SGER: Nutrient Dynamics in Riverine Wetlands -- The Effects of Flooding

低频率但高强度的干扰事件，如严重的火灾或洪水，是构成许多生态系统的关键因素（Grime，1979;休士顿，1979; Picket白色，1985; sparks等，1990年）。 1993年密西西比河上游的洪水提供了一个机会来研究这种事件对大型河流洪泛区生态系统的组成和过程的影响。 美国陆军工程兵团和美国地质调查局对1993年洪水的重现周期进行了不同的估计，1993年洪水的重现周期非常长（3月至10月：图1），为100-500年。 尽管人们认识到营养盐供应通常是控制初级生产力的主要限制因素，但对河流湿地营养盐动态的研究相对较少。 长时间的大洪水将以多种方式影响河漫滩的养分动态。它们会使富含有机物的沉积物存款下来，但也会增加诸如反硝化作用等过程的速度，这将导致营养物从系统中流失。 洪水还将改变植被组成的早期演替状态：土壤过程的速度受到植物物种组成的强烈影响。 关于大型河流漫滩营养盐动态的数据很少，而对于大部分漫滩仍然完好的大型河流，数据就更少了。 我们建议调查的影响，1993年的洪水在河漫滩的养分动态的养分含量和土壤过程的一系列被洪水淹没的不同程度的网站进行比较。 1993年的洪水提供了一个独特的研究机会。 我们建议与荷兰乌得勒支大学的Jos Verhoeven博士合作，他的小组是湿地营养动态研究的领导者之一。

9413134 Sparks Low frequency but high magnitude disturbance events such as severe fires or floods are key factors structuring many ecosystems (Grime, 1979; Huston, 1979; Picket & White, 1985; sparks et al., 1990). the 1993 flood on the Upper Mississippi River provides a rate opportunity to investigate the impact of such an event on the components and processes of a large river floodplain ecosystem. The recurrence interval of a flood equivalent to that of 1993, which was of exceptionally long duration (March to October: Figure1), has been variously estimated at 100-500 years by the Army Corps of Engineers and the US Geological Survey. Although it is acknowledged that nutrient supply is usually the main limiting factor governing primary productivity, the nutrient dynamics of riverine wetlands has been relatively little studied. Large floods of long duration will affect nutrient dynamics of the floodplain in a number if ways. they will deposit sediment rich in organic matter, but will also increase the rates of processes such as denitrification which will lead to a loss of nutrient from the system. Flooding will also change the vegetational composition to that of an early successional state: the rates of soil processes are strongly influenced by the species composition of the plants growing in them. There are few data on nutrient dynamics of large rive floodplains, and even less for large rivers with a substantial part of their floodplain still intact,. %%% We propose to investigate the effects of the 1993 flood in the nutrient dynamics of the floodplain by comparing the nutrient content and rates of soil processes of a range of sites which were inundated by the flood to a different extent. The 1993 flood provides a unique research opportunity. We propose to cooperate with Dr. Jos Verhoeven (Utrecht University, The Netherlands) whose group is one of the leaders in research on wetland nutrient dynamics.