James R Ehleringer

Publications (351) View all

• Source

  Available from: Douglas C Duckworth

  Article: Bayesian integration of isotope ratio for geographic sourcing of castor beans.

  Bobbie-Jo Webb-Robertson, Helen Kreuzer, Garret Hart, James Ehleringer, Jason West, Gary Gill, Douglas Duckworth
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  ABSTRACT: Recent years have seen an increase in the forensic interest associated with the poison ricin, which is extracted from the seeds of the Ricinus communis plant. Both light element (C, N, O, and H) and strontium (Sr) isotope ratios have previously been used to associate organic material with geographic regions of origin. We present a Bayesian integration methodology that can more accurately predict the region of origin for a castor bean than individual models developed independently for light element stable isotopes or Sr isotope ratios. Our results demonstrate a clear improvement in the ability to correctly classify regions based on the integrated model with a class accuracy of 60.9 ± 2.1% versus 55.9 ± 2.1% and 40.2 ± 1.8% for the light element and strontium (Sr) isotope ratios, respectively. In addition, we show graphically the strengths and weaknesses of each dataset in respect to class prediction and how the integration of these datasets strengthens the overall model.
  Journal of Biomedicine and Biotechnology 01/2012; 2012:450967. · 2.44 Impact Factor
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  Available from: James R Ehleringer

  Article: American fast food isn't all corn-based.

  Lesley Chesson, James Ehleringer, Thure Cerling
  Proceedings of the National Academy of Sciences 03/2009; 106(6):E8; author reply E9. · 9.68 Impact Factor
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  Available from: Tomas Domingues

  Article: Life form-specific variations in leaf water oxygen-18 enrichment in Amazonian vegetation.

  Chun-Ta Lai, Jean P H B Ometto, Joseph A Berry, Luiz A Martinelli, Tomas F Domingues, James R Ehleringer
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  ABSTRACT: Leaf water (18)O enrichment (Delta(o)) influences the isotopic composition of both gas exchange and organic matter, with Delta(o) values responding to changes in atmospheric parameters. In order to examine possible influences of plant parameters on Delta(o) dynamics, we measured oxygen isotope ratios (delta(18)O) of leaf and stem water on plant species representing different life forms in Amazonia forest and pasture ecosystems. We conducted two field experiments: one in March (wet season) and another in September (dry season) 2004. In each experiment, leaf and stem samples were collected at 2-h intervals at night and hourly during the day for 50 h from eight species including upper-canopy forest trees, upper-canopy forest lianas, and lower-canopy forest trees, a C(4) pasture grass and a C(3) pasture shrub. Significant life form-related differences were detected in (18)O leaf water values. Initial modeling efforts to explain these observations over-predicted nighttime Delta(o) values by as much as 10 per thousand. Across all species, errors associated with measured values of the delta(18)O of atmospheric water vapor (delta(v)) appeared to be largely responsible for the over-predictions of nighttime Delta(o) observations. We could not eliminate collection or storage of water vapor samples as a possible error and therefore developed an alternative, plant-based method for estimating the daily average delta(v) value in the absence of direct (reliable) measurements. This approach differs from the common assumption that isotopic equilibrium exists between water vapor and precipitation water, by including transpiration-based contributions from local vegetation through (18)O measurements of bulk leaf water. Inclusion of both modified delta(v) and non-steady state features resulted in model predictions that more reliably predicted both the magnitude and temporal patterns observed in the data. The influence of life form-specific patterns of Delta(o) was incorporated through changes in the effective path length, an important but little known parameter associated with the Péclet effect.
  Oecologia 07/2008; 157(2):197-210. · 3.41 Impact Factor
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  Available from: James R Ehleringer

  Article: Comparative ecophysiology of C3 and C4 plants

  R. W. PEARCY, J. EHLERINGER
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  ABSTRACT: In this review we relate the physiological significance of C4 photosynthesis to plant performance in nature. We begin with an examination of the physiological consequences of the C4 pathway on photosynthesis, then discuss the ecophysiological performance of C4 plants in contrasting environments. We then compare the performance of C3 and C4 plants when they occur together in similar habitats, and finally discuss the distribution of C4 photosynthesis with respect to the physical environment, phylogeny, and life form.
  Plant Cell and Environment 04/2006; 7(1):1 - 13. · 5.22 Impact Factor
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  Available from: James R Ehleringer

  Article: Epidermis effects on spectral properties of leaves of four herbaceous species

  Z. F. Lin, J. Ehleringer
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  ABSTRACT: The spectral properties of the leaves of the herbaceous species Brassica oleracea L. var. botrytis L., Cerastum tomentosum L., Petunia hybrida Vilm., and Talinum paniculatum (Jacq.) Gaertn. were examined to see what effect the epidermis had on leaf absorptance, reflectance and transmittance. Removal of the epidermis from the side of the leaf surface being illuminated resulted in increases in leaf absorptance and transmittance, and a decrease in reflectance in the 400–800 nm waveband. Removal of the epidermis from the opposite side of an illuminated leaf (effect was similar in both abaxial and adaxial surfaces) resulted in small decreases in both absorptance and reflectance, and corresponding increases in transmittance. Removal of both the upper and lower epidermis resulted in a marked increase in transmittance, while both leaf reflectance and absorptance were decreased. The results suggest that the presence of the epidermis significantly increases leaf absorptance in the photosynthetic wavebands.
  Physiologia Plantarum 04/2006; 59(1):91 - 94. · 3.11 Impact Factor