Differences in inferred rangeland vegetation condition among satellite- and field-based estimates, before or after wildfire
Pre- and post-wildfire management is increasingly guided by fractional vegetation cover (FVC) products, that is, maps parameterized with satellite imagery, that are used to determine where, when and how vegetation can be managed to moderate ecosystem impacts of wildfire. Several recent FVC products have transformed the science and management of wildland fuels and fire by estimating the type and abundance of vegetation across continuous regional areas. Additional guidance can help inform how well FVC products are parameterized for such broad areas and how they can be applied to the smaller scales at which vegetation is most directly managed for wildfire. We asked how inference for pre- and post-wildfire management would differ between the most common FVC products and benchmark field data in four scenarios of sagebrush-steppe management in the Great Basin, USA. Case studies included herbicide treatments in California and Nevada, a livestock exclusion in Colorado, post-fire seeding in Utah and wildfire risk assessment in Idaho. FVC products included the U.S. Department of Agriculture Rangeland Analysis Platform (RAP) and the USGS Rangeland Condition Monitoring and Assessment Program (RCMAP), both 30 m pixel resolution. Agreement in vegetation change or variability between FVC products and field data, specifically the variability in vegetation cover attributable to treatments or wildfire risks, was modest and evident mainly in terms of directionality and not magnitude. We found weak support for the concept of greater agreement among data sources across larger sites, when differences in vegetation across time or space were larger, and when the abundance of the vegetation of interest was moderate. Practical implication . Conclusions about management conditions would differ meaningfully if based on the benchmark field data compared to FVC products and also between FVC products. When using FVC products for management, the management question can be matched to the limitations of the data source or multiple lines of evidence can be integrated together.