Riparian Management: Alternative Paradigms and Implications for Wild Salmon

Abstract

Atlantic salmon spawn and rear in watersheds subject to a long and complex history of land-use change. The implications of these changes for salmon habitat and production in turn depend, to a large extent, on the manifestation of these changes in riparian zones, which exert significant control over the physical and chemical environments of rivers and streams. There has been considerable effort spent on conserving, restoring and managing riparian zones to improve habitat conditions for salmon, but there is considerable uncertainty as to the effectiveness of these actions. In this chapter, I consider riparian management strategies based on species requirements, where the goal is increased fish abundance and production, to strategies based on process restoration, where the goal is to restore key processes that have been altered by human activity, with the expectation that these processes will in turn increase productivity and diversity. I argue that effective riparian management should include both process-and species-oriented approaches. In order to demonstrate how this integration may work, I provide a case study of a riparian and instream habitat management programme for large woody debris (LWD) restoration in Atlantic salmon rearing streams in the northeastern US. In this study forest growth models and riparian and instream surveys are used to quantify expected LWD loads under different forest and habitat management scenarios. These results provide targets for management experiments (LWD additions and riparian forest prescriptions) which, in turn, are monitored to assess habitat and fish population response. This combined approach allows us to both evaluate established management strategies and learn more about the mechanisms by which riparian management affects fish populations. Salmonid Fisheries: Freshwater Habitat Management Paul Kemp

A Lidar‐derived Evaluation of Watershed‐scale Large Woody Debris Sources and Recruitment Mechanisms: Coastal Maine, Usa

“…However, given the protected status of the riparian zone throughout the basin (Maine DEP, ), predicted increases in tree size will likely expand this zone of influence. Under these old‐growth‐like conditions, wood will likely play a greater role in the system, a finding consistent with previous modelling (Nislow, ) and empirical work (Keeton et al , ) in the northeastern region.…”

“…In systems where appropriate reference conditions are not available, forest vegetation simulation models can then be used to set realistic basin-wide targets for wood recruitment, as well as provide guidelines for active wood restoration projects designed to provide accelerated recovery. This approach was previously used to determine that current wood loads in the streams in the Green Mountains of central New England, USA, were well below predicted old-growth conditions and that current active restoration projects were within the range of these predicted loads (Nislow, 2010).…”

A conceptual model of riparian forest restoration for natural flood management

“…A full model description is included in Lester et al , (). In previous applications of NE‐CWD, in‐stream wood loads were shown to be much higher than those found in natural managed forest streams, with highest accumulation rates found for 100–150 years after stand initiation (Nislow, ). However, the disparity between modelled and managed loads was explained in terms of the legacy of previous deforestation and forest management which have exerted a strong long‐term influence on the structure and function of ecosystems (Jones et al , ; Bragg, ; Nislow, ).…”

“…In order to derive predictions of in‐stream large wood loads and the complexity of floodplain surfaces over time following a programme of riparian forest regeneration, a numerical modelling approach was adopted to simulate forest growth and succession. Numerical models of riparian forest growth are comparatively rare worldwide and none exist for a UK context, therefore a numerical model for the North‐Eastern United States (NE‐CWD, Nislow, ) was used, which incorporates growth, dead wood and riparian dynamics of both broadleaf and conifer species (Lester et al , ). The use of numerical models is well established to predict upland forest plot growth and harvest yields (e.g.…”

“…As knowledge of the benefits of mature floodplain forests has increased, policy and practice both in the United States and Europe has turned towards encouraging riparian forest restoration and protecting riparian forests; initially for ecological reasons (Naiman and Décamps, ; Broadmeadow and Nisbet, ; Nislow, ), and at relatively small scales (Nislow, ), but more recently as a component in natural flood risk management, or ‘working with natural processes’ (Defra, ; Lane, ; Mondal and Patel, ; Nilsson et al , ), and advocated at entire catchment scales.…”