Environmental Microbiomics Research Center, School of Environmental Science and Engineering, Southern Marine Science and Engineering Guangdong Laboratory (Zhuhai), Sun Yat-sen University, Guangzhou 510006, China.
South China Sea Institution, Sun Yat-sen University, Zhuhai 519082, China.
Sci Total Environ. 2020 Jun 15;721:137807. doi: 10.1016/j.scitotenv.2020.137807. Epub 2020 Mar 7.
Biological nitrogen fixation (BNF) mediated by diazotrophic communities is a major source of bioavailable nitrogen in mangrove wetlands, which plays important roles in maintaining the health and stability of mangrove ecosystems. Recent large-scale mangrove afforestation activities have drawn great attention due to introduced mangrove species and their potential impacts on bio-functionalities of local ecosystems. However, the effects of introduced mangrove species on diazotrophic communities remain unclear. Here, we analyzed rhizosphere and endosphere diazotrophic communities between native mangrove species (Avicennia marina) and introduced mangrove species (Sonneratia apetala and Laguncularia racemose) by sequencing nifH gene amplicons. Our results showed that S. apetala and L. racemose introduction significantly (P < 0.05) increased nutrition components (e.g., total carbon and total nitrogen) in rhizosphere, as well as the diazotrophs richness in rhizosphere and endosphere. The relative abundance of clusters III diazotrophs in the rhizosphere and Rhizobium in the endosphere were significantly increased with L. racemosa or S. apetala introduction. Fe and pH were the main environmental factors driving the divergence of endophyte-rhizophyte diazotrophs between native and introduced mangroves. The correlation-based network analyses indicated that the interaction among rhizophyte-endophyte diazotrophs is more harmonious in native mangrove, while there exist more competition in introduced mangroves. These findings expand our current understanding of BNF in mangrove afforestation, and providing new perspectives to sustainable management of mangrove ecosystem.
生物固氮（BNF）由固氮生物群落介导，是红树林湿地中生物可利用氮的主要来源，对维持红树林生态系统的健康和稳定起着重要作用。由于引入的红树林物种及其对当地生态系统生物功能的潜在影响，最近大规模的红树林造林活动引起了广泛关注。然而，引入的红树林物种对固氮生物群落的影响仍不清楚。在这里，我们通过测序 nifH 基因扩增子分析了本地红树林物种（桐花树）和引入的红树林物种（海桑和尖瓣海桑）的根际和内生固氮生物群落。我们的结果表明，海桑和尖瓣海桑的引入显著（P<0.05）增加了根际的营养成分（如总碳和总氮），以及根际和内生固氮生物群落的丰富度。根际 III 型固氮菌的相对丰度和内生根瘤菌的相对丰度随着尖瓣海桑或海桑的引入而显著增加。Fe 和 pH 是驱动本地和引入红树林根际-内生固氮生物群落差异的主要环境因素。基于相关性的网络分析表明，在本地红树林中，根际-内生固氮生物之间的相互作用更加和谐，而在引入的红树林中则存在更多的竞争。这些发现扩展了我们对红树林造林中生物固氮的认识，并为红树林生态系统的可持续管理提供了新的视角。
