Validation of a methodological strategy for the qualitative evaluation of semiarid rangelands in Zacatecas

Rangeland degradation due to mismanagement practices in the extensive system for cattle and the need for monitoring rangelands continuously, leads to seek for methodologies which may be easily and quickly applied. In order to accomplish such objectives, methodologies must be based upon qualitative indicators. Such methodology has been applied broadly using 17 indicators that represent soil, water and vegetation attributes. This study was carried out in the State of Zacatecas and included 34 sites located randomly in the grassland with four repetitions by site. Data was analysed by principal components and a semivariogram and maps were generated by Kriging. Further, maps were compared to reference maps, which were calculated by quantitative methods. First map was associated to rangelands general health condition. The reference map was estimated from NDVI values. The second component refers to runoff, and the third component was associated to water erosion induced by bare soil. Those two were compared to reference maps estimated from mathematical models. Coincidences among maps were as 59.2, 31.2 y 17.2 %, which were the variance values estimated by principal components, and allowed to validate correspondence between them. Categorical data were not different (P>0.05). Low cost and easy methods are helpful and should be validated for use them when no other methods are available.