鄱阳湖湿地土壤酶及微生物生物量的剖面分布特征

为探明淡水沼泽湿地土壤微生物功能活性随土壤剖面深度的变化，以鄱阳湖区内典型的苔草湿地土壤为研究对象，选择剖面深度为1 m共5层(0~20、>20~40、>40~60、>60~80、>80~100 cm)的土壤，对土壤酶Bglu(β-葡萄糖苷酶)、NAG(乙酰氨基葡萄糖苷酶)、Bxyl(β-木糖苷酶)、Phos(酸性磷酸酶)、Phox(酚氧化酶)、Pero(过氧化物酶)]活性、w(MBC)(微生物生物量碳含量)和w(MBN)(微生物生物量氮含量)及土壤理化性质进行研究.结果表明，代表微生物功能活性的土壤酶和w(MBC)、w(MBN)均随着剖面深度的增加而逐渐降低，表层(0~20 cm)土壤中的酶活性和w(MBC)、w(MBN)均显著高于深层土壤.值得注意的是，不同土壤酶活性随着剖面深度的变化规律不一，但总体酶活性在土壤深度为>40~60 cm时达到稳定，并且仍都具有较高活性；表层土壤中w(MBC)为65.58~161.90 mg/kg，w(MBN)为7.39~16.28 mg/kg，二者占所研究剖面土壤总微生物碳氮含量的51%~69%.进一步的相关性分析发现，土壤微生物功能特性与有机质AFDM(去灰分干重)、w(TOC)、w(TN)、含水量及pH存在显著的相关性，其中土壤w(TOC)、w(TN)是影响鄱阳湖湿地土壤微生物数量和活性的最主要因素.研究显示，土壤深度对湿地土壤微生物功能特性及土壤性质具有显著影响，表层土壤中微生物功能活性最高，但湿地深层土壤中仍存在大量的微生物，由微生物参与的代谢活动仍然活跃，深层土壤微生物功能特性不容忽视. 

Profile Distribution Characteristics of Soil Enzymes and Microbial Biomass in the Poyang Lake Wetland

In order to study the soil microbial function in freshwater marsh wetlands, the Poyang Lake wetland with typical Carex cinerascens community was selected as the research object. The profile soil depth was 1 m, which was divided into five layers (0-20, >20-40, >40-60, >60-80 and >80-100 cm). The soil profile distribution of soil enzyme activities (Bglu, NAG, Bxyl, Phos, Phox and Pero), microbial biomass and soil physicochemical properties were determined. The results showed that the soil enzymes w(MBC) and w(MBN), which represented microbial functional activities, decreased gradually as the soil depth increased. The soil enzyme activities and microbial biomass in surface soil (0-20 cm) were significantly higher than those in deep soil. It should be noted that the profile distributions of different soil enzyme activities varied with increasing soil depth, but the overall enzyme activity was not only stable, but also relatively high at the soil depth of >40-60 cm. Besides, w(MBC) in the surface soil was 65.58-161.90 mg/kg, and w(MBN) was 7.39-16.28 mg/kg, accounting for 51%-69% of the total contents of MBC and MBN in the soil profile. In addition, correlation analysis showed that soil microbial functional characteristics were significantly related to AFDM, w(TOC), w(TN), soil moisture and pH. Among them, w(TOC) and w(TN) were the two most important factors affecting the soil microbial biomass and activity in the Poyang Lake wetland. These results indicated that soil depth had significant effects on both soil microbial functional characteristics and soil physicochemical properties. Our findings suggest that although the microbial activity in surface soil was highest, a large number of microorganisms still existed in the deep soil, and their metabolic activities were also active. Therefore, the microbial functional characteristics in deep soil should be explored in future work.