| Due to different exploitation intensity and ecological restoration measures used in Hongchiba region, Wuxi county, the vegetation have been formed a series of succession stages, i.e. herbaceous stage scrub-shrub stage-shrub-tree stage-pure Larix daempferi conifer forest stage-Pinus armandii needle broad-leaved mixed forest stage-natural deciduous broad-leaved forest. On the basis of substituting space for time, communities dynamic characteristics including composition and structure, species diversity, population niche, soil nutrient content were investigated. In the meanwhile, the best community that was picked out from natural deciduous broad-leaved forest was taken as contrast. And the hight, dominance, soil fertility, coverage, composition and biomass of the community were used as community characteristics parameters to comprehensively evaluate the restored degree of communities at different restoration stages. The results as following:i) Totally, species diversity increased gradually with the development of community succession. When community developed to climax stage, however, the species diversity would decrease attributing to the disappearance of some pioneer species. In addition, species diversity of the shrub-tree ecotone would increase swingingly, due to the "bundary effects". Thus, species diversity could not be regarded as a unique index for measuring the effect of vegetation ecological restoration. Moreover, the reasons resulted in the higher species diversity should be further discussed. Stability of community structures and its ecological function should also be considered simutaneously.ii) Some native spcies, eg. Crateagus wilsonii, Cerasus szechuanica, Malus prati, Toxicodendron verniciflua, are dominants and co-edificators in almost every woody communities. It indicated that the reproduction and spread ability of native species were stronger than those of artificial species. And the native species were more suitable for the native habitats during the process of ecological restoration. Native forest therefore should be built with native species. The powerful restoration potentiality of native species should be utilized more wildly in the process of ecological restoration and rehabilitation.iii) For artificial communities including herbaceous community, pure conifer and needle broad-leaved mixed forest, the poor niche configuration and serious niche overlap of component species made the composition structure of community be in an unstable state. Whereas, for the natural forest consisted of native species, the niche overlap was low and the interspecies relationship was harmonious. The composition structure of community thereby was more stable. Considering the fact, native species should be used as cultivation object and regional vegetation should be served as ultimate object during the process of ecological recovery and rehabilitation.IV) Soil nutrient contents increased with the succession progress generally. But for conifer community, since needle leaves decomposed very slowly, soil nutrient contents were rather low and even lower than those of former stages. On the contrary, natural communities consisted of broad-leaved species, including shrub community, commonly possessed high soil nutrient contents. Therefore, it should be emphasized to enhance the self-fertilization capability of forest by adjusting the species composition and increasing the proportion of native broad-leaved species.V) Occupying space and covering ground should be served as the main strategy in early stage of vegetation restoration, which would enable the community coverage to rehabilitate rapidly. In mid-stage, due to the change of light environment and the species substitution, component adjustment should be chose as the main strategy. In later stage, both biomass accumulation and component adjustment should be conducted as main strategy. It can be found that the restoration of coverage, component and dominance were always prior to that of biomass during the course of restoration. Meanwhile, t...
|
PDF Full Text Request