| The experiment analyzed the plant community and eco- physiological characteristics of main plant population under different stocking rates in Stipa breviflora desert steppe in Siziwang Banner of Inner Mongolia in order to compare their responses to the stocking rates. The main results were as follows: (1)There is no significant effect of grazing on distribution of plant community in a short period of time, evenness index ,richness index of plant community have no significant difference with the increase of stocking rate. (2)There were a close relationship between plant community and stocking rate, and net primary production of the plant species occurred equal- compensatory growth when the stocking rate was below1.213 sheep/hm2/year, while unde-compensatory growth has occurred above this value, so 1.027 sheep/hm2/year was the most suitable to this steppe (3)The differentiation rate of reproductive shoots of Artemisia frigida has decreased significantly with the increace of stocking rate ,asexual reproductive perdentage increased.(4)Activities of SOD,POD of Artemisia frigida, Stipa breviflora, Convolvulus ammannii, Cleistogenes songorica were increased in the heavier stocking rate sites. (5)Grazing press to the grassland was enhanced with the increase of stocking rate. At the same time, accumulation of malondialdehyde, proline of Artemisia frigida, Stip breviflora, Convolvulus ammannii were increased in heavier stocking rate sites. (6)Grazing has little effect on stored nutrition of plant root in a short period of time, and there was no regular changes of them with the increase of stocking rate.(7)The middle stocking rate site has the highest average Artemisia frigida, photosynthesis rate and easy to get a higher plant production.The most suitable stocking rate should be 0.918 sheep/hm2/year. |
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