Fluctuating Forests

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Science  04 May 2012:
Vol. 336, Issue 6081, pp. 521
DOI: 10.1126/science.336.6081.521-c

In the current era of rapidly changing climate, the past can provide useful lessons about the responses of ecological communities to climate fluctuations. Increased or repeated drought is a plausible scenario in some currently humid environments under climate change, although where and when this might occur is still hard to predict. The kinds of ecological change that might be expected, however, are illustrated in a study of historical ecological change in the humid western Great Lakes area of North America in response to the Medieval Climate Anomaly (MCA). The MCA began approximately 1050 years ago, lasted for 450 years, and was characterized by a warmer climate in north temperate regions and a series of droughts in the Great Lakes region. Booth et al. used pollen analyses and subfossil testate amoebae (which are sensitive indicators of water table depth in peatlands) to trace the population changes in drought-sensitive beech trees during this period. They show that beech declined in abundance sharply wherever drought and increased moisture fluctuations occurred, with associated effects on fire incidence and other components of the ecological community. These findings illustrate how currently moist regions could experience rapid ecological change as a result of increased climatic fluctuations in a warming world.

Ecology 93, 219 (2012).

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