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Goal: Sustain Our Nation’s Forests and Grasslands Warmer temperatures reduce forest productivity but not water use

Director’s Choice
Technician calibrating equipment on top of a tower overlooking a forest

Field technician Chris Sobek calibrates a gas analyzer on top of a forest eddy flux tower at Coweeta Hydrologic Laboratory. (Forest Service photo by Christopher Oishi)


Warmer temperatures are expected to lengthen the growing season for forests. Longer growing seasons may also increase forest water use and productivity. However, other key processes affecting water and carbon cycles are also highly temperature-dependent.


The net effects of a warming planet are uncertain and highly dependent on local climate and vegetation. The Southern Appalachian Mountains of western North Carolina are one of the wettest biomes in North America and are home to highly productive forests. In these forests, warm temperatures in early 2012 caused leaf-out to occur two weeks earlier than in cooler years and led to higher seasonal productivity. However, these warmer temperatures also increased winter ecosystem respiration. This increase offset much of the springtime carbon gain. Years with warmer growing seasons had 10% higher respiration and sequestered about 40% less carbon than cooler years. In contrast, annual evapotranspiration was relatively consistent among years despite large differences in precipitation. The increasing frequency of high summer temperatures is expected to have a greater effect on respiration than growing season length, reducing forest carbon storage.

Principal Investigators
Christopher Oishi, Research Ecologist
Chelcy F. Miniat, Project Leader
Kimberly A. Novick
James M. Vose, Project Leader
4353 - Center for Forest Watershed Research
Strategic Program Area
Water, Air, and Soil
Warmer temperatures reduce net carbon uptake, but do not affect water use, in a mature southern Appalachian forest
CompassLive Story
Climate Drivers of Carbon Gain and Water Loss in a Southern Appalachian Forest
External Partners
School of Public and Environmental Affairs, Indiana University – Bloomington
Joseph W. Jones Ecological Research Center
U.S. Environmental Protection Agency, Office of Research and Development