PARENT SESSION
Poster Session #64: Long Term Ecological Research.
Friday, August 9. Presentation from 8:00 AM to 9:30 AM. Exhibit Hall B & C, TCC

Quantifying 100 years of assemblage dynamics in a Sonoran Desert plant community: Assessing the role of climate, site specific and biotic interactions.

Weiser, Michael^*,1, Enquist, Brian^1,2, Betancourt, Julio^3,4, Huxman, Travis¹, Van Dyken, J. David¹, ¹ University of Arizona Department of Ecology and Evolutionary Biology, Tucson, AZ² Center for Applied Biodiversity Science, Conservation International, Washington, DC³ U. S. Geological Survey, Desert Laboratory, Tucson, AZ⁴ University of Arizona Department of Geosciences, Tucson, AZ

ABSTRACT- A central focus in community ecology is to highlight the fundamental processes dictating local community composition and structure over space and time. We used multivariate techniques to quantify assemblage dynamics over time in permanent plots measured repeatedly over a century on Tumamoc Hill (Desert Laboratory), a Sonoran Desert reserve on the west side of Tucson. Specifically, we examined the importance of maturation, climate, position on the landscape, and stochastic effects on assemblage structure. Further, we tested whether the composition in each plot has exhibited divergent or equilibrium dynamics over time. Our results show that each of the long-term plots is characterized by dynamic change in species composition and abundance. Each of the long-term plots has continued to diverge in composition over time, as reflected by multivariate trajectories. However, the rates of assemblage change are quite variable and reflect important site/species specific differences. Additional analyses assess the importance of position on the landscape (slope vs. flats), species-specific responses to recovery from disturbance and habitat preference, and climatic variability. Understanding the dynamical behavior of assemblages over multiple decades may be essential to predict species and assemblage level responses to both periodic and directional climate change.

KEY WORDS: assemblage, dynamics, desert, plants