不同林龄油茶林土壤酶化学计量特征及微生物养分限制因素

Variations in soil enzyme stoichiometry and microbial nutrient limitations in Camellia oleifera plantations with different ages

林龄的变化引起土壤性质和微生物群落的改变,探明林龄对油茶林土壤酶化学计量特征及微生物养分限制的影响,对油茶林的养分管理具有重要意义。本研究以亚热带红壤地区4个林龄段油茶林(<10年、15~25年、30~50年、>60年)为对象,研究土壤酶化学计量和微生物养分限制对林龄变化的响应以及影响油茶林微生物养分限制的重要途径。结果表明:与<10年林龄段油茶林相比,15~25年林龄土壤酶活性C∶N显著提高,但酶活性N∶P显著降低。微生物生物量碳(MBC)、微生物生物量氮(MBN)、微生物生物量磷(MBP)随林龄增加呈现先降低后升高趋势;MBN、MBN∶MBP在<10年林龄显著高于30~50年林龄;30~50年、>60年林龄MBC∶MBN显著高于<10年和15~25年林龄。冗余分析结果显示,土壤养分、微生物生物量及其化学计量解释了酶化学计量变化的92.4%。偏最小二乘路径建模分析(PLS-PM)表明,土壤有机碳(SOC)对微生物的C限制有总的正效应;MBN、MBN∶MBP、MBC∶MBP和SOC、全氮对微生物的P限制有总的负效应,土壤C∶N对微生物的P限制有总的正效应,微生物的C限制与P限制呈显著正相关。随林龄增加,微生物养分由N、P限制(<10年)向C、P限制(15~25年、30~50年、>60年)转变。

The alteration of stand age instigates modifications in soil properties and microbial communities.Understanding the impacts of stand age on soil enzyme stoichiometry and microbial nutrient limitations in Camellia oleifera plantation is crucial for nutrient management.Taking C.oleifera plantation across four age groups(<10 a,15-25 a,30-50 a,>60 a)in a subtropical red soil region as test objects,we examined the response of soil enzyme stoichiometry and microbial nutrient limitations to change in stand age and analyzed the pathways for such responses.The results showed that,compared to that of stand age<10 a,enzyme C:N in the 15-25 a was increased and enzyme N:P was significantly reduced.Microbial biomass carbon(MBC),microbial biomass nitrogen(MBN),and microbial biomass phosphorus(MBP)exhibited a trend of initially decreasing and then increasing with stand age.MBN and MBN:MBP were significantly higher in the<10 a compared to that in the 30-50 a.MBC:MBN was significantly higher in the 30-50 a and>60 a compared to the<10 a and 15-25 a.Results of redundancy analysis revealed that soil nutrients,microbial biomass and their stoichiometry explained 92.4%of the variations in enzyme stoichiometry.Partial least squares path modeling(PLS-PM)results demonstrated that soil organic carbon(SOC)had a positive effect on microbial C limitation;MBN,MBN:MBP,MBC:MBP,SOC,and total nitrogen had a nega-tive overall effect on microbial P limitation,whereas soil C:N had a positive overall effect on microbial P limitation.There was a significant positive correlation between microbial C and P limitations.With increasing stand age,microbial nutrient limitation shifted from N and P limitation(<10 a)to C and P limitation(15-25 a,30-50 a,>60 a).