News

My new invited commentary, Seeing dew deposition from satellites: leveraging microwave remote sensing for the study of water dynamics in and on plants, was published a few weeks ago in New Phytologist and is accessible HERE. The commentary is a response to the article by Xu et al. published in the same issue that looked at the effect of leaf wetness on microwave remote sensing by combining satellite data and a plant hydrodynamics model.

DOI: 10.1111/nph.17418

My new preprint entitled Improving representation of tropical wetland methane emissions with CYGNSS inundation maps was recently published in the Earth and Space Science Open Archive. The article is currently under review in Global Biogeochemical Cycles. For this work, I generated monthly maps of two tropical wetlands, the Pantanal in Brazil and the Sudd in South Sudan, and used this maps within the wetland methane emissions model WetCHARTs to understand the seasonal and interannual dynamics of wetland methane emissions. We found the new maps drastically improve the results from WetCHARTs when compared to satellite data or flux-based measurement. 

Link to the preprint: https://www.essoar.org/doi/10.1002/essoar.10504845.1

Abstract

Wetlands are the single largest source of methane to the atmosphere and their emissions are expected to respond to a changing climate. Inaccuracy and uncertainty in inundation extent drives differences in modeled wetland emissions and impacts representation of wetland emissions on inter-annual and seasonal time frames. Existing wetland maps are based on optical or NIR satellite data obscured by clouds and vegetation, often leading to underestimates in wetlands extent, especially in the Tropics. Here, we present new inundation maps based on the CYGNSS satellite constellation, operating in L-band that is not impacted by clouds or vegetation, providing reliable observations through canopy and cloudy periods. We map the temporal and spatial dynamics of the Pantanal and Sudd wetlands, two of the largest wetlands in the world, using CYGNSS data and a computer vision algorithm. We link these inundation maps to methane fluxes via WetCHARTs, a global wetland methane emissions model ensemble. We contrast CYGNSS-modeled methane emissions with WetCHARTs standard runs that use monthly rainfall data from ERA5, as well as the commonly used SWAMPS wetland maps. We find that the CYGNSS-based inundation maps modify the methane emissions in multiple ways. The seasonality of inundation and methane emissions is shifted by two months because of the lag in wetland recharge following peak rainfall.  Both inundation and methane emissions also respond non-linearly to wet-season precipitation totals, leading to large interannual variability in emissions. Finally,  the annual magnitude of emissions is found to be greater than previously estimated.

My article on monitoring reforestation efforts in Chinese drylands using microwave remote sensing from QuikSCAT and solar-induced chlorophyll fluorescence from GOME-2 has been published in One Earth. This work was done in collaboration with an interdisciplinary team: Gretchen Keppel-Aleks at the University of Michigan, Feng Wang from the Chinese Academy of Sciences, Steve Frolking from the University of New Hampshire, and Denise Mauzerall from Princeton University. We find that both remote sensing data correlates strongly with official planting data from the Chinese government. We also compare different planting techniques: the "traditional" manual planting and the more recent trend of closing pastures to let vegetation recolonize the area naturally. Both methods appear to be successful. You can read the full article HERE (open access).

Title

Satellite Monitoring of Natural Reforestation Efforts in China's Drylands

Abstract

Desertification in Northern China degrades air quality in China's eastern cities by causing frequent dust storms. To stop desert expansion, China's government initiated the Three-North Shelterbelt Program, a large-scale reforestation project. Many issues with the project have been raised, from the choice of ill-adapted species to planting methods. Recently, the government implemented “natural reforestation” - closing former pastures to let vegetation regrow naturally. Unfortunately, it has been difficult to estimate the large-scale success of natural reforestation because measuring arid ecosystem productivity is a challenge for optical remote sensing. Here, we use satellite data to monitor vegetation water content and photosynthetic activity, thereby quantifying changes in vegetation biomass and productivity in Northern China. These satellite data corroborate official reforestation data. Our results show that vegetation activity is strongly correlated with both natural and traditional active reforestation, indicating opportunities for new natural reforestation techniques combined with satellite monitoring in other semi-arid regions.

Science for Society

Climate change has been driving desertification in many parts of the world, from the southwestern United States to Sub-Saharan Africa. Deserts often encroach over arable land, reducing income for farmers and causing dust storms with large health impacts on the local population and global climate effects. Reforestation efforts protect the sand from being lifted by the wind, but these projects often fail because these areas are very dry, and the plants do not survive. Understanding how well different strategies work in this harsh environment is of global interest because many countries use reforestation as an official offset for their CO2 emissions. However, because of the mismatch between planted and surviving trees, the accounted carbon sequestered in these forests is overestimated. In this study, we use a new type of satellite data looking at vegetation water and photosynthesis to compare the success of different reforestation methods, using China's Three-North Shelterbelt Program as a case study.

