Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
6536782 | Agricultural and Forest Meteorology | 2018 | 14 Pages |
Abstract
Increasing air temperature is expected to extend growing season length in temperate, broadleaf forests, leading to potential increases in evapotranspiration and net carbon uptake. However, other key processes affecting water and carbon cycles are also highly temperature-dependent. Warmer temperatures may result in higher ecosystem carbon loss through respiration and higher potential evapotranspiration through increased atmospheric demand for water. Thus, the net effects of a warming planet are uncertain and highly dependent on local climate and vegetation. We analyzed five years of data from the Coweeta eddy covariance tower in the southern Appalachian Mountains of western North Carolina, USA, a highly productive region that has historically been underrepresented in flux observation networks. We examined how leaf phenology and climate affect water and carbon cycling in a mature forest in one of the wettest biomes in North America. Warm temperatures in early 2012 caused leaf-out to occur two weeks earlier than in cooler years and led to higher seasonal carbon uptake. However, these warmer temperatures also drove higher winter ecosystem respiration, offsetting much of the springtime carbon gain. Interannual variability in net carbon uptake was high (147 to 364â¯gâ¯Câ¯mâ2â¯yâ1), but unrelated to growing season length. Instead, years with warmer growing seasons had 10% higher respiration and sequestered â¼40% less carbon than cooler years. In contrast, annual evapotranspiration was relatively consistent among years (coefficient of variationâ¯=â¯4%) despite large differences in precipitation (17%, rangeâ¯=â¯800â¯mm). Transpiration by the evergreen understory likely helped to compensate for phenologically-driven differences in canopy transpiration. The increasing frequency of high summer temperatures is expected to have a greater effect on respiration than growing season length, reducing forest carbon storage.
Keywords
Related Topics
Physical Sciences and Engineering
Earth and Planetary Sciences
Atmospheric Science
Authors
A. Christopher Oishi, Chelcy F. Miniat, Kimberly A. Novick, Steven T. Brantley, James M. Vose, John T. Walker,