Scaling spatial pattern in river networks: the effects of spatial extent, grain size and thematic resolution

Context: Understanding how spatial pattern changes with scale can provide insights into its relationship with ecological processes. In riverine landscapes, spatial pattern could scale differently from other well-studied landscapes because of their dendritic form. Objectives: The objectives of this study were (1) to assess how spatial pattern of hydrogeomorphic habitat patches (HGP) change with spatial extent, grain size, and thematic resolution, and (2) to quantify how spatial pattern in river networks varies across the contiguous United States (CONUS). Methods: We identified hydrogeomorphic patches in river networks located in different ecoclimatic domains. We then quantified spatial pattern within each river network using a suite of landscape metrics and investigated scaling relationships for each component of scale. We also assessed whether watershed area, river network length, and drainage density were related to spatial pattern among river networks and explored regional differences in the hydrologic, geomorphologic, and climatic variables that differentiate HGP types. Results: When predictable, scaling relationships within river networks followed either linear, logarithmic, or power functions. Among river networks, spatial pattern was related to total network length, catchment area and drainage density. Rarely were HGP types in different networks characterized by the same suite of hydrologic, geomorphologic and climatic variables. Conclusions: In riverine landscapes, there are a variety of relationships between spatial pattern and scale. The scaling functions we present can provide a concise description of scale dependency in these landscapes and improve our ability to synthesize information across scales.