Capabilities for rangelands state and degradation assessment using remote sensing data

The study aimed to investigate the relationships between remotely measured spectral characteristics and rangelands condition indicators acquired through ground-based geobotanical survey.The study was carried out in the Stavropol Region on 16 test sites located in the mixed grass steppes landscape.The MODIS (230 m) and Sentinel-2 (10 m) satellite instruments data were used for the study.A strong correlation between MODIS-derived NDVI and a rangelands degradation index values was established.The Spearman rank correlation coefficient of -0.67 was estimated for four different degrees of rangelands degradation and it grew up to -0.89 by combining two lowest rangelands degradation categories.Using the ground-based measurements by the GreenSeeker sensor it was found that the NDVI values of main grass species were quasi equal at the vegetation maximum development stage.It justifies the herbaceous cover development peak as most appropriate time interval for rangelands degradation assessment with remote sensing data.The weighted NDVI mean values derived from Sentinel-2 data demonstrated an increase in the rank correlation with rangelands degradation up to -0.80 and -0.95 in cases of four and three different categories of vegetation disturbances respectively.