川西亚高山云杉天然林和人工林土壤酶化学计量特征比较

Soil enzyme stoichiometric characteristics of natural forest and plantation of subalpine spruce in western Si⁃chuan

土壤酶以及化学计量比是表征土壤养分可用性和微生物养分限制的关键指标。然而,对川西亚高山天然林转换为人工林后土壤酶活性和化学计量比的变化特征及其关键驱动因素尚不清晰。本研究以川西亚高山云杉天然次生林和人工林为对象,测定了两种林分的土壤理化性质和酶活性。结果表明:(1)天然林土壤碳氮比(C∶N)显著低于人工林(P<0.05),其土壤碳磷比(C∶P)和氮磷比(N∶P)则均显著高于人工林土壤(P<0.05);(2)天然林的酶碳氮比(C∶N_(EEA))和酶碳磷比(C∶P_(EEA))显著高于人工林,而酶氮磷比(N∶P_(EEA))却显著低于人工林(P<0.01);人工林的碳质量指数CQI1和CQI2显著高于天然林(P<0.05),而矢量长度和矢量角度显著低于天然林(P<0.01);(3)天然林土壤微生物受到了一定程度的碳、磷限制,人工林土壤微生物则受氮严重限制;(4)冗余分析结果表明,全氮是影响酶化学计量比的主要因素。以上研究结果表明,在本区域内人工林土壤养分管理中,需充分考虑微生物对氮素的需求。

Soil enzymes and stoichiometry are key indicators for soil nutrient availability and microbial nutrient limitation.However,the variations and key driving factors of soil enzyme activities and stoichiometric ratios after the conversion of subalpine natural forests to plantations in western Sichuan remain unclear.In this study,we measured soil physicochemical properties and enzyme activities in a natural secondary forest and a plantation of subalpine spruce in western Sichuan.The results showed that:(1)Soil C∶N ratio of natural forest was significantly lower than that of plantation(P<0.05),while soil C∶P and N∶P ratios were significantly higher than that of plantation(P<0.05).(2)The C∶N_(EEA) and C∶P_(EEA)of natural forest were significantly higher than that of plantation,while N∶P_(EEA)was significantly lower than that of plantation(P<0.01).The carbon quality indices(CQI1 and CQI2)of plantation were significantly higher than natural forest(P<0.05),while vector length and vector angle were significantly lower than natural forest(P<0.01).(3)Soil microorganisms were limited by C and P in the natural forest,but by N in the plantation.(4)The results of redundancy analysis showed that soil total N was the main factor affecting the enzyme stoichiometric ratio.Our results suggest that the N requirements of microorganisms should be fully considered in soil nutrient management of plantations in this region.