@article{cook_fox_allen_cohrs_ribas-costa_trlica_ricker_carter_rubilar_campoe_et al._2024, title={Forest soil classification for intensive pine plantation management: "Site Productivity Optimization for Trees" system}, volume={556}, ISSN={["1872-7042"]}, DOI={10.1016/j.foreco.2024.121732}, abstractNote={Forest productivity and response to silvicultural treatments are dependent on inherent site resource availability and limitations. Trees have deeper rooting profiles than agronomic crops, so evaluating the impacts of soils, geology, and physiographic province on forest productivity can help guide silvicultural management decisions in southern pine plantations. Here, we describe the Forest Productivity Cooperative’s “Site Productivity Optimization for Trees” (SPOT) system which includes: texture, depth to increase in clay content, drainage class, soil modifiers (i.e., surface attributes, mineralogy, and additional limitations such as root restrictions), geologic formations, and physiographic province. We quantified the total area for each SPOT code in the native range of loblolly pine (Pinus taeda L.), the region’s most commercially important species, and used a remotely-sensed layer to quantify SPOT code areas in managed southern pine (approximately 14 million ha). The most common SPOT code in the native range is also the most planted, a B2WekoGgPD (fine loamy, shallow depth to increase in clay, well-drained, eroded, kaolinitic, granitic, Piedmont soil), spanning 1.1 million ha total, but only 12% in managed southern pine. However, the SPOT code with the greatest percentage of managed southern pine (61%; a D4PoioAmAF, spodic, deep to increase in clay, siliceous, middle Atlantic Coastal Plain, Flatwoods soil) was the 20th most common in the native range with 474,662 ha. We used machine learning and data from decades of “Regionwide” trials to assess the variable importance of SPOT constituents, climate, planting year, and N rate on site index (base age 25 years) and found that planting year was the most important variable, showing an increase of 17 cm site index per year since 1970, followed by maximum vapor pressure deficit, and precipitation. Geology was the top-ranking SPOT variable to explain site index followed by physiographic province. The Regionwide trials represent 72 unique SPOT codes (out of over 10,000 possible in the pine plantations) and approximately one million ha (or about 7% of all soils identified as supporting managed pine). To extrapolate site index values outside of the unique soil and geologic conditions empirically represented, we created a predictive model with an R2 of 0.79 and an RMSE of 1.38 m from SPOT codes alone. With this extrapolation, the Regionwide data predicts 10.5 million ha, or 74%, of all soils under loblolly pine management in its native range. Overall, this system will allow managers to assess their current site productivity, and recommend silvicultural treatments, thus, providing a framework to optimize forest productivity in pine plantations in the southeastern US.}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Cook, Rachel and Fox, Thomas R. and Allen, Howard Lee and Cohrs, Chris W. and Ribas-Costa, Vicent and Trlica, Andrew and Ricker, Matthew and Carter, David R. and Rubilar, Rafael and Campoe, Otavio and et al.}, year={2024}, month={Mar} }
 @article{minick_leggett_sucre_fox_strahm_2021, title={Bioenergy production effects on SOM with depth of loblolly pine forests on Paleaquults in southeastern USA}, volume={27}, ISSN={["2352-0094"]}, DOI={10.1016/j.geodrs.2021.e00428}, abstractNote={Managed loblolly pine (P. taeda L.) forests comprise a major land-use across the “wood basket” of the southeastern US. Lower coastal plain loblolly pine forests can enhance carbon (C) storage in fast-growing vegetation and soils, representing a significant opportunity to manage these forests for improved soil health through an understanding of soil C and nitrogen (N) storage. Furthermore, these forests have unrealized potential to produce biomass for emerging bioenergy markets. Despite this, very little is known about how intensified management (herbaceous bioenergy production) of these forests influences short-term soil organic C (SOC) and soil organic N (SON) pools in surface and subsurface soil horizons. The field site was located in the Lower