Bio


Alexandra Konings leads the Remote Sensing Ecohydrology group, which studies interactions between the global carbon and water cycles. That is, her research studies how changes in hydrological conditions change ecosystems, and how this in turn feeds back to weather and climate. These interactions include studies of transpiration and root water uptake, photosynthesis, mortality, and fire processes, among others. To address these topics, the groups primarily uses the tools of model development and remote sensing (satellite) data, especially microwave remote sensing data of vegetation water content. Alex believes that a deep understanding of remote sensing techniques and how they can be used to create environmental datasets enables new opportunities for scientific insight and vice versa.

Academic Appointments


Administrative Appointments


  • Faculty Affiliate, Stanford Woods Institute for the Environment (2016 - Present)
  • Assistant Professor, Stanford Department of Earth System Science (2016 - Present)
  • Visiting Postdoc, NASA Jet Propulsion Laboratory (2016 - 2016)
  • Visiting Postdoc, Columbia University (2015 - 2016)
  • NASA Earth and Space Science Fellow, Massachusetts Institute of Technology (2012 - 2015)
  • NSF Graduate Research Fellow, Massachusetts Institute of Technology (2011 - 2011)
  • NSF Graduate Research Fellow, Duke University (2009 - 2011)

Honors & Awards


  • Global Environmental Change Early Career Award, AGU (2021)
  • Editor's Citation for Excellence in Refereeing (Geophysical Research Letters), AGU (2020)
  • CAREER, NSF (2020-2025)
  • New (Early Career) Investigator Award, NASA (2018-2021)
  • Group Achievement Award: AirMOSS Implementation Team, NASA (2016)
  • Best Doctoral Thesis Award, MIT Department of Civil and Environmental Engineering (2015-2016)
  • Earth and Space Science Fellowship, NASA (2012-2015)
  • Graduate Research Fellowship, National Science Foundation (2009-2012)
  • James B. Duke Fellowship, Duke University (2009-2011)

Boards, Advisory Committees, Professional Organizations


  • Member, Jasper Ridge Biological Preserve Faculty Advisory Committee (2017 - Present)
  • Member, AGU Hydrology Technical Committee on Remote Sensing (2016 - Present)
  • Member, IEEE Geoscience and Remote Sensing Society (2010 - Present)
  • Member, American Geophysical Union (2008 - Present)

Professional Education


  • Ph.D., Massachusetts Institute of Technology, Hydrology (2015)
  • M.S., Duke University, Environmental Science (2011)
  • S.B., Massachusetts Institute of Technology, Environmental Engineering Science (2009)

