Pearl River Source Of Degraded Ecosystems Restoration And Reconstruction Study

Soil erosion, environmental degradation, natural disasters and other issues are prominent in the source area of the Pearl River because of the particular topography and limestone properties. Therefore, the restoration and rehabilatation in this area is extremely important. In this paper, the research object is the source area of the Pearl River. Fuyuan County is the main pilot area. We can get the soil physical properties, soil nutrient characteristics, biological diversity in the way of field survey, field observation, experimental analysis, and we can separate the eight kinds of restore mode to ecological degradation of the pilot area(Quercus semecarpi folia shrub(Cl), Alnus repolensis+Sabina chinensis forest(C2), Pinus armandii forest (C3), Pinus yunnanensis+Quercus variabilis Blume forest(C4), Lithocorpus dealbatus forest(C5), Castanea mollissima Blume forest(C6), Cryptomeria fortunei Hooibrenk forest(C7), Alnus repolensis+Pinus yunnanensis forest(C8)) from each other. We use the correlation analysis and the gray relational grade analysis (GRA) to find the comprehensive ecological benefits of the eight modes, aimed at provide a scientific basis to the ecosystem restoration and reconstruction of the source region of the Pearl River. The results are as follows:(1) Soil physical properties:The study by comparing the eight kinds of restore mode of soil physical properties compared with the former two stages (2001,2004) shows an improving trend, and the soil surface (0-20cm) and the lower (20-40cm)have great similar trend. There is a obvious improvement in soil volume weight and soil porosity at the early restoration of vegetation, and gradually improve the situation stabilized, reaching a stable value. Improved soil volume weight and porosity indicates that the soil structure and the moisture retention capacity and conservation water capacity are improved.(2) Soil permeability:The study shows that water infiltration and infiltration rate is bigger at the initial stage, and with the infiltration time increases, the infiltration speed gradually reach a fixed value, that is, steady seepage, so the beginning of infiltration speed is higher than the steady infiltration velocity. The permeability of C5 is the best, C6 followed by, C3 is the worst. Because the degree of permeability impact the soil and water conservation, so the water conservation of C5 and C6 is better than C3.(3) Soil chemical nutrient characteristics:With the increase years of vegetation restoration, soil nutrients are basically improving;but at the the initial stage of restoration, the soil nutrient content was reduced that was mainly due to absorption of trees. With faster growth of trees, the biomass increase, and the return of vegetation increase, then the amount of soil nutrients have increased. Soil organic matter content, total N, available N, available P and K content in line with changes in the similar trend, the overall upward trend. Soil total P content was increased after the reduce in the trend. Total P content in 2008 was lower than the former because the accumulation of plant migration, part of P was fixed at the plant, and the return is also affected by litter composition and decomposition rate. Can also be seen that in the surface soil total P content is generally higher than the lower; pH values showed a downward trend.(4) Changes in biodiversity:The study of the restoration shows that:C8 has the most richness and the highest diversity species in tree layer, and species distribution is the most evenly. C1 is the highest in shrub layer species, C4 is the lowest, C3 is the highest in species diversity, C4 is minimum, C5 has the most uniform distribution. C8 is the highest in herb layer species, C7 is minimum, C5 has the highest species diversity, and the most uniform distribution.C8 is the highest in community species, C7 is minimum, C5 has the highest species diversity, and the most uniform distribution.(5)Through correlation analysis of physical, chemical nutrient char-acteristics shows:Litter, soil bulk density, porosity, the noncapillary porosity and permeability of the soil has a significant correlation relationship, indicating that the interaction between them is great; soil organic matter content, soil total N, hydrolysable N has a significant positive correlation relationship, because of soil organic matter has a great impact on nitrogen; soil nutrient characteristics of organic matter, total nitrogen, hydrolysable N, available phosphorus, potassium, etc. have a positive correla-tion between each other, suggesting that organic matter, total nitrogen, hydrolysable N, available phosphorus, total potassium content depends not only on the content of the soil itself, but also closely related with other elements. It have important effects to soil nutrients, and soil nutrient indexes are mutual influenced.(6)Through the gray correlation analysis method shows:at the improvement of soil physical properties, C5 is the best, C3 is the worst; at the improvement of chemical nutrients in the soil properties, C4 is the best, C5 followed by, C3 is the worst. The results showed that soil improvement of eight modes is: C5> C4> C2> C6> C1> C8> C7> C3.