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Submitted to: Rangeland Ecology and Management
Publication Type: Peer Reviewed Journal Publication Acceptance Date: 2/28/2010 Publication Date: 3/18/2010 Citation: Boyd, C.S., and K.W. Daview. 2010. Shrub Microsite Influences Post-Fire Perennial Grass Establishment. Rangeland Ecology and Management. 63:248-252. Interpretive Summary: Woody plants can cause localized increases in resources (i.e. resource islands) that persist after fire and create a heterogeneous environment for restoration. We tested the hypothesis that burned subcanopies (formerly under shrubs, Artemisia tridentata ssp. wyomingensis Welsh) would have increased seeding establishment (density) and performance (height) of post-fire seeded perennial bunchgrasses compared to burned interspaces. Results indicated that one year post-seeding subcanopy microsites had dramatically higher seedling density and taller seedlings than interspace microsites and that seedling density was almost eight times higher for non-native as compared to native seedlings. Our data underscore the importance of shrub conservation for providing microsites with elevated chances of restoration success, particularly in low elevation sagebrush communities where establishing perennial grasses can help reduce susceptibility to invasion by exotic annual grasses Technical Abstract: Many arid and semi-arid systems benefit from restoration of perennial grasses following wildfire. Woody plants can cause localized increases in resources (i.e. resource islands) that can persist after fire and create a heterogeneous environment for restoration. We tested the hypothesis that burned subcanopies (formerly under shrubs, Artemisia tridentata ssp. wyomingensis Welsh) would have increased seeding establishment of post-fire seeded perennial bunchgrasses compared to burned interspaces. We used a randomized complete block design with five study sites located in southeast Oregon. The area was burned in a wildfire (2007) and re-seeded in the same year with a seed mix that included the non-native perennial grasses Agropyron cristatum (L.) and A. sibiricum ((Wild.) Beauv.) and native perennial grasses Psedoregneria spicata ((Pursh) A. Love) and Elymus wawawaiensis (J. Carlson & Barkworth). Seedling density and height were measured in October of 2008 in burned subcanopy and interspace microsites. Non-native perennial grasses had greater densities than native species (p < 0.001) and were six times more abundant in burned subcanopies compared to burned interspaces (p < 0.001). Density of natives in burned subcanopies was 24-fold higher than burned interspaces (p = 0.043). Seedling height did not vary between native and non-native perennial grasses (p = 0.989), but seedlings were taller in burned subcanopies compared to burned interspaces (p = 0.001). Our seedling density results suggest pre-burn shrub cover may be important to post-fire restoration of perennial grasses. The mechanism(s) contributing to increased seeding success in burned subcanopy microsites is unknown; however, other authors have found that subcanopies have increased soil organic matter, nitrogen and carbon (i.e. resource islands) and elevated post-fire soil temperature. These factors may contribute to increased post-burn heterogeneity of resources and spatially variable restoration success. Our data underscore the importance of shrub conservation, particularly in low elevation sagebrush communities where establishing perennial grasses can help reduce susceptibility to invasion by exotic annual grasses. |
