Modeling Ambitions Outpace Observations of Forest Carbon Allocation

Babst, Flurin; Friend, A. D.; Karamihalaki, Maria; Wei, Jingshu; Arx, Georg von; Papale, Dario; Peters, Richard L.

doi:10.1016/j.tplants.2020.10.002

Cited by 34 publications

(23 citation statements)

References 72 publications

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“…With respect to all three of these sources of uncertainty—climate effects, disturbance and demographic processes, and CO2 fertilization—adding tree rings to NFIs strengthens the empirical foundation for improving models and scaling of carbon dynamics from leaf to globe (Fisher et al 2018 , Kannenberg et al 2019 ). At the scale of individual trees, tree rings form an obvious basis for parameterizing and validating next-generation mechanistic models of tree growth that explicitly represent wood formation—a key line of inquiry to help understand whether tree growth is controlled by photosynthesis (is source limited) or if in fact photosynthesis is controlled by the conditions needed to support growth, such as adequate turgor pressure (growth is sink limited; Körner 2013 , Fatichi et al 2014 , Körner 2015 , Sass-Klaassen 2015 , Friend et al 2019 , Babst et al 2020 ), the latter of which would fundamentally undermine the notion of CO2 fertilization and the prediction of a strong forest carbon sink in the coming decades. Tree-ring data have been and are being used to estimate biomass increment at the forest stand level and forest ecosystem fluxes (Dye et al 2016 , Metsaranta et al 2018 , Metsaranta 2019 ), demonstrating the feasibility of forest carbon scaling from tree rings.…”

Section: Carbon Cycle Uncertainties Carbon Accounting and Atmospheric...mentioning

confidence: 99%

Adding Tree Rings to North America's National Forest Inventories: An Essential Tool to Guide Drawdown of Atmospheric CO2

et al. 2021

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Tree-ring time series provide long-term, annually resolved information on the growth of trees. When sampled in a systematic context, tree-ring data can be scaled to estimate the forest carbon capture and storage of landscapes, biomes, and—ultimately—the globe. A systematic effort to sample tree rings in national forest inventories would yield unprecedented temporal and spatial resolution of forest carbon dynamics and help resolve key scientific uncertainties, which we highlight in terms of evidence for forest greening (enhanced growth) versus browning (reduced growth, increased mortality). We describe jump-starting a tree-ring collection across the continent of North America, given the commitments of Canada, the United States, and Mexico to visit forest inventory plots, along with existing legacy collections. Failing to do so would be a missed opportunity to help chart an evidence-based path toward meeting national commitments to reduce net greenhouse gas emissions, urgently needed for climate stabilization and repair.

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Section: Carbon Cycle Uncertainties Carbon Accounting and Atmospheric...mentioning

confidence: 99%

Adding Tree Rings to North America's National Forest Inventories: An Essential Tool to Guide Drawdown of Atmospheric CO2

et al. 2021

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“…TLS has the potential to discriminate equifinal model simulations with similar land fluxes but contrasting structure. On-site trait measurements (Figure 7) could further help avoid those risks of equifinality (Babst et al 2020;Peaucelle et al 2019).…”

Section: Model Equifinalitymentioning

confidence: 99%

Using terrestrial laser scanning to constrain forest ecosystem structure and functions in the Ecosystem Demography model (ED2.2)

Meunier

Moorthy

Peaucelle

et al. 2021

Preprint

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Abstract. Terrestrial Biosphere Modeling (TBM) is an invaluable approach for studying plant-atmosphere interactions at multiple spatial and temporal scales, as well as the global change impacts on ecosystems. Yet, TBM projections suffer from large uncertainties that limit their usefulness. A large part of this uncertainty arises from the empirical allometric (size-tomass) relationships that are used to represent forest structure in TBMs. Forest structure actually drives a large part of TBM uncertainty as it regulates key processes such as the transfer of carbon, energy, and water between the land and atmosphere, but remains challenging to measure and reliably represent. The poor representation of forest structure in TBMs results in models that are able to reproduce observed land fluxes, but which fail to realistically represent carbon pools, forest composition, and demography. Recent advances in Terrestrial Laser Scanning (TLS) techniques offer a huge opportunity to capture the three-dimensional structure of the ecosystem and transfer this information to TBMs in order to increase their accuracy. In this study, we quantified the impacts of integrating structural observations of individual trees (namely tree height, leaf area, woody biomass, and crown area) derived from TLS into the state-of-the-art Ecosystem Demography model (ED2.2) at a temperate forest site. We assessed the relative model sensitivity to initial conditions, allometric parameters, and canopy representation by changing them in turn from default configurations to site-specific, TLS-derived values. We show that forest demography and productivity as modelled by ED2.2 are sensitive to the imposed initial state, the model structural parameters, and the way canopy is represented. In particular, we show that: 1) the imposed openness of the canopy dramatically influenced the potential vegetation, the optimal ecosystem leaf area, and the vertical distribution of light in the forest, as simulated by ED2.2; 2) TLS-derived allometric parameters increased simulated leaf area index and aboveground biomass by 57 and 75 %, respectively; 3) the choice of model structure and allometric coefficient both significantly impacted the optimal set of parameters necessary to reproduce eddy covariance flux data.

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“…While studies based on calibrated DVMs have uncovered spatial and temporal variations in forest productivity along large environmental gradients, they have rarely addressed variation in growth rates and the relative importance of environmental growth constraints at fine spatial resolution (~1 km 2 ). This is, in part, because many DVMs have relatively simplistic schemes of disentangling the impact of climatic factors on growth (Sitch et al., 2015), which challenges sub‐seasonal assessments of tree growth and its climatic drivers (Babst et al., 2021).…”

Section: Introductionmentioning

confidence: 99%

Tree growth in Switzerland is increasingly constrained by rising evaporative demand

et al. 2021

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Modeling Ambitions Outpace Observations of Forest Carbon Allocation

Cited by 34 publications

References 72 publications

Adding Tree Rings to North America's National Forest Inventories: An Essential Tool to Guide Drawdown of Atmospheric CO2

Adding Tree Rings to North America's National Forest Inventories: An Essential Tool to Guide Drawdown of Atmospheric CO2

Using terrestrial laser scanning to constrain forest ecosystem structure and functions in the Ecosystem Demography model (ED2.2)

Tree growth in Switzerland is increasingly constrained by rising evaporative demand

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