Photosynthetic capacity and leaf nitrogen decline along a controlled climate gradient in provenances of two widely distributed Eucalyptus species

Abstract

Climate is an important factor limiting tree distributions and adaptation to different thermal environments may influence how tree populations respond to climate warming. Given the current rate of warming, it has been hypothesized that tree populations in warmer, more thermally stable climates may have limited capacity to respond physiologically to warming compared to populations from cooler, more seasonal climates. We determined in a controlled environment how several provenances of widely distributed Eucalyptus tereticornis and E. grandis adjusted their photosynthetic capacity to +3.5°C warming along their native distribution range (~16-38°S) and whether climate of seed origin of the provenances influenced their response to different growth temperatures. We also tested how temperature optima (T ) of photosynthesis and J responded to higher growth temperatures. Our results showed increased photosynthesis rates at a standardized temperature with warming in temperate provenances, while rates in tropical provenances were reduced by about 40% compared to their temperate counterparts. Temperature optima of photosynthesis increased as provenances were exposed to warmer growth temperatures. Both species had ~30% reduced photosynthetic capacity in tropical and subtropical provenances related to reduced leaf nitrogen and leaf Rubisco content compared to temperate provenances. Tropical provenances operated closer to their thermal optimum and came within 3% of the T of J during the daily temperature maxima. Hence, further warming may negatively affect C uptake and tree growth in warmer climates, whereas eucalypts in cooler climates may benefit from moderate warming.

Climate warming and tree carbon use efficiency in a whole‐tree 13CO2 tracer study

“…Respiration and photosynthesis may acclimate to temperature together such that their ratio ( R/A ) is constant. This is consistent with some measurements of an invariant R/A ratio across a wide range of temperatures, but with some additional variation at exceptionally high or low temperatures (Atkin et al ., ; Aspinwall et al ., ; Slot & Winter, ; Crous et al ., ; Dusenge et al ., ). Importantly, several studies indicated that the R/A ratio changed in response to a change in growth temperature, but that a homeostatic R/A ratio was restored following the development of new leaves (Ziska & Bunce, ; Loveys et al ., ; Campbell et al ., ).…”

Acclimation and adaptation components of the temperature dependence of plant photosynthesis at the global scale

“…The second important mechanism for acclimation was a change in the magnitude of JV r , as has also been observed by others (Kattge & Knorr, ; Crous et al ., , ; Lin et al ., ). The ratio determines the transition between the two limiting steps, W c and W j .…”

Joint forcing by heat waves and mowing poses a threat to grassland ecosystems: Evidence from a manipulative experiment

“…Mounting evidence points to an increase in the frequency and intensity of HWs, which have affected more than 73% of the global terrestrial area since the mid-20th century (IPCC, 2013;Perkins-Kirkpatrick et al, 2016) and have caused large and widespread impacts at all ecological scales from the species level to the ecosystem level. Severe HW events not only rapidly reduce plant photosynthesis and respiration (Crous Kristine et al, 2018), decrease aboveground and belowground biomass accumulation (Qu, Chen, Dong, & Shao, 2018), and alter the (re)allocation of carbon and nitrogen within a plant (Li et al, 2017), but also result in a decrease in ecosystem gross primary productivity and net ecosystem carbon exchange (Ciais et al, 2005;Qu et al, 2018;Tatarinov et al, 2016).…”