Key Landscape Factors Influencing Stream Physical Habitats Across the Brazilian Neotropical Savanna

Abstract

Improved management of small headwater streams in the Cerrado (Neotropical Savanna) biome in Brazil is necessary given the significant landscape transformations caused by anthropogenic activities in recent decades. Thus, we aimed to determine the relative influence of the leading natural landscape features and anthropogenic pressures on the physical habitat structure of 174 headwater stream sites distributed in five hydrological units across the Cerrado. We used multivariate statistical analysis at four different spatial extents to establish likely causal relationships between landscape explanatory variables and 14 stream physical habitat response variables. At the biome extent, natural landscape variables explained only 13% of the variation in the physical habitats, but anthropogenic variables explained no variation. On the other hand, within the hydrological units, natural landscape variables explained 17–31% of physical habitat variation, and anthropogenic activities explained 0–27%. Regarding the influence of spatial extent, catchment variables were most important at the biome extent and within hydrologic units, but riparian and local variables were also significant within hydrologic units. Overall, terrain and drainage features likely drove differences in stream physical habitat in the biome and hydrologic units. Although vegetation cover and anthropogenic activities at the catchment, riparian zone, and site were usually of secondary importance, they occurred in all hydrologic unit models. For conserving and rehabilitating Cerrado headwater streams, it is essential to consider spatial connectivity and processes from catchment to local levels and large hydrologic units as largely independent systems.