Reproducibility of Emergent Plant Mapping on Lakes

Abstract

Bulrushes Schoenoplectus spp. are widely distributed emergent plants that provide important fish habitat. Despite their importance, the precision of aquatic plant surveys conducted within lakes is rarely studied. Reproducibility of field-based bulrush stand coverage was assessed by using three different surveyors to conduct repeated delineations of bulrush stands in five north-central Minnesota lakes. Lakes were mapped by means of Global Positioning System delineation. The reproducibility trial of this study demonstrated that coverage mapping of bulrush stands could be completed in a timely manner and with reasonable precision. No significant differences were found among surveyor estimates of whole-lake bulrush stand coverage. The ability to detect a change in bulrush coverage over time appears to depend on the extent of mixed stands of bulrushes and perhaps on stand size. For lakes with monospecific bulrush stands, it may be reasonable to detect a whole-lake change of 10% or greater by using the techniques described here.

Received July 28, 2010; accepted December 6, 2010

ACKNOWLEDGMENTS

We thank Ray Valley for advice and for reviewing an earlier draft of the manuscript; we are also grateful to Stephanie Simon for providing data from past mapping efforts in the study lakes. Three anonymous reviewers improved the manuscript.