Geocode-based Aquatic Habitats in Hierarchical System of the Yellow River Basin

Riverine systems are primary habitats for aquatic species. Great efforts have been made to understand interaction between aquatic organism and various environmental factors in specific reaches of a river, yet little was known about how to identify habitats in river networks. In this paper, a comprehensive approach was proposed for identification of aquatic habitats in hierarchical river systems in terms of integrated geocodes synthesized through over-layer of multiple factors such as geologic periods, climatic conditions, water sources, geomorphic characteristics and river patterns. Using this approach in the Yellow River basin over an area of 758,600 km2, six groups of aquatic habitats were classified by clustering of 85 geocodes, and 313 sub-habitats were further identified by considering both surface composition (e.g. lithological features and soil texture) and topographic property (e.g. elevation and slope) in the loess geomorphic regions. Consequently, the contribution of the headwater streams to diversity of aquatic habitats among rivers and mid-sized rivers to the diversity within a river has been revealed by coupling of the geocode-based habitats and the river networks. The present study is of significance to efficient capture of habitat diversity and better understanding of biodiversity in rivers of different stream orders.