The United Graduate School of Agricultural Sciences, Iwate University, 18-8, Ueda 3-chome, Morioka, Iwate 020-8550, Japan; Faculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia, Russian Federation Blvd, PO Box 86, Phnom Penh 120404, Cambodia.
Faculty of Hydrology and Water Resources Engineering, Institute of Technology of Cambodia, Russian Federation Blvd, PO Box 86, Phnom Penh 120404, Cambodia.
Sci Total Environ. 2023 Dec 1;902:166524. doi: 10.1016/j.scitotenv.2023.166524. Epub 2023 Aug 23.
Soil microbial communities control biogeochemical processes, nutrient cycling, and organic carbon storage and release in wetlands, which are influenced by flooding. To predict soil nutrient function in wetland ecosystems, understanding the effect of flooding on soil biogeochemical cycling and energy flux, including soil properties, dissolved organic matter (DOM), and microbial communities is essential. This study investigated how different flood durations (1, 3, 8, 16, and 30 d) affect the interactions between physicochemical properties and bacterial communities in a river wetland. The DOM composition was measured using ultraviolet/visible spectrophotometry coupled with fluorescence spectroscopy, and the bacterial communities were identified using 16S rRNA sequencing. Simpson's diversity index varied from 0.92 to 0.94, indicating high bacterial diversity throughout the treatments; the highest and lowest bacterial diversities were found at 1 and 8 flooding days, respectively. The abundance of Desulturomonadales, Clostridiales, Bacteroidales, and Gaiellales was positively correlated with pH, electrical conductivity, water-extractable dissolved organic carbon (WEOC), and water-extractable total dissolved nitrogen (TDN) but negatively correlated with dissolved oxygen (DO) and soil organic matter (SOM), suggesting complex interactions among these factors in response to flooding. Structural equation model revealed that flooding directly increased TDN but indirectly increased WEOC through increasing soil pH; and directly decreased DO and SOM, leading to decreases in total protein-like fraction. Three significant pathways were identified, showing the impacts of flooding on bacterial diversity: (1) flood duration decreased DO, resulting in decreased bacterial diversity; (2) flood duration decreased SOM, leading to increased bacterial diversity; and (3) flood duration decreased DO and SOM, leading to increased bacterial diversity via decreased total protein-like fraction. This study indicated that prolonged flooding has both positive and negative impacts on bacterial diversity, depending on environmental factors. It highlights the importance of flooding in shaping soil bacterial communities, with implications for nutrient cycling and carbon storage in wetlands.
土壤微生物群落控制着湿地中的生物地球化学过程、养分循环以及有机碳的储存和释放，而这些过程又受到洪水的影响。为了预测湿地生态系统中的土壤养分功能，了解洪水对土壤生物地球化学循环和能量通量的影响，包括土壤特性、溶解有机物质（DOM）和微生物群落，是至关重要的。本研究调查了不同的洪水持续时间（1、3、8、16 和 30 天）如何影响河流湿地中理化性质与细菌群落之间的相互作用。采用紫外/可见分光光度法结合荧光光谱法测定 DOM 组成，采用 16S rRNA 测序鉴定细菌群落。辛普森多样性指数在 0.92 到 0.94 之间变化，表明整个处理过程中的细菌多样性很高；在 1 天和 8 天洪水期间，细菌多样性最高和最低。Desulturomonadales、Clostridiales、Bacteroidales 和 Gaiellales 的丰度与 pH、电导率、水可提取溶解有机碳（WEOC）和水可提取总溶解氮（TDN）呈正相关，与溶解氧（DO）和土壤有机质（SOM）呈负相关，表明这些因素之间存在复杂的相互作用，以响应洪水。结构方程模型表明，洪水直接增加 TDN，但通过增加土壤 pH 间接增加 WEOC；并直接降低 DO 和 SOM，导致总蛋白样分数降低。确定了三个显著途径，显示了洪水对细菌多样性的影响：（1）洪水持续时间降低 DO，导致细菌多样性降低；（2）洪水持续时间降低 SOM，导致细菌多样性增加；（3）洪水持续时间降低 DO 和 SOM，通过降低总蛋白样分数，导致细菌多样性增加。本研究表明，长时间的洪水对细菌多样性既有积极影响，也有消极影响，这取决于环境因素。它强调了洪水在塑造土壤细菌群落方面的重要性，对湿地中的养分循环和碳储存具有启示意义。
