Soil Moisture and Atmospheric Aridity Impact Spatio‐Temporal Changes in Evapotranspiration at a Global Scale

Zhang, Wenmin; Koch, Julian; Wei, Fengsi; Zeng, Zhenzhong; Fang, Zhongxiang; Fensholt, Rasmus

doi:10.1029/2022jd038046

Cited by 8 publications

(3 citation statements)

References 57 publications

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“…Besides VPD, WUE DEPART is likely controlled by multiple other environmental drivers, and the relationship between WUE and these drivers likely depends on plant functional type (Grossiord et al., 2020). For example, it is known that soil moisture can modulate the relationship between WUE and VPD (Novick et al., 2016), depending on plant physiological strategy (Ambika & Mishra, 2021; W. Zhang et al., 2023). The inconsistent relationship between WUE DEPART and VPD at the sub‐yearly timescale (Figures 4 and 5) suggests that implementing assumptions of stomatal optimality—which result in assuming strong coupling of WUE and VPD—may be inappropriate for partitioning ET in semiarid ecosystems at certain timescales.…”

Section: Discussionmentioning

confidence: 99%

Section: Temporal Scale Wue and T/etmentioning

confidence: 99%

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A Semi‐Mechanistic Model for Partitioning Evapotranspiration Reveals Transpiration Dominates the Water Flux in Drylands

Reich,

Samuels‐Crow,

Bradford

et al. 2024

JGR Biogeosciences

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Popular evapotranspiration (ET) partitioning methods make assumptions that might not be well‐suited to dryland ecosystems, such as high sensitivity of plant water‐use efficiency (WUE) to vapor pressure deficit (VPD). Our objectives were to (a) create an ET partitioning model that can produce fine‐scale estimates of transpiration (T) in drylands, and (b) use this approach to evaluate how climate controls T and WUE across ecosystem types and timescales along a dryland aridity gradient. We developed a novel, semi‐mechanistic ET partitioning method using a Bayesian approach that constrains abiotic evaporation using process‐based models, and loosely constrains time‐varying WUE within an autoregressive framework. We used this method to estimate daily T and weekly WUE across seven dryland ecosystem types and found that T dominates ET across the aridity gradient. Then, we applied cross‐wavelet coherence analysis to evaluate the temporal coherence between focal response variables (WUE and T/ET) and environmental variables. At yearly scales, we found that WUE at less arid, higher elevation sites was primarily limited by atmospheric moisture demand, and WUE at more arid, lower elevation sites was primarily limited by moisture supply. At sub‐yearly timescales, WUE and VPD were sporadically correlated. Hence, ecosystem‐scale dryland WUE is not always sensitive to changes in VPD at short timescales, despite this being a common assumption in many ET partitioning models. This new ET partitioning method can be used in dryland ecosystems to better understand how climate influences physically and biologically driven water fluxes.

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Section: Discussionmentioning

confidence: 99%

Section: Temporal Scale Wue and T/etmentioning

confidence: 99%

A Semi‐Mechanistic Model for Partitioning Evapotranspiration Reveals Transpiration Dominates the Water Flux in Drylands

Reich,

Samuels‐Crow,

Bradford

et al. 2024

JGR Biogeosciences

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show abstract

“…In addition, grassland covers an area of 52.5 million km 2 of Earth's land surface and also acts as an important carbon sink, with the carbon stored as root biomass and soil organic carbon [10]. Nevertheless, extreme climate events, particularly droughts, seriously threaten terrestrial ecosystem structures and functions that could essentially weaken the role of forests and grasslands as carbon sinks and even make ecosystems become carbon sources [11,12].…”

Section: Introductionmentioning

confidence: 99%

The Divergent Resistance and Resilience of Forest and Grassland Ecosystems to Extreme Summer Drought in Carbon Sequestration

