Get reliable rangeland science

Developers of Ecological Site Descriptions (ESD's) increasingly rely on moderate-scale ecoregion designations known as the Land Resource Unit (LRU) to resolve differences in vegetation communities (e.g. species composition, biomass production) that arise from localized climatic effects. Hierarchically, the LRU is nested within the Major Land Resource Area (MLRA) and specifies ranges for a specific climatic zone that can accommodate a suite of similar ESD's from a management perspective. The implications of LRU development can be monumental; if developed with robust criteria, LRU's may inform land owners, managers, and other interested entities in areas such as range management plans, wildlife habitat restoration, forestry, and recreation. The Sierra Nevada Foothills (MLRA 18) has been heavily utilized for a wide variety of resources over past centuries and today is recognized for its cultural resource hotspots, a gateway to several National Parks within the Sierra Nevada Mountains, and large expanses are dedicated to livestock production. Our study area, consisting of mostly privately owned landholdings, is centrally located within the Sierra Nevada Foothills MLRA and overlaps sections of two distinct zones identified in a previous ecoregion delineation project (EPA, Level IV). Our objective is to identify the main abiotic drivers of vegetation patterns across the two zones in order to improve an ongoing soil survey. Using EPA Ecoregion polygons as our spatial extent, we will employ vegetation cover data collected from 2009 to 2015 to evaluate soils, topographic, and climatic data. Specifically, we will use the vegan package in R to identify groupings of major vegetation communities based on environmental gradients. We will then use non-metric multidimensional scaling to compare the major groupings via dissimilarity indices. The results we present are specific to the Tuolumne-Calaveras County soil survey, but our techniques may apply to modeling LRU's of the entire MLRA.