Proxy soil temperature and moisture regimes (climate regimes) in southwestern U.S. drylands: 1980-1999 and 2000-2019

Spatially explicit and climate sensitive information on the responses of ecosystems to global change processes is required for strategic planning and prioritization of conservation and restoration. Indicators of ecological resilience and invasion resistance (R&R) are used increasingly to understand the influence of climate regimes on ecosystem responses to global change processes and determine effective management strategies. We developed proxy soil temperature and moisture regimes, or climate regimes, for southwestern U.S. drylands that accounted for precipitation seasonality and climate change at a scale of 1 kilometer (km). The climate variables that we used, mean annual temperature, precipitation, and monsoon index, allowed us to construct climate sensitive and ecologically meaningful climate regimes that mirrored the soil temperature and moisture regimes in the U.S. National Cooperative Soil Survey data and Ecological Site Descriptions that are widely used by managers in the western U.S. The climate regimes reflected the dominant ecological types and plant functional groups and allowed us to develop meaningful indicators of R&R. Particularly important was identification of a monsoon index value (0.30) to delineate areas with an ustic (summer moist) precipitation regime as indicated by the frequency of C4 vs. C3 grass species. This data publication provides climate regimes raster data (GeoTIFF format) that include four temperature regimes (cryic, frigid, mesic, and hypermesic), both ustic and xeric/aridic moisture regimes, and multiple moisture subclasses based on average precipitation zones (PZ). These climate regimes were used to develop two spatial data layers of the climate regimes for two consecutive time periods: 1980-1999, and 2000-2019.
Previous indicators of ecological resilience and resistance to invasion (R&R) focused on the sagebrush biome and relied on soil temperature and moisture regimes mapped as part of the U.S. National Cooperative Soil Survey or climate and water availability indicators derived from ecohydrological process models. However, proxy soil temperature and moisture regimes (climate regimes), and their associated R&R indicators, based on atmospheric climate variables are likely preferable to those based on soil climate because (1) soil temperature and moisture regimes from the Soil Survey are static and challenges exist in evaluating climate change effects based on these indicators, (2) discontinuities exist in soil map units across state boundaries, and (3) many areas, notably some U.S. National Forests, do not yet have published soil surveys. The finer-scale climate regimes and multiclass R&R indicators that we developed allowed us to account for precipitation seasonality and thus to provide more accurate information on the likely responses to disturbances and climate suitability to the widespread invasive annual, cheatgrass (Bromus tectorum), across the southwest drylands. We expect the climate regimes and R&R indicators will provide valuable information for strategic planning and prioritization and will be useful to develop prioritization strategies for fire prevention and management, invasive species management, conservation of species habitat, and to evaluate restoration success. These two spatial data layers represent climate regimes for two consecutive time periods: 1980-1999, and 2000-2019. The creation of two sets of climate regimes for different time periods allows comparison of climate-sensitive expected responses.
For more information about these data, see Chambers et al. (in review).