@article{potter_riitters_2022, title={A National Multi-Scale Assessment of Regeneration Deficit as an Indicator of Potential Risk of Forest Genetic Variation Loss}, volume={13}, ISSN={["1999-4907"]}, url={https://doi.org/10.3390/f13010019}, DOI={10.3390/f13010019}, abstractNote={Genetic diversity is essential because it provides a basis for adaptation and resilience to environmental stress and change. The fundamental importance of genetic variation is recognized by its inclusion in the Montréal Process sustainability criteria and indicators for temperate and boreal forests. The indicator that focuses on forest species at risk of losing genetic variation, however, has been difficult to address in a systematic fashion. We combined two broad-scale datasets to inform this indicator for the United States: (1) tree species occurrence data from the national Forest Inventory and Analysis (FIA) plot network and (2) climatically and edaphically defined provisional seed zones, which are proxies for among-population adaptive variation. Specifically, we calculated the estimated proportion of small trees (seedlings and saplings) relative to all trees for each species and within seed zone sub-populations, with the assumption that insufficient regeneration could lead to the loss of genetic variation. The threshold between sustainable and unsustainable proportions of small trees reflected the expectation of age–class balance at the landscape scale. We found that 46 of 280 U.S. forest tree species (16.4%) may be at risk of losing genetic variation. California and the Southeast encompassed the most at-risk species. Additionally, 39 species were potentially at risk within at least half of the seed zones in which they occurred. Seed zones in California and the Southwest had the highest proportions of tree species that may be at risk. The results could help focus conservation and management activities to prevent the loss of adaptive genetic variation within tree species.}, number={1}, journal={FORESTS}, author={Potter, Kevin M. and Riitters, Kurt}, year={2022}, month={Jan} }
 @article{potter_riitters_guo_2022, title={Non-native tree regeneration indicates regional and national risks from current invasions}, volume={5}, ISSN={["2624-893X"]}, DOI={10.3389/ffgc.2022.966407}, abstractNote={Non-native (introduced, exotic, and alien) species alter forest ecosystem processes, cause landscape change, interfere with services provided by native trees, and contribute to biotic homogenization. To quantify the degree of invasion by non-native trees in the United States, we combined two broad-scale datasets: (1) tree species occurrence data from the national Forest Inventory and Analysis (FIA) plot network and (2) ecoregions characterized by relatively homogeneous environmental conditions. Using the FIA statistical design, we created an indicator of non-native tree regeneration success by estimating the proportion of small trees (seedlings and saplings) relative to all trees for non-native species in the conterminous United States and southeast Alaska, Hawaii, and Puerto Rico. Species with at least 75 percent of their stems consisting of smaller stems were classified as highly invasive while those with 60 percent to 75 percent of smaller stems were classified as moderately invasive. Above these thresholds, non-native species are of ecological concern because they are established and reproducing successfully and therefore likely to continue to spread in the future. For the conterminous United States and southeast Alaska, we identified 16 highly invasive and four moderately invasive non-native tree species. Widespread highly invasive and relatively well-established species included Ailanthus altissima, Triadica sebifera, and Ulmus pumila. The richness of highly invasive species was the highest in parts of the Midwest and Mid-Atlantic States, followed by much of the Southeast. In Hawaii, we identified seven highly invasive and three moderately invasive non-native tree species. The most widespread highly invasive and well-established tree species in the archipelago were Psidium cattleyanum, Psidium guajava, Ardisia elliptica, and Syzygium cumini. The largest numbers of highly invasive species were inventoried in the lowland/leeward dry and mesic forests of O’ahu and the lowland wet and mesic forests of Hawai’i Island. Puerto Rico had 17 highly invasive and two moderately invasive tree species. The most widespread and well-established non-native species were Leucaena leucocephala, Spathodea campanulata, Coffea arabica, Syzygium jambos, and Melicoccus bijugatus. The results of this assessment offer insights into which species are most likely to alter forest ecosystems and which forests may be effectively managed to control invasive trees.}, journal={FRONTIERS IN FORESTS AND GLOBAL CHANGE}, author={Potter, Kevin M. and Riitters, Kurt H. and Guo, Qinfeng}, year={2022}, month={Aug} }
