COS 75-2
The relationship between recent climate, biogeography, and phenology of trembling aspen (Populus tremuloides Michx.) communities of the Rocky Mountain region
Trembling aspen (Populus tremuloidesMichx.) occurs over wide geographical, latitudinal, elevational, and environmental gradients, making it a favorable candidate for a study of phenology and climate relationships. Aspen forests and woodlands provide numerous ecosystem services such as high primary productivity, species and structural diversity, and snow-water retention. Yet aspen-dominated systems are experiencing declines in the western United States due to climate-induced drought conditions during the last decade. We correlated environmental variables (precipitation, temperature, snow-water equivalent (SWE)) and biogeography (elevation, latitude, soil water-holding capacity) to the phenology of aspen forest and woodland communities of the Rocky Mountain region between 36°N and 49°N Latitude. The remote sensing-based data were compiled for selected sites having more than 75% cover by aspen woodland communities between the years 2001 and 2012. Our objectives are 1) to determine the aspen land surface phenology using the Normalized Difference Vegetation Index (NDVI), end of season time (EOST), start of season NDVI (SOSN), start of season time (SOST), and time-integrated NDVI over a 12-year record; and 2) to determine the important climatological and biogeographical influences to aspen seasonal phenology.
Results/Conclusions
Our results from a pilot study in southwestern Colorado demonstrate linkages between these environmental variables on the onset and cessation of annual growth of aspen. We found mean spring maximum temperature and SWE to be significantly correlated to SOST indicating that warm dry spring weather promotes early growth. We also found that mean fall minimum temperature and mean fall temperature difference (maximum-minimum) to be significantly correlated to EOST, confirming that warm days and cold nights influence changes in fall foliage