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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.
Sendall, Kerrie M.; Reich, Peter B.; Zhao, Changming; Jihua, Hou; Wei, Xia Orong; Stefanski, Artur; Rice, Karen; Rich, Roy L.; and Montgomery, Rebecca A., "Acclimation of photosynthetic temperature optima of temperate and boreal tree species in response to experimental forest warming" (2014). Faculty Research & Creative Activity. Paper 277.