Carbon isotopes and water use efficiency: sense and sensitivity

@article{Seibt2007CarbonIA,
  title={Carbon isotopes and water use efficiency: sense and sensitivity},
  author={Ulli Seibt and Abazar Rajabi and Howard Griffiths and Joseph A. Berry},
  journal={Oecologia},
  year={2007},
  volume={155},
  pages={441-454}
}
We revisit the relationship between plant water use efficiency and carbon isotope signatures (δ13C) of plant material. Based on the definitions of intrinsic, instantaneous and integrated water use efficiency, we discuss the implications for interpreting δ13C data from leaf to landscape levels, and across diurnal to decadal timescales. Previous studies have often applied a simplified, linear relationship between δ13C, ratios of intercellular to ambient CO2 mole fraction (Ci/Ca), and water use… 
Revisiting the carbon isotope discrimination and water use efficiency relation: the influence of mesophyll conductance
TLDR
A mathematical expression of iWUE as a function of Δ that includes gm (iWUEmes) and exploits the gm-stomatal conductance (gsc) relationship across drought-stress levels and plant functional groups in a global database is derived.
Accounting for mesophyll conductance substantially improves 13 C-based estimates of intrinsic water-use efficiency.
TLDR
The inclusion of the gsc /gm ratio, fixed at 0.79 when gm was unknown, proved desirable to eliminate significant errors in estimating iWUE from Δ across various C3 vegetation types.
How do leaf and ecosystem measures of water-use efficiency compare?
TLDR
This study quantifies the uncertainty associated with different methods of measuring WUE, indicates potential for bias when using WUE measures to parameterize or validate models, and indicates key research directions needed to reconcile alternative measures of WUE.
Variation in the carbon and oxygen isotope composition of plant biomass and its relationship to water-use efficiency at the leaf- and ecosystem-scales in a northern Great Plains grassland.
TLDR
Investigating the causes of seasonal and inter-annual variability in water-use efficiency in a grassland near Lethbridge, Canada using stable isotope (leaf-scale) and eddy covariance measurements (ecosystem- scale) demonstrated that water stress was not a significant limitation on photosynthesis and biomass production in these years.
Gas exchange and water-use efficiency in plant canopies.
TLDR
In coming decades, increases in plant water-use efficiency caused by rising CO2 are likely to partially mitigate impacts on plants of drought stress caused by global warming.
Observed and modelled historical trends in the water-use efficiency of plants and ecosystems.
TLDR
The causes of variations in observed and modelled historical trends in WUE over the continuum of scales from leaf to ecosystem are reviewed, including methodological issues, with the aim of elucidating the reasons for discrepancies observed within and across spatial scales.
The validity of optimal leaf traits modelled on environmental conditions.
TLDR
Predicted values of photosynthetic traits, including carboxylation capacity (Vcmax ), derived from δ13 C, growth temperature and solar radiation, showed meaningful agreement with inferred values derived from gas-exchange measurements, supporting the general hypothesis that many key parameters required by Earth system models are adaptive and predictable from plants' growth environments.
Historical changes in the stomatal limitation of photosynthesis: empirical support for an optimality principle.
TLDR
The results support theoretical predictions that variations in χ are tightly regulated by the four environmental drivers and suggest that explicitly accounting for the effects of plant-available soil water and other site-specific characteristics might improve the predictions.
Whole-tree mesophyll conductance reconciles isotopic and gas-exchange estimates of water-use efficiency.
TLDR
It is concluded that δ13 Cph is a good proxy for whole-tree iWUE, with the caveats that post-photosynthetic fractionations and intrinsic variability of gm should be incorporated to provide reliable estimates of this trait in response to abiotic stress.
Relationships Between Tree Height and Carbon Isotope Discrimination
Understanding how tree size impacts leaf- and crown-level gas exchange is essential to predicting forest yields and carbon and water budgets. The stable carbon isotope ratio (δ13C) of organic matter
...
1
2
3
4
5
...

References

SHOWING 1-10 OF 70 REFERENCES
Spatial distribution of leaf water‐use efficiency and carbon isotope discrimination within an isolated tree crown
The spatial variations in the stable carbon isotope composition ( δ 13 C) of air and leaves (total matter and soluble sugars) were quantified within the crown of a well-watered, 20year-old walnut
Internal conductance does not scale with photosynthetic capacity: implications for carbon isotope discrimination and the economics of water and nitrogen use in photosynthesis.
TLDR
It is demonstrated that at common WUE, delta may vary by up to 3 per thousand, which is as large or larger than is commonly reported in many interspecific comparisons of delta, and adds to previous warnings about simplistic interpretations of WUE based on delta.
On the Relationship Between Carbon Isotope Discrimination and the Intercellular Carbon Dioxide Concentration in Leaves
TLDR
It is shown how diffusion of gaseous COz can significantly affect carbon isotopic discrimination and a simple relationship between discrimination and the ratio of the intercellular and atmospheric partial pressures of COZ is developed.
13C discrimination during CO2 assimilation by the terrestrial biosphere
TLDR
From this model, it is estimated that, on a global basis, 21% of GPP is by C4 plants and for the terrestrial biosphere as a whole, an average isotope discrimination during photosynthesis of 14.8‰ is calculated, which is slightly less than would be calculated from C4 plant dry matter carbon isotopic composition.
Carbon isotope discrimination indicates improving water-use efficiency of trees in northern Eurasia over the last 100 years
We investigated the response of conifer trees in northern Eurasia to climate change and increasing CO2 over the last century by measuring the carbon isotope ratio in tree rings. Samples from Larix,
The influence of (photo)respiration on carbon isotope discrimination in plants
TLDR
Consideration of photorespiratory fractionation is necessary when interpreting δ 13 C of leaf material, especially under conditions where (photo)respiratory CO 2 losses make a large relative contribution to total plant carbon budgets, as well as manipulations of the carbon isotope composition of source CO 2 during growth and measurement.
Homeostatic gas-exchange parameters inferred from 13C/12C in tree rings of conifers
TLDR
Evidence is reported that conifers have undergone adjustments in the intercellular CO2 concentration that have maintained ca-ci constant, which should be considered a homeostatic gas-exchange set point for these conifer species.
Rapid variations of mesophyll conductance in response to changes in CO2 concentration around leaves.
TLDR
Transgenic tobacco plants differing in the amounts of aquaporin NtAQP1 showed different slopes of the gm-Ci response, suggesting a possible role for aquaporins in mediating CO2 responsiveness of gm, and the importance of these findings is discussed in terms of their effects on parameterization of AN-CI curves.
Long-term ci /ca response of trees in western North America to atmospheric CO2 concentration derived from carbon isotope chronologies
TLDR
Calculations show that the ci/ca ratios of the trees were constant or increased slightly before the 20th century, but changed more rapidly in the20th century; some increased, some decreased, and some stayed constant; in contrast, the CO2 concentration inside plant leaves increased monotonically for all trees.
Predicting leaf gas exchange and δ13 C responses to the past 30000 years of global environmental change.
  • D. Beerling
  • Medicine, Environmental Science
    The New phytologist
  • 1994
TLDR
Leaf gas exchange predictions show that the increased water use efficiency of these trees growing in present-day environments was brought about through an increase in photosynthetic rates and a decrease in stomatal conductance, which contrasts with the explanation of the recent increase in the WUE of temperate and Mediterranean ecosystems inferred from δ13 C measurements.
...
1
2
3
4
5
...