The capacity to cope with climate warming declines from temperate to tropical latitudes in two widely distributed Eucalyptus species

Abstract

As rapid climate warming creates a mismatch between forest trees and their home environment, the ability of trees to cope with warming depends on their capacity to physiologically adjust to higher temperatures. In widespread species, individual trees in cooler home climates are hypothesized to more successfully acclimate to warming than their counterparts in warmer climates that may approach thermal limits. We tested this prediction with a climate-shift experiment in widely distributed Eucalyptus tereticornis and E. grandis using provenances originating along a ~2500 km latitudinal transect (15.5-38.0°S) in eastern Australia. We grew 21 provenances in conditions approximating summer temperatures at seed origin and warmed temperatures (+3.5 °C) using a series of climate-controlled glasshouse bays. The effects of +3.5 °C warming strongly depended on home climate. Cool-origin provenances responded to warming through an increase in photosynthetic capacity and total leaf area, leading to enhanced growth of 20-60%. Warm-origin provenances, however, responded to warming through a reduction in photosynthetic capacity and total leaf area, leading to reduced growth of approximately 10%. These results suggest that there is predictable intraspecific variation in the capacity of trees to respond to warming; cool-origin taxa are likely to benefit from warming, while warm-origin taxa may be negatively affected.

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

“…This may have been caused by having a relatively small number of climates of origin or a limited geographic range. For the widespread species Eucalyptus grandis W.Hill and Eucalyptus tereticornis Sm., intraspecific variation in A and growth showed that the capacity to cope with 3.5 C warming is higher in cooler sites, suggesting that trees from warmer sites are near a thermal limit (Drake et al 2015). Our results for photosynthetic tolerance of a springtime heatwave are somewhat similar for plants in aCO 2 but not eCO 2 .…”

“…suggest that their distributions are related to tolerance of thermal extremes, rather than their growth rate responses to typical sublethal conditions (Paton 1980). These prior results show that responses to both episodic temperature extremes and conditions that mimic slow, chronic warming are important for photosynthetic physiology of some Eucalyptus species, and can help explain their geographic distribution (Drake et al 2015). Previous research has observed genotypic variation in physiological response to eCO 2 within E, camaldulensis var.…”

“…Elevated CO 2 often does not lead to enhanced photosynthetic performance or survival of heatwave events (Bauweraerts et al 2014;Duan et al 2014). In some cases, photosynthetic and leaf area responses to growth temperature suggest intraspecific variation in the thermal response of some Eucalyptus species (Drake et al 2015). These results indicate that there are diverse functional responses to eCO 2 , weather, and climate among the eucalypts and neighbouring species of south-east Australia that could be important for their management.…”

“…These results are similar to previous studies of the effects of eCO 2 on photosynthesis for Eucalyptus spp. during or following exposure to high temperature events Ball 1996a, 1996b), which can be driven, in some cases, by intraspecific variation within species (Drake et al 2015) or by environmental variation across species collection sites (Lewis et al 2011). The effects of eCO 2 on the heat or high-temperature stress tolerance of plants can act on several sites or processes within cells (Weis and Berry 1988;Murata et al 2007), which may help determine major distribution patterns (Osmond et al 1987;O'Sullivan et al 2017).…”

Modelling seed germination response to temperature inEucalyptusL'Her. (Myrtaceae) species in the context of global warming

“…Evidence exists to show that many Eucalyptus can grow successfully outside their natural distributions at warmer mean annual temperatures (Butt et al, 2013;Booth, 2015;Booth et al, 2015) and are highly plastic in traits related to maintaining fitness under novel conditions (Byrne et al, 2013;McLean et al, 2014). Adult plants may have the capacity to buffer extremes of climate through physiological resistance or phenotypic plasticity (for example, changes in water use efficiency and specific leaf area) (Nicotra et al, 2010;Drake et al, 2014) but it is thought that long-lived tree species are unlikely to track rapidly changing environments effectively due to slow response times to changing climates (Pearson and Dawson 2003;Butt et al, 2013). The reproductive stages of a plant's life cycle often represent a major bottleneck for species persistence, and tolerance in this early developmental stage is critical for survival, more so than at the adult stage (Watkinson, 1997;Lloret et al, 2004).…”