Photosynthesis of temperate Eucalyptus globulus trees outside their native range has limited adjustment to elevated CO₂ and climate warming

Abstract

Eucalyptus species are grown widely outside of their native ranges in plantations on all vegetated continents of the world. We predicted that such a plantation species would show high potential for acclimation of photosynthetic traits across a wide range of growth conditions, including elevated [CO2] and climate warming. To test this prediction, we planted temperate Eucalyptus globulus Labill. seedlings in climate-controlled chambers in the field located >700 km closer to the equator than the nearest natural occurrence of this species. Trees were grown in a complete factorial combination of elevated CO2 concentration (eC; ambient [CO2] +240 ppm) and air warming treatments (eT; ambient +3 °C) for 15 months until they reached ca. 10 m height. There was little acclimation of photosynthetic capacity to eC and hence the CO2-induced photosynthetic enhancement was large (ca. 50%) in this treatment during summer. The warming treatment significantly increased rates of both carboxylation capacity (V(cmax)) and electron transport (Jmax) (measured at a common temperature of 25 °C) during winter, but decreased them significantly by 20-30% in summer. The photosynthetic CO2 compensation point in the absence of dark respiration (Γ*) was relatively less sensitive to temperature in this temperate eucalypt species than for warm-season tobacco. The temperature optima for photosynthesis and Jmax significantly changed by about 6 °C between winter and summer, but without further adjustment from early to late summer. These results suggest that there is an upper limit for the photosynthetic capacity of E. globulus ssp. globulus outside its native range to acclimate to growth temperatures above 25 °C. Limitations to temperature acclimation of photosynthesis in summer may be one factor that defines climate zones where E. globulus plantation productivity can be sustained under anticipated global environmental change.

A test of the ‘one‐point method’ for estimating maximum carboxylation capacity from field‐measured, light‐saturated photosynthesis

“…C i , intercellular CO 2 concentration; A n , net photosynthesis. , and Γ*, the CO 2 compensation point in the absence of mitochondrial respiration (lmol mol À1 ), can be found in the literature (Badger & Collatz, 1977;Jordan & Ogren, 1984;Brooks & Farquhar, 1985;Bernacchi et al, 2001;Crous et al, 2013). We chiefly use values taken from Bernacchi et al (2001), hereafter denoted B01, in common with many TBMs.…”

“…We chiefly use values taken from Bernacchi et al (2001), hereafter denoted B01, in common with many TBMs. To test whether the choice of values for these parameters affects the success of the one-point method, we also used two alternative sets of these parameters, namely those advanced by Badger & Collatz (1977) (hereafter denoted BC77) and Crous et al (2013) (hereafter denoted C13): see Table 2 for details. The Г* temperature dependencies of tobacco (B01) and eucalypt (C13) represent two extremes of the most and least temperature-sensitive Г* responses, respectively, using in vivo gas exchange methods (K. Crous, unpublished).…”

Securing African forests for future drier climates: applying ecophysiology in tree improvement

“…Thus, certain tree genotypes with relatively more 'thirsty' leaves could have an increased risk of hydraulic failure during drought events (Schreiber et al 2016). Indeed, to incorporate levels of photosynthesis in plantation tree selection can be particularly useful to predict their growth suitability across varying climatic conditions (Crous et al 2013; Table 2). Even when the forest canopy cannot be readily accessed for such conventional empirical measurements, remote-sensing of transpiration strategies between various plantation trees may also provide an indication of tree-stress, as was shown for Eucalyptus plantations in South Africa (Dye et al 2004).…”

“…Similarly, in Zimbabwe, correlating the xylem structural adaptations of native Pterocarpus angolensis (kiaat) individuals to historical precipitation in the landscape, provided valuable insights regarding the likely productivity of this widely-planted commodity tree when exposed to variable climatic conditions (Stahle et al 1999). Knowledge of variance in tree hydraulic 6 structure and function thus allows for more precise and advanced future crop development recommendations (Crous et al 2013). …”

Relationships between climate of origin and photosynthetic responses to an episodic heatwave depend on growth CO2 concentration for Eucalyptus camaldulensis var. camaldulensis

“…Growth in eCO 2 can result in lower photosynthetic efficiency for some Eucalyptus species under conditions of high temperatures and irradiance, though the effects are dependent on plant water status Ball 1996a, 1996b). Photosynthesis for some species of Eucalyptus grown in eCO 2 outside their home range may have a limited capacity for summertime temperature acclimation, which demonstrates the strong linkage with climate of origin (Crous et al 2013). Responses to eCO 2 can also be complicated by interacting factors, such as when warmer temperatures increase the impact of drought (Duan et al 2013).…”