effects of grazing exclusion on plant productivity and carbon sequestration (case study: gomishan rangelands, golestan province, iran)

in recent years, rangelands have been regarded as potential carbon sinks. one of the most widely suggested options to sequester more c in rangelands is the restoration of the degraded rangelands through grazing the exclusion. in present study, the effects of exclusion on the carbon sequestration of gomishan rangelands were investigated. three transects were established in a key area inside and outside the exclosure. in each transect, ten plots were established systematically and in each plot, the number of plant individuals for each plant species was recorded and used to estimate the density of each species per unit area. in order to estimate the plant biomass, a few individuals of each species were sampled by the clipping and weighing method. the carbon content of aerial and root biomass were obtained by the combustion of 10 g of oven-dried samples. five soil samples at the depths of 0–10 and 10–20 cm were taken along each transect and then, transported to the laboratory. the soil organic carbon percent was determined by the walkley–black method. plant data analysis was performed by one way analysis of variance (anova) and tukey test. the rate of soil carbon sequestration inside and outside the exclosure was compared using the independent t test at significance level of 1%. finally, the economic benefit of sequestrated carbon was estimated. the results revealed that the response of plant and soil carbon storage to the exclosure in gomishan rangelands was positive and there was a significant difference between exclosure and grazing areas for the stored carbon of plant biomass and soil. after a 20 year exclosure, the value of carbon sequestration per hectare in gomishan rangelands was estimated as 14743 $/h. it can be argued that the education and extension of carbon sequestration in iran will offer new incentives to restore the degraded rangelands.