PARENT SESSION
Poster Session 20: Invasive Species
Wednesday, August 10, 5:00 PM - 6:30 PM, Exhibit Hall 220 A-E, Level 2, Palais des congrès de Montréal

Belowground communities respond to restoration strategies in Bromus tectorum-invaded ecosystems in the northern Great Basin.

DeCrappeo, Nicole^*,1, Pyke, David¹, ¹ U.S. Geological Survey, Corvallis, OR, USA

ABSTRACT- The invasion of Bromus tectorum (cheatgrass) into former Artemisia tridentata (big sagebrush) steppe ecosystems in the northern Great Basin has resulted in decreased plant species richness and structural diversity, drastic changes in litter inputs, modification of the rhizosphere, and alteration of soil moisture and temperature regimes. These relatively new soil conditions may have a measurable effect on the abundance, distribution, activity, and community structure of certain groups of soil organisms. Belowground organisms play vital roles in nutrient cycling, and any changes in their structure and functional diversity should be understood in the context of broader landscape-level dynamics. The aim of this study was to characterize changes in soil microbial and nematode community composition in conjunction with native plant restoration efforts underway in eastern Oregon, southern Idaho, northern Utah and northern Nevada. We sampled plots from low (200-250 mm) and high (250-300 mm) precipitation zones, half of which had been treated with sugar in fall 2003 and winter 2004. Subplots were hand-seeded using a factorial design of Bromus and native plant seed mixtures. Soil microbial communities were assessed using both BIOLOG substrate utilization ecoplates and phospholipid fatty acid analysis (PLFA). Nematodes were extracted using a density-dependent sugar-centrifugation method. Results from nonmetric multidimensional scaling (NMS) indicate that microbial and nematode communities subjected to sugar treatments were distinctly different on a two-dimensional scale. In addition, pairwise comparisons for Bromus versus native plant mixes indicated significant differences in nematode trophic group composition. These results may have important implications for the effects of annual invasive plants on soil communities and subsequent feedbacks loops and play a role in the success of restoration projects in arid rangelands.

Key words: Bromus tectorum, soil communities, rangeland restoration