اثرات چرای دام بر کربن، نیتروژن و زیست توده میکروبی خاک در برخی مراتع مرجع استان چهارمحال و بختیاری

Livestock grazing may directly and indirectly make changes in plant cover and soil properties, with a consequence for alterations in soil microbial activity, growth and biomass. The primary objective of this study was to assess the effects of pasture management (grazing and ungrazing) on soil N and C contents, and the amounts of microbial biomass C and N in the natural pastures ofChaharmahal Va Bakhtiyari province. Three managerial regimes including: a) long-term ungrazed, b) controlled grazed and c) free (over) grazed in close vicinity were selected at three sites including SabzKouh (grazing- protected for ۱۸ years), Boroujen (grazing-protected for ۲۳ years) and Sheida (grazing-protected for ۲ years). Soil samples were collected from ۰-۱۵ cm depth and organic C, total N and microbial biomass C and N were measured under standard conditions. Results showed that SabzKouh and Sheida sites had the highest (۱۴.۶ mg g-۱) and the lowest (۴.۸۰ mg g-۱) soil C stocks, respectively. Soil N and C contents at SabzKouh were significantly higher when compared to the other sites, probably due to more rainfall and humid climate. The amount of microbial biomass was significantly higher (۳۶۶%) in ungrazed than grazed soils at SabzKouh, while at  Sheida the light grazing pasture had a greater soil microbial biomass, and no change was found at Boroujen site. In brief, degraded pastures at SabzKouh and Boroujen seem to recover rather quickly from the long-term overgrazing with a proper management, while pasture ecosystems at Sheida site with cropping history need a much longer period for steady-state conditions and for improvements in soil quality and fertility after long-term soil degradation and disturbance.

Keywords:

ترسیب کربن , چرای مفرط , زیست توده میکروبی , کربن آلی , مدیریت مرتع , نیتروژن