DOI: 10.1016/j.oneear.2019.12.015

As the chair of the early-career subcommittee for the AGU Ecohydrology Technical Committee, I would like to advertise three events related to the upcoming AGU Fall Meeting (1 funding opportunity, two on-site events). Please feel free to forward to colleagues, students, and anyone else who may be interested!

1. Tiny Grants

The Ecohydrology Technical Committee with the support of the Hydrology Section of the American Geophysical Union is happy to announce a new “Tiny Grant” program to support early-career scientists attending the AGU Fall Meeting 2019. The necessity to financially support early-career scientists attending the Fall Meeting was one of the main takeaways from the Ecohydrology early-career subcommittee survey. The survey gathered answers from close to 50 ecohydrologists to understand how the Ecohydrology Technical Committee could improve the Fall Meeting experience of early-career scientists.

The $500 award budget will be equally split between 2 to 5 recipients (depending on the number and the quality of the applications) to help provide financial support with costs associated with attending the meeting. Applicants must be graduate students or early-career scientists (less than 10 years since PhD graduation) working in the field of ecohydrology to apply. 

To apply, please fill out the online form here.  Application Deadline: 4 November 2019.

2. Bar Meet-up 

Are you a self-identified ecohydrologist attending the AGU Fall Meeting this year? Come meet and chat with fellow ecohydrologists at the Ecohydro Happy Hour on Wednesday, December 11th at 6:30pm in the Sir Francis Drake Hotel’s lobby bar. The address is 450 Powell Street, one block north of Union Square. It will be a chance to catch up with old and new friends, chat about science and careers, and hear more about the work the Ecohydrology Technical Committee has been doing. Join us and please spread the word to anyone else who might be interested.

3. Informal Ecohydrology Lunches

We’re organizing no-host lunches to network and connect ecohydrologists, especially first-time AGU attendees. You can participate in one of two ways: volunteer as a lunch leader (we specifically need one for Thursday) or simply join as an attendee. 

 For lunch leaders:

1. Once you know your presentation schedule, we ask that 1-2 ecohydro TC members volunteer as lunch leaders: Pick a day, location for lunch, and then coordinate the meet-up time and location with other attendees. You should decide whether to meet at the lunch spot or at Moscone Center to walk together to the venue.

2. Please list your name, email, and some keywords or phrases about your work in the sign-up sheet.

3. Send an email to your lunch-mates about 1 week before AGU (by Dec. 2) to introduce yourself and share details about your meet-up. If you feel comfortable sharing your phone number, consider emailing attendees your phone contact to ease coordination.

For lunch attendees:

1. Once you know your presentation schedule, sign-up for a lunch slot. If you happen to know many of the people already signed up for one day, consider stretching yourself to meet new folks and sign-up for a different day.

2. Be in touch with your lunch lead and be on time when the lunch location/time is determined. Attendees are responsible for purchasing their own food and drink.

Here is the sign-up sheet to help coordinate meet-ups. The spreadsheet is a public link, so we do not recommend posting phone numbers. 

See you all in San Francisco!

Dr. Cynthia Gerlein-Safdi (U. Michigan), Dr. Khandker Ishtiaq (Florida International University), Natasha Krell (U.C. Santa Barbara) and Aurora Kagawa-Viviani (U.H.-Manoa).

My article on monitoring reforestation efforts in Chinese drylands using microwave remote sensing from QuikSCAT and solar-induced chlorophyll fluorescence from GOME-2 is available to read as a preprint on The Cell's website. This work was done in collaboration with Gretchen Keppel-Aleks at the University of Michigan, Feng Wang from the Chinese Academy of Sciences, Steve Frolking from the University of New Hampshire, and Denise Mauzerall from Princeton University. We find that both remote sensing data correlates strongly with official planting data from the Chinese government. We also compare different planting techniques: the "traditional" manual planting and the more recent trend of closing pastures to let vegetation recolonize the area naturally. Both methods appear to be successful. Learn more by reading the full preprint HERE.

The paper is currently in revision and we are hoping that the final version will be available shortly! UPDATE: see the final paper out now in One Earth

Title

Satellite Monitoring of Natural Reforestation Efforts in China's Drylands

Abstract

Desertification in Northern China degrades air quality in China's eastern cities by causing frequent dust storms. To stop desert expansion, China's government initiated the Three-North Shelterbelt Program, a large-scale reforestation project. Many issues with the project have been raised, from the choice of ill-adapted species to planting methods. Recently, the government implemented "natural reforestation'' - closing former pastures to let vegetation regrow naturally. Unfortunately, it has been difficult to estimate the large-scale success of natural reforestation because measuring arid ecosystem productivity is a challenge for optical remote sensing. Here, we use satellite data to monitor vegetation water content and photosynthetic activity, thereby quantifying changes in vegetation biomass and productivity in Northern China. These satellite data corroborate official reforestation data. Our results show that vegetation activity is strongly correlated with both natural and traditional active reforestation, indicating opportunities for new natural reforestation techniques combined with satellite monitoring in other semi-arid regions.

