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Cited by 355Paleontology and Stratigraphy of FossilsEarth Systems and Cosmic EvolutionGeological and Geochemical Analysis

Earliest land plants created modern levels of atmospheric oxygen

Open access
Lenton, Timothy M., Dahl, Tais W., Daines, Stuart J., Mills, Benjamin J. W., Ozaki, Kazumi, Saltzman, Matthew R., Porada, Philipp·2016·Proceedings of the National Academy of Sciences
DOI 10.1073/pnas.1604787113PMC PMC5024600
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Abstract

Significance: The rise of atmospheric oxygen over Earth’s history has received much recent interdisciplinary attention. However, the puzzle of when and how atmospheric oxygen reached modern levels remains unresolved. Many recent studies have argued for a major oxygenation event—of uncertain cause—in the Neoproterozoic Era >541 Ma, enabling the rise of animals. Previous modelling work has predicted a late Paleozoic oxygen rise (<380 Ma) due to the rise of forests. Here we show that neither scenario is correct. Instead, the earliest plants, which colonized the land from 470 Ma onward, first increased atmospheric oxygen to present levels by 400 Ma, and this instigated fire-mediated feedbacks that have stabilized high oxygen levels ever since, shaping subsequent evolution.

AI snapshot

Written from the paper’s full text.

TL;DR

The paper argues that the earliest land plants, colonizing from ∼470 Ma, drove a mid-Paleozoic oxygenation event by increasing organic carbon burial, raising atmospheric O₂ to present levels by 420–400 Ma. It uses a revised COPSE biogeochemical model plus a trait-based cryptogamic vegetation model and bryophyte C/P data to reproduce a sustained +2‰ δ¹³C shift and O₂ rise consistent with charcoal and redox proxies.

Key findings

  • Earliest nonvascular plants colonized land from ∼470–445 Ma; the model reproduces a sustained +2‰ δ¹³C increase by ∼445 Ma and an O₂ rise to present levels by 420–400 Ma, consistent with fossil charcoal indicating O₂ >15–17% by 420–400 Ma and Mo isotope evidence for deep-ocean oxygenation at 435–392 Ma.
  • A trait-based ecophysiological model predicts cryptogamic vegetation cover at 445 Ma (CO₂ = 8 PAL, O₂ = 0.6 PAL) could achieve global NPP = 18.7 GtC·y⁻¹, ∼30% of today; COPSE with stronger Late Ordovician colonization predicts 30–40% of today’s NPP.
  • Bryophyte C/P literature ranges from 800 to 4,300 (mean ∼1,900); assuming C/P = 2,000 vs 1,000 increases modeled organic carbon burial by ∼50% vs ∼25%, δ¹³C by +1.1‰ vs +0.5‰, and O₂ by +0.27 vs +0.11 PAL.
  • Reproducing the observed +2‰ δ¹³C shift requires selective P weathering: a 50% increase in P weathering with C/P = 1,000 gives burial ∼95%, δ¹³C +2.2‰, and O₂ +0.74 PAL (to 0.97 PAL at 417 Ma); a 25% increase with C/P = 2,000 gives burial ∼90%, δ¹³C +2.1‰, and O₂ +0.67 PAL; P weathering spikes with C/P = 2,000 peak at O₂ +0.72 PAL at 407 Ma.

Methods

  • Revised COPSE biogeochemical model for coupled C, O, N, P, and S cycles and δ¹³C, with biological forcing factors: evolution/colonization (E), weathering enhancement (W), selective phosphorus weathering (F), and terrestrial C/P burial ratio (CP); sensitivity analyses varied geologic forcing and initial conditions.
  • Trait-based spatial model of cryptogamic vegetation (bryophyte and lichen) driven by Late Ordovician (445 Ma) climate simulations at different atmospheric CO₂ and O₂; assumed CO₂ = 8 PAL, O₂ = 0.6 PAL, and no ice sheet mask to predict global NPP.
  • Data compilation included the early charcoal record, molybdenum isotope record, carbonate δ¹³C spline fit, and bryophyte C/P ratios; experimental P weathering calculation used granite with the moss *Physcomitrella patens*.

Limitations

  • Stated: direct evidence linking a phase of land colonization to enhanced weathering and a positive δ¹³C excursion is only established for the Silurian–Devonian boundary; alternative hypotheses for short-lived positive δ¹³C excursions should also be considered.
  • Stated: the model does not capture the earlier Late Ordovician–Early Silurian δ³⁴S rise from ∼25 to ∼30‰; other processes not yet included warrant future consideration, such as the effect of increasing atmospheric mass on climate and effects on δ⁷Li and ⁸⁷Sr/⁸⁶Sr.
  • Evident: P weathering amplification estimates are dominated by the unmeasured P content of biomass, though the factor must be >5.3; the hypothesis requires early plants to have been much more productive and globally extensive than previously assumed.

Model-written summary. Check it against the paper before relying on it.

Integrity signals

Registry

Crossref · 10.1073/pnas.1604787113

Cites

90 of 90 references verified0 citation errors · 0 not checkable

Statistics

Nothing to recompute.

