Variation in carbon and nitrogen inputs and pools along an elevation, precipitation and vegetation gradient in southern Appalachian forests

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The role of forests in C sequestration is of global interest; and while recent progress in characterizing terrestrial C pools and fluxes at global scales has been made, challenges remain in characterizing how C pools and fluxes vary in time and space, particularly in landscapes with high variability in precipitation and temperature, vegetation diversity, and topography, such as southern Appalachian mountain forests.

In 1990 as part of the Coweeta Long-term Ecological Research (LTER) program, we established five large permanent plots across an elevation, precipitation, and vegetation gradient in southern Appalachian forests within Coweeta Hydrologic Laboratory, a US Forest Service Experimental Forest, in western North Carolina, USA.  The gradient forest communities include mixed oak-pine, mixed oak, cove hardwood and northern hardwoods; elevation ranges from 790 to 1390 m.  Annual precipitation ranges 210 to 268 cm and air temperature ranges 15.1 to 11.8 °C along the gradient.  We analyzed a 20-yr record of soil C and N; aboveground species composition, growth, biomass, and C stocks; coarse wood stocks; and leaf litterfall and fine wood C flux and changes over time with soil moisture, soil temperature, and vegetation community.  We expect to show that total C and N pool sizes are characteristic of vegetation, soil moisture availability and temperature regimes.  Additionally, that soil C and N pool sizes and accumulation rates are regulated by site variability in soil moisture and temperature as compared to inter-annual variability of aboveground C pools.