Our lab is broadly interested in the mechanisms underlying patterns of plant species distributions, their relationship with ecosystem structure and function, and their response to resource exploitation and global change. We work primarily in the diverse lowland forests of South America, with principal research sites in French Guiana, Peru and Brazil. Current research focuses on four themes.

Functional traits and community assembly

A major objective in our laboratory is to describe functional strategies of tropical trees and their relationships with species performance and distributions to better understand the processes contributing to community structure and ecosystem function. Much of our work over the past several years has been in the context of the BRIDGE project, funded by ANR-France, which seeks to examine models of community assembly in tropical trees. We have conducted complete inventories in 9 one-hectare plots across a range of geological substrates and rainfall, where we climbed and sampled every individual tree and collected herbarium vouchers for botanical determinations. Read more on tropical tree identification here. To date we have sampled nearly 5000 trees representing over 700 species for which we are developing a refined phylogenetic hypothesis based on chloroplast and nuclear markers. In addition, we sampled leaves and wood from each individual and measured functional traits related to resource acquisition, growth and defense. This project represents the largest databases for DNA (cf., Gonzalez et al. 2009, PLoS One ), functional traits (cf. Baraloto et al. 2010, Ecology Letters ) and plant chemical defenses (cf., Courtois et al. 2009, Journal of Chemical Ecology ) of any tropical forest region. The integration of these data have permitted rigorous tests of community assembly, led by former post-doctoral associate Tim Paine, who provides an elegant demonstration of the contribution of environmental filtering to community assembly using functional traits (Paine et al., in press, Oikos ).

Two current projects expand our understanding of plant functional strategies. Along with Claire Fortunel and Julien Ruelle (INRA), we are describing whole plant level variation in functional traits including root and stem tissue densities, anatomy and chemistry, as part of an INRA-funded Package project. Using samples collected from more than 800 species in permanent plots we have installed in lowland forests of Peru and French Guiana, we are seeking to test for coordinated allocation strategies among tissue types and the consistency of this relationship across habitats differing in resource availability and herbivore pressure. And along with collaborators Paul Fine (Berkeley) and John Lokvam (University of Utah), we are expanding our investigations of plant chemical defenses beyond the presence-absence data of volatile molecules to a total metabolite approach for several widespread Amazonian tree lineages (Bombacoideae, Protieae, Swartzia, Inga, Micropholis, Eschweilera).

Plant-insect interactions and beta-diversity of Amazonian tree lineages

In the lowland Amazon, we observe substantial turnover in tree species composition across the landscape, especially among terra firme, flooded and white-sand forests. The predominant explanation for habitat specialization invokes allocation-based tradeoffs in response to different biotic (herbivores and/or pathogens) and abiotic (nutrient limitation and drought stress) selection pressures. Along with Paul Fine, we have been working since 2007 on a US-NSF-funded project in Peru and French Guiana to test the growth-defense trade-off for habitat specialization in Amazonian trees. A major portion of this project involves the characterization of tree-phytophagous insect interactions across environmental gradients. Current PhD student Greg Lamarre is leading this work, with three objectives. First, we are characterizing insect community structure across wide gradients of soil resource availability in Peru and French Guiana, using a suite of insect trapping methods and a network of international collaborators. Read more on Insects here. Second, we are monitoring leaf production and herbivory rates on common species and focal tree genera across this same gradient. Finally, we have established a reciprocal transplant experiment across habitats and countries that includes an herbivore exclusion treatment to conduct a controlled test of herbivory rates and their consequences for plant performance across the geographic and environmental gradient.

Biodiversity, global change and forest management

Our laboratory works actively with government and non-government partners to ensure that the research we conduct on biodiversity can be applied to mitigate the threats of global change on ecosystem services furnished by tropical forests. In French Guiana, we have recently completed a project in collaboration with the regional government and the forest service to examine impacts of selective logging on biodiversity and ecosystem services, resulting in an updated guide for silvicultural practices in addition to several academic publications. We currently have two projects underway in collaboration with these partners. First, with funding from the French Ecology Ministry, we are integrating current information on tree biodiversity and carbon stocks to develop a conservation planning GIS database and planning map for the spatial distribution of these two important ecosystem properties across all of French Guiana (read more here). We are working with collaborators on other taxonomic groups to expand this work to include insects, birds, reptiles and amphibians, and mammals beginning with a pilot study to design appropriate sampling protocols, in the Nouragues Reserve. These results will be used to plan future conservation areas and to revise regulations for existing areas. A second project we have recently initiated builds on our previous work to model scenarios of climate change on services provided by tropical forests. We are integrating our long-term permanent plot data and environmental measures with our functional trait databases to develop predictions for forest structure and composition under different future climate scenarios (read more here).

Integrative studies of socio-ecological resilience, conservation and development

In collaboration with colleagues at the University of Florida and a consortium of local partners integrating biophysical and social sciences and development, we have worked since 2005 to address impacts of the highway paving in the southwestern Amazon in Peru, Bolivia and Brazil. We are currently completing a large interdisciplinary project funded by the Humans and Social Dimensions section of US-NSF to examine social and ecological resilience in forest communities of the southwestern Amazon where the transnational highway has recently been paved. The project integrates remote sensing analyses with community and household inventories and descriptions of forest structure and plant diversity. We work with botanical teams at three participating universities in Puerto Maldonado, Peru (UNAMAD); Cobija, Bolivia (CIPA-UAP); and Rio Branco, Brazil (UFAC). Read more on botanical training here. Along with collaborating professors from the herbaria of the three institutions, we have built student teams that have now established more than 75 new permanent plots in the region (see Plots). We are integrating this information with the remote sensing and interview data to test for effects of connectivity to population centers on forest structure and biomass, commercial resources, and species composition.