Increased water‐use efficiency does not lead to enhanced tree growth under xeric and mesic conditions

Lévesque, Mathieu; Siegwolf, Rolf; Saurer, Matthias; Eilmann, Britta; Rigling, Andreas

doi:10.1111/nph.12772

Cited by 172 publications

(159 citation statements)

References 66 publications

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“…Our dual-isotope analysis, however, suggests that both species reacted by small and non-significant reductions of stomatal conductance (g s ) and net carbon assimilation [51] (Figure 7). Higher iWUE in P. sylvestris reflected its tighter stomatal control than P. nigra and thus a more isohydric strategy oriented to reduce water spending in accordance with previous results from xeric sites [2,75]. Earlier stomata closing in P. sylvestris might contribute to maintaining hydraulic pressure below dangerous levels at this site, but its conservative strategy might reduce its ability to compete for light if P. nigra grows taller faster.…”

Section: Intrinsic Water-use Efficiencysupporting

confidence: 88%

Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species

Martín-Benito

Anchukaitis

Evans

et al. 2017

Forests

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Exploring how drought influences growth, performance, and survival in different species is crucial to understanding the impacts of climate change on forest ecosystems. Here, we investigate the responses of two co-occurring pines (Pinus nigra and Pinus sylvestris) to interannual drought in east-central Spain by dendrochronological and wood anatomical features integrated with isotopic ratios of carbon (δ 13 C) and oxygen (δ 18 O) in tree rings. Our results showed that drought induces both species to allocate less carbon to build tracheid cell-walls but increases tracheid lumen diameters, particularly in the transition wood between early and latewood, potentially maximizing hydraulic conductivity but reducing resistance to embolism at a critical phase during the growing season. The thicker cell-wall-to-lumen ratio in P. nigra could imply that its xylem may be more resistant to bending stress and drought-induced cavitation than P. sylvestris. In contrast, the higher intrinsic water-use efficiency (iWUE) in P. sylvestris suggests that it relies more on a water-saving strategy. Our results suggest that narrower cell-walls and reduced growth under drought are not necessarily linked to increased iWUE. At our site P. nigra showed a higher growth plasticity, grew faster and was more competitive than P. sylvestris. In the long term, these sustained differences in iWUE and anatomical characters could affect forest species performance and composition, particularly under increased drought stress.

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Section: Intrinsic Water-use Efficiencysupporting

confidence: 88%

Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species

Martín-Benito

Anchukaitis

Evans

et al. 2017

Forests

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“…The d 13 C in tree-ring cellulose (d 13 C tree-ring ) can be used to document changes in the intrinsic water use efficiency, defined as the ratio of leaf CO 2 assimilation (A) to stomatal conductance (g s ) (L evesque et al, 2014;Saurer et al, 2014;Frank et al, 2015). Some studies found that d 13 C tree-ring was unaffected by thinning, implying either that g s and A did not change or that they changed with the same magnitude, that is, the ratio A/g s remained constant (Martin-Benito et al, 2010;Powers et al, 2010;Brooks & Mitchell, 2011;Moreno-Gutierrez et al, 2011).…”

Section: Introductionmentioning

confidence: 99%

Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach

et al. 2015

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SummaryThinning fosters individual tree growth by increasing the availability of water, light and nutrients. At sites where water rather than light is limiting, thinning also enhances soil evaporation and might not be beneficial. Detailed knowledge of the short-to long-term physiological response underlying the growth responses to thinning is crucial for the management of forests already suffering from recurrent drought-induced dieback.We applied a dual isotope approach together with mechanistic isotope models to study the physiological processes underlying long-term growth enhancement of heavily thinned Pinus sylvestris in a xeric forest in Switzerland. This approach allowed us to identify and disentangle thinning-induced changes in stomatal conductance and assimilation rate.At our xeric study site, the increase in stomatal conductance far outweighed the increase in assimilation, implying that growth release in heavily thinned trees is primarily driven by enhanced water availability rather than increased light availability.We conclude that in forests with relatively isohydric species (drought avoiders) that are growing close to their physiological limits, thinning is recommended to maintain a less negative water balance and thus foster tree growth, and ultimately the survival of forest trees under drought.