 @article{costanza_riitters_vogt_wickham_2019, title={Describing and analyzing landscape patterns: where are we now, and where are we going?}, volume={34}, ISSN={0921-2973 1572-9761}, url={http://dx.doi.org/10.1007/s10980-019-00889-6}, DOI={10.1007/s10980-019-00889-6}, number={9}, journal={Landscape Ecology}, publisher={Springer Science and Business Media LLC}, author={Costanza, Jennifer K. and Riitters, Kurt and Vogt, Peter and Wickham, James}, year={2019}, month={Aug}, pages={2049–2055} }
 @article{riitters_costanza_2019, title={The landscape context of family forests in the United States: Anthropogenic interfaces and forest fragmentation from 2001 to 2011}, volume={188}, ISSN={0169-2046}, url={http://dx.doi.org/10.1016/j.landurbplan.2018.04.001}, DOI={10.1016/j.landurbplan.2018.04.001}, abstractNote={The capacity of family owned forests to sustain ecological goods and services depends on the landscape context within which that forest occurs. For example, the expansion of a nearby urban area results in the loss of adjacent forest, which threatens the ability of the family forest to sustain interior forest habitat. Our objective was to assess the status and change of the landscape context of family forests across the conterminous United States, as measured by interior forest status and anthropogenic (urban and agricultural) interface zones. We combined circa 2005 forest inventory data with land cover maps from 2001 and 2011 to evaluate changes in the vicinity of 132,497 inventory locations. We compared family forests to nonfamily private and public forests, and evaluated regional conservation opportunities for family forests. Between 2001 and 2011, 1.5% of family forest area experienced a change of anthropogenic interface zone, and 46% was in an interface zone by 2011. During that same time, there was a net decrease of 9.7% of family owned interior forest area, such that 27% of family forest was interior forest by 2011. The rates of forest fragmentation and occurrence in anthropogenic interface zones were higher for family and nonfamily private forests than for public forest, yet family forests contained 31% of the extant interior forest area. The geography of landscape patterns suggested where aggregate actions by family forest owners may have relatively large regional effects upon extant interior forest conditions.}, journal={Landscape and Urban Planning}, publisher={Elsevier BV}, author={Riitters, Kurt and Costanza, Jennifer}, year={2019}, month={Aug}, pages={64–71} }
 @article{guo_riitters_potter_2018, title={A Subcontinental Analysis of Forest Fragmentation Effects on Insect and Disease Invasion}, volume={9}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f9120744}, DOI={10.3390/f9120744}, abstractNote={The influences of human and physical factors on species invasions have been extensively examined by ecologists across many regions. However, how habitat fragmentation per se may affect forest insect and disease invasion has not been well studied, especially the related patterns over regional or subcontinental scales. Here, using national survey data on forest pest richness and fragmentation data across United States forest ecosystems, we examine how forest fragmentation and edge types (neighboring land cover) may affect pest richness at the county level. Our results show that habitat fragmentation and edge types both affected pest richness. In general, specialist insects and pathogens were more sensitive to fragmentation and edge types than generalists, while pathogens were much less sensitive to fragmentation and edge types than insect pests. Most importantly, the developed land edge type contributed the most to the richness of nonnative insects and diseases, whether measured by the combination of all pest species or by separate guilds or species groups (i.e., generalists vs. specialists, insects vs. pathogens). This observation may largely reflect anthropogenic effects, including propagule pressure associated with human activities. These results shed new insights into the patterns of forest pest invasions, and it may have significant implications for forest restoration and management.}, number={12}, journal={Forests}, publisher={MDPI AG}, author={Guo, Qinfeng and Riitters, Kurt and Potter, Kevin}, year={2018}, month={Nov}, pages={744} }
