Abstract:

For the universal grassland degradation and associated human utilization in the world, authors expound ecosystem restoration, climate climax in ecological succession, environment change and grassland state transition, grazing and disturbance climax, restoration by human intervention, thereby put forward the restoration path and state model of the degraded grassland ecosystem. This paper emphasizes that the restoration of degraded grassland should be carried out from the perspective of ecosystem, rather than only vegetation or soil processes, because there will be multiple alternative restoration states for grasslands in the context of environmental change or human disturbance. Three basic restoration modes of degraded grassland and possible restoration states are described as the followings: (1) Gradual restoration according to natural succession: based on the theory of ecological succession, grasslands from light to moderate degradation under favorable environments might reach the climax or near climax state for a long time by the systematical self-organization. (2) Intervention restoration by human activity: for those severely or extremely degraded grasslands, it needs to break through a series of abiotic (soil structure, nutrients, etc.) and biotic (plant colonization, species interaction, etc.) restrictions, and restore to a certain equilibrium or stable state, even climax state by using engineering, physical, chemical or biological-ecological methods or practices. It will take a long-time. (3) Restoration by grazing disturbance: grassland ecosystem structure (species composition and diversity), productivity and nutrient processes could be regulated through light to moderate livestock grazing, thereby maintaining and promoting grassland ecosystem multifunctionality and stability. This restoration method can be selected for medium-mild degraded grasslands. In conclusion, the holistic goal of grassland restoration is to achieve its long-term stable ecosystem multifunctionality.

Key words: degraded grassland, ecological succession, livestock grazing, environmental variation, climate climax, disturbance climax