2021-22 Courses


Stanford Advisees


All Publications


  • Interannual Variations of Vegetation Optical Depth are Due to Both Water Stress and Biomass Changes GEOPHYSICAL RESEARCH LETTERS Konings, A. G., Holtzman, N. M., Rao, K., Xu, L., Saatchi, S. S. 2021; 48 (16)
  • Extreme wet events as important as extreme dry events in controlling spatial patterns of vegetation greenness anomalies ENVIRONMENTAL RESEARCH LETTERS Famiglietti, C. A., Michalak, A. M., Konings, A. G. 2021; 16 (7)
  • Global Coordination in Plant Physiological and Rooting Strategies in Response to Water Stress GLOBAL BIOGEOCHEMICAL CYCLES Liu, Y., Konings, A. G., Kennedy, D., Gentine, P. 2021; 35 (7)
  • Global ecosystem-scale plant hydraulic traits retrieved using model-data fusion HYDROLOGY AND EARTH SYSTEM SCIENCES Liu, Y., Holtzman, N. M., Konings, A. G. 2021; 25 (5): 2399-2417
  • Optimal model complexity for terrestrial carbon cycle prediction BIOGEOSCIENCES Famiglietti, C. A., Smallman, T., Levine, P. A., Flack-Prain, S., Quetin, G. R., Meyer, V., Parazoo, N. C., Stettz, S. G., Yang, Y., Bonal, D., Bloom, A., Williams, M., Konings, A. G. 2021; 18 (8): 2727-2754
  • Satellite Observations of the Tropical Terrestrial Carbon Balance and Interactions With the Water Cycle During the 21st Century REVIEWS OF GEOPHYSICS Worden, J., Saatchi, S., Keller, M., Bloom, A., Liu, J., Parazoo, N., Fisher, J. B., Bowman, K., Reager, J. T., Fahy, K., Schimel, D., Fu, R., Worden, S., Yin, Y., Gentine, P., Konings, A. G., Quetin, G. R., Williams, M., Worden, H., Shi, M., Barkhordarian, A. 2021; 59 (1)
  • Patterns of plant rehydration and growth following pulses of soil moisture availability BIOGEOSCIENCES Feldman, A. F., Gianotti, D., Konings, A. G., Gentine, P., Entekhabi, D. 2021; 18 (3): 831-847
  • Empirical estimates of regional carbon budgets imply reduced global soil heterotrophic respiration NATIONAL SCIENCE REVIEW Ciais, P., Yao, Y., Gasser, T., Baccini, A., Wang, Y., Lauerwald, R., Peng, S., Bastos, A., Li, W., Raymond, P. A., Canadell, J. G., Peters, G. P., Andres, R. J., Chang, J., Yue, C., Dolman, A., Haverd, V., Hartmann, J., Laruelle, G., Konings, A. G., King, A. W., Liu, Y., Luyssaert, S., Maignan, F., Patra, P. K., Peregon, A., Regnier, P., Pongratz, J., Poulter, B., Shvidenko, A., Valentini, R., Wang, R., Broquet, G., Yin, Y., Zscheischler, J., Guenet, B., Goll, D. S., Ballantyne, A., Yang, H., Qiu, C., Zhu, D. 2021; 8 (2)
  • L-band vegetation optical depth as an indicator of plant water potential in a temperate deciduous forest stand BIOGEOSCIENCES Holtzman, N. M., Anderegg, L. L., Kraatz, S., Mavrovic, A., Sonnentag, O., Pappas, C., Cosh, M. H., Langlois, A., Lakhankar, T., Tesser, D., Steiner, N., Colliander, A., Roy, A., Konings, A. G. 2021; 18 (2): 739-753
  • Global-scale assessment and inter-comparison of recently developed/reprocessed microwave satellite vegetation optical depth products REMOTE SENSING OF ENVIRONMENT Li, X., Wigneron, J., Frappart, F., Fan, L., Ciais, P., Fensholt, R., Entekhabi, D., Brandt, M., Konings, A. G., Liu, X., Wang, M., Al-Yaari, A., Moisy, C. 2021; 253
  • Leaf surface water, not plant water stress, drives diurnal variation in tropical forest canopy water content. The New phytologist Xu, X. n., Konings, A. G., Longo, M. n., Feldman, A. n., Xu, L. n., Saatchi, S. n., Wu, D. n., Wu, J. n., Moorcroft, P. n. 2021

    Abstract

    Variation in canopy water content (CWC) that can be detected from microwave remote sensing of vegetation optical depth (VOD) has been proposed as an important measure of vegetation water stress. However, the contribution of leaf surface water (LWs ), arising from dew formation and rainfall interception, to CWC is largely unknown, particularly in tropical forests and other high-humidity ecosystems. We compared the AMSR-E VOD and CWC predicted by a plant hydro-dynamics model at four tropical sites in Brazil spanning a rainfall gradient. We assessed how LWs influenced the relationship between VOD and CWC. The analysis indicates that while CWC is strongly correlated with VOD (R2 =0.62 across all sites), LWs accounts for 61-76% of the diurnal variation in CWC despite being less than 10% of CWC. Ignoring LWs weakens the near-linear relationship between CWC and VOD and reduces the consistency in diurnal variation. The contribution of LWs to CWC variation, however, decreases at longer, seasonal to interannual, time scales. Our results demonstrate that diurnal patterns of dew formation and rainfall interception can be an important driver of diurnal variation in CWC and VOD over tropical ecosystems and therefore should be accounted for when inferring plant diurnal water stress from VOD measurements.

