Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil–plant–atmosphere continuum

Bonan, G. B.; Williams, Mathew; Fisher, Rosie A.; Oleson, Keith W.

doi:10.5194/gmd-7-2193-2014

Cited by 344 publications

(407 citation statements)

References 86 publications

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“…Our results and those of Bonan et al (2014) demonstrate that model performance using the optimisation scheme was comparable to the original empirical stomatal conductance (Ball et al, 1987) scheme. Optimisation of key plant attributes is a viable alternative to empirical or overly complex mechanistic model algorithms (Dewar et al, 2009).…”

Section: Optimisation Theory In Lsmssupporting

confidence: 63%

“…By calibrating parameters to match the existing parameterisation of the original empirical stomatal model (MED-L), we were able to show that the new model structure for stomatal conductance does not degrade overall model performance. This result is similar to that of Bonan et al (2014), who implemented the optimal stomatal conductance scheme into the CLM LSM, following Williams et al (1996). In their implementation they solve the optimisation problem numerically (Eq.…”

Section: Optimisation Theory In Lsmssupporting

confidence: 57%

“…In addition, the behaviour of this model has been widely tested at the leaf scale and it has been shown to perform at least as well, if not better than, the more widespread empirical approaches currently used (Medlyn et al, 2011;De Kauwe et al, 2013a;Duursma et al, 2013;Medlyn et al, 2013;Héroult et al, 2013). We also note that it is possible to implement a numerical solution of this optimisation problem into a LSM (Bonan et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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A test of an optimal stomatal conductance scheme within the CABLE land surface model

et al. 2015

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Abstract. Stomatal conductance (g s ) affects the fluxes of carbon, energy and water between the vegetated land surface and the atmosphere. We test an implementation of an optimal stomatal conductance model within the Community Atmosphere Biosphere Land Exchange (CABLE) land surface model (LSM). In common with many LSMs, CABLE does not differentiate between g s model parameters in relation to plant functional type (PFT), but instead only in relation to photosynthetic pathway. We constrained the key model parameter "g 1 ", which represents plant water use strategy, by PFT, based on a global synthesis of stomatal behaviour. As proof of concept, we also demonstrate that the g 1 parameter can be estimated using two long-term average bioclimatic variables: (i) temperature and (ii) an indirect estimate of annual plant water availability. The new stomatal model, in conjunction with PFT parameterisations, resulted in a large reduction in annual fluxes of transpiration (∼ 30 % compared to the standard CABLE simulations) across evergreen needleleaf, tundra and C4 grass regions. Differences in other regions of the globe were typically small. Model performance against upscaled data products was not degraded, but did not noticeably reduce existing model-data biases. We identified assumptions relating to the coupling of the vegetation to the atmosphere and the parameterisation of the minimum stomatal conductance as areas requiring further investigation in both CABLE and potentially other LSMs.We conclude that optimisation theory can yield a simple and tractable approach to predicting stomatal conductance in LSMs.

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Section: Optimisation Theory In Lsmssupporting

confidence: 63%

Section: Optimisation Theory In Lsmssupporting

confidence: 57%

Section: Introductionmentioning

confidence: 99%

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A test of an optimal stomatal conductance scheme within the CABLE land surface model

et al. 2015

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“…Neither the empirical functions nor the soil moisture stress functions, which are commonly used in landsurface models, fully capture stomatal closure and limitation of C uptake during drought stress (Bonan et al, 2014;Verhoef and Egea, 2014). Therefore, we replaced the soil moisture stress function which limits C assimilation through a constraint on k Vcmax in the ORCHIDEE trunk, with a constraint based on the amount of water plants can transport from the soil to their leaves.…”

