The Use of NDVI for the Analysis of the Effect of Drought on Vegetation Productivity in the Pre-Urals Steppe Area Where a Population of the Przewalski Horse Equus Ferus Przewalskii Polj., 1881 Had Been Established

Abstract

The comparison of seasonal dynamics of NDVI between years 2016 of normal-average rainfall and drought-affected 2010 was carried out in the Pre-Urals Steppe area (Orenburg State Nature Reserve, Russia), where a semi-free population of the Przewalski horse had been established. Landsat 7, 8 and Sentinel 2 satellite images were used to calculate NDVI. Vegetation productivity in 63 model-scientific plots were studied in between June 18 and 30, 2016 during the period of maximum development of the vegetation; NDVI for the plots were calculated too. The data were used to build a linear predictive model on the correlation between NDVI and vegetation productivity. Such modelling might prove effective in an estimation of pasture forage resources and the prediction of its changes in dry years. According to the model the extreme drought in 2010 resulted in a 60% decrease in vegetation productivity during the period of maximum development of the vegetation. After a severe drought the drop in winter forage resources may be much more drastic. Yet, a study of the depth and spatial distribution of snow cover is necessary for accurate predictions of a supply of pasture forage for the population of the Przewalski horses.