Skip to content Skip to navigation


January 31, 2021

This paper, led by PhD student Nathan Dadap, uses Planet data to map, for the first time, drainage canals in the tropical peatlands of Southeast Asia, a hotspot of CO2 emissions. These canals lower the water table and cause large CO2 emissions associated with the resulting peat decompositon. We further showed that, contrary to common assuptions in estimating carbon emissions, there is significant diversity in drainage density within land use classes. These maps may therefore be useful in building better emissions estimates for this hotspot region. The paper is in review at AGU Advances, but can now be read as a preprint on the Earth and Space Science Open Archive, here.

January 2, 2021

The paper describes some fieldwork we completed as part of SMAPVEX19-21, to demonstrate explicitly (and without a difference in spatial scales) that L-band VOD is sensitive to xylem and leaf water potential variations. The paper is still undergoing typesetting, but the original version can be found here.

January 1, 2021

In the paper, we present an approach to estimate ecosystem-scale plant hydraulic parameters (e.g. maximum xylem conductance, P50, stomatal parameters) using model-data fusion combining a plant hydraulic model and assimilation of LPDR vegetation optical depth and ALEXI evapotranspiration. Using the new trait maps, we further show that one can derive 'hydraulic functional types' - alternative clusters to PFTs. When the hydraulic functional type mean is used instead of a PFT-wide mean (as in typical land surface models), ET forward model estimates improve even for a relatively small number of HFTs. You can read (or comment on!) the full paper here.

January 1, 2021

Carbon cycle models have become increasingly complex over time, as more and more processes are represented. But as models get more complex, the risk that they are mis-parametrized becomes increasingly large. We used CARDAMOM with a variety of different model structures, data assimilation types and errors, and more to systematically assess whether increasing model complexity always improves forecast performance (including accounting for prediction uncertainty). In fact, intermediate complexity models often perform better than more complex models. Increased complexity only improves forecast skill if net carbon flux data is available to sufficiently constrain the parameters. This suggests terrestrial biosphere models should focus more on constraining parameter uncertainties rather than simply increasing the number of processes represented. A list of other specific recommendations is also included in the paper, which can be read (or commented on!) here.

December 30, 2020

Greg leaves the group to go work in Anna Trugman's group at UCSB. We're grateful for Greg's time in the group, and that he'll still be close by!

December 10, 2020

Check out the virtual AGU presentations from the RSEG members!
B081-0018: Olivia's poster (with Yanlan) on spatial patterns in maximum stomatal conductance, and simple PFT-alternative predictive models
B089-06: Yanlan's talk (with Natan) on estimating global plant hydraulic traits maps using VOD and designing 'hydraulic functional types'
B034-0007: Krishna's poster on using SAR-derived live fuel moisture to understand the relationship between plant hydraulic traits and fire ignition risk
EP042-06: Nathan's talk on characterizing the factors driving soil moisture drying in tropical peatlands using SMAP
B117-06: Caroline's talk (with Greg) on the relationship between carbon cycle model forecast performance and model complexity
B110-0001: Greg's poster (with Nathan and Caroline) using 100-year CARDAMOM simulations to show the surprisingly tight and large
H093-03: Matt's poster on ECOSTRESS and radiation in the Upper Colorado River, his undergraduate work
B090-06: Alex's talk (with Natan, Krishna and Yanlan) on using microwave remote sensing for ecosystem-scale plant drought response studies
H072-01: Alex's talk (with Nathan) on mapping drainage canals in Southeast Asian peatlands and their relationship with carbon fluxes

October 31, 2020

The paper explores how mortality and growth vary between initial and subsequent extreme droughts in a given location by using both site-scale and VOD-based analyses. You can read it here

October 25, 2020

Natan and Alex contributed to this paper as part of the SMAPVEX19 validation campaign. The paper is available here

October 25, 2020

The paper is based on measurements we took at Harvard Forest as part of SMAP's SMAPVEX19 campaign and compares tower-based L-band VOD with leaf and stem water potentials and dielectric constants. You can find it here

September 30, 2020

Matthew Worden joins the group as a new PhD student. Welcome, Matt!

