Spatio-temporal variability in alpine plant species composition on Niwot Ridge, Colorado

Poster Number: 
Presenter/Primary Author: 
Hope Humphries
Christophe F. Randin
Nigel G. Yoccoz
Katherine N. Suding

Spatial and temporal changes in alpine plant species composition were analyzed at the landscape, plant community, and individual species levels. We standardized field observations for 88 gridded vegetation plots sampled in 1990, 1997, and 2006 on Niwot Ridge, Colorado and developed spatial environmental data for the study area (snow cover, growing-degree days, time of meltout, and solar radiation). At the landscape scale, growing-degree days increased from 1990 to 2006, while the snow-covered period decreased and meltout occurred earlier. Partial triadic analysis (PTA) revealed a consistent, although small, directional change in species composition from 1990 to 2006 at the landscape level. Similar results were found for PTA conducted at the community level, except for wet meadow. Individual species differed in the degree and direction of changes in cover over time.