اثر چرای دراز مدت بر پویایی کربن لاشبرگ در اکوسیستم مرتعی سبزکوه استان چهارمحال و بختیاری

Over-grazing may induce changes in the dynamics of plant residue carbon and soil organic carbon (SOC). The objective of this study was to evaluate the litter quality of three dominant pasture species, and the relationship between litter quality and C dynamics under different range managements in native rangelands of SabzKou. Aboveground litters from three dominant species including, Agropyron intermedium (AP), Hordeum bulbosum (HB) and Juncus stenophylla (JU) were collected in an area protected from grazing for 15 years. Concentrations of N, P and K in litter samples were determined. Litter decomposition was also studied by using a litter bag experiment. Bagged litters were incubated under field conditions at grazed and ungrazed sites for one year. Concentrations of N in litters were 1.37, 1.36 and 0.98, respectively, for AP, JU and HB. Assuming 50 % C in the litter, C/N ratios of litters were 37.2, 37.3 and 51.1, respectively, for AP, JU and HB. The litters of AP, JU and HB contained, respectively, 0.13,0.12 and 0.21 % of P, and 1.04, 1.01 and 1.72 % of K. Results indicate no significant (p>0.05) and consistent difference in litter decomposition rates between grazed and ungrazed areas. The three pasture species, however, showed significant (p<0.01) differences in litter decomposition rate. It is appearing that the trend in litter decomposition of these plant species correlates initially with litter C/N ratio, but other quality parameters of litter as well as soil environmental conditions would likely affect the litter decomposability in advanced stages of decomposition process.