    View details for DOI 10.1111/nph.17254

    View details for PubMedID 33539544

  • Lagged effects regulate the inter-annual variability of the tropical carbon balance BIOGEOSCIENCES Bloom, A., Bowman, K. W., Liu, J., Konings, A. G., Worden, J. R., Parazoo, N. C., Meyer, V., Reager, J. T., Worden, H. M., Jiang, Z., Quetin, G. R., Smallman, T., Exbrayat, J., Yin, Y., Saatchi, S. S., Williams, M., Schimel, D. S. 2020; 17 (24): 6393–6422
  • Interannual variability of ecosystem iso/anisohydry is regulated by environmental dryness. The New phytologist Wu, G., Guan, K., Li, Y., Novick, K. A., Feng, X., McDowell, N. G., Konings, A. G., Thompson, S. E., Kimball, J. S., De Kauwe, M. G., Ainsworth, E. A., Jiang, C. 2020

    Abstract

    Plants are characterized by the iso/anisohydry continuum depending on how they regulate leaf water potential (PsiL ). However, how iso/anisohydry changes over time in response to year-to-year variations in environmental dryness and how such responses vary across different regions remains poorly characterized. We investigated how dryness, represented by aridity index, affects the interannual variability of ecosystem iso/anisohydry at the regional scale, estimated using satellite microwave vegetation optical depth (VOD) observations. This ecosystem-level analysis was further complemented with published field observations of species-level PsiL . We found different behaviors in the directionality and sensitivity of isohydricity (sigma) with respect to the interannual variation of dryness in different ecosystems. These behaviors can largely be differentiated by the average dryness of the ecosystem itself: in mesic ecosystems, sigma decreases in drier years with a higher sensitivity to dryness; in xeric ecosystems, sigma increases in drier years with a lower sensitivity to dryness. These results were supported by the species-level synthesis. Our study suggests that how plants adjust their water use across years - as revealed by their interannual variability in isohydricity - depends on the dryness of plants' living environment. This finding advances our understanding of plant responses to drought at regional scales.

    View details for DOI 10.1111/nph.17040

    View details for PubMedID 33118166

  • SMAP Detects Soil Moisture Under Temperate Forest Canopies GEOPHYSICAL RESEARCH LETTERS Colliander, A., Cosh, M. H., Kelly, V. R., Kraatz, S., Bourgeau-Chavez, L., Siqueira, P., Roy, A., Konings, A. G., Holtzman, N., Misra, S., Entekhabi, D., O'Neill, P., Yueh, S. H. 2020; 47 (19)
  • Divergent forest sensitivity to repeated extreme droughts NATURE CLIMATE CHANGE Anderegg, W. L., Trugman, A. T., Badgley, G., Konings, A. G., Shaw, J. 2020
  • Data-driven estimates of evapotranspiration and its controls in the Congo Basin HYDROLOGY AND EARTH SYSTEM SCIENCES Burnett, M. W., Quetin, G. R., Konings, A. G. 2020; 24 (8): 4189–4211
  • SAR-enhanced mapping of live fuel moisture content REMOTE SENSING OF ENVIRONMENT Rao, K., Williams, A., Flefil, J., Konings, A. G. 2020; 245
  • Plant hydraulics accentuates the effect of atmospheric moisture stress on transpiration NATURE CLIMATE CHANGE Liu, Y., Kumar, M., Katul, G. G., Feng, X., Konings, A. G. 2020
  • Carbon Flux Variability from a Relatively Simple Ecosystem Model with Assimilated Data is Consistent with Terrestrial Biosphere Model Estimates Journal of Advances in Modeling Earth Systems Quetin, G. R., Bloom, A. A., Bowman, K. W., Konings, A. G. 2020; 12: e2019MS001889