Coastal Plain of North Carolina, USA in which trees were planted in bedded (e.g., raised) rows (bed) and intercropped with or without switchgrass (P. virgatum L.) between the bedded rows of trees (interbed). Soils were collected from four depths (0–5, 5–15, 15–30, and 30–45 cm) and two locations (bed and interbed regions) and fractionated into light and heavy mineral-associated SOC and SON pools using a sequential density fractionation technique. Bulk soil SOC and SON concentration as well as C:N ratio decreased with depth for both treatments, while 15N became enriched. Free and occluded lighter fractions (< 1.65 g cm−3) had higher SOC and SON concentration (~45% C and ~ 1.15% N) compared to medium (1.65–2.00 g cm−3) and heavy (> 2.00 g cm−3) fractions. At the 0–5 cm depth in interbeds, SOC and SON were concentrated in the free light fraction (~45%), but transitioned to being concentrated in the heaviest mineral-associated fraction at the 15–30 (~55%) and 30–45 (~70%) cm depth. The 15N analysis of density fractions indicated progressive enrichment with increasing density, suggesting increasing incorporation of microbially-derived products into stable mineral-associated soil organic matter (SOM) pools. In the pine-switchgrass treatment, SOC and SON concentrations were higher in the light and medium fractions in beds and interbeds compared to the pine only treatment, particularly at the 30–45 cm depth. The C:N ratio in the pine-switchgrass treatment was higher compared to the pine only treatment indicating inputs of new plant-derived organic matter. Furthermore, the δ13C stable isotope signature was enriched in both the occluded light fraction (1.65 g cm−3) and the mineral-associated fraction (1.65–1.85 g cm−3). Our results suggest that switchgrass intercropping is contributing to the early buildup of SOM in particulate and mineral-associated SOM pools possibly through additions of new root-derived organic matter and the positive effect on soil microbial activity through priming of microbes.}, journal={GEODERMA REGIONAL}, author={Minick, Kevan J. and Leggett, Zakiya H. and Sucre, Eric B. and Fox, Thomas R. and Strahm, Brian D.}, year={2021}, month={Dec} }
 @article{albaugh_maier_campoe_yanez_carbaugh_carter_cook_rubilar_fox_2020, title={Crown architecture, crown leaf area distribution, and individual tree growth efficiency vary across site, genetic entry, and planting density}, volume={34}, ISSN={["1432-2285"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85071645632&partnerID=MN8TOARS}, DOI={10.1007/s00468-019-01898-3}, abstractNote={We examined crown architecture and within crown leaf area distribution effects on Pinus taeda L. growth in North Carolina (NC), Virginia (VA), and Brazil (BR) to better understand why P. taeda can grow much better in Brazil than in the southeastern United States. The NC, VA, and BR sites were planted in 2009, 2009, and 2011, respectively. At all sites, we planted the same two genetic entries at 618, 1236, and 1854 trees ha−1. In 2013, when trees were still open grown, the VA and NC sites had greater branch diameter (24%), branch number (14%), live crown length (44%), foliage mass (82%), and branch mass (91%), than the BR site. However, in 2017, after crown closure and when there was no significant difference in tree size, site did not significantly affect these crown variables. In 2013, site significantly affected absolute leaf area distribution, likely due to differences in live crown length and leaf area, such that there was more foliage at a given level in the crown at the VA and NC sites than at the BR site. In 2017, site was still a significant factor explaining leaf area distribution, although at this point, with crown closure and similar sized trees, there was more foliage at the BR site at a given level in the crown compared to the VA and NC sites. In 2013 and 2017, when including site, genetic entry, stand density, and leaf area distribution parameters as independent variables, site significantly affected individual tree growth efficiency, indicating that something other than leaf area distribution was influencing the site effect. Better BR P. taeda growth is likely due to a combination of factors, including leaf area distribution, crown architecture, and other factors that have been identified as influencing the site effect (heat sum), indicating that future work should include a modeling analysis to examine all known contributing factors.}, number={1}, journal={TREES-STRUCTURE AND FUNCTION}, author={Albaugh, Timothy J. and Maier, Chris A. and Campoe, Otavio C. and Yanez, Marco A. and Carbaugh, Eric D. and Carter, David R. and Cook, Rachel L. and Rubilar, Rafael A. and Fox, Thomas R.}, year={2020}, month={Feb}, pages={73–88} }
