Acclimation of photosynthetic temperature optima of temperate and boreal tree species in response to experimental forest warming

Abstract

Rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain. Such changes may threaten temperature‐sensitive species, causing local extinctions and range migrations. This study examined the optimal temperature of net photosynthesis (Topt) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota, United States under two contrasting temperature regimes. We hypothesized that Topt would be higher in temperate than co‐occurring boreal species, with temperate species exhibiting greater plasticity in Topt, resulting in better acclimation to elevated temperatures. The chamberless experiment, located at two sites in both open and understory conditions, continuously warmed plants and soils during three growing seasons. Results show a modest, but significant shift in Topt of 1.1 ± 0.21 °C on average for plants subjected to a mean 2.9 ± 0.01 °C warming during midday hours in summer, and shifts with warming were unrelated to species native ranges. The 1.1 °C shift in Topt with 2.9 °C warming might be interpreted as suggesting limited capacity to shift temperature response functions to better match changes in temperature. However, Topt of warmed plants was as well‐matched with prior midday temperatures as Topt of plants in the ambient treatment, and Topt in both treatments was at a level where realized photosynthesis was within 90–95% of maximum. These results suggest that seedlings of all species were close to optimizing photosynthetic temperature responses, and equally so in both temperature treatments. Our study suggests that temperate and boreal species have considerable capacity to match their photosynthetic temperature response functions to prevailing growing season temperatures that occur today and to those that will likely occur in the coming decades under climate change.

Stomatal acclimation to vapour pressure deficit doubles transpiration of small tree seedlings with warming

“…Temperate deciduous trees usually increase T opt in response to warming (Sendall et al . ), which would correspond with our observation of increasing D opt with increasing VPD in all species (Fig. ).…”

Simulation of CO2 Fluxes in European Forest Ecosystems with the Coupled Soil-Vegetation Process Model “LandscapeDNDC”

“…Similarly, the "optimum temperature for photosynthesis" (PSNTOPT) is found to be much lower for boreal (FI-Hyy, FI-Sod, in average 8.74 °C) than for temperate forest (NL-Loo, BE-Bra). This is in agreement with field experiments where the link between photosynthetic response potentials and prevailing growing season temperatures had been demonstrated [120]. The differentiation of site-calibrated parameters in this study indicates the degree of acclimation of trees to specific environmental conditions.…”

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

“…A number of previous studies have demonstrated short‐term acclimation of Rubisco kinetics to growth temperature (Medlyn et al ., ; Yamori et al ., ; Kattge & Knorr, ; Lin et al ., ; Yamaguchi et al ., ; Smith & Dukes, ; Crous et al ., ), although the sensitivities of the responses varied. In addition, studies that have compared the acclimation capacity of multiple species in common growth temperatures have shown similar direction and magnitude of short‐term temperature acclimation of T optA (Berry & Björkman, ; Sendall et al ., ) and Rubisco kinetics (Lin et al ., ; Smith & Dukes, ) across species irrespective of their climate of origin. Therefore, we argue that the capacity of species to adjust their photosynthetic biochemistry to temporal variations in growth temperature provides a fitness advantage over that of local climatic adaptation of T optA and its related mechanisms, by enabling species to optimize C balance in their current habitat (Hikosaka et al ., ).…”

“…For curves where the first point was not measured at ambient CO 2 concentration, we extracted the A net value at the measured sample CO 2 concentration falling between 300 and 400 ppm. We estimated the temperature optimum for A net , T optA , by fitting a widely used model of instantaneous photosynthetic temperature response (Gunderson et al ., ; Crous et al ., ; Sendall et al ., ; Vårhammar et al ., ) 1) to the net photosynthesis measurements. The model is a quadratic equation, expressed as: where A net is the net photosynthetic rate (μmol m −2 s −1 ) at a given leaf temperature, T (°C), T optA is the temperature optimum for photosynthesis (°C), A opt is the net photosynthetic rate at T optA , and the parameter b (unitless) describes the degree of curvature of the relationship.…”