Climate and species traits shape responses of alpine flora in the US Rocky Mountains to a changing world: Analysis of five GLORIA sites across the southern Rockies

Powers, Claire; Borgman, Erin; Doak, Daniel

doi:10.36967/2306920

The Global Observation Research Initiative in Alpine Environments (GLORIA) is a world-wide network of sites dedicated to monitoring changes in alpine flora near mountain tops. In this project we analyzed data collected at 5 sets of GLORIA monitoring sites in the Rocky Mountains of the western USA. Each site was visited between 2 and 4 times in the years spanning 2003 to 2021. These sites include four National Parks (Great Sand Dunes National Park and Preserve, Rocky Mountain National Park, Yellowstone National Park, and Glacier National Park) and one wilderness area in the Pecos Wilderness within Santa Fe National Forest. We focused on testing the climatic sensitivity of the alpine flora as a whole, and the relative responsiveness of plant species based upon their commonness or rarity, their geographic ranges, and other aspects of their life forms and of site characteristics. We find that across all sites and species there is strong evidence for turnover of the flora in the GLORIA sampling areas, with rare species disproportionately increasing over time and common species generally declining. We also find that graminoids and shrubs have increased more than forbs, as has been found or suggested in other studies. Multiple climate variables have significant influence on changes in plant cover. In particular, higher annual precipitation increases abundance, on average. Lower growing season precipitation, higher growing degree days (reflecting both warmer temperatures and more days of higher temperatures), and higher mean temperatures also lead to increasing abundance. Also, species with lower latitudinal ranges tended to increase more over time, while species with more northerly ranges often declined. Within these general trends there are substantial differences between species, as indicated by random species-level effects, but there were no strong patterns in these effects that would suggest additional generalizations between species groups. Beyond our findings regarding the drivers of alpine plant dynamics, we examined factors that could potentially add bias or uncertainty to the data sets and made recommendations regarding data collection going forward. Among these suggestions are: 1) that all the NPS GLORIA teams consider consulting with previous species lists when performing field surveys; 2) that redundant temperature data loggers be deployed by at least two team members at each plot; and 3) that a careful training protocol be developed to better standardize cover estimation across parks and censuses. We expand on these recommendations at the end of report.

Climate and species traits shape responses of alpine flora in the US Rocky Mountains to a changing world: Analysis of five GLORIA sites across the southern Rockies

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