Effect of restricted-time grazing on desert grassland vegetation

To study the effects of restricted- time grazing on the height,coverage,density and biomass of desert grassland vegetation,forty male with similar body weight [( 15. 62 ± 0. 33) kg]and good body condition at four weeks of age,were randomly divided into four different restricted- time grazing groups( 2,4,8,and 12 h /d) of ten sheep each with access to pasture from June to September. The Tan sheep in the 2 h /d grazing group were supplemented with 300 g and 500 g of concentrates,daily for first 2 months and last 2 months,respectively; the Tan sheep in the 4 h /d and 8 h /d grazing groups were supplemented with 150 g and 300 g of concentrates,daily for first 2 months and last 2 months,respectively; while there was no supplemental feeding in the 12 h /d group. The results showed that the vegetation height,coverage,density and biomass of the grasslands showed a gradually decreasing trend with the increase of grazing time. The restricted- time grazing significantly affected( P 0. 05) the vegetation height of the grassland in the last two months after grazing,and the vegetation height of the grassland for grazing the sheep in the 2 h /d grazing group was significantly higher( P 0. 05) than that of the grassland for grazing the sheep in the 12 h /d grazing group; the vegetation height of the grassland for grazing the sheep in the 2 h /d grazing group was significantly higher( P 0. 05) than that of the grassland for grazing the sheep in the 12 h /d grazing group in the last one month after grazing; but there were no significant differences between the density and biomass of the grasslands. The results indicate that the restricted- time grazing for 2 ~ 8 h has less influence on the grassland vegetation,which is conducive to the growth of grassland vegetation and rational use of grassland resources.