Winter vs. Growing Season Climate Effects on Tree Growth and Carbon Sequestration in a Northern Hardwood Forest
Abstract
Mean annual air temperatures for the northeastern U.S. are projected to increase 3 to 5 degrees Celsius over the next century, leading to warmer growing season temperatures, reduced snowpack, and increased frequency of soil freeze/thaw cycles in winter. Warmer soils have been shown to stimulate rates of net mineralization, nitrogen uptake, and carbon uptake by trees. However, wintertime soil freezing has been shown to damage tree roots, which impairs the ability of trees to take up nitrogen, water, and carbon early in the following growing season. Compared to our understanding of growing season effects on northern hardwood forests, we know little about the combined effects of changes in both growing season and winter climate, which are important to determine since they may be additive, synergistic, or cancel each other out. We conducted a multi-year experiment at Hubbard Brook Experimental Forest in New Hampshire to determine the combined effects of winter and growing season climate change on tree growth and carbon sequestration of a northern hardwood forest. We established six plots (11 X 14 m) in a red maple (Acer rubrum) dominated forest. Two plots are warmed 5 degrees Celsius throughout the growing season with buried heating cables. Two others are warmed 5 degrees Celsius in the growing season and have snow removed during winter to induce soil freeze/thaw cycles. Two additional plots are not treated and serve as references for the experiment. We measured rates of aboveground productivity using litterfall baskets and dendrometer bands over four years. We find that winter climate change through an increase in soil freeze/thaw cycles offsets the positive effects of growing season warming on aboveground growth and carbon sequestration of these forests. Together, these results demonstrate that winter climate change is likely to have strong impacts on the carbon cycling of terrestrial ecosystems, but the magnitude of these effects depend on whether they are offset by positive effects of warming during the growing season.
- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2018
- Bibcode:
- 2018AGUFM.B32A..08T
- Keywords:
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- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCESDE: 0470 Nutrients and nutrient cycling;
- BIOGEOSCIENCESDE: 0475 Permafrost;
- cryosphere;
- and high-latitude processes;
- BIOGEOSCIENCESDE: 1863 Snow and ice;
- HYDROLOGY