SREL Reprint #2504

A multistage approach to population monitoring for rare plant populations

Tom Philippi1, Beverly Collins1, Stephanie Guisti1, and Philip M. Dixon2

1Savannah River Ecology Laboratory, Drawer E, Aiken, SC 29802 USA
2Department of Statistics, 125 Snedecor Hall, Iowa State University, Ames, IA 50011-1210 USA

Abstract: Monitoring populations of endangered, threatened, or sensitive species to provide information on population status and trends is often mandated. Monitoring plant population size over time is not trivial, even though plants are stationary. Demographic status often must be included in monitoring information because individuals of different status contribute differentially to population dynamics. However, the important status may be difficult to census, and resource limitations may preclude complete demographic monitoring of all but the smallest and most important populations. Further, the duration of the census activity controls the power to detect a trend, so comparability with any prior data increases the current value of any monitoring program. The optimal monitoring protocol need not be a single methodology and intensity applied to the entire population. In some cases, multistage sampling, combining extensive plant counts with intensive demographic monitoring of subsets of individuals, can provide more powerful monitoring and simultaneously allow continued use of prior data. The key to this possibility is using reproductive values, estimated from intensively sampled subsets, as weights for the extensive plant counts.

Index terms: demographic monitoring, Echinacea laevigata, multistage sampling, rare plants, reproductive value

SREL Reprint #2504

Philippi, T., B. Collins, S. Guisti, and P. M. Dixon. 2001. A multistage approach to population monitoring for rare plant populations. Natural Areas Journal 21:111-116.

This information was provided by the University of Georgia's Savannah River Ecology Laboratory (srel.uga.edu).