The Study On Species Abundance Distribution And Main Species Spatial Point Patterns Of Bothriochloa Ischaemun Community In The Loess Hilly And Gully Region,China

This paper took Bothriochloa Ischaemun Community in the Loess Hilly and GullyRegion as main research object, based on the dates of field survey and analysis, using diversity analysis methods, population distribution analysis methods and spatial point pattern analysismethods, and combined with whiteecological characteristics of species, habitat heterogeneityand succesessional stages, we analysised structures and species components, species abundacedistributions and spatial patterrns of major species in Bothriochloa ischaemun Community, the spatial associations between them, and the ecological processes underlying are discussed. The results were as following:1.The general sequence of succession of abandoned frams in the Loess Hilly and GullyRegion was: annual weeds association community (Artemisia capillaris et.), perennial herbage community (Stipa bungeana et.) and zonal community (Bothriochloa ischaemun) and so on. With vegetation succession, The value of Patrick index, Shannon-Wiener index and Simpson index increased first and gone down to some levels, the highest value was at the middle stages of succession community of Stipa bungeana, and evenness indexes Pielous and Alatalo was increased and finally stabilized.2. In succession, Artemisia capillaris community species distribution of many do not accord with the selected four model; Stipa bungeana community species distribution model for many degrees Broken-Sticks model and Zipf model, Zipf model is much better; Bothriochloaischaemun community species distribution model for Zipf model. With vegetation successionproceeding, community composition became complicated and gradually improved the stability of the community. This was as vegetation succession, community species composition and structure changed, especially in the community was the advantage of the succession of the community species which were more important.3.The spatial distribution pattern and interspecific coorelations of the main populations inthree types of Bothriochloa ischaemun communities were analyzed at multiple(0-100cm) scal es by the O-ring functions of univariate and bivariate. The results were as following, main populations shown different patterns, populations of Bothriochloa ischaemun, Artemisia sacrorum, Artemisia giraldii fitted the double-cluster process,Lespedeza davurica, Stipa bungeana fitcluster process at0-6cm and random dis-tributions at larger scales. The results confirmed thatcluster patterns are popular in the natrue.4.The interspecific coorelations of the main populations were independentce or simiar independence, which is the result of succession, at the stage of Bothriochloa ischaemun, nichehad been divided further, each population occupied a favorable position, dependence and competition between each other weakened, community structure was stable basically.Species ecological characteristics, competition, habitat heterogeneity influnces the distributions and correlations most.In summary, Bothriochloa ischaemun community had a higher species diversity and evenness, species abundance distribution followed a Zipf model, spatial patterns of dominant speciesshown small scale cluster and larger scales random or eveness, interspecies relations mainlyshowed independent, the community is a stabile zonal community in the Loess Hilly andGully Region.