Rocky Mountain Research Station

Title: Spatio-temporal heterogeneity and habitat invasibility in sagebrush steppe ecosystems

Author: Mazzola, Monica B.

Date: 2008

Source: Reno, NV: University of Nevada, Reno. 148 p. Dissertation.

Description: Bromus tectorum L. (cheatgrass) is the most widespread invasive weed in sagebrushsteppe ecosystems. Invasion by Bromus tectorum produces large-scale changes ecosystem that negatively affect seedling establishment processes. Establishment of invasive and native species plays a key role in determining community invasibility and restoration potential. This study examined factors influencing seedling establishment and survival of Bromus tectorum and native species in ecosystems characterized by different degrees of Bromus tectorum invasion. Temporal and spatial patters of resource availability were examined in native and invaded shrublands. The replacement of native herbaceous species by Bromus tectorum affected resource availability and seedling establishment patterns. Within the native community, invasibility appeared to increase with increasing resources and was controlled by microsite conditions, with interspaces dominated by native grasses resulting in the highest resistance to invasion. Within the invaded community, spatial differences were less important and it appeared that B. tectorum facilitated its own establishment. In Bromus tectorum-dominated grasslands, short-term reduction of soil resources negatively impacted Bromus tectorum, but effects were temporary and were not effective in controlling Bromus tectorum. Perennial species establishment was affected by increasing Bromus tectorum density and appeared to be restricted by seed availability. Results indicate that invasibility and restoration potential are determined by dynamic interactions between temporal and spatial variations in resource supply, competition and seed availability of both Bromus tectorum and perennial species.

Keywords: Bromus tectorum L., cheatgrass, heterogeneity, habitat invasibility, sagebrush steppe

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Citation

Mazzola, Monica B.  2008.  Spatio-temporal heterogeneity and habitat invasibility in sagebrush steppe ecosystems.   Reno, NV: University of Nevada, Reno. 148 p. Dissertation..