OEB Seminar Series

Paul Moorcroft
Professor of Organismic and Evolutionary Biology
Harvard University, Department of OEB

"The Role of Ecosystem Diversity and Heterogeneity in the Resilience of Terrestrial Ecosystems to Climate Change"

Abstract: Amazon Forests, which comprise approximately 40% of world’s remaining tropical forests and play a vital role in global water, energy and carbon cycling, are predicted to experience both longer and more intensive dry seasons by the end of the 21^st century, However, the climate sensitivity of this ecosystem remains uncertain: several studies have predicted large-scale die-back of the Amazon, while several more recent studies predict that the biome will remain largely intact. In this study, we use an individual-based terrestrial ecosystem model to explore the sensitivity and ecological resilience of Amazon forests to changes in climate. Our results show that water stress operating at the scale of individual plants, combined with spatial variation in soil texture, strongly influence the ecosystem’s resilience to changes in dry season length. In contrast to existing predictions of either stability or catastrophic biomass loss, our analyses indicate that, as a result of ecosystem diversity and heterogeneity, the Amazon forest’s response to a drying regional climate is likely to be an immediate, graded, heterogeneous transition from high biomass moist forests to transitional dry forests and woody savannah ecosystems. Further analyses show that two key characteristics influencing the climatic sensitivity of individuals within the plant canopy are their leaf phenology and plant hydraulic architecture. Finally, I discuss the prospects for remote sensing measurements to improve predictions how changes in climate will affect composition, structure and functioning of forest ecosystems.