Modeling the future redistribution of pinyon-juniper woodland species

Predicting the effects of future climate change on a plant species requires knowledge of the plant’s current distribution, its climate tolerances, its migratory and successional responses to change, and the geography of future climates.  We describe new techniques for such modeling and demonstrate their application using the dominant species of the pinyon-juniper woodland of Arizona and New Mexico: Colorado pinyon pine (Pinus edulis) and one-seed juniper (Juniperus monosperma).  The results for pinyon suggest that over the next 100 years its range will contract throughout Arizona, Utah, and southern New Mexico, but will expand in Colorado and northernmost New Mexico.  In contrast, the results for juniper show a range contraction around its periphery and an expansion at the center of its current range across north central Arizona and New Mexico.  These results are coincidentally similar to ongoing population shifts by these two species.  There has been extensive mortality recently in pinyon throughout Arizona and New Mexico, and juniper has been expanding into mid-elevation grasslands of northern Arizona and New Mexico.  These results imply that modeling ecosystem change at the community or association level would be inappropriate since two current community co-dominants may respond to global warming in separate ways forming assemblages that are disharmonious in our current classification schemes.