Monitoring riparian restoration to ensure recruitment of large woody debris in Haida Gwaii, British Columbia

Abstract

Monitoring is a fundamental aspect of restoration, as it determines when the restoration objectives have been met. As restoration objectives are not universal, monitoring needs to be included in the development and design of each restoration project. We assessed the effectiveness and efficiency of a forest stand dynamic monitoring plan, developed for use with riparian restoration occurring on Lyell Island, Haida Gwaii, British Columbia. The restoration objective is to accelerate the development of late-successional forests for the benefit of riparian wildlife species and recruitment of in-stream large woody debris, which specifically provides essential habitat for a variety of fish species. In this study large woody debris (LWD) is referred to as downed wood greater than 7.5 cm in diameter. Prior to the start of riparian restoration, two watersheds were quantified for their stand structure and composition using the forest stand dynamic monitoring plan. An error analysis of these data was used to assess the sampling efficiency of the monitoring plan. The design of the monitoring plan was found to be efficient at monitoring the riparian forest stand dynamics (with seven or eight plots per site sufficient to evaluate stand basal area and stem density to within 10%), but not woody debris volumes (for which deviations >10% were found even with 14 plots per site). Incorporation of additional line transects or adoption of more efficient sampling methods for woody debris (such as diameter or length relascope methods) is suggested as a means of enhancing large woody debris sampling efficiency.