Claims the paper makes

0 of 56 cited sources checked · 0 supported · 0 flagged

  • Findingown data
    § Earliest land plants created modern levels of atmospheric oxygen

    Early plant material had a much higher molar C:P ratio (∼2,000) than marine biomass (∼100).

    “Data from modern bryophytes suggests this plentiful early plant material had a much higher molar C:P ratio ( ∼ 2,000) than marine biomass ( ∼ 100)”
    Quote in the paperSubstantial claim
  • Findingcitation
    § Results and Discussion

    The original baseline COPSE model predicts early Paleozoic O2 ∼0.23 PAL at 445 Ma, supported by an organic carbon burial flux of ∼4×10^12 mol·y-1 with δ13C = 0.03‰.

    “The original baseline model (10) predicts early Paleozoic O2 ∼ 0.23 PAL at a reference time of 445 Ma, supported by an organic carbon burial flux of ∼ 4 × 10 12 mol · y -1 (about half the present-day value) with δ 13 C = 0.03 ‰ .”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] source

      Not checked in the free run.

  • Findingreasoning
    § Earliest land plants created modern levels of atmospheric oxygen

    Combining these effects in a model of long-term biogeochemical cycling reproduces a sustained +2‰ increase in the carbonate carbon isotope (δ13C) record by ∼445 Ma.

    “Combining these effects in a model of long-term biogeochemical cycling, we reproduce a sustained + 2 ‰ increase in the carbonate carbon isotope ( δ 13 C) record by ∼ 445 Ma”
    Quote in the paperSubstantial claim
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.
  • Findingreasoning
    § Earliest land plants created modern levels of atmospheric oxygen

    The model predicts a corresponding rise in O2 to present levels by 420-400 Ma.

    “and predict a corresponding rise in O2 to present levels by 420 -400 Ma, consistent with geochemical data.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
  • Findingown data
    § Earliest land plants created modern levels of atmospheric oxygen

    Cryptogamic vegetation cover could have achieved ∼30% of today's global terrestrial net primary productivity by ∼445 Ma.

    “We use a trait-based ecophysiological model to predict that cryptogamic vegetation cover could have achieved ∼ 30% of today ' s global terrestrial net primary productivity by ∼ 445 Ma.”
    Quote in the paperSubstantial claim
  • May combine two claims. 33
  • Classified as probably not a substantial claim. 14

  • May combine two claims.

    Findingreasoning
    § Results and Discussion

    If buried early plant matter had C/P = 2,000, then even with no effect on weathering fluxes, this increases global organic carbon burial by ∼50%, δ13C by 1.1‰, and atmospheric O2 by 0.27 PAL.

    “If instead we assume that buried early plant matter had C/P = 2,000, then given their productivity, even with no effect on weathering fluxes, this increases global organic carbon burial by ∼ 50%, δ 13 C by 1.1 ‰ , and atmospheric O2 by 0.27 PAL (Fig. 3, cyan).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • May combine two claims.

    Findingcitation
    § Results and Discussion

    In the original COPSE model, predicted NPP only reaches ∼5% of today's value in the Late Ordovician and Silurian, but with a stronger Late Ordovician phase of land colonization, COPSE predicts global NPP 30-40% of today.

    “In the original COPSE model (10), predicted NPP only reaches ∼ 5% of today ' s value in the Late Ordovician and Silurian, but when we assume a stronger Late Ordovician phase of land colonization by nonvascular plants (following ref. 20; SI Materials and Methods ), then COPSE predicts global NPP 30 -40% of today (Fig. 3 A ), consistent with the detailed spatial model.”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [10] source

      Not checked in the free run.

    • cites [20] Lenton TM, Crouch M, Johnson M, Pires N, Dolan L (2012) First plants cooled the Ordovician. Nat Geosci 5(2):86 -89. source

      Not checked in the free run.

  • May combine two claims.

    Findingcitation
    § Results and Discussion

    Including an effect of early plants on silicate weathering with C/P = 1,000 increases organic carbon burial by ∼35%, δ13C by 0.7‰, and O2 by 0.18 PAL.

    “If we include in COPSE an effect of early plants on silicate weathering following ref. 20, assuming C/P = 1,000, this increases organic carbon burial by ∼ 35%, δ 13 C by 0.7 ‰ , and O2 by 0.18 PAL (Fig. 3, magenta).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Lenton TM, Crouch M, Johnson M, Pires N, Dolan L (2012) First plants cooled the Ordovician. Nat Geosci 5(2):86 -89. source

      Not checked in the free run.

    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • May combine two claims.

    Findingown data
    § Results and Discussion

    In COPSE, early land plants alone, with no effect on weathering fluxes and C/P = 1,000, increase total organic carbon burial by ∼25%, δ13C by 0.5‰, and atmospheric O2 by 0.11 PAL.

