A Method for Monitoring Long‐Term Population Trends: An Example Using Rare Arctic‐Alpine Plants

• Published in: Ecological Applications
• Main Authors: Lesica, Peter, Steele, Brian M.
• Format: Article in Journal/Newspaper
• Language: English
• Published: Wiley 1996
• Subjects: Global warming; Tundra
• Online Access: http://dx.doi.org/10.2307/2269491; https://api.wiley.com/onlinelibrary/tdm/v1/articles/10.2307%2F2269491; https://esajournals.onlinelibrary.wiley.com/doi/pdf/10.2307/2269491

Populations of arctic‐alpine plants at the southern periphery of their range should respond rapidly to projected global warming. We established a study to monitor the density and reproductive effort of six such species in tundra of Glacier National Park, Montana to help project the fate of these species in the center of their range. For many species, detecting long‐term population trends is confounded by short‐term variation. Our study design employs temporal resampling of permanent plots on multiple sites and a repeated‐measures model that accommodates the effects of high frequency variation and allows assessment of the significance of long‐term trends. Statistical analysis compares site‐specific estimates of annual mean density between two time periods and uses between‐plot, within‐site, within‐year variation to estimate error. Power calculations using data from the 3‐yr baseline period indicate that measurements of fecundity will be less sensitive for detecting long‐term trends than measurements of plant density. Furthermore, our results suggest that perennial species of closed‐turf communities may be better bioassays of long‐term change than annuals or species of open, ephemeral microsites.