 @article{riitters_potter_iannone_oswalt_guo_fei_2018, title={Exposure of Protected and Unprotected Forest to Plant Invasions in the Eastern United States}, volume={9}, ISSN={1999-4907}, url={http://dx.doi.org/10.3390/f9110723}, DOI={10.3390/f9110723}, abstractNote={Research Highlights: We demonstrate a macroscale framework combining an invasibility model with forest inventory data, and evaluate regional forest exposure to harmful invasive plants under different types of forest protection. Background and Objectives: Protected areas are a fundamental component of natural resource conservation. The exposure of protected forests to invasive plants can impede achievement of conservation goals, and the effectiveness of protection for limiting forest invasions is uncertain. We conducted a macroscale assessment of the exposure of protected and unprotected forests to harmful invasive plants in the eastern United States. Materials and Methods: Invasibility (the probability that a forest site has been invaded) was estimated for 82,506 inventory plots from site and landscape attributes. The invaded forest area was estimated by using the inventory sample design to scale up plot invasibility estimates to all forest area. We compared the invasibility and the invaded forest area of seven categories of protection with that of de facto protected (publicly owned) forest and unprotected forest in 13 ecological provinces. Results: We estimate approximately 51% of the total forest area has been exposed to harmful invasive plants, including 30% of the protected forest, 38% of the de facto protected forest, and 56% of the unprotected forest. Based on cumulative invasibility, the relative exposure of protection categories depended on the assumed invasibility threshold. Based on the invaded forest area, the five least-exposed protection categories were wilderness area (13% invaded), national park (18%), sustainable use (26%), nature reserve (31%), and de facto protected Federal land (36%). Of the total uninvaded forest area, only 15% was protected and 14% had de facto protection. Conclusions: Any protection is better than none, and public ownership alone is as effective as some types of formal protection. Since most of the remaining uninvaded forest area is unprotected, landscape-level management strategies will provide the most opportunities to conserve it.}, number={11}, journal={Forests}, publisher={MDPI AG}, author={Riitters, Kurt and Potter, Kevin and Iannone, Basil, III and Oswalt, Christopher and Guo, Qinfeng and Fei, Songlin}, year={2018}, month={Nov}, pages={723} }
 @article{coulston_ambrose_riiters_conkling_2005, title={Forest health monitoring: 2002 National Technical Report}, journal={Forest health monitoring : 2002 national technical report}, publisher={Asheville, NC : U.S. Dept. of Agriculture, Forest Service, Southern Research Station}, author={Coulston, J. and Ambrose, M. J. and Riiters, K. H. and Conkling, B. L.}, year={2005} }
 @article{coulston_ambrose_riiters_conkling_smith_2005, title={Forest health monitoring: 2003 National Technical Report}, journal={Forest health monitoring : 2003 national technical report}, publisher={Asheville, NC : U.S. Dept. of Agriculture, Forest Service, Southern Research Station}, author={Coulston, J. W. and Ambrose, M. J. and Riiters, K. H. and Conkling, B. L. and Smith, W. D.}, year={2005} }
 @article{coulston_riitters_2005, title={Preserving biodiversity under current and future climates: a case study}, volume={14}, DOI={10.1111/j.1466-822x.2004.00135.x}, abstractNote={ABSTRACT}, number={1}, journal={Global Ecology and Biogeography}, author={Coulston, J. W. and Riitters, K. H.}, year={2005}, pages={31–38} }
 @article{riitters_wickham_coulston_2004, title={A preliminary assessment of Montreal Process indicators of forest fragmentation for the United States}, volume={91}, ISSN={["1573-2959"]}, DOI={10.1023/B:EMAS.0000009240.65355.92}, abstractNote={As part of the U.S. 2003 National Report on Sustainable Forests, four metrics of forest fragmentation--patch size, edge amount, inter-patch distance, and patch contrast--were measured within 137744 non-overlapping 5625 ha analysis units on land-cover maps derived from satellite imagery for the 48 conterminous States. The perimeter of a typical forest patch is about 100 m from the perimeter of its nearest neighbor, except when there is not much forest, in which case that distance is 200 to 300 m. A typical analysis unit has from 10 to 40% as much forest edge as it could possibly have, given the amount of forest present. Most analysis units contain a large number of patches that are less than one hectare in size, and about 10% contain one or more 2000 to 5000 ha patches. Forest often defines the background landscape, and patch contrast is generally either very high or very low in eastern regions and intermediate in western regions. Many research needs were identified by this experimental analysis of available data and metrics.}, number={1-3}, journal={ENVIRONMENTAL MONITORING AND ASSESSMENT}, author={Riitters, KH and Wickham, JD and Coulston, JW}, year={2004}, month={Feb}, pages={257–276} }
