Soil carbon stocks can be negatively affected by land use and climate change in natural ecosystems of semi-arid environment of Iran

Soil is the largest organic carbon pool in the terrestrial biosphere, and a minor variation in the soil organic carbon (SOC) stock can substantially affect the global carbon cycle and climate. This study examined SOC storage considering land use and land use change across a semi-arid environment in northern Iran with a double aim: studying the effects of available soil parameters using a regression based modeling, and simulating the effect of the temporal variations of SOC under future climate change projections. In this regard, the following land covers were considered: forest cover, rangeland cover, conversion of forest to cropland, and conversion of rangeland to cropland. A stepwise regression analysis method was used to derive the relevant models of soil properties at of 0-10 and 10-20 cm depths. The results of regression modeling indicate that fungal abundance (for 0-10 cm soil depth) and the stoichiometry of microbial biomass nitrogen to total nitrogen (for 10-20 cm soil depth) are the most important factors for predicting SOC under the studied land covers. The effect of climate change on SOC stock differed among land uses. Simulated SOC stock decrease was in the range 5.14-11.95 Mg C ha-1 in forest, 4.48-10.37 Mg C ha-1 in rangeland, 9.34-15.38 Mg C ha-1 in cropland converted from forest and 8.00-13.72 Mg C ha-1 in cropland converted from rangeland. Therefore, conversion from natural ecosystems to cropland re-quires targeted intervention for a proper management of soils through a better residue management, the in-clusion of a cover crop to be used as green manure in rotation with wheat, minimum tillage intensity and addition of both mineral and organic fertilizers.