Linking Ecosystem Processes and Community Structure in Tropical Marshes: The Role of Macrophytes and Microbial Communities

热带湿地生态系统的变化正在迅速增加，但热带湿地生态系统对养分输入大规模变化的反应却知之甚少。 本研究的目的是获得一个生态系统水平的响应，增加养分输入沿着盐度梯度的解释。 将继续进行一项长期试验，即在2001年开始的一组沼泽地中添加营养物质。 这些地块的一个子集将用于对碳、氮和磷循环的具体组成部分进行更详细的检查。 根系微生态系统将被用于详细的根系分泌物的评估和分子方法将被用于调查沉积物细菌群落。 到目前为止，我们证实，磷添加促进水生植物的生长，导致减少蓝藻垫和消除固氮。在这些结果的基础上，我们建议继续与常规监测的响应变量在现场实验，此外，集中在内部的磷和氮循环中的作用，水生植物和微生物群落。 我们假设，这种循环是由沉积物微生物区系的组成和活动，这反过来又强烈影响的数量和质量的有机碳产生的自养生物（大型植物和蓝藻垫）。 外源磷的加入显著改变了自养生物群落结构，从而改变了有机物料的输入量。 不同的水生植物（香蒲与灯心草）对微生物群落的影响不同，因为它们产生的有机物质的质量和数量不同。 从磷限制到氮限制的转变将取决于内部氮循环的程度和异养微生物群落提供足够额外氮的能力。这项研究将有助于量化和更好地了解在敏感的沼泽生态系统暴露于不断增加的营养投入，通过人类活动的结构和生物地球化学过程的变化。 它在伯利兹和其他热带地区的生物保护和疾病控制方面具有重要的管理应用。

AbstractProposal number 0516159: Linking ecosystem processes and community structure in tropical marshes: the role of macrophytes and microbial communitiesEcosystem alterations in the tropics are increasing rapidly yet reactions of tropical wetland ecosystems to large-scale changes of nutrient input are poorly understood. The aim of this research is to obtain an explanation for an ecosystem level response to increased nutrient input along a salinity gradient. A long-term experiment, involving additions of nutrients to a replicated set of marshes that have started in 2001, will continue. A subset of the plots will be used for more detailed examination of specific components of carbon, nitrogen and phosphorus cycling. Root microcosms will be employed for detailed root exudates assessment and molecular methods will be utilized to investigate the sediment bacterial communities. So far, we confirmed that phosphorus additions promote the growth of macrophytes leading to reduction of cyanobacterial mats and elimination of nitrogen fixation. Building on these results, we propose to continue with the routine monitoring of response variables in the field experiment and, in addition, concentrate on the role of macrophytes and microbial communities in the internal phosphorus and nitrogen cycling. We hypothesize that this cycling is determined by composition and activities of sediment microflora, which in turn is strongly impacted by the quantity and quality of organic carbon produced by the autotrophs (macrophytes and cyanobacterial mats). External addition of P dramatically changes the autotroph community thus changing the quantity of the input of organic materials. Different macrophytes (cattails vs. rushes) will have different impact on microbial community due the differences in the quality and quantity of organic material they produce. The switch from phosphorus to nitrogen limitation will depend on the extent of internal nitrogen recycling and capability of heterotrophic microflora to provide enough additional nitrogen. This research will facilitate quantification and improved understanding of the changing structure and biogeochemical processes in sensitive marsh ecosystems exposed to increasing nutrient inputs through human activities. It has important management applications for biological conservation and disease control in Belize and other tropical regions.