中国东部南北样带典型针叶林土壤酶活性分布格局

Pattern of enzyme activities of typical coniferous forest soils along the NorthSouth Transect of Eastern China

选取中国东部南北样带不同气候区(寒温带、温带和亚热带)的针叶林作为研究对象,分析了多酚氧化酶、过氧化物酶、几丁质酶以及β-葡萄糖苷酶活性的变化。结果表明,土壤溶解性有机碳(DOC)、微生物生物量碳(MBC)、微生物生物量氮(MBN)含量从北到南依次减小,寒温带显著高于亚热带;土壤p H值在3个气候区差异显著,温带最高,亚热带最低。分解木质素的多酚氧化酶和过氧化物酶活性不存在显著性差异;而与氮循环密切相关的几丁质酶活性表现为温带显著高于寒温带和亚热带;与碳循环密切的β-葡萄糖苷酶活性在温带最高,并显著高于亚热带地区。逐步回归分析表明,土壤MBN与p H值影响土壤几丁质酶活性,而土壤β-葡萄糖苷酶活性主要受p H的控制。研究认为,在中国东部南北样带针叶林中,土壤几丁质酶和β-葡萄糖苷酶活性存在显著性差异,而p H与MBN可能是影响土壤酶活性的主要因素。

Soil organic carbon（ SOC） is the largest terrestrial pool of carbon,and the amount of carbon in soils represents about two thirds of total ecosystem. Therefore,any change in the size and turnover rate of SOC pools will potentially alter the atmospheric CO2 concentration and the subsequent global climate. Soil enzymes are involved in a series of catalyzing reactions and play pivotal roles in litter and soil organic matter decomposition as well as nutrient cycling in terrestrial ecosystems. Soil enzyme activity can be used as a proxy for plant and microbial substrate availability,the interference between soil ecosystem and external environment,and microbial community structure and metabolic capabilities. Therefore,the determination of soil enzyme activities is a powerful tool for understanding soil carbon and nitrogen biogeochemical processes and their responses to climate change. Soil enzyme activity has been a frontier of forest ecology research and has been widespread concern. Unfortunately,most of the studies to date have been limited to a single forest biome or a single forest site,and few studies concern the pattern and controlling factors of soil enzyme activity at a terrestrial transect scale.North-South Transect of Eastern China（ NSTEC） is the fifteenth standard transect established by International GeosphereBiosphere Program（ IGBP） in 2005 and is mainly driven by heat,followed by precipitation. It covers almost all forest typesfrom boreal forest to tropical rain forest,which provides an ideal tool to investigate the pattern and environmental control of soil enzyme activities in the boreal,temperate and tropical forest biomes. In the past decade,many studies were conducted to measure the main factors affecting the pattern of SOC storage and soil-atmosphere exchange of greenhouse gases in the typical forests along the NSTEC. However,little information is available on the pattern of soil enzyme activities involved in soil carbon and nitrogen cycles and they relate to soil microbial biomass at a large spatial scale. In this study,the typical coniferous forests distributed in the cold-temperate,temperate and subtropical climatic zones were selected along the NSTEC. The activities of polyphenol oxidase,peroxidase,chitinase and β-glucosaccharase,soil dissolved organic carbon（DOC）,microbial biomass carbon（ MBC） and microbial biomass nitrogen（ MBN） as well as soil pH in the three coniferous forest soils were measured. The results showed that soil DOC,MBC,and MBN contents tended to decrease from north to south,and they were higher in the cold-temperate forest soils than in the subtropical forest soils. There was a significant difference in the soil pH values among the three coniferous forests,following the order cold-temperate temperate subtropical forests. Also,no significant differences were found in the soil polyphenol oxidase and peroxidase activities among the three typical coniferous forests. In contrast,the soil chitinase activity involved in soil nitrogen cycle was significantly higher in the temperate forest than in the cold-temperate and subtropical forests,and the soil β-glucosaccharase activity in the temperate forest was also significantly higher than that of the subtropical forest. Stepwise regression analysis showed that the soil chitinase activity was closely associated with soil MBN content and soil pH value,and the soilβ-glucosaccharase activity was significantly and positively related to soil pH value. Our results suggest that soil celluloseand chitin-degrading enzymes（ i. e.,chintinase and β-glucosaccharase） sensitively respond to climate zone. Soil MBN content and pH value are the main factors controlling soil enzyme activities of coniferous forests along the NSTEC.