Regional scaling of soil moisture dynamics on the semiarid grasslands of Mexico through remotely sensed vegetation indices

Soil moisture dynamics for both native (Bouteloa gracilis) and introduced (Eragrostis curvula) species within the semiarid grasslands in Mexico are analyzed. The semiarid grasslands of Mexico are part of the shortgrass steppe ecosystem, which extends from the North American midwest in the north to Llanos de Ojuelos in the south, where the study site is located. Soil moisture dynamics are measured on two homogeneous fields; one dominated by the native species (Bouteloa gracilis), and another with an introduced species (Eragrostis curvula) at three different depths with high temporal resolution along with standard climatological data. These data are related to measured Leaf Area Index (LAI) and spectra at 16 different wavelengths, both of which, in turn, are related to remotely sensed imagery through different vegetation indices (NDVI, SAVI, EVI and Modified Chlorophyll Absorption Ratio Index (MCARI)) for different sensors (LANDSAT, SPOT, Pleiades) at different growth stages. To date, the MCARI exhibits a larger correlation with LAI for all sensors and growing stages for both grass species (ongoing field work will provide additional data). Regionalization of soil moisture dynamics (i.e. recharge) will be done using a numerical model of the vadose zone that will be linked to the temporal variation of MCARI. Financial support by the Mexico's CONACYT (project CB 158370) and UNAM's PAPIIT program (project IA100613) is acknowledged.