Effects Of Grazing On The Relationships Between Plant Diversity And Community Stability On Meadow Steppe

Biodiversity, productivity, stability and their relationship within ecosystems haveemerged as a major scientific issue today. Grazing is one of the critical factorsaffecting the variation of plant community diversity in grassland ecosystem. Animaldiversity and the combined effects of various animals greatly affected the diversity,productivity and stability of plant community as well as the relationship between them.Meanwhile, the heterogeneous environment derived from plant diversity affectsanimal feeding strategy and then plant community varied. Therefore, it is necessary toexplore the effect of animal diversity on the variation of plant diversity, which isbeneficial to clarify the stability of grassland grazing comprehensively and providetheoretical basis for improving the understanding on the interactions between animalsand plants as well as the co-evolutionary theory. In addition, it will play a theoreticaland practical role in restoring or maintaining biodiversity and grassland management.In this dissertation, we mainly focused on the research that under the conditionof high and low plant diversity, different grazing (sheep grazing alone, cattle grazingalone, mixed grazing of cattle and sheep) had an effect on plant diversity, productivity,stability and their relationship in Songnen Grasslands. The results are as follows:(1) Grazing increased plant species richness (apart from the plot of sheep grazingalone decreased slightly in low plant diversity), Shannon-Wiener index and evenness.Species richness of mixed grazing was significantly higher than the single grazing.Shannon-Wiener index and evenness in pastures where cattle grazing alone under thelevel of low plant diversity and mixed grazing under the level of high plant diversitywere higher than any of the others.(2) The impacts of grazing on plant biomass were difference under the differentlevels of plant diversity. At the level of low plant diversity, grazing reduced the plantaboveground biomass. Cattle grazing resulted in lower plant aboveground biomasscompared with mixed and sheep grazing. At high plant diversity, in contrast, grazingincreased the plant biomass. Mixed grazing was particularly obvious and significantlyhigher than cattle grazing alone and the control group. With same conditions ofgrazing and different levels of plant diversity, the difference between mixed grazingand sheep grazing alone was significant except cattle grazing.(3) Grazing reduced the height of plant, the cattle grazing alone and mixedgrazing are the more apparent at the level of high and low plant diversity respectively. The total density of plants, decreased at the level of low plant diversity thoughgrazing and the least at plot of cattle grazing alone. On the contrary, the increase oftotal density of plants at the level of high plant diversity, particularly in mixed grazingand cattle grazing alone.(4) The relationship between plant aboveground biomass and diversity (plantrichness, Shannon-Wiener index, evenness) was a significant positive linearcorrelation at high plant diversity, while was no significant correlation at low plantdiversity.(5) Grazing improved the stability of the grassland ecosystem at any treatments.The variation coefficient (CV) of productivity was the lowest in plot of mixed grazingfurther in favor of the effect. Meanwhile, high plant diversity was less than the low.The relationship of plant diversity index and CV of aboveground biomass showedsignificant negative linear correlation at high or low plant diversity. In addition, it wasno significant correlation between plant evenness and coefficient of variation ofbiomassIn conclusion, animal grazing improved plant diversity and thereby the stabilityof the grassland ecosystem, furthermore, mixed grazing was more favorable to theeffect. Plant productivity and about itself in relations to diversity depended on thelevel of plant diversity. The grassland with higher plant diversity exhibited the higherthe stability of ecosystem.