Peru

Destructive fires have recently become a major problem along the upper Ucayali River in the lowland Peruvian Amazon. For centuries burning has been used to manage agricultural fields and, more recently, to clear and clean pastures. While these managed areas have traditionally been mosaics of small fields, diverse gardens, and extensive mature forests, increased activity in large-scale agriculture and ranching and changes in land-use management patterns from migrant landholders are rapidly transforming the landscape. These transformations are further compounded by the uncertainties of a changing climate. The project uses an interdisciplinary approach to investigate how changes in the incidence, size and severity of escaped fires are linked to ongoing processes of change in land use, migration, urbanization, and climate. Field data, climate data, and data gathered using remote sensing techniques will be used to develop a model of fire risk as a function of social, demographic, land use, and climatic factors. The complex processes and interrelationships explored in this project will result in better understanding of how biological, social, and atmospheric processes are coupled to change the danger of fire damage in evolving tropical landscapes. Weblink coming soon.

Our research focuses on understanding the socioeconomic, physical, and ecological mechanisms that govern the dynamics of secondary tropical forests. Using a multi-disciplinary, quantitative approach, we aim to forecast the dynamics of secondary forests at multiple spatial scales. We focus on two classes of mechanisms: the drivers of forest recovery at a landscape-scale and stand dynamics of second-growth forests. We are particularly interested in interactions between human land use and natural disturbance (i.e., hurricanes).

Deforestation in the tropics is continuing at rates that lack historical precedent, resulting in the fragmentation of species-rich rain forests. One of the most common consequences of fragmentation is reduced seedling establishment, particularly for species found in the forest understory. In collaboration with Dr. Emilio Bruna, we are examinig the relative importance of variousbiotic and abiotic factors on the recruitment of Heliconia acuminata, an Amazonian understory plant. We are also ascertaining how these processes are altered in forest fragments at the Smithsonian Biological Dynamics of Forest Fragments Project. We use field studies coupled with an innovative spatially-explicit modeling framework. By advancing our understanding of these mechanisms, this work will help improve management and conservation efforts for tropical forests.

Chile

Rapid economic development has led to a replacement of native forest with plantation and a tenfold increase in the number of salmon farms in the southern regions of Chile. We are examining the effects that these developments are having on land-water-atmosphere interactions.

Effects of neighborhood composition and structure on plant nitrogen allocation in a grassland community

Allocation of nitrogen to seeds at senescence in annual plants in California grasslands prevents leaching losses from litter and promotes high seedling density. As self-thinning occurs, seedling size asymmetries result in the death of less competitive plants, while providing a steady flow of nitrogen to remaining plants. The magnitude of nitrogen allocation to seeds is determined, in part, by neighborhood structure, providing a strong and intriguing link between population and community dynamics and nutrient cycling in this system. For this project, we are using a combination of game-theory models and greenhouse studies.

Collaborator: Dr. Valerie Eviner (University of California, Davis)