Rangeland Evaluation in Fresno County,California based on Livestock Carrying Capacity Modeling using GIS

Research Projects

Rangeland Evaluation in Fresno County, California based on Livestock Carrying Capacity Modeling using GIS

PI: Tim Minor

Project Period: October 2000 - March 2002

Funded by: County of Fresno, California and Agricast, Inc.

Keywords: carrying capacity, multispectral imagery, GIS modeling

Project Description

DRI is supporting Agricast, Inc. with remote sensing/GIS expertise and analysis as it provides the County of Fresno, California, with a science based, defensible methodology for modeling the livestock carrying capacity of County rangeland. New methods of determining carrying capacity, integrating range science principles, satellite imagery, and GIS modeling, are being applied to more than 5600 square kilometers of rangeland contained within Fresno County. DRI has assisted Agricast, Inc. in the canopy classification of Landsat Thematic Mapper satellite imagery (see Figure 1), and is in the process of conducting all the necessary GIS data conversions and integration required to set up the carrying capacity model for the County. The carrying capacity model requires three input spatial variables: Canopy cover (broken down into multiple ranges, i.e. <25%; 25-50%; 50-75%; and >75%); Slope data, derived from a Digital Elevation Model (DEM) (see Figure 2), also broken down into ranges (<10%; 10-25%; 25-40%; >40%); and precipitation data (two annual categories across the County). All spatial data has been converted into raster (cell based) data with a common spatial resolution. Using a matrix model method that assigns livestock carrying capacity values to specific canopy cover ranges, slope values and precipitation ranges, the various data grids will be combined using ArcView GIS software tools to develop a single grid representing livestock carrying capacity on a cell by cell basis for the entire study area. Using the Assessor's parcel database provided by Fresno County as a selection data set, the number of animal units per acre per parcel will be calculated. These statistics will be used to more accurately determine the fair tax value of rangeland in Fresno County.

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