Section: Hydraulic Architecturementioning

confidence: 99%

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

et al. 2015

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Abstract. Since 70 % of global forests are managed and forests impact the global carbon cycle and the energy exchange with the overlying atmosphere, forest management has the potential to mitigate climate change. Yet, none of the land-surface models used in Earth system models, and therefore none of today's predictions of future climate, accounts for the interactions between climate and forest management. We addressed this gap in modelling capability by developing and parametrising a version of the ORCHIDEE land-surface model to simulate the biogeochemical and biophysical effects of forest management. The most significant changes between the new branch called ORCHIDEE-CAN (SVN r2290) and the trunk version of ORCHIDEE (SVN r2243) are the allometric-based allocation of carbon to leaf, root, wood, fruit and reserve pools; the transmittance, absorbance and reflectance of radiation within the canopy; and the vertical discretisation of the energy budget calculations. In addition, conceptual changes were introduced towards a better process representation for the interaction of radiation with snow, the hydraulic architecture of plants, the representation of forest management and a numerical solution for the photosynthesis formalism of Farquhar, von Caemmerer and Berry. For consistency reasons, these changes were extensively linked throughout the code. Parametrisation was revisited after introducing 12 new parameter sets that represent specific tree species or genera rather than a group of often distantly related or even unrelated species, as is the case in widely used plant functional types. Performance of the new model was compared against the trunk and validated against independent spatially explicit data for basal area, tree height, canopy structure, gross primary production (GPP), albedo and evapotranspiration over Europe. For all tested variables, Published by Copernicus Publications on behalf of the European Geosciences Union. K. Naudts et al.: A vertically discretised canopy description for ORCHIDEEORCHIDEE-CAN outperformed the trunk regarding its ability to reproduce large-scale spatial patterns as well as their inter-annual variability over Europe. Depending on the data stream, ORCHIDEE-CAN had a 67 to 92 % chance to reproduce the spatial and temporal variability of the validation data.

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“…Several authors chose longer (multi-year) sites (Balsamo et al, 2009;Lawrence et al, 2011;Wang et al, 2011). Some evaluation papers explicitly sought to sample a range of PFTs (Bonan et al, 2014;De Kauwe et al, 2015). Many highlighted choices based on the availability of gap-filled data (Krinner et al, 2005;Slevin et al, 2015;Wang et al, 2011).…”

mentioning

confidence: 99%

Does predictability of fluxes vary between FLUXNET sites?

Haughton¹,

Abramowitz²,

Kauwe³

et al. 2018

Preprint

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Abstract. The FLUXNET dataset contains eddy covariance measurements from across the globe, and represents an invaluable estimate of the fluxes of energy, water and carbon between the land surface and the atmosphere. While there is an expectation that the broad range of site characteristics in FLUXNET result in a diversity of flux behaviour, there has been little exploration of how predictable site behaviour is across the network. Aside from intrinsic interest in this fundamental question, understanding site predictability would be useful for land surface model (LSM) evaluation in setting a priori expectations of model 5 performance. It would also provide a clear rationale for selecting particular FLUXNET sites for model development, evaluation and benchmarking. Here, 155 datasets with 30 minute temporal resolution from the Tier 1 of FLUXNET2015 were analysed in a first attempt to assess individual site predictability. Predictability was defined using the disparity between the ability to simulate fluxes at a site given specific knowledge of the site, and the ability to simulate fluxes given general land surface specifications. We then examined predictability using performance metrics including RMSE, correlation, and probability density 10 overlap, and defined site uniqueness as the disparity between multiple empirical models trained globally and locally for each site. A number of hypotheses potentially explaining site predictability were then tested, including climatology, data quality and site characteristics. We found very few clear predictors of uniqueness across different sites including little evidence that flux behaviour is well discretised by vegetation types. While this result might relate to our definition of uniqueness, we argue that our approach is sound and provides a useful basis for site selection in LSM evaluation.

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Modeling stomatal conductance in the earth system: linking leaf water-use efficiency and water transport along the soil–plant–atmosphere continuum

Cited by 344 publications

References 86 publications

A test of an optimal stomatal conductance scheme within the CABLE land surface model

A test of an optimal stomatal conductance scheme within the CABLE land surface model

A vertically discretised canopy description for ORCHIDEE (SVN r2290) and the modifications to the energy, water and carbon fluxes

Does predictability of fluxes vary between FLUXNET sites?

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