Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

Stoy, Paul C.; El‐Madany, Tarek S.; Fisher, Joshua B.; Gentine, Pierre; Gerken, Tobias; Good, Stephen P.; Klosterhalfen, Anne; Miralles, Diego G.; Pérez-Priego, Óscar; Rigden, A. J.; Skaggs, Todd H.; Wohlfahrt, Georg; Anderson, Ray G.; Coenders-Gerrits, Miriam; Jung, Martin; Maes, Wouter; Mammarella, Ivan; Mauder, Matthias; Migliavacca, Mirco; Nelson, Jacob A.; Poyatos, Rafael; Reichstein, Markus; Scott, Russell L.; Wolf, Sebastian

doi:10.5194/bg-2019-85

Cited by 42 publications

(73 citation statements)

References 158 publications

(205 reference statements)

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“…Our results also show that both increased woodland cover and increased woodland density under climate change conditions (Rundqvist et al, ) will result in larger controls of the water fluxes by the canopies of deciduous trees as opposed to the understorey vegetation. However, our upscaling exercise also shows that adequately accounting for understorey components (and transpiration vs. evaporation processes; Stoy et al, ) may be necessary to constrain future hydrological changes in these areas. The highly variable and patchy nature of subarctic vegetation may require flux upscaling approaches considering spatial variation not only of land cover (Hartley et al, ), but also of LAI (Stoy, Williams, et al, ).…”

Section: Discussionmentioning

confidence: 87%

Transpiration from subarctic deciduous woodlands: Environmental controls and contribution to ecosystem evapotranspiration

et al. 2020

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Potential land–climate feedbacks in subarctic regions, where rapid warming is driving forest expansion into the tundra, may be mediated by differences in transpiration of different plant functional types. Here, we assess the environmental controls of overstorey transpiration and its relevance for ecosystem evapotranspiration in subarctic deciduous woodlands. We measured overstorey transpiration of mountain birch canopies and ecosystem evapotranspiration in two locations in northern Fennoscandia, having dense (Abisko) and sparse (Kevo) overstories. For Kevo, we also upscale chamber‐measured understorey evapotranspiration from shrubs and lichen using a detailed land cover map. Subdaily evaporative fluxes were not affected by soil moisture and showed similar controls by vapour pressure deficit and radiation across sites. At the daily timescale, increases in evaporative demand led to proportionally higher contributions of overstorey transpiration to ecosystem evapotranspiration. For the entire growing season, the overstorey transpired 33% of ecosystem evapotranspiration in Abisko and only 16% in Kevo. At this latter site, the understorey had a higher leaf area index and contributed more to ecosystem evapotranspiration compared with the overstorey birch canopy. In Abisko, growing season evapotranspiration was 27% higher than precipitation, consistent with a gradual soil moisture depletion over the summer. Our results show that overstorey canopy transpiration in subarctic deciduous woodlands is not the dominant evaporative flux. However, given the observed environmental sensitivity of evapotranspiration components, the role of deciduous trees in driving ecosystem evapotranspiration may increase with the predicted increases in tree cover and evaporative demand across subarctic regions.

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Section: Discussionmentioning

confidence: 87%

Transpiration from subarctic deciduous woodlands: Environmental controls and contribution to ecosystem evapotranspiration

et al. 2020

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“…The contribution of evaporation is undesirable in estimating stomatal ozone uptake because evaporation is not directly related to ozone dry deposition. While advances with respect to the ecosystem‐scale transpiration fraction of evapotranspiration (e.g., Stoy et al, ) will help estimates of surface conductance more strictly represent g s , there is still the issue that surface conductance includes the contribution of turbulent transport of water vapor through the canopy. Assuming similar in‐canopy concentration profiles of ozone and water vapor, the contribution of in‐canopy turbulence to the surface conductance may be desirable in an ecosystem‐scale estimate of g s .…”