    “In COPSE, this advent of early land plants alone, with no assumed effect on weathering fluxes, and assumed C/P = 1,000, increases total organic carbon burial by ∼ 25%, δ 13 C by 0.5 ‰ , and atmospheric O2 by 0.11 PAL (Fig. 3, blue).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • May combine two claims.

    Findingcitation
    § Results and Discussion

    We estimate much higher global NPP and weathering potential than previous arguments.

    “However, we estimate much higher global NPP (Fig. 2) and weathering potential (32).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [32] Porada P, et al. (2016) High potential for weathering and climate effects of nonvascular vegetation in the Late Ordovician. Nat Commun , 10.1038/ncomms12113. source

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § Results and Discussion

    Predicted NPP is sensitive to variations in CO2, climate, ice sheet cover, and O2, but is consistently higher than the 4.3 GtC·y-1 estimated elsewhere.

    “Predicted NPP is sensitive to variations in CO2 and climate (Fig. S1), ice sheet cover (Fig. S2), and O 2 (Table S2), but is consistently higher than the 4.3 GtC · y -1 (7% of today) estimated elsewhere (33).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [33] Edwards D, Cherns L, Raven JA (2015) Could land-based early photosynthesizing ecosystems have bioengineered the planet in mid-Palaeozoic times? Palaeontology 58(5): 803 -837. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Findingown data
    § Materials and Methods

    The mean moss biomass in the biotic microcosms was 14.390 mg.

    “The mean moss biomass in the biotic microcosms was 14.390 mg”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Findingreasoning
    § Results and Discussion

    Assuming early plants caused a sustained 50% increase in phosphorus weathering relative to bulk rock dissolution, with C/P = 1,000, increases total organic carbon burial by ∼95%, δ13C by 2.2‰, and O2 by 0.74 PAL (to 0.97 PAL at 417 Ma).

    “Assuming that early plants caused a sustained 50% increase in phosphorus weathering relative to bulk rock dissolution, with C/P = 1,000, increases total organic carbon burial by ∼ 95%, δ 13 C by 2.2 ‰ , and O2 by 0.74 PAL (to 0.97 PAL at 417 Ma; Fig. 3, yellow).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • May combine two claims.

    Findingown data
    § Results and Discussion

    Varying the uplift and degassing forcing within plausible bounds only causes ±0.08 PAL variation in O2 about the initial state, although it causes the effect of the same early plant forcing scenario to range over +0.4 to 1.0 PAL O2.

    “Varying the uplift and degassing forcing of the model within plausible bounds only causes ± 0.08 PAL variation in O2 about the initial state (Fig. S4), although it does cause the effect of the same early plant forcing scenario to range over + 0.4 to 1.0 PAL O2 (Table S4).”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingcitation
    § Materials and Methods

    The relatively high global NPP results obtained are consistent with present-day cryptogamic covers providing ∼7% of global NPP, despite making up only 1% of terrestrial vegetation by mass and being restricted to relatively resource-poor habitats, while also operating in an atmosphere with a low CO2/O2 ratio.

    “The relatively high global NPP results obtained are consistent with present-day cryptogamic covers providing ∼ 7% of global NPP, despite making up only 1% of terrestrial vegetation by mass (90) and being restricted to relatively resource-poor habitats, while also operating in an atmosphere with a low CO2/O2 ratio.”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [90] Elbert W, et al. (2012) Contribution of cryptogamic covers to the global cycles of carbon and nitrogen. Nat Geosci 5(7):459 -462. source

      Not checked in the free run.

  • May combine two claims.

    Findingown data
    § Results and Discussion

    The model predicts a decline in pyrite sulfur burial and associated drop in δ34S and increases in seawater SO4 concentration and C/S burial ratio with the rise of the earliest plants.

    “Our model makes additional predictions that can be tested against geochemical data -notably, it predicts a decline in pyrite sulfur burial and associated drop in δ 34 S and increases in seawater SO4 concentration and C/S burial ratio with the rise of the earliest plants (Fig. S5).”
    Quote in the paperNot a substantial claim

  • Classified as probably not a substantial claim. May combine two claims.

    Findingown data
    § Results and Discussion

    Assuming buried early plant matter had C/P = 2,000 causes larger increases in total organic carbon burial ∼60%, δ13C +1.2‰, and atmospheric O2 +0.35 PAL.

    “Assuming that buried early plant matter had a higher C/P = 2,000 causes larger increases in total organic carbon burial ∼ 60%, δ 13 C + 1.2 ‰ , and atmospheric O2 + 0.35 PAL (Fig. 3, green).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Findingown data
    § Materials and Methods

    The amplification factors for Ca and Mg from granite are 1.4 and 1.5, respectively.

    “the amplification factors for Ca = 1.4 and Mg = 1.5 from granite”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Findingcitation
    § Results and Discussion

    Including an additional negative feedback on O2 from increased marine organic C/P burial ratios under anoxic waters increases its initial early Paleozoic level to 0.54 PAL and reduces the effect of the same biological forcing scenarios on O2 by ∼10-30%, giving a maximum increase of +0.63 PAL.

