Collaborative Research: Effects of Flow Regime Shifts, Anticendent Hydrology, Nitrogen Pulses and Resource Quantity and Quality on Food Chain Length in Rivers

合作研究：流态变化、前期水文、氮脉冲以及资源数量和质量对河流食物链长度的影响

• 批准号: 1457689
• 负责人: Tamara Harms
• 金额: $ 46.1万
• 依托单位: University of Alaska Fairbanks Campus
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2021-09-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1457689&HistoricalAwards=false
• 关键词: Collaborative; Research; Effects; Flow; Regime

The pattern of water flow in a river can affect the abundance of plants and animals and the food web that supports fisheries. Severe floods that scour the riverbed can potentially displace or kill plants and animals, however, little is known about how floods (or droughts) or the timing of these across years affects the complexity and diversity of food webs. Some work suggests that river flow is a stronger determinant than the quantity of plant production on the flow of energy through the food web, but little is known about how the quality of plant food affects food chains and biodiversity. The study will provide fundamental information on how the timing of floods and droughts across years influences water quality (nitrate inputs to rivers), primary production, and the production of animals higher in the food web, such as fish. The researchers will produce a synthesis of research in hydrology and ecology to improve the management of arid land rivers. This work will reach across fundamental knowledge to education, from kindergarten to graduate levels. The project will have numerous broader impacts including training of several undergraduates, graduate students, and a postdoc. Researchers will work with a non-profit group to integrate project findings into an existing citizen science program on river drying sponsored by The Nature Conservancy, and develop an environmental education program for grades K-5. Finally, the research team will establish an innovative open source, distributed graduate seminar on application of statistical methods in ecology.Researchers will study streams spanning a gradient in the timing of rainfall to examine the role of changing hydrologic regimes in altering nitrogen supply, energy supply and food web structure in arid land streams. This proposal will: 1) Quantify the effect of food quality, energy supply and energetic efficiencies on trophic structure, 2) Quantify the effects of time between floods on stimulation of plant production and trophic structure, and 3) Quantify the effect of changes in flow regime on trophic structure via direct mortality, shifts in plants at the base of the food web, and the structure of the food web. Proposed research activities include characterization of the hydrologic regime, analysis of food webs across a hydroclimate gradient, and manipulation of nitrogen supply. Extreme event statistics and spectral analyses will characterize properties of flood intervals and flow regime shifts across 12 study sites spanning a gradient in timing of rainfall and hydrologic variation (monsoon vs. winter precipitation dominance) in Arizona. Derived hydrologic metrics will be used in combination with measures of ecosystem metabolism, N supply, secondary consumer energetic efficiencies, resource stoichiometry, and the proportion of autochthonous energy sources as predictor variables of food chain length and trophic structure to understand the mechanisms linking energetics and hydrology to food chain length. This comparative study includes 12 streams within the same biogeographic province that feature an algal-dominated food source and similar ecosystem size (1st-3rd order streams). Additionally researchers will conduct a nitrogen enrichment experiment in 6 streams to disentangle the indirect effects of water flow on nitrogen cycling versus the direct effects on plants and animals.

河流中的水流模式会影响植物和动物的丰富度以及支持渔业的食物网。冲刷河床的严重洪水可能会导致植物和动物流离失所或死亡，然而，人们对洪水（或干旱）或历年发生的时间如何影响食物网的复杂性和多样性知之甚少。 一些研究表明，河流流量比植物产量对食物网能量流动的影响更大，但人们对植物性食物的质量如何影响食物链和生物多样性知之甚少。该研究将提供有关多年来洪水和干旱的时间如何影响水质（河流的硝酸盐输入）、初级生产以及食物网中较高级别的动物（例如鱼类）的生产的基本信息。 研究人员将进行水文学和生态学研究的综合，以改善干旱地区河流的管理。 这项工作将涵盖基础知识和教育，从幼儿园到研究生阶段。 该项目将产生许多更广泛的影响，包括培训多名本科生、研究生和博士后。研究人员将与一个非营利组织合作，将项目研究成果整合到大自然保护协会赞助的现有河流干涸公民科学计划中，并为 K-5 年级制定环境教育计划。最后，研究小组将建立一个创新的开源、分布式研究生研讨会，讨论统计方法在生态学中的应用。研究人员将研究降雨时间梯度的溪流，以研究水文状况的变化在改变氮供应、能源供应方面的作用。和干旱土地溪流中的食物网结构。 该提案将： 1) 量化食品质量、能源供应和能量效率对营养结构的影响，2) 量化洪水之间的时间对刺激植物生产和营养结构的影响，以及 3) 量化流量变化的影响通过直接死亡率、食物网底部植物的变化以及食物网的结构来确定营养结构的制度。 拟议的研究活动包括水文状况的表征、水文气候梯度上的食物网分析以及氮供应的控制。极端事件统计和光谱分析将描述亚利桑那州 12 个研究地点的洪水间隔和流态变化的特性，这些研究地点跨越降雨时间和水文变化（季风与冬季降水主导）的梯度。导出的水文指标将与生态系统代谢、氮供应、二次消费者能量效率、资源化学计量和本地能源比例等指标结合使用，作为食物链长度和营养结构的预测变量，以了解能量学和水文学之间的联系机制到食物链的长度。这项比较研究包括同一生物地理省内的 12 条溪流，这些溪流的食物来源以藻类为主，生态系统规模相似（一阶至三阶溪流）。此外，研究人员还将在 6 条溪流中进行氮富集实验，以区分水流对氮循环的间接影响与对植物和动物的直接影响。