槟榔林下间作平托花生土壤细菌群落结构及多样性研究

Community structure and diversity of soil bacteria in intercropping Arachis pintoi under Areca Catechu forest

为探索槟榔林下间作平托花生能否改善槟榔园土壤微生物环境,试验选取槟榔林下间作平托花生和槟榔单作模式下10~20 cm土层的土壤样本,测定pH及酸性有效磷、全磷、速效钾、有机碳、全氮、碱解氮、全钾含量等理化因子,在此基础上,利用Illumina MiSeq测序平台对槟榔间作平托花生和槟榔单作模式下土壤的细菌群落进行16S rRNA V4~V5区检测。结果表明:在理化因子方面,槟榔林下间作平托花生模式下的有效磷、全磷、全钾、速效钾含量以及p H显著提高。在土壤细菌群落多样性方面,间作模式的土壤细菌多样性和丰富度与槟榔单作模式存在一定差异,其中Chao1指数、ACE指数分别显著增加4.95%、4.60%,Shannon指数和Simpson指数也均增加但未达显著性差异,土壤细菌的物种丰富度和群落多样性均有所提高。在土壤细菌群落结构方面,从门水平分析,2组样本的主要优势菌门为变形菌门(Proteobacteria)、酸杆菌门(Acidobacteria)、放线菌门(Actinobacteria)、绿弯菌门(Chloroflexi);从属水平上分析,主要优势菌属为Gp1~Gp6、亚硝化球菌属(Nitrososphaera)、Gaiella、芽单胞菌属(Gemmatimonas)和Pseudolabrys等。冗余分析结果表明,速效钾、有机碳、全氮和干湿比是影响土壤细菌群落结构的主要理化因子;速效钾解释了76.2%的变异程度,有机碳、全氮和干湿比解释度分别为3.5%、7.6%和9.1%;排序轴1、排序轴2对土壤总细菌变异程度的解释度分别为83.96%、8.71%,解释度总共高达92.67%。单作模式的土壤细菌群落结构差异主要由全氮和有机碳含量的变化引起,而间作模式细菌群落结构主要受速效钾和干湿比的影响。此外,放线菌门、芽单胞菌门、变形菌门与速效钾、有机碳、全氮含量呈正相关;酸杆菌门、绿弯菌门、拟杆菌门、疣微菌门与速效钾含量和干湿比呈负相关;属水平下由细菌菌属与理化因子的相关性分析可知,亚硝化球菌属、硝化螺菌属、Gp4、Gp1和Gp2菌属均与理化因子呈显著负相关;Gaiella、芽单胞菌属、Pseudolabrys、红游动菌属与理化因子呈显著正相关。代谢功能预测分析表明,氨基酸代谢、碳水化合物代谢、膜运输和能量代谢是两种种植模式下细菌群落的主要代谢功能途径。间作后细菌群落能量代谢功能基因增加,苯丙素、类黄酮和甜菜红色素等次生代谢产物生物合成功能基因均显著减少,辅助因子和维生素的代谢功能基因以及昼夜节律-植物的功能基因显著减少。因此,槟榔林下间作平托花生不仅能提高土壤pH、有机碳及氮、磷、钾含量和土壤细菌多样性,还能改善代谢功能,从而促进槟榔根系对营养元素的有效吸收,为槟榔健康栽培提供理论依据和技术支撑。

In order to explore whether Areca catechu intercropping with Arachis pintoi can improve the soil microbial environment of Areca catechu plantation,selected soil samples of 10~20 cm soil layer under Areca catechu forest intercropping with Arachis pintoi and Areca catechu monoculture,and measured physical and chemical factors such as pH and the content of acid available phosphorus,total phosphorus,available potassium,organic carbon,total nitrogen,available nitrogen,and total potassium.On this basis,the Illumina MiSeq sequencing platform was used to detect the bacterial community under 16S rRNA V4~V5 area in soil under Areca catechu intercropping with Arachis pintoi and Areca catechu monoculture models.The results showed that in terms of soil physical and chemical factors,the contents of acid available phosphorus,total phosphorus,total potassium,available potassium and pH value of Areca catechu intercropping with Arachis pintoi were significantly increased.In the diversity of soil bacterial community,the diversity and abundance of soil bacteria in the intercropping pattern were different from those in Areca catechu monoculture pattern,in which the Chao1index and ACE index increased significantly by 4.95% and 4.60%,and Shannon index and Simpson index increased but with no significant difference,besides,the species richness and community diversity of soil bacteria increased.According to the results of the structure of soil bacterial community analyzed at phylum level,Proteobacteria,Acidobacteria,Actinobacteria and Chloroflexi were the dominant phylum in the two groups.At the genus level,the main dominant bacteria were Gp1~Gp6,Nitrososphaera,Gaiella,Gemmatimonas and Pseudolabrys etc.The results of redundancy analysis suggested that available potassium,organic carbon,total nitrogen and dry-wet ratio were the main physical and chemical factors affecting the structure of soil bacterial community.Available potassium explained 76.2% of the variation degree,and the interpretation rates of organic carbon,total nitrogen and dry-wet ratio were 3.5%,7.6% and 9.1%,respectively.The interpretation degree of sequencing axis 1 and axis 2 to the variation degree of soil bacteria was 83.96% and 8.71%,respectively,with a total interpretation degree of 92.67%.The difference of soil bacterial community structure in monoculture model was mainly caused by the change of total nitrogen and organic carbon content,while that in intercropping model was mainly affected by available potassium and dry-wet ratio.In addition,Actinobacteria,Gemmatimonadetes and Proteobacteria were positively correlated with content of available potassium,organic carbon and total nitrogen,while Acidobacteria,Chloroflexi,Bacteroidetes and Verrucomicrobia were negatively correlated with available potassium content and dry-wet ratio.There was a significantly negative correlation between physical and chemical factors and the genera of Nitrososphaera,Nitrospira,Gp4,Gp1,Gp2,while Gaiella,Gemmatimonas,Pseudolabrys and Rhodoplanes were significantly positively correlated with physical and chemical factors.Metabolic function prediction analysis showed that amino acid metabolism,carbohydrate metabolism,membrane transport and energy metabolism were the main metabolic pathways of bacterial communities under the two cropping patterns.After intercropping,the functional genes like energy metabolism were significantly increased,while the functional genes of biosynthesis of secondary metabolites such as phenylpropanoid,flavonoids and beet red pigment,as well as the genes of metabolism of cofactors and vitamins and the functional genes circadian rhythm-plants were significantly decreased.Therefore,intercropping Arachis pintoi under Areca catechu forest can not only increase soil pH,the content of organic carbon,nitrogen,phosphorus,potassium and soil bacteria diversity,but also promote metabolic function of soil bacteria community,so as to accelerate the effective absorption of nutrient elements by Areca catechu root,and provide theoretical basis and technical support for the healthy cultivation of Areca catechu.