    “Including an additional negative feedback on O2, from increased marine organic C/P burial ratios under anoxic waters (37), increases its initial early Paleozoic level to 0.54 PAL and reduces the effect of the same biological forcing scenarios on O2 by ∼ 10 -30%, giving a maximum increase of + 0.63 PAL (Table S5).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [37] Van Cappellen P, Ingall ED (1996) Redox stabilization of the atmosphere and oceans by phosphorus-limited marine productivity. Science 271:493 -496. source

      Not checked in the free run.

  • Classified as probably not a substantial claim. May combine two claims.

    Findingnone given
    § Results and Discussion

    Assuming a sustained 25% increase in phosphorus weathering relative to bulk rock and C/P = 2,000 increases organic carbon burial by ∼90%, δ13C by 2.1‰, and O2 by 0.67 PAL.

    “Assuming a sustained 25% increase in phosphorus weathering relative to bulk rock and C/P = 2,000 increases organic carbon burial by ∼ 90%, δ 13 C by 2.1 ‰ , and O2 by 0.67 PAL (Fig. 3, red).”
    Quote in the paperSubstantial claim
    • Rests on an assumption: The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.
    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • Classified as probably not a substantial claim. May combine two claims.

    Findingreasoning
    § Materials and Methods

    Assuming 0.43 gC/g biomass and C/P = 2,000, the moss biomass corresponds to 0.26 μmol P in biomass; for C/P = 1,000-4,000, it corresponds to 0.13-0.52 μmol P.

    “which assuming 0.43 gC/g biomass and C/P = 2,000 (Table S3) suggests 0.26 μ mol P in biomass, or for C/P = 1,000 -4,000, 0.13 -0.52 μ mol P in biomass”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Results and Discussion

    Subsequent experiments with the liverwort Marchantia paleacea found a 2.5- to 7-fold amplification of Ca weathering and a 9- to 13-fold amplification of P weathering from basalt.

    “Subsequent experiments (21) with the modern liverwort Marchantia paleacea found a 2.5- to 7-fold amplification of Ca weathering and a 9- to 13-fold amplification of P weathering from basalt.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [21] Quirk J, et al. (2015) Constraining the role of early land plants in Palaeozoic weathering and global cooling. Proc Biol Sci , 10.1098/rspb.2015.1115.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Results and Discussion

    Early Devonian coaly shales indicate extensive peatlands 410-400 Ma and have C/N of 44-119, comparable to modern peatlands where C/P ratios tend to increase with depth to C/P >3,000.

    “Furthermore, Early Devonian coaly shales indicate extensive peatlands 410 -400 Ma and have C/N of 44 -119 (28), comparable to that in modern peatlands where N/P and C/P ratios tend to increase with depth to C/P &gt; 3,000 (34).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [28] Kennedy KL, et al. (2013) Lower Devonian coaly shales of northern New Brunswick, Canada: Plant accumulations in the early stages of Terrestrial colonization. J Sediment Res 83(12):1202 -1215. source

      Not checked in the free run.

    • cites [34] Wang M, Moore TR, Talbot J, Richard PJH (2014) The cascade of C:N:P stoichiometry in an ombrotrophic peatland: from plants to peat. Environ Res Lett 9(2):024003. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S2 (checkable).

    Interpretationreasoning
    § Earliest land plants created modern levels of atmospheric oxygen

    The evolution of land plants is the obvious candidate for the permanent shift.

    “The evolution of land plants is the obvious candidate”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationown data
    § Significance

    Neither the Neoproterozoic oxygenation event nor the late Paleozoic oxygen rise due to forests is correct.

    “Here we show that neither scenario is correct.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Significance

    Plants and their associated mycorrhizal fungi can increase phosphorus weathering, and this could be sustained on longer timescales if they preferentially weather phosphorus relative to alkalinity.

    “However, plants and their associated mycorrhizal fungi can increase phosphorus weathering (20 -22), and this could be sustained on longer timescales if they preferentially weather phosphorus relative to alkalinity.”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [20] Lenton TM, Crouch M, Johnson M, Pires N, Dolan L (2012) First plants cooled the Ordovician. Nat Geosci 5(2):86 -89. source

      Not checked in the free run.

    • cites [21] Quirk J, et al. (2015) Constraining the role of early land plants in Palaeozoic weathering and global cooling. Proc Biol Sci , 10.1098/rspb.2015.1115.

      Not checked in the free run.

    • cites [22] Lenton TM, Watson AJ (2000b) Redfield revisited: 2. What regulates the oxygen content of the atmosphere? Global Biogeochem Cycles 14(1):249 -268. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Earliest land plants created modern levels of atmospheric oxygen

    The COPSE model predicts Early Paleozoic pO2 ∼0.2-0.5 PAL, consistent with redox proxy data, but does not predict a rise in oxygen until the advent of forests starting ∼385 Ma, which is too late to explain geochemical changes before ∼390 Ma.

