Study On Community Structure And Soil Carbon Sequestration In The Forest Of Miaodao Archipelago

Forest ecosystem is an important component of terrestrial ecosystems, it is significant important to study forest plant communities and soil carbon sequestration function of a certain area for study the region’s soil and water conservation and forest carbon cycle. Island is a special terrestrial ecosystem, on which the communities and environmental conditions are similar to those of the mainland, but its ecological structure is relatively simple, and the species richness is lower than that of the mainland. Island regions are especially vulnerable to future changes in eustatic sea level, and are often affected by natural disasters. There is a big difference between the forest plant communities, density of soil organic carbon in forest and that in other land areas because of the special circumstances.Based on the vegetation data and soil samples investigated in stand plot, forest vegetation composition, forest plant community structure and species diversity in the southern islands of Miaodao Archipelago in Shandong Province were study, the impacts of different parameters such as site conditions, vegetation diversity and soil properties of forest ecosystem(Pinus thunbergii, Robinia pseudoacacia, and Pinus thunbergii×Robinia pseudoacacia) on soil organic carbon density were discussed. The results of the study are showed as follows:(1) One hundred forty-eight kinds of vascular plants belonging to fifty-three families and one hundred twenty-threet genera were investigated in the survey area, including ten kinds of trees, twenty kinds of shrubs and one hundred eighteen kinds of herbas.(2) According to the important value of plant, the main forest types are classified as P. Thunbergii forest, R. Pseudoacacia forest and P. Thunbergii×R. Pseudoacacia forest, where the largest is P. Thunbergii forest. There is difference in forest types, shrubs and herbs species composition among in the southern islands of Miaodao Archipelago.(3) By using TWINSPAN, the population of shrub layer were classified into six types, they are Morus alba group, Robinia pseudoacacia-Cudrania tricuspidata group, Ziziphus jujuba var.spinosa group, Grewia biloba var.parviflora group, Vitex negundo var.heterophylla group and Amorpha fruticosa group; the population of herb layer were classified into six types, they are Galium verum group, Setaria viridis group, Artemisia argyi group, Miscanthus sacchariflorus+ Carex lanceolata Boott group, Cleistogenes Keng group, Carex lanceolata Boott group.(4) By using canonical correspondence analysis(CCA), the ecological gradient analysis of shrubs communities and herbaceous communities were analyzed. The results of CCA indicates that tree cover, soil p H, available phosphorus and soil moisture were the most important environmental factors which influence shrub distribution; available nitrogen, available phosphorus, soil p H, altitude, slope, shrub cover and soil organic matter content were the most important environmental factors which influence herb distribution and growing.(5) The species diversity of plant communities varies in different forest communities, richness index S, Pielou evenness index J, Simpson diversity index D and Shannon-Wiener diversity index H refer to the overall performance of P. Thunbergii×R. Pseudoacacia forest > P. Thunbergii forest > R. Pseudoacacia forest, the vegetation vertical structure, species diversity of mixed forest is superior than pure forest, it is conducive to sustainable management of forest.(6) The index of species richness, Shannon-Wiener diversity and Simpson diversity of forest community changes from high to low in the order herb layer, shrub layer and tree layer, and the changing consequence of Pielou index high to low is shrub layer, herb layer and tree layer.(7) The results showed that the SOC density in the topsoil under different forest types increased in the order(p<0.01): P. Thunbergii×R. Pseudoacacia forest > P. Thunbergii forest > R. Pseudoacacia forest, moreover, the SOC density of mixed forest was much higher than that pure forest. Based on the mathematical statistics method, the correlation between SOC density and environmental factors were analyzed. Pearson correlation analysis showed that there was negatively correlation between SOC density and slope(R =-0.423), while there was no significant correlation between altitude, aspect and SOC density. Besides, there was no obvious correlation between soil carbon fixation capability and vegetation diversity. Principal Components Analysis(PCA) indicated that sand, silt, total nitrogen, nitrogen, organic matter content in the forest were the major controlling factors on SOC density in the southern islands of Miaodao Archipelago.