连栽木麻黄根际微生物群落结构和功能特征

以不同栽培代数的木麻黄(第1代FCP、第2代SCP、第3代TCP)根际土壤为试验材料,运用BIOLOG微平板和磷脂脂肪酸(PLFA)技术分析根际土壤微生物群落结构和功能多样性对多代连栽响应。结果表明,不同代数的土壤微生物对各类碳源的利用程度存在显著差异,连栽后木麻黄根际土壤微生物对碳源利用率显著下降。在6类碳源中,除胺类外,其他5种碳源均呈现FCP>SCP>TCP。PLFA分析共检测到11种PLFA生物标记,FCP土壤微生物PLFA生物标记总量明显高于SCP和TCP,3个代数土壤中含量最高的PLFA生物标记是i16:0、a15:0和18:1ω9c。土壤中特征微生物含量差异明显,细菌分布量最大,其次是真菌和放线菌。随栽植代数增加,细菌含量减少,真菌含量增加。土壤微生物群落多样性指数均呈现FCP>TCP>SCP,与土壤理化性质变化密切相关。可见木麻黄连栽显著影响其根际土壤微生物群落结构与功能,因此根际土壤微生态失衡可能是导致木麻黄连栽障碍的重要因素。

Microbial community structure and functional characteristics of rhizosphere soil in different generations of Casuarina equisetifolia plantations

In this study,we aimed to investigate changes in the microbial community structure and functional diversity of rhizosphere soil,in response to continuous cultivation.We used BIOLOG microplate and phospholipid fatty acid(PLFA)technology to analyze microbial community composition and function of the rhizosphere soil ofCasuarina equisetifoliagrown in the first(FCP),the second(SCP),and the third(TCP)generation forests.The BIOLOG results showed that there were significant differences in the utilization of different carbon sources among FCP,SCP,and TCP.The utilization ratios of carbon sources by the soil microbial community significantly decreased following continuous planting.Among the six types of carbon sources,five showed the following pattern in utilization:FCP>SCP>TCP,the exception being amines.From the PLFA analysis,11 PLFAs biomarkers were detected.The total amount of PLFA biomarkers in FCP soil was significantly higher than that of SCP and TCP,and the highest content of PLFA biomarkers in all soil samples were found for i16:0,a15:0 and 18:1ω9 c.The characteristic microbial content in the soil was significantly different among the forest types,but the bacterium distribution was consistently the largest,followed by fungus and actinomycete.The bacterium content decreased and the fungal content increased after continuous planting.The community diversity index also showed the following trend:FCP>TCP>SCP,and it was significantly affected by TN,AN,TP,and pH value.Therefore,the continuous cultivation ofC.equisetifoliahad a significant effect on the rhizosphere soil microbial community.It is speculated that the problem of continuous cultivation ofC.equisetifoliais caused by an imbalance in the microbial community of the rhizosphere soil.