Satellite based estimates underestimate the effect of CO2 fertilization on net primary productivity

Kauwe, Martin G. De; Keenan, Trevor F.; Medlyn, Belinda E.; Prentice, Iain Colin; Terrer, César

doi:10.1038/nclimate3105

Cited by 90 publications

(73 citation statements)

References 19 publications

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“…The effect of CO 2 concentration was found to be of some significance but not a key driver of RUE as found by De Kauwe et al (). This might be due to the fact that we analysed natural variability of CO 2 concentration (overall 380 ± 8 ppm) whereas De Kauwe et al () analysed long‐term FACE forest sites with CO 2 concentrations ranging from 370 to 550 ppm. A high CO 2 concentration may increase the effect of CO 2 on RUE.…”

Section: Discussionsupporting

confidence: 53%

“…In a recent study, Fernández‐Martínez et al () tested the relationship between RUE and N deposition but no significant association was found. Finally, De Kauwe, Keenan, Medlyn, Prentice, and Terrer () have recently shown that CO 2 is a key factor controlling RUE variability. These authors found a large increase in RUE due to elevated CO 2 for two long‐term free air carbon enrichment (FACE) forest sites (Oak Ridge: 1998–2008 and Duke: 1996–2007).…”

Section: Introductionmentioning

confidence: 98%

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Different determinants of radiation use efficiency in cold and temperate forests

Balzarolo

Valdameri

et al. 2019

Global Ecol Biogeogr

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Aim To verify which vegetation and environmental factors are the most important in determining the spatial and temporal variability of average and maximum values of radiation use efficiency (RUEann and RUEmax, respectively) of cold and temperate forests. Location Forty‐eight cold and temperate forests distributed across the Northern Hemisphere. Major taxa studied Evergreen and deciduous trees. Time period 2000–2011. Methods We analysed the impact of 17 factors as potential determinants of mean RUE (at 8 days interval, annual and interannual level) and RUEmax (at annual and interannual level) in cold and temperate forests by using linear regression and random forests models. Results Mean annual RUE (RUEann, c. 1.1 gC/MJ) and RUEmax (c. 0.8 gC/MJ) did not differ between cold and temperate forests. However, for cold forests, RUEann was affected by temperature‐related variables, while for temperate forests RUEann was affected by drought‐related variables. Leaf area index (LAI) was important for both forest types, while N deposition only for cold forests and cloud cover only for temperate forest. RUEmax of cold forests was mainly driven by N deposition and LAI, whereas for temperate forests only a weak relationship between RUEmax and CO2 concentration was found. Short‐term variability of RUE was strongly related to the meteorological variables and varied during the season and was stronger in summer than spring or autumn. Interannual variability of RUEann and RUEmax was only weakly related to the interannual variability of the environmental drivers. Main conclusions Cold and temperate forests show different relationships with the environment and vegetation properties. Among the RUE drivers observed, the least anticipated was N deposition. RUE is strongly related to short‐term and seasonal changes in meteorological variables among seasons and among sites. Our results should be considered in the formulation of climate zone‐specific tools for remote sensing and global models.

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Section: Discussionsupporting

confidence: 53%

Section: Introductionmentioning

confidence: 98%

Different determinants of radiation use efficiency in cold and temperate forests

Balzarolo

Valdameri

et al. 2019

Global Ecol Biogeogr

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“…With N constraint, the simulated global terrestrial GPP decreased by 1.4 Pg C yr −1 in 2015, dampening our expectation for the enhanced CO 2 fertilization. Our result may provide new explanation for the discrepancies between Smith et al () and De Kauwe et al () regarding the large divergence of LUE‐based and ESMs estimates of global terrestrial CO 2 fertilization. Therefore, the consideration of both LUE increase and reduced CO 2 fertilization under N limitation is necessary for accurate projections of future C‐climate feedbacks for different Representative Concentration Pathways.…”

Section: Discussionsupporting

confidence: 50%

Nitrogen Availability Dampens the Positive Impacts of CO₂ Fertilization on Terrestrial Ecosystem Carbon and Water Cycles

