Carbon fluxes and interannual drivers in a temperate forest ecosystem assessed through comparison of top-down and bottom-up approaches

Ouimette, A.; Ollinger, Scott V.; Richardson, Andrew D.; Hollinger, David Y.; Keenan, Trevor F.; Lepine, L. C.; Vadeboncoeur, Matthew A.

doi:10.1016/j.agrformet.2018.03.017

Cited by 40 publications

(31 citation statements)

References 67 publications

(27 reference statements)

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“…Previous attempts to uncover legacy effects in larger scale C cycle processes have been limited by their large spatial and temporal breadth (Schwalm et al, 2017;Wu et al, 2017), while other studies linking tree rings to GPP have not examined this question in the context of environmental stress (Mund et al, 2010;Ouimette et al, 2018;Rocha et al, 2006;Rollinson et al, 2017). Thus, we lack a comprehensive understanding of how legacy effects affect the C cycle.…”

Section: Drought Effects and Legacy Effects In Gppmentioning

confidence: 98%

Linking drought legacy effects across scales: From leaves to tree rings to ecosystems

Kannenberg

Novick

Alexánder³

et al. 2019

Global Change Biology

159

143

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Severe drought can cause lagged effects on tree physiology that negatively impact forest functioning for years. These “drought legacy effects” have been widely documented in tree‐ring records and could have important implications for our understanding of broader scale forest carbon cycling. However, legacy effects in tree‐ring increments may be decoupled from ecosystem fluxes due to (a) postdrought alterations in carbon allocation patterns; (b) temporal asynchrony between radial growth and carbon uptake; and (c) dendrochronological sampling biases. In order to link legacy effects from tree rings to whole forests, we leveraged a rich dataset from a Midwestern US forest that was severely impacted by a drought in 2012. At this site, we compiled tree‐ring records, leaf‐level gas exchange, eddy flux measurements, dendrometer band data, and satellite remote sensing estimates of greenness and leaf area before, during, and after the 2012 drought. After accounting for the relative abundance of tree species in the stand, we estimate that legacy effects led to ~10% reductions in tree‐ring width increments in the year following the severe drought. Despite this stand‐scale reduction in radial growth, we found that leaf‐level photosynthesis, gross primary productivity (GPP), and vegetation greenness were not suppressed in the year following the 2012 drought. Neither temporal asynchrony between radial growth and carbon uptake nor sampling biases could explain our observations of legacy effects in tree rings but not in GPP. Instead, elevated leaf‐level photosynthesis co‐occurred with reduced leaf area in early 2013, indicating that resources may have been allocated away from radial growth in conjunction with postdrought upregulation of photosynthesis and repair of canopy damage. Collectively, our results indicate that tree‐ring legacy effects were not observed in other canopy processes, and that postdrought canopy allocation could be an important mechanism that decouples tree‐ring signals from GPP.

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Section: Drought Effects and Legacy Effects In Gppmentioning

confidence: 98%

Linking drought legacy effects across scales: From leaves to tree rings to ecosystems

Kannenberg

Novick

Alexánder³

et al. 2019

Global Change Biology

159

143

View full text Add to dashboard Cite

show abstract

“…CO 2 ecosystem and soil respiration cannot be estimated from forest mensuration methods. Examples of forest mensuration, including soil CO 2 and ecosystem respiration efflux, in relation to eddy covariance approaches are well represented (Curtis et al, 2002;Luyssaert et al, 2009;Ouimette et al, 2018).…”

Section: Discussionmentioning

confidence: 99%

Peer Review #3 of "California air resources board forest carbon protocol invalidates offsets (v0.1)"

