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Boise State University (2021)

Effects of Habitat Disturbances on Reptiles in Sagebrush Steppe

Parker, Kristina Joan

Titre : Effects of Habitat Disturbances on Reptiles in Sagebrush Steppe

Auteur : Parker, Kristina Joan

Université de soutenance : Boise State University

Grade : Master of Science (MS) in Biology 2021

Résumé partiel
Reptiles inhabiting shrub-steppe ecosystems of the Intermountain West have adapted to harsh, unpredictable desert conditions, yet recent changes in disturbance regimes may put species at risk. In southwest Idaho, cheatgrass (Bromus tectorum) has altered the fire regime resulting in a vast conversion of shrub-steppe to mostly annual grasslands that burn too frequently to allow shrublands to recover. Southwest Idaho has the highest reptile diversity in the Pacific Northwest, yet we know little about reptile community dynamics in response to the cheatgrass-fire cycle. We hypothesized that wildfires and cheatgrass negatively affect reptile communities directly (i.e., mortality during fires) and indirectly through changes in the quality of reptile habitats at multiple spatial scales. We used trapping and visual encounter survey data to quantify the effect of previous wildfires, cheatgrass, and other habitat metrics on reptile richness, diversity, occupancy, and abundance at local (i.e., trapping array) and landscape levels. We found that vegetation cover, distance to a rock outcrop, and wildfire frequency were essential predictors c reptile abundance at both spatial scales. We found that many reptile species were not affected by cheatgrass cover but were affected by wildfire frequency. Lizard richness decreased with the number of times an area immediately around a trapping array burned. Our models indicated that occupancy for many reptile species declined in areas that burned, especially in areas with repeated burns at the local level. We found that only gophersnake abundance was significantly negatively affected by wildfire at the local level. Our research contributes to the growing body of evidence that the cheatgrass-fire cycle in the western U.S. negatively impacts many species, including reptiles. However, the effect on communities is nuanced, with winners and losers depending on a combination of habitat associations, life history, and environmental sensitivities.

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Page publiée le 12 décembre 2022