July 20, 2020

I am currently looking for a new postdoctoral fellow! If you think our group and your background would be a good fit, please email Alex at with a CV and a description of your research interests. Multiple research topics are available. The postdoc will work to either: a) test newly derived datasets of canopy water content based on microwave radiometry and apply these to a variety of ecological questions or b) use a global carbon cycle data assimilation system constrained by remote sensing (CARDAMOM) to understand the spatial variability of carbon cycle parameters and their implication for global scale modelling. I am, of course, also open to discussing your research ideas. Applicants should have strong, demonstrated quantitative, computational, and communication skills. Experience working with ecological modeling, remote sensing data analysis, and/or microwave remote sensing is preferred. If that sounds like you, please reach out! Applications will be reviewed starting August 17th, until filled. Candidates from underrepresented groups are especially encouraged to apply

June 28, 2020

Yanlan Liu has accepted an offer as assistant professor at The Ohio State University! She will have a joint appointment in the School of Earth Sciences and in the School of Environment and Natural Resources and will begin her new position in fall 2021. We are excited that Yanlan can stay with us a little longer before then. Congratulations, Yanlan!!

June 20, 2020

Natan will be using the NASA FINESST fellowship to continue his work analyzing field campaign results relating VOD and water potential as well as mapping the response of VOD to water status and biomass changes to improve predictions of how vegetation will respond to future drought. Congratulations, Natan!

June 8, 2020

Yanlan's work uses a MCMC model-data fusion system to demonstrate that the commonly used empirical semi-empirical stomatal conductance models are overly sensitive to soil moisture and compensate by not being sufficiently sensitive to VPD relative to a more physiologically accurate approach that incorporates plant hydraulics. Under high VPD conditions, which are becoming more common as droughts become hotter, this leads models without plant hydraulic to underestimate ET reductions. The paper can be read here.

May 11, 2020

The approach combines Sentinel-1 with in situ LFMC measurements from the National Fuel Moisture Databse using a recurrent neural network. The use of Sentinel-1 SAR provides observations that are directly sensitive to vegetation moisture content, enabling improved accuracy relative to provious optical-data-only approaches. Maps are available at 15-day and 250 m resolution across the Western United States. You can play with the data interactively or download them here. The paper can be read here.

May 4, 2020

The paper is the first to derive data-driven ET estimates at basin scale by using an inverted water balance in combination with GRACE total water storage data. Precipitation inputs are determined by an optimal combination of precipitation products based on triple collocation. The paper discusses the surprising peak in ET during the smaller MAM wet season and the surprising lack of a trend in ET across the study period despite trends in climatic drivers. You can find it here.

May 1, 2020

The paper is co-authored by Susan Steele Dunne (TU Delft) and discusses the interpretation of, and possible value for, microwave remote sensing indices of vegetation water content for plant physiological and ecological applications. You can read it here.

March 22, 2020

Greg's recent paper shows that the CARDAMOM global carbon cycle model-data fusion system - which avoids parameter uncertainty by optimizing ecosystem parameters at each location but has a relatively simple structure to avoid equifinality - is able to capture NEP seasonal and interannual dynamics as well as TRENDY and CMIP5 can (to within their uncertainty). You can read it here.

February 20, 2020

A team including Krishna Rao and Natan Holtzman won first prize in the 'Best use of Google Cloud' and 'Most Energy-Efficient Sustainable Energy Hack' categories at the Stanford TreeHacks hackathon. Their project combined Krishna's recently created dataset of live fuel moisture content with data on fuel availability and urban proximity. More information is here. Congratulations, Krishna and Natan!

