytes and their functioning in symbiosis with plants are key aspects of predicting their role in an altered climate. • Methods: Here we characterized endophytes in grasses across a steep precipitation gradient to examine the relative importance of environmental and spatial factors in structuring endophyte communities. We also tested how 20 endophytes isolated from drier and wetter regions performed in symbiosis with grass seedlings under high and low soil moisture in the greenhouse. • Key results: Environmental factors related to historical and current precipitation were the most important predictors of endophyte communities in the field. On average, endophytic fungi from western sites also reduced plant water loss in the greenhouse compared to fungi from eastern sites. However, there was substantial variability in how individual endophytic taxa affected plant traits under high and low water availability, with up to two orders of magnitude difference in the plasticity of plant traits conferred by the different fungal taxa. • Conclusions: While species sorting appears to largely explain local endophyte community composition, their function in symbiosis is not predictable from local environmental conditions. The development of a predictive framework for endophyte function will require further study of individual fungal taxa and genotypes across environmental gradients.}, journal={American Journal of Botany}, year={2013}, month={Jul} }
 @article{waring_averill_hawkes_2013, title={Differences in fungal and bacterial physiology alter soil carbon and nitrogen cycling: insights from meta-analysis and theoretical models}, volume={16}, DOI={10.1111/ele.12125}, abstractNote={Since fungi and bacteria are the dominant decomposers in soil, their distinct physiologies are likely to differentially influence rates of ecosystem carbon (C) and nitrogen (N) cycling. We used meta-analysis and an enzyme-driven biogeochemical model to explore the drivers and biogeochemical consequences of changes in the fungal-to-bacterial ratio (F : B). In our meta-analysis data set, F : B increased with soil C : N ratio (R2 = 0.224, P < 0.001), a relationship predicted by our model. We found that differences in biomass turnover rates influenced F : B under conditions of C limitation, while differences in biomass stoichiometry set the upper bounds on F : B once a nutrient limitation threshold was reached. Ecological interactions between the two groups shifted along a gradient of resource stoichiometry. At intermediate substrate C : N, fungal N mineralisation fuelled bacterial growth, increasing total microbial biomass and decreasing net N mineralisation. Therefore, we conclude that differences in bacterial and fungal physiology may have large consequences for ecosystem-scale C and N cycling.}, number={7}, journal={Ecol Lett}, publisher={Wiley-Blackwell}, author={Waring, Bonnie G. and Averill, Colin and Hawkes, Christine V.}, editor={Holyoak, MarcelEditor}, year={2013}, month={May}, pages={887–894} }
 @article{aspinwall_lowry_taylor_juenger_hawkes_johnson_kiniry_fay_2013, title={Genotypic variation in traits linked to climate and aboveground productivity in a widespread C 4 grass: evidence for a functional trait syndrome}, volume={199}, DOI={10.1111/nph.12341}, abstractNote={Summary Examining intraspecific variation in growth and function in relation to climate may provide insight into physiological evolution and adaptation, and is important for predicting species responses to climate change. Under common garden conditions, we grew nine genotypes of the C 4 species Panicum virgatum originating from different temperature and precipitation environments. We hypothesized that genotype productivity, morphology and physiological traits would be correlated with climate of origin, and a suite of adaptive traits would show high broad‐sense heritability ( H 2 ). Genotype productivity and flowering time increased and decreased, respectively, with home‐climate temperature, and home‐climate temperature was correlated with genotypic differences in a syndrome of morphological and physiological traits. Genotype leaf and tiller size, leaf lamina thickness, leaf mass per area ( LMA ) and C : N ratios increased with home‐climate temperature, whereas leaf nitrogen per unit mass ( N m ) and chlorophyll (Chl) decreased with home‐climate temperature. Trait variation was largely explained by genotypic differences ( H 2 = 0.33–0.85). Our results provide new insight into the role of climate in driving functional trait coordination, local adaptation and genetic divergence within species. These results emphasize the importance of considering intraspecific variation in future climate change scenarios.}, number={4}, journal={New Phytol}, publisher={Wiley-Blackwell}, author={Aspinwall, Michael J. and Lowry, David B. and Taylor, Samuel H. and Juenger, Thomas E. and Hawkes, Christine V. and Johnson, Mari-Vaughn V. and Kiniry, James R. and Fay, Philip A.}, year={2013}, month={May}, pages={966–980} }
