Ecological Characteristics Study Of Rosa Xanthina Community In Shanxi

Rosa xanthina is one of the Widely distributed species on theLoess Plateau, which plays a very important role in the protection ofecosystems of the Loess Plateau region. In this paper, based on thefield survey, the community characteristics of Rosa xanthina weresystematically and comprehensively studied from the flora and thecommunity ecology point of view, including the communitystructure, composition, classification and sorting, species diversity,interspecific association. The purpose of this study is the analysisof the ecological relationships between plant community andenvironment, and to provide some theory bases that could beapplied in the ecological restoration and protection of degradedecosystem in Shanxi.(1) 31 plots were set up and investigated in the field.The resultsshow that the height of Rosa xanthina community was from 2m to4m; the vertical structure was simple, which could be obviouslydivided into two layers: shrub and herb. There were totally 218species belonging to 163 genera of 56 families in Rosa xanthinacommunity, Asteraceae was the family with the richest species,next was Rosaceae, Leguminosae and Lamiaceae. There were 56species of plants in shrub layer, in which Rosaceae was the familywith the richest species. In shrub layer, the species composition was simpler than herb layer. There were 162 species of plants inherb layer,and Asteraceae was the predominant family, in whichCarex lanceolata was dominant species. The flora of 156 seedplants founded in the community was classified into 14 areal typesand 9 subtypes, of which north temperate elements had 32 genera,accounting for 20.51%, world distribution elements or northtemperate zone and southern temperate disjunct elements had 24genera, accounting for 15.38%, and southern temperate floristicelements dominated in the community. Community physiognomywas characterized mainly by phanerophytes.(2) Based on the data collected from 122 quadrats,theclassification and ordination of Rosa xanthina community werestudied using two-way indicator species analysis(TWINSPAN) anddetrended correspondence analysis(DCA). According to the resultsof TWINSPAN classification, 122 quadrats of Rosa xanthinacommunity were classified into 15 association types. DCAordination analysis not only exhibited the same classificationresults as the TWINSPAN analysis, but also reflected therelationship between association types and environmental gradient,that is, the first axis of DCA mainly reflected the position change ofslope, and the second axis of DCA indicated the elevation change ofaspect. All these results showed that the species composition anddistribution of Rosa xanthina community were affected mainly byslope position and elevation change.(3) Four diversity indices were applied to analyze the speciesdiversity characteristics of Rosa xanthina community. The resultsshow that all these indices could effectively reflect the character of communities, such as the structure and habitat. Meanwhile, theyalso reflect the particularity of composition and structure of Rosaxanthina community. Species richness and species diversityindices of plants were obviously lower than those of herbs, but therewas no significant difference in the evenness. The variety ofdiversity in different plots was significantly related with habitatconditions. The relationship between vertical structure and speciesdiversity of the community shows that species richness and speciesdiversity index of herb layer was higher than shrub layer. The orderof the herb layer of magnitude of species diversity was higher thanthe shrub layer. The diversity indices of shrub layer and herb layerwere varied in the communities. The shrub layer is relativelyhomogeneous types and the dominant species obvious while morethe type and quantity of the herb layer.(4) Jaccard index, Ochiai index, Dice index, andχ2test with 2×2contingency table were used to analyze the interspecificassociation among 214 species-pairs of 22 dominant species ofRosa xanthina community. Pearson’s correlation coefficient andSpearman’s rank correlation coefficient were also applied tocalculate correlations between species. The results showed that110, 93 and 119 species-pairs were positively correlated,while 100,138, 112 species-pairs had negative correlations, based onχ2testfor a 2×2 contingency table, Pearson’s correlation coefficient test,and Spearman’s rank correlation coefficient test, respectively, andthe numbers of positive correlated species-pairs were nearly equalto the negatives. Compared withχ2test and Pearson’s correlationcoefficient test, Spearman’s rank correlation coefficient test was an effective method to study the relationships between species.