Changes in Soil Organic Carbon, Nitrogen and Phosphorus in Modified and Native Rangeland Communities (Case study: Sisab Rangelands, Bojnord)

Converting the native rangelands to simplified agronomic communities causes some changes in soil carbon, nitrogen and phosphorus. Establishing of perennial plantcommunities on formerly cultivated rangelands is expected to stabilize soil properties and increase the amount of C, N, P stored in rangeland soils, but there is little information on what plant communities are the most effective for improvement of soil C, N, P reserves. The purpose of this study was to compare soil C, N, and P pools in ungrazed native rangelandswith plant community of Festuca-Centurea with those ungrazed pastures established by sowing non-native perennial grasses (Agropyron elongatum and Agropyron desertorum), shrubs (Kochia prostrata), and wheat cultivation in continuous dry land farming system. Study site was located in Sisab Research Station in North Khorasan Province, Iran. The results showed that the total C, N and P contents in the soils under modified plant communities were less than that for native rangeland. Soils under A. elongatum, A. desertorum and K. prostrata tended to have higher values for total C, N and P than soils cultivated annually in wheat-fallow systems. The total C and N content of soils under K. prostrata were near as native rangeland which suggests that K. prostrata can increase the soil C and N contents much more rapidly than the other perennial communities.