The cattle industry in Chihuahua, Mexico is one of the most important economic activities in the State and relies mostly on native grasslands. These ecosystems present several problems: overgrazing, land use change and especially climate variability. These problems have been evaluated in the past with traditional methodologies. Recently, the use of remote sensing has yielded reliable estimations of biomass production in different geographical areas and times of the year. Images from different sensors can be calibrated with radiometric data measured on the field. This study developed a model of biomass production in the grasslands of Chihuahua State based on the integration of radiometry data and MODIS images. Data from 103, 117 and 107 sampling stations (each one including four subsamples) were collected from October 2011, 2012 and 2013, respectively. Values of NDVI from the images were validated against values of NDVI from radiometry data using linear regression. Values for 2011 was R2=0.69, for 2012, R2=0.75, and for 2013 was R2= 0.69. Then, values from radiometry were correlated to biomass production, giving a R2 of 0.52, 0.55, and 0.41 for 2011, 2012 and 2013, respectively. The models generated for biomass were scaled to the MODIS images. The calculated production was 34.23 kg/ha, 80.23 kg/ha and 110.14 kg/ha for 2011, 2012 and 2013, respectively. Low values of biomass production obtained are a result of two consecutive dry years, where 2011 was historically the driest year in the last 50 years. Even though the 2013 precipitation was above the annual average, biomass production for this year was still low. Years with severe droughts may affect biomass production for longer periods. The methodology implemented in this study will be useful for monitoring large grassland areas subjected to drought.
Oral presentation and poster titles, abstracts, and authors from the Society for Range Management (SRM) Annual Meetings and Tradeshows, from 2013 forward.