Monitoring the spatial distribution of soil carbon sequestration for four decades based on changes in rangeland vegetation conditions (Case study: Noorrud watershed in Mazandaran province)

Carbon sequestration was monitored and predicted in rangeland ecosystems of Noorrud watershed. For this purpose, the land cover status of the years 1988, 1998, 2008 and 2018 were investigated on the basis of Landsat satellite images. Rangelands were segmented on the basisi of distinguished vegetation cover. Field sampling method was used for rangelands. For other land uses however, the default data of the International Climate Change Committee (IPCC) were used. Sampling points were marked on the maps and by designing a systematic-random sampling system, three 100m long transects were established on each already marked sampling area. Ten plots were put alongside of the each transect. In each plot, the percentage of vegetation cover and its biomass was estimated. To measure soil carbon at each sampling points, a soil profile was dug and soil samples were taken from a depth of 0 to 30 cm. samples dried in the open air and transported to the laboratory to determine carbon sequestration by walk-block method. By using the IDRISI Terrset software carbon sequestration measured based on ton per hectar and their distribution were mapped for each year. The results showed in the best rangelands S1 the land have decreased by 10374 hectares and in the poor ragelands S3 it have declined by 3.10253 hectares. On the otherside the lands classified as medium (S2) had an increasing trend (10758 hectares). Also, the amount of carbon in good, medium and poor rangelands is 111.45, 81.63 and 50.39 tons per hectare, respectively. The results also showed that carbon sequestration has been decreasing in the course of the study. So that its amount decreased from 9905729 tons in the whole area in 1988 to 8860803 tons in 2018. Meanwhile, the highest rate of decrease was related to the period 2008 to 2018 (562125 tons).