Assessing the effects of nitrogen deposition and climate on carbon isotope discrimination and intrinsic water‐use efficiency of angiosperm and conifer trees under rising CO₂ conditions

Abstract

The objective of this study is to globally assess the effects of atmospheric nitrogen deposition and climate, associated with rising levels of atmospheric CO2 , on the variability of carbon isotope discrimination (Δ(13) C), and intrinsic water-use efficiency (iWUE) of angiosperm and conifer tree species. Eighty-nine long-term isotope tree-ring chronologies, representing 23 conifer and 13 angiosperm species for 53 sites worldwide, were extracted from the literature, and used to obtain long-term time series of Δ(13) C and iWUE. Δ(13) C and iWUE were related to the increasing concentration of atmospheric CO2 over the industrial period (1850-2000) and to the variation of simulated atmospheric nitrogen deposition and climatic variables over the period 1950-2000. We applied generalized additive models and linear mixed-effects models to predict the effects of climatic variables and nitrogen deposition on Δ(13) C and iWUE. Results showed a declining Δ(13) C trend in the angiosperm and conifer species over the industrial period and a 16.1% increase of iWUE between 1850 and 2000, with no evidence that the increased rate was reduced at higher ambient CO2 values. The temporal variation in Δ(13) C supported the hypothesis of an active plant mechanism that maintains a constant ratio between intercellular and ambient CO2 concentrations. We defined linear mixed-effects models that were effective to describe the variation of Δ(13) C and iWUE as a function of a set of environmental predictors, alternatively including annual rate (Nrate ) and long-term cumulative (Ncum ) nitrogen deposition. No single climatic or atmospheric variable had a clearly predominant effect, however, Δ(13) C and iWUE showed complex dependent interactions between different covariates. A significant association of Nrate with iWUE and Δ(13) C was observed in conifers and in the angiosperms, and Ncum was the only independent term with a significant positive association with iWUE, although a multi-factorial control was evident in conifers.

Effects of Climate Change on Vegetation in Mediterranean Forests: A review

“…Tree growth rate might not increase proportionally with increase in photosynthesis because of other limiting factors such as nutrient availability [30,31]. Although experiment enrichment or short -term CO2 increase can lead to higher net primary productivity [32], tree ring analysis in the Mediterranean shows the opposite [33] probably due to limitations in water and nutrients availability [34,35]. This is in line, with the recorded tree growth reduction [36], increased growth variability [37] and defoliation in Mediterranean forests the last decades.…”

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

“…The European δ 13 C tree-ring records analyzed by Frank et al (2015) and Saurer et al (2014) also point to a moderate control towards a constant c i /c a ratio. 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.…”

“…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). The δ 13 C data are used to evaluate global and local models of plant growth, carbon cycling, and land-atmosphere isotopic fluxes for atmospheric carbon balancing (Scholze et al, 2003(Scholze et al, , 2008Suits et al, 2005;Danis et al, 2012;van der Velde et al, 2014).…”

“…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).…”

Revised algorithm of ecosystem water use efficiency for semi-arid steppe in the Loess Plateau of China

“…同 化 的 碳 量 ) 定 量 表 达 (Singh & Gupta, 1977;Baldocchi, 1994) (Leonardi et al, 2012;Battipaglia et al, 2013;Grossiord et al, 2014)。Zhou等(2014 …”