    “The COPSE model we adapt here (10) predicts Early Paleozoic pO2 ∼ 0.2 -0.5 PAL consistent with redox proxy data but, like the other models (7, 8), it does not predict a rise in oxygen until the advent of forests starting ∼ 385 Ma, and continuing until ∼ 300 Ma, which is too late to explain marked changes in geochemical data that occur before ∼ 390 Ma (Fig. 1).”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [10] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationcitation
    § Significance

    Earlier plants developed peatlands and had rock-weathering capabilities, so they could also have affected the global carbon cycle.

    “Given that earlier plants developed peatlands (28), and had rock-weathering capabilities (20, 21), they could also have affected the global carbon cycle (18, 20).”
    Quote in the paperSubstantial claim0 of 3 sources checked
    • cites [28] Kennedy KL, et al. (2013) Lower Devonian coaly shales of northern New Brunswick, Canada: Plant accumulations in the early stages of Terrestrial colonization. J Sediment Res 83(12):1202 -1215. source

      Not checked in the free run.

    • cites [20] Lenton TM, Crouch M, Johnson M, Pires N, Dolan L (2012) First plants cooled the Ordovician. Nat Geosci 5(2):86 -89. source

      Not checked in the free run.

    • cites [21] Quirk J, et al. (2015) Constraining the role of early land plants in Palaeozoic weathering and global cooling. Proc Biol Sci , 10.1098/rspb.2015.1115.

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Earliest land plants created modern levels of atmospheric oxygen

    The long-term mean δ13C remains ∼2‰ throughout the rest of the Paleozoic, Mesozoic, and Early Cenozoic, indicating a sustained increase in global organic carbon burial.

    “Though there are many subsequent δ 13 C fluctuations, including drops back to 0 ‰ , for example, at ∼ 400 Ma, the long-term mean δ 13 C remains ∼ 2 ‰ throughout the rest of the Paleozoic, the Mesozoic, and the Early Cenozoic (17), indicating a sustained increase in global organic carbon burial.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [17] Saltzman MR, Thomas E (2012) Carbon isotope stratigraphy. The Geologic Time Scale , eds Gradstein FM, Schmitz JGOD, Ogg GM (Elsevier, Boston), pp 207 -232. source

      Not checked in the free run.

    • Rests on an assumption: Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).

  • May combine two claims.

    Interpretationreasoning
    § Earliest land plants created modern levels of atmospheric oxygen

    The persistent oxygenation of the ocean and appearance of charcoal can be explained by a rise in atmospheric oxygen occurring by ∼400 Ma.

    “The persistent oxygenation of the ocean and appearance of charcoal can be explained by a rise in atmospheric oxygen occurring by ∼ 400 Ma”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisereasoning
    § Significance

    Land plants typically have a much higher molar C/P ratio (∼1,000) than marine organic matter (∼100), allowing them to support an increased organic carbon burial flux for the same P weathering flux.

    “Land plants typically have a much higher molar C/P ratio ( ∼ 1,000) than marine organic matter ( ∼ 100) due to carbon-rich but phosphorus-poor structural compounds such as sporopollenin, lignin, and, in their fungal mycorrhizal symbionts, chitin; therefore, they can support an increased organic carbon burial flux for the same P weathering flux.”
    Quote in the paperSubstantial claim
    • Rests on an assumption: On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

  • May combine two claims.

    Premisecitation
    § Significance

    The P weathering flux is partly tied to bulk silicate weathering, and the silicate weathering flux of alkalinity is ultimately controlled by the degassing input of CO2 on timescales ≥1 My.

    “The P weathering flux is partly tied to bulk silicate weathering, for example, due to the dissolution of apatite inclusions in silicate rocks, and the silicate weathering flux of alkalinity is in turn set by negative feedback in the longterm carbon cycle, so is ultimately controlled by the degassing input of CO2 on timescales ≥ 1 My (7, 10).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [7] source

      Not checked in the free run.

    • cites [10] source

      Not checked in the free run.

  • May combine two claims.

    Interpretationown data
    § Significance

    The earliest plants first increased atmospheric oxygen to present levels by 400 Ma, and this instigated fire-mediated feedbacks that have stabilized high oxygen levels ever since.

    “Instead, the earliest plants, which colonized the land from 470 Ma onward, first increased atmospheric oxygen to present levels by 400 Ma, and this instigated fire-mediated feedbacks that have stabilized high oxygen levels ever since, shaping subsequent evolution.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Premisecitation
    § Earliest land plants created modern levels of atmospheric oxygen

    Ocean oxygenation is also supported by a Silurian increase in the C/S ratio of shales and a shift in iron speciation data sometime during 435-387 Ma.

    “This ocean oxygenation is also supported by a Silurian increase in the C/S ratio of shales (15), and a shift in iron speciation data sometime during 435 -387 Ma (6).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [15] Berner RA, Raiswell R (1983) Burial of organic carbon and pyrite sulfur in sediments over phanerozoic time: A new theory. Geochim Cosmochim Acta 47(5):855 -862. source

      Not checked in the free run.