 @article{raymond_fox_cook_albaugh_rubilar_2020, title={Losses of fertilizer nitrogen after a winter fertilization in three managed pine plantations of the southeastern United States}, volume={84}, ISSN={["1435-0661"]}, url={http://www.scopus.com/inward/record.url?eid=2-s2.0-85081895628&partnerID=MN8TOARS}, DOI={10.1002/saj2.20017}, abstractNote={Abstract}, number={2}, journal={SOIL SCIENCE SOCIETY OF AMERICA JOURNAL}, author={Raymond, Jay E. and Fox, Thomas R. and Cook, Rachel L. and Albaugh, Timothy J. and Rubilar, Rafael}, year={2020}, pages={609–617} }
 @article{lin_domec_ward_marshall_kin_laviner_fox_west_sun_mcnulty_et al._2019, title={Using delta C-13 and delta O-18 to analyze loblolly pine (Pinus taeda L.) response to experimental drought and fertilization}, volume={39}, ISSN={["1758-4469"]}, DOI={10.1093/treephys/tpz096}, abstractNote={Abstract}, number={12}, journal={TREE PHYSIOLOGY}, author={Lin, Wen and Domec, Jean-Christophe and Ward, Eric J. and Marshall, John and Kin, John S. and Laviner, Marshall A. and Fox, Thomas R. and West, Jason B. and Sun, Ge and McNulty, Steve and et al.}, year={2019}, month={Dec}, pages={1984–1994} }
 @article{albaugh_stape_fox_rubilar_allen_2012, title={Midrotation Vegetation Control and Fertilization Response in Pinus taeda and Pinus elliottii across the Southeastern United States}, volume={36}, ISSN={["0148-4419"]}, DOI={10.5849/sjaf.10-042}, abstractNote={We examined fertilization (224 and 56 kg ha−1 of elemental nitrogen and phosphorus, applied as urea and diammonium phosphate, respectively) and vegetation control (one-time site-specific application) in a 2 × 2 factorial design with three or four replicates at each site on 13 sites (10 in Pinus taeda and 3 in Pinus elliottii). Nitrogen and phosphorus limited pine growth on seven sites where we found significant volume growth responses to fertilization in at least one measurement period. Five sites had significant volume growth responses to vegetation control in at least one measurement period. Biologic response treatment order was fertilizer plus vegetation control > fertilizer > vegetation control. The combined treatment effects were additive, indicating that resources other than nitrogen and phosphorus were being ameliorated by the vegetation control. Vegetation control response was not related to estimates of competing vegetation basal area, and its duration was likely limited by regrowth of competing vegetation on some sites. Competing vegetation leaf area was proposed as a good metric by which to estimate the extent of interference of noncrop vegetation. We recommend that future work examining vegetation control focus on a process approach to better understand the influences of competing vegetation on crop tree growth.}, number={1}, journal={SOUTHERN JOURNAL OF APPLIED FORESTRY}, author={Albaugh, Timothy J. and Stape, Jose L. and Fox, Thomas R. and Rubilar, Rafael A. and Allen, H. Lee}, year={2012}, month={Feb}, pages={44–53} }
 @article{rubilar_allen_alvarez_albaugh_fox_stape_2010, title={Silvicultural manipulation and site effect on above and belowground biomass equations for young Pinus radiata}, volume={34}, ISSN={["1873-2909"]}, DOI={10.1016/j.biombioe.2010.07.015}, abstractNote={There is little understanding of how silvicultural treatments, during the early stages of tree development, affect allometric relationships. We developed and compared stem, branch, foliage, coarse and fine root biomass, and leaf area estimation equations, for four-year-old genetically improved radiata pine trees grown on three contrasting soil-site conditions. At each site, selected trees were destructively sampled from a control (shovel planted, no weed control, fertilized with 2 g of boron), a shovel planted + weed control (2 first years) + complete fertilization (nitrogen + phosphorus + boron 2 first years + potassium 2nd year), and a soil tillage (subsoil at 60 cm) + weed control (first 2 