海岸沙地肉质入侵植物对微生物群落功能与结构变化的影响

Evidence of functional and structural changes in the microbial community beneath a succulent invasive plant in coastal dunes

海岸沙地提供了诸多宝贵的生态系统服务,例如耕地保护、水分供应和生物多样性保护,因此海岸沙地代表了重要的栖息地保护区。因为海岸沙地环境恶劣、水资源匮乏、养分贫瘠,所以土壤微生物群落对维持植物多样性至关重要。就海岸沙地的生态系统保护而言,外来入侵植物是主要威胁。本文探讨了沿海地区入侵植物食用日中花(Carpobrotus edulis)对细菌群落功能及结构的各种影响。沙地中土壤有机质含量低,微生物活性有限,所以沙地是一种颇具挑战性的底物。因此,在评估食用日中花对生态系统的影响之前需要对细菌提取进行优化,并开展功能评估。本文首先从群落水平生理特征(CLPP)的角度,比较了采用不同土壤储量、样品量、提取液等12种提取方法对沙地群落功能活性的影响,然后又探讨了食用日中花入侵的沙地菌落功能(利用Biolog Ecoplates)与结构变化(利用PCR-DGGE)。血细胞计数发现盐溶液持续增殖了细菌细胞(P≤0.001)。主成分分析(PCA)结果显示,在有限时间框架(0–24 h)内,碳底物消耗没有显著变化。通过对比天然区与非天然区(种间)及天然区(种内)之间食用日中花入侵后的变化,发现了一种与众不同的碳底物利用模式,食用日中花入侵对群落功能的影响因地而异,而与之相辅相成的是,PCR-DGGE结果表明原沙地的菌落结构不同于食用日中花入侵后沙地的菌落结构。

Coastal dunes represent priority habitats for conservation due to the provision of valuable ecosystem services such as land protection,water supply or biodiversity conservation.Soil microbial communities are of crucial importance to maintain plant diversity due to harsh environmental conditions,water limitation and nutrient scarcity.Invasive alien plants represent a major threat to ecosystem conservation.Here,we explored different impacts of Carpobrotus edulis,a succulent plant invading coastal areas worldwide,on the function and structure of bacterial communities.Sand represents a challenging substrate due to low organic matter content and limited microbial activity.We optimized bacterial extraction for functional evaluation before assessing ecosystem impacts produced by C.edulis.We compared 12 extracting procedures combining different soil storage,sample amount and extracting solutions on the functional activity of sand communities through the community-level physiological profile.We further explored the function(using Biolog Ecoplates)and structure[using polymerase chain reaction–denaturing gradient gel electrophoresis(PCR-DGGE)]of bacterial communities from dunes invaded by C.edulis.Saline solution consistently increased bacterial cells detected by cytometry(P≤0.001).Principal component analysis suggested a limited temporal framework(0–24 h)in which community function can be explored without significant alterations in C substrate consumption.Changes under C.edulis invasion exhibited a different pattern of C substrate utilization comparing native and non-native zones(interspecific),but also between native zones(intraspecific),suggesting that functional impacts are site-dependent.Complementary,results obtained from PCR-DGGE indicated that the bacterial community structure of native dunes significantly differed from dunes invaded by C.edulis.