Prediction of atmospheric δ¹³CO₂ using fossil plant tissues

Abstract

Reconstruction of the carbon isotope composition of atmospheric CO2 is critical to the understanding of long‐term global carbon cycling. We have suggested that the δ13C value of land plant carbon (δ13Cp) preserved in the geologic record should reflect the δ13CO2 at the time during which the plants grew (δ13Ca), based on a meta‐analysis of modern plant data. Here we present the results of laboratory experiments designed to quantify the relationship between plant tissue δ13C and δ13CO2 values under varying environmental conditions, including differential pCO2 ranging from 1 to 3 times today's levels. As predicted, plants grown under elevated pCO2 showed increased average biomass compared to controls grown at the same temperature. Across a very large range in δ13Ca (≈24‰) and pCO2 (≈740 ppmv) we observed a consistent correlation between δ13Ca and δ13Cp (p < 0.001). We show an average isotopic depletion of −25.4‰ for aboveground tissue and −23.2‰ for belowground tissue of Raphanussativus L. relative to the composition of the atmosphere under which it formed. For aboveground and belowground tissue, grown at both ∼23°C and ∼29°C, correlation was strong and significant (r2 ≥ 0.98 and p < 0.001); variation in pCO2 level had little or no effect on this relationship. These results validate our initial conclusion that in the absence of environmental stress, plant δ13C primarily reflects atmospheric δ13CO2 linearly across pCO2 levels; the demonstrated excellent correlation in δ13Ca and δ13Cp suggests a high level of predictive power across varying environmental conditions.

Global patterns in leaf 13 C discrimination and implications for studies of past and future climate

“…Relationships based on modern plants may not fully quantify the response of Δ leaf to greenhouse climate conditions (high T and pCO 2 ) such as those of the PETM (12,13,38). Given the multiple functions of stomata (water loss prevention, CO 2 provision for A, evaporative cooling), it is unlikely that plants could simultaneously maintain homeostasis with respect to leaf T (15) and c i or Δ leaf (12) during periods of rapid global change.…”

The effect of atmospheric CO2 concentration on carbon isotope fractionation in C3 land plants

“…The average pCO 2 levels for each of the eight R. sativus experiments were 407,497,576,780,1494,2723,3429, and 4200 ppm; the seven A. thaliana experiments were conducted at pCO 2 levels of 370, 455, 733, 995, 1302, 1843, and 2255 ppm. We chose to grow A. thaliana based on recent reports of its growth at 550 ppm (Li et al, 2008) and the wealth of previous biological characterizations based on its use as the genome-based molecular model for plant organisms (The Arabidopsis Genome Initiative, 2000). We chose to grow R. sativus because of its particular anatomical distinction between above-and below-ground tissues (Jahren et al, 2008;Schubert and Jahren, 2011), which allowed for clear separation and analysis of root versus shoot and leaf tissues; R. sativus is also considered a model species for the study of below-ground growth and root development (e.g., Idso et al, 1988;Idso and Kimball, 1989;Kostka-Rick and Manning, 1993). The number of plants grown at each pCO 2 level (n = 16, R. sativus; n = 9, A. thaliana) exceeded the commonly suggested number (n = 8) arising from the median number of plants harvested in 350 previous elevated-CO 2 experiments (Poorter and Navas, 2003).…”

“…All plant growth occurred within (0.51 cubic meter) positive-pressure Plexiglass chambers designed to control light levels, temperature, relative humidity, pCO 2 level, and d 13 C CO2 within the growth environment (after Jahren et al, 2008;Schubert and Jahren, 2011) (Fig. 1, Tables EA1-EA2).…”

“…In addition, multiple studies of Dd 13 C p have been performed upon plants growing across a gradient of pCO 2 level, either in growth chambers (Beerling and Woodward, 1995;Jahren et al, 2008;Schubert and Jahren, 2011) or in field experiments (Saurer et al, 2003;Sharma and Williams, 2009); other workers have attempted to correlate past pCO 2 level with the Dd 13 C p values of sub-fossil tree rings (Feng and Epstein, 1995;Berninger et al, 2000;Hietz et al, 2005;McCarroll et al, 2009;Treydte et al, 2009;Wang et al, 2011) and fossil leaves Beerling and Woodward, 1993;Van de Water et al, 1994;Beerling, 1996;Peñ uelas and Estiarte, 1997). The majority of these modern and fossil studies show a positive correlation between Dd 13 C p and pCO 2 Van de Water et al, 1994;Beerling and Woodward, 1995;Kü rschner et al, 1996;Peñ uelas and Estiarte, 1997;Berninger et al, 2000;Saurer et al, 2003;Hietz et al, 2005;Sharma and Williams, 2009;Treydte et al, 2009); however, negative correlation (Beerling and Woodward, 1993;Beerling, 1996) and no correlation (Jahren et al, 2008) have also been reported. Therefore, there exists no clear consensus as to the effect that pCO 2 has on Dd 13 C p .…”

Organic matter and palaeoenvironmental signals during the Early Triassic biotic recovery: The Salt Range and Surghar Range records

“…Bulk organic C-isotope data are known to be strongly dependent on the composition of the organic matter and physical factors during plant growth, such as temperature, water availability, insolation etc. (Jahren et al, 2008). Therefore, it is essential to know the composition of the OM as well as the isotopic end-members of marine and terrestrial OM respectively.…”