TRADITIONAL AND UPDATED EVALUATION OF THE RANGELAND SITE AND CONDITION IN THE SEMIARID SCRUB OF THE HIGH PLATEAU

In Mexico, the concepts of rangeland site and condition are not well known. For this reason, most of the rangelands of private ranches on the high plateau of San Luis Potosí and Zacatecas are undergoing a process of severe generalized deterioration. The purpose of this study was to survey and characterize multi-branched rangeland sites of three beef cattle ranches on the San Luis Potosí-Zacatecas High Plateau, as well as to assess their condition using a quantitative ecological method complemented by updated technological tools. The hypothesis proposed was that the site and condition of rangeland evaluated with the quantitative ecological method (used for grasslands and soil), complemented by updated technology, are also identifiable in multi-branched rangelands of this type of production units on the San Luis Potosí-Zacatecas High Plateau. Based on a Landsat satellite image, an unsupervised classification process was performed for the three ranches, which was then confirmed by field observations. A total of 11 sites were surveyed, three on each ranch (microphyll desert scrub, predominantly Bouteloua gracilis; microphyll desert scrub, with predominance of Sporobolus airoides; and an ecotone between microphyll desert scrub and rosetophile desert scrub) and two exclusive locations (crassicaule scrub and rosetophile desert scrub with predominance of Muhlenbergia villiflora). Rangeland condition was evaluated by measuring density and volume (volumetric biomass) of the main plant species, categorized by forage value, and the actual state of the soil surface was assessed in terms of bare soil and vegetation, litter, feces and rock cover. The data were ordered and classified with the DECORANA and TWINSPAN modules from the PC-ORD program. Site and condition evaluation under this approach was satisfactory for surveying the state of the rangelands of the three private cattle ranches studied on the San Luis Potosí-Zacatecas High Plateau.