Effects of Livestock Grazing on Soil Carbon, Nitrogen and Microbial Biomass in some Reference Pastures of haharmahal Va Bakhtiyari Province

Document Type : Research Paper

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Abstract

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 18 years), Boroujen (grazing-protected for 23 years) and Sheida (grazing-protected for 2 years). Soil samples were collected from 0-15 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 (14.6 mg g-1) and the lowest (4.80 mg g-1) 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 (366%) 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. 

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References

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