    View details for DOI 10.1029/2019MS001889

  • SMAP VALIDATION EXPERIMENT 2019-2021 (SMAPVEX19-21): DETECTION OF SOIL MOISTURE UNDER FOREST CANOPY Colliander, A., Cosh, M. H., Misra, S., Bourgeau-Chavez, L., Kelly, V., Siqueira, P., Roy, A., Lakhankar, T., Kraatz, S., Konings, A. G., Holtzman, N., Kurum, M., Entekhabi, D. L., O'Neill, P., Yueh, S. H., IEEE IEEE. 2020: 3338-3340
  • Validation practices for satellite soil moisture retrievals: What are (the) errors? Remote Sensing of Environment Gruber, A., De Lannoy, G., Albergel, C., Al-Yaari, A., Brocca, L., Calvet, J., Colliander, A., Cosh, M., Crow, W., Dorigo, W., Draper, C., Hirshi, M., Kerr, Y., Konings, A., Lahoz, W., McColl, K., Montzka, C., Munoz-Sabater, J., Peng, J., Reichle, R., Richaume, P., Rudiger, C., Scanlon, T., Van der Schalie, R., Wigneron, J., et al 2020; 224: 111806
  • Satellite-based vegetation optical depth as an indicator of drought-driven tree mortality REMOTE SENSING OF ENVIRONMENT Rao, K., Anderegg, W. L., Sala, A., Martinez-Vilalta, J., Konings, A. G. 2019; 227: 125–36
  • Global satellite-driven estimates of heterotrophic respiration BIOGEOSCIENCES Konings, A. G., Bloom, A., Liu, J., Parazoo, N. C., Schimel, D. S., Bowman, K. W. 2019; 16 (11): 2269–84
  • Macro to Micro: Microwave Remote Sensing of Plant Water Content for Physiology and Ecology. The New phytologist Konings, A. G., Rao, K., Steele-Dunne, S. C. 2019

    Abstract

    Although primarily valued for their suitability for oceanographic applications and soil moisture estimation, microwave remote sensing observations are also sensitive to plant water content (Mw ). Since Mw depends on both plant water status and biomass, these observations have the potential to be useful for a range of plant drought response studies. In this paper, we introduce the principles behind microwave remote sensing observations to illustrate how they are sensitive to plant water content and discuss the relationship between landscape-scale Mw and common stand-scale metrics, including plant-scale relative water content, live fuel moisture content and leaf water potential. Lastly, we discuss how various sensor types can be leveraged for specific applications depending on the spatio-temporal resolution needed. This article is protected by copyright. All rights reserved.

    View details for PubMedID 30919449

  • Physics-Based Modeling of Active and Passive Microwave Covariations Over Vegetated Surfaces IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Jagdhuber, T., Konings, A. G., McColl, K. A., Alemohammad, S., Das, N., Montzka, C., Link, M., Akbar, R., Entekhabi, D. 2019; 57 (2): 788–802
  • Satellite soil moisture observatins predict burned area in Southeast Asian peatlands ENVIRONMENTAL RESEARCH LETTERS Dadap, N. C., Cobb, A. R., Hoyt, A. M., Harvey, C. F., Konings, A. G. 2019; 14

    View details for DOI 10.1088/1748-9326/ab3891

  • Simultaneous retrieval of global-scale vegetation optical depth, surface roughness, and soil moisture using X-band AMSR-E observations Remote Sensing of Environment Karthikeyan, L., Pan, M., Konings, A. G., Piles, M., Fernandez-Moran, R., Kumar, D. N., Wood, E. F. 2019; 234: 111473
  • Macro to micro: microwave remote sensing of plant water content for physiology and ecology NEW PHYTOLOGIST Konings, A. G., Rao, K., Steele-Dunne, S. C. 2019; 223: 1166-1172

    Abstract

    Although primarily valued for their suitability for oceanographic applications and soil moisture estimation, microwave remote sensing observations are also sensitive to plant water content (Mw ). Since Mw depends on both plant water status and biomass, these observations have the potential to be useful for a range of plant drought response studies. In this paper, we introduce the principles behind microwave remote sensing observations to illustrate how they are sensitive to plant water content and discuss the relationship between landscape-scale Mw and common stand-scale metrics, including plant-scale relative water content, live fuel moisture content and leaf water potential. Lastly, we discuss how various sensor types can be leveraged for specific applications depending on the spatio-temporal resolution needed.

