辽西北地区植被分布组成与土地沙化关系的调查

在辽西北部地区土地沙化调查中,进行的植被调查结果表明,草本植被平均盖度为71.9%。由于草地面积减少与连年干旱的影响,湿生植物、中生植物分布缩小,而旱生植物分布扩大。出现频度最高的植物共20种,其中1年生田间杂草和沙生植物的总出现次数与数量高于多年生禾草和其他多年生植物,为其1.8倍和2.7倍。因此,该区植被退化与土地沙化发展比较强烈。这20种植物中过度放牧和极度放牧沙化植物的出现次数和数量高于适度放牧(包括不放牧)和重度放牧,可知过度放牧和极度放牧,是植被退化与土地沙化的主要因素。蒺藜草的分布频度达25.0%,多度达23.7%,已经成为当地草原的主要害草。

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.