A climatic driver for abrupt mid-Holocene vegetation dynamics and the hemlock decline in New England.
The mid-Holocene decline of eastern hemlock is widely viewed as the sole prehistorical example of an insect- or pathogen-mediated collapse of a North American tree species and has been extensively studied for insights into pest-host dynamics and the consequences to terrestrial and aquatic ecosystems of dominant-species removal. We report paleoecological evidence implicating climate as a major driver of this episode. Data drawn from sites across a gradient in hemlock abundance from dominant to absent demonstrate: a synchronous, dramatic decline in a contrasting taxon (oak); changes in lake sediments and aquatic taxa indicating low water levels; and one or more intervals of intense drought at regional to continental scales. These results, which accord well with emerging climate reconstructions, challenge the interpretation of a biotically driven hemlock decline and highlight the potential for climate change to generate major, abrupt dynamics in forest ecosystems.
Foster
David R
DR
Harvard Forest, Harvard University, 324 North Main Street, Petersham, Massachusetts 01366, USA. drfoster@fas.harvard.edu
Oswald
W Wyatt
WW
Faison
Edward K
EK
Doughty
Elaine D
ED
Hansen
Barbara C S
BC
D002980:Climate; D017753:Ecosystem; D019015:Geologic Sediments; D009511:New England; D028225:Tsuga / Q000502:physiology*