Effects of Land Use Changes on Soil Organic C Pools in Marginal Lands of Zerebar Lake

Organic carbon pools and carbon lability directly affect soil biological، physical and chemical characteristics. Besides، capacity of self-organization of soil is related to the organic carbon pools. Sand size fraction (> 50 µm) organic matter is more labile than silt+clay size fraction organic matter. Assessment of this organic carbon variation can be a suitable index to determine soil quality. The aim of present study was to evaluate the impact of land use change on particle size fractions of organic carbon and carbon pool index. In September 2010، soil samples were collected from the three major land use types including wetlands around the lake، wetlands converted to wheat، and alfalfa cultivations. Soil samples were collected from the 0-30، 30-60 and 60-90-cm depths in each of land use. According to the results of particle size fractionation of organic carbon in 0-30-cm layer، the highest and lowest amounts of sand size fraction organic carbon were obtained in wetland (67. 01 g. C. kg-1soil) and wheat land use (24. 57 g. C. kg-1soil)، respectively. Land use change from wetland to alfalfa and wheat caused a decrease of silt+clay size fraction organic carbon in 0-30-cm by 48. 39 and 45. 14 t. C. h-1، respectively. In the 30-60-cm layer of cultivated land، soil organic carbon storage in silt+clay size particle was more than sand size fraction organic carbon. Results showed that carbon pool index in alfalfa، and wheat land was decreased by 50 and 60% compared to wetland، respectively. And carbon management index in alfalfa and wheat was declined by 44. 90% and 66. 70%، respectively.