Preliminary Study Of The Vegetation And Soil Changes In Northern Guangdong, Rocky Desertification Process

Karst mountainous region in the north of Guangdong is one of the abroad, ands erious harmful desertification lands in South China. The paper selected the typical desertification area——Yanbei Town, which located in the north of Guangdong Province, Yingde City, as the research spot. On the basis of field semi-permanent observation to slightly, moderately, severely and very severely desertification land in this typical area. The paper analyzed the processes of rocky desertification, including degradation of vegetation and degradation of land productivity with statistic analysis, and discussed the changes of vegetation community's structure, vegetation coverage and species diversity, land productivity, soil granularity and soil nutrients.Research revealed that, under the typical subtropical environment in the north of Guangdong Province, the process of desertification is a complex superficial process which is composed of the process of sand geomorphology changes, the process of degradation of vegetation.In the process of degradation of vegetation, the vegetation community's structure becomes more and more simple, and the life form changed obviously, the quality of vegetation degraded, which lead to the decrease of vegetation coverage and the reduction of species diversity. From slightly to medium, severely and very severely desertification land, the vegetation kinds became less. The structure of vegetation community tend to the vegetation coverage decreased from slight degree's 63.41％to less than 7.52％in extreme degree; Standing biomass also decreased significantly from 438.82g·m^-2 to 14.57 g·m^-2 in process of rocky desertification. At the same time, the species numbers and distributing were more difference in the rocky desertification. The vegetation degradation was the important trigger and sign of development of rocky desertification.With the development of the rocky desertification, the soil thickness became thinner and thinner, the tendency of average soil thickness changed from 40cm to 35cm, 20cm and below 5cm and soil coverage changed from 60.6％to 2.97％, while soil grain became bigger and bigger, presenting the coarse characteristics in process of desertification. Meanwhile soil fertility and productivity reduced gradually while degree of soil erosion and leaching strengthened, bio-enrichment capacity weakened and organic carbon decreased obviously, which result in soil total N, available N, available P and available K are all decreased significantly (P＜0.001).The process of rocky desertification is a complex process. The factors in the processes of soil geomorphology changes, the degradation of vegetation are interrelated and interacted. So vegetation and soil are ought to be the main index of the rocky desertification stage. Rocky desertification results in the deterioration of physiochemical property of soil, which restrained the growth and development of vegetation and leads to the land productivity declining. The two factors formed an infernal circle results in percentage of bare rock area increasing.