喀斯特峰丛洼地不同植被类型土壤微生物量碳氮磷和养分特征

  目的  探讨桂西北喀斯特峰丛洼地不同植被类型的土壤理化性质和微生物碳(MBC)、微生物氮（MBN）、微生物磷（MBP）含量的变化特征及它们之间的关系。  方法  利用生态化学计量方法和Pearson相关性分析方法研究不同植被类型和土层深度对土壤MBC、MBN、MBP含量和土壤养分含量分布特征的影响。  结果  （1）不同植被类型土壤养分含量和MBC、MBN、MBP含量依次为次生林 > 灌木 > 灌草 > 草地 > 耕地；土壤养分垂直分布表现为随着土层深度加深而下降，不同土层间土壤有机碳（SOC）、全氮（TN）、全磷（TP）含量差异显著，土壤MBC、MBN和MBP含量在不同植被类型和不同土层间差异显著，均表现为MBC > MBN > MBP。（2）不同植被类型土壤MBC/SOC和MBP/TP的值较小，MBN/TN的差异较大。不同植被类型的土壤MBC/MBN差异显著，MBC/MBP变化范围较大，MBN/MBP表现为次生林 > 灌草 > 灌木 > 草地 > 耕地。（3）土壤MBC和MBN与SOC、TN、速效氮和速效钾呈显著或极显著正相关，与土壤容重、pH值表现出不同程度的负相关，表明植被恢复过程中土壤MBC和MBN可作为衡量土壤养分的敏感性指标。  结论  不同植被类型的土壤微生物生物量碳氮磷、养分含量和化学计量特征有明显的表聚效应，随着植被的正向演替，土壤结构、养分和微生物群落功能得到显著提高。

Characteristics of Soil Microbial Biomass Carbon,Nitrogen and Phosphorus,and Nutrients in Different Vegetation Types in Karst Peak-cluster Depression

  Objective  The soils with different vegetation types in karst peak-cluster depression in northwest Guangxi were selected as the research object to study the characteristics of soil physical and chemical properties, microbial carbon (MBC), nitrogen (MBN) and phosphorus (MBP) contents and their relationship under different vegetation types.   Method  Ecological stoichiometry and Pearson correlation analysis were used to study the effects of different vegetation types and soil depth on soil MBC, MBN, MBP and nutrient contents.   Result  (1) Soil nutrients, MBC, MBN and MBP contents in different vegetation types were in the order of secondary forest > shrub > shrubby > grassland > cropland. The vertical distribution of soil nutrients showed a decrease with the depth of soil layer, and the contents of soil organic carbon (SOC), total nitrogen (TN) and total phosphorus (TP) differed significantly among different soil layers. And the MBC, MBN and MBP contents differed significantly among different vegetation types and different soil layers, with the order of MBC > MBN > MBP. (2) The values of soil MBC/SOC and MBP/TP were smaller for different vegetation types, and the differences of MBN/TN were larger. The differences in soil MBC/MBN of different vegetation types were significant, and the range of MBC/MBP variation was large, with MBN/MBP showing secondary forest > scrub > shrub > grassland > cropland. (3) Soil MBC and MBN were significantly correlated with SOC, TN, TP, available nitrogen and available potassium, and showed negative correlations with soil bulk density and pH, indicating that soil MBC and MBN could be used as sensitive indicators of soil nutrients.  Conclusion  There is a significant epistatic effect of carbon, nitrogen, phosphorus, nutrient content and stoichiometric characteristics of soil microbial biomass in different vegetation types, and soil structure, nutrients and microbial community functions are significantly improved with the positive vegetation succession.