Ecosystem Fluxes in Great Basin Sagebrush and Post-Fire Communities

Project Number:

02R-03

Project Duration:

24 months

Dates:

May 1, 2002 to April 30, 2004

Institution of Principle Investigator while on this project:

University of Illinois

Investigators (most current known information)

DeLucia, Evan (PI)

Professor, Plant Biology, University of Illinois, 265 Morrill Hall, 505 S Goodwin Ave, Urbana IL 61801-3707

TEL: +1-217-333-3260, FAX: +1-217-244-7246, Email: evan@ux1.cso.uiuc.edu

Arnone III, John A.

Assistant Research Professor, Desert Research Institute, 2215 Raggio Parkway, Reno NV 89512

TEL: +1-775-673-7445, FAX: +1-775-673-7485, Email: jarnone@dri.edu

Yakir, Dan

Weizmann Institute of Science, Environmental Sciences and Energy Research, Rehovot 76100, ISRAEL

TEL: +972-8-934-2549, FAX: +972-8-934-4124, Email: ciyakir@wisemail.weizmann.ac.il

Proposal Abstract

Invasion of nonnative annuals across the American West is causing a widespread transition from perennial sagebrush communities to fire-prone annual grasslands. For over a century sagebrush ecosystems of the Great Basin Desert have been aggressively invaded by cheatgrass (Bromus tectorum L.), a winter annual native of Europe and Asia. Overgrazing of native bunchgrasses rendered this system vulnerable to invasion and once established, cheatgrass increases the frequency and intensity of fire thereby promoting its own growth. The diverse sagebrush ecosystem is becoming annual grassland dominated by a single species. Cheatgrass has become the dominant species in over 41 million hectares in the Great Basin. The objective of this research was to quantify the effect of cheatgrass invasion and establishment, as well as remediation practices, on carbon and water resources in the Great Basin Desert.

Our primary research goals were (1) to quantify how post-fire cheatgrass communities, cheatgrass/non-native bunchgrass mixtures, and native sagebrush communities differ in their net carbon exchange (NCE), evapotranspiration (ET) and soil moisture regimes at the ecosystem-level; and (2) to determine if these patterns lead to a redistribution of resources (water) in space and time. Our study included experiments to test the following detailed hypotheses and predictions.

Net carbon exchange and ET will be higher early in the spring in cheatgrass than sagebrush communities, with intermediate values in the bunchgrass/cheatgrass mixture. Establishment of nonnative grasses will alter the seasonal patterns of surfaces fluxes such that latent heat flux and ET will be also higher early in the spring in bunchgrass/cheatgrass than sagebrush communities.
Higher ET in spring and soil evaporation in early summer will cause a steeper decline in surface soil moisture in cheatgrass relative to the mixed grass and sagebrush communities. However, on an annual basis ET may not differ significantly among community types because sagebrush canopies remain active longer than grass canopies and because sagebrush may use deeper soil water.
Greater spatial variation in root density and aboveground biomass will contribute to higher spatial variation in surface soil moisture in sagebrush than in mixed grass or cheatgrass.