Long-Term Response of a Forest Watershed Ecosystem: Clearcutting in the Southern Appalachians
March 25, 2014
Otto, NC — A new book edited by U.S. Forest Service emeritus scientist Wayne Swank and Virginia Tech professor Jack Webster and published by Oxford University Press brings together findings from more than 30 years of collaborative research by the Forest Service and the National Science Foundation (NSF) Long Term Ecological Research (LTER) program on the Coweeta Experimental Forest (Coweeta) near Otto, North Carolina.
|Long-Term Response of a Forest Watershed Ecosystem: Clearcutting in the Southern Appalachians)|
The research centers on the long-term ecological responses of a southern Appalachian forested watershed following clearcut logging that took place in the 1970s. The 14 chapters by Forest Service and university scientists cover aspects that range from tree regrowth, to stream water quality, to effects on stream macroinvertebrates—each highlighting the importance of long-term data collection and research.
“We’re frequently asked, just what is long-term research in forested systems,” said Swank. “We consider the minimum window of investigation for forest ecosystems to include the lifespan of the forest of interest, which can easily include several generations of scientists. This book provides a comprehensive update on the long-term study of Coweeta Watershed 7, which so far spans nearly 40 years.”
In 1974, then Forest Service scientist Swank and colleagues at the University of Georgia proposed the research to NSF, which funded the study on nutrient cycling from a clearcut cable-logging study on Watershed 7 at Coweeta. The study was incorporated into the newly established NSF LTER program in 1980. The study was unique in that it answered both practical questions related to forest resource management in the southern Appalachians, as well as fundamental hypotheses about hydrologic and ecological processes that were driving the responses. Data and published findings from the study now stretch into decades.
Major findings covered in the book include:
- The pattern of initial response and early recovery of annual streamflow after clearcutting were consistent with other forest cutting experiments at Coweeta; however, in subsequent years, forest insects, diseases, and large shifts in species composition altered hydrologic responses.
- Following cutting, high rates of primary production and sequestration and storage of nutrients during early succession moderated loss of nutrients from the watershed. Later in succession, the death of black locust trees caused by stem borers contributed to elevated nitrogen loss from the watershed, which can limit productivity since nitrogen is essential to plant growth. Future long-term ecosystem responses to forest succession will be important.
- Two long-term Forest Service experimental forests (Hubbard Brook and Fernow) located in the Appalachian Highlands Physiographic Division provide important findings based on clearcutting experiments similar to those at Coweeta. The authors of these chapters compare the hydrologic and nutrient responses to Coweeta Watershed 7 and discuss factors contributing to similarities and differences between responses.
One of the novel features of the research is that it captures watershed responses over a large number of disturbances—not only logging, but also drought, record rainfall, hurricanes, insect outbreaks, and diseases. The research increased awareness about the effects of disturbance on forest ecosystems as well as the need to understand these processes at greater levels of complexity.
“Some forest processes simply cannot be forecast accurately with data from short-term studies,” said Swank. “For example, water quality and nutrient responses on Watershed 7 changed with every decade of data. Building models to forecast chemistry, nutrient, and carbon responses using data from the first 5 or 10 years would have given us different answers from what we actually observed in the long-term record. Watershed 7 continues to provide a rare opportunity for researchers.”
For more information, contact Wayne Swank at email@example.com.