川西亚高山不同森林类型土壤酶活性对短期凋落物输入量变化的响应

Response of soil enzyme activities to short-term litter input in different types of forest in subalpine western Sichuan

凋落物输入是生态系统物质循环和能量流动的重要环节,在维持亚高山森林的"自肥"机制及生态系统结构和功能等方面具有不可替代的作用.为进一步了解川西亚高山森林土壤物质循环过程,以该地区典型森林为对象,通过进行凋落物输入控制试验,研究3种森林类型(阔叶林、针阔混交林和针叶林)不同时期(添加时间)凋落物输入变化对土壤碳(C)、氮(N)和磷(P)分解相关的酶活性及其化学计量比的影响.结果显示:3种森林类型中凋落物输入对土壤酶活性的影响不显著,而不同林型和凋落物输入时间则显著影响了土壤酶活性.凋落物处理1.5年时期,在凋落物输入处理中,阔叶林的β-葡萄糖苷酶和纤维二糖水解酶的酶活性显著高于针阔混交林(2.69和2.73倍)和针叶林(1.87和1.47倍);而在凋落物去除处理中,针叶林中的酸性磷酸酶活性则显著大于阔叶林(1.72倍)与针阔混交林(1.66倍).相关性分析表明,土壤含水量以及C、N含量是影响酸性磷酸酶、β-葡萄糖苷酶和纤维二糖水解酶变化的主要因素,而多酚氧化酶和过氧化物酶主要受到土壤pH以及土壤硝态氮含量的影响.根据生态酶化学计量理论,本研究的土壤酶化学计量碳氮比(C:NEEA)均低于全球平均值,而土壤酶化学计量碳磷比(C:P_(EEA))和土壤酶化学计量氮磷比(N:P_(EEA))均高于全球平均值,表明该区域N转化酶活性较高,处于相对N限制的区域.本研究表明在养分循环较慢的川西亚高山地区,短期凋落物的输入对土壤酶活性的影响较为缓慢,但不同凋落物组成(林型)对土壤酶活性的影响不同,关于土壤酶活性对于凋落物输入的响应还有待长期研究.

Litter input is an important link between the material cycle and energy flow of the subalpine forest and plays an irreplaceable role in maintaining the"self-fertilization"mechanism,structure,and function of this ecosystem.Understanding the effects of litter on soil enzymatic activity is helpful for improving our knowledge of the forest material cycle.To further analyze the process of soil material cycling in the subalpine forest of western Sichuan,we conducted a 2-year experiment in a broad-leaved forest,mixed coniferous and broadleaved forest,and coniferous forest to assess the effects of litter input on the dynamics of soil C,N,and P decomposition-related enzymatic activities and stoichiometric ratios.The results showed that in the three forest types,litter input had no significant effect on soil enzymatic activities,whereas forest type and litter input time significantly affected soil enzymatic activities.In the litter input experimental treatment,theβ-glucosidase and cellobiohydrolase enzyme activities of broad-leaved forests were significantly higher than those of mixed coniferous and broad-leaved forests(2.69 and 2.73 times,respectively)and coniferous forests(1.87 and 1.47 times,respectively).In the litter removal experimental treatment,the acid phosphatase activity in coniferous forest was significantly higher than that in broad-leaved forest(1.72 times)and mixed coniferous and broadleaved forest(1.66 times).Correlation analysis results showed that the soil water,C,and N contents were the primary factors affecting the changes in acid phosphatase,β-glucosidase,and cellobiohydrolase,while polyphenol oxidase and peroxidase were primarily affected by soil pH and soil nitrate content.The ratio of specific C:N acquisition activity in this study was lower than the global average,whereas that of C:P and N:P acquisition activities was higher than the global average,indicating that the enzymatic activity of N-invertase in this region is relatively high and that there is a relative N limitation in the region.The effect of short-term litter input on soil enzymatic activity was relatively slower in the subalpine region of western Sichuan,where the nutrient cycle is slower.However,different litter compositions(forest types)had different effects on soil enzymatic activity.The response of soil enzymatic activities to litter input requires further long-term research.