Impact of Vegetation Cover on Soil Carbon Storage and CO2 Fixation in Long-Term Land Uses in Bajestan

Land vegetation and soil degradation have considerable effects on greenhouse gas emissions resulting in global warming. Hence, this study aims to investigate the relationsip between soil organic carbon storage (SOCS) and different vegetation cover/ land uses in two soil depths (0-20 and 20-40 cm) in the Bajestan, Khorasan Razavi, Iran. A total of 122 soil samples (two depths× 61 soil sampling sites= 122 soil samples) were collected including orchard (pomegranate, pistachio and saffron), farmland (barley), desert (under and between haloxylon shrubs), and pasture. Results showed that surface layer of desert lands covered by haloxylon shrubs (3.17 Kg m-2) and both soil depths in pomegranate orchards (2.57 kg m-2 in 0-20 cm and 1.63 kg m-2 in 20-40 cm) had the highest SOCS content. Furthermore, it was found that soils under haloxylon shrubs accounted for 21.35% of surface SOCS as well as for 116.66 tons ha-1of absorbed CO2 in the soil and about 3.5 times more than areas located between haloxylon shrubs. Finally, the economic value of CO2 absorbed in the soil of studied land covers is 8193.45 and 3018.00-dollars ha-1 for surface and subsurface horizons, respectively. Comparing of soil organic carbon (SOC) content over 2004-2018 in the cultivated lands showed the increasing trend about 10.60 and 19.23 percent and in saffron and barley increased by 3.5 and 4.0 fold, respectively. Overall, sufficient information about SOC variation (positive or negative) with time can be effective in sustainable lands management, particularly in arid regions of the country to evaluate effects of different land use managements for increasing in SOCS process.