Study On Sustainable Utilization Of Meadow Steppe At Edge Of South Mongolia Altiplano

The research was carried out at National Grassland Ecosystem Field Research Station in Hebeiprovince for two years from 2005 to 2006. The station located at the adge of south of Mongoliaaltiplano. The objective of the experiment is to research sustainable utilization of meadow steppe. Weset different sward height maintained in exclosure, and that is DO: no treatment; D1: 15 centimeter; D2:10 centimeter; D3:5 centimeter; D4:2 centimeter. From grassland growth capability, communitystructure, soil physical and chemical properties and physiology character to explore the successionorders of grassland degradation, and research the relationship between grassland utilization anddegradation, in order to provide some scientific basis for protecting and managing grassland in Bashangarea. Ecosystem balance and value in using should be considered for natural grassland sustainableutilization. The results indicate:1. The standing crop of community and L. chinensis decreased with the higher defoliation intensityand got the maximum at the middle of August. Growth biomass of community and L. chinensis had thesame change in treatments with one peak, and growth biomass of community in DO, D1, D2, D3 werenot significance, but D4 was least at P＜0.05 level. The differences of growth biomass of L. chinensis inDO, D1, D2 were not significance, which were higher than D3 and D4 at P＜0.05 level. Treatments hadthe similar changes in growth biomass and growth rate with dynamics as one peak. The response ofgrowth rate of community and L. chinensis to sward height maintained was the form of conic. Therelative growth rate of community and L. chinensis of different treatments had not significant difference.Based on the analysis on the relationship between growth rate and sward height maintained, there wasan optimum sward height of 15 centimeter.2. After two years' study, the results showed that there were significant effects of differentdefoliation intensity on vegetation quantitative characters. With increasing of defoliation intensity, thecommunity structure changed and L. chinensis as a dominant species became weaker. Important valueof some forages decreased, such as Stipa krylovii, Medicago ruthenica, but Artemisia and Cinquefoilincreased. The coverage of grassland decreased, but it can get 78.75％under D4 treatment. Communitypopulation changed slowly except D4 treatment. The species character index, including richness (S),diversity index (D and H'), eveness (J'), had similary trend and enhenced with the higher defoliationintensity. In the analysis of canopy structure index, LAI decreased and TD increased with the higherdefoliation intensity.3. The changes of soil physical characters were not significance in treantments. Organic matter ofsoil in D4 treatment was decreaser than the control in 0-10 centimeter soil layer at P＜0.05 level, butthere were no significance changes in 0-20 centimeter layer. Other soil chemical characters were notsignificance both 0-10 and 10-20 centimeter layers.4. The results showed that water-soluble carbohydrate in the leaves of L. chinensis had the seasonaldynamic changes. The effects of defoliation intensity on the water-soluble carbohydrate contents of leaves, the base stem and the rhizome of L. chinensis were significant at P＜0.05 level. Thewater-soluble carbohydrate of base stem increased with time passed in growing season and gotmaximum at the end of growing season. Changes of water-soluble carbohydrate content in the rhizomehad the similar trend with base stem of L. chinensis. Water-soluble carbohydrate contents of rhizomedecreased with the higher defoliation intensity in the same time. With the higher defoliation intensity,the length of rhizome, number of stem nodes, and number of buds and biomass of rhizome decreased.5. The results showed that there were seasonal dynamics as one peak for aboveground biomass ofcommunity and L. chinensis. The absolute growth rate and relative growth rate of L. chinensis werehigher at the initial growth stage than other stages. Dynamics of aboveground biomass of communityand L. chinensis accorded with logistic growth curve. In 2005, threshold value of community is 85.20gDM/m~2, and L. chinensis is 75.62g DM/m~2. In 2006, threshold value of community is 126.94 g DM/m~2,and L. chinensis is 103.56 g DM/m~2.