Soil water stress and coupled photosynthesis–conductance models: Bridging the gap between conflicting reports on the relative roles of stomatal, mesophyll conductance and biochemical limitations to photosynthesis

Keenan, Trevor F.; Sabaté, Santiago; Gracia, Carlos

doi:10.1016/j.agrformet.2010.01.008

Cited by 140 publications

(127 citation statements)

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“…Moreover, inclusion of non-stomatal limitations on photosynthesis during drought, e.g. reduced mesophyll conductance or carboxylation capacity, may additionally improve the model results (Keenan et al, 2010).…”

Section: Discussionmentioning

confidence: 99%

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Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

et al. 2017

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Abstract. The influence of drought on plant functioning has received considerable attention in recent years, however our understanding of the response of carbon and water coupling to drought in terrestrial ecosystems still needs to be improved. A severe soil moisture drought occurred in southern Finland in the late summer of 2006. In this study, we investigated the response of water use efficiency to summer drought in a boreal Scots pine forest (Pinus sylvestris) on the daily time scale mainly using eddy covariance flux data from the Hyytiälä (southern Finland) flux site. In addition, simulation results from the JSBACH land surface model were evaluated against the observed results. Based on observed data, the ecosystem level water use efficiency (EWUE; the ratio of gross primary production, GPP, to evapotranspiration, ET) showed a decrease during the severe soil moisture drought, while the inherent water use efficiency (IWUE; a quantity defined as EWUE multiplied with mean daytime vapour pressure deficit, VPD) increased and the underlying water use efficiency (uWUE, a metric based on IWUE and a simple stomatal model, is the ratio of GPP multiplied with a square root of VPD to ET) was unchanged during the drought. The decrease in EWUE was due to the stronger decline in GPP than in ET. The increase in IWUE was because of the decreased stomatal conductance under increased VPD. The unchanged uWUE indicates that the trade-off between carbon assimilation and transpiration of the boreal Scots pine forest was not disturbed by this drought event at the site. The JS-BACH simulation showed declines of both GPP and ET under the severe soil moisture drought, but to a smaller extent compared to the observed GPP and ET. Simulated GPP and ET led to a smaller decrease in EWUE but a larger increase in IWUE because of the severe soil moisture drought in comparison to observations. As in the observations, the simulated uWUE showed no changes in the drought event. The model deficiencies exist mainly due to the lack of the limiting effect of increased VPD on stomatal conductance during the low soil moisture condition. Our study provides a deeper understanding of the coupling of carbon and water cycles in the boreal Scots pine forest ecosystem and suggests possible improvements to land surface models, which play an important role in the prediction of biosphere-atmosphere feedbacks in the climate system.

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Section: Discussionmentioning

confidence: 99%

“…WUE can be used to study ecosystem functioning which is in close connection to the global cycles of water, energy, and carbon (Keenan et al, 2013). With the use of the eddy covariance technique (EC) and associated data processing, i.e.…”

Section: Introductionmentioning

confidence: 99%

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

et al. 2017

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“…Phenology is temperature-dependent and accounted for in an updated version of the Pelkonen & Hari (1980) approach for calculating the seasonal variations in photosynthetic potential. GOTILWA 1 has been validated and widely applied both in the Mediterranean region and the rest of Europe (see Kramer et al, 2002;Morales et al, 2005;Keenan et al, 2009a for validation exercises and Keenan et al, 2009bKeenan et al, , c, 2010 for example applications).…”

Section: Mars (Multivariate Adaptive Regression Splines)mentioning

confidence: 99%

Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!

Keenan

Serra

Lloret

et al. 2010

Global Change Biology

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Assessing the potential future of current forest stands is a key to design conservation strategies and understanding potential future impacts to ecosystem service supplies. This is particularly true in the Mediterranean basin, where important future climatic changes are expected. Here, we assess and compare two commonly used modeling approaches (niche-and process-based models) to project the future of current stands of three forest species with contrasting distributions, using regionalized climate for continental Spain. Results highlight variability in model ability to estimate current distributions, and the inherent large uncertainty involved in making projections into the future. CO 2 fertilization through projected increased atmospheric CO 2 concentrations is shown to increase forest productivity in the mechanistic process-based model (despite increased drought stress) by up to three times that of the non-CO 2 fertilization scenario by the period 2050-2080, which is in stark contrast to projections of reduced habitat suitability from the niche-based models by the same period. This highlights the importance of introducing aspects of plant biogeochemistry into current niche-based models for a realistic projection of future species distributions. We conclude that the future of current Mediterranean forest stands is highly uncertain and suggest that a new synergy between niche-and process-based models is urgently needed in order to improve our predictive ability.

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“…3.4a as the point where we enter a very weakly coupled regime for CO 2 in the ABL. We note that this threshold shifts towards very low values of SMI if C β (and thus β) increases in our analysis, and a similar effect occurs if we apply the linear β function on the mesophyll conductance instead of on the gross primary production, as done by Calvet et al (1998) and as suggested by Keenan et al (2010a) (not shown here). This will be discussed further in Sect.…”

Section: Coupling Pointsmentioning

confidence: 60%

“…Several studies (Egea et al, 2011;Keenan et al, 2010a;Calvet et al, 1998) have suggested that in addition to downregulation of stomatal conductance, the mesophyll conductance and/or the maximum carboxylation rate should also be downregulated. The latter would account for non-stomatal effects, such as the decline in leaf nitrogen content (Grassi and Magnani, 2005) and the hardening of mesophyll cell walls (Keenan et al, 2010b).…”

Section: Discussionmentioning

confidence: 99%

Modeling the coupled exchange of water and CO2 over croplands

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Soil water stress and coupled photosynthesis–conductance models: Bridging the gap between conflicting reports on the relative roles of stomatal, mesophyll conductance and biochemical limitations to photosynthesis

Cited by 140 publications

References 100 publications

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

Response of water use efficiency to summer drought in a boreal Scots pine forest in Finland

Predicting the future of forests in the Mediterranean under climate change, with niche- and process-based models: CO2 matters!

Modeling the coupled exchange of water and CO2 over croplands

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