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Impact of Warming on Photosynthesis of Temperate and Boreal Trees

Paper Reviewed
Sendall, K.M., Reich, P.B., Zhao, C., Jihua, H., Wei, X., Stefanski, A., Rice, K., Rich, R.L. and Montgomery, R.A. 2015. Acclimation of photosynthetic temperature optima of temperate and boreal tree species in response to experimental forest warming. Global Change Biology 21: 1342-1357.

Introducing their paper that was published in Global Change Biology, Sendall et al. (2015) write that "rising temperatures caused by climate change could negatively alter plant ecosystems if temperatures exceed optimal temperatures for carbon gain," noting that "such changes may threaten temperature-sensitive species, causing local extinctions and range migrations." But is this really the case?

In a study they devised to explore this question, the nine researchers examined the optimal temperature for net photosynthesis (Topt) of two boreal and four temperate deciduous tree species grown in the field in northern Minnesota (USA) over a two-year period under two contrasting temperature regimes, which they achieved via the use of infrared heat lamps and buried soil heating cables, while employing dummy lamps and soil cables in the non-heated plots. And the results?

Sendall et al. report "the roughly equivalent differences between Topt and realized temperatures under both ambient and warmed conditions led to realized photosynthetic rates that were 90-95% of optimal in both warming treatments, demonstrating that plants subjected to experimental warming were as well-matched to their environment as ambient plants." And they thus conclude that (1) "despite the modest shift in Topt of 1.1 ± 0.21°C in response to the warming treatment, acclimation was relatively complete, suggesting that direct negative impacts of modest climate warming on photosynthesis will be ameliorated as plants come near to optimizing photosynthesis with respect to temperatures experienced," or, put another way, that (2) "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," which change, it might be added, may never occur.

Posted 19 June 2015