 @article{perennial biomass grasses and the mason–dixon line: comparative productivity across latitudes in the southern great plains_2013, url={http://dx.doi.org/10.1007/s12155-012-9254-7}, DOI={10.1007/s12155-012-9254-7}, abstractNote={Understanding latitudinal adaptation of switchgrass (Panicum virgatum L.) and Miscanthus (Miscanthus × giganteus J. M. Greef & Deuter ex Hodk. & Renvoize) to the southern Great Plains is key to maximizing productivity by matching each grass variety to its optimal production environment. The objectives of this study were: (1) to quantify latitudinal variation in production of representative upland switchgrass ecotypes (Blackwell, Cave-in-Rock, and Shawnee), lowland switchgrass ecotypes (Alamo, Kanlow), and Miscanthus in the southern half of the US Great Plains and (2) to investigate the environmental factors affecting yield variation. Leaf area and yield were measured on plots at 10 locations in Missouri, Arkansas, Oklahoma, and Texas. More cold winter days led to decreased subsequent Alamo switchgrass yields and increased subsequent upland switchgrass yields. More hot-growing season days led to decreased Kanlow and Miscanthus yields. Increased drought intensity also contributed to decreased Miscanthus yields. Alamo switchgrass had the greatest radiation use efficiency (RUE) with a mean of 4.3 g per megajoule intercepted PAR and water use efficiency (WUE) with a mean of 4.5 mg of dry weight per gram of water transpired. The representative RUE values for other varieties ranged from 67 to 80 % of Alamo’s RUE value and 67 to 87 % of Alamo’s WUE. These results will provide valuable inputs to process-based models to realistically simulate these important perennial grasses in this region and to assess the environmental impacts of production on water use and nutrient demands. In addition, it will also be useful for landowners and companies choosing the most productive perennial grasses for biofuel production.}, journal={BioEnergy Research}, year={2013}, month={Mar} }
 @article{kivlin_waring_averill_hawkes_2013, title={Tradeoffs in microbial carbon allocation may mediate soil carbon storage in future climates}, volume={4}, DOI={10.3389/fmicb.2013.00261}, abstractNote={GENERAL COMMENTARY article Front. Microbiol., 04 September 2013Sec. Terrestrial Microbiology Volume 4 - 2013 | https://doi.org/10.3389/fmicb.2013.00261}, journal={Front. Microbiol.}, publisher={Frontiers Media SA}, author={Kivlin, Stephanie N. and Waring, Bonnie G. and Averill, Colin and Hawkes, Christine V.}, year={2013} }
 @article{hamman_hawkes_2012, title={Biogeochemical and Microbial Legacies of Non-Native Grasses Can Affect Restoration Success}, volume={21}, DOI={10.1111/j.1526-100x.2011.00856.x}, abstractNote={The restoration of disturbed ecosystems is challenging and often unsuccessful, particularly when non‐native plants are abundant. Ecosystem restoration may be hindered by the effects of non‐native plants on soil biogeochemical characteristics and microbial communities that persist even after plants are removed. To examine the importance of soil legacy effects, we used experimental restorations of Florida shrubland habitat that had been degraded by the introduction of non‐native grasses coupled with either mechanical disturbance or pasture conversion. We removed non‐native grasses and inoculated soils with native microbial communities at each degraded site, then examined how habitat structure, soil nitrogen, soil microbial abundances, and native seed germination responded over two years compared to undisturbed native sites. Grass removal treatments effectively restored some aspects of native habitat structure, including decreased exotic grass cover, increased bare ground, and reduced litter cover. Soil fungal abundance was also somewhat restored by grass removals, but soil algal abundance was unaffected. In addition, grass removal and microbial inoculation improved seed germination rates in degraded sites, but these remained quite low compared to native sites. High soil nitrogen persisted throughout the experiment regardless of treatment. Many treatment effects were site‐specific, however, with legacies in the more degraded vegetation type tending to be more difficult to overcome. These results support the need for context‐dependent restoration approaches and suggest that the degree of soil legacy effects may be a good indicator of restoration potential.}, number={1}, journal={Restoration Ecology}, publisher={Wiley-Blackwell}, author={Hamman, Sarah T. and Hawkes, Christine V.}, year={2012}, month={Apr}, pages={58–66} }
