关键词: 短花针茅草原, 放牧系统, 载畜率, 植物净生长量

Abstract: This experiment was conducted with 2 years old crossbred wether at Haya Teaching Ranch of Inner Mongolia Institute of Agriculture and Animal Husbandry where the natural rangeland is Stipa breuiflora desert steppe from 1996 to 1997. There are 5 grazing plots with different stocking rates and one ungrazing plot to be as control. The plant net productivity of all plots was measured in order to reveal the plant compensatory growth in the grazing system and test the grazing optimization hypothesis. The results showed that there was no significant difference(P>0.05) on the aboveground net productivity of sward between the grazing plots of 5 stocking rates and the ungrazing plot in 1996,which is called equal-compensatory growth of plant. In the dry year, 1997,when the stocking rate were below 2.0 sheep/half year/ha there was no significant difference (P>0.05) on the aboveground net productivity of the sward between grazing plots and ungrazing plot land when the stocking rate were over 2.0 sheep/half year/ha the aboveground net productivity of sward in the grazing plot was lower(P<0.05) than that in the ungrazing plot,which is called under-compensatory growth of plants. When stocking rates were 1.3 and 1. 5 sheep/half year/ha the aboveground net productivities of Artemisia frigida in the grazing plots were higher (P<0.05) than that in the ungrazing plot, which is called over-compensatory growth of plant. There was no significant difference(P>0.05) on the aboveground net productivities of Stipa breviflora, Jmpmus chinensis, Kochia prostrata, and forb, and on the underground(0~100 cm) standing crop of sward between grazing plots and ungrazing plot in 1996 and 1997.

Key words: Stipa breviflora desert steppe, Grazing system, Stocking rate, Plant net productivity