Community responses to river drying in an arid-land ecosystem: a field and experimental study

流经干旱地区的河流为人口和经济增长提供了有限的资源，同时支持着多样化的动植物群落。因此，这些河流往往是密集恢复活动的目标，这些活动可能错误地基于为湿润河流开发的概念。旱地系统不同于内陆系统，因为它们经历了巨大的流量变化，从高洪水到几乎干涸。低流量和河流间歇是常见的现象，干燥事件可能对增强物种多样性很重要，因为它允许分别在高流量和低流量条件下生存的生物共存。然而，流量的季节变化，特别是低流量对水生群落的实际影响在很大程度上仍然未知。为了解决这一知识缺口，将在新墨西哥州的里约热内卢Grande进行实地和实验研究。改变了组成河流的藻类、无脊椎动物和鱼类的生物量和营养成分？美国的食物网将被追踪。宏量营养素，如碳、氮和磷，将被用作示踪剂，以了解自然河流环境中与流量变异和干燥相关的群落变化动态。最后，一项实验研究将操纵在干旱河流环境中似乎强烈影响物种丰度和多样性的关键变量。本研究的结果将有助于制定科学的防御性恢复政策和建立旱地河流的最小流量。制定这种政策对全世界干旱和半干旱地区的经济至关重要。

Rivers that flow through arid lands provide a limiting resource for human population and economic growth while simultaneously supporting a diverse community of plants and animals. Consequently, these rivers are often targets of intensive restoration activities based, perhaps erroneously, on concepts developed for mesic (wetter) rivers. Arid-land systems differ from mesic counterparts in that they experience enormous variability in flows that range from high floods to being nearly dry. Low flows and river intermittency are common occurrences, and drying events may be important for enhancing species diversity by allowing coexistence of organisms that specialize on high- and low-flow conditions, respectively. However, actual effects of seasonal variability in discharge, especially low flows, on aquatic communities remain largely unknown. To address this gap in knowledge, a field and experimental study will be conducted on the Rio Grande in New Mexico. Changes biomass and nutrient composition of the algae, invertebrates, and fishes that make up the river?s food web will be tracked. Macronutrients, such as carbon, nitrogen, and phosphorus, will be used as tracers to understand the dynamics of community changes associated with flow variability and drying in natural river environments. Finally, an experimental study will manipulate key variables that appear to strongly affect species abundance and diversity in drying river environments. The outcomes of this study will aid development of scientifically defensible restoration policies and establishment of minimum flows in arid-land rivers. Development of such policies is of paramount economic importance to arid and semi-arid regions worldwide.