 @article{hawkes_kivlin_du_eviner_2012, title={The temporal development and additivity of plant-soil feedback in perennial grasses}, volume={369}, DOI={10.1007/s11104-012-1557-0}, number={1-2}, journal={Plant Soil}, publisher={Springer Science \mathplus Business Media}, author={Hawkes, Christine V. and Kivlin, Stephanie N. and Du, Jennifer and Eviner, Valerie T.}, year={2012}, pages={141–150} }
 @article{treseder_kivlin_hawkes_2011, title={Evolutionary trade-offs among decomposers determine responses to nitrogen enrichment}, volume={14}, DOI={10.1111/j.1461-0248.2011.01650.x}, abstractNote={Evolutionary trade-offs among ecological traits are one mechanism that could determine the responses of functional groups of decomposers to global changes such as nitrogen (N) enrichment. We hypothesised that bacteria targeting recalcitrant carbon compounds require relatively high levels of N availability to support the construction costs of requisite extracellular and transport enzymes. Indeed, we found that taxa that used more recalcitrant (i.e. larger and cyclic) carbon compounds were more prevalent in ocean waters with higher nitrate concentrations. Compared to recalcitrant carbon users, labile carbon users targeted more organic N compounds, were found in relatively nitrate-poor waters, and were more common in higher latitude soils, which is consistent with the paradigm that N-limitation is stronger at higher latitudes. Altogether, evolutionary trade-offs may limit recalcitrant carbon users to habitats with higher N availability.}, number={9}, journal={Ecology Letters}, publisher={Wiley-Blackwell}, author={Treseder, Kathleen K. and Kivlin, Stephanie N. and Hawkes, Christine V.}, year={2011}, month={Jul}, pages={933–938} }
 @article{kivlin_hawkes_treseder_2011, title={Global diversity and distribution of arbuscular mycorrhizal fungi}, volume={43}, DOI={10.1016/j.soilbio.2011.07.012}, abstractNote={Arbuscular mycorrhizal (AM) fungi form associations with most land plants and can control carbon, nitrogen, and phosphorus cycling between above- and belowground components of ecosystems. Current estimates of AM fungal distributions are mainly inferred from the individual distributions of plant biomes, and climatic factors. However, dispersal limitation, local environmental conditions,and interactions among AM fungal taxa may also determine local diversity and global distributions. We assessed the relative importance of these potential controls by collecting 14,961 DNA sequences from 111 published studies and testing for relationships between AM fungal community composition and geography, environment, and plant biomes. Our results indicated that the global species richness of AM fungi was up to six times higher than previously estimated, largely owing to high beta diversity among sampling sites. Geographic distance, soil temperature and moisture, and plant community type were each significantly related to AM fungal community structure, but explained only a small amount of the observed variance. AM fungal species also tended to be phylogenetically clustered within sites, further suggesting that habitat filtering or dispersal limitation is a driver of AM fungal community assembly. Therefore, predicted shifts in climate and plant species distributions under global change may alter AM fungal communities.}, number={11}, journal={Soil Biology and Biochemistry}, publisher={Elsevier BV}, author={Kivlin, Stephanie N. and Hawkes, Christine V. and Treseder, Kathleen K.}, year={2011}, month={Nov}, pages={2294–2303} }
