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University of Nevada Reno (2020)

Responses of Above- and Belowground Forb and Plant Species Diversity to Grazing Exclusion and Fire in the Northern Great Basin Sagebrush Steppe

Boldis, Mariel Tereza

Titre : Responses of Above- and Belowground Forb and Plant Species Diversity to Grazing Exclusion and Fire in the Northern Great Basin Sagebrush Steppe

Auteur : Boldis, Mariel Tereza

Université de soutenance : University of Nevada Reno

Grade : Master of Science in Animal and Rangeland Science 2020

Résumé partiel
The legacy effects of improper grazing regimes in the pre-1936 Taylor Grazing Act era and historical fire suppression have contributed to an overall decrease in native deep-rooted perennial bunch grasses and forbs, an increase in annual invasive grasses, and greater sagebrush dominance. Although not as widely used as perennial bunchgrasses, forbs of the Intermountain west have also been tested for use in rehabilitation purposes in the Intermountain West. Forbs provide the majority of plant species richness in stable-state sagebrush systems of the Northern Great Basin, are important seasonal food sources for wildlife like the Greater sage-grouse, provide erosion control through rapid establishment, and help prevent soil-nutrient loss. We assessed differences in above- and belowground diversity between burned and adjacent unburned areas, and between grazed and long-term grazing excluded areas, using soil seed bank and aboveground cover attributes in order to provide insight into ecological potentials of sagebrush sites in the northern Great Basin.Based on soil texture, elevation, species richness and composition of the seed bank in burned areas at each site, aboveground diversity (Effective S) increased as the seed bank became more diverse and was likely dominated by annual herbaceous species (except Claypan 14-16 #1). Below 1660-m in elevation (Loamy Slope 10-14), non-native annual grasses and forbs generally dominated the seed bank, suggesting that in the event of disturbance, aboveground cover may recover into a non-native annual herbaceous community. At sites between 1660—1970-m in elevation (Loamy 14-16, Gravelly North Slope 14-18, Claypan 14-16 #2, Claypan 10-14), annual herbaceous plants dominated the seed bank, and the composition of native forbs and native perennial grasses increased while the composition of non-native forbs and grasses decreased with increasing elevation (except at Claypan 14-16 #2), suggesting predicted aboveground diversity (Effective S) would generally have a native, mixed annual-perennial herbaceous plant community at higher elevations. Claypan 14-16 #2 did not follow this trend with 91% of total seed density in the burned area characterized as annual, composed mostly by cheatgrass and non-native forbs

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Page publiée le 22 novembre 2020