Increased light‐use efficiency in northern terrestrial ecosystems indicated by CO<sub>2</sub> and greening observations

Thomas, Rebecca T.; Prentice, Iain Colin; Graven, Heather; Ciais, Philippe; Fisher, Joshua B.; Hayes, D. J.; Huang, Maoyi; Huntzinger, D. N.; Ito, Akihiko; Jain, Atul K.; Mao, Jiafu; Michalak, A. M.; Peng, Shushi; Poulter, Benjamin; Ricciuto, Daniel M.; Shi, Xiaoying; Schwalm, Christopher R.; Tian, Hanqin; Zeng, Ning

doi:10.1002/2016gl070710

Cited by 50 publications

(60 citation statements)

References 73 publications

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“…DGVMs tend to simulate a slower increase in CO

_{2}

uptake than reported by inversions in several regions and globally. The weak negative trend in

D_{G l o b e}

is consistent with studies showing that DGVMs may underestimate the response of vegetation to the effect of CO

_{2}

fertilization (Fernndez‐Martnez et al, ; Thomas et al, ), or the effect of N deposition in Asia (Liu et al, ), or forest regrowth (Pugh et al, ). The positive values for the trend in EU, KAJ, and SEAS indicate that DGVMs show a stronger long‐term increase in the land sink compared to inversions.…”

Section: Discussionsupporting

confidence: 84%

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates

Bastos

O’Sullivan

Ciais

et al. 2020

Global Biogeochemical Cycles

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The Global Carbon Budget 2018 (GCB2018) estimated by the atmospheric CO 2 growth rate, fossil fuel emissions, and modeled (bottom‐up) land and ocean fluxes cannot be fully closed, leading to a “budget imbalance,” highlighting uncertainties in GCB components. However, no systematic analysis has been performed on which regions or processes contribute to this term. To obtain deeper insight on the sources of uncertainty in global and regional carbon budgets, we analyzed differences in Net Biome Productivity (NBP) for all possible combinations of bottom‐up and top‐down data sets in GCB2018: (i) 16 dynamic global vegetation models (DGVMs), and (ii) 5 atmospheric inversions that match the atmospheric CO 2 growth rate. We find that the global mismatch between the two ensembles matches well the GCB2018 budget imbalance, with Brazil, Southeast Asia, and Oceania as the largest contributors. Differences between DGVMs dominate global mismatches, while at regional scale differences between inversions contribute the most to uncertainty. At both global and regional scales, disagreement on NBP interannual variability between the two approaches explains a large fraction of differences. We attribute this mismatch to distinct responses to El Niño–Southern Oscillation variability between DGVMs and inversions and to uncertainties in land use change emissions, especially in South America and Southeast Asia. We identify key needs to reduce uncertainty in carbon budgets: reducing uncertainty in atmospheric inversions (e.g., through more observations in the tropics) and in land use change fluxes, including more land use processes and evaluating land use transitions (e.g., using high‐resolution remote‐sensing), and, finally, improving tropical hydroecological processes and fire representation within DGVMs.

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“…DGVMs tend to simulate a slower increase in CO

_{2}

uptake than reported by inversions in several regions and globally. The weak negative trend in

D_{G l o b e}

is consistent with studies showing that DGVMs may underestimate the response of vegetation to the effect of CO

_{2}

Section: Discussionsupporting

confidence: 84%

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates

Bastos

O’Sullivan

Ciais

et al. 2020

Global Biogeochemical Cycles

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“…In other words, earlier start of growing season is highly linked to earlier onset of peak of season and higher NDVI (Table 1). We suggest that the ESMs are capturing the increasing maximum annual GPP and NEP through CO 2 fertilization, the effect of CO 2 on light use efficiency and climate-driven increases in photosynthesis (Thomas et al, 2016). We suggest that the ESMs are capturing the increasing maximum annual GPP and NEP through CO 2 fertilization, the effect of CO 2 on light use efficiency and climate-driven increases in photosynthesis (Thomas et al, 2016).…”

Section: Impact Of Shifting Peak Season Plant Activity On Vegetatiomentioning

confidence: 85%

Peak season plant activity shift towards spring is reflected by increasing carbon uptake by extratropical ecosystems