Chen

Croft

et al. 2017

Geophysical Research Letters

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The magnitude and variability of the terrestrial CO2 sink remain uncertain, partly due to limited global information on ecosystem nitrogen (N) and its cycle. Without N constraint in ecosystem models, the simulated benefits from CO2 fertilization and CO2‐induced increases in water use efficiency (WUE) may be overestimated. In this study, satellite observations of a relative measure of chlorophyll content are used as a proxy for leaf photosynthetic N content globally for 2003–2011. Global gross primary productivity (GPP) and evapotranspiration are estimated under elevated CO2 and N‐constrained model scenarios. Results suggest that the rate of global GPP increase is overestimated by 85% during 2000–2015 without N limitation. This limitation is found to occur in many tropical and boreal forests, where a negative leaf N trend indicates a reduction in photosynthetic capacity, thereby suppressing the positive vegetation response to enhanced CO2 fertilization. Based on our carbon‐water coupled simulations, enhanced CO2 concentration decreased stomatal conductance and hence increased WUE by 10% globally over the 1982 to 2015 time frame. Due to increased anthropogenic N application, GPP in croplands continues to grow and offset the weak negative trend in forests due to N limitation. Our results also show that the improved WUE is unlikely to ease regional droughts in croplands because of increases in evapotranspiration, which are associated with the enhanced GPP. Although the N limitation on GPP increase is large, its associated confidence interval is still wide, suggesting an urgent need for better understanding and quantification of N limitation from satellite observations.

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“…We note, however, that the ratio of two out of six models including carbon-nutrient interactions in the ISIMIP ensemble is commensurate to other model inter-comparison projects: 3 out of 10 CMIP5 models (Exbrayat et al, 2014) or 2 out of 8 models in the new ISIMIP experiments presented by Chen et al (2017). There is also considerable debate on how good large-scale NPP observational products are de Kauwe et al, 2016), a problem that we address by performing the REA approach three times.…”

Section: Discussionmentioning

confidence: 99%

Reliability ensemble averaging of 21st century projections of terrestrial net primary productivity reduces global and regional uncertainties

et al. 2018

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Abstract. Multi-model averaging techniques provide opportunities to extract additional information from large ensembles of simulations. In particular, present-day model skill can be used to evaluate their potential performance in future climate simulations. Multi-model averaging methods have been used extensively in climate and hydrological sciences, but they have not been used to constrain projected plant productivity responses to climate change, which is a major uncertainty in Earth system modelling. Here, we use three global observationally orientated estimates of current net primary productivity (NPP) to perform a reliability ensemble averaging (REA) method using 30 global simulations of the 21st century change in NPP based on the Inter-Sectoral Impact Model Intercomparison Project (ISIMIP) "business as usual" emissions scenario. We find that the three REA methods support an increase in global NPP by the end of the 21st century (2095-2099) compared to [2001][2002][2003][2004][2005], which is 2-3 % stronger than the ensemble ISIMIP mean value of 24.2 Pg C y −1 . Using REA also leads to a 45-68 % reduction in the global uncertainty of 21st century NPP projection, which strengthens confidence in the resilience of the CO 2 fertilization effect to climate change. This reduction in uncertainty is especially clear for boreal ecosystems although it may be an artefact due to the lack of representation of nutrient limitations on NPP in most models. Conversely, the large uncertainty that remains on the sign of the response of NPP in semi-arid regions points to the need for better observations and model development in these regions.

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Satellite based estimates underestimate the effect of CO2 fertilization on net primary productivity

Cited by 90 publications

References 19 publications

Different determinants of radiation use efficiency in cold and temperate forests

Different determinants of radiation use efficiency in cold and temperate forests

Nitrogen Availability Dampens the Positive Impacts of CO₂ Fertilization on Terrestrial Ecosystem Carbon and Water Cycles

Reliability ensemble averaging of 21st century projections of terrestrial net primary productivity reduces global and regional uncertainties

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Satellite based estimates underestimate the effect of CO2 fertilization on net primary productivity

Cited by 90 publications

References 19 publications

Different determinants of radiation use efficiency in cold and temperate forests

Different determinants of radiation use efficiency in cold and temperate forests

Nitrogen Availability Dampens the Positive Impacts of CO2 Fertilization on Terrestrial Ecosystem Carbon and Water Cycles

Reliability ensemble averaging of 21st century projections of terrestrial net primary productivity reduces global and regional uncertainties

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Nitrogen Availability Dampens the Positive Impacts of CO₂ Fertilization on Terrestrial Ecosystem Carbon and Water Cycles