PARENT SESSION
Oral Session 8: Forest Ecology I: Dynamics and Succession.
Presiding: A Fiala and D Kashian
Monday, August 2, 8:00 AM to 11:30 AM, Meeting Room B 117.
Soil warming hastens successional dynamics in a temperate forest ecosystem.
MOHAN, JACQUELINE*,1, BAZZAZ, FAKHRI1, BURROWS, ELIZABETH2, LUX, HEIDI2, MELILLO, JERRY2, 1 Harvard University, Cambridge, MA, USA2 The Ecosystems Center, Marine Biological Laboratory, Woods Hole, MA, USA
ABSTRACT- Extratropical forests of the Northern Hemisphere are currently important sinks for atmospheric carbon dioxide (CO2), largely due to forest regrowth on abandoned agricultural land. At Harvard Forest we tested the hypotheses that soil warming could affect forest regeneration dynamics by preferentially benefiting either highly-productive or slow-growing understory tree species - potentially altering rates of forest succession with accompanying implications for future net ecosystem productivity (NEP). Using data on pre-treatment and post-treatment growth of 11 tree species, we found that a 5 oC increase in soil temperature caused a 50% enhancement in understory productivity (p<0.0001). The magnitude of the heating effect was negatively correlated with intrinsic growth rate, so that warming preferentially benefited slower-growing taxa. Of the six species that exhibited significant growth enhancements from warming, five were the slowest growing taxa under control conditions: Fraxinus americana (p=0.01), Tsuga canadensis (p=0.005), Quercus velutina (p=0.01), Acer saccharum (p=0.001), and Prunus serotina (p=0.07). The sixth species, Acer rubrum, had intrinsically rapid growth under control conditions but additionally grew faster with soil warming (p=0.003). In contrast, fast-growing species like Betula alleghaniensis, B. lenta, and Acer pennsylvanicum exhibited negligible responses to warming. These results may partially explain the large contemporary increase in A. rubrum abundance, and suggest that future forests may cycle more rapidly through successional development. Long-term carbon uptake by forests may be less than suggested by current estimates based on highly-productive aggrading stands, and projections of biotic feedbacks to the global carbon cycle may require revision.
Key words: global change, forest succession, global warming, ecosystem ecology