    • cites [6] source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation
    § Materials and Methods

    The early charcoal record was compiled from the literature using existing compilations and checking them where possible against the original sources.

    “The early charcoal record (Table S1) was compiled from the literature (11, 12, 28, 44 -72) using existing compilations (12, 44 -47) and checking them where possible against the original sources.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [11] source

      Not checked in the free run.

    • cites [12] source

      Not checked in the free run.

    • cites [28] Kennedy KL, et al. (2013) Lower Devonian coaly shales of northern New Brunswick, Canada: Plant accumulations in the early stages of Terrestrial colonization. J Sediment Res 83(12):1202 -1215. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Results and Discussion

    This finding is broadly consistent with the sulfur isotope record, which shows a marked decline through the Silurian-Early Devonian from ∼30 to ∼18‰, although available data also suggest an earlier Late Ordovician-Early Silurian rise from ∼25 to ∼30‰, which the present model does not capture.

    “This finding is broadly consistent with the sulfur isotope ( δ 34 S) record (38 -40), which shows a marked decline through the Silurian -Early Devonian from ∼ 30 to ∼ 18 ‰ , although available data also suggest an earlier Late Ordovician -Early Silurian rise from ∼ 25 to ∼ 30 ‰ , which the present model does not capture.”
    Quote in the paperNot a substantial claim0 of 3 sources checked
    • cites [38] Prokoph A, Shields GA, Veizer J (2008) Compilation and time-series analysis of a marine carbonate δ 18O, δ 13C, 87Sr/86Sr and δ 34S database through Earth history. Earth Sci Rev 87(3 -4):113 -133. source

      Not checked in the free run.

    • cites [39] Gill BC, Lyons TW, Saltzman MR (2007) Parallel, high-resolution carbon and sulfur isotope records of the evolving Paleozoic marine sulfur reservoir. Palaeogeogr Palaeoclimatol Palaeoecol 256(3 -4):156 -173. source

      Not checked in the free run.

    • cites [40] Jones DS, Fike DA (2013) Dynamic sulfur and carbon cycling through the end-Ordovician extinction revealed by paired sulfate -pyrite δ 34S. Earth Planet Sci Lett 363: 144 -155. source

      Not checked in the free run.

  • Classified as probably not a substantial claim.

    Study design and conductown data
    § Results and Discussion

    Sensitivity analyses indicate that our results are robust.

    “Sensitivity analyses ( SI Materials and Methods ) indicate that our results are robust.”
    Quote in the paperSubstantial claim

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation
    § Materials and Methods

    Uncertainties shown in Fig. 1 represent 2 SD of the mean (analytical precision) plus the propagated uncertainty from matching in-house reference materials to the universal standard NIST SRM 3136 where seawater display δ98/95Mo = 2.3 ‰.

    “Uncertainties shown in Fig. 1 represent 2 SD of the mean (analytical precision) plus the propagated uncertainty from matching in-house reference materials to the universal standard NIST SRM 3136 where seawater display δ 98/95 Mo = 2.3 ‰ (75, 76).”
    Quote in the paperNot a substantial claim0 of 2 sources checked
    • cites [75] Goldberg T, et al. (2013) Resolution of inter-laboratory discrepancies in Mo isotope data: An intercalibration. J Anal At Spectrom 28(5):724 -735. source

      Not checked in the free run.

    • cites [76] Nägler TF, et al. (2014) Proposal for an international molybdenum isotope measurement standard and data representation. Geostand Geoanal Res 38(2):149 -151. source

      Not checked in the free run.

  • May combine two claims.

    Interpretationreasoning
    § Conclusion

    The δ13C record suggests that the increase in organic carbon burial was essentially permanent, producing a new dynamically stable state for atmospheric O2.

    “The δ 13 C record suggests this increase in organic carbon burial was essentially permanent, producing a new dynamically stable state for atmospheric O2.”
    Quote in the paperSubstantial claim

  • May combine two claims.

    Interpretationcitation
    § Conclusion

    New fire-mediated negative feedbacks on O2 were instigated and have played a key role in stabilizing atmospheric O2 concentration up to the present day.

    “new fire-mediated negative feedbacks on O2 were instigated that have played a key role in stabilizing atmospheric O2 concentration up to the present day (22, 43).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [22] Lenton TM, Watson AJ (2000b) Redfield revisited: 2. What regulates the oxygen content of the atmosphere? Global Biogeochem Cycles 14(1):249 -268. source

      Not checked in the free run.

    • cites [43] Kump LR (1988) Terrestrial feedback in atmospheric oxygen regulation by fire and phosphorus. Nature 335:152 -154. source

      Not checked in the free run.

  • May combine two claims.

    Premisecitation
    § Results and Discussion

    The model is consistent with proxy reconstructions of seawater SO4 concentration, which suggest an Ordovician-Silurian rise from ∼6 to ∼10 mM, and with a Silurian increase in the molar C/S ratio of shales from ∼5 to ∼16.