 @article{kivlin_hawkes_2010, title={Differentiating between effects of invasion and diversity: impacts of aboveground plant communities on belowground fungal communities}, volume={189}, DOI={10.1111/j.1469-8137.2010.03494.x}, abstractNote={• Exotic plant species can affect soil microbial communities with the potential for community and ecosystem feedbacks. Yet, separating the effects of exotics from confounded changes in plant community diversity still remains a challenge. • We focused on how plant diversity and native or exotic life history affected root fungi because of their significant roles in community and ecosystem processes. Specifically, we examined how fungi colonizing plant roots were affected by plant richness (one, two or four species) replicated across a range of plant community mixtures (natives, exotics, native–exotic mixtures). • Fungal biomass inside roots was affected independently by plant richness and mixture, while root fungal community composition was affected only by plant richness. Extraradical networks also increased in size with plant richness. By contrast, plant biomass was a function of plant mixture, with natives consistently smaller than exotics and native–exotic mixtures intermediate. • Plant invasions may have an impact on the belowground community primarily through their effects on diversity, at least in the short-term. Disentangling the effects of diversity and invasion on belowground microbial communities can help us to understand both the controllers of belowground resilience and mechanisms of successful colonization and spread of exotic plants.}, number={2}, journal={New Phytologist}, publisher={Wiley-Blackwell}, author={Kivlin, Stephanie N. and Hawkes, Christine V.}, year={2010}, month={Oct}, pages={526–535} }
 @article{eviner_hoskinson_hawkes_2010, title={Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands}, volume={32}, DOI={10.2111/rangelands-d-09-00005.1}, abstractNote={Ecosystem Impacts of Exotic Plants Can Feed Back to Increase Invasion in Western US Rangelands DOI:10.2458/azu_rangelands_v32i1_Hawkes}, number={1}, journal={Rangelands}, publisher={Elsevier BV}, author={Eviner, Valerie T. and Hoskinson, Sarah A. and Hawkes, Christine V.}, year={2010}, month={Feb}, pages={21–31} }
 @article{hawkes_kivlin_rocca_huguet_thomsen_suttle_2010, title={Fungal community responses to precipitation}, volume={17}, DOI={10.1111/j.1365-2486.2010.02327.x}, abstractNote={Understanding how fungal communities are affected by precipitation is an essential aspect of predicting soil functional responses to future climate change and the consequences of those responses for the soil carbon cycle. We tracked fungal abundance, fungal community composition, and soil carbon across 4 years in long-term field manipulations of rainfall in northern California. Fungi responded directly to rainfall levels, with more abundant, diverse, and consistent communities predominating under drought conditions, and less abundant, less diverse, and more variable communities emerging during wetter periods and in rain-addition treatments. Soil carbon storage itself did not vary with rainfall amendments, but increased decomposition rates foreshadow longer-term losses of soil carbon under conditions of extended seasonal rainfall. The repeated recovery of fungal diversity and abundance during periodic drought events suggests that species with a wide range of environmental tolerances coexist in this community, consistent with a storage effect in soil fungi. Increased diversity during dry periods further suggests that drought stress moderates competition among fungal taxa. Based on the responses observed here, we suggest that there may be a relationship between the timescale at which soil microbial communities experience natural environmental fluctuations and their ability to respond to future environmental change.}, number={4}, journal={Global Change Biology}, publisher={Wiley-Blackwell}, author={HAWKES, CHRISTINE V. and KIVLIN, STEPHANIE N. and ROCCA, JENNIFER D. and HUGUET, VALERIE and THOMSEN, MEREDITH A. and SUTTLE, KENWYN BLAKE}, year={2010}, month={Oct}, pages={1637–1645} }
 @article{hausmann_hawkes_2010, title={Order of plant host establishment alters the composition of arbuscular mycorrhizal communities}, volume={91}, DOI={10.1890/09-0924.1}, abstractNote={The causes of local diversity and composition remain a central question in community ecology. Numerous studies have attempted to understand community assembly, both within and across trophic levels. However, little is known about how community assembly aboveground influences soil microbial communities belowground. We hypothesized that plant establishment order can affect the community of arbuscular mycorrhizal fungi (AMF) in roots, with the strength of this effect dependent on both host plant identity and neighboring plant identity. Such priority effects of plants on AMF may act through host-specific filters of the initial species pool that limit the available pool for plants that established second. In a greenhouse experiment with four plant hosts, we found that the strength of the priority effect on AMF communities reflected both host plant characteristics and interactions between host and neighbor plant species, consistent with differential host specificity among plants. These patterns were independent of plant biomass and root colonization. Functional studies of AMF associated with a wide array of host plants will be required to further understand this potential driver of community dynamics.