A Study On Characteristics Of Community Structure Under Different Grassland Vegetatio

This research is based on Inner Mongolia Ergun meadow steppe，Manzhouli typicalsteppe, Shenmu desert grassland in northern Shaanxi and Annual weed communitiesin Yangling Demonstration Zone as the research object, through field investigation researchon grassland plant communities combined with "binary number" and "aboveground biomass"survey methods, we use the the power low method, the beta-binomial model and the gammadistribution model to analyze the survey data of the four regional grasslands. Our aim is toexplore the basic law which includes the number of grass species, species frequency, biomassand spatial distribution in different regions and different uses. Finally, by our quantitativeresearch on the basic characteristics of the grassland plant commutities and spatialheterogrneity between the composing plant species and the whole community, we can providea theoretical basis for the reasonable use of the grass, the scientific management and grasslandecosystem protection, moreover, we could come up with effective countermeasures formaintenance of grassland species diversity and the improvement of grassland productivity.The main conclusions obtained are as follows:(1) Analysis results showed that under the different utilization types, plant speciesoccurrence and biomass well followed to the power law, beta-binomial distribution andgamma distribution in proving spatial distribution rule of the plant communities in InnerMongolia Ergun meadow steppe, Manzhouli typical steppe, Shenmu desert grassland innorthern shaanxi and Anuual weed communities in Yangling Demonstration Zone. Thus, thisapproach can be used in the quantitative study of grassland spatial heterogeneity.(2) In the meadow steppes under two different use patterns, all showed a stronger spatialheterogeneity than the random distribution, and the number of species, species diversity index(H′), evenness index (J′) and spatial heterogeneity index of the whole community (δｃ) on themowing meadow steppe were all higher than those in the grazing meadow steppe. Themeadow steppe after grazing, indicator plant species such as Potentilla verticillatus,Taraxacum officinale and Plantago asiatica increased in the degenerated grassland. On theother hand, only high quality Gramineae plants such as Agropyron cristatum, Bromus inermisand Festuca ovina appeared in the mowing meadow steppe.(3) In the typical steppes under two different use patterns, all showed a stronger spatial heterogeneity than the random distribution, and the spatial heterogeneity of no-grazing typicalsteppe is lower than grazing typical steppe’ s. After prohibiting grazing, species diversityindex(H’), the average number of species and mean species diversity index were slightlylower in grassland qradarts; Stipa grandis and Leymus chinensis occupied community in thefirst two dominant species, had a lower degree of heterogeneity and closed to randomdistribution of the state; we have ten kinds of forage after prohiting grazing, takeArtemisia capillaries and Cleistogenes Keng for example, their spatial heterogrneity havedecreased to some extend, the result showed that no-grazing typical steppe have a certaindegree of recovery.(4) The number of co-appeared plant species is16in three different types of desertgrassland in Shenmu, according to the following order, the total number of species (Artemisiaannua steppe<Leymus chinensis steppe<Thymus mongolicus steppe), species diversity index(Leymus chinensis steppe<Artemisia annua steppe<Thymus mongolicus steppe), evennessindex(Leymus chinensis steppe<Thymus mongolicus steppe<Artemisia annua steppe), spatialheterogeneity index of the whole community (Artemisia annua steppe<Leymus chinensissteppe<Thymus mongolicus steppe). However, the average biomass of Leymus chinensissteppe is the biggest than others in grassland quadrats, so results show the highest biomassappeared at a medium level of community heterogeneity.(5) It can be seen through the research on the annual weed community in the YanglingDemonstration Zone, Setaria viridis had highly interspecific competitive and dominant in thecommunity, which have the highest biomass and the lowest spatial heterogeneity, closing tothe random distribution and reducing the spatial heterogeneity of the whole community;the total number of species and species diversity index decreased with the growth periodgoing on, the same as average species number and species diversity index within the quadrat;the average biomass increased with the growth period developing, but spatial heterogeneitydecreased, appeared the maximum biomass and minimum spatial heterogeneity index of thewhole community in July21, generally speaking, grassland community biomass is reducingwith the increase of the heterogeneity index.