Seeing the trees in the forest when estimating riparian shade

摘要

Riparian forest management is impacted by requirements to provide stream shading. Models of riparian shading assume a simple opaque wall of trees adjacent to a stream, the "view to sky" model, or uniform light transmission properties for the forest canopy and understory adjacent to a stream. These approaches fail to recognize the discrete nature of the trees within a riparian forest, including gaps and opaque boles. Advances in desktop computing power allow the estimation of shade using individual trees in a riparian forest. A potential shade model was implemented using ray tracing within a bootstrap simulation framework to approximate the distribution of stream shading that could be provided by a riparian forest. The view to sky shade model, the uniform property shade model, and an individual tree shade model are compared using two management scenarios to identify strengths and weaknesses of the three shade modeling approaches.