    “The model is consistent with proxy reconstructions of seawater SO4 concentration, which suggest an Ordovician -Silurian rise from ∼ 6 to ∼ 10 mM (41), and with a Silurian increase in the molar C/S ratio of shales from ∼ 5 to ∼ 16 (15).”
    Quote in the paperSubstantial claim0 of 2 sources checked
    • cites [41] Algeo TJ, Luo GM, Song HY, Lyons TW, Canfield DE (2015) Reconstruction of secular variation in seawater sulfate concentrations. Biogeosciences 12(7):2131 -2151. source

      Not checked in the free run.

    • cites [15] Berner RA, Raiswell R (1983) Burial of organic carbon and pyrite sulfur in sediments over phanerozoic time: A new theory. Geochim Cosmochim Acta 47(5):855 -862. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing). May combine two claims.

    Study design and conductown data
    § Materials and Methods

    The sensitivity of predicted global NPP was explored with respect to variations in atmospheric CO2 and corresponding climate state, to constraining vegetation cover with extensive Late Ordovician ice sheet cover, and to varying O2 in combination with CO2.

    “We explored the sensitivity of predicted global NPP to variations in atmospheric CO2 and corresponding climate state (Fig. S1), to constraining vegetation cover with extensive Late Ordovician ice sheet cover (Fig. S2), and to varying O2 in combination with CO2 (Table S2).”
    Quote in the paperNot a substantial claim

  • May combine two claims.

    Interpretationreasoning
    § Conclusion

    In the new steady state, oxidative weathering was increased and became less sensitive to variations in O2.

    “In this new steady state, oxidative weathering was increased (becoming less sensitive to variations in O2)”
    Quote in the paperSubstantial claim

  • Classified as probably not a substantial claim.

    Premisecitation
    § Materials and Methods

    In previously reported weathering experiments with granite, the mean amounts of phosphate weathered into aqueous solution were 0.0137 μmol P in control microcosms and 0.0726 μmol P in biotic microcosms.

    “In our previously reported (20) weathering experiments with granite, the mean amounts of phosphate weathered into aqueous solution were as follows: control microcosms = 0.0137 μ mol P, biotic microcosms = 0.0726 μ mol P.”
    Quote in the paperSubstantial claim0 of 1 sources checked
    • cites [20] Lenton TM, Crouch M, Johnson M, Pires N, Dolan L (2012) First plants cooled the Ordovician. Nat Geosci 5(2):86 -89. source

      Not checked in the free run.

  • Probably not a substantial claim: may not pass S3 (load-bearing).

    Study design and conductcitation
    § Materials and Methods

    In a sensitivity analysis, uncertainty in geologic forcing and alternative initial conditions altering the feedback structure of the model were considered.

    “Then, in a sensitivity analysis, we considered uncertainty in geologic forcing (91), and alternative initial conditions (altering the feedback structure of the model).”
    Quote in the paperNot a substantial claim0 of 1 sources checked
    • cites [91] Royer DL, Donnadieu Y, Park J, Kowalczyk J, Goddéris Y (2014) Error analysis of CO2 and O2 estimates from the long-term geochemical model GEOCARBSULF. Am J Sci 314(9):1259 -1283. source

      Not checked in the free run.

40 of 40

  • The paper relies on this without support.

    The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks.

    “The major long-term source of oxygen to the atmosphere is the burial of organic carbon in sedimentary rocks (which represents the net flux of photosynthesis minus various pathways of respiration and oxidation).”

  • The paper relies on this without support.

    Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks (δ13C).

    “Increases in global organic carbon burial are recorded as positive shifts in the isotopic composition of carbonate rocks ( δ 13 C).”

  • The paper relies on this without support.

    On long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the molar ratio of carbon-to-phosphorus in material that is buried.

    “In simple terms, on long timescales, the global organic carbon burial flux is determined by the supply flux of the ultimate limiting nutrient phosphorus from weathering and the (molar) ratio of carbon-to-phosphorus in material that is buried”

  • The paper relies on this without support.

    The C/P ratio of early land plants was similar to that of extant bryophytes.

    “supported by the high C/P ratio of early land plant material”
    “The C/P ratio of extant bryophytes (Table S3) was compiled from data in the literature (34, 80 -88).”
4 of 4

Claims other papers make about this one

Each is checked against this paper’s own text: does it say what the citing paper says it does?

  • Sedimentary recycling of organic carbon during the Archaean and Proterozoic can help reconcile increases in oxygen, and presumed associated increases in biological productivity, with the lack of a secular trend in δ13Ccarb until the Phanerozoic.

    “Sedimentary recycling of organic carbon during the Archaean and Proterozoic can thus help reconcile increases in oxygen, and presumed associated increases in biological productivity, with the lack of a secular trend in δ13Ccarb until the Phanerozoic17 (where there is a shift from 0 to 2‰ associated with the rise of land plants13).”

    From Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon (2017) · cites this paper as [13]

  • The rise of oxygen to present levels required an increase in organic carbon burial rate, which may have begun in the Neoproterozoic Era but in this model was not completed until the mid-Palaeozoic Era with the colonization of the land by plants and fungi.

