Riparian nutrients and food webs on a regulated river

描述(申请人提供)：随着世界范围内人类对溪流和河流淡水的需求增加，河流和河岸生态系统的恢复已成为最密集的研究领域之一。河流不仅是农业和人类消费的重要水源，而且是生物多样性的关键领域。格兰德河中段流经新墨西哥州中部，是美国西南部现存的最大面积的原生杨木河岸森林之一。这项拟议研究的目的是研究洪水对棉杨养分分配和河岸食物网动态的作用，以及养分可用性对MRG沿线一个关键有害生物的生理限制的作用。洪水对棉杨和食物网络结构的影响将在MRG沿线250公里范围内的八个研究地点进行测量。将在两年内收集棉杨树叶、凋落物、土壤和土壤节肢动物的样本，并分析碳(C)、氮(N)、磷(P)以及13C和15N稳定同位素的自然丰度。在生态系统研究中，结合C/N、C/P和N/P比值使用的C和N稳定同位素是评估营养循环和食物网络结构和功能的重要工具。在一系列实验中，将通过低和高饮食质量以及不同的13C和15N稳定同位素特征处理来测量营养可获得性对陆地等足类营养分配、生长和繁殖的影响。虽然在许多生物体中已经对饮食质量C/N进行了研究，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全面了解干旱和半干旱地区河岸生态系统的生态系统过程，并改善河流对水质、生物多样性和水资源的管理。

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.