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“…Leonardi et al (2012) conclude that the temporal variation in δ 13 C in their long-term isotope tree-ring chronologies for 53 sites worldwide supports the hypothesis of an active plant mechanism that maintains a constant ratio between intercellular and ambient CO 2 concentrations. Lévesque et al (2014) reported, from their δ 13 C tree-ring data, an increase in iWUE over the last 50 years in the range of 8 to 29 % for xeric and mesic sites in the Alps and Switzerland. At their sites, drought-induced stomatal closure has reduced transpiration at the cost of reduced carbon uptake and growth.…”

Section: Consistency With Previous Studiesmentioning

confidence: 99%

“…There is a rich body of literature on changes in 13 C isotopic discrimination and iWUE and on observational evidence from δ 13 C tree-ring records McCarroll and Loader, 2004;Fichtler et al, 2010;Leonardi et al, 2012;Churakova , Sidorova, S;Lévesque et al, 2014;Liu et al, 2014b;Saurer et al, 2014;Hartl-Meier et al, 2015;Voelker et al, 2016), free-air CO 2 enrichment (FACE)-type experiments (Battipaglia et al, 2013;Klein et al, 2016), δ 13 C site measurements (Pataki et al, 2003;Bowling et al, 2014), and δ 13 C paleodata (Voelker et al, 2016). These data generally suggest small to moderate decadal-to-century-scale changes in discrimination that correspond to a 20th century increase in iWUE On the order of 20 % and physiological control towards a constant ratio of the partial pressure of CO 2 within the leaf's substomatal cavities to the CO 2 pressure outside the leaf (c i /c a ; Saurer et al, 2004;Leonardi et al, 2012;Frank et al, 2015) and, more generally, a pattern of stomatal optimization towards minimizing water loss per unit carbon assimilated (Voelker et al, 2016).…”

mentioning

confidence: 99%

20th century changes in carbon isotopes and water-use efficiency: tree-ring-based evaluation of the CLM4.5 and LPX-Bern models

et al. 2017

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Abstract. Measurements of the stable carbon isotope ratio (δ 13 C) on annual tree rings offer new opportunities to evaluate mechanisms of variations in photosynthesis and stomatal conductance under changing CO 2 and climate conditions, especially in conjunction with process-based biogeochemical model simulations. The isotopic discrimination is indicative of the ratio between the CO 2 partial pressure in the intercellular cavities and the atmosphere (c i /c a ) and of the ratio of assimilation to stomatal conductance, termed intrinsic wateruse efficiency (iWUE). We performed isotope-enabled simulations over the industrial period with the land biosphere module (CLM4.5) of the Community Earth System Model and the Land Surface Processes and Exchanges (LPX-Bern) dynamic global vegetation model. Results for C3 tree species show good agreement with a global compilation of δ 13 C measurements on leaves, though modeled 13 C discrimination by C3 trees is smaller in arid regions than measured. A compilation of 76 tree-ring records, mainly from Europe, boreal Asia, and western North America, suggests on average small 20th century changes in isotopic discrimination and in c i /c a and an increase in iWUE of about 27 % since 1900. LPXBern results match these century-scale reconstructions, supporting the idea that the physiology of stomata has evolved to optimize trade-offs between carbon gain by assimilation and water loss by transpiration. In contrast, CLM4.5 simulates an increase in discrimination and in turn a change in iWUE that is almost twice as large as that revealed by the tree-ring data. Factorial simulations show that these changes are mainly in response to rising atmospheric CO 2 . The results suggest that the downregulation of c i /c a and of photosynthesis by nitrogen limitation is possibly too strong in the standard setup of CLM4.5 or that there may be problems associated with the implementation of conductance, assimilation, and related adjustment processes on long-term environmental changes.

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Increased water‐use efficiency does not lead to enhanced tree growth under xeric and mesic conditions

Cited by 172 publications

References 66 publications

Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species

Effects of Drought on Xylem Anatomy and Water-Use Efficiency of Two Co-Occurring Pine Species

Improvement of water and light availability after thinning at a xeric site: which matters more? A dual isotope approach

20th century changes in carbon isotopes and water-use efficiency: tree-ring-based evaluation of the CLM4.5 and LPX-Bern models

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