Variation Analysis And Environmental Interpretation Of The Understory And Soil Microbial Communities Of Five Different Plantations In Southern Subtropical Area Of China

This study investigates the communities of understory and soil microbial as well as the species-environment relationship of five typical plantations in southern subtropical area of China: Pinus massoniana, Connighamia lanceolata, Mytilaria laosensis, Castanopsis hystrix, Michelia macclurei, with primary focus on the effects of environment on the understory and soil microbial communities. The purpose of the study was to gain differences of the composition and diversity of understory communities and soil microbial communities between this five forests, and systematically understanding the limited factors of diversity of them under southern subtropical of China and to propose some theoretical basis for formulating forest management strategies, biodiversiy maintaining, vegetation recovery and soil structure improvement.The community characteristics of understory and soil microbial of the five forests were investigated where the forests’ages, management strategies, slope position and gradient within the study area are the same, by setting standard plots, investigating species and collecting samples. By means of the methods of one-way ANOVA, Pearson correlation analysis, Redundancy analysis (RDA) as well as Partial redundancy analysis (PRDA), and partitioning of variance of habitat and biotic factors, the differences of understory and soil microbial communities as well as the effects of canopy structure and site between the five forests plant were examined.Major results are summarized as follows:1. In shrub layer, the vegetation biodiversity of Coniferous forests (Pinus massoniana, Connighami lanceolata) is higher than broad-leaved forests’ (Mytilaria laosensis, Castanopsis hystrix, Michelia macclurei); however, no significant difference in the vegetation biodiversity of herb layer between the five forests. In addition, the shrub layer’s vegetation biodiversity is positive related with the herb layer’s.2. The factors affecting distribution of shrub layer falls into three categories:(1) index that reflects the terrain (altitude); (2) indexes that expresses characteristics of tree layer (forest type, leaf area index, mean foliage inclination angle, transmission coefficient and forest density); (3) soil property (soil organic carbon, soil total potassium, soil available potassium, soil carbon-nitrogen ratio, pH, soil permeability). Among these factors, biotic factors in terms of canopy explain more variances than habitat factors in terms of soil property.3. The factors affecting distribution of herb layer are the same with these in shrub layer except forest type. Moreover, the limiting factors and community composition differ from coniferous forests to broad-leaved forests. Among these factors, habitat factors in terms of altitude and soil property explain little more variances in the composition of herb layer than biotic factors in terms of canopy.4. Among the five experimental plantations, soil microbial biomass in coniferous forests is higher than broad-leaved forests significantly, and the same as these in bacteria, actinomycete and protist. Soil microbial PLFA percent of bacteria, gram negative bacteria and protist in broad-leaved forests are higher than those in coniferous forests.5. The factors affecting distribution of soil microbial are forest type, forest density, leaf area index, mean foliage inclination angle, transmission coefficient, soil carbon-nitrogen ratio, soil available potassium, soil moisture and fine-root biomass. Among the factors affecting distribution of soil microbial, biotic factors in terms of canopy explain much more variances in the composition of soil microbial than habitat factors in terms of soil property.