Gonsamo

Chen

Ooi

2017

Global Change Biology

116

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Climate change is lengthening the growing season of the Northern Hemisphere extratropical terrestrial ecosystems, but little is known regarding the timing and dynamics of the peak season of plant activity. Here, we use 34-year satellite normalized difference vegetation index (NDVI) observations and atmospheric CO concentration and δ C isotope measurements at Point Barrow (Alaska, USA, 71°N) to study the dynamics of the peak of season (POS) of plant activity. Averaged across extratropical (>23°N) non-evergreen-dominated pixels, NDVI data show that the POS has advanced by 1.2 ± 0.6 days per decade in response to the spring-ward shifts of the start (1.0 ± 0.8 days per decade) and end (1.5 ± 1.0 days per decade) of peak activity, and the earlier onset of the start of growing season (1.4 ± 0.8 days per decade), while POS maximum NDVI value increased by 7.8 ± 1.8% for 1982-2015. Similarly, the peak day of carbon uptake, based on calculations from atmospheric CO concentration and δ C data, is advancing by 2.5 ± 2.6 and 4.3 ± 2.9 days per decade, respectively. POS maximum NDVI value shows strong negative relationships (p < .01) with the earlier onset of the start of growing season and POS days. Given that the maximum solar irradiance and day length occur before the average POS day, the earlier occurrence of peak plant activity results in increased plant productivity. Both the advancing POS day and increasing POS vegetation greenness are consistent with the shifting peak productivity towards spring and the increasing annual maximum values of gross and net ecosystem productivity simulated by coupled Earth system models. Our results further indicate that the decline in autumn NDVI is contributing the most to the overall browning of the northern high latitudes (>50°N) since 2011. The spring-ward shift of peak season plant activity is expected to disrupt the synchrony of biotic interaction and exert strong biophysical feedbacks on climate by modifying the surface albedo and energy budget.

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“…Based on modeling, Thomas et al (2016) showed that LUE has increased in high northern latitudes over the last 50 years. Based on modeling, Thomas et al (2016) showed that LUE has increased in high northern latitudes over the last 50 years.…”

Section: Light Use Efficiencymentioning

confidence: 99%

“…Some have reported an increase in the RUE in relation to increasing CO 2 concentration (Keenan et al, 2013;Thomas et al, 2016), while others reported a decrease in the RUE (Tang et al, 2014;Zhang et al, 2014). Some have reported an increase in the RUE in relation to increasing CO 2 concentration (Keenan et al, 2013;Thomas et al, 2016), while others reported a decrease in the RUE (Tang et al, 2014;Zhang et al, 2014).…”

Section: Introductionmentioning

confidence: 99%

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Divergent long‐term trends and interannual variation in ecosystem resource use efficiencies of a southern boreal old black spruce forest 1999–2017

Liu

Black

Jassal

et al. 2019

Global Change Biology

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Long‐term trends in ecosystem resource use efficiencies (RUEs) and their controlling factors are key pieces of information for understanding how an ecosystem responds to climate change. We used continuous eddy covariance and microclimate data over the period 1999–2017 from a 120‐year‐old black spruce stand in central Saskatchewan, Canada, to assess interannual variability, long‐term trends, and key controlling factors of gross ecosystem production (GEP) and the RUEs of carbon (CUE = net primary production [NPP]/GEP), light (LUE = GEP/absorbed photosynthetic radiation [APAR]), and water (WUE = GEP/evapotranspiration [E]). At this site, annual GEP has shown an increasing trend over the 19 years (p < 0.01), which may be attributed to rising atmospheric CO2 concentration. Interannual variability in GEP, aside from its increasing trend, was most strongly related to spring temperatures. Associated with the significant increase in annual GEP were relatively small changes in NPP, APAR, and E, so that annual CUE showed a decreasing trend and annual LUE and WUE showed increasing trends over the 19 years. The long‐term trends in the RUEs were related to the increasing CO2 concentration. Further analysis of detrended RUEs showed that their interannual variation was impacted most strongly by air temperature. Two‐factor linear models combining CO2 concentration and air temperature performed well (R2~0.60) in simulating annual RUEs. LUE and WUE were positively correlated both annually and seasonally, while LUE and CUE were mostly negatively correlated. Our results showed divergent long‐term trends among CUE, LUE, and WUE and highlighted the need to account for the combined effects of climatic controls and the ‘CO2 fertilization effect’ on long‐term variations in RUEs. Since most RUE‐based models rely primarily on one resource limitation, the observed patterns of relative change among the three RUEs may have important implications for RUE‐based modeling of C fluxes.

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Increased light‐use efficiency in northern terrestrial ecosystems indicated by CO₂ and greening observations

Cited by 50 publications

References 73 publications

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates

Peak season plant activity shift towards spring is reflected by increasing carbon uptake by extratropical ecosystems

Divergent long‐term trends and interannual variation in ecosystem resource use efficiencies of a southern boreal old black spruce forest 1999–2017

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Increased light‐use efficiency in northern terrestrial ecosystems indicated by CO2 and greening observations

Cited by 50 publications

References 73 publications

Sources of Uncertainty in Regional and Global Terrestrial CO2 Exchange Estimates

Sources of Uncertainty in Regional and Global Terrestrial CO2 Exchange Estimates

Peak season plant activity shift towards spring is reflected by increasing carbon uptake by extratropical ecosystems

Divergent long‐term trends and interannual variation in ecosystem resource use efficiencies of a southern boreal old black spruce forest 1999–2017

Contact Info

Product

Resources

About

Increased light‐use efficiency in northern terrestrial ecosystems indicated by CO₂ and greening observations

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates

Sources of Uncertainty in Regional and Global Terrestrial CO₂ Exchange Estimates