}, number={8}, journal={Ecology}, publisher={Ecological Society of America}, author={Hausmann, Natasha Teutsch and Hawkes, Christine V.}, year={2010}, month={Aug}, pages={2333–2343} }
 @article{hawkes_douglas_fitter_2009, title={Origin, local experience, and the impact of biotic interactions on native and introduced Senecio species}, volume={12}, DOI={10.1007/s10530-009-9435-2}, number={1}, journal={Biol Invasions}, publisher={Springer Science \mathplus Business Media}, author={Hawkes, Christine V. and Douglas, Angela E. and Fitter, Alastair H.}, year={2009}, month={Feb}, pages={113–124} }
 @article{hausmann_hawkes_2009, title={Plant neighborhood control of arbuscular mycorrhizal community composition}, volume={183}, DOI={10.1111/j.1469-8137.2009.02882.x}, abstractNote={• Arbuscular mycorrhizal fungi (AMF) are important root symbionts that can provide benefits to plant hosts, yet we understand little about how neighboring hosts in a plant community contribute to the composition of the AMF community. We hypothesized that the composition of the plant neighborhood, including the identities of both host and neighbor, would alter AMF community composition. • We tested this in a glasshouse experiment in which a native perennial grass (Nassella pulchra) and three annual grasses (Avena barbata, Bromus hordeaceaous and Vulpia microstachys) were grown in two neighborhoods: conspecific monocultures and heterospecific perennial–annual mixtures. To identify AMF taxa colonizing plant roots, we used a combination of terminal restriction fragment length polymorphism and cloning. • Both host and neighbor were important in structuring AMF communities. Unique AMF communities were associated with each plant host in monoculture. In heterospecific neighborhoods, the annual neighbors V. microstachys, A. barbata, and B. hordeaceus influenced N. pulchra AMF in different ways (synergistic, controlling, or neutral) and the reciprocal effect was not always symmetric. • Our findings support a community approach to AMF studies, which can be used to increase our understanding of processes such as invasion and succession.}, number={4}, journal={New Phytologist}, publisher={Wiley-Blackwell}, author={Hausmann, Natasha Teutsch and Hawkes, Christine V.}, year={2009}, month={Sep}, pages={1188–1200} }
 @article{fox_kareiva_silliman_hitt_lytle_halpern_hawkes_lawler_neel_olden_et al._2009, title={Why do we fly? Ecologists' sins of emission}, volume={7}, DOI={10.1890/09.wb.019}, abstractNote={Please note: The publisher is not responsible for the content or functionality of any supporting information supplied by the authors. Any queries (other than missing content) should be directed to the corresponding author for the article.}, number={6}, journal={Frontiers in Ecology and the Environment}, publisher={Ecological Society of America}, author={Fox, Helen E and Kareiva, Peter and Silliman, Brian and Hitt, Jessica and Lytle, David A and Halpern, Benjamin S and Hawkes, Christine V and Lawler, Joshua and Neel, Maile and Olden, Julian D and et al.}, year={2009}, month={Aug}, pages={294–296} }
 @article{eviner_hawkes_2008, title={Embracing Variability in the Application of Plant-Soil Interactions to the Restoration of Communities and Ecosystems}, volume={16}, DOI={10.1111/j.1526-100x.2008.00482.x}, abstractNote={Plant–soil interactions are the foundation of effective and sustained restoration of terrestrial communities and ecosystems. Recent advances in ecological science have greatly contributed to our understanding of the effects of soil conditions on plant community dynamics and our understanding of plant composition impacts on almost every aspect of soil structure and function. Although these theories provide important guidelines for the practice of restoration, they often fall short of providing the level of information required to make effective site-specific management decisions. This is largely because of ecology’s search for simple unifying