PARENT SESSION
Oral Session # 93: Vegetation Change and Response.
Presiding: B Parry Hecht
Friday, August 8. 8:30 AM to 12:00 PM, SITCC Meeting Room 105.
Multivariate analysis of ecosystem response to precipitation pulses.
Potts, Daniel*,1, Huxman, Travis1, Enquist, Brian1, Weltzin, Jake2, Williams, David3, 1 University of Arizona, Tucson, AZ2 University of Tennessee, Knoxville, TN3 University of Wyoming, Laramie, WY
ABSTRACT- We currently do not have a framework by which to evaluate how whole-ecosystems respond to environmental variation and perturbations either over short or long time scales. Here we assess and quantify complex system dynamics by utilizing multivariate techniques. During June 2002, we measured a suite of physiological and ecosystem measurements during 5 diurnal periods for two weeks following a simulated 25mm rainfall pulse for replicated plots of either native (Heteropogon contortus) or nonnative (Eragrostis lehmanniana) warm-season bunchgrasses on two distinct soil types. PCA of process variables reveals that independent of species or soil type, treatments followed a similar, nonlinear trajectory with measurement periods forming distinct clusters in multivariate space. PCA axis 1 and 2 combined to explain >70% of variation in treatments. We conclude that bunchgrass species and soil type has influence over the magnitude of ecosystem processes, but does not change the fundamental trajectory of ecosystem metabolism through time in response to a rainfall pulse. This multivariate approach provides a unique lens through which to view and characterize interactions between ecosystem properties and responses to short-term fluctuations in resource availability.
Key words: pulse, PCA, grassland