Optimising a Sampling Design for Endangered Wetland Plant Communities: Another Call for Adaptive Management in Monitoring

Abstract

Effective monitoring requires clear questions and a well-designed sampling regime. However, objectives often evolve over time which can render the initial sampling design ineffective. Using a vegetation monitoring program employed in Newnes Plateau Shrub Swamps, Australia, as a case study, we examine a sampling design based on small numbers of 400 m2 plots to assess if it can meet the stated monitoring objectives of detecting significant changes in number and abundance of species per wetland. To determine this, we intensively sampled four monitored wetlands using randomly distributed 4 m2 plots to obtain representative estimates of species composition and abundance. The 400 m2 plots captured 91 % of the common species and a similar proportional distribution of life-forms as found in the 4 m2 plots, but missed 62 % of the sparse species found in 4 m2 plots. Insufficient replication of 400 m2 plots made detection of statistically significant changes at the swamp scale difficult or impossible. Our review showed the weak sampling design was contributed to by 1) an initial lack of clearly stated management triggers and 2) changes in monitoring objectives and triggers over time, without revising the sampling design. We highlight the need for an adaptive approach to monitoring.