We began this research in November 1994 funded by an LTER augmentation grant. The research  focused on two watersheds, Little Tennessee (LT) and French Broad (FB) Rivers, because these offer a contrast in the pattern of land-use change. LT retains large areas of forested land, while FB has a longer history of forest fragmentation. By using aerial photographs to analyze changes in land-use in this region over the past 5 decades, we have been able to document significant differential disturbance related to landform and topographic position. Prior to the mid- 1950s permanent vegetation alteration was concentrated in low-elevation coves and flats and near urban areas. Current disturbance is much more likely at mid-to higher-elevation steeper sites, and farther from urban centers.

Impacts of land-use change on regional C cycles
Summary:  The impacts of land-use change on C budgets have been determined by combining our small scale measurements with landscape-level C budget modeling.

We established sites in 3 regions of the southern Appalachians (LT, FB and southwestern Virginia) that are in early successional forest (<30 yr), mature forest (80-150 yr), old-growth forest (>150 yr), and pasture (Figure 9). In forested sites, plots are located in cove, slope, and ridge positions. At each site we have quantified carbon pools (soil, forest floor, and plant), measured flux rates, and developed net ecosystem carbon budgets.

The results show that large differences exist in woody biomass pools among land-use types: e.g., woody biomass in the old growth forest is 2- to 8-fold greater than early and mid-successional sites. Variation across topographic positions is also evident, although of lesser magnitude than across land-use types. There are also large differences in the distribution of biomass among species across topographic positions. If there are large differences in respiration rate among species, then species distribution could directly influence C balance among and within land-use types. Therefore, we measured tree stem CO2 flux attributable to both growth and maintenance respiration . Soil CO2 flux measurements were greatest in June when soils were warmest and lowest in early spring and late fall when soils were coolest. There appear to be large differences in C cycling among land-use types. The roles of litter and soil temperature, soil moisture, fine and coarse root mass, root and soil N and C, and litter mass N and C that regulate these differences have been analyzed (more).

 Impacts of land-use change on terrestrial and aquatic biodiversity
Vascular plant and bird diversity was sampled at 22 sites in a study of the effects of forest fragmentation in the FB and LT basins. Scott Pearson and Monica Turner focused on the diversity of species across the landscape in relation to land-use history. The impact of fragmentation on species diversity was quantified in the field as well as with a simulation model that incorporates both the landscape pattern and the life history of the organism. Model results suggested that species able to tolerate a high degree of habitat fragmentation had the highest survivorship probabilities. Bird diversity declined with forest patch size; however, patch size had no effect on plant species richness, although it did affect community composition. Smaller patches have a greater proportion of edge species and a smaller proportion of forest-interior species, although small patches still harbor some forest interior species (Figure 11). A spatially explicit model has been written to simulate population dynamics in landscapes with different fragmentation patterns and is being used to explore interactions between life-history strategies and landscape pattern (more).

We have also examined the effects of different land cover types on fish and aquatic invertebrate diversity and abundance and stream geomorphology in a series of 24 small vs. large streams draining either agricultural or forested watersheds in the FB and LT basins. The LT, agricultural watersheds have higher fish diversities and densities regardless of stream size. Agricultural sites are dominated by drift-feeding fishes, whereas a greater diversity of foraging types are represented in forested streams. Trout are found only in forested streams, and sites with large numbers of trout have low diversities and densities of other species. Adverse impacts of sediments on species composition are more apparent in FB than LT sites. Invertebrate density in the LT does not differ significantly among land-use types or stream size, although larger pasture streams appear to have fewer taxa. There are no significant differences in diversity indices, but there are fewer sensitive species (e.g. Plecoptera) in pasture streams .

As more detailed data of the land cover history of the area upstream of sample points has become available from GIS projects, additional analyses of the stream data have been possible. Recent results show that though significant differences exist in the species assemblages between primarily forested and agricultural drainage types, the history of the landscape may account for much of the difference between sites within each type of drainage.  For example, findings suggest that forest re-generation within a catchment may alleviate some negative effects of long-term agriculture, however recovery of the species to its structure before the disturbances may take decades (more).

In addition to quantifying the land-use change and population demographics of the region, Theodore Gragson (Co-PI and Anthropologist at the University of Georgia), has been brought on board to study and understand the motivations for and values of land use for populations of both people native to the Southern Appalachians as well as those that constitute the large influx of new permanent and seasonal residents of the Southern Appalachians. Rather than population growth and seasonal migration being strictly recent phenomena (from retiree and vacation home construction), they may be a repetition of a pattern set early in the population history of the Blue Ridge Mountains. A settlement history from 1790 to the present for the 42 counties in northern Georgia, western North Carolina, and southwestern Virginia comprising the cultural Blue Ridge has been developed from archival census records and other information. For more information on how this research has progressed please visit our current regional analyses on land cover change and socioeconomic drivers research.

To view all citations from past research web page, please see our past references page.

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