    View details for DOI 10.1111/nph.15808

  • Beyond soil water potential: An expanded view on isohydricity including land–atmosphere interactions and phenology PLANT, CELL, AND ENVIRONMENT Novick, K. A., Konings, A. G., Gentine, P. 2019; 42: 1802-1815

    Abstract

    Over the past decade, the concept of iso/anisohydry, which describes the link between soil water potential (ΨS ), leaf water potential (ΨL ), and stomatal conductance (gS ), has soared in popularity. However, its utility has recently been questioned, and a surprising lack of coordination between the dynamics of ΨL  and gS across biomes has been reported. Here, we offer a more expanded view of the isohydricity concept that considers effects of vapor pressure deficit (VPD) and leaf area index (AL ) on the apparent sensitivities of ΨL and gs to drought. After validating the model with tree and ecosystem scale data, we find that within a site, isohydricity is a strong predictor of limitations to stomatal function, though variation in VPD and leaf area, among other factors, can challenge its diagnosis. Across sites, the theory predicts that the degree of isohydricity is a good predictor of the sensitivity of gs to declining soil water in the absence of confounding effects from other drivers. However, if VPD effects are significant, they alone are sufficient to decouple the dynamics of ΨL  and gs entirely. We conclude with a set of practical recommendations for future applications of the isohydricity framework within and across sites.

    View details for DOI 10.1111/pce.13517

  • Moisture pulse-reserve in the soil-plant continuum observed across biomes NATURE PLANTS Feldman, A. F., Gianotti, D., Konings, A. G., McColl, K. A., Akbar, R., Salvucci, G. D., Entekhabi, D. 2018; 4 (12): 1026–33

    Abstract

    The degree to which individual pulses of available water drive plant activity across diverse biomes and climates is not well understood. It has previously only been investigated in a few dryland locations. Here, plant water uptake following pulses of surface soil moisture, an indicator for the pulse-reserve hypothesis, is investigated across South America, Africa and Australia with satellite-based estimates of surface soil and canopy water content. Our findings show that this behaviour is widespread: occurring over half of the vegetated landscapes. We estimate spatially varying soil moisture thresholds at which plant water uptake ceases, noting dependence on soil texture and proximity to the wilting point. The soil type and biome-dependent soil moisture threshold and the plant soil water uptake patterns at the scale of Earth system models allow a unique opportunity to test and improve model parameterization of vegetation function under water limitation.

    View details for DOI 10.1038/s41477-018-0304-9

    View details for Web of Science ID 000454576600012

    View details for PubMedID 30518832

  • Global-scale assessment and combination of SMAP with ASCAT (active) and AMSR2 (passive) soil moisture products REMOTE SENSING OF ENVIRONMENT Kim, H., Parinussa, R., Konings, A. G., Wagner, W., Cosh, M. H., Lakshmi, V., Zohaib, M. 2018; 204: 260-275
  • Hydraulic diversity of forests regulates ecosystem resilience during drought NATURE Anderegg, W. R., Konings, A. G., Trugman, A. T., Yu, K., Bowling, D. R., Gabbitas, R., Karp, D. S., Pacala, S., Sperry, J. S., Sulman, B. N., Zenes, N. 2018; 561: 538-541

    Abstract

    Plants influence the atmosphere through fluxes of carbon, water and energy1, and can intensify drought through land-atmosphere feedback effects2-4. The diversity of plant functional traits in forests, especially physiological traits related to water (hydraulic) transport, may have a critical role in land-atmosphere feedback, particularly during drought. Here we combine 352 site-years of eddy covariance measurements from 40 forest sites, remote-sensing observations of plant water content and plant functional-trait data to test whether the diversity in plant traits affects the response of the ecosystem to drought. We find evidence that higher hydraulic diversity buffers variation in ecosystem flux during dry periods across temperate and boreal forests. Hydraulic traits were the predominant significant predictors of cross-site patterns in drought response. By contrast, standard leaf and wood traits, such as specific leaf area and wood density, had little explanatory power. Our results demonstrate that diversity in the hydraulic traits of trees mediates ecosystem resilience to drought and is likely to have an important role in future ecosystem-atmosphere feedback effects in a changing climate.

