闽江河口红树林土壤微生物群落对互花米草入侵的响应

Soil microbial community of mangrove forests and its responses to the invasion of Spartina alterniflora in the Minjiang River Estuary

采用磷脂脂肪酸标记法(PLFA)研究外来入侵植物互花米草对闽江河口湿地红树林土壤微生物群落结构的影响,并探讨其主要影响因素。结果表明:从3种不同植被群落土壤(红树林群落MC、红树林-互花米草混生群落MS、互花米草群落SC)共检测到22种PLFA生物标记,MS土壤微生物PLFA生物标记总量明显高于其他植被群落,3种植被群落土壤理化性质和酶活性的变化趋势为:MC>MS>SC,表明互花米草入侵后土壤微生物量增加,而理化性质和酶活性均有明显下降,红树林湿地土壤质量发生了明显退化。3种植被群落土壤中含量最高的PLFA生物标记是16:0,16:1w7c,9Me15:0w,18:1w12c。土壤中特征微生物相对生物量存在明显差异,细菌分布量最大,其次是真菌和放线菌,原生动物分布量最小。群落多样性指数呈相似规律,MS土壤微生物类群多样性指数均小于MC,表明互花米草入侵后土壤微生物群落多样性指数均有下降。通过主成分分析,基本能区分出3种不同植被群落微生物群落的特征。土壤理化性质、酶活性间存在相关性,有机碳、全氮、蔗糖酶、过氧化氢酶与革兰氏阴性菌、放线菌呈显著或极显著正相关。研究结果表明互花米草入侵在一定程度上具有影响红树林群落土壤营养代谢循环的潜力,特别是关于碳、氮、磷等的循环及酶活性,改变部分有利于自身生长的土壤环境相关的微生物类群含量,竞争有利环境,迅速扩张实现入侵。

In the present study, soil microbial communities of mangrove forests and its responses to the invasion of Spartina alterniflora were analyzed using phospholipid fatty acid analysis （PLFA）. Soil physic-chemical properties and enzyme activities were measured in the Minjiang River Estuary. The results showed that： There were 22 PLFAs that were significantly different in soil samples from mangrove communities （MC）, Mangrove-S. alterniflora （MS）, and S. alterniflora communities （SC）. The MS soil exhibited richer PLFAs than the other vegetation types. The physic-chemical properties and enzyme activities in soils of different vegetation communities were in the order of MC 〉 MS 〉 SC. Following the invasion of S. alterniflora, the soil microbial biomass of mangrove communities increased, and the physic-chemical properties, enzyme activities significantly decreased, and the quality of mangrove wetland soil was degraded. The PLFAs biomarkers of three species with the highest contents were 16：0, 16：1w7c, 9Me15：0w, and 18：1w12c. There was a significant difference in the relative biomass of soil microbial biomass. Bacteria exhibited the richest distribution, followed by fungus, actinomycetes, and protozoans. Community diversity indices showed a similar pattern, MS soil microbial community diversity indexes were less than those of MC. The soil microbial community diversity indexes decreased following the invasion of S. alterniflora. Principal component analysis was able to distinguish the characteristics of microbial communities in different vegetation communities. The soil physic-chemical properties were closely correlated with enzyme activities, and SOC, TN, sucrose, and catalase were significantly correlated with the PLFAs of gram-positive bacteria and actinomycetes. The results of this study showed that the invasion of S. alterniflora has the potential to affect nutrient metabolism in the mangrove community, especially with regard to the C, N and P cycles, and the enzyme activities. S. alterniflora can change the microbial biomass to create favorable soil environments for their growth to achieve the rapid invasion.