Detection and Monitoring of Invasive Exotic Plants: A Comparison of Four Sampling Methods

Abstract

The ability to detect and monitor exotic invasive plants is likely to vary depending on the sampling method employed. Methods with strong qualitative thoroughness for species detection often lack the intensity necessary to monitor vegetation change. Four sampling methods (systematic plot, stratified-random plot, modified Whittaker, and timed meander) in hemlock and red oak forests in the Delaware Water Gap National Recreation Area were compared for their ability to detect and monitor understory exotic invasive plant species. The timed-meander method best detected exotic invasive plants and documented richness. The stratified-random method was similar to the timed-meander method in terms of detection of exotic invasives and defining richness, but also provided estimates of species abundances and diversity. An initial combination of the timed-meander and stratified-random sampling designs followed by monitoring with the stratified-random method is suggested as a standard approach.