漓江水陆交错带不同植被类型的土壤酶活性

水陆交错带是内陆水生生态系统与陆地生态系统之间的功能界面区,其包含了高地到低地直到水体的区域,是土壤有机质源、汇和转换器。土壤中有机物的分解以及营养物质的转化不仅影响到植物的生长,也对水体质量产生间接影响。土壤酶几乎参与土壤中有机物质的分解与合成的全过程,直接或间接影响着土壤一系列的生物化学反应,对生态系统的物质循环产生重要影响。不少学者围绕农田土壤、林地土壤以及湿地土壤探讨了不同植被下酶活性的变异。水陆交错带植被种类丰富,周期性的淹水条件加剧了土壤性质变异的复杂性。但目前水陆交错带不同植被类型土壤酶活性差异的研究不多。以漓江水陆交错带土壤为研究对象,对苔藓、草本和灌丛3种植被类型下的土壤溶解性化学成分、4种土壤水解酶即糖苷酶、几丁质酶、亮氨酸氨基肽酶和磷酸酶以及2种氧化还原酶即酚氧化酶和过氧化物酶的活性,以及土壤性质与酶活性之间的关系进行了研究。结果表明,苔藓植被下土壤的糖苷酶和酚氧化酶活性显著高于草本和灌丛,草本植被下土壤的过氧化物酶活性显著高于苔藓和灌丛,灌丛植被下土壤几丁质酶活性显著高于苔藓和草本,但不同植被类型的土壤亮氨酸氨基肽酶活性无显著差异。相关分析表明,土壤水分含量与糖苷酶和酚氧化酶活性呈显著正相关,而与几丁质酶和碱性磷酸酶活性呈显著负相关。土壤有机碳和易氧化碳均与糖苷酶和酚氧化酶活性呈极显著负相关,与几丁质酶活性呈显著正相关。土壤溶解性有机碳与亮氨酸氨基肽酶和酚氧化酶呈显著正相关。综合认为,水陆交错带不同种类土壤酶在不同植被类型间的差异有别,土壤水分含量和土壤有机碳显著影响土壤酶活性的变化。不同植被类型土壤酶活性的差异不仅与植被类型有关,与水陆交错带微地形以及土壤性质的空间异质性也有密切关系,需运用长期控制试验手段开展研究。

The activities of soil enzyme under different vegetation types in Li River riparian ecotones

"Riparian ecotone" refers to the functional-frontal-zone between an internal water-ecosystem and land-ecosystem, and riparian ecotones-as the sinks, sources or transformers of soil organic matter-contain the interference from the uplands, lowlands and aquatic zone. Riparian ecotones had played a critical role in regulating the conponents of chemical composition between terrestrial and aquatic zones. In addition, they have also had a significant effect on maintaining biodiversity, preventing pollutants from the land ecosystem entering the aquatic zone, and improving water quality or any other aspects. Soil offered essential nutrient substance for the growth of vegetation. The decomposition of organic matter and the transformation of nutrient substances in the soil have not only influenced the growth of vegetation but have also had an indirect effect on the quality of the water. The partial involvement of soil enzymes throughout process of soil organic matter decomposition and synthesis, has influenced all the biochemical reactions of soil, directly or indirectly, and has had a great impact on material circulation within the ecological system. Much debate has focused on the variation in soil enzyme activities with different vegetation types, e.g., farmland, forest land and wetland. Riparian ecotones have diverse vegetation types, complicated by the variation in soil properties aggravated by periodic flooding conditions. However, studies aimed at soil enzyme activity under different vegetation communities in riparian ecotones have been scare. In the riparian ecotones of the Lijiang River, soil water-soluble chemical composition, four types of soil hydrolase(glycosidase, chitinase, leucine aminopeptidase and phosphatase)and two types of oxidoreductase (phenol oxidase and peroxidase) were measured in relation to three vegetation types: mosses, herbs and shrubs. The relationship between the soil properties and enzyme activities was also studied. The results showed:(1) that the activity of soil glycosidase and phenol oxidase under mosses was significantly greater than that under herbaceous and shrubs;(2)that the soil glucosaminidase activity under shrubs was significantly higher than that under mosses and herbs;(3)that the peroxides activity under herbs was significantly higher than that under mosses and shrubs; and that there was no obvious difference in the activity of leucine amino peptidase among the three vegetation types. Among the six enzyme activities examined, soil water content was positively related to the activity of glucosidase and phenol oxidase, and negatively related to the activity of glucosaminidase and alkaline phosphatases. Soil organic carbon and readily oxidizable carbon were negatively associated with glucosidase and phenol oxidase, but positively associated with glucosaminidase. Dissolved organic carbon in soil was positively related to the activity of both glucosidase and phenol oxidase. In short, there were differences between different types of soil enzymes under different vegetation types in riparian ecotones, and soil water content and soil organic carbon significantly influenced the change in soil enzyme activities. In riparian ecotones enriching the plant diversity can accelerate soil ecological processes. The difference in soil enzyme activities under different vegetation communities was not only related to the vegetation types, but also to the micro-topography and spatial heterogeneity of the soil properties in riparian ecotones. Future research on soil enzyme activities under different kinds of vegetation types in the soil of riparian ecotones of the Lijiang River should incorporate long-term control-tests.