February 11, 2020

Alex has won an NSF CAREER grant from the Terrestrial Ecosystems program at NSF. The intellectual thrust of this five year grant will be to use CARDAMOM to study spatial patters in ecosystem parameters. That is, can more informative alternatives to plant functional types be derived across the globe from remote sensing data? The project will consider several ecosystem parameters, but particularly consider those related to heterotrophic respiration;

January 8, 2020

You can read this article here while it is in review. Greg and Alex contributed to this analysis. This paper uses CARDAMOM to demonstrate that lagged effects (e.g. changes in carbon pool sizes due to climate in previous years) have a greater effect on interannual variability in terrestrial carbon fluxes than direct responses to climate (which are much more commonly studied) do.

December 8, 2019

Here are our presentations:
1) Greg's Monday talk on CARDAMOM historical CO2 attribution: B11B-03
2) Nathan's Monday poster on mapping Southeast Asian peatland canals: H13K-1857
3) Yanlan's Monday talk on the interactions between plant hydraulics and VPD sensitivity: B12A-03
4) Caroline's Tuesday poster on extreme wet vs dry effects on NDVI: B21G-2407
5) Alex's Tuesday talk on Krishna's work predicting mortality with VOD: B22E-02
6) Alex's Thursday panel participation on the past and future of hydrological remote sensing: H41D-07
7) Krishna's talk on SAR-based high-resolution maps of live fuel moisture content: NH52A-03
8) Natan's poster on fieldwork showing the VOD - xylem water potential link: H51M-1657

December 1, 2019

As one of the associate editors for the Data-driven Climate Sciences section of Frontiers in Big Data, Alex is co-editing a research topic (virtual special issue) on 'Big Data for understanding tropical ecosystem services' together with Kyle Davis and Rafael Schmitt. We are interested in a wide variety of topics related to using data to better understand ecosystem service variability in the sparsely observed tropics. Papers should use at least two different types of data. More details on the special issue can be found here. Abstracts are due March 1st, 2020. 

October 14, 2019

To find out more about the workshop and see Alex's introductory talk about remote sensing of vegetation water content, click here. Yanlan and Natan were also among the 34 international attendees of the workshop. Thnak you to all the attendees for stimulating discussions!

September 18, 2019

The paper shows that, contrary to popular wisdom, vegetation density is sufficiently low (likely due to land use change) in many Insular Southeast Asian peatlands to allow for soil moisture retrieval using SMAP. SMAP soil moisture carries information about burned area with as much as 30 days lag time, and provides information not contained in commonly-used precipitation metrics, because soil moisture is also influenced by anthropogenic canal-building in the area. The paper can be found here. Stanford's press release about the article can be found here

September 1, 2019

Caroline presented her work about the effect of pluvials on ecosystem growth, and Greg presented on parameter uncertainty vs. structural uncertainty in CARDAMOM and other models, as well as an attribution of historical CO2 uptake due to climate change. 

July 31, 2019

Yanlan was previously a visiting student in summer of 2018. Welcome back, Yanlan!

July 29, 2019

Check out Nathan's and Krishna's talks, and the sessions on Vegetation Optical Depth!

July 8, 2019

We are working with Alexandre Roy (Université du Québec à Trois Rivières) and others to compare in situ L-band radiometry at Harvard Forest with various measurements of tree water status

June 17, 2019

Researchers from several groups spent a week discussing opportunities and results with the CARDAMOM model-data fusion system

June 11, 2019

Congratulations to Michael Burnett, Nathan Dadap and Krishna Rao for winning the Stanford School of Earth, Energy, and Environmental Sciences Certificate for Outstanding Achievement in Mentoring! 

June 5, 2019

The paper can be found here. It inverts the carbon balance using remote sensing data to constrain heterotrophic respiration.

April 14, 2019

The article was published in Remote Sensing of Environment and can be found here.

April 1, 2019

The paper explores how variations in leaf water potential due to factors such as leaf area index and vapor pressure deficit. Based on modelling and FLUXNET results, these factors can disrupt the relationship between apparent isohydricity and stomatal function across sites, but not within a site. You can find the paper here.

