I am broadly interested in all areas of ecology but especially in the interface between plant population, community, and ecosystem ecology. Biotic interactions, resource availability, and species pools interact to govern the assembly, diversity, and functioning of plant communities. This understanding is key to predicting future changes in ecosystems since biotic interactions, resource availability, and species pool change as a result of global change. Secondly, I am interested in feedbacks through nutrient cycling and density-dependent biotic processes that influence the composition, diversity and the functioning of plant communities. Thirdly, I am interested in understanding the impacts of management and human-induced global changes on biodiversity and ecosystem function and applying this understanding to the conservation and restoration of native plant communities.
I think that changes in biodiversity, either through local extinction or biological invasions, is the single most important and dramatic problem in contemporary ecology, and to understand these changes we need to place community ecology in the context of population and ecosystem processes. I also think that this is essential to study the mechanisms that control species diversity as a way to predict the consequences of global change on diversity. I am interested in testing and developing mechanisms of what controls biodiversity using experimental and observational studies of plant communities in combination with mathematical and statistical models and simulations.
My approach has been to combine observational data with well-replicated field experiments using a theoretical framework. Some of the questions that I am currently working on are:
- How biodiversity in plant communities changes over successional time and how this links with ecosystem carbon and nitrogen cycling
- The relative importance of biotic and abiotic processes that structure biodiversity and that control successional changes in plant communities
- How changes in the environment, such as elevated CO2, fire, nitrogen additions, herbivory and species pools, drive changes in community composition and what the consequences of these changes are for ecosystem dynamics
- How invasive plant species differ from natives, and which traits translate into a competitive advantage and what the consequence of an invasion is for ecosystem dynamics
- The effects of nutrient limitation for diversity, stability and composition of grassland ecosystems
- The interactive effects of carbon dioxide, nitrogen deposition and plant diversity on primary productivity decomposition and soil organic carbon and nitrogen pools
- Carbon sequestration, methane and NO2 fluxes in natural and agricultural ecosystems
- Lastly, I am working with Dr. Koenig on a long-term project to determine which factors influence acorn productivity and oak masting. We are using a 29-year database of acorn productivity of 250 individual trees at a site to determine which factors influence the variability both in time and space that we observe. We expanded our monitoring to 16 additional sites within California. This will allow us to better address regional and statewide scaling issues.