Long term records provide insights on the relative influence of climate and forest community structure on water yield in the southern Appalachians

2015 Spring Cyberseminar Series

Presenter(s):
Peter Caldwell / U.S. Forest Service Southern Research Station

Talk Description:

In forested watersheds, changes in climate and forest structure or age can affect water yield; yet few long-term observational records from such watersheds exist that allow an assessment of these impacts over time.  In this study, we used long-term (~80 yrs) observational records of climate and water yield in six reference watersheds at the Coweeta Hydrologic Laboratory in the southern Appalachian mountains of North Carolina to determine whether water yield has changed over time, and  examine and attribute the causal mechanisms of change.  These six reference watersheds are unmanaged with only successional dynamics and natural disturbances altering the forest structure since the 1920s. AutoRegressive, Integrated Moving-Average  (ARIMA) time series modeling revealed significant (p<0.05) increases in annual water yield (Q) from 1938 to the early 1970s and subsequent decreases in Q through 2013 for lower elevation watersheds.  Changes in precipitation (P) and potential evapotranspiration (PET) partially explained the changes in Q, but additional ARIMA modeling indicates that other factors contributed to the changes in observed Q. Forest species composition, stem diameter, and stem density data measured in long term permanent plot surveys suggest that there have been changes in forest structure, age, and species composition that could be the missing link in explaining the changes in Q. Our results could have significant implications for water supply in the region and may inform forest management strategies to mitigate climate change impacts on water resources, as well as emphasize the importance of maintaining long term monitoring networks.

CUAHSI's Spring 2015 Cyberseminar Series on  Evapotranspiration - Frontiers in measurement, modeling and management from the leaf to the landscape!

Hosted by Steven Brantley, Joseph W. Jones Ecological Research Center