Role of Riparian Stream Shading on Stream Function and Implications for Catchment Management

ABSTRACT: Riparian shade within the small stream network (SSN) plays a key role in regulating light and water temperature, which mitigates catchment stressors such as nutrient enrichment. Small streams, with their narrow channels and high surface area-to-volume ratio, can be effectively shaded by bankside vegetation, influencing instream processes. Achieving adequate shading using appropriate bankside species may therefore present as an advantageous method to mitigate negative impacts of agriculture land use—the major pressure within SSN—on instream ecology, while providing other co-benefits for habitat and biodiversity. In contrast to protocols focused on managing nutrient source and transfer, as described through the nutrient transfer continuum, offer strategies to mitigate the ‘impact’ of overland transport and entrained nutrients, by imposing light limitation. This mitigation application of shading is less developed and not widely applied compared to other riparian strategies. The aim of this review is to improve understanding of the role of riparian shade on stream processes and ecological function; examine factors including vegetation type, width, height and density; identify knowledge gaps, and propose a conceptual framework for effective catchment management.