题目：
滨海湿地有机碳库的新视角：微生物残体和球囊霉素的积累对土壤有机碳库贡献的研究
New insight into the accumulation and contribution of glomalin and microbial necromass to the SOC pool in in coastal wetlands
主讲人：2019级博士生李强
时间：3月2日（周四）中午12:30
地点：16教学楼221会议室
摘要：
滨海湿地在碳固存方面发挥着重要作用，是缓解全球气候变化的有效蓝色碳汇（蓝碳）。近年来，滨海湿地面临的盐水入侵和富营养化等环境问题影响了微生物介导的生态系统功能，如C固定和养分转化等。虽然微生物残体和球囊霉素相关土壤蛋白（GRSP）都被证实是SOM的重要贡献者，但对滨海盐沼中微生物代谢产物的积累特征及其驱动因素知之甚少。本研究通过测定微生物残体生物标志物氨基糖、GRSP、胞外酶活性和微生物群落结构，研究了养分富集、土壤盐度和土壤生物地球化学性质是如何调控河口滨海湿地中土壤微生物来源有机碳的积累。结果表明，从上游到下游，真菌和细菌残体C含量均有所下降。随着盐度的增加，微生物残体C对SOC的贡献从16.03％降至10.73％，而总GRSP对SOC的贡献从9.07％增加到13.55％。随机森林模型表明，土壤盐度与沿海湿地的植被类型密切相关，土壤盐度和养分质量解释了土壤微生物残体碳和GRSP积累和变化的大部分变异。此外，真菌残体对SOC的贡献随盐度变化更为敏感，因此真菌可能比细菌在维持滨海盐沼碳固存方面更为关键。
Coastal wetlands play a critical role in storing carbon (C), referred to as “blue carbon”, which provides significant promise for climate change mitigation. In recent years, coastal wetlands have experienced intensively environmental impacts such as saltwater intrusion and eutrophication, resulting in significant shifts in microbially-mediated ecosystem functions, such as C sequestration and nutrient transformations. Although microbial necromass and glomalin-related soil proteins (GRSP) have been verified as important contributors to SOM, little is known about the accumulation characteristics of microbial metabolic products in coastal marshes and their driving factors. Here, we investigated changes in fungal and bacterial necromass using amino sugar biomakers, GRSP, and extracellular enzyme activity to evaluate how changes of multiple contributing factors such as the nutrient enrichment, soil salinity, and soil biogeochemical properties regulate soil microbial-derived C along a river-estuary-coast continuum. The results showed that both fungal and bacterial necromass C contents decreased from upstream to downstream. As salinity increased, the contribution of microbial necromass C to SOC decreased from 16.03% to 10.73% while the contribution of total GRSP to SOC increased from 9.07% to 13.55%. The random forest models suggested that soil salinity was strongly associated with vegetation types in coastal wetlands and nutrient quality explained most of the variation in the accumulation of microbial necromass and GRSP in soil. Moreover, the contribution of fungal necromass to SOC was more sensitive to salinity and fungi might be more pivotal than bacteria in maintaining carbon sequestration in coastal marshes.
