Mechanism For Restoration And Regulatory Of Degraded Grassland Ecosystem In Yunwu Mountain

Grassland is the largest terrestrial ecosystem in China, and plays important ecologicalfunctions for biodiversity protection, water cycle, carbon sequestration and animal husbandrydevelopment. In the Loess Plateau of China, about63%terrestrial area covered with arid andsemi-arid ecosystem, which provide an important strategic position for ecologicalenvironment construction and economic development in northwest of China. Owing to globalclimate change and human activity disturbance, parts of grassland ecosystems of these aridand semi-arid areas have undergone degradation and dysfunction, biodiversity andproductivity lose, and these changes further influenced the ecological service function, andprevented regional social and economic development and ecological environment protection.It is an important scientific problem how to achieve sustainable development by combiningrestoration grassland ecological service function and rational utilization of grassland resources.In this paper, we selected the Yunwu Mountain National Grassland Nature Reserve asresearch objects. Using the monitoring data from1982to2012, we studied several keyscientific problems in restoration progress of degradation grassland. Based on the monitoringdata from different vegetation types and different stages grazing exclusion grassland, westudied the changes in vegetation, soil nutrients and soil microbial, and to discuss thecomprehensive management and regular technology of restoration grassland. Theoretical andexperimental research on grassland restoration is of great important for enriching the basictheory of grassland ecosystem, as well as guiding the restoration, reconstruction andcomprehensive management of grassland ecosystem.Combining the scientific experimental design and analysis technology, as well asapplying the field investigation and indoor analysis, we studied the mechanism for restorationand regulatory of degraded grassland ecosystem in Loess Plateau under the background ofglobal climate change, and we obtained the important conclusion as follows.(1) In semi-arid areas of annual rainfall400-450mm and annual mean air temperature7℃, for the aboveground biomass of grazing exclusion grassland, the≥0°C (annual)cumulative temperature and0-60cm soil water content as a significant variable was retained;and January-August precipitation as a significant variable was retained for abovegroundbiomass in grazing grassland. For soil moisture in the0-60cm soil layer, the main changeswere an initial increase in the early stages of restoration (from0to15years), followed by a gradual decrease from16to30years.(2) Based on analysis results of the monitoring data of30years, we obtained thefollowing results: the plant communities were composed of Poaceae, Fabaceae, andAsteraceae. Perennial species, C3plants, xerophytes and perennial bunchgrasses were themain indicators of the succession process and vegetation restoration. Therefore, we suggestthat Poaceae and Fabaceae should be selected first in process of Green for Grain Project inLoess Plateau. The “compensatory effects” of species and plant functional groups may beincreased the grassland stability. The ecosystem stability was in unstable status in the earlystages of restoration, followed by a gradual increase in the mid-and later stage of restoration.(3) Using the “space-for-time substitution” method, we studied the changes in soilnutrients, soil bacterial and eukaryotes communities for grazing exclusion grassland ofdifferent stage and different revegetation. The results of454Roche pyrosequencing showedthat for the grassland of different grazing exclusion stages, the diversity and abundant of soilbacterial communities reached the peak values in the15and9year grazing exclusiongrasslands, respectively. Comparison of the Shannon index of the different vegetation typesshowed that the highest bacterial diversity was found in korshinsk peashrub, followed byslope farmland, grazing exclusion grassland, alfalfa, grazing grassland and black locust. Thedominant phyla across all soil samples were Actinobacteria, Proteobacteria, Firmicutes,Acidobacteria, Gemmatimonadetes, Chloroflexi and Planctomycetes (the relativeabundances>5%). Soil eukaryotes mainly included fauna, fungi, and flora. At differenttaxonomic levels, comparison of the compostion and relative abundances of soil bacteria andeukaryotes showed differences among different sites. Plant species richness, abovegroundbiomass were the major influence factors of soil bacterial community diversity, indicated thatthe restoration soil bacteria and vegetation were synchronous.(4) Based on the grazing and mowing experimental data, we found that light grazing (2sheep ha-1, grazing periods per year were divided into three stages: June15to30; August15to30; October15to30) and mowing once every two years (July and September) wouldmaintain the highest diversity and productivity. In the management and restoration process ofgrassland in semiarid area, the mechanism of action productivity and diversity to stabilityshowed an “interactive model”. Rational management method of grassland (such grazing andmowing) could maintain and improve the ecosystem stability, and overgrazing decreased theecosystem stability.(5) In this study, we built the “Trinity of time threshold value method” for determiningthe best time threshold for management and utilization of restoration grassland. Andaccording to this method, we put forward that the best time threshold for management and utilization of restoration grassland is the15th in this study area. We recommend grazing andmowing could as management strategies and regulation technique for the restorationgrassland in the Loess Plateau, and the rational grazing intensity was2~3sheep ha-1(grazingperiods per year were divided into three stages: June15to30; August15to30; October15to30), and the rational mowing frequency was once every two years (July and September).