The role of nitrogen in tropical forest recovery from disturbance
David Medvigy, assistant professor of geosciences, and Lars Hedin, professor of ecology and evolutionary biology, are coordinating field- and model-based assessments of the response and resilience of tropical ecosystems to global environmental change. Their study will seek to (1) understand how nutrient feedbacks can affect the strength of the tropical forest carbon sink in the future, and (2) investigate how plant diversity impacts the response of tropical forests to climate change. This project is supported by the Carbon Mitigation Initiative (CMI), a partnership between Princeton University and BP,and by the Princeton Environmental Institute (Grand Challenges) at Princeton University.
Schematic diagram of the forest nitrogen cycle, as implemented in the Ecosystem Demography 2 model.
Amazon deforestation: global climate implications
David Medvigy, assistant professor of geosciences, is investigating how the deforestation of the Amazon rainforest will affect the climate. Conversion of the rainforest to pasture changes how the land and the atmosphere exchange heat and moisture, and hence also temperature and precipitation. Medvigy’s work has recently shown how deforestation of the Amazon can affect parts of the globe that are located far away from the rainforest. Simulations from a variable-resolution atmospheric model (Ocean-Land-Atmosphere Model, OLAM) indicate that the northwest U.S. may become drier in response to Amazon deforestation. Meanwhile, parts of southern South America may experience an increase in cold air anomalies. This research is supported by a grant from the National Science Foundation.
Medvigy, D., R.L. Walko, M.J. Otte, and R. Avissar. (2013) Simulated changes in Northwest U.S. climate in response to Amazon deforestation. J. Climate, 26, 9115-9136. doi: 10.1175/JCLI-D-12-00775.1 (PDF)
In addition to having a local effect (left), Amazon deforestation also sets up atmospheric waves that are capable of traversing the planet (center). These waves set up dry anomalies over the northwest U.S. and wet anomalies south of Mexico (right).
Model simulations indicate that deforestation of the Amazon could mean 20 percent less rain for the coastal Northwest U.S. The figure above shows the change (in millimeters per day) in daily average precipitation after total Amazon deforestation compared to before deforestation. The pink to dark-pink range indicates a drop in precipitation of up 1.6 mm less per day once the Amazon is gone.
Climate Syndromes of Seasonality (Climate SoS)
David Medvigy, assistant professor of geosciences, Ignacio Rodriguez-Iturbe, James S. McDonnell Distinguished University Professor of Civil and Environmental Engineering, and Elena Shevliakova, senior climate modeler in ecology and evolutionary biology, have initiated a study of the seasonality of tropical dry forests. These forests have a pronounced winter dry season and are of great interest due to their significant biodiversity and their provision of numerous ecosystem services. This new project will use models and field observations to understand how recent and future changes in climate seasonality are likely to affect these forests. Support for this work is provided by the Princeton Environmental Institute and the Andlinger Center for Energy and the Environment at Princeton University.
Seasonality of North American forests
David Medvigy, assistant professor of geosciences, and Su-Jong Jeong, postdoctoral research associate, are investigating the environmental drivers of seasonality in the temperate forests of North America. The timing of events such as spring budburst and autumn leaf coloration strongly impact forest carbon budgets, albedo, and other aspects of ecosystem biophysics and biogeochemistry. With support from NOAA/CICS, this project includes analysis of a national database of ground-based observations and the development of new models designed to shed insights on temperate forest seasonality.
Jeong, S.-J., D. Medvigy, E. Shevliakova, and S. Malyshev. (2013) Predicting changes in temperate forest budburst using continental-scale observations and models, Geophys. Res. Lett., 40, doi:10.1029/2012GL054431 (PDF)
Jeong, S.-J., D. Medvigy, E. Shevliakova, and S. Malyshev. (2012) Uncertainties in terrestrial carbon budgets related to spring phenology. J. Geophys. Res. 117, G01030, doi: (PDF)
Red maple budburst date anomalies relative to the 1980-1999 average. (a) Spatially averaged budburst date anomaly simulated for the eastern United States. (b) Spatial patterns of budburst date anomaly simulated for the 2080-2099 period assuming different Representative Concentration Pathways (RCPs).
Forest recovery from insect attacks and fire
David Medvigy, assistant professor of geosciences, is investigating forest recovery from disturbances such as insect attacks and fires. Forests in the eastern U.S. experience periodic gypsy moth outbreaks that often result in substantial defoliation. Defoliation can lead to tree mortality, forest carbon loss, and modified forest hydrology. To investigate these processes, insect attacks have been incorporated into the Ecosystem Demography 2 model. The model is now being used together with field observations from the New Jersey Pinelands to understand the response and recovery of forests from disturbance.
Schäfer, K.V.R., H.J. Renninger, K.L. Clark, and D. Medvigy. (2014) Hydrological response of an upland oak/pine forest on the Atlantic Coastal Plain to drought and disturbance. Hydrological Processes, in press, doi:10.1002/hyp.10104.
Medvigy, D., K.L. Clark, N.S. Skowronski, and K.V.R. Schäfer. (2012) Simulated impacts of insect defoliation on forest carbon dynamics. Environ. Res. Lett., 7, 045703 doi: (PDF)
Simulated changes in forest structure and composition in response to periodic defoliation events. Simulations were carried out using the Ecosystem Demography 2 model. The red trees are oaks and the blue trees are pines.
Day-to-day atmospheric variability and terrestrial ecosystems
David Medvigy, assistant professor of geosciences, is investigating how terrestrial ecosystems respond to day-to-day environmental variability. Because terrestrial ecosystems exhibit strong nonlinear responses to their environment, they are sensitive to climate variability as well as to the mean climate state. We analyzed satellite observations to find that tropical land areas are now experiencing more day-to-day solar radiation variability than they were in the 1980s. This increase in variability is expected to reduce ecosystems’ ability to sequester carbon from the atmosphere. Ongoing research is focusing on the mechanisms that drive changes in atmospheric variability as well as the consequences for terrestrial ecosystem structure, composition, and functioning.
Medvigy, D., and C. Beaulieu (2012) Changes in daily solar radiation and precipitation coefficients of variation since 1984. Journal of Climate, 25, 1330-1339.
Medvigy, D., S.C. Wofsy, J.W. Munger, and P.R. Moorcroft. (2010) Responses of terrestrial ecosystems and carbon budgets to current and future environmental variability. Proc. Natl. Acad. Sci. USA, 107 (18), 8275-8280. (PDF)
Changes in Solar Radiation Variability: Percentage changes in the annual coefficient of variation of solar radiation between 1984 and 2007: grid cells without a statistically significant change are shown in gray and the Indian Ocean sector is blacked out because data were not available for much of this period.