Study On Desert-Oasis Ecotone Vegetation And Oasis Stability

Species diversity dominance niche community ordination and classificationx population spatial pattern in desert-oasis ecotone in Fukang,along with their relation to soil factors,are analyzed by quantitative vegetation analyze methods. The characteristic x dynamic of landscape ecological pattern and their influence factors are also analyzed by the partition of landscape transect. Oasis stability is primary explored by the successive observation of soil water and salt in Sangonghe basin in Fukang. The main results are as following:1 Species diversity indices are significantly different among communities in desert-oasis ecotone,but are low in general;diversity indices based on important value and cover are more properly in arid desert areas. Soil pH,total salt content,soil organic matter,Cl-,K++Na+,Mg2+,total nitrogen and available phosphorus are related to species diversity significantly.2 Shrubs and undershrubs in desert-oasis ecotone can be divided into four groups based on the niche breadth. Based on the niche overlaps matrix ,overlap between Reaumuria soongorica and Haloxylon ammodendron is large;overlaps among Kalidium foliation-,Suaedaphysophora Kalidium caspicum- Tamarix ramosissima T. elongata are large;the others' overlaps are small. Simpson Shannon-Wiener methods for measuring niche breadth and Wang-gang niche overlap formula are more fitted to ecotone.3 Eight communities are identified by gradient analysis in desert-oasis ecotone,and species are divided into 5 ecological groups. DCA ordination is superior to CCA and DCCA. Variation of vegetation explained by environmental and spatial factors reaches 23.4%;among these the species matrix explained by non-spatial soil factors account for up to 11.5% of variation,spatial variation that is not shared by soil factors explains up to 11.6%,their interaction explains up to 0.3%.4 Reaumuria soongorica and Haloxylon ammodendron in desert-oasis ecotone show random distribution. The seedling of H. ammodendron shows clump distribution. The effect of the x2 test for fit to three distributions is bad to desert dominant population.5 The dynamic of soil water content and salinity is significantly different among communities in ecotone. The soil moisture and salinity are two main factors that influence the distribution and succession of plant communities.6 Diversity fragmentation and evenness of ecological landscape in Fukang increase with more utilization and development. The change of landscape pattern about land utilization is mainly area variation of plantation and wasteland in pluvial fan and alluvial plain,the key influence factors are the dynamic of soil moisture and salinity under the development of water and land resource.7 Topography and land use are main factors affecting the change of groundwater table,then influencing the redistribution of soil moisture and salinity. Soil secondary salinization can be considered as the main factors that influence the stability of new oasis in alluvial plain.8 NDVI value in oasis is significantly higher than the value in desert,both of them havedifferent rules in monthly variation. Irrigation temperature and precipitation have effect on variation of NDVI in oasis,the correlation coefficients of sparse vegetation NDVI in desert with climatic and hydrological factors are insignificant and meaningless in practice. The drive factors of oasis NDVI are only adapted on oasis in arid land and are not fit to desert system in arid land.9 The status and characteristic of ecosystem stability in every topography position in Fukang desert and oasis is different,so the different measures should be made in process of utilization and management.