干热河谷区泥石流滩地不同景观类型土壤与微生物量C、N、P生态化学计量特征

生态化学计量是研究生态系统元素平衡与评价地球化学循环的重要方法，明确泥石流滩地不同景观类型下植物群落与土壤和微生物化学计量特征对揭示泥石流滩脆弱生态系统的物种营建机制与植被生态修复具重要意义。选择泥石流滩地设置撂荒耕地、荒滩地、无水溪沟和有水溪沟4种景观类型，调查其物种组成、植物群落特征以及土壤和微生物量碳(C)、氮(N)、磷(P)及其生态化学计量特征，探讨了泥石流滩地植被分布规律，并通过多样性指数、冗余分析和单因素方差分析等方法对植物群落和土壤因子进行比较分析。研究结果表明：(1)物种数在4种景观类型中表现为荒滩地>无水溪沟>撂荒耕地>有水溪沟，Margalef丰富度指数表现为无水溪沟>荒滩地>撂荒耕地>有水溪沟，Simpson优势度指数表现为撂荒耕地>有水溪沟>无水溪沟>荒滩地，且有水溪沟的植物群落密度、平均高度、盖度以及地上生物量均显著高于其它景观类型。(2)有水溪沟土壤N、P含量显著高于其他景观类型土壤；撂荒耕地土壤C含量最少，显著低于其他景观类型土壤；土壤C∶N、C∶P表现为荒滩地>无水溪沟>有水溪沟>撂...

C: N: P ecological stoichiometry characteristics of soil and microbes of different landscape types in debris flow beach of dry-hot valley

Ecological stoichiometry is a significant method to study the element balance and evaluation of geochemical cycle. Defining the relation of plant community characteristics and the ecological stoichiometry characteristics of the soil and microbial under different landscape types is of great significance to reveal the species coexistence mechanism and vegetation ecological restoration of fragile ecosystem in debris flow beach. In this paper, four landscape types (fallow, barren beach, anhydrous gully, and water gully) were selected as research objects. Species composition, plant community characteristics, carbon (C), nitrogen (N), phosphorus (P), and its ecological characteristics of soil and microbial biomass under different landscape types were analyzed. By means of diversity index, redundancy analysis and one-way ANOVA, the comparative analysis of plant community and soil factors was carried out to discuss the distribution law of vegetation in debris flow beach. The results showed that:(1) the species numbers of the four landscape types were barren beach > anhydrous gully > fallow > water gully. Margalef richness index showed the order of anhydrous gully > barren beach > fallow > water gully. Simpson dominance index showed that fallow > water gully > anhydrous gully > barren beach. The plant community density, average height, coverage and aboveground biomass of water gully were significantly higher than those of other landscape types. (2) Soil N and P contents in water gully were significantly higher than those in other landscape types. The C content of fallow soil was the lowest, significantly lower than that of other landscape soils. Soil C:N and C:P showed barren beach > anhydrous gully > water gully > fallow. There was no significant difference in soil N:P among the landscape types. (3) Microbial biomass carbon (MBC) showed as follows:anhydrous gully > barren beach > water gully > fallow. The soil MBC:microbial biomass nitrogen (MBN) and MBC:microbial biomass phosphorus (MBP) of barren beach were significantly higher than those of gully landscape. MBN, MBP and MBN:MBP had no significant differences among different landscape types. (4) The correlations between plant and soil, microbial C, N, P contents and stoichiometric characteristics were different under different landscape types, indicating that nutrient flow and transformation between plant and soil had important effects on plant community characteristics. Soil C:N, MBP, N, MBC and P had significant effects on plant community characteristics. Simpson dominance index was positively correlated with soil P and MBP. There was a significantly positive correlation between plant community coverage and soil N, P and MBP, and a significantly negative correlation between plant community coverage and soil C:N, C:P and MBP. The aboveground biomass was positively correlated with soil N, P and MBP. There were significantly positive correlations between soil C content and MBC, MBN, MBC:MBN, soil C:P, MBN:MBP ratios, indicating that the changes of plant community, soil and microbial ecological stoichiometry in the fragile ecosystem of debris flow beach were mutually influenced.