Over the past few months, I have been busy with conferences and talks, starting with a talk at the AGU Fall Meeting in Washington DC on my work using CYGNSS to look at rainfall interception. In January, I visited Caltech for the CYGNSS Science Team meeting. I went on to give a talk for the Environmental Engineering and Water Resources Seminar Series in the CEE department here at the University of Michigan. Finally, I gave a guest lecture for the Environmental Science Seminar at Iowa State University, hosted by Pr. Brian Hornbuckle.

 Recently, the Green Life Sciences Symposium I presented at in September 2018 uploaded all the presentations to Youtube. You can see my talk below, or follow this link to see the rest of the presentations.

Inspired by the AGU Centennial Celebration and how ecohydrology has grown in the last 100 years, the AGU Ecohydrology Technical Committee I am part of has been adding a "leaf" to the ecohydrology tree week-by-week by introducing a new ecohydrologist every week and how their experiences helped shape the perspective they contribute.

I was featured this week and answered a few questions on my vision of the field. Head over to the AGU Ecohydrology website to check it out!

Our new article, "Dew deposition suppresses transpiration and carbon uptake in leaves" was just published in Agricultural and Forest Meteorology. The work was a collaboration with Kelly Caylor, Sally Thompson's lab at UC Berkeley, and Tony Rockwell at Harvard University. For this work, we built a leaf energy balance model to test the effects of dew and fog on the leaf water, carbon, and energy balances. We compared our model to data from UC Berkeley's Blue Oak Ranch Reserve in CA. See the abstract below for a quick overview of the study and results or head to the A&FM website to read the full paper.

Abstract

Dew deposition occurs in ecosystems worldwide, even in the driest deserts and in times of drought. Although some species absorb dew water directly via foliar uptake, a ubiquitous effect of dew on plant water balance is the interference of dew droplets with the leaf energy balance, which increases leaf albedo and emissivity and decreases leaf temperature through dew evaporation. Dew deposition frequency and amount are expected to be affected by changing environmental conditions, with unknown consequences for plant water stress and ecosystem carbon, water and energy fluxes. Here we present a simple leaf energy balance that characterizes the effect of deposition and the evaporation of dew on leaf energy balance, transpiration, and carbon uptake. The model is driven by five common meteorological variables and shows very good agreement with leaf wetness sensor data from the Blue Oak Ranch Reserve in California. We explore the tradeoffs between energy, water, and carbon balances for leaves of different sizes across a range of relative humidity, wind speed, and air temperature conditions. Our results show significant water savings from transpiration suppression up to 25% for leaf characteristic lengths of 50 cm. CO2 assimilation is decreased by up to 12% by the presence of dew, except for bigger leaves in windspeed conditions below 1 m s−1 when an increase in assimilation is expected.

This year, the AGU Fall Meeting moved from its traditional location in San Francisco to New Orleans. As usual, the meeting was a wonderful occasion to catch up with former classmates and colleagues, and hear about all the new science!

This year, I was the co-chair for the CYGNSS session A11F, Early On-Orbit Results of the Cyclone Global Navigation Satellite System, together with Chris Ruf. The poster session was a great way for all the people using and working on CYGNSS to chat about their respective results.

In addition, I gave an oral presentation entitled Effects of dew deposition on transpiration and carbon uptake in leaves that presented the results of a collaboration with Sally Thompson's lab at UC Berkeley.

Finally, I had the opportunity to attend the Ecohydrology Technical Committee and to help out with the Hydrology Business Meeting. Both events were great opportunities to meet new people in my field, and I'm hoping to get more and more involved with the hydrology community at AGU in the future.

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.

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!

youtu.be/4JBHCk2zmXo 

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.

See the article.

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.

[youtube https://www.youtube.com/watch?v=pRyOwbHZgfs&w=560&h=315]

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.

I just receive the great news that I  have been awarded one of the Mary and Randall Hack ‘69 Graduate Awards 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.

I am planning on using the award to focus my summer research on my project using QuikSCAT data to map dew formation over tropical forests.

You can read more about my project in the official announcement HERE.

Last week, I went out to California to initiate a new collaboration with Pr. Sally Thompson at UC Berkeley. Pr. Thompson has been collecting leaf wetness data at multiple sites across California, and I will be using her dataset together with my leaf energy balance model to estimate the reduction in transpiration associated with dew and fog formation. I got the chance to visit one of the field sites, the Blue Oak Ranch Reserve, located up in the hills above San Jose. 