    View details for DOI 10.1038/s41586-018-0539-7

  • Tall Amazonian forests are less sensitive to precipitation variability NATURE GEOSCIENCE Giardina, F., Konings, A. G., Kennedy, D., Alemohammad, S., Oliviera, R. S., Uriarte, M., Gentine, P. 2018: 405-409
  • L-band vegetation optical depth seasonal metrics for crop yield assessment REMOTE SENSING OF ENVIRONMENT Chapparo, D., Piles, M., Vall-llossera, M., Camps, A., Konings, A. G., Entekhabi, D. 2018
  • Characterization of vegetation and soil scattering mechanisms across different biomes using P-band SAR polarimetry REMOTE SENSING OF ENVIRONMENT Alemohammad, S., Konings, A. G., Jagdhuber, T., Moghaddam, M., Entekhabi, D. 2018: 107-117
  • Active microwave observations of diurnal and seasonal variations of canopy water content across the humid African tropical forests GEOPHYSICAL RESEARCH LETTERS Konings, A. G., Yu, Y., Xu, L., Yang, Y., Schimel, D., Saatchi, S. 2017; 44: 2290-2299

    View details for DOI 10.1002/2016GL072388

  • Water, Energy, and Carbon with Artificial Neural Networks (WECANN): a statistically based estimate of global surface turbulent fluxes and gross primary productivity using solar-induced fluorescence BIOGEOSCIENCES Alemohammad, S., Fang, B., Konings, A. G., Aires, F., Green, J. K., Kolassa, J., Miralles, D., Prigent, C., Gentine, P. 2017; 14: 4101-4124

    Abstract

    A new global estimate of surface turbulent fluxes, latent heat flux (LE) and sensible heat flux (H), and gross primary production (GPP) is developed using a machine learning approach informed by novel remotely sensed Solar-Induced Fluorescence (SIF) and other radiative and meteorological variables. This is the first study to jointly retrieve LE, H and GPP using SIF observations. The approach uses an artificial neural network (ANN) with a target dataset generated from three independent data sources, weighted based on triple collocation (TC) algorithm. The new retrieval, named Water, Energy, and Carbon with Artificial Neural Networks (WECANN), provides estimates of LE, H and GPP from 2007 to 2015 at 1° × 1° spatial resolution and on monthly time resolution. The quality of ANN training is assessed using the target data, and the WECANN retrievals are evaluated using eddy covariance tower estimates from FLUXNET network across various climates and conditions. When compared to eddy covariance estimates, WECANN typically outperforms other products, particularly for sensible and latent heat fluxes. Analysing WECANN retrievals across three extreme drought and heatwave events demonstrates the capability of the retrievals in capturing the extent of these events. Uncertainty estimates of the retrievals are analysed and the inter-annual variability in average global and regional fluxes show the impact of distinct climatic events - such as the 2015 El Niño - on surface turbulent fluxes and GPP.

    View details for DOI 10.5194/bg-14-4101-2017

    View details for PubMedCentralID PMC5744880

  • Relationship between vegetation microwave optical depth and cross-polarized backscatter from multi-year Aquarius observations. IEEE JOURNAL OF SELECTED TOPICS IN EARTH OBSERVATIONS AND REMOTE SENSING Rotzer, K., Montzka, C., Entekhabi, D., Konings, A. G., McColl, K. A., Piles, M., Vereecken, H. 2017
  • Estimating global ecosystem iso/anisohydry using active and passive microwave satellite data JOURNAL OF GEOPHYSICAL RESEARCH - BIOGEOSCIENCES Li, Y., Guan, K., Gentine, P., Konings, A. G., Meinzer, F. C., Kimball, J. S., Xu, X., Anderegg, W. R., McDowell, N. G., Martinez-Vilalta, J., Long, D. G., Good, S. P. 2017; 122

    View details for DOI 10.1002/2017JG003958

  • Interacting effects of leaf water potential and biomass on vegetation optical depth JOURNAL OF GEOPHYSICAL RESEARCH - BIOGEOSCIENCES Momen, M., Wood, J. D., Novick, K. A., Pangle, R., Pockman, W. T., McDowell, N. G., Konings, A. G. 2017; 122

