Relationship Between Productivity And Species Diversity Of Plant Community In Hulunber Grassland

Four main-transects, one sub-transect and one degraded transect were established as sampling sites in Hulunber grassland region for the current study. This research mainly include five sections: (1)the plant diversity and primary productivity of the main plant communities; (2)the diversity of community plant composition and the stability of plant communities; (3) the effects of climate change on the diversity and productivity of plant communities; (4) the effects of grazing disturbance on the diversity and productivity of community plant compositions; (5)the change of range conditions and the sustainable management of grassland. Main results and conclusions from the research were summarized as follows: 1. Temperature and water are the main ecological factors affecting species richness, diversity and primary productivity of plant communities in Hulunber grassland eco system. In the natural grassland communities, species richness, diversity and productivity are in accordance with the diversity—productivity relationship. In the regional scale, when all plant communities are included, the relationship of plant species richness with productivity conforms to single-peak mode. This relationship results from co-existing mechanism of community species and the interreactions of species, which is the selected result for fitness to the specific niche in an heterogeneous environmental condiotion. 2. Different functional groups have different contributions to the community aboveground biomass. Perennial bunch grasses, perennial rhizomatous grasses and forbs are main components of plant life form functional groups. The roles of functional groups of perennial bunch grasses and forbs change with plant zonal distribution obviously, for instance, with the moisture gradient decreasing, the relative biomass of perennial rhizomatous grasses increases and the relative biomass of perennial forbs decreases. Intermediate xerophytes is the main component in plant life form functional groups. In the regional scale, with the moisture condition decreasing. the relative biomass of mesophytes functional groups decreases and the relative biomass of xerophytes functional groups increases. 3. From population level to functional group level, and then to community level, the yearly-variation of aboveground biomass minimizes gradually and stability increases. The variability of dominant species is low at population level. At functional groups level, the variabilities of perennial bunch grasses, perennial rhizomatous grasses and forbs are also low in different plant life form functional groups. The variability of intermediate xerophytes is low at ecological type functional groups. At community level, the yearly coefficient variation of aboveground biomass is in the range of 13.16%～23.62%. 4. The effects of plant diversity on plant community stability result from compensated actions of different functional groups. In life form functional groups, the compensated actions mainly occur between perennial bunch grasses and perennial rhizomatous grasses, perennial bunch grasses and perennial forbs, perennial rhizomatous grasses and perennial forbs. In ecological type functional groups, the compensated actions mainly occur between xerophytes and intermediate xerophytes, intermediate mesophytes and intermediate xerophytes, and intermediate xerophytes and mesophytes. These kinds of compensated actions make the plant community stable in the ecosystem 5. In China, Hulunber grassland is a main region that becomes warmer. The average temperature of Stipa baicalensis meadow steppe increases 0.0487℃ per year. The average temperature of Leymus chinensis meadow steppe increases 0.0441℃per year. Precipitation increases, but increment is not dramatically. The warmer climate do not have obviously effects on the community compositions and community productivity of Stipa baicalensis meadow steppe and Leymus chinensis meadow steppe. Only Filifolium sibiricum, Serratura komarovii, Calium verum and Achnatherum sibiricum are sensitive to the climate change. With the annu...