Large‐Scale Droughts Responsible for Dramatic Reductions of Terrestrial Net Carbon Uptake Over North America in 2011 and 2012

He, Wei; Ju, Weimin; Schwalm, Christopher R.; Sippel, Sebastian; Wu, Xiaocui; He, Qian; Song, Le; Zhang, Chunhua; Li, Jing; Sitch, Stephen; Viovy, Nicolas; Friedlingstein, Pierre; Jain, Atul K.

doi:10.1029/2018jg004520

Cited by 41 publications

(24 citation statements)

References 104 publications

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“…Despite these difficulties, several studies have attempted to quantify ecosystem legacy effects by leveraging approaches such as eddy covariance (Shen et al 2016; Yang et al 2016; He et al 2018), remote sensing products (Gazol et al 2018, Wu et al 2018, Yu et al 2017), ecosystem models (Shen et al 2016), model intercomparison projects (Anderegg et al 2015a, Kolus et al 2019), or a diverse array of the aforementioned data sources (Schwalm et al 2017; Kannenberg et al 2019c). While these studies quantify legacy effects at different scales, using different methods, in a wide variety of ecosystem processes, one commonality is clear: legacy effects in C uptake at the ecosystem scale seem to be smaller and shorter than those in tree rings.…”

Section: Introductionmentioning

confidence: 99%

Ghosts of the past: how drought legacy effects shape forest functioning and carbon cycling

2020

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Multi-year lags in tree drought recovery, termed 'drought legacy effects', are important for understanding the impacts of drought on forest ecosystems, including carbon (C) cycle feedbacks to climate change. Despite the ubiquity of lags in drought recovery, large uncertainties remain regarding the mechanistic basis of legacy effects and their importance for the C cycle. In this review, we identify the approaches used to study legacy effects, from tree rings to whole forests. We then discuss key knowledge gaps pertaining to the causes of legacy effects, and how the various mechanisms that may contribute these lags in drought recovery could have contrasting implications for the C cycle. Furthermore, we conduct a novel data synthesis and find that legacy effects differ drastically in both size and length across the US depending on if they are identified in tree rings versus gross primary productivity. Finally, we highlight promising approaches for future research to improve our capacity to model legacy effects and predict their impact on forest health. We emphasise that a holistic view of legacy effectsfrom tissues to whole forestswill advance our understanding of legacy effects and stimulate efforts to investigate drought recovery via experimental, observational and modelling approaches.

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Section: Introductionmentioning

confidence: 99%

Ghosts of the past: how drought legacy effects shape forest functioning and carbon cycling

2020

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“…Approximately 25% of global anthropogenic CO 2 emissions are counteracted by terrestrial ecosystems [1], but the terrestrial carbon cycle is easily affected by climate extremes. The increase in the frequency and intensity of climatic extremes predicted by global climate models in the 21st century [2] indicated that anthropogenic activities are changing the climate [3], which has an evident impact on the composition, structure and functions of terrestrial ecosystems and indirectly alters the terrestrial carbon balance [4][5][6].…”

Section: Introductionmentioning

confidence: 99%

Concurrent and Lagged Effects of Extreme Drought Induce Net Reduction in Vegetation Carbon Uptake on Tibetan Plateau

Sun

Liu

et al. 2020

Remote Sensing

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Climatic extremes have adverse concurrent and lagged effects on terrestrial carbon cycles. Here, a concurrent effect refers to the occurrence of a latent impact during climate extremes, and a lagged effect appears sometime thereafter. Nevertheless, the uncertainties of these extreme drought effects on net carbon uptake and the recovery processes of vegetation in different Tibetan Plateau (TP) ecosystems are poorly understood. In this study, we calculated the Standardised Precipitation–Evapotranspiration Index (SPEI) based on meteorological datasets with an improved spatial resolution, and we adopted the Carnegie–Ames–Stanford approach model to develop a net primary production (NPP) dataset based on multiple datasets across the TP during 1982–2015. On this basis, we quantised the net reduction in vegetation carbon uptake (NRVCU) on the TP, investigated the spatiotemporal variability of the NPP, NRVCU and SPEI, and analysed the NRVCUs that are caused by the concurrent and lagged effects of extreme drought and the recovery times in different ecosystems. According to our results, the Qaidam Basin and most forest regions possessed a significant trend towards drought during 1982–2015 (with Slope of SPEI < 0, P < 0.05), and the highest frequency of extreme drought events was principally distributed in the Qaidam Basin, with three to six events. The annual total net reduction in vegetation carbon uptake on the TP experienced a significant downward trend from 1982 to 2015 (−0.0018 ± 0.0002 PgC year−1, P < 0.001), which was negatively correlated with annual total precipitation and annual mean temperature (P < 0.05). In spatial scale, the NRVCU decrement was widely spread (approximately 55% of grids) with 17.86% of the area displaying significant declining trends (P < 0.05), and the sharpest declining trend (Slope ≤ −2) was mainly concentrated in southeastern TP. For the alpine steppe and alpine meadow ecosystems, the concurrent and lagged effects of extreme drought induced a significant difference in NRVCU (P < 0.05), while forests presented the opposite results. The recovery time comparisons from extreme drought suggest that forests require more time (27.62% of grids ≥ 6 years) to recover their net carbon uptakes compared to grasslands. Therefore, our results emphasise that extreme drought events have stronger lagged effects on forests than on grasslands on the TP. The improved resilience of forests in coping with extreme drought should also be considered in future research.

