连栽杉木林地土壤对其无性系幼苗土壤酶活性和酚酸类物质含量的影响

探讨杉木在连栽杉木林土壤培养下,其优良无性系根际与非根际土壤酶活性以及根际和根尖酚类物质含量的变化特征及其相互关系,揭示杉木优良无性系对不同连栽代数土壤培养的响应机理,以不同连栽代数杉木人工林土壤为培养基质,栽植杉木无性系幼苗2a后,采用抖落法取根际和非根际土壤测定相关酶活性和根际酚类物质含量,并剪取0～2cm根尖测定酚酸类物质含量。结果表明,在杉木根际土壤和非根际土壤中的脲酶、蔗糖酶、过氧化氢酶及酸性磷酸酶活性总体上随连栽代数增加呈下降的变化趋势,而多酚氧化酶活性呈上升的变化趋势。杉木优良无性系根际土壤中共鉴定出11种酚类物质,其中阿魏酸、没食子酸和咖啡酸相对含量较高,是最主要的酚类物质。没食子酸相对含量随连栽代数增加而增多,阿魏酸含量表现为先降后升,但均高于对照,而咖啡酸则表现为先升后降,其含量均低于对照,且三者在三代林中的含量均高于一代林;杉木根尖中共鉴定出8种酚类物质,其中儿茶素、奎尼酸和山奈酚相对含量较高。儿茶素含量逐代下降,二代林和三代林中其含量均高于对照;山奈酚含量逐代增加,而不同连栽代数中其含量均低于对照;奎尼酸含量表现为先升后降,而不同连栽代数中其含量均高于对照。相关性分析表明,鞣花酸、奎尼酸与酸性磷酸酶呈显著负相关,龙胆酸与酸性磷酸酶呈极显著正相关,芦丁、龙胆酸与多酚氧化酶呈显著负相关,鞣花酸与多酚氧化酶呈显著正相关,没食子酸与脲酶呈显著负相关;槲皮素、芦丁和香草酸与脲酶呈显著正相关,对香豆酸和山奈酚与蔗糖酶呈显著正相关。综上所述,杉木连栽可能会通过改变杉木根尖和根际土壤中酚类物质的积累来影响土壤酶的活性,进而影响杉木对养分的吸收利用,最终导致杉木连栽障碍的发生。

Effects of Continuous Planting on Soil Enzyme Activities and Phenolic Acid Contents in Soil and Root Tips of Cunninghamia lanceolata

The objectives of this study were to investigate the rhizospheric and non-rhizospheric soil enzyme activities,the changes of phenolic contents in rhizosphere and root tips and their relationships in different Cunninghamia lanceolata clones under various continuous cropping soil conditions,and to reveal the underlying mechanism of different C.lanceolata clones in response to various continuous cropping soils.Soils of different C.lanceolata plantations were used as the culture media.After planting the clonal seedlings of C.lanceolata for 2 years,the enzyme activities and phenolic substances in the rhizosphere and non-rhizosphere soils were determined by shaking off method,and the contents of phenolic substances in the rhizosphere were measured.The phenolic acid contents in root tips (0-2 cm) were determined.The results showed that the activities of urease,sucrase,catalase and acid phosphatase in the rhizosphere and non-rhizosphere soils generally decreased with the increase of successive generations,while opposite for polyphenol oxidase.A total of 11 phenolic compounds were identified in the rhizosphere soil,among which the relative contents of ferulic acid,gallic acid and caffeic acid were relatively high,and they were the major phenolic substances.The relative content of gallic acid increased with the increase of successive generations.The content of ferulic acid increased firstly and then decreased with the increase of successive generations,but both contents were higher than the control.However,it was opposite for caffeic acid.The relative contents of ferulic acid,gallic acid and caffeic acid in the 3 rd generation were higher than those in the 1 st generation.A total of 8 phenolic compounds were identified in the root tips,in which the contents of catechins,quinic acid and kaempferol were relatively higher as compared with other phenolic compounds.The content of catechins decreased gradually from the 1 st to the 3 rd generations.Moreover,the catechins contents in the 2 nd and the 3 rd generations were higher than the control.The content of kaempferol increased gradually from the 1 st to 3 rd generations,and its contents in different generations were lower than the control.The content of quinic acid rose firstly and then decreased,while the contents of quinic acid in different generations were higher than the control.Correlation analysis showed that significant and negative correlations were observed among ellagic acid,quinic acid and acid phosphatase,while gentisic acid was positively correlated with acid phosphatase.Rutin,gentisic acid were negatively correlated with polyphenol oxidase.Positive correlationship between ellagic acid and polyphenol oxidase was observed.Gallic acid was significantly and negatively correlated with urease.Quercetin,rutin,vanillic acid and urease were significantly and positively correlated,and p -coumaric acid,kaempferol and invertase showed positive correlation.The above findings suggested that the continuous-planting of C.lanceolata might affect the soil enzymes activities through altering the accumulation of phenolic acids in plant root tips and soil,which in turn affected the uptake and utilization of nutrients from soil,as a result,the growth of C.lanceolata was inhibited,and the continuous planting obstacle of C.lanceolata occurred.