 @article{coulston_riitters_smith_2004, title={A preliminary assessment of the Montreal process indicators of air pollution for the United States}, volume={95}, ISSN={["1573-2959"]}, DOI={10.1023/B:EMAS.0000029895.96868.f8}, abstractNote={Air pollutants pose a risk to forest health and vitality in the United States. Here we present the major findings from a national scale air pollution assessment that is part of the United States' 2003 Report on Sustainable Forests. We examine trends and the percent forest subjected to specific levels of ozone and wet deposition of sulfate, nitrate, and ammonium. Results are reported by Resource Planning Act (RPA) reporting region and integrated by forest type using multivariate clustering. Estimates of sulfate deposition for forested areas had decreasing trends (1994-2000) across RPA regions that were statistically significant for North and South RPA regions. Nitrate deposition rates were relatively constant for the 1994 to 2000 period, but the South RPA region had a statistically decreasing trend. The North and South RPA regions experienced the highest ammonium deposition rates and showed slightly decreasing trends. Ozone concentrations were highest in portions of the Pacific Coast RPA region and relatively high across much of the South RPA region. Both the South and Rocky Mountain RPA regions had an increasing trend in ozone exposure. Ozone-induced foliar injury to sensitive species was recorded in all regions except for the Rocky Mountain region. The multivariate analysis showed that the oak-hickory and loblolly-shortleaf pine forest types were generally exposed to more air pollution than other forest types, and the redwood, western white pine, and larch forest types were generally exposed to less. These findings offer a new approach to national air pollution assessments and are intended to help focus research and planning initiatives related to air pollution and forest health.}, number={1-3}, journal={ENVIRONMENTAL MONITORING AND ASSESSMENT}, author={Coulston, JW and Riitters, KH and Smith, GC}, year={2004}, month={Jul}, pages={57–74} }
 @article{riitters_wickham_o'neill_jones_smith_coulston_wade_smith_2002, title={Fragmentation of continental United States forests}, volume={5}, DOI={10.1007/s10021002-0209-2}, number={8}, journal={Ecosystems}, author={Riitters, K. H. and Wickham, J. D. and O'Neill, R. V. and Jones, K. B. and Smith, E. R. and Coulston, J. W. and Wade, T. G. and Smith, J. H.}, year={2002}, pages={815–822} }
 @article{wickham_riitters_rv o'neill_reckhow_wade_jones_2000, title={Land cover as a framework for assessing risk of water pollution}, volume={36}, ISSN={["1093-474X"]}, DOI={10.1111/j.1752-1688.2000.tb05736.x}, abstractNote={ABSTRACT:  A survey of numerous field studies shows that nitrogen and phosphorous export coefficients are significantly different across forest, agriculture, and urban land‐cover types. We used simulations to estimate the land‐cover composition at which there was a significant risk of nutrient loads representative of watersheds without forest cover. The results suggest that at between 20 percent and 30 percent nonforest cover, there is a 10 percent or greater chance of N or P nutrient loads being equivalent to the median values of predominantly agricultural or urban watersheds. The methods apply to environmental management for assessing the risk to increased nonpoint nutrient pollution. Interpretation of the risk measures are discussed relative to their application for a single watershed and across a region comprised of several watersheds.}, number={6}, journal={JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION}, author={Wickham, JD and Riitters, KH and RV O'Neill and Reckhow, KH and Wade, TG and Jones, KB}, year={2000}, month={Dec}, pages={1417–1422} }
 @article{rv o'neill_riitters_wickham_jones_1999, title={Landscape pattern metrics and regional assessment}, volume={5}, ISSN={["1076-2825"]}, DOI={10.1046/j.1526-0992.1999.09942.x}, abstractNote={ABSTRACT The combination of remote imagery data, geographic information systems software, and landscape ecology theory provides a unique basis for monitoring and assessing large‐scale ecological systems. The unique feature of the work has been the need to develop and interpret quantitative measures of spatial pattern—the landscape indices. This article reviews what is known about the statistical properties of these pattern metrics and suggests some additional metrics based on island biogeography, percolation theory, hierarchy theory, and economic geography. Assessment applications of this approach have required interpreting the pattern metrics in terms of specific environmental endpoints, such as wildlife and water quality, and research into how to represent synergystic effects of many overlapping sources of stress.}, number={4}, journal={ECOSYSTEM HEALTH}, author={RV O'Neill and Riitters, KH and Wickham, JD and Jones, KB}, year={1999}, month={Dec}, pages={225–233} }