April 1, 2019

The article is a short Tansley Insight article and will become part of a virtual issue on remote sensing for plant science. You can find it (open access) here.

April 1, 2019

Please submit your abstract here. The conference will be in San Diego from August 26-29. This will be a great way to bring together an intimate gathering of a small group of people interested in carbon-climate feedbacks. Alex is on the program committee.

April 1, 2019

Greg will be speaking at 12:15 on Tuesday in Session BG2.48 on "Net Biosphere Exchange in the Recent Past: Uncertainty Comparison Between Model-data Fusion and Earth System Models"

January 8, 2019

We also presented a poster on Mike Burnett's work on ET in the Congo!

December 7, 2018

We'll be presenting: B33N-2872 (Krishna's work on fire fuel estimation with Sentinel-1), B51G-2013: (Greg's work comparing CARDAMOM, CMIP5, and TRENDY, oh my!), B53D-07 (Yanlan's work on plant hydraulic traits and ET), H44A-04 (Mike's work on using GRACE to estimate ET in the Congo basin), and B31J-2627 (Alex's work on global, data-driven heterotrophic respiration estimates)

December 3, 2018

Alex collaborated on this paper led by Andrew Feldman (MIT). It can be found here

September 24, 2018

In Mike's absence, Alex will present his work on estimating ET in the Congo River Basin via a water balance approach, and trends in the seasonality of ET in the basin.

September 23, 2018

Welcome, Natan and Caroline!

September 21, 2018

The flux tower based analysis is supplemented by a global analysis using VOD data that Alex led. The article can be found here.

June 27, 2018

Guadalupe is a rising senior at University of Texas - El Paso. She will be working with Nathan to characterize drainage patterns from anthropogenic canals in Insular Southeast Asia. Welcome, Guadalupe! 

June 14, 2018

Krishna Rao was awarded the 3-yr fellowship to support his PhD studies on using SAR for canopy mortality studies. Nathan Dadap will use the fellowship to support his PhD work on mapping soil moisture in Southeast Asian peatlands to better estimate fire and CO2 emissions. Congratulations, Nathan and Krishna!

June 4, 2018

SMAP MT-DCA data are now available via anonymous ftp. Instructions are on the datasets page.

June 1, 2018

The paper shows that the photosyntheis of taller Amazon forests is up to tree times less sensitive to precipitation than than of shorter forests. You can find it here

June 1, 2018

Yanlan is currently a PhD student at Duke. She'll be working on comparing ET model performance between approaches with and without plant hydraulics. Welcome, Yanlan!

March 13, 2018

The research will employ model-data fusion in a plant hydraulic model to improve hydrologic modelling

February 26, 2018

Welcome, Greg! Greg completed his PhD with Abby Swann at the University of Washington and will be working on understanding on the drought response of tropical carbon fluxes using CARDAMOM and other tools. 

January 19, 2018

Jackie Fortin (MS student in CEE) and Mike Burnett (senior in Earth Systems) join the group. Welcome!

December 7, 2017

Our talks and posters:
Nathan:  B13D-1794: Using Remotely Sensed Soil Moisture to Estimate Fire Risk in Tropical Peatlands

Mostafa: B24C-02: Interacting Effects of Leaf Water Potential and Biomass on Vegetation Optical Depth

Krishna: B31D-2009: Vegetation optical depth measured by microwave radiometry as an indicator of tree mortality

Alex: H14A-01: Stomatal and xylem regulation traits control the sensitivity of grassland productivity to aridity

September 22, 2017

WECANN is a new set of flux predictions based on solar-induced fluorescence based on neural networks. The paper can be found here

August 19, 2017

Congratulations and thanks for working with us, Chris. We'll miss you!

July 11, 2017

You can find it here. We are working to make the data publicly available, which should be soon. In the mean-time, please get in touch if you are interested!