Impacts Of The Deyeuxia.angnstifolia Invasion To Plant Communities On The West Slope Of Changbai Mountain

From2000to2500m on the west slope of Changbai Mountain, we have foundthe phenomenon of Deyeuxia angustifolia invasion to tundra zone.The impact of thephenomenon to plant communities were studied in this paper. The study patches aredivided into three kinds of communities depending on D. angustifolia coverage ofeach patch: Mild invasion patch, Moderate invasion patch and severe invasion patch；And the Rhododendron chrysanthum community was used as a control group to beanalyzed.Firstly, we studied the sequence between the R. chrysanthum communities and theD. angustifolia communities using the NMDS sort method. Secondly, The α diversityand β diversity changes along an altitudinal gradient increasing of different invadedplant communities are studied. We select the Shannon-Wiener index、Evennessindex、Margalef’s index and Richness index to instruct the α diversity and Whittakerindex and Wilson index to instruct β diversity. Lastly, we do a comparison analysis todifferent patches with Tukey’s HSD test of the one-way ANOVA and. The destinationis to test whether the species diversity differences between different invasion patchesreached a significant level. The results show that:1) The D. angustifolia have invaded the tundra in the west slope of ChangbaiMountain. The number of shrub species significantly reduced with the increase ofinvasion degree. The herbaceous species gradually increased, and the average heightof plant communities also obviously increased. At low altitudes, D. angustifoliapatches number is small, but the area is larger than the high altitudes; However, athigh altitudes, the number of patches is large, but smaller size than the low altitudes.2) The NMDS sort analysis showed that there were significant differences incommunity composition between D. angustifolia communities and R. chrysanthumcommunities.The D. angustifolia communities have more plant species than the R.chrysanthum communities. In D. angustifolia communities most of plants areherbaceous, while, shrubs plants mainly composed the R. chrysanthumcommunities.This indicates that the D. angustifolia invasion had changed the structureof the original community, and the newly formed community is herbaceouscommunity, not shrub community. The D. angustifolia community which washerbaceous community had been almost formed. 3) The α diversity indicated that the species diversity appeared an obviousdownward trend along altitude gradient in the R. chrysanthum communities. Thespecies diversity in D.angustifolia invasion patches and R. chrysanthum communitieshas great difference because of the invasion. And the species diversity index changesdifferently in different invasion degree patches. Finally, we can conclude that theinvasion has an obvious impact on the species diversity in plant communities,including the increase of species diversity and number in the communities.4) The β diversity indicated that the R. chrysanthum had formed a stablecommunity above the forest and tundra ecotone, showing a high level speciesreplacement rate. With the invasion intensity increases, the R. chrysanthumcommunity becomes unstable. And the dominance of R. chrysanthum is graduallyweakened. The D. angustifolia community which is herbaceous community has beenalmost formed in severe invasion patches.5)Through the comparison of diversity indices, the species diversity inD.angustifolia invasion patches and R. chrysanthum communities has great differencebecause of the invasion. The fierce competition among new increased species hasseverely effects on the species diversity in plant communities.