Thursday, August 7, 2008
Exhibit Hall CD, Midwest Airlines Center
Lora Perkins, Natural Resource Management, South Dakota State University, Brookings, SD and Robert S. Nowak, Natural Resources and Environmental Science, University of Nevada Reno, Reno, NV
Background/Question/Methods Seeding target species for restoration of degraded areas of Great Basin rangeland has only produced minor success due to competition from Bromus tectorum (cheatgrass), harsh climate and variable precipitation. Target species may either be: 1) native grasses; or 2) select non-native grasses often used in restoration that are thought to compete well with cheatgrass. To provide information that may increase the success rate of restoration plans, this project examines the individual abilities of target plants to establish and maintain a stand in the field faced with cheatgrass competition. The target species used in this project were bluebunch wheatgrass (Pseudoroegneria spicata), Snake River wheatgrass (Elymus wawawaiensis), Sandberg bluegrass (Poa secunda), thickspike wheatgrass (Elymus lanceolatus), squirreltail (Elymus elymoides), crested wheatgrass (Agropyron cristatum), sterile wheat hybrids (Triticum aestivum x), and mountain wildrye (Elymus canadensis). Each species was drill seeded in 8 cheatgrass dominated sites over 4 states in the Great Basin. The experiment was repeated in 2 consecutive years. Plant density, aboveground biomass and reproduction were measured by species for two consecutive growing seasons at each site. Soil characteristics were measured at the beginning of the study. Climate variables were obtained for each site. Results/Conclusions
In order to elucidate the interactions among climate, soil characteristics, target plant performance, and cheatgrass competition, we constructed a Structural Equation Model (SEM). The variables included in the SEM were initial cheatgrass density, initial soil characteristics, precipitation, temperature, and a measure of both cheatgrass and native plant performance individually for both years. As expected, individual target species varied in their response to soil characteristics, climate, and cheatgrass competition. If target species can be selected for their ability to compete with cheatgrass on a site specific basis (considering soils, climate and precipitation), better seed mixes may be produced that increase restoration success.
