The Research Of Stability And Population & Community Dynamics Of Haloxylon Ammodendron In Gurbantunggut Desert

To study the Haloxylon ammodendron community,3 sample strips and permanent large-scale plots were established.Through the field investigation,long-term monitoring,and soil chemical analysis,the research was based on the theory and methods in floristic geography,quantitative ecology mathematics statistics,geostatistics and ecological niche theory.The population structure,density,biomass,static life table,survival curve,seedlings and dead stains,spatial pattern,community structure,biodiversity,gradient alalysis,community floristic characteristics,community structure species diversity and so on were studied.Correlation analysis,grey correlation analysis,hierarchical structure model and AHP were used to screen and identify key factors affecting the stability of sandbinding vegetation.Quantitative assessment on the stability and preliminary calculation of the vegetation coverage threshold of sandbinding vegetation's stability were finished.The vegetation coverage of the whole Gurbantunggut retrieved by remote sensing data wase use to map the divisional chart of SVSI in Gurbantunggut Desert.The main obtained results are as follows:(1)The age structure of populations had a reverse ?J? shape,suggesting growth type population.The survival curve tended to be the type of Deevey-III with the high mortality rate at early stage(66 %)and low mortality rate at late stage and high mortality rate again in the old.H.ammodendron population mortality in small age class and harsh environment fluctuated sharply too.The seedlings and death plant density in F.were higher than in M..Spatial pattern of h.ammodendron showed that aggregated distribution was the main trend in seedings and with the growth of h.ammodendron aggregation degree,the adult tree was characterized by random distribution type.(2)H.ammodendron community belonged to 15 families,38 genera and 51 species of plants which partly were Chenopodiaceae(?40 %).The main was taproot type(87 %,92%,42 %)that were short individual below(0-20cm),drought-resistant plant and miniature leaves or degradation leaf..H.ammodendron community horizontal stand structure had mosaicism and plaque.From the southern to the central of desert,the proportion of perennial plants increased gradually and the total biomass decreased.The community diversity index H didn't have obvious trend.Biomass of h.ammodendron was far greater than the undergrowth biomass.(3)We identified and screened the key factors which influenced the stability of sandbinding vegetation.They were coverage,diversity index,the proportion of perennials,clay content,SOM content and soil moisture content,which consisted of the sandbinding vegetation Stability index(SVSI).(4)We raised the method of evaluation the stability of sandbinding vegetation was the sandbinding vegetation Stability index(SVSI)with the results of stablility in F.,semistablity in S.,instability in M..F.and S.is of mild desertification and M is severe desertification.The threshold coverage that maintain stability was calculated with the results of stability vegetation:semi-stability vegetation 48 % to 22 %,and instability vegetation 0 to 22 %.The divisional chart of stability of Gurbantunggut Desert was mapped.