    View details for DOI 10.1002/2017JG004145

  • Regionally strong feedbacks between the atmosphere and terrestrial biosphere NATURE GEOSCIENCE Green, J., Konings, A. G., Alemohammad, S., Berry, J., Entekhabi, D., Kolassa, J., Lee, J., Gentine, P. 2017; 10: 410–414

    View details for DOI 10.1038/ngeo2957

  • L-band vegetation optical depth and scattering albedo estimation from SMAP REMOTE SENSING OF ENVIRONMENT Konings, A. G., Piles, M., Das, N., Entekhabi, D. 2017; 198: 460-470
  • The global distribution and dynamics of surface soil moisture NATURE GEOSCIENCE McColl, K. A., Alemohammad, S., Akbar, R., Konings, A., Yueh, S., Entekhabi, D. 2017; 10: 100-104

    View details for DOI 10.1038/ngeo2868

  • Global variations in ecosystem scale isohydricity GLOBAL CHANGE BIOLOGY Konings, A. G., Gentine, P. 2017; 23 (2): 891-905

    Abstract

    Droughts are expected to become more frequent and more intense under climate change. Plant mortality rates and biomass declines in response to drought depend on stomatal and xylem flow regulation. Plants operate on a continuum of xylem and stomatal regulation strategies from very isohydric (strict regulation) to very anisohydric. Coexisting species may display a variety of isohydricity behaviors. As such, it can be difficult to predict how to model the degree of isohydricity at the ecosystem scale by aggregating studies of individual species. This is nonetheless essential for accurate prediction of ecosystem drought resilience. In this study, we define a metric for the degree of isohydricity at the ecosystem scale in analogy with a recent metric introduced at the species level. Using data from the AMSR-E satellite, this metric is evaluated globally based on diurnal variations in microwave vegetation optical depth (VOD), which is directly related to leaf water potential. Areas with low annual mean radiation are found to be more anisohydric. Except for evergreen broadleaf forests in the tropics, which are very isohydric, and croplands, which are very anisohydric, land cover type is a poor predictor of ecosystem isohydricity, in accordance with previous species-scale observations. It is therefore also a poor basis for parameterizing water stress response in land-surface models. For taller ecosystems, canopy height is correlated with higher isohydricity (so that rainforests are mostly isohydric). Highly anisohydric areas show either high or low underlying water use efficiency. In seasonally dry locations, most ecosystems display a more isohydric response (increased stomatal regulation) during the dry season. In several seasonally dry tropical forests, this trend is reversed, as dry-season leaf-out appears to coincide with a shift toward more anisohydric strategies. The metric developed in this study allows for detailed investigations of spatial and temporal variations in plant water behavior.

    View details for DOI 10.1111/gcb.13389

  • Sensitivity of grassland productivity to aridity controlled by stomatal and xylem regulation NATURE GEOSCIENCE Konings, A. G., Williams, A., Gentine, P. 2017; 10: 284-288

