Tropical rainforest species have larger increases in temperature optima with warming than warm‐temperate rainforest trees

Abstract

While trees can acclimate to warming, there is concern that tropical rainforest species may be less able to acclimate because they have adapted to a relatively stable thermal environment. Here we tested whether the physiological adjustments to warming differed among Australian tropical, subtropical and warm-temperate rainforest trees.Photosynthesis and respiration temperature responses were quantified in six Australian rainforest seedlings of tropical, subtropical and warm-temperate climates grown across four growth temperatures in a glasshouse. Temperature-response models were fitted to identify mechanisms underpinning the response to warming.Tropical and subtropical species had higher temperature optima for photosynthesis (T optA ) than temperate species. There was acclimation of T optA to warmer growth temperatures. The rate of acclimation (0.35-0.78°C °C-1 ) was higher in tropical and subtropical than in warm-temperate trees and attributed to differences in underlying biochemical parameters, particularly increased temperature optima of V cmax25 and J max25 . The temperature sensitivity of respiration (Q 10 ) was 24% lower in tropical and subtropical compared with warmtemperate species.Overall, tropical and subtropical species had a similar capacity to acclimate to changes in growth temperature as warm-temperate species, despite being grown at higher temperatures. Quantifying the physiological acclimation in rainforests can improve accuracy of future climate predictions and assess their potential vulnerability to warming.

Acclimation of photosynthetic capacity and foliar respiration in Andean tree species to temperature change

“…Strong thermal acclimation of R dark to c. 5°C of warming, regardless of species, has also been observed (Mujawamariya et al, 2021). A major shortcoming of previous acclimation studies, however, is that many are conducted using potted seedlings (Dusenge et al, 2021), or using potted seedlings in highly controlled growing environments (Cheesman & Winter, 2013;Slot & Winter, 2017;Crous et al, 2018;Choury et al, 2022;Wittemann et al, 2022), so little is known about the responses of freely rooted trees growing under field conditions (but see Mujawamariya et al (2021) for R dark ). Understanding the thermal acclimation potential of a variety of Andean TMF species is key to comprehending current observed compositional changes in these ecosystems and to predict how ecosystem composition might be altered by further warming.…”

“…Enzymatic reactions are faster at higher temperatures, allowing plants to achieve optimal CO 2 assimilation with lower levels of photosynthetic enzymes (Arcus et al, 2016;Wang et al, 2020); this should result in warm-acclimated plants exhibiting lower rates of both V cmax and J max than cool-acclimated plants of the same species when measured at a common temperature (Way & Oren, 2010;Ali et al, 2015;Vårhammar et al, 2015;Bahar et al, 2017;Wang et al, 2017Wang et al, , 2020Dusenge et al, 2021). However, previous work on the responses of these parameters to warming is mixed, with studies reporting decreases (Dusenge et al, 2020(Dusenge et al, , 2021, increases (Crous et al, 2013) and no change (Scafaro et al, 2017;Crous et al, 2018Crous et al, , 2022Fauset et al, 2019;Choury et al, 2022) in rates of V cmax and J max at 25°C with warming. R dark is tightly coupled with V cmax (Atkin et al, 2015;Wang et al, 2020) due to a large proportion of respiratory energy being required to synthesise and maintain photosynthetic proteins (O'Leary et al, 2019), including the highly abundant Rubisco (Raven, 2013;Bar-On & Milo, 2019).…”

“…5°C of warming, regardless of species, has also been observed (Mujawamariya et al ., 2021). A major shortcoming of previous acclimation studies, however, is that many are conducted using potted seedlings (Dusenge et al ., 2021), or using potted seedlings in highly controlled growing environments (Cheesman & Winter, 2013; Slot & Winter, 2017; Crous et al ., 2018; Choury et al ., 2022; Wittemann et al ., 2022), so little is known about the responses of freely rooted trees growing under field conditions (but see Mujawamariya et al . (2021) for R dark ).…”

Does plant ecosystem thermoregulation occur? An extratropical assessment at different spatial and temporal scales

“…Whether plant ecosystems can thermoregulate their canopy temperature ( T c ) in response to the changing environment remains a central question in plant ecology and ecophysiology (Doughty & Goulden, 2008; Pau et al ., 2018; Lin et al ., 2020; Choury et al ., 2022), with increasing relevance due to global climate change. T c is a key state variable tightly regulating canopy metabolism of photosynthesis, respiration, and transpiration (Farquhar et al ., 1980; Bernacchi et al ., 2013; Lombardozzi et al ., 2015), which further impacts the growth and health of individual plants, as well as regional to global‐scale carbon and water cycles (Lloyd & Farquhar, 2008; Dong et al ., 2017; Still et al ., 2021).…”

The temperature optima for pollen germination and pollen tube growth of coconut (Cocos nucifera L.) strongly depend on the growth temperature

“…Temperature is one of the principal factors affecting growth and development of crops; therefore, understanding how these processes respond to temperature is important to make predictions on how crops will respond to warming in future climates. Although we have a sound understanding of the impact of rising temperature on growth and development of crops including trees (Choury et al ., 2022; Drake et al ., 2017; Kumarathunge et al ., 2020; Lizumi et al ., 2017), we lack a robust quantitative assessment of how crop reproductive processes are affected by global warming. The reproductive phase of plants is considered one of the most sensitive and vulnerable stages to increasing temperature (Hedhly et al ., 2005).…”