疏伐措施对大熊猫廊道云杉林土壤养分特征及微生物碳氮的短期影响

Short-term effects of thinning on soil nutrient characteristics and microbial biomass carbon and nitrogen in Picea asperata forest of giant panda corridor

以大熊猫廊道云杉人工林为研究对象,对次生低效云杉林进行了透光疏伐和林下植被改造,分析了疏伐1a后云杉林不同土层养分和微生物碳氮特征.结果表明:与未疏伐的云杉林相比,疏伐后云杉林总养分有所下降,但有效养分增加,且土壤微生物碳氮也增加.疏伐后表层土土壤有机碳(TOC)、全氮(TN)和全磷(TP)分别下降了20.65%、20.73%和75.72%,而硝态氮(NN)、铵态氮(AN)、速效钾(AK)和有效磷(AP)分别升高了40.70%、13.26%和37.20%和43.30%,土壤微生物碳(MBC)、土壤微生物氮(MBN)、微生物碳熵(qMBC=w(MBC)/w(TOC))、微生物氮熵(qMBN=w(MBN)/w(TN))分别升高了27.23%、25.24%和42.42%、28.93%,亚表层土也具有相似的结果.疏伐后表土层碳磷比(C/P=w(TOC)/w(TP))和氮磷比(N/P=w(TN)/w(TP))大幅度升高,而亚表层碳氮比(C/N=w(TOC)/w(TN))和微生物碳氮比(MBC/MBN=w(MBC)/w(MBN))显著降低.MBC、MBN与各有效养分呈正相关,MBC与TN、TOC无相关性,MBC/MBN与TN、TOC、AN、AK、C/N呈显著负相关.疏伐改造一方面提高了云杉人工林土壤有效养分和微生物量,但另一方面可能导致土壤有机质有所不足,在后续措施中需要加强林地特别是林下层对有机质的补偿作用.

To analyze the characteristic of soil nutrients and microbial biomass carbon and nitrogen in different soil layers after thinning and removing for one year,Picea asperata forest of giant panda corridor was chosen.Compared with the non-thinning forest,the total nutrients of the thinning forest decreased,but the effective nutrients increased,and the soil microbial carbon and nitrogen also increased,after thinning,TOC,TN and TP in topsoil decreased by 20.65%,20.73%and 75.72%,while NN,AN,AK and AP increased by 40.70%,13.26%,37.20%and 43.30%,MBC,MBN,qMBC and qMBN increased by 27.23%,25.24%,42.42%and 28.93%respectively,the results are similar to the subsurface soil;The C/P and N/P of the topsoil layer increased significantly,while the C/N and MBC/MBN of the sub-topsoil layer decreased significantly;MBC and MBN are positively correlated with available nutrients,MBC is not correlated with TN,TOC,and MBC/MBN is correlated with TN,TOC,AN,AK,C/N showed a significant negative correlation.Thinning improved the soil available nutrients and microbial biomass,however,it may lead to insufficient soil organic matter of the P.asperata forest.It is necessary to strengthen the compensation effect of P.asperata forest,especially the under-story,by applying organic matters in the following measures.