Studies On Vegetation And Soil During Ecological Restoration Process Of Sandy Grassland In North-west Sichuan

This paper took the sandy grassland of Zoige plateau in north-west Sichuan for example. Through the investigation and analysis of community and soil, the changeful regulation of community quantitative characters and soil features during the restoration succession was studied. The main results are as follows:(1) The plant species were poor in Zoige's sandy grassland, which mainly belonged to Leguminocae, Gramineae, Compositae and Cyperaceae. With the recovery process, the number of plant species increased slowly at the start, then rapidly in the following stage. At last the community increased 14 species in total.(2) The community characteristics were effected mainly by the sub-dominant and the accessory species, whereas the dominant species' influence are small. The high increased gradually during the early stage, then dropped a little after reaching the peak value during the medium stages, and tended to the average value of alpine meadow duringthe later stage. The coverage varied logistically (P=68.2800/1+e^{(x-2.0365)/0.0379}). The density, whichchanged from 166 ind/m² to 760 ind/m², had not displayed the obvious change rule. The IV of dominant species, sub-dominant species and accessory species tended to 15% during the process of succession, so the community developed to the multi-superiority community. Meanwhile the plant diversity indices increased step by step.(3) The up-ground biomass , which varied from 185.6g/m² (the 1st stage) to753.5g/m2 (the 4th stage), showed the tendency of logistic growth (B₁=480.9214/1+e ^{(x-1.3924)/0.6171}). (4) The physical clay (< 0.0 lmm) of sandy grassland in north-west Sichuan ranged form 9.9% to 10.7%, so the soil texture mostly was purple sand. And the pH value of soil assumed neutrality in general.(5) Because of surface evaporation and physiology transpiration, the surface layer soil (0-10cm) water content assumed the obvious increasing tendency, the other layers water content changed in no law, and the average water content showed a rule that increasing-dropping- increasing.(6)The soil quality had improved significantly during the process of succession. The organic mater increased in general. The regulation of total nitrogen is consistent with the one of organic mater, so the total nitrogen and the organic mater had a significant positive correlation with (r = 0.947^**). The total phosphorus was gradually increasing, positively related with the organic matter(r=0.588). The content of total potassium varied undulatingly, and the correlation between total potassium and organic mater is positive(r=0.377).