Study On Restoration Succession And Health Evaluation Of Typical Steppe In Xilingol, Inner Mongolia

To disclose the variation law of health factors of typical steppe in restoring process, expand the content of grassland ecosystem health evaluation, promote the development of grassland ecosystem health evaluation, we chose typical steppe in Xinlingol League as research area, and selected the natural grassland which were exclosured in different years, including the sites exclosed in 2002 (exclosued for 6 to 7 years, F02) , exclosed in 1999 (exclosued for 9 to 10 years, F99) , exclosed in 1996 (exclosued for 12 to 13 years, F96) , exclosed in 1989 (exclosued for 19 to 20 years, F89) as research objects, at the same time, selected free grazing grassland as control (all treats set two times repeated), carried out the comparative research on vegetation and soil characteristics and analyzed the variation law of health factors of typical steppe in restoring process. Based on this, we constructed the index systems of grassland ecosystem health evaluation, elected the sensitive indices of typical steppe health evaluation, and evaluated the health status and the service value of typical steppe in different exclosure period. The main results are as follows:(1) The degraded typical steppe developed positively, the production, coverage, density, under-ground biomass and litter biomass of the grassland increased and the structure of community optimized after the utilization of seasonal exclosure. Along with the prolonging of exclosure period, the production, coverage, density, under-ground biomass and litter biomass increased significantly, but if hay production was developed continuously for many years, and then the grassland might appear the second retrogressive succession, so the production, coverage, density, under-ground biomass and litter biomass of the grassland decreased again after exclosed for 19 to 20 years.(2)After the utilization of seasonal exclosure, the proportion of coarse sand (2.00～0.25 mm) dropped significantly, and the proportion of fine sand (0.25～0.05mm) and silt and clay (<0.05mm) increased significantly, soil bulk density and compaction dropped, soil porosity, nutrient and microbe quantity increased, soil microbial biomass and enzyme activity enhanced in the layer of 0～10cm and 10～20cm.And soil porosity, nutrient, microbe quantity, microbial biomass and enzyme activity showed the trend of rise along with the increase of exclosure period, and after exclosed for 12 year, the quality of the soil reached to the best. But the soil quality descended again after enclosed for 19 year because of the mowing utilization for many years.(3)Started with the ecosystem structure and function, constructed the index system of grassland ecosystem health evaluation. And selected eight quantitative and two qualitative indices, including the production, community coverage, litter biomass, excellent forage proportion, forage crude protein, soil compaction, soil organic matter, soil microbial biomass nitrogen and dominance species and life form synusia composition, as the sensitive indices of typical steppe health evaluation.(4)The health condition of typical steppe in different exclosure period was evaluated by grey correlation analysis, fuzzy comprehensive evaluation, VOR index and CVOR index, the result showed that all of the methods used above could be used to evaluate the health condition of typical steppe. In addition, the result showed that the health condition rose after the utilization of seasonal exclosure. In free grazing land, the health condition decreased to"threshold"because of continuous heavy grazing, after the utilization of seasonal exclosure, the health condition was significantly increased. So the health condition of typical steppe increased to"sub-health"after exclosued for 6～10 year, and then increased to"health"condition after exclosued for 12～13 year. But the health condition of typical steppe descended to"sub-health"again after exclosued for 19～20 years, analyzing the reason was continuous mowing for many years.(5)After the utilization of seasonal exclosure, the service value of typical steppe was significantly increased. Compared with free grazing land, the total value of service function of typical steppe was increased by 17.64%, 29.11%, 53.62% and 39.87% respectively after exclosing for 6～7, 9～10, 12～13 and 19～20 years. Showed that seasonal exclosure was the effective method for maintaining the service value of grassland ecosystem and realizing the sustainable development of grassland animal husbandry.