Section: Theory Models and Observations Of Terrestrial Ozone Deposimentioning

confidence: 99%

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Clifton

Fiore

Massman

et al. 2020

Reviews of Geophysics

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Dry deposition of ozone is an important sink of ozone in near‐surface air. When dry deposition occurs through plant stomata, ozone can injure the plant, altering water and carbon cycling and reducing crop yields. Quantifying both stomatal and nonstomatal uptake accurately is relevant for understanding ozone's impact on human health as an air pollutant and on climate as a potent short‐lived greenhouse gas and primary control on the removal of several reactive greenhouse gases and air pollutants. Robust ozone dry deposition estimates require knowledge of the relative importance of individual deposition pathways, but spatiotemporal variability in nonstomatal deposition is poorly understood. Here we integrate understanding of ozone deposition processes by synthesizing research from fields such as atmospheric chemistry, ecology, and meteorology. We critically review methods for measurements and modeling, highlighting the empiricism that underpins modeling and thus the interpretation of observations. Our unprecedented synthesis of knowledge on deposition pathways, particularly soil and leaf cuticles, reveals process understanding not yet included in widely used models. If coordinated with short‐term field intensives, laboratory studies, and mechanistic modeling, measurements from a few long‐term sites would bridge the molecular to ecosystem scales necessary to establish the relative importance of individual deposition pathways and the extent to which they vary in space and time. Our recommended approaches seek to close knowledge gaps that currently limit quantifying the impact of ozone dry deposition on air quality, ecosystems, and climate.

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“…2019; Stoy et al, 2019;Sun et al, 2017). Theoretical advancements in nonequilibrium thermodynamics and Maximum Entropy Production (MEP) could be incorporated into the classical ET theories (Xu et al, 2019;Zhang et al, 2016a).…”

Section: Ignorance Of the Effects Of Irrigationmentioning

confidence: 99%

Evaluation of global terrestrial evapotranspiration by state-of-the-art approaches in remote sensing, machine learning, and land surface models

Pan¹,

Pan²,

Tian³

et al. 2019

Preprint

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Abstract. Evapotranspiration (ET) is a critical component in global water cycle and links terrestrial water, carbon and energy cycles. Accurate estimate of terrestrial ET is important for hydrological, meteorological, and agricultural research and applications, such as quantifying surface energy and water budgets, weather forecasting, and scheduling of irrigation. However, direct measurement of global terrestrial ET is not feasible. Here, we first gave a retrospective introduction to the basic theory and recent developments of state-of-the-art approaches for estimating global terrestrial ET, including remote sensing-based physical models, machine learning algorithms and land surface models (LSMs). Then, we utilized six remote sensing-based models (including four physical models and two machine learning algorithms) and fourteen LSMs to analyze the spatial and temporal variations in global terrestrial ET. The results showed that the mean annual global terrestrial ET ranged from 50.7 × 103 km3 yr−1（454 mm yr−1）to 75.7 × 103 km3 yr−1 (6977 mm yr−1), with the average being 65.5 × 103 km3 yr−1 (588 mm yr−1), during 1982–2011. LSMs had significant uncertainty in the ET magnitude in tropical regions especially the Amazon Basin, while remote sensing-based ET products showed larger inter-model range in arid and semi-arid regions than LSMs. LSMs and remote sensing-based physical models presented much larger inter-annual variability (IAV) of ET than machine learning algorithms in southwestern U.S. and the Southern Hemisphere, particularly in Australia. LSMs suggested stronger control of precipitation on ET IAV than remote sensing-based models. The ensemble remote sensing-based physical models and machine-learning algorithm suggested significant increasing trends in global terrestrial ET at the rate of 0.62 mm yr−2 (p 0.05), even though most of the individual LSMs reproduced the increasing trend. Moreover, all models suggested a positive effect of vegetation greening on ET intensification. Spatially, all methods showed that ET significantly increased in western and southern Africa, western India and northeastern Australia, but decreased severely in southwestern U.S., southern South America and Mongolia. Discrepancies in ET trend mainly appeared in tropical regions like the Amazon Basin. The ensemble means of the three ET categories showed generally good consistency, however, considerable uncertainties still exist in both the temporal and spatial variations in global ET estimates. The uncertainties were induced by multiple factors, including parameterization of land processes, meteorological forcing, lack of in situ measurements, remote sensing acquisition and scaling effects. Improvements in the representation of water stress and canopy dynamics are essentially needed to reduce uncertainty in LSM-simulated ET. Utilization of latest satellite sensors and deep learning methods, theoretical advancements in nonequilibrium thermodynamics, and application of integrated methods that fuse different ET estimates or relevant key biophysical variables will improve the accuracy of remote sensing-based models.

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Reviews and syntheses: Turning the challenges of partitioning ecosystem evaporation and transpiration into opportunities

Cited by 42 publications

References 158 publications

Transpiration from subarctic deciduous woodlands: Environmental controls and contribution to ecosystem evapotranspiration

Transpiration from subarctic deciduous woodlands: Environmental controls and contribution to ecosystem evapotranspiration

Dry Deposition of Ozone Over Land: Processes, Measurement, and Modeling

Evaluation of global terrestrial evapotranspiration by state-of-the-art approaches in remote sensing, machine learning, and land surface models

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