2019

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The commercial asset value of sequestered forest carbon is based on protocols employed globally, however, their scientific basis has not been validated. We review and analyze commercial forest carbon protocols, claimed to have reduced net greenhouse gas emissions, issued by the California Air Resources Board and validated by the Climate Action Reserve (CARB-CAR). CARB-CAR forest carbon offsets, based on forest mensuration and model simulation, are compared to a global database of directly measured forest carbon sequestration, or net ecosystem exchange (NEE) of forest CO 2. NEE is a meteorologically based method integrating CO 2 fluxes between the atmosphere, forest and soils and is independent of the CARB-CAR methodology. Annual carbon accounting results for CAR681 are compared with NEE for the Ameriflux site, Howland Forest Maine, USA, (Ho-1), the only site where both methods were applied contemporaneously, invalidating CARB-CAR protocol offsets. We then test the null hypothesis that CARB-CAR project population data fall within global NEE population values for natural and managed forests measured in the field; net annual gC m-2 yr-1 are compared for both protocols. Irrespective of geography, biome and project type, the CARB-CAR population mean is significantly different from the NEE population mean at the 95% confidence interval, rejecting the null hypothesis. The CARB-CAR population exhibits standard deviation ~5x that of known interannual NEE ranges, is overcrediting biased, incapable of detecting forest transition to net positive CO 2 emissions, and exceeds the 5% CARB compliance limit for invalidation. Exclusion of CO 2 efflux via soil and ecosystem respiration precludes a valid net carbon accounting result for CARB-CAR and related protocols, consistent with our findings. Protocol invalidation risk extends to vendors and policy platforms such as the United Nations Program on Reducing Emissions from Deforestation and Forest Degradation (REDD+) and the Paris Agreement. We suggest that CARB-CAR and related protocols

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“…Tree ring increments recorded at two HAFE sites showed relatively lower correlations (0.22<r<0. 63) with ForDRI. This could be because the dominant tree species in the park (oak) are drought-tolerant.…”

Section: Evaluating Fordri With Bowen Ratiomentioning

confidence: 99%

Forest Drought Response Index (ForDRI): A New Combined Model to Monitor Forest Drought in the Eastern United States

Tadesse

Hollinger²,

Bayissa

et al. 2020

Preprint

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Monitoring drought impacts in forest ecosystems is a complex process, because forest ecosystems are composed of different species with heterogeneous structural compositions. Even though forest drought status is a key control on the carbon cycle, very few indices exist to monitor and predict forest drought stress. The Forest Drought Indicator (ForDRI) is a new monitoring tool developed by the National Drought Mitigation Center (NDMC) to identify forest drought stress. ForDRI integrates 12 types of data, including satellite, climate, evaporative demand, ground water, and soil moisture, into a single hybrid index to estimate tree stress. The model uses Principal Component Analysis (PCA) to determine the contribution of each input variable based on its covariance in the historical records (2003–2017). A 15-year time series of 780 ForDRI maps at a weekly interval were produced. The ForDRI values at a 12.5km spatial resolution were compared with normalized weekly Bowen ratio data, a biophysically based indicator of stress, from nine AmeriFlux sites. There were strong and significant correlations between Bowen ratio data and ForDRI at sites that had experienced intense drought. In addition, tree ring annual increment data at eight sites in four eastern U.S. national parks were compared with ForDRI values at the corresponding sites. The correlation between ForDRI and tree ring increments at the selected eight sites during the summer season ranged between 0.46 and 0.75. Generally, the correlation between the ForDRI and normalized Bowen ratio or tree ring increment are reasonably good and indicate the usefulness of the ForDRI model for estimating drought stress and providing decision support on forest drought management.

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Carbon fluxes and interannual drivers in a temperate forest ecosystem assessed through comparison of top-down and bottom-up approaches

Cited by 40 publications

References 67 publications

Linking drought legacy effects across scales: From leaves to tree rings to ecosystems

Linking drought legacy effects across scales: From leaves to tree rings to ecosystems

Peer Review #3 of "California air resources board forest carbon protocol invalidates offsets (v0.1)"

Forest Drought Response Index (ForDRI): A New Combined Model to Monitor Forest Drought in the Eastern United States

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