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.
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.
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).
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.
Stephanie Debats just got awarded the Mary and Randall Hack ‘69 Graduate Award by the Princeton Environmental Institute. The Mary and Randall Hack ’69 Award provides research funding to support Princeton University graduate students pursuing innovative research on water and water-related topics with implications for the environment. Stephanie is planning on using the award for workshops and conferences critical for strengthening her skills in remote sensing, statistical machine learning, and computer vision. It will also support her Zambian farmer text messaging pilot project and collection of validation data sets for her statistical model.
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.
As part of the PulseLab project, Adam Wolf, Lyndon Estes, Ben Siegfried and Matteo Kruijssen (PEI Grand Challenge intern working with Lyndon and Darren Drewry from NASA JPL for the summer, as part of a SURP grant) went out in California in June to install sensors in agricultural fields with the goal of realtime monitoring of crop growth and microclimate in control, water limited, and N-limited corn fields. Since crop growth forecasts are largely driven by remote sensing, these observations help to improve space-borne satellite retrievals for modeling, but also provide important constraints to the local microclimate, including temperature and soil moisture, which are critical to improving the predictions of climate change impacts on crop productivity. Check out the pictures of their fieldtrip below!
End of July, Adam and Ben went out again, to New Mexico this time. You can see the pictures of the pods installation HERE.
The NASA grant was awarded to Lyndon under the New Investigator Program in Earth Science for his proposal entitled “Integrating crowdsourcing, in situ sensing, and spaceborne observation to understand the sustainability of smallholder agriculture in African wet savannas”. This project will use a combination of remote sensing, field observations by PULSE lab sensors, machine learning (led by Stephanie Debats), and crowdsourcing to detect trends in the area and productivity of Zambian maize farms since 2000. The aim is to assess 1) whether yield increases are correlated with cropland expansion or contraction, 2) whether yield increases precede cropland changes, and 3) whether yield gains correspond to increased climate sensitivity. This research will provide insight into the socioeconomic and ecological sustainability of agricultural expansion in a region of increasing climatic variability and rapid growth.