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“…Besides, the positive anomalies of temperature during flash droughts might also increase ecosystem respiration and further intensify the carbon loss of terrestrial ecosystem [ 29 ]. He et al [ 20 ] found that the enhanced respiration caused more carbon loss for grasslands and croplands during the 2012 flash drought over North America. The responses of LAI occur during 79% of the flash droughts, indicating the structural changes of the ecosystem during flash droughts.…”

Section: Discussionmentioning

confidence: 99%

“…Ecosystem photosynthesis and respiratory processes can be suppressed when vegetation is under water stress [ 33 ] and GPP is the total ecosystem carbon uptake representing the dynamics of vegetation photosynthetic functioning. NPP is the discrepancy between GPP and autotrophic respiration integrating the impacts of drought on photosynthesis and respiration [ 20 ]. LAI is the green leaf area per unit ground area, which can be used to detect changes of vegetation state (e.g., defoliation).…”

Section: Methodsmentioning

confidence: 99%

“…NPP is controlled by GPP and vegetation autotrophic respiration. Vegetation respiration could be impaired under severe drought, whereas sometimes it can be enhanced, thereby further increasing carbon loss for some cases of drought [ 20 ]. Otkin et al [ 12 ] assessed the evolution of vegetation conditions during the 2012 flash drought over the U.S.…”

Section: Introductionmentioning

confidence: 99%

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Remote sensing of the impact of flash drought events on terrestrial carbon dynamics over China

Zhang

Yuan

Otkin

2020

Carbon Balance Manage

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Background Flash drought poses a great threat to terrestrial ecosystems and influences carbon dynamics due to its unusually rapid onset and increasing frequency in a warming climate. Understanding the response of regional terrestrial carbon dynamics to flash drought requires long-term observations of carbon fluxes and soil moisture at a large scale. Here, MODIS satellite observations of ecosystem productivity and ERA5 reanalysis modeling of soil moisture are used to detect the response of ecosystems to flash drought over China. Results The results show that GPP, NPP, and LAI respond to 79–86% of the flash drought events over China, with highest and lowest response frequency for NPP and LAI, respectively. The discrepancies in the response of GPP, NPP, and LAI to flash drought result from vegetation physiological and structural changes. The negative anomalies of GPP, NPP, and LAI occur within 19 days after the start of flash drought, with the fastest response occurring over North China, and slower responses in southern and northeastern China. Water use efficiency (WUE) is increased in most regions of China except for western regions during flash drought, illustrating the resilience of ecosystems to rapid changes in soil moisture conditions. Conclusions This study shows the rapid response of ecosystems to flash drought based on remote-sensing observations, especially for northern China with semiarid climates. Besides, NPP is more sensitive than GPP and LAI to flash drought under the influence of vegetation respiration and physiological regulations. Although the mean WUE increases during flash drought over most of China, western China shows less resilience to flash drought with little changes in WUE during the recovery stage. This study highlights the impacts of flash drought on ecosystems and the necessity to monitor rapid drought intensification.

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Large‐Scale Droughts Responsible for Dramatic Reductions of Terrestrial Net Carbon Uptake Over North America in 2011 and 2012

Cited by 41 publications

References 104 publications

Ghosts of the past: how drought legacy effects shape forest functioning and carbon cycling

Ghosts of the past: how drought legacy effects shape forest functioning and carbon cycling

Concurrent and Lagged Effects of Extreme Drought Induce Net Reduction in Vegetation Carbon Uptake on Tibetan Plateau

Remote sensing of the impact of flash drought events on terrestrial carbon dynamics over China

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