Riparian nutrients and food webs on a regulated river

描述（由申请人提供）：随着世界范围内人类对溪流和河流淡水需求的增加，河流和河岸生态系统的恢复已成为最热门的研究领域之一。河流不仅是农业和人类消费的重要水源，也是生物多样性的关键领域。中部的格兰德河（MRG）流经新墨西哥州中部，拥有美国西南部现存的最广阔的原生棉杨林之一。本研究的目的是研究洪水对棉杨营养分配和河岸食物网动态的影响，以及营养有效性对沿MRG的关键营养物质的生理限制的作用。洪水对杨木和食物网结构的影响将在沿MRG 250公里的8个研究地点进行测量。在两年的时间里，将收集棉杨叶、凋落物、土壤和土壤节肢动物的样本，分析碳(C)、氮(N)、磷(P)以及13C和15N稳定同位素的自然丰度。C和N稳定同位素与C/N、C/P和N/P比值是生态系统研究中评估养分循环和食物网结构与功能的重要工具。通过低品质和高品质饲粮处理以及不同13C和15N稳定同位素特征的一系列试验，研究养分有效性对陆生等足类动物养分分配、生长和繁殖的影响。尽管人们已经研究了许多生物的日粮质量C/N，但P的作用在很大程度上是未知的。这项研究将有助于更好地了解干旱和半干旱地区沿河岸生态系统的生态系统过程，并有助于改善河流水质、生物多样性和水利用的管理。

DESCRIPTION (provided by applicant): Restoration of river and riparian ecosystems has become one of the most intense areas of research as human demands for freshwater from streams and rivers increase worldwide. Rivers are not only vital sources of water for agriculture and human consumption, but key areas of biodiversity. The middle Rio Grande river (MRG), which flows through central New Mexico, contains one of the most extensive riparian forests of native cottonwood remaining in the southwestern United States. The objectives of the proposed study are to examine the role of flooding on cottonwood nutrient allocation and riparian food web dynamics, and the role nutrient availability has on the physiological constraints of a key detritivore along the MRG. The effects of flooding on cottonwoods and food web structure will be measured at eight study sites along a 250 km reach of the MRG. Samples of cottonwood leaves, litter, soil, and soil arthropods will be collected over a two year period and analyzed for carbon (C), nitrogen (N), phosphorus (P), and natural abundance of 13C and 15N stable isotopes. C and N stable isotopes used in concert with C/N, C/P, and N/P ratios are important tools to assess nutrient cycling and food web structure and function in ecosystem studies. The effects of nutrient availability on terrestrial isopod nutrient allocation, growth, and reproduction will be measured during a series of experiments with treatments of low and high diet quality and different 13C and 15N stable isotope signatures. Although diet quality C/N has been studied in many organisms, the role of P is largely unknown. This research will contribute to better general understanding of ecosystem processes along riparian ecosystems in arid and semiarid regions and improved river management for water quality, biodiversity, and water use.