Surveys on relationship of vegetation distribution compositions and land desertification in northwestern Liaoning

Investigation on status of land desertification in northwestern Liaoning was conducted.The results regarding vegetation indicated that the average coverage for grass vegetation was 71.9%.Distribution of phreatophytes and mesophytes lessened and distribution of xerophytes expanded due to the effects of decrease of grassland area and drought in successive years.The degree of presence for 20 plants was highest,among which total times of presence and quantities for annual weeds in fields and sand grown plants were 1.8 and 2.7 times higher than perennial gramineae grass and other perennial plants respectively.Vegetation degradation and land desertification were serious in this region.Times of presence and quantities for abovementioned 20 plants in overgrazing and extreme grazing areas were much higher than that in moderate(no grazing included) and heavy grazing areas,which showed that over grazing and extremely grazing were key factors for vegetation degradation and land desertification.Distribution degrees of presence and richness for Cenchrus panciflorus attained 25.0% and 23.7% respectively,Cenchrus panciflorus has become the major harmful grass in the local grassland.