Determining the thresholds of sustainable use of rangeland ecosystems by combining remote sensing techniques and meteorological indices (Case Study: the Karaj River Watershed)

Abstract Despite the need to determine the threshold of sustainable use of rangeland ecosystems, especially in drought conditions, no significant progress has been made in recent years, and still time-consuming and costly sampling of species production in a period of 5 to 10 years is used. In this study, to determine and monitor the threshold of sustainable use of rangeland ecosystem, the satellite index and meteorological drought index has been used, while the satellite index was determined by field measurement of canopy cover in a one-year period 2018-2019 in part of the basin of the Karaj river watershed. In this regard, In 3, 6, 9 and 12 month time steps, And the maximum satellite index (NDVI) during the growth period in the target years was determined over a period of 20 years. The results showed that there is a correlation coefficient of about 60% between satellite index and plant density, and in the normal years the satellite index has a correlation coefficient of is about 70% with the index of meteorological drought and 9-month cumulative rainfall leading to the period of maximum growth. Using the permitted harvest coefficients, the operating thresholds for the allowable range of the satellite index were determined and eventually the value of satellite index (NDVI) for the sustainable exploitation of the rangeland was proposed as (0.07459 ± 0.00908) and (0.1799±0.0194) for dry and wet years respectively, is recommended.