Abstract

Research based on Stipa bungeana community enclosing typical steppe zone in the Loess Plateau, and through different intensity-mowing disturbance test for 27 years, shows that higher species diversity and productivity are retained for grassland through moderate mowing, promotion of substance balance, starting cycle and providing an important basis for reasonable mowing and using the enclosed grassland. Due to the effects of rainfall and plant growth environment in mowing early days (1982 to 1987a), the species diversity of the grassland showed conk-increasing trend, and the species diversity showed significant changes under different intensity-mowing, and later -mowing (1988 to 2008a). The obtained results are as follows: mowing once every 2 year was 24.1±0.64 (species/m²); mowing once a year was 15.5±0.37 (species/m²), and mowing twice a year was 13.9±0.41 (species/m²). The biomass presented a parabola model in three mowing treatments, and average aboveground biomass in 27 years showed that: mowing once every 2 years was 785.6±111.84 (g/m²), mowing once a year was 630.8±115.1 (g/m²), and mowing twice a year was 501.5±120.53 (g/m²). The succession process of grassland community of three mowing disturbance had five phases: S. bungeana community reached the sub-climax at the iv succession phase with the abundant species number of plant community reaching 159; the shrubs and herbages of forest-steppe zone showed that the succession of typical steppe community tended to forest or bush steppe development. For the succession at the v period, S. bungeana as constructive species turned to mutation when the individual numbers of the community declined substantially and the clusters appeared to be a serious-death phenomenon. Stipa grandis community had the tendency that substituted for S. bungeana and became the constructive species. However, tiller capacity of the individual was poor, and the cluster small, and the coverage and biomass were low for S. grandis, so whether or not it reached the climax communities, succession growth needs to be observed further. The following results provide more scientific evidence for plant-soil system interactions and grassland management.

Key words: Plant-soil biosystem, typical steppe, Stipa bungeana community, mowing frequency, succession process, Loess Plateau.