Study On The Damage And The Adaptation Strategy Of The Vegetation During Sandy Desertification Process

The social and economic sustainable development in the arid and semiarid area in China has been restricted by sandy desertification heavily. The studied site (DUOLUN county) has distinct geographical position and special terrain and geomorphic, so studying in this area plays the important role in the research on the sandy desertification in northern China, especially for grassland. It was studied integratedly on sandy desertification interference according to the principle and methods of community ecology, population ecology and physiological ecology through observation outdoors and analysis indoors in 3 years. The damage and adaptation strategy of the vegetation during sandy desertification process in natural conditions were discussed through variations of community, population and individual, morphological and physiological characters under different gradients of sandy desertification. The results were as follows:1. With the process of the sandy desertification in grassland, the contents of clay decreased. The soil moisture decreased, especially in 20-30cm layer. The soil moisture in deeper was higher than the super. The soil bulk density increased. The contents of organic matter, carbon and nitrogen in the soil decreased very significantly, the reduction of nitrogen was more rapid than that of carbon, thus C/N in the soil increased. It shows that the provided nitrogen in the plant was scarce heavily. The positive correlation was significant between the granular composition and the nutrient element in the soil. The correlation between the clay and N was nearer than that of the clay and C, C and N. Therefore the reduction of the fine particle resulted in the reduction of N very significantly during sandy desertification.2. With the process of the sandy desertification, the coverage, density, number of species, biomass and diversity index of community decreased. The ratio of biomass aboveground- biomass underground did not changed significantly. C/N in the soil was the nearest to community through their correlation analysis.3. With the process of the sandy desertification, individual height, density, leaf area index(LAX), biomass aboveground, reproductive allocation(RA) of the common populations and the specific leaf area(SLA) of the main plant changed alternatively.(1)Individual height, density decreased overall. Leymus chinensis had Very significantdifferences in the different gradients of desertification. Cleislogenes squarrosa and Artemisia frifida increased in potential desertification stage (PD), light desertification stage (LD) or moderate desertification stage (MD) because of their phasic statuses of dominant species and their stronger stress resistances. Melilotoides ruthenica increased before MD, and after MD its morpha growth reduced along with the others, only that it had no significance. This change was the same as biomass aboveground of M: ruthenica. The significance of density of M. ruthenica in the different gradients of desertification was only in the increase with the development of the sandy desertification. The significance of density of C. squarrosa was only in the decrease with the development of the sandy desertification. The significance of A. frifida was both in the increase and in the decrease with the development of the sandy desertification. The variances in the different gradients of desertification and the changes of individual height, density of different populations showed the variance of the damage and adaptability of different plants in the worse environment. L. chinensis was damaged heavily, thus its adaptability was little. C. squarrosa and A. frifida were damaged to certain extent, but they had the stronger stress resistances. Responses of M. ruthenica to sandy desertification were weak, moderate sandy desertification made for its growth, but its reduce of growth resulted in exorbitant sandy desertification as the same as other populations.(2)The specific leaf area of majority investigated plants decreased, thus their morpha growth reduced. Then A. frigida and M.