Landscape dynamics and ecological change in the Southern Appalachians
Coweeta LTER, historical land use, land-use change, climate, Southern Appalachians, plant performance, bird community, ecosystem services
Our prior CWT research focused extensively on understanding the patterns and ecological implications of land-use changes throughout the Southern Appalachian region; the role of climate received less attention. The steep environmental gradients that characterize the Southern Appalachians provide an outstanding opportunity for studying climate effects on vegetation and how climate and land-use change may interact. Our current studies focus on understanding the effects of climate and land-use on biodiversity, emphasizing native forest understory herbs and bird populations. For the southern Appalachians and Piedmont, projections of land-cover change with global warming indicate strong sensitivity to increasing aridity. Forests are expected to expand under more moderate scenarios, where moisture stress is less severe, but decline under more extreme climate scenarios. Temperate deciduous forest communities are likely to be replaced by southeast mixed forests in most scenarios, but if moisture is sufficiently limiting, replacement by savanna/woodland may occur. Mammal and bird richness are also predicted to decline in much of the southern US. Few (if any) studies have been considering understory species, however. We are conducting studies that evaluate the joint effects of climate and land-use on native forest herbs and vertebrates (especially birds), and we continue to collaborate closely with Scott Pearson (Mars Hill College).
Herbaceous plants and their pollinators. Michelle Jackson initiated her studies of the interaction between land-use history and climate variation as it affects establishment and growth of native herbaceous species during summer 2009. Both land-use history and climate can play a vital role in influencing the composition and structure of forest communities. This study examines how changes in land use, particularly logging history, and climate variability affect the distribution, germination, performance and population dynamics of native forest herbs and addresses three overarching questions: (1) How do the current distribution and abundance of forest herbs differ along natural climate and environmental gradients at different spatial extents? (2) How are germination and performance of experimentally planted and naturally growing forest herbs affected by gradients of stand age and climate? (3) How are plant-pollinator interactions affected by land-use history and climate? Read more about Michelle’s work…
Avian communities. For her MS, Heather Lumpkin studied the effects of climate and exurban development on Southern Appalachian avian communities (Lumpkin 2011). Climate variability and land-use dynamics have important effects on many terrestrial systems, yet very few empirical studies examine both of these. Exurban development, one of the fastest growing forms of land use in the United States, may affect wildlife through habitat fragmentation or building presence may alter habitat quality. We studied the impacts of building density, forest canopy cover, and daily mean temperature on bird species occurrence at 140 study sites in the Southern Appalachian Mountains (North Carolina, USA). Occupancy models were used to determine 36 bird species' associations with these factors, and an interaction between building density and mean temperature. Species responses varied with habitat requirement, geographic center of breeding range, and migration distance. Forest-interior species and Neotropical migrants were negatively associated with building density, and these species groups were associated with lower temperatures found at high elevations. Short-distance migrants and resident species were relatively tolerant of buildings. Warmer temperatures were associated with an increase in southern species and a decrease in northern species. Both building density and temperature were significant for 7 species, and their interaction was important for 3 species. As exurban development expands in the Southern Appalachians, forest interior species and Neotropical migrants are likely to decline, and edge species are not likely to benefit, suggesting an overall negative net impact on the bird community. Moreover, warming climates may exacerbate these negative effects.
Land-use and climate change have likely contributed to population declines in interior-forest and Neotropical migrant bird species in eastern North America, but the causative mechanisms are not well understood. We conducted a nest predation experiment in forested plots in the Southern Appalachian Mountains (North Carolina, USA) during the 2009 and 2010 breeding seasons to determine the effects of exurban development and climate on nest survival and predator presence (Lumpkin et al. 2012). Artificial nests were baited with quail eggs and monitored for 18 days. Clay eggs, BiofoamTM track plates, and motion-triggered cameras were used to detect nest predators. Nest survival decreased with mean temperature and, to a lesser extent, building density. Nests on the ground had lower survival than those in trees, likely due to increased predation of ground nests by opossum and other carnivores. Many interior-forest, Neotropical migrants occur at high elevations, and our results indicate that these species may face increased nest predation if climate warms in the Southern Appalachians.
We are now extending our studies to consider spatially explicit landscape models in the context of regional change. Our focus will include synthesis of our past work and consideration of ecosystem services and landscape sustainability. These directions will be developed as part of Rose Graves’ doctoral studies.
Jackson, M. M., M. G. Turner, S. M. Pearson and A. R. Ives. Seeing the forest and the trees: multilevel models reveal both species and community patterns. (In review).
Lumpkin, H. A. 2011. Effects of climate and exurban development on bird species and nest predation in the Southern Appalachians. MS Thesis, Department of Zoology, University of Wisconsin, Madison.
Lumpkin, H. A., S. M. Pearson and M. G. Turner. 2012. Climate and exurban development affect nest predation and nest predator presence in the Southern Appalachians. Conservation Biology (In press).
This research is funded by the LTER program of the National Science Foundation.