    “The rise of oxygen to present levels simply required an increase in organic carbon burial rate, which may have begun in the Neoproterozoic Era10, but in our model was not completed until the mid-Palaeozoic Era with the colonization of the land by plants and fungi, liberating nutrient phosphorus from rocks and producing high C/P material for burial1113.”

    From Atmospheric oxygen regulation at low Proterozoic levels by incomplete oxidative weathering of sedimentary organic carbon (2017) · cites this paper as [13]

Cites

Flagged first, then by citations

2 of the 92 references couldn’t be matched to a known paper.

Research works printed but not linked: 4

  1. HD Pflug, KF Prössl, Palynostratigraphical and paleobotanical studies in the pilot hole of the German continental deep drilling programme results and implications. Sci Drill 2, 13–33 (1991).
  2. KAR Ghori Silurian-Devonian Petroleum Source-Rock Potential and Thermal History, Carnarvon Basin, Western Australia (Geological Survey of Western Australia, Perth, Australia, 1999).
  3. JK Michelsen, GK Khorasani, A regional study on coals from Svalbard; Organic facies, maturity and thermal history. Bull Soc Geol Fr 162, 385–397 (1991).
  4. M Fairon-Demaret, C Hartkopf-Fröder, Late Famennian plant mesofossils from the Refrath 1 Borehole (Bergisch Gladbach-Paffrath Syncline; Ardennes-Rhenish Massif, Germany). CFS Courier Forschungsinstitut Senckenberg 251, 89–121 (2004).

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Related

Authors
Lenton, T. M., Dahl, T. W., Daines, S. J., Mills, B. J. W., Ozaki, K., Saltzman, M. R., & Porada, P.
Affiliations
  • University of Exeter (GB)
  • University of Copenhagen (DK)
  • University of Leeds (GB)
  • Georgia Institute of Technology (US)
  • The Ohio State University (US)
  • Stockholm University (SE)
ORCID
Venue
Proceedings of the National Academy of Sciences
Publisher
National Academy of Sciences
Published
2016-08-15
Volume
113
Issue
35
Pages
9704-9709
ISSN
  • 0027-8424 (ISSN-L)
  • 1091-6490
DOI
10.1073/pnas.1604787113
PMC
PMC5024600
OpenAlex
W2508469640
Cited by
343
References
92
Citations by year
2026: 25 · 2025: 33 · 2024: 45 · 2023: 48 · 2022: 47 · 2021: 34 · 2020: 21 · 2019: 32 · 2018: 31 · 2017: 23 · 2016: 4
FWCI
24.94
Type
journal article
Language
en
Open access
Licence
www.pnas.org/preview_site/misc/userlicense.xhtml (vor, 184 d)
Locations
  • Proceedings of the National Academy of Sciences (publishedVersion)
  • Europe PMC (PubMed Central) (publishedVersion)
  • PubMed Central (publishedVersion)
  • PubMed (publishedVersion)
  • Research at the University of Copenhagen (University of Copenhagen) (publishedVersion)
  • White Rose Research Online (University of Leeds, The University of Sheffield, University of York) (acceptedVersion)
  • Open Research Exeter (University of Exeter) (acceptedVersion)
  • Figshare (submittedVersion)
  • Tokyo Tech Research Repository (Tokyo Institute of Technology) (submittedVersion)
Funders
  • Leverhulme Trust (RPG-2013-106)
  • Natural Environment Research Council (NE/I005978/2)
  • Royal Society (Wolfson Research Merit Award)
Topics
  • Physical Sciences › Earth and Planetary Sciences › Paleontology › Paleontology and Stratigraphy of Fossils
  • Physical Sciences › Earth and Planetary Sciences › Atmospheric Science › Earth Systems and Cosmic Evolution
  • Physical Sciences › Earth and Planetary Sciences › Geophysics › Geological and Geochemical Analysis
Keywords
atmospheric oxygenation, early land plants, organic carbon burial, bryophytes, terrestrial net primary productivity, C:P ratio, carbonate carbon isotopes, biogeochemical cycles, fire feedbacks, redox proxies
MeSH terms
Origin of Life, Atmosphere, Carbon Dioxide, Carbon Isotopes, Biological Evolution, Oceans and Seas, Oxidation-Reduction, Oxygen, Phosphorus, Photosynthesis, Soil, Models, Statistical, Biomass, Earth, Planet, Geologic Sediments, Embryophyta, History, Ancient

About these checks

Registry, retraction, Cites and statistics results are computed, not judged, with one exception: a printed reference that no index lists is read once by a model before it counts as a citation error. Claims are extracted by a model and kept only when their quote appears verbatim in the text; each cited source is then checked, with a model’s help, for whether it says what the claim relies on. Those verdicts can be wrong — read the claim’s quote and the cited source before relying on one.

Claims read by deepseek-v4.1-flash under definition version 3 (extract-v3) on 2026-10-08.

Classified by jev-1.13-20260917 (gold-guideline-v0.2) on 2026-10-08.

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