Vegetation and Climate Change in Eastern North America Since the Last Glacial Maximum

Abstract

Response surfaces describing the empirical dependence of surface pollen percentages of 13 taxa on three standard climatic variables (mean July temperature, mean January temperature, and mean annual precipitation) in eastern North America were used to infer past climates from palynological data. Inferred climates at 3000—yr intervals from 18 000 years ago to the present, based on six taxa (spruce, birch, northern pines, oak, southern pines, and prairie forbs), were used to generate time series of simulated isopoll maps for these taxa and seven others (hickory, fir, beech, hemlock, elm, alder, and sedge). The simulations captured the essential features of the observed isopoll maps for both sets of taxa, including differences in migration patterns during the past 10 000 yr that have previously been attributed to differential migration lag. These results establish that the continental—scale vegetation patterns have responded to continuous changes in climate from the last glacial maximum to the present, with lags ≤ 1500 yr. The inferred climatic changes include seasonality changes consistent with orbitally controlled changes in insolation, and shifts in temperature and moisture gradients that are consistent with modelled climatic interactions of the insolation changes with the shrinking Laurentide ice sheet. These results pose new ecological questions about the processes by which vegetated landscapes approach dynamic equilibrium with their changing environment.

Plants and Temperature--CO 2 Uncoupling

“…ture increases at constant C02 (360 pmol mol-'). All Because and C02 at the Last C02 increase scenarios were started at C02 concentra-Glacial Maximum resulted in subtions of 360 ,,mol mol-l. stantial vegetation changes arising from altered plant carbon and water bal-photorespiratory carbon losses) than low ance (12), then the lower photosynthetic C02 alone, thus heightening plant susceptirates simulated under predicted Miocene bility to increased aridity. The effects of C02 concentrations of 260 pmol molt1 (2) temperature-C02 uncoupling on plant-car-(see the table) indicate that similar, or bon balance may also explain why Eocene even greater, changes to global vegetation rates of herbivory seem to have been highpatterns should have occurred.…”

The Changes in North American atmospheric circulation patterns indicated by wood cellulose

“…Such a change in the general circulation pattern would have been refl ected by changes in surface wind patterns, temperature, and moisture conditions in North America. Modeled changes in temperature and precipitation can be verifi ed with paleoclimate data, such as pollen or lake-level records Prentice et al, 1991;Webb et al, 1998). However, there are few reports on wind patterns (Sweeney et al, 2004).…”

Pleistocene Megafaunal Collapse, Novel Plant Communities, and Enhanced Fire Regimes in North America

“…The possibility that late-glacial vegetation and fire regimes were influenced by herbivory does not rule out climatic drivers of late Quaternary landscape change, which are well established (27,28). Rather, we suggest a hierarchy of controls on deglacial vegetation history, with climate driving changes in plant and megafaunal ranges and abundances, which engendered further herbivory-and fire-regulated biotic interactions.…”