years) + complete fertilization treatment. Tissues were separated into foliage, branch, stem, fine and coarse roots (>2 mm). Regression equations for each tree biomass tissue versus leaf area were fit for each site and compared among treatments and sites with the same genetic material. Our results indicated that individual tree biomasses for young plantations are affected by silvicultural treatment and site growing conditions. Higher variability in estimates was found for foliage and branches due to the ephemeral nature of these components. Stem biomass equations vary less, but differences in biomass equations were found among sites and treatments. Coarse root biomass estimates were variable but less than expected, considering the gradient among sites. Similar to stem biomass, a simple positive general linear relationship between root collar diameter, or diameter at breast height with coarse roots biomass was developed across sites and treatments.}, number={12}, journal={BIOMASS & BIOENERGY}, author={Rubilar, Rafael A. and Allen, H. Lee and Alvarez, Jose S. and Albaugh, Timothy J. and Fox, Thomas R. and Stape, Jose L.}, year={2010}, month={Dec}, pages={1825–1837} }
 @article{carlson_burkhart_allen_fox_2008, title={Absolute and relative changes in tree growth rates and changes to the stand diameter distribution of Pinus taeda as a result of midrotation fertilizer applications}, volume={38}, ISSN={["0045-5067"]}, DOI={10.1139/X08-050}, abstractNote={ Silvicultural treatments have the potential to change the diameter distribution of a stand, which can alter the final product mix of the stand. Growth and yield models need to account for these changes in the diameter distribution to assess the economic viability of the silvicultural operations. We investigated how the diameter distribution of Pinus taeda L. stands changes as a result of midrotation fertilization. Data from 43 installations of a nitrogen and phosphorus midrotation fertilizer trial series established in the southeastern United States were used in the study. The results indicated that both the absolute growth response and the relative growth response of individual trees were greater among the larger trees. A three-parameter Weibull distribution fitted at each study site was used to investigate how the parameters of the distribution changed with time and treatment. The location and scale parameters of the Weibull distribution were both affected by fertilization. Stand variables, such as site index, age, stand density, and mean diameter at time of fertilization, also affected the location and scale parameters. The shape parameter was not affected by any of the treatments in this study. }, number={7}, journal={CANADIAN JOURNAL OF FOREST RESEARCH-REVUE CANADIENNE DE RECHERCHE FORESTIERE}, author={Carlson, Colleen A. and Burkhart, Harold E. and Allen, H. Lee and Fox, Thomas R.}, year={2008}, month={Jul}, pages={2063–2071} }
 @article{carlson_fox_allen_albaugh_2008, title={Modeling mid-rotation fertilizer responses using the age-shift approach}, volume={256}, ISSN={["0378-1127"]}, DOI={10.1016/j.foreco.2008.04.020}, abstractNote={Growth and yield modelers have incorporated mid-rotation fertilizer responses by: modifying site index; developing new models to include fertilizer responses directly; using multipliers or additional terms to scale existing models. We investigated the use of age-shifts to model mid-rotation fertilizer responses. Age-shift prediction models were constructed from 43 installations of a nitrogen (0, 112, 224 and 336 kg ha−1 elemental) by phosphorus (0, 28 and 56 kg ha−1 elemental) factorial experiment established in mid-rotation loblolly (Pinus taeda L.) pine stands in the southeastern US. Age-shifts for dominant height and basal area increased with time after fertilization, to a maximum and then either remained fairly constant, or declined. The initial rate of increase, maximum age-shift and decline were functions of the rate and combinations of fertilizers applied, as well as stand density and age at fertilization. Volume age-shifts increased linearly throughout the 10-year measurement period for most treatments with the rate of increase being a function of the elements applied, stocking, site index and age at fertilization. A mid-rotation fertilizer application of 224 and 28 kg ha−1 elemental N and P, respectively, resulted in age-shifts of 1.1, 1.9 and 2.4 years for dominant height, basal area and volume, respectively, 10 years after fertilization. The age-shifts were incorporated into growth and yield models.}, number={3}, journal={FOREST ECOLOGY AND MANAGEMENT}, author={Carlson, Colleen A. and Fox, Thomas R. and Allen, H. Lee and Albaugh, Timothy J.}, year={2008}, month={Jul}, pages={256–262} }
