LAUSR

Abstract Our present understanding of the effects of natural and anthropogenic disturbances on aquatic systems in forested landscapes is based on a long history of studies relating physical, chemical and biological variables to biotic responses. The explanatory relationships resulting from this work have proven informative for ensuring environmentally-sound forest management, but such evaluations have not been applied to all forest types and management conditions and rarely in the context of aquatic ecosystem services. In this study, we applied a combination of field measurements and modelling to derive a comprehensive suite of physical, chemical, and biological variables (n = 80) to develop explanatory relationships between these variables and benthic macroinvertebrate community composition of headwater streams in managed forests. The work was conducted in a northern hardwood forest catchment that contains a gradient of disturbance, ranging from undisturbed to actively managed over the past 25 years, and a history of research that has generated an extensive relevant dataset. From among the initial suite of 80 variables, we found that those related to hydrological patterns and processes (i.e. flow variability; conductivity) were most strongly associated with benthic macroinvertebrate community structure. We also found that selection-based forest harvesting had no measurable adverse effects on benthic macroinvertebrate communities. By better defining the relationships between physical, chemical and biological indicators of aquatic ecosystem function, our work provides information required to make effective monitoring and management decisions aimed at ensuring sustainability of forest-based aquatic ecosystem services, particularly in the face of a changing climate.