Evidence of a universal scaling relationship for leaf CO₂ drawdown along an aridity gradient

Abstract

Summary• The leaf carbon isotope ratio (d 13 C) of C 3 plants is inversely related to the drawdown of CO 2 concentration during photosynthesis, which increases towards drier environments. We aimed to discriminate between the hypothesis of universal scaling, which predicts between-species responses of d 13 C to aridity similar to within-species responses, and biotic homoeostasis, which predicts offsets in the d 13 C of species occupying adjacent ranges.• The Northeast China Transect spans 130-900 mm annual precipitation within a narrow latitude and temperature range. Leaves of 171 species were sampled at 33 sites along the transect (18 at ‡ 5 sites) for dry matter, carbon (C) and nitrogen (N) content, specific leaf area (SLA) and d 13 C.• The d 13 C of species generally followed a common relationship with the climatic moisture index (MI). Offsets between adjacent species were not observed. Trees and forbs diverged slightly at high MI. In C 3 plants, d 13 C predicted N per unit leaf area (N area ) better than MI. The d 13 C of C 4 plants was invariant with MI. SLA declined and N area increased towards low MI in both C 3 and C 4 plants.• The data are consistent with optimal stomatal regulation with respect to atmospheric dryness. They provide evidence for universal scaling of CO 2 drawdown with aridity in C 3 plants.

Determinants of maximum tree height inEucalyptusspecies along a rainfall gradient in Victoria, Australia

“…4). Globally, D increases with moisture supply in many contexts (Schulze et al 1998, Miller et al 2001, Turner et al 2008, Diefendorf et al 2010, Kohn 2010, Prentice et al 2010, Mencuccini et al 2011) and decreases with tree height locally (Koch et al 2004, Burgess and Dawson 2007, McDowell et al 2011. Our data suggest that, when relative moisture supply and tree height co-vary along a gradient, the effects of the former on maximum tree height will dominate.…”

“…We used simple and multiple regression to test whether D decreases with N content per unit area (N mass /SLA) and increases with SLA, as observed in Eucalyptus from southwestern Australia (Turner et al 2008) and a variety of C 3 plants from the northeast China moisture transect (Prentice et al 2010). We conducted a multiple regression relating D to maximum height and P/E p to determine the relative strengths of the relationships of D to these factors when both are considered, and whether one or both factors had a significant effect on D. We used a similar approach to evaluate the relative effect of maximum tree height (H ) and P/E p on SLA, N mass , and estimated A mass .…”

Thermal acclimation of leaf photosynthetic traits in an evergreen woodland, consistent with the coordination hypothesis

“…Prentice et al (2014) provided field evidence supporting the least-cost hypothesis, stating that plants adopt an optimal c i : c a ratio that minimizes the combined costs per unit carbon assimilation of maintaining the capacities for carboxylation (V cmax ) and water transport. This hypothesis predicts that the c i : c a ratio should increase with temperature due to lower water viscosity (reducing water costs) and higher photorespiration (increasing carboxylation costs) while declining with vapour pressure deficit (VPD) due to increasing water costs (Prentice et al, 2011). …”

Thermal acclimation of leaf photosynthetic traits in an evergreen woodland, consistent with the co-ordination hypothesis

“…This hypothesis predicts, inter alia, that the c i :c a ratio should increase with the Michaelis-Menten coefficient for Rubisco-limited photosynthesis (K) and decrease with vapour pressure deficit (D). The c i :c a ratio is expected to increase with temperature, due to lower water viscosity (reducing water costs) and higher photorespiration (increasing carboxylation costs) , while declining with D (Prentice et al, 2011). 15…”