Site: Coweeta LTER

Though Coweeta became one of the first LTER sites in 1980, the Coweeta Hydrologic Laboratory as funded by the United States Forest Service has been in existence since 1934. Today the LTER and the Coweeta Hydrologic Laboratory coexist in the same complex of buildings and laboratories, collaborating and sharing data that now spans nearly eight decades. This data set has given Coweeta researchers unprecedented access to information about forest effects of both natural disturbances and human management.

In the 1930s, researchers selected several basins to study the effects of human management on forest hydrology. Researchers designated different watersheds to receive different treatments, such as clear cutting, clear cutting and replanting with pine, or conversion to agriculture, and continued to record data for many decades after treatment. Long-term study of this data has documented how the disturbance agent, gap size, and species-specific demography affect both recovery of the forest and hydrology in the long and short term. For example, researchers have found that on watersheds where hardwood vegetation was clearcut and watersheds converted from hardwoods to pine or hardwoods to grass that mean stream nitrate concentrations far exceeded measurements from control sites even 18-39 years after treatment.

Since these early experiments, the valley has continued to experience both natural and anthropogenic disturbance. The effects of disease, invasions of non natives, hurricanes, and droughts as well as different types of logging, agriculture, and increasing rates of exurban development have all been captured by the long-term vegetation plots first established in the 1930s. All of these have been effectively recorded in data that researchers can now analyze, with the help of models, to scale the effects of disturbance across temporal and spatial scales that remain invisible without the ability to incorporate such broad ranging data. New natural disturbances continue to occur on land monitored by Coweeta. The recent appearance of the Hemlock Wooly Adelgid in Macon County has been closely monitored by Coweeta scientists, and the combination of existing long-term plots and intensive short-term measurements will undoubtedly prove invaluable in anticipating and responding to the ecological impacts of this latest disturbance. Comprehensive climatic, hydrologic, and biogeochemical databases, made possible by the long-term nature of LTER funding and long-term measurements of vegetation dynamics, provide a template for understanding broader and more complex environmental issues. These environmental issues incorporate climate change, carbon cycling, and atmospheric deposition as they relate to effects on water resources and the productivity and health of forests.

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A graph showing long-term changes in species composition for unmanaged forest measured in 1934-1935, 1969-1973, and 1988-1993 within Coweeta, western North Carolina
Elliot and Vose 2011