I will be presenting a poster at the AGU Fall Meeting on Wednesday, December 16th between 1:40 and 6:00 PM in Moscone South. The poster, Foliar Shielding: How Non-Meteoric Water Deposition Helps Leaves Survive Drought by Reducing Incoming Energy (A33H-0273), will focus on the results of my first paper currently under review in PCE. Don't hesitate to stop by and say hi! If you can't make it, check out the E-Poster.

Elliot Chang, currently doing his senior thesis in the Caylor Lab, will be presenting the results of our paper together (RCMS, under review) in a poster titled Solid Phase Extraction Using C-18 Sorbents to Treat Organics in Water and Eliminate Spectral Interference in Isotope Ratio Infrared Spectroscopy (PP11B-2246). He will be presenting on Monday, December 14 from 08:00 AM to 12:20 PM. You can also see the E-Poster.

To see the rest of the presentations from the Caylor Lab, click HERE!

Today, I officially started my visit at Harvard University. For the next year, I will be sitting in Pr. N. Michele Holbrook's lab in the department of Organismic and Evolutionary Biology. I am excited to improve my plant physiology knowledge, and to get more lab experience. I will still be a full time student in the EcoHydrology Lab at Princeton University and will go to Princeton regularly throughout the year.

I gave the EEWR (Environmental Engineering and Water Resources) departmental seminar on Friday, March 27th 2015. My talk focused on the latest results from the lab experiments I conducted last summer and fall, looking at the impact of dew deposition on Colocasia esculenta's energy balance. Please contact me if you would like to hear more on the topic!

See the flyer and abstract here.

This summer I finally started my own research project. I spent the summer working in the Caylor Lab in Princeton, helped by Craig Sinkler, a student from Rider University who did an internship in our lab this summer. We planted six large bulbs of Colocasia esculenta that we watered until the plants reached maturity. After about 4 weeks of growth, we stopped watering the plants. Every two days, we sprayed the leaves of half of the plants with isotopically spiked water, while the other half of the plants did not get any water. We collected leaves from each treatment and looked at the spatial distribution of water isotopes in the leaf using the Picarro Induction Module. I then built maps of the leaf isotopes for leaves collected at different times within a 4 week long treatment. 

In order to help us interpret the evolution of the spatial patterns of the leaf isotopes, I also started running a water potential experiment in which I leave a leaf dry out under a heat lamp over a period of 10 hours and collect samples every half hour that I run on the WP4C to measure leaf water potential. I have been running the same experiment but spraying the leaf with ultra pure water every hour to look at whether foliar uptake is actually happening in Colocasia esculenta and how it improves water potential. Preliminary results show that foliar uptake is indeed happening!

I am happy to announce that I was awarded a PEI-STEP Fellowship! I will be working in collaboration with Prof. Mauzerall on the influence of policy incentives on the deforestation rate of tropical forests. I will look at decisions taken from the international to the municipal level across three different countries: Brazil, RDC and Indonesia. I will use the Global Forest Change monitor to study land use change and associate decrease in deforestation rates with efficient policy incentives.

The Fellowhsip will cover one year of stipend. To complete the STEP Certificate, I will also have to complete three courses in environmental policy. I am really thankful to PEI for such a great opportunity and I'm looking forward to starting working on my project!

See the PEI announcement HERE.

I just got the news today that I passed my general examination! I am now officially a PhD Candidate!

My Generals' proposal is focusing on the importance of non-meteoric atmospheric water for the hydraulic functions of plants in tropical forests.

I just got accepted to the SPATIAL 2014 Summer course at the University of Utah. This course is the second leg of the Iso-Camp Summer school I attended in June 2013. SPATIAL is focused on regional and continental research involving stable isotopes. In addition, I also got awarded a $2300 NSF scholarship to cover the tuition of the course.

I am very excited and I am really looking forward to being back in Salt Lake City to hang out with the isotopeteers!

In the fall of 2013, I help teach the freshman seminar ``Global Environmental Change: Science Technology and Policy". As part of my teaching, I organized a field trip to Costa Rica, where we visited a geothermal power plant, a wind farm, a field of solar panels, a sustainable coffee plantation, a research station in the cloud forest. Within a week, I saw  the students' perspective on Global Change evolve more than it had in the 6 weeks of classes prior to the trip, proving once again the impact of teaching outside of the classroom.

I was up in NYC on Thursday, April 18th for the NYC Girls Computer Science and Engineering Conference. I presented my research and helped teach an introductory programming class to high school girls. The conference, hosted by NYU in collaboration with Princeton University and Google, was aimed at stimulating girls' interest in computer sciences and engineering. Over 200 high schoolers from all over NYC attended the conference.