REU: Productivity, Plant Biomass, and Trophic Interactions Rivers

一场对所有食物网理论都感兴趣的辩论 关于捕食者的攻击率是否应该取决于 瞬时猎物密度，或相反的猎物的比例 数量与分享它们的捕食者的数量相对应。 模型 根据绝对猎物密度的攻击率预测， 营养级将逐步增加， 生产力，直到链接添加到食物链， 消费者的生物量和资源应该是不相关的。 比率依赖模型预测连续单调增加 随着生产力的提高，所有营养级的生物量， 丰富的消费者和资源应该 是的。 这些假设和预测可以用 简单的实地观察。 私家侦探建议测试 假设和预测的两个模型在河流中使用一个 混合实验和多河流比较。 的 研究人员将研究生产力对食物网影响 冬季洪水过后， 社区发展发生在可预测的夏季低， 利用遮阴控制初级生产力 通过营养扩散， 陶罐（clay pots） 在这些实验性的舞台上，私家侦探。 将观察洪水后食物网的组装， 生产率制度，记录个人的应计额， 生产者、初级消费者和捕食者行会的生物量; 分类组成和多样性，这些公会，和大小 其组成种群的结构。 私家侦探将进行 其他短期行为实验来测量攻击率 在不同的猎物下， 和捕食者密度，以及在存在和不存在植物的情况下， 掩护 为了检验实验结果的一般性， 主要研究地点，研究者将调查几条河流 这代表了环境生产力的梯度， 研究食物网的营养结构， 夏季为低流量季节，冬季为洪水季节。

A debate of general interest to all food web theory has arisen over whether attack rates of predators should depend on instantaneous prey densities, or instead on ratios of prey numbers to the numbers of predators sharing them. Models with attack rates scaled to absolute prey densities predict that trophic levels will be added stepwise with increasing productivity, and that until links are added to food chains, biomass of consumers and resources should be uncorrelated. Ratio-dependent models predict continuous monotonic increases of biomass at all trophic levels with increasing productivity, so that abundance of consumers and resources should covary positively. These assumptions and predictions can be tested with fairly simple field observations. The P.I. proposes to test assumptions and predictions of both models in rivers using a mixture of experimental and multi-river comparisons. The investigator will study effects of productivity on food web structure in a seasonal river where, following winter floods, community development occurs during the predictable summer low- flow season and manipulate primary productivity by shading instream channels, and by fertilizing nutrient-diffusing substance (clay pots). In these experimental arenas, the P.I. will observe the post-flood assembly of food webs under various productivity regimes, recording the accrual of individuals and biomass in producer, primary consumer, and predator guilds; the taxonomic composition and diversity of these guilds, and the size structures of their component populations. The P.I. will conduct other, short-term behavioral experiments to measure attack rates of common predators feeding on dominant prey under different prey and predator densities, and in the presence and absence of plant cover. To test the generality of results from experiments at the primary study site, the investigator will survey several rivers that represent a gradient of environmental productivity, and examine trophic structures of food webs that assemble during the summer low-flow season, following winter floods.