Collaborative Research: Hierarchical Functioning of River Macrosystems in Temperate Steppes - From Continental to Hydrogeomorphic Patch Scales

随着全球气候变化和外来动植物对淡水河流和湖泊的影响，在更大的区域到大陆尺度的宏观系统层面上了解和管理生态系统的必要性变得越来越重要。宏观系统管理需要了解不同层次的空间复杂性（从一条溪流到整个河谷尺度）和生物组织（从种群到生态系统）如何影响河流和湖泊的功能。目前的研究将为18条河流提供这些信息，这些河流平均分布在世界上两个最大的温带草原生物群落之间：北美大平原和欧亚草原（包括蒙古的草原）。该项目将为代表性不足的参与者（特别是农村和美洲原住民学生）提供研究经验，刺激代表性不足的州（EPSCoR）的STEM项目招聘，支持主要本科院校的一些教师和学生，并为两国研究生和本科院校的科学教育做出贡献。这些河流流经这些温带草原生物群系的3种主要生态区域：山地草原灌丛地、矮至高草原和半干旱灌丛地。来自美国和蒙古的科学家和学生将在不同的水文地貌区域对这18条河流的结构和功能进行采样，比如狭窄的、蜿蜒的、编织的和吻合的河道。尽管在生物群系和生态区域类型上具有相似性，但大平原和蒙古草原的河流宏观系统通过生态系统功能在动物、植物和群落方面存在很大差异。这些变化是由气候模式的差异、河流景观改变的程度（如水坝、堤防和河岸改造）以及居住动物群的自然程度造成的。例如，美国的大多数河流都有一些水坝，并引入了许多外来动物，而蒙古绝大多数河流没有水坝，其水生动物几乎完全是自然的，与美国的水生动物不同。此外，蒙古中亚次大陆地区是地球上变暖信号最强烈的地区之一，气温上升速度是北半球整体平均速度的三倍。因此，美国的河流宏观系统可以帮助预测由于大坝建设和某些河流可能引入的物种而导致的蒙古河流的变化，而蒙古宏观系统对更快速的气候变化的反应的知识可以帮助预测未来对美国河流的影响。因此，本项目的目标是：(a)比较和对比两大洲相似生物群系和生态区中河流的等级尺度关系、系统驱动因素和跨尺度相互作用的影响；(b)评估气候变化和人为干扰对这些河流宏观系统的影响。

The need to understand and manage ecosystems at larger regional to continental scale macrosystem levels is becoming increasingly crucial with global climate changes and impacts of exotic plants and animals in freshwater rivers and lakes. Macrosystem management requires an understanding of how different levels of spatial complexity (within a stream reach to entire river valley scales) and biotic organization (populations to ecosystems) affect the functioning of rivers and lakes. The present study will provide this information for 18 rivers spread equally between the two largest temperate steppe biomes of the world: the North American Great Plains and the Euro-Asian Steppes (including those in Mongolia). This project will provide research experiences for under-represented participants (particularly rural and Native American students), stimulate STEM program recruitment in largely under-represented (EPSCoR) states, support some faculty and students at primarily undergraduate institutions, and contribute to scientific education at both graduate and undergraduate institutions in two countries.These rivers flow through 3 major types of ecoregions within these temperate steppe biomes: mountain steppe shrublands, short-to-tall grasslands, and semi-arid shrublands. Scientists and students from the USA and Mongolia will sample the structure and functioning of these 18 rivers in a variety of hydrogeomorphic areas, such as constricted, meandering, braided, and anastomosing channel sections. Despite their similarity in biome and ecoregional types, the river macrosystems of the Great Plains and the Mongolian steppes vary substantially in fauna, flora, and community through ecosystem functioning. These variations result from differences in climatic patterns, the degree of riverine landscape modification (e.g., by dams, levees, and riparian modification), and the naturalness of the resident fauna. For example, most rivers in the USA contain some dams and many exotic fauna have been introduced, while the vast majority of Mongolian rivers contain no dams and their aquatic fauna is almost exclusively natural and different from those in the USA. Moreover, the Central Asian subcontinental area of Mongolia has one of the strongest warming signals on earth, with air temperatures rising three times faster than the overall northern hemisphere average. Consequently, riverine macrosystems in the USA can help predict changes to Mongolian rivers as a result of pending dam construction and possible species introductions to some rivers, while knowledge of responses of Mongolian macrosystems to more rapid climatic changes can help predict future effects in U.S. rivers. Therefore, this project's goals are to: (a) compare and contrast hierarchical scaling relationships and effects of system drivers and cross-scale interactions on rivers in similar biomes and ecoregions of the two continents; and (b) evaluate effects of climatic changes and anthropogenic disturbance to these river macrosystems.