My research examines feedbacks between people and the biosphere, including studies of energy, land use, and climate change. I am currently Director of Duke's Center on Global Change and Duke's Stable Isotope Mass Spectrometry Laboratory. In the quest for solutions to global warming, I also direct the Department of Energy-funded National Institute for Climatic Change Research for the southeastern U.S. and co-directed the Climate Change Policy Partnership, working with energy and utility corporations to find practical strategies to combat climate change.
The renewable freshwater cycle in units of thousands of km3/yr (Jackson et al. 2001)
The Duke Free Air CO2 Enrichment (FACE) experiment studies how elevated carbon dioxide and nitrogen affect a Loblolly Pine (Pinus taeda) plantation with a naturally succeeding understory. My research at FACE focuses belowground, on the effects of elevated CO2 and N on root biomass and soil respiration. Surprisingly, even after 12 years, the stimulation of root growth and respiration under elevated CO2 is still increasing. N fertilizer decreases both fine root biomass and soil respiration, but increases coarse root biomass. In the lab, I maintain a handful of websites, run various analytical instruments, and serve as lab manager. I also enjoy the role of resident naturalist, specializing in birds, lepidopterans, and woody plants.
Measuring soil respiration at the FACE site
Natural gas could be an important energy source in the future. Through my research, I seek to better understand the environmental tradeoffs involved in the extraction, transportation, and combustion of natural gas. When combusted, natural gas emits less carbon dioxide per unit of energy gained than other forms of fossil fuel. However, methane itself is a powerful greenhouse gas. Leak rates from natural gas distribution systems, both rural and urban, remain uncertain, which makes it difficult to tell how the greenhouse warming footprint of natural gas compares to other fuels. Extraction of natural gas through hydraulic fracturing is poised to become a major fuel extraction technology worldwide in the near future, but questions remain about what environmental consequences, if any, this practice entails. My field research focuses on groundwater testing in the Marcellus Shale of Pennsylvania and New York, background water sampling in the Sanford Basin of central North Carolina, and urban air measurements in Boston, Massachusetts.
My research can be broadly classified as physiology and ecology of tree and shrub species, population dynamics of those species and plant functional morphology (i.e. adaptive traits). Currently, my primary focus is on water transport (hydraulic architecture and function) in tree and shrub species Ongoing projects in this area include impacts of leaf hydraulic architecture and function on gas exchange and growth, mechanisms of drought-induced tree mortality, embolism repair mechanisms and efficiency and the coordination of root, stem and leaf water transport. My other interests include physiological ecology and population biology of young seedling establishment, which is critical for forest regeneration and migration with climate change.
Measuring leaf hydraulic conductivity
I study the influence of plants on the cycle of materials (water, nutrients, salts, carbon) in terrestrial ecosystems; the impact of vegetation changes (afforestation of grasslands, deforestation and cropping in forests, overgrazing degradation) on ecosystem functioning, its interaction with the hydrological system; biological carbon uptake and sequestration; biogeography of terrestrial ecosystems; and productive systems design. Approaches and methodology include: hydrological observations, physical and chemical determinations on soils and sediments, ecophysiological measurements on plants, biophysical characterization of the terrestrial surface with remote sensing, simulation models, and stable isotope natural abundance.
Eucalyptus plantation and adjacent grassland in Uruguay
I am interested in how humans affect terrestrial biogeochemical cycles at many scales, from the rhizosphere to the ecosphere. Particularly, I am interested in how spatial pattern in tropical agriculture-forest mosaiclands affects soil processes and ecosystem services. I also have a longstanding interest in sustainable agricultural development. As a first-year student in the lab, I'm getting my feet wet in a variety of projects and working to turn my interests into a research program.
Interests: water and salts dynamics in arid to humid ecosystems, groundwater-vegetation interactions, biogeochemistry.
I am interested in the reciprocal influences between water/salts dynamics and vegetation. I am currently focused on the interactions between shallow groundwater and crops in the flat humid landscapes of the Pampas. I also study the effects of land-use on the water cycle and energy balance components and the potential climatic impacts of land-use changes. The approaches and methodologies I used involve: remote sensing and GIS, hydrological observations, physical and chemical analysis in soil, water and sediments, natural and artificial water tracers and modeling, among others.
Interests - biogeochemistry, afforestation impacts, atmospheric deposition
I am analyzing biogeochemical impacts of afforestations in Uruguay and Argentina, performing mass balances of C, N, Na, Ca, Mg, K, Cl, P, and S, and evaluating the relative impact of alternative plantation species (Eucalyptus and Pines). I am also evaluating atmospheric depositions over souther South America with a network of collection sites, with special interest in tracking spatial redistribution of nutrients and water in the region. Finally I am also analyzing the C cycle in agricultural systems with a special emphasis in developing C sequestration strategies in both food and biofuel crop systems.
Eucalyptus plantation and adjacent grassland in Uruguay
My research interests include biogeochemistry, global change ecology, and geospatial analysis. I am specifically interested in modeling human disturbances of biogeochemical cycles across multiple scales, from an individual tree to a regional level. Currently, I am assisting on a project to estimate drought induced tree mortality in Texas using remote sensing. As extreme weather events such as drought become more common, it will be important to model the net carbon costs associated with droughts as well as the ecological impacts such as altered species compositions.
I conduct research on policy analysis for a low-carbon energy system. I have published policy reports on wind power, energy storage, electrical transmission, and peer-reviewed articles in technology innovation policy, solar energy, electric vehicle, pumped hydroelectric energy storage, nuclear power, and methanol fuel. My recent focus is on the development in China’s energy policy, including the efficiency improvement in the coal-fired power sector, the disturbances in coal market, and the global implications of China’s unique institutional context and policy approaches.