Project Summary

Studies of natural perturbations help us understand how plants ecologically and/or evolutionarily respond to climate change. Since the eruption of Sunset Crater that denuded 2,000 km2 and ended in about 1300AD, colonizing plants have had only a few hundred years to adapt to this hotter, dryer, and nutrient-poor cinder environment. During the past 15 years we have examined how these environmental stresses have affected pinyon pine, Pinus edulis, a dominant tree in the Southwest, and their dependent community members. Compared to trees growing in low stress sandy-loam soils, trees growing in cinders produce less defensive resin, suffer chronic insect outbreaks, and suffer corresponding declines in mycorrhizal mutualists, growth and cone production. This in turn affects birds and mammals dependent upon pinyon seeds for their survival. Associated changes in tree genetics suggest that the selection pressures imposed by this new environment have resulted in genetic adjustments in the plant population. The distributions of dependent mycorrhiza, arthropods and vertebrates map onto the underlying genetic structure of the plant population. Our work and on-going collaborations will address the following issues:

1. Are there spatial and temporal differences in the population dynamics of herbivores that differ in major life-history traits?

2. Does developmental resistance to one herbivore result in increased susceptibility to another herbivore?

3. Is there a cost to herbivore resistance (i.e., reduced growth & reproduction)?

4. How do species respond to rare events?

5. How do environmental stress and plant resistance interact to affect biodiversity (300 species arthropods, 50 species mycorrhiza, 600 species microbes)?

6. Using our current long-term data to calibrate dendrochronology and stable isotope studies, how will reconstruction of past limates and events (up to 40,000 yrs ago) compare with that observed today?

7. How has environmental stress, pest outbreaks and plant resistance interacted to select for new strains and species of mycorrhiza and microbial mutualists at Sunset Crater?

8. Using 600 AFLP DNA markers to examine the genetic makeup of pinyons at Sunset Crater, how has hybridization and introgression with another pinyon species affected the ability of pinyons to locally adapt to this new cinder environment?

9. How does chronic herbivory affect nutrient cycling at Sunset Crater?

Because the Southwest has experienced general warming since the beginning of record keeping and is currently suffering a 100-year record drought, by contrasting Sunset Crater with adjacent less stressed control sites we ask, "Is Sunset Crater an analogue to global climate change and if so how can it be used to predict the ecological and evolutionary impacts of continuing warming trends? We develop how long-term monitoring of individual trees and the continuation of our long-term experiments is being used by ecologists, physiologists and geneticists to study the pinyons and their dependent community members to understand this ecosystem.