On September 7th 2017, I defended my PhD. My thesis is entitled “Investigating dew deposition on leaves: effects on leaf water content, CO2, and remote sensing characterization” and is available on ProQuest.
My readers were Eric Wood and my advisor Kelly Caylor. Examiners were (from left to right): Kelly Caylor, Amilcare Porporato, and Steve Frolking (University of New Hampshire).
It has been a long and exciting ride at Princeton University. On September 1st, I started a position as a Junior Fellow with the Michigan Society of Fellows. During my 3-year long tenure as a Junior Fellow, I will be working in the Department of Climate and Space Sciences and Engineering at the University of Michigan, focusing on using the new CYGNSS data over land.
After thinking a lot about pre-print and how they fit in the world of plant research, I have decided to give it a try! My first pre-print entitled “Dew-induced transpiration suppression impacts the water and isotope balances of Colocasia leaves“ is now available on the bioRxiv: see the article!
The paper examines the effects of dew on transpiration suppression in Colocasia esculenta leaves using stable isotopes of water to track changes in the water status of the leaves. The article has been submitted to a peer-reviewed journal.
Abstract: Foliar uptake of water from the surface of leaves is common when rainfall is scarce and non-meteoric water such as dew or fog is more abundant. However, many species in more mesic environments have hydrophobic leaves that do not allow the plant to uptake water. Unlike foliar uptake, all species can benefit from dew- or fog-induced transpiration suppression, but despite its ubiquity, transpiration suppression has so far never been quantified. Here, we investigate the effect of dew-induced transpiration suppression on the water balance and the isotopic composition of leaves via a series of experiments. Characteristically hydrophobic leaves of a tropical plant, Colocasia esculenta, are misted with isotopically enriched water to reproduce dew deposition. We measure leaf water isotopes and water potential and find that misted leaves exhibit a higher water potential (p < 0.05) and a more depleted water isotopic composition than misted leaves (p < 0.001), suggesting a ∼30% decrease in transpiration rate (p < 0.001) compared to control leaves. We propose three possible mechanisms governing the interaction of water droplets with leaf energy balance. Comparing previous studies on foliar uptake to our results, we conclude that transpiration suppression has an effect of similar amplitude, yet opposite sign to foliar uptake on leaf water isotopes.
My new paper is finally available online on Plant, Cell & Environment. For this paper, entitled “Leaf water 18O and 2H maps show directional enrichment discrepancy in Colocasia esculenta“, we looked at spatial patterns of water isotopes in Colocasia esculenta leaves. See the abstract below for a quick overview of the study and results or head to the PCE website to read the full paper.
Spatial patterns of leaf water isotopes are challenging to predict because of the intricate link between vein and lamina water. Many models have attempted to predict these patterns, but to date most have focused on monocots with parallel veins. These provide a simple system to study, but do not represent the majority of plant species. Here, a new protocol is developed using a Picarro induction module coupled to a cavity ringdown spectrometer to obtain maps of the leaf water isotopes (18O and 2H). The technique is applied to Colocasia esculenta leaves. The results are compared to isotope ratio mass spectrometry. In C. esculenta, a large enrichment in the radial direction is observed, but not in the longitudinal direction. The string-of-lakes model fails to predict the observed patterns, while the Farquhar-Gan model is more successful, especially when enrichment is accounted for along the radial direction. Our results show that reticulate veined leaves experience a larger enrichment along the axis of the secondary veins than along the midrib. We hypothesize that this is due to the lower major/minor vein ratio that leads to longer pathways between major veins and sites of evaporation.
This weekend, I took part in the “Thesis in 180s” competition at MIT during which French speaking PhD students from all background presented their thesis in 180 seconds (3 minutes) to a non-specialized audience. This competition started in French-speaking countries in 2012, and this year was the first time that the competition was hosted is the US. The event was organized by the French Consulate in Boston and the French @MIT Club.
Explaining one’s research project in such a short amount time requires a lot of preparation, but it was a very fun challenge! During my presentation, I introduced the concepts of dew, foliar uptake, transpiration suppression, cavitation, and water use efficiency, all in only 180s! I was awarded 3rd place and received a $500 prize from Thales, who sponsored the event. The winner, Arthur Michaut, will defend the US in the international final in September in Liège (Belgium).
If you understand French, make sure to watch the video of my presentation!
Two weeks ago, I had the pleasure to attend the 16th Electromagnetic and Light Scattering Conference, held at the University of Maryland in College Park. This yearly conference gathers over 100 participants from around the world to discuss different aspects of scattering by small particles, from modeling to lab work and atmospheric and astrophysical observations. I gave a talk on modeling scattering from a dew-wetted leaf. You can see the abstract HERE and the program HERE.
Two new articles I co-authored recently came out.
The influence of memory, sample size effects, and filter paper material on online laser-based plant and soil water isotope measurements, published in Rapid Communications in Mass Spectrometry looks at the performance of the Picarro Induction Module for rapid, in-situ analysis of water isotopes in plant and soil samples. The lead author, Jiangpeng Cui, is a PhD student from the Institute of Tibetan Plateau Research at the Chinese Academy of Sciences. Jiangpeng approached me at the AGU Fall Meeting 2014 where I presented work using the induction module, and we have collaborated ever since.
See the article.
Global sources, emissions, transport and deposition of dust
and sand and their effects on the climate and environment:
a review, published in Frontiers of Environmental Science & Engineering is a review paper on some of the positive aspects of dust and sand storms. Lead author Feng Wang was a visiting professor in the Caylor Lab at Princeton for almost a year back in 2014 and has kept in touch with the lab since then.
I recently took part in a broad study on gender biases faced by women in geoscience. The work was led by the brilliant Julia Rosen and was just published on AGU’s EOS webpage today.
Julia interviewed women in academia, from PhD students to professors, and compiled stories and research articles on the biases encountered by women in geoscience on a daily basis. One of the key conclusions of the article is that women still face hurdles in the geosciences, but that these hurdles are harder to spot than they once were, making them more difficult to eliminate.
Head to their website to read the full story!
Photo credit: Natasha Krell
I will be presenting a poster at the AGU 2016 Fall Meeting on Wednesday, December 14th between 1:40 and 6:00 PM in Moscone South. The poster, Characterization of canopy dew formation in tropical forests using active microwave remote sensing (B33F-0681), will focus on my project modeling scattering of microwaves from dew-wetted leaves. Don’t hesitate to stop by and say hi! If you can’t make it, check out the E-Poster HERE!
On Tuesday, December 13th at 4:05PM, I will be giving a 5min long Pop-Up talk presenting our upcoming review paper on tropical ecohydrology. The session will be held in Moscone West, room 2001A. More details on the Water Sciences Pop-Up session can be found HERE.
EDIT: The video of my Pop-Up talk is now available online! Watch it below or directly on Youtube.
The AGU Tumblr page just published my profile in their early career scientists series. In this series, PhD students, post-docs, and early career faculty get to answer a few fun questions related to their research and their academic life.
Check out their page to read my interview!
I was recently awarded a 1-year award from the NASA Jet Propulsion Lab’s Strategic University Research Partnership program! These grants provide up to $100,000 for cutting edge earth science research conducted by JPL scientists and their chosen collaborators at one of JPL’s 12 partnering universities.
For this project, I will be collaborating with David Thompson from JPL. We plan to combine QuikSCAT active microwave remote sensing data with the AVIRIS Next Generation data over California to advance remote sensing of tree canopy water, improving our ability to map ecophysiology, water stress, drought response, and fire risk.
Photo credit: NASA Landsat (showing the Selenge River delta)