Invasive Species Compendium

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Abstract

Assessment of rangeland ecosystem conditions in Grand Canyon-Parashant National Monument, Arizona.

Abstract

The objective of this report is to (1) increase our understanding of the underlying landscape, soil, and climate setting factors that affect Grand Canyon-Parashant National Monument dryland ecosystem structure and function (also referred to as land potential) and (2) characterize the condition of Grand Canyon-Parashant National Monument ecosystems in relation to management concepts, such as rangeland health. The results discussed here on ecosystem condition, coupled with the increased understanding of soil-geomorphic controls on vegetation distribution within Grand Canyon-Parashant National Monument, provide information to help managers develop appropriate livestock management strategies. Survey results document the high level of diversity within the study area, including 15 unique soil taxa (to great group level) and 271 species of plants. We collected three new plant species for Grand Canyon-Parashant National Monument and 17 new species for the NPS portion of Grand Canyon-Parashant National Monument. Results also document a strong association between rangeland health indicators and elevation, topographic setting, and soils. Soil factors found to explain important variation across plots include the amount of exposed bedrock, soil rockiness, soil texture (and associated hydrologic properties), and soil depth. We also found that dominant species turnover across elevation may represent species' differences in adaptation to climates, including Larrea tridentata, Coleogyne ramosissima, and Artemisia spp. Bromus rubens is the most common invasive species of concern recorded in this study, but other common invasive species are Bromus tectorum, Erodium cicutarium, and Schismus arabicus. Correlations between an index of cattle use and indicators of rangeland health suggest that areas with high cattle use have increased bare ground, decreased ground cover, increased frequency of Schismus arabicus, decreased cover of Coleogyne ramosissima and Ephedra spp., and increased cover of Gutierrezia spp. The few strong correlations observed between indicators of vascular plant community cover or abundance and indicators of cattle activity support rangeland assessment and monitoring strategies that do not rely solely on plant-based indicators are needed.