Grazing Effect On Vegetation And Soil In Stipa Breviflora Steppe And Rough Fescue Grassland

The experiments were conducted to investigate the changes of vegetatiton and soil in Stipa breviflora steppe in Inner Mongolia and Rough Fescue grassland in Alberta of Canada.The purpose of this study was to investigate the relationships among vegetation, livestock and soil to obtain sustainable livestock production and prevent the grassland further degradation.One experiment was conducted at three sites (replicates) in Siziwang Banner in Inner Mongolia with four treatments defined along an historic grazing gradient: ungrazed (Control), lightly grazed (LG), moderately grazed (MG) and heavily grazed (HG). The grazing treatments were classified based on species composition and ground cover. Another one was conducted on the Rough Fescue (Festuca campestris (Rydb.) grassland near Stavely, Alberta on the site of a long-term stocking-rate experiment established in 1949. Three grazing treatments were selected: Moderate grazing (MG), heavy grazing (HG), and a non-grazed exclosure (control) that were stocked at 12, 24, and 0 SM·ha-1, respectively. The vegetation and soil properties were assessed in fall 2005 in Stipa breviflora steppe and monthly from May to September 2007 in Rough Fescue grassland, respectively. This study investigates the effect of grazing on herbage production, herbage nutrients and mineral concentrations and soil nutrients, soluble ions, soil pH, and soil electricity conductivity both in Stipa breviflora steppe and Rough Fescue grassland, at the same time we studied the chanes of nitrogen and phosphorus concentrations in cow tail hair in Rough Fescue grassland.The vegetation coverage, net primary production (NPP) and litter in Stipa breviflora steppe decreased with grazing intensity (p>0.05), and species richness and Shannon-Winner index also decresed (p>0.05). While in Rough Fescue grassland, species richness and Shannon-Winner had the same trends with Stipa breviflora steppe, however, NPP increased but litter yield decreased (p<0.05) with grazing. The vegetation total N (TN) and P (TP) concentrations andδ¹⁵N level in Stipa breviflora steppe were not affected (p>0.05) by grazing.While TN and TP concentrations of vegetation in Rough Fescue grasssland were higher in grazing treatments than control (p<0.05). Which indicated the grazing accelerated nutrients cycles and it was reflected fromδ¹⁵N level of vegetation. Grazing increased soil bulk density by increaseing soil compaction. Soil TN and TP concentrations were affected by graizng. However, this effect in Stipa breviflora steppe were not significant, only had a decrease trend (p>0.05). Soil TN and TP concetrations in Rough Fescue grassland were affected by grazing (p<0.05) and they were higher in the control than in grazing tretments.δ¹⁵N level in Stipa breviflora steppe incresed with grazing intensity (p<0.05) while there had no consistant trend in Rough Fescue grassland. Soil organic carbon (OC) was affected by grazing but not singnificant in Stipa breviflora steppe, HG resulted in 16.4 reductions in soil OC. Grazing significantly affected soil OC (0-15cm) in Rough Fescue grassland, and it was lower in the MG and HG treatments than in the control (p<0.05). Grazing had no effect (p>0.05) on soil available P, available N (NO3- and NH4+), electrical conductivity, pH and soluble ion (Na⁺, Ca²⁺, Mg²⁺ and SO₄^2-) levels both in Stipa breviflora steppe and Rough Fescue grassland. Soil pH and soluble K⁺ at all depths (0-60cm) was higher (p<0.05) in grazing treatments than control, while Cl^- was higher (P <0.05) in the control than in the MG and HG treatments. And soil C, N, P and soluble ions significantly (P <0.05) decreased with soil depth.δ¹⁵N level in the cow tail hair decreased significanly with increased grazing intensity (p<0.05).