COS 5-1 - Effects of winter climate change on water and carbon dynamics in a northern hardwood forest

Monday, August 8, 2011: 1:30 PM
6A, Austin Convention Center
Pamela H. Templer, Department of Biology, Boston University, Boston, MA, Nathan Phillips, Earth and Environment, Boston University, Boston, MA and Mark Friedl, Earth and Environment, Boston University

Climate models predict winter warming in the northeastern United States of approximately 4 °C by the end of the 21st century and a 12-30% increase in winter precipitation, with a greater proportion falling as rain compared to what is currently observed. These changes in climate are expected to result in reduced depth and duration of the winter snowpack. In the absence of an insulating layer of snow, soils can freeze when air temperatures drop below freezing. In recent years, considerable progress has been made in our understanding of how soil microbial activity and nutrient cycling might respond to reduced snow cover and increased soil frost. However, the response of growing season plant dynamics to changes in the winter snowpack is less well understood. The objectives of this research were to determine the impacts of changes in the winter snowpack and increased soil frost on growing season plant dynamics such as sap production, water use efficiency and whole tree carbon gain. We conducted a snow-removal experiment in mixed stands of red maple (Acer rubrum) and red oak (Quercus rubra) at Harvard Forest in Petersham, MA. Snow was removed for the first 5 weeks of winter to mimic a later onset of the snowpack. Soil frost, snow water equivalent and soil temperature were measured throughout the winter, and soil temperature, soil moisture, and sap flow were measured throughout the growing season.


The results of the first year of our multi-year study suggest that a later accumulation of snow and greater depth and duration of soil frost impacts sap flow and canopy carbon exchange in these forests. Our results illustrate the importance of examining the impacts of changes in winter climate on plant dynamics during the growing season because there could be feedbacks to future climate.

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