Resilience and the Rates of Recovery of Small Streams Along a Gradient of Riparian Management Intensity

We assume that riparian management mitigates the impacts of upslope forest harvesting and promotes the recovery of streams from any associated negative effects.  However, we know very little about the resilience of flowing water ecosystems to such disturbances and the rates of recovery processes.  Using a an experimental gradient of the extent of riparian protection along small streams, some processes, e.g. organic matter inputs and shading of long-wave radiation recover in coarse terms very quickly.  The recovery of these processes comes largely from rapid infill of shrub layer vegetation with or without buffers along small streams where canopy closure is possible even from shrubs.  However, other ecosystem attributes, such as fish populations and invertebrate assemblages are less quick to recover.  One possible expectation is that the systems are fully recovered by the time of the next perturbation, but this has never been examined and if this is not the case we may slowly erode the ecosystem’s resilience in the face of such impacts.  Two other issues remain somewhat intractable given our current understanding.  First, we cannot adequately address the impacts on less common species and their rates of recovery simply because of sampling limitations, while these might be the most sensitive species, at least in part due to their rarity.  And second, the background landscape is not stationary and the potentially diminishing amounts of refuge habitats may further reduce the resilience of stream ecosystems by reducing rates of recolonization. Issues of sustainable forest management will need to consider the challenge of large-scale changes in resilience and recovery of stream ecosystems as a key measure in the evaluation of the effectiveness of protection of freshwater.