Multiple interactions among global change factors

How will the combined influences of warming, snowpack, nitrogen deposition influence alpine biodiversity and the establishment of woody plants? Does the establishment of woody plants feedback to influence these interactions?

Global change is multifaceted, comprising simultaneous changes in many environmental factors, and these factors may have non-additive effects on plant communities. Effects can be non-additive if the response of a community to two simultaneous global change factors is not predictable by the single factor effects.  Quantifying these non-additive effects is essential if we want to be able to forecast species responses to realistic global change scenarios.  We are testing the effects of warming, nitrogen deposition, and snowpack (precipitation) on the plant community and ecosystem function in the alpine tundra.  These three global change factors are all predicted to increase over the next century in the alpine tundra in the Rocky Mountains.  They are also thought to drive another large-scale pattern in the tundra: woody plant encroachment, the increase of woody shrubs in an otherwise herbaceous plant community.  We have set up an experiment manipulating these three factors in all combinations on Niwot Ridge.  We have also planted willow seedlings in the plots to determine which global change factors affect shrub establishment and growth, and eventually how the establishment of woody plants may feedback to affect the alpine plant community and ecosystem function.

People involved: Emily Farrer, Dr. Isabel Ashton (National Park Service, Northern Great Plains Network)