9623258 Harte Vegetation feedbacks to climate change: extending results from an ecosystem-warming experiment to landscape level. Predictions of global climate change are based on models that largely ignore climate-ecosystem interactions. Yet such interactions may potentially generate large positive or negative feedbacks to the climate. For example, shifts in vegetative cover will alter energy and water exchange with the atmosphere and could be a significant source of feedback To quantify such feedbacks, a detailed and mechanistic understanding of climate-ecosystem interactions on the scale of experimental plots is needed, along with reliable methods for generalizing knowledge obtained from ecosystem experimentation and natural climatic gradient analysis. This project will combine manipulations with elevational transect studies to 1) deepen understanding of mechanisms and contingent factors that shape climate-ecosystem feedbacks, and 2) evaluate and improve the use of transect and manipulation studies for extrapolating results about ecosystem response and feedback to the landscape scale. The focus will be on a shift in dominant vegetation from forbs to shrubs in subalpine meadow habitat in Colorado. This ecosystem response to climate variation has been observed over four years of an experimental simulation of climate warming. Correlations derived from monitoring vegetation and climatic variables along an elevational gradient will be compared with results from 1) the existing and continuing climate manipulation, 2) additional climate manipulations and reciprocal transplants along the gradient, and 3) interannual climatic variation within each data set.
