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Welcome to the Princeton Ecohydrology Lab Website!

We've recently moved into a new site, so please let us know if you have any comments or - more likely - find any missing or dead links.

  • Dryland Ecohydrology

    Life in dryland savanna ecosystems is reliant on the spatial and temporal distribution of rainfall. In order to understand the impacts of changes in rainfall on woody vegetation patterns, our group has developed a set of modeling approaches that combine existing stochastic soil water balance models with a resource trade-off hypothesis pertaining to the organization of dryland vegetation communities. This framework has provided a mathematically tractable optimization problem which we have applied to southern African savannas, the Rio Salado basin in the US southwest, and a central Kenyan ecosystem.

  • Isotope Hydrology

    Understanding the coupled interactions between hydrology and ecology requires new measurements of environmental process at the landscape level. To this end we are beginning to use stable isotopes of hydrogen and oxygen as a tool for partitioning land surface water vapor fluxes into evaporation and transpiration components. We have recently constructed a new eddy flux tower in Likipia, Kenya which will be outfitted with a laser-based isotope analyzer from Los Gatos Research. This instrument allows continuous δ18O and δ2H measurements (1 Hz) in water vapor. It has great potential to answer both theoretical (e.g., kinetic fractionations in soil evaporation) and practical questions (e.g., the effect of vegetation structure on evaporation/transpiration partition).

New paper in GRL

We recently published a paper in Geophysical Research Letters that investigates the relationship between the ratio of transpiration over evapotranspiration (T/ET) and leaf area index (LAI). We developed a function relating T/ET to the growing stage relative to the timing of peak LAI. LAI and growing stage collectively explained 43% of the variations in the global T/ET data set, providing a new way to interpret and model global T/ET variability.

 

Summer at Mpala: plant physiological response to water stress

This summer, Hilary and her intern Kathy joined Drew and Keita in Laikipia, Kenya to collect data on plant physiological response to water stress. Hilary spent her summer recording photosynthesis and transpiration rates of Acacia mellifera along a water availability gradient at the Caylor Lab’s eddy covariance-isotope tower at Mpala Research Center. By looking at differences in carbon fixation rate, water loss and leaf hydraulic conductivity of the same species in various stages of water stress, it is possible to gauge the vulnerability of species to drought. Hilary hopes to pair this information with landscape-scale data from the flux tower to better understand and predict patterns in species distribution and abundance.

Summer in the lab: foliar uptake in Colocasia esculenta

This summer, Cynthia Gerlein and her intern Craig Sinkler spent the summer in the lab in Princeton to conduct an experiment looking at foliar uptake in Colocasia esculenta, a tropical specie. After a few weeks spent growing the plants, they subjected half of the plants to a drought treatment, while the other half received isotopically enriched water sprayed on the surface of the leaves every two days. The treatment experiment lasted 4 weeks during which they collected leaves from both treatments. They used the Picarro Induction Module and spatial interpolation techniques to obtain high resolution maps of the spatial distribution of the isotopes within the leaves. This experiment, coupled with water potential experiments and a rigorous validation of the induction module data against IRMS data, will be the basis for Cynthia’s effort to include foliar uptake into a leaf water balance model.

 

Drew Gower receives EPA STAR Fellowship

Drew Gower just received a Science to Achieve Results (STAR) Fellowship for Graduate Environmental Study awarded by the Environmental Protection Agency. The fellowship will cover his stipend and a portion of his tuition for two years, starting in September. Drew’s proposal focused on improving water resource management among irrigators in the Laikipia Region of Kenya.

Congratulations Drew!

New paper in ERL

We recently published a paper in Environmental Research Letters that examines changes in the water available for growing maize in sub-Saharan Africa between 1979 and 2010. We identified trends in rainfall, potential evapotranspiration (PET, which is the atmospheric demand for water), and the ratio of the two (also known as the aridity index), and also quantified the factors responsible for changing PET. You can follow the links below to several stories that provide a fuller overview of the findings.