天宝岩长苞铁杉林倒木接触处土壤酶活性变化及其环境效应

Soil enzyme activities under fallen logs and their environmental gradient analysis in the Tsuga longibracteata forest,Tianbaoyan National Nature Reserve,China

倒木是森林生态系统中重要的结构性和功能性成分,但分解过程十分缓慢,目前有关土壤生物学特性对其分解影响机制的研究甚少。通过分析环境因子对选择天宝岩国家级自然保护区长苞铁杉林内倒木接触处土壤酶活性的影响,探讨酶活性对倒木分解机制、土壤进程的影响及特定酶活性的时空分布格局。研究结果表明:天宝岩长苞铁杉林内倒木接触处土壤酶活性的变异系数属中高等变异程度,纤维素分解酶活性受环境影响最大,蛋白酶受影响最小;倒木的覆盖有利于提高土壤酶活性,尤其是显著地提高了纤维素酶活性,蛋白酶及脲酶活性随腐烂等级升高而降低,纤维酶活性呈升高趋势;在所有环境因子中,土壤基质环境对土壤酶活性的解释量最大,表明化学基质环境对土壤酶活性的影响不容忽视,土壤酶活性随土壤SOC、TN含量的增加而升高,随海拔升高而降低,越往南坡,土壤酶活性越高。研究揭示倒木分解与土壤酶活性之间相互促进、相互制约,倒木的存在对驱动森林生态系统的碳循环有重要意义。

Fallen logs are essential structural and functional components of the forest ecosystem, but the decomposition of fallen logs is very slow. Until recently, there has been a lack of knowledge about the effect of fallen logs on soil biological properties. The objective of this study was to determine the temporal and spatial distribution patterns of soil enzyme activities under fallen logs and how they were influenced by environmental variables during log decomposition in the Tianbaoyan National Nature Reserve. A multivariate analysis was performed to investigate the connections between environmental variables and soil enzyme activity. This study took place in Tsuga longibracteata forest, which is in the Tianbaoyan National Nature Reserve, Fujian Province, China. In the forest, the coefficient of variance for soil enzyme activity shows a high degree of variation. The cellulase spatial distribution pattern showed the greatest change, whereas changes to protease, urease, and invertase activities were lower. The increase in decay class caused a decreasing trend in protease and urease activities, but cellulase activity increased. Soil enzyme activities were positively associated with soil organic carbon （SOC） and total nitrogen （TN）. Among the environmental variables, soil chemical properties had the greatest effect on soil enzyme activities, which suggested that soil chemical properties should be taken into account when assessing the effect of fallen logs on soil enzyme activity. These activities were positively associated with TN, SOC, elevation, and slope. We identified the interactive relationship between fallen logs and soil enzyme activities and showed that the presence of fallen logs plays an important role in forest C recycling.