theories and the resulting tendency to generalize from studies at one or only a few sites. An average effect or broad-scale simple relationship tends to provide a “one-size-fits-all” (or none) prescription for managers. Plant–soil interactions can vary greatly depending on their context (e.g., environmental conditions, management practices, time, neighboring community, interaction with other organisms). The ability to predict these context-dependent interactions between plants and soils can be developed by building upon existing general frameworks for understanding plant–soil interactions. Collaborations between researchers and managers can develop conceptual tools that allow us to understand and manage the variability and complexity of plant–soil interactions, simultaneously advancing theory and applicability.}, number={4}, journal={Restoration Ecology}, publisher={Wiley-Blackwell}, author={Eviner, Valerie T. and Hawkes, Christine V.}, year={2008}, pages={713–729} }
 @article{preserving accuracy in genbank_2008, url={http://dx.doi.org/10.1126/science.319.5870.1616a}, DOI={10.1126/science.319.5870.1616a}, abstractNote={GenBank, the public repository for nucleotide and protein sequences, is a critical resource for molecular biology, evolutionary biology, and ecology. While some attention has been drawn to sequence errors ([1][1]), common annotation errors also reduce the value of this database. In fact, for}, journal={Science}, year={2008}, month={Mar} }
 @article{hawkes_hartley_ineson_fitter_2008, title={Soil temperature affects carbon allocation within arbuscular mycorrhizal networks and carbon transport from plant to fungus}, volume={14}, DOI={10.1111/j.1365-2486.2007.01535.x}, abstractNote={How soil carbon balance will be affected by plant–mycorrhizal interactions under future climate scenarios remains a significant unknown in our ability to forecast ecosystem carbon storage and fluxes. We examined the effects of soil temperature (14, 20, 26 °C) on the structure and extent of a multispecies community of arbuscular mycorrhizal (AM) fungi associated with Plantago lanceolata. To isolate fungi from roots, we used a mesh-divided pot system with separate hyphal compartments near and away from the plant. A 13C pulse label was then used to trace the flow of recently fixed photosynthate from plants into belowground pools and respiration. Temperature significantly altered the structure and allocation of the AM hyphal network, with a switch from more vesicles (storage) in cooled soils to more extensive extraradical hyphal networks (growth) in warmed soils. As soil temperature increased, we also observed an increase in the speed at which plant photosynthate was transferred to and respired by roots and AM fungi coupled with an increase in the amount of carbon respired per unit hyphal length. These differences were largely independent of plant size and rates of photosynthesis. In a warmer world, we would therefore expect more carbon losses to the atmosphere from AM fungal respiration, which are unlikely to be balanced by increased growth of AM fungal hyphae.}, number={5}, journal={Global Change Biol}, publisher={Wiley-Blackwell}, author={HAWKES, CHRISTINE V. and HARTLEY, IAIN P. and INESON, PHIL and FITTER, ALASTAIR H.}, year={2008}, month={May}, pages={1181–1190} }
 @article{hawkes_2007, title={Are Invaders Moving Targets? The Generality and Persistence of Advantages in Size, Reproduction, and Enemy Release in Invasive Plant Species with Time since Introduction}, volume={170}, DOI={10.1086/522842}, abstractNote={Successful plant invasions are often attributed to increased plant size, reproduction, or release from natural enemies, but the generality and persistence of these patterns remains widely debated. Meta-analysis was used to quantitatively assess invasive plant performance and release from enemy damage and how these change with residence time and geographic distribution. Invasive plants were compared either in their introduced and home ranges or with native congeners in the introduced range. Invasive plants in the introduced range were generally larger, allocated more to reproduction, and had lower levels of herbivore damage compared with conspecifics in the home range; pathogen attack, however, varied widely. In congener comparisons, invasive and native plants did not differ in size or herbivory, but invaders did allocate less to reproduction and had lower levels of pathogen damage. Time since introduction was a significant nonlinear predictor of enemy release for both herbivores and pathogens, with initial release in recently arrived species and little to no release after 50 to 200 years. Geographic distribution was also a significant nonlinear predictor of enemy release. The observed nonlinear relationships are consistent with dynamic invasions and may define targets for eradication efforts if these patterns hold up for individual species.}, number={6}, journal={Am Nat}, publisher={University of Chicago Press}, author={Hawkes, Christine V.}, year={2007}, pages={832–843} }