Lu,

Yan

2023

Land

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It is projected that extreme drought events will become more frequent and more severe across many regions of the globe by the end of the 21st century. Despite the substantial efforts that have been made to explore the impacts of droughts on terrestrial ecosystems, our understanding of the response of diverse ecosystems, including resistance and resilience, remains unclear. A total of 16 site years of eddy covariance-based carbon flux data were used to reveal the different responses of forest and grassland ecosystems to two extreme summer droughts. We found that the carbon fluxes of the forest, namely gross primary productivity (GPP), ecosystem respiration (Re), and the net ecosystem carbon exchange (NEE), exhibited distinct seasonal patterns with a single peak. However, GPP and NEE of grassland showed multiple peaks owing to hay harvesting throughout one year. Meanwhile, all climate factors jointly affected the seasonal dynamics in the NEE of the forest, whereas solar radiation only dominated the variability in the NEE of grassland. Moreover, the optimal response relationship was quadratic between the vapor pressure deficit (VPD) and the NEE, with the thresholds being 5.46 and 5.84 for forest and grassland, respectively. Owing to the large increase in VPD during the droughts of 2003 and 2018, the carbon sequestration of forest and grassland reduced sharply and even altered from carbon sink to carbon source. Compared with grassland, forest GPP showed stronger resistance with weaker resilience to droughts. However, larger resilience appeared for both forest and grassland NEE relative to their resistance. All analyses reflect the different adaptive strategies among plant functional types, which is crucial to evaluate ecosystem carbon sequestration to overcome future climate change.

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Summer evapotranspiration-cloud feedbacks in land-atmosphere interactions over Europe

Zhang,

Wagner,

Goergen

et al. 2024

Clim Dyn

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Land-atmosphere (L-A) feedbacks are important for understanding regional climate functioning. However, the accurate quantification of feedback strength is challenging due to complex, nonlinear interactions and varying background atmospheric conditions. In particular, the role of cloud water in the terrestrial water cycle is often ignored or simplified in previous L-A feedback studies, which overlook the relationship between evapotranspiration (ET) and cloud water (TQC). This study diagnoses the interactions between $$\:ET$$, $$\:TQC$$ and its dynamics ($$\:\varDelta\:TQC/\varDelta\:t$$) under different atmospheric conditions by conducting correlation and a novel scaling analysis, based on a coupled regional climate model simulation. Contrasting correlation relationships between $$\:ET$$, $$\:TQC$$ and $$\:\varDelta\:TQC/\varDelta\:t$$ were identified, indicating the positive feedback between $$\:ET$$ and the dynamics in cloud water. Two types of positive scaling relationships between $$\:ET$$ and $$\:\varDelta\:TQC/\varDelta\:t$$ were identified by K-means clustering. The analysis shows a contrasting north-south distribution of the scaling relationship that is similar to the spatial distribution of energy-limited and water-limited $$\:ET$$ regimes, highlighting the role of ET regimes in modulating the $$\:ET$$ - $$\:\varDelta\:TQC/\varDelta\:t$$ scaling relationships. Moreover, the feedback strength and scaling relationship are affected by atmospheric moisture flux dynamics, providing remote moisture sources and altering dry/wet conditions. Our results highlight the role of cloud water in the atmospheric part of the L-A process chain and reveal the effect of different atmospheric conditions on L-A interactions based on the new analysis framework.

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Soil Moisture and Atmospheric Aridity Impact Spatio‐Temporal Changes in Evapotranspiration at a Global Scale

Cited by 8 publications

References 57 publications

A Semi‐Mechanistic Model for Partitioning Evapotranspiration Reveals Transpiration Dominates the Water Flux in Drylands

A Semi‐Mechanistic Model for Partitioning Evapotranspiration Reveals Transpiration Dominates the Water Flux in Drylands

The Divergent Resistance and Resilience of Forest and Grassland Ecosystems to Extreme Summer Drought in Carbon Sequestration

Summer evapotranspiration-cloud feedbacks in land-atmosphere interactions over Europe

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