    View details for DOI 10.1038/ngeo2903

  • Triple collocation for binary and categorical variables: Application to validating landscape freeze/thaw retrievals REMOTE SENSING OF ENVIRONMENT McColl, K. A., Roy, A., Derksen, C., Konings, A. G., Alemohammed, S. H., Entekhabi, D. 2016; 176: 31-42
  • Vegetation optical depth and scattering albedo retrieval using time series of dual-polarized L-band radiometer observations REMOTE SENSING OF ENVIRONMENT Konings, A. G., Piles, M., Roetzer, K., McColl, K. A., Chan, S. K., Entekhabi, D. 2016; 172: 178-189
  • L-Band Radar Soil Moisture Retrieval Without Ancillary Information IEEE JOURNAL OF SELECTED TOPICS IN APPLIED EARTH OBSERVATIONS AND REMOTE SENSING Bruscantini, C. A., Konings, A. G., Narvekar, P. S., McColl, K. A., Entekhabi, D., Grings, F. M., Karszenbaum, H. 2015; 8 (12): 5526-5540
  • How Many Parameters Can Be Maximally Estimated From a Set of Measurements? IEEE GEOSCIENCE AND REMOTE SENSING LETTERS Konings, A. G., McColl, K. A., Piles, M., Entekhabi, D. 2015; 12 (5): 1081-1085
  • Characterization of precipitation product errors across the United States using multiplicative triple collocation HYDROLOGY AND EARTH SYSTEM SCIENCES Alemohammad, S. H., McColl, K. A., Konings, A. G., Entekhabi, D., Stoffelen, A. 2015; 19 (8): 3489-3503
  • The Effect of Variable Soil Moisture Profiles on P-Band Backscatter IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Konings, A. G., Entekhabi, D., Moghaddam, M., Saatchi, S. S. 2014; 52 (10): 6315-6325
  • Extended triple collocation: Estimating errors and correlation coefficients with respect to an unknown target GEOPHYSICAL RESEARCH LETTERS McColl, K. A., Vogelzang, J., Konings, A. G., Entekhabi, D., Piles, M., Stoffelen, A. 2014; 41 (17): 6229-6236
  • Thermodynamics of an idealized hydrologic cycle WATER RESOURCES RESEARCH Konings, A. G., Feng, X., Molini, A., Manzoni, S., Vico, G., Porporato, A. 2012; 48
  • A phenomenological model for the flow resistance over submerged vegetation WATER RESOURCES RESEARCH Konings, A. G., Katul, G. G., Thompson, S. E. 2012; 48
  • Mean Velocity Profile in a Sheared and Thermally Stratified Atmospheric Boundary Layer PHYSICAL REVIEW LETTERS Katul, G. G., Konings, A. G., Porporato, A. 2011; 107 (26)

    Abstract

    A stability correction function φ(m)(ζ) that accounts for distortions to the logarithmic mean velocity profile (MVP) in the lower atmosphere caused by thermal stratification was proposed by Monin and Obukhov in the 1950s using dimensional analysis. Its universal character was established from many field experiments. However, theories that describe the canonical shape of φ(m)(ζ) are still lacking. A previous link between the spectrum of turbulence and the MVP is expanded here to include the effects of thermal stratification on the turbulent kinetic energy dissipation rate and eddy-size anisotropy. The resulting theory provides a novel explanation for the power-law exponents and coefficients already reported for φ(m)(ζ) from numerous field experiments.

    View details for DOI 10.1103/PhysRevLett.107.268502

    View details for Web of Science ID 000298609000019

    View details for PubMedID 22243189

  • Drought sensitivity of patterned vegetation determined by rainfall-land surface feedbacks JOURNAL OF GEOPHYSICAL RESEARCH-BIOGEOSCIENCES Konings, A. G., Dekker, S. C., Rietkerk, M., Katul, G. G. 2011; 116
  • Unsteady overland flow on flat surfaces induced by spatial permeability contrasts ADVANCES IN WATER RESOURCES Thompson, S., Katul, G., Konings, A., Ridolfi, L. 2011; 34 (8): 1049-1058
  • Comparative hydrology across AmeriFlux sites: The variable roles of climate, vegetation, and groundwater WATER RESOURCES RESEARCH Thompson, S. E., Harman, C. J., Konings, A. G., Sivapalan, M., Neal, A., Troch, P. A. 2011; 47
  • Effect of Radiative Transfer Uncertainty on L-Band Radiometric Soil Moisture Retrieval IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Konings, A. G., Entekhabi, D., Chan, S. K., Njoku, E. G. 2011; 49 (7): 2686-2698
  • The rainfall-no rainfall transition in a coupled land-convective atmosphere system GEOPHYSICAL RESEARCH LETTERS Konings, A. G., Katul, G. G., Porporato, A. 2010; 37
  • Conditioning Stochastic Rainfall Replicates on Remote Sensing Data IEEE TRANSACTIONS ON GEOSCIENCE AND REMOTE SENSING Wojcik, R., McLaughlin, D., Konings, A. G., Entekhabi, D. 2009; 47 (8): 2436-2449