 @article{hawkes_deangelis_firestone_2007, title={Root Interactions with Soil Microbial Communities and Processes}, DOI={10.1016/b978-012088775-0/50003-3}, abstractNote={Publisher Summary This chapter discusses the recent advances in rhizosphere microbial ecology, the impacts of rhizosphere microbial communities on nutrient cycling, and the importance of rhizosphere processes at larger scales. A common definition of soil is the surface layer of earth that supports plant life. Rhizosphere soil effectively forms a boundary layer between the roots and the surrounding soil. Plant roots grow into and through an extraordinary array of “indigenous” soil microorganisms. Community characterization is not always genotypic in nature, but may occur at different scales ranging from functional diversity to broader taxons to simple abundance. Functional diversity can also be estimated by measuring functional genes that play a role in ecosystem processes. In 16S rDNA analysis of the rhizosphere microbial community, phylogenetic diversity can be related to function only through conventional interpretations. Root-microbial interactions encompass a range of specificity from “highly evolved” symbioses (legume-rhizobium) to less specific associations (arbuscular mycorrhizas). Apparent symbioses are the most likely to develop host-specificity. Plant roots exude a large amount and a complex assortment of organic compounds into the nearby soil. A variety of biotic interactions occur in the rhizosphere that can affect the diversity and composition of the microbial community associated with roots. Global changes in climate and plant communities may further alter microbial communities with consequences for ecosystem process rates. Research since the 1990s has underscored the fact that understanding and quantifying the interactions among plants and soil microbes is essential for understanding both plant and soil microbial community ecology and the roles that these communities play in ecosystem function.}, journal={The Rhizosphere}, publisher={Elsevier BV}, author={Hawkes, Christine V. and DeAngelis, Kristen M. and Firestone, Mary K.}, year={2007}, pages={1–29} }
 @article{hawkes_belnap_carla_firestone_2006, title={Arbuscular Mycorrhizal Assemblages in Native Plant Roots Change in the Presence of Invasive Exotic Grasses}, volume={281}, DOI={10.1007/s11104-005-4826-3}, number={1-2}, journal={Plant Soil}, publisher={Springer Science \mathplus Business Media}, author={Hawkes, Christine V. and Belnap, Jayne and Carla, D’Antonio and Firestone, Mary K.}, year={2006}, month={Mar}, pages={369–380} }
 @article{hawkes_wren_herman_firestone_2005, title={Plant invasion alters nitrogen cycling by modifying the soil nitrifying community}, volume={8}, DOI={10.1111/j.1461-0248.2005.00802.x}, abstractNote={Abstract Plant invasions have dramatic aboveground effects on plant community composition, but their belowground effects remain largely uncharacterized. Soil microorganisms directly interact with plants and mediate many nutrient transformations in soil. We hypothesized that belowground changes to the soil microbial community provide a mechanistic link between exotic plant invasion and changes to ecosystem nutrient cycling. To examine this possible link, monocultures and mixtures of exotic and native species were maintained for 4 years in a California grassland. Gross rates of nitrogen (N) mineralization and nitrification were quantified with 15 N pool dilution and soil microbial communities were characterized with DNA‐based methods. Exotic grasses doubled gross nitrification rates, in part by increasing the abundance and changing the composition of ammonia‐oxidizing bacteria in soil. These changes may translate into altered ecosystem N budgets after invasion. Altered soil microbial communities and their resulting effects on ecosystem processes may be an invisible legacy of exotic plant invasions.}, number={9}, journal={Ecol Letters}, publisher={Wiley-Blackwell}, author={Hawkes, Christine V. and Wren, Ian F. and Herman, Donald J. and Firestone, Mary K.}, year={2005}, month={Sep}, pages={976–985} }
