改变碳输入对太岳山油松林土壤酶活性的影响

Effects of carbon input changes on soil enzyme activities in a Pinus tabulaeformis forest at the Taiyue Mountain

土壤酶是土壤微生物作用于土壤环境的媒介,其活性对土壤环境的变化十分敏感,因此测定土壤酶活性对了解土壤微生物群落功能与环境因子的关系具有重要意义.为了解碳输入变化对土壤酶活性的影响,本文以山西太岳山油松(Pinus tabulaeformis)天然林和人工林为研究对象,自2009年7月开始进行对照(无人为干扰,CK)、去凋(去除凋落物,LR)、切根去凋(切断根系并去除凋落物,LRNR)3种处理,于2012年7、9月和2013年5月采集表层0-20 cm的土样,测定了多酚氧化酶(Polyphenol oxidase)、过氧化物酶(Peroxidase)、纤维素酶(Cellulase)、蔗糖酶(Invertase)、脲酶(Urease)和中性磷酸酶(Neutral phosphatase)的活性,另于2012年10月采集表层0-20 cm的土样测定土壤化学性质.结果显示:碳输入的改变对土壤酶活性影响显著,去凋处理和切根去凋处理均显著降低了土壤碳、氮含量(P<0.05),并且显著抑制了土壤纤维素酶、蔗糖酶、脲酶、中性磷酸酶等水解酶的活性(P<0.05),但对多酚氧化酶和过氧化物酶等氧化酶的影响不显著(P>0.05).切根去凋处理对水解酶的抑制作用大于去凋处理,并略微提高了土壤过氧化物酶活性.另外在天然林中蔗糖酶活性的下降比人工林更为显著,而人工林中纤维素酶活性的下降比天然林更显著.研究表明:油松天然林中的土壤微生物群落功能倾向于分泌蔗糖酶,而油松人工林中的土壤微生物群落功能倾向于分泌纤维素酶.土壤酶活性的变化说明,在山西油松林,碳输入的减少会降低参与有机质降解的土壤酶活性,而对参与腐殖质合成的土壤酶活性没有显著影响.

Activities of soil enzymes are very sensitive to changes in the soil environment. Therefore, determination of soil enzyme activity had great significance in understanding the relationships between soil microbial community function and environmental factors. This paper aimed to study the effects of carbon input variation on the soil enzyme activities. Three treatments involving a） both litter and root exclusion（LRNR）, b） only litter exclusion（LR）, and c） a control（CK） were installed in the plantation and natural forest of Pinus tabulaeformis at the Taiyue Mountain of Shanxi Province China since July 2009.Each treatment comprised three replicate plots of 2 m × 2 m. Soil samples were collected from 0-20 cm in July, September 2012 and May 2013. The activities of invertase, cellulase, peroxidase, polyphenol oxidase, urease and neutral phosphatase were determined. Soil chemical properties were determined with the 0-20 cm soil samples collected in October 2012. The results showed that changes of carbon input significantly influenced soil enzyme activities, with both LRNR and LR significantly reducing soil carbon and nitrogen content（P〈 0.05） and significantly inhibiting the hydrolase activities such as invertase, cellulase, urease and neutral phosphatase（P〈 0.05）. But these treatments did not affect oxidase such as polyphenol oxidase and peroxidase（P〈 0.05）. LRNR slightly increased soil peroxidase activity, with greater inhibition on hydrolytic enzymes than LR. The invertase activity was decreased more significantly in the natural forest than in the plantation. Yet the decrease in cellulase activity was the contrary. The results suggested that the soil microbial community tend to secrete invertase in natural forests but to secrete cellulose in plantations. Changes of soil enzyme activities showed that, in the Shanxi Pinus tabulaeformis forest, decrease of carbon input slows the soil microbial degradation of organic matter, but has no effect on the soil microbial synthesis capacity of humus.