不同桉树混交林土壤理化性质、酚酸含量与酶活性的差异

Differences of soil physicochemical property,phenolic acid and enzyme activities in different Eucalyptus mixed plantations

【目的】研究桉树与不同阔叶树种混交对土壤理化性质、酚酸含量和酶活性的影响,分析酚酸物质与酶活性的关系,为改善桉树纯林的土壤质量、合理经营桉树人工林及适宜混交树种的选择提供参考。【方法】在广西凭祥市选择6年生桉树纯林以及桉树与豆科树种(降香黄檀、格木)、非豆科树种(红锥)的混交林作为研究对象,测定不同林分类型桉树根际与非根际土壤的理化性质(铵态氮、有机碳、全氮、硝态氮含量、pH、自然含水率)、酚酸类物质含量及酶(多酚氧化酶、脲酶、蔗糖酶、过氧化氢酶、蛋白酶)活性,并采用相关性和冗余分析方法揭示酚酸含量和酶活性的相关关系。【结果】(1)桉树混交林根际与非根际土壤的pH、自然含水率、有机碳、全氮、硝态氮、铵态氮含量均总体高于桉树纯林。(2)与桉树纯林相比,混交林桉树根际土壤酚酸物质含量升高,表现为桉树×红锥混交林(50.01μg/g)>桉树×格木混交林(38.39μg/g)>桉树×降香黄檀混交林(36.94μg/g)>桉树纯林(27.76μg/g);非根际土壤的酚酸类物质含量降低,表现为桉树纯林(21.45μg/g)>桉树×降香黄檀混交林(16.35μg/g)>桉树×格木混交林(15.50μg/g)>桉树×红锥混交林(13.52μg/g)。(3)桉树混交林根际与非根际土壤的蛋白酶、蔗糖酶、脲酶和过氧化氢酶活性均高于桉树纯林;桉树混交林根际土壤的多酚氧化酶活性总体低于纯林,而非根际土壤的多酚氧化酶活性显著高于纯林。(4)相关性和冗余分析结果表明,土壤酚酸类物质含量与酶活性具有较高的相关性,阿魏酸、对羟基苯甲酸、香草酸含量在一定程度上能够解释根际与非根际土壤间酶活性的差异。【结论】混交造林对桉树根际与非根际土壤理化性质、酚酸类物质含量和酶活性影响显著,能够增加桉树根际土壤酚酸积累,减缓非根际土壤酚酸富集,提高土壤养分和酶活性,其中红锥与桉树混交更有利于维持土壤肥力。

【Objective】The effects of mixed Eucalyptus and different broad-leaved species on soil physicochemical properties,phenolic acid content and enzyme activities were studied and the relationship between phenolic acid and enzyme activities was analyzed to provide referable evidence for improving soil quality,rational management and selection of suitable mixed tree species for Eucalyptus plantations.【Method】Six-year-old pure and mixed plantations of Eucalyptus with Castanopsis hystrix,Dalbergia odorifera and Erythrophleum fordii were selected in Pingxiang,Guangxi.Physical and chemical properties,phenolic acids content and enzyme activities of rhizosphere and non-rhizosphere soils of Eucalyptus in different stands were determined.Correlation and redundancy analysis were used to reveal the correlations between phenolic acids and enzyme activities.【Result】(1)The pH,natural water,total organic carbon,total nitrogen,nitrate nitrogen and ammoniacal nitrogen contents in rhizosphere and non-rhizosphere soil of Eucalyptus mixed plantations were higher than that of pure plantation.(2)Compared with pure forest,mixed plantations of Eucalyptus increased contents of phenolic acids in rhizosphere soil,and the contents were in the order of mixed plantation of Eucalyptus and Castanopsis hystrix(50.01μg/g)>mixed plantation of Eucalyptus and Erythrophleum fordii(38.39μg/g)>mixed plantation of Eucalyptus and Dalbergia odorifera(36.94μg/g)>pure plantation of Eucalyptus(27.76μg/g).In addition,mixed plantations of Eucalyptus reduced contents of phenolic acids in non-rhizosphere soil and the contents were in the order of pure plantation of Eucalyptus(21.45μg/g)>mixed plantation of Eucalyptus and Dalbergia odorifera(16.35μg/g)>mixed plantation of Eucalyptus and Erythrophleum fordii(15.50μg/g)>mixed plantation of Eucalyptus and Castanopsis hystrix(13.52μg/g).(3)The activities of protease,invertase,urease and catalase in rhizosphere and non-rhizosphere soil of Eucalyptus mixed plantations were higher than those in pure forest.The activity of polyphenol oxidase in rhizosphere soil of Eucalyptus mixed plantations was lower than that of pure forest,while the activity of polyphenol oxidase in non-rhizosphere soil was significantly higher than that of pure forest.(4)Correlation and redundancy analysis showed that there were high correlations between soil phenolic acids and soil enzyme activities,and contents of ferulic acid,p-hydroxybenzoic acid and vanillic acid could explain the differences in enzyme activities between rhizosphere and non-rhizosphere soils.【Conclusion】Mixed afforestation had significant effects on phenolic acids contents and enzyme activities in rhizosphere and non-rhizosphere soils of Eucalyptus plantations.Mixed afforestation could increase the accumulation of phenolic acid in rhizosphere soil,decrease the accumulation of phenolic acid in non-rhizosphere soil,and improve soil nutrients and enzyme activities.The mixed plantations of Eucalyptus and Castanopsis hystrix had more advantages in maintaining soil fertility.