 @article{albaugh_allen_fox_2008, title={Nutrient use and uptake in Pinus taeda}, volume={28}, ISSN={["0829-318X"]}, DOI={10.1093/treephys/28.7.1083}, abstractNote={We quantified nitrogen (N), phosphorus (P), potassium (K), calcium (Ca) and magnesium (Mg) content, use (nutrient amount for one growth year), retranslocation (nutrients recycled before foliage senescence), uptake (use minus retranslocation), volume production per unit of uptake and fertilizer-uptake efficiency (percent applied taken up) in a 2 x 2 (nutrient and water) factorial experiment replicated four times in an 8-year-old loblolly pine (Pinus taeda L.) stand growing on a nutrient-poor sandy soil in Scotland County, North Carolina, USA. Over 14 years, we applied 1140, 168, 393, 168 and 146 kg ha(-1) of elemental N, P, K, Ca and Mg fertilizer, respectively, and an average of 710 mm year(-1) of irrigation. All plots received complete vegetation control. Fertilization about doubled tissue N, P, K and Mg contents at age 21, whereas irrigation resulted in smaller increases in nutrient contents. Maximum annual uptake was 101, 9.3, 44, 37 and 13 kg ha(-1) year(-1) and volume production per unit of nutrient uptake was 0.35, 3.5, 0.66, 1.1 and 3.1 m(3) kg(-1), for N, P, K, Ca and Mg, respectively. Irrigated plots had greater volume production per unit of N, P, K and Mg uptake than control plots, likely because irrigation allowed photosynthesis to continue during dry periods. Fertilized plus irrigated plots had less volume production per unit of these elements than the fertilized plots either because nutrient uptake exceeded the requirement for optimum growth or because available water (rainfall plus irrigation) was insufficient for the leaf area achieved with fertilization. At age 19, fertilizer-uptake efficiencies for N, P, K, Ca and Mg were 53, 24, 62, 57 and 39%, respectively, and increased with irrigation to 68, 36, 78, 116 and 55%, respectively. The scale of fertilizer uptake was likely a result of low native site nutrient availability, study longevity, measurement of all tissue components on site, a comprehensive assessment of coarse roots, and the 3-m rooting depth. Ecosystem nitrogen retention (applied nitrogen found in living plant material, litter fall and soil to 150-cm depth) was estimated at 79% at age 17, a value that would likely be greater when including soil nitrogen to rooting depth and calculating retention at age 21 when the study ended. The ecosystem retention value provides evidence that intensive site resource management can be accomplished with low likelihood of applied materials moving offsite.}, number={7}, journal={TREE PHYSIOLOGY}, author={Albaugh, Timothy J. and Allen, H. Lee and Fox, Thomas R.}, year={2008}, month={Jul}, pages={1083–1098} }
 @article{albaugh_allen_fox_2007, title={Historical patterns of forest fertilization in the southeastern United States from 1969 to 2004}, volume={31}, number={3}, journal={Southern Journal of Applied Forestry}, author={Albaugh, T. J. and Allen, H. L. and Fox, T. R.}, year={2007}, pages={129–137} }
 @misc{fox_jokela_allen_2007, title={The development of pine plantation silviculture in the southern United States}, volume={105}, number={7}, journal={Journal of Forestry}, author={Fox, T. R. and Jokela, E. J. and Allen, H. L.}, year={2007}, pages={337–347} }
 @inbook{fox_jokela_allen_2004, title={The evolution of pine plantation silviculture in the southern United States}, booktitle={Southern forest science: Past, present, future}, publisher={Asheville, NC: Southern Research Station}, author={Fox, T. R. and Jokela, E. J. and Allen, H. L.}, editor={Rauscher, H. M. and Johnsen, K.Editors}, year={2004}, pages={63–82} }
 @article{fox_1986, title={Raspberry (Rubus idaeus L.) competition effects on balsam fir (Abies balsamea (L.) Mill.) seedlings in northern Maine}, volume={37}, number={2}, journal={Tree Planters' Notes}, author={Fox, T. R.}, year={1986}, pages={20} }