Grazing and Climate Effects on High Elevation Meadow Resources
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Authors
Richardson, William
Issue Date
2022
Type
Dissertation
Language
Keywords
grazing management , groundwater dependent ecosystems , insect abundance , Landsat , phenocam , sage-grouse
Alternative Title
Abstract
Semi-arid rangelands cover roughly 41% of the Earth’s land surface, and house more than 38% of the human global population. The Greater sage-grouse (Centrocercus urophasianus) has commonly been used as an umbrella species for restoration of sagebrush ecosystems in rangelands, due to its status as an indicator of overall rangeland health. Scarce mesic resources may lead to an energetic bottleneck for juvenile sage grouse, limiting fitness and survival rates. Mesic and ground-water dependent ecosystems found in the Great Basin of North America are heavily utilized by livestock and wildlife throughout the year. It is important for land managers to understand how intensity and timing of grazing affect the temporal availability of mesic commodities utilized by species like sage-grouse. This dissertation quantifies changes in the timing of availability of mesic sage-grouse resources across grazing and climatic gradients in high-elevation meadows. The methods include both on the ground and remotely sensed tools, and the correlations between them are assessed. The results suggest that field determined phenology, phenocam Green Chromatic Coordinate (GCC), Phenocam Normalized Difference Vegetation Index (NDVI), and Landsat NDVI are all highly correlated, with slight de-coupling occurring at the end of the growing season. Timing of growth varied in these ecosystems depending on yearly precipitation and vegetative type. Arthropod taxa abundance responded differently to grazing management and environmental variables in these meadow communities. Coleoptera abundance during peak sage-grouse usage periods had an increase of roughly 40% in some meadows with increased grazing intensity, while Formicidae abundance saw a 22% decrease. Near-surface cameras had varied success with predicting peak insect abundance levels. Sage grouse usage of the meadows was highly linked to growth seasons of vegetation, with slight decoupling occurring with growth seasons derived from phenocam GCC in drier years. Little correlation was seen between peak sage grouse usage of the meadows and peak capture rates of arthropods, this was true for all insect groups (Coleoptera, Formicidae, and Lepidoptera).