The Variation Of The Structure Of Plant Communities And Its Mechanism In Anxi Hyper-arid Desert Area

We selected six parallel plots of plant communities in the Anxi hyper-arid desert area to investigate the seasonal and inter-annual variation of species abundance, coverage, richness and climatic conditions for three years. On this basis, desert plant community structure, seasonal and inter-annual variation were explored through analysis the changes in plant community structure, biodiversity, as well as growth conditions of some plants. Furthermore, comparative analysis between the relationship of dominant species in internal communities and the impact of environmental conditions on changes in community structure to illustrate the internal mechanism of the desert plant community structure changes.The results showed:(1) Seasonal variation of species richness and abundance is mainly caused by the seasonal variation of annual plants, and the coverage changes of communities caused by the seasonal variation of the perennial shrub coverage;(2) Inter-annual changes in species richness of plant communities, abundance and coverage is mainly caused by the inter-annual variations of annual plants;(3)There is a positive relationship between the seasonal variation of the species richness, abundance, the coverage and changes in local rainfall and temperature, but has nothing to do with the number of species richness in plant communities, the inter-annual variability of the abundance and coverage. Therefore it could be determined that the rainfall and temperature have greater impact on the seasonal variation of desert plant community structure, but have little impact on inter-annual variations. Within a slight range of changes in climatic conditions, the desert community structure maintains a relatively stable structure.(4)Changes in the composition of the soil has little effect on the species richness and abundance, coverage, Shannon-Wiener index, evenness index and Simpson index changes of plant communities.(5)In desert ecosystems, competitions the main relationship between the main species within plant communities. There is a negative relationship between the seasonal variation of the abundance, coverage in plant community and the intensity of competition, and negative relationship also showed between inter-annual variation of the abundance, inter-annual variation of coverage and the intensity of competition.(6)The aspect on the contribution of structure changes of plant community, the contribution of the competition of the abundance on the seasonal variation is greater than that of the climatic conditions; the contribution of climatic conditions to coverage on the seasonal variation is greater than that of the competition; the contribution of the competition of the abundance and coverage of the inter-annual variability is greater than the contribution of the climatic conditions. It means the relationship between plant communities within the main species determined the seasonal variation of the number of individual plants, and climatic conditions determined the seasonal variation of the community coverage. Internal factors played a decisive role in the inter-annual variability of the abundance and coverage, and it also illustrated that inter-annual variation of environmental conditions is slight.