FIELD INDICATORS OF SOIL CLIMATE CHANGE IN TRANS-PECOS, TEXAS, AND IMPLICATIONS FOR MANAGEMENT

A USDA-NRCS soil temperature study across southern Brewster and Presidio Counties, Texas, has expanded the range of the hyperthermic soil temperature regime to include approximately one million acres previously considered thermic. The majority of these hyperthermic soils fall within the aridic soil moisture regime, areas of minimal soil moisture commonly associated with desert shrubs. However, field indicators suggest that the hyperthermic soil temperature regime also impacts areas with slightly increased soil moisture typically associated with desert grasslands. These “hot desert grasslands” would represent soil climates that are transitional from hyperthermic to thermic soil temperature regimes within the aridic soil moisture regime and suggest an expansion of desert shrub landscapes into desert grassland landscapes due to increasing soil temperature. A combination of plant indicators such as leatherstem (Jatropha dioica), guayacan (Guaiacum angustifolium), Chino grama (Bouteloua ramosa), and others, as well as elevation, slope gradient and aspect were used to identify hyperthermic soils in areas with increased soil moisture. Management will need to adapt to climate change especially in the transitional zones.