 @article{hawkes_2004, title={Effects of biological soil crusts on seed germination of four endangered herbs in a xeric Florida shrubland during drought}, volume={170}, DOI={10.1023/b:vege.0000019035.56245.91}, number={1}, journal={Plant Ecology}, publisher={Springer Science \mathplus Business Media}, author={Hawkes, Christine V.}, year={2004}, pages={121–134} }
 @article{hawkes_sullivan_2001, title={The Impact of Herbivory on Plants in Different Resource Conditions: A Meta-Analysis}, volume={82}, DOI={10.2307/2680068}, abstractNote={Understanding how plant recovery from herbivory interacts with the resource environment is necessary to predict under what resource conditions plants are most affected by herbivory, and ultimately how herbivory impacts plant population dynamics. It has been commonly assumed that plants are generally best able to recover from herbivory when growing in high resource conditions, an assumption which is supported by some models (e.g., the continuum of responses model) but opposed by others (e.g., the growth rate model). The validity and generality of any effects of resources (light, nutrients, and water) on plant recovery from herbivory were tested with mixed-model, factorial meta-analyses using a log response ratio metric applied to plant growth and reproduction data from the ecological literature. In total, 81 records from 45 studies were included in the growth meta-analysis, and 24 records from 14 studies in the reproduction meta-analysis. High resource levels and the absence of herbivory both strongly increased plant growth and reproduction. There was no significant overall interaction between growth or reproduction after herbivory and resource conditions, but the interaction terms were significant for each plant functional group in the growth meta-analysis. Basal meristem monocots grew significantly more after herbivory in high resources, while both dicot herbs and woody plants grew significantly more after herbivory in low resources. A similar result was found in the 34.6% of growth records where exact- or overcompensation occurred. Overcompensation was more likely in high resources for monocots and in low resources for dicot herbs. The reproduction data set was too small to subdivide. These qualitative differences between monocot and dicot herbs and woody plants explain many of the contradictory results in the literature and show that no single current model can account for the responses of all plants to herbivory.}, number={7}, journal={Ecology}, publisher={JSTOR}, author={Hawkes, Christine V. and Sullivan, Jon J.}, year={2001}, month={Jul}, pages={2045} }
 @article{hawkes_menges_1996, title={The Relationship between Open Space and Fire for Species in a Xeric Florida Shrubland}, volume={123}, DOI={10.2307/2996065}, number={2}, journal={Bulletin of the Torrey Botanical Club}, publisher={JSTOR}, author={Hawkes, Christine V. and Menges, Eric S.}, year={1996}, month={Apr}, pages={81} }
 @article{hawkes_menges_1995, title={Density and Seed Production of a Florida Endemic, Polygonella basiramia, in Relation to Time since Fire and Open Sand}, volume={133}, DOI={10.2307/2426355}, abstractNote={-Density and reproductive output in relation to fire, open sand, and other site factors were determined for Polygonella basiramia. This federally endangered species is endemic to only three ridges in central Florida and found primarily in rosemary (Ceratiola ericoides) dominated sand pine (Pinus clausa) scrub. Twenty-two sites ranging from 5 to >26 yr postfire were sampled. Site factors of openness, time since last fire, dominant species, ground cover, elevation and soil type were examined. Multivariate analyses identified the amount of open sand habitat at a site as the only variable having a significant positive relationship with both plant density and seed production. Seed production actually increased with conspecific density, suggesting that the lack of interspecific competition in open sand gaps helps define P basiramia microhabitat. Open sand habitat is critical in the life history strategy of this obligate-seeding, perennial herb in a community where it must compete with larger, resprouting shrubs and herbs both immediately after fire and during fire-free inter-}, number={1}, journal={American Midland Naturalist}, publisher={JSTOR}, author={Hawkes, Christine V. and Menges, Eric S.}, year={1995}, month={Jan}, pages={138} }