亚热带区4种林地土壤微生物生物量碳氮磷及酶活性特征

在位于亚热带丘陵区的长沙县大山冲林场选取地域毗邻、环境条件(立地、土壤、气候)基本一致的杉木人工林(CL)和3种次生林:马尾松-柯(又名石栎)针阔混交林(PM-LG)、南酸枣落叶阔叶林(CA)、柯-青冈常绿阔叶林(LG-CG),每种林地随机设置5个20 m×20 m的样地,分别采集表层(0—15 cm)和亚表层(15—30 cm)土壤样品,测定土壤微生物生物量碳(B_C)、氮(B_N)、磷(B_P)和蔗糖酶(INV)、脲酶(URE)、酸性磷酸酶(ACP)、过氧化氢酶(CAT)活性,分析4种林地土壤微生物生物量和酶活性及其与土壤化学性质的关系。结果表明:表层和亚表层土壤B_C、B_N、B_P和ACP活性依次为:CA LG-CG PM-LG CL,INV和URE活性依次为:LG-CG CA PM-LG CL,CAT活性依次为:CA PM-LG LG-CG CL,说明森林植被恢复对土壤微生物生物量和酶活性有明显的促进作用。通径分析表明,土壤B_C、B_N、B_P的直接影响因素和主要影响因素分别为SOC和TN/TP,TN和TN/TP,TP和SOC/TP,而TN/TP与B_C之间,TN与B_N之间具有较强的负相关;INV、ACP活性的直接影响因素主要是TN、TN/TP,其中TN/TP与INV、ACP活性具有较强的负相关;URE、CAT活性分别为B_P/TP和B_P,B_C/SOC和SOC,其中B_P与URE活性具有较强的负相关,B_C/SOC、SOC两者与CAT活性具有较强的正相关。此外,土壤B_C、B_N、B_P以及INV、URE、ACP、CAT活性的剩余余项通径系数较低,说明土壤化学性质对土壤微生物生物量,以及土壤化学性质和微生物生物量对土壤酶活性具有较大的影响。土壤B_C、B_N、B_P之间及其与土壤酶活性呈显著正相关。

Characteristics of soil microbial biomass carbon, nitrogen, phosphorus and enzyme activity in four subtropical forests, China

We selected four forest types, comprising of Cunninghamia lanceolata plantation (CL), Pinus massoniana-Lithocarpus glaber coniferous-broad leaved mixed forest (PM-LG), Choerospondias axillaris deciduous broad leaved forest (CA) and Lithocarpus glaber-Cyclobalanopsis glauca evergreen broad-leaved forest (LG-CG) in Changsha County, Hunan Province, in a mid-subtropical hilly region of China. Five permanent plots (20 m×20 m) were randomly established in each forest type. Soil samples (0-30 cm) were collected and divided into two layers (0-15 and 15-30 cm). Soil microbial biomass carbon (B_C), nitrogen (B_N), phosphorus (B_P) and activity of Invertase (INV), urease (URE), acid phosphatase (ACP), catalase (CAT) were measured, and variations of soil microbial biomass and enzyme activity and the relationship between soil microbial biomass, enzyme activity and chemical properties were studied. The results showed:(1) soil B_C, B_N and B_P, ACP activities were in the order as follows:CA > LG-CG > PM-LG > CL, both INV and URE activities were in the order as follows:LG-CG > PM-LG > CA > CL, and CAT activity ranked in the order of CA > PM-LG > LG-CG > CL, indicating that forest vegetation restoration had a significant promoting impact on the soil microbial biomass and enzyme activity. Path analysis showed that the direct and main influencing factors for B_C were SOC and TN/TP, for B_N were TN and TN/TP, and for B_P were TP and SOC/TP. However, TN/TP had a strong negative effect on B_C, and TN had a strong negative effect on B_N. The direct influencing factors for both INV and ACP activities were TN and TN/TP, of which TN/TP showed a strong negative effect on both INV and ACP activities. The direct influencing factors for URE were B_P/TP and B_P, of which B_P showed a strong negative effect on URE activities, and those for CAT were B_C/SOC and SOC, and also both had major positive effect on CAT. Furthermore, the residual path cofficients of soil B_C, B_N, B_P, in addition to INV, URE, ACP, CAT activity were small, impying soil chemical properties had a great influence on soil microbial biomass, and soil chemical properties and microbial biomass had a great influence on soil enzyme activity. Significant positive correlations were found between B_C, B_N and B_P, and between soil microbial biomass and soil enzyme activity.