Catastrophic Disturbance in a Tropical Rain Forest - Impact of the Riparian Zone on Nutrient Export

1989年9月17日至18日，飓风雨果几乎完全摧毁了波多黎各Luquillo实验森林的部分森林。飓风毁林与在热带森林中研究的其他扰动（伐木、砍砍和焚烧农业）有很大的不同，主要在于大量的活生物量立即进入地表凋落物区。目前还没有足够的数据来预测这种凋落物输入将如何影响或受热带森林河岸带营养动态的影响。Drs。自1988年8月以来，麦克道尔、鲍登和史密斯一直在这片森林的两个地点对近地表地下水和溪水进行采样。他们的工作强调了通过河岸带的养分和水通量，并评估了微生物与维管植物通过该界面控制养分通量的相对重要性。这个新项目将研究雨果飓风造成的森林砍伐对河岸区调节从陆地到水生生态系统的营养物质运输能力的影响。研究人员假设，在这种灾难性的干扰之后，河岸带在调节氮的损失方面起着至关重要的作用。他们明确提出了两个主要假设：1)与雨果飓风相关的森林砍伐将导致比斯利流域的河流氮输出增加；2)氮的保留和转化将大大减少溪流中氮的输出量。为了验证这些假设，飓风雨果前后的信息将在两个地点进行比较，一个地点受干扰，一个地点未受干扰。从事这项研究的科学家是经验丰富、富有成果的研究人员，他们以前对热带森林的河岸过程有过研究经验。该计划得到了优秀的机构设施的支持。

On September 17-18, 1989, Hurricane Hugo almost completely deforested portions of the Luquillo Experimental Forest in Puerto Rico. Hurricane deforestation differs substantially from other disturbances that have been studied in tropical forests (logging, slash and burn agriculture) principally in that an enormous amount of live biomass instantly enters the surface litter compartment. Insufficient data exist to predict how this litter input will affect or be affected by nutrient dynamics in the riparian zone of this tropical forest. Drs. McDowell, Bowden and Smith have been sampling near- surface ground water and stream water at two sites in this forest since August 1988. Their work emphasizes the nutrient and water flux through the riparian zone and assesses the relative importance of microbial versus vascular plant control of nutrient flux through this interface. This new project will examine the impact of deforestation caused by Hurricane Hugo on the ability of riparian zones to regulate transport of nutrients from terrestrial to aquatic ecosystems. The investigators hypothesize that the riparian zone plays a crucial role in regulating losses of nitrogen following this catastrophic disturbance. They specifically identify two major hypotheses: 1) deforestation associated with Hurricane Hugo will result in increased fluvial export of nitrogen from the Bisley watershed, and 2) the magnitude of nitrogen export in stream water will be lessened significantly by nitrogen retention and transformation. To test these hypotheses, information from before and after Hurricane Hugo will be compared at two sites, one disturbed and one undisturbed. The scientists engaged in this research are experienced, productive researchers who have previous experience with riparian processes in tropical forests. The program is supported by excellent institutional facilities.