Reference
Wertin, T.M., McGuire, M.A., van Iersel, M., Ruter, J.M. and Teskey, R.O. 2012. Effects of elevated temperature and [CO2] on photosynthesis, leaf respiration, and biomass accumulation of Pinus taeda seedlings at a cool and a warm site within the species' current range. Canadian Journal of Forest Research 42: 943-957.
What was done
In the words of the authors, they "examined the influence of elevated temperature (ambient + 2°C) and atmospheric CO2 concentration (700 ppm), applied singly and in combination, on biomass accumulation and the temperature response of net photosynthesis (Anet) and leaf respiration (Rd) of loblolly pine (Pinus taeda L.) seedlings grown simultaneously at a northern and a southern site within the species' range," where the long-term mean growing season temperature (from February through October) at the cool site was 15.2°C and at the warm site was 21.5°C, and where the well watered and fertilized seedlings were grown over the course of two consecutive years in half-cylindrical polyfilm-enclosed chambers located in open fields.
What was learned
Wertin et al. report that "biomass accumulation was substantially greater at the warmer site compared with the cooler site regardless of treatment," that "at each site, biomass accumulation was greater in the elevated temperature treatment compared with the ambient treatment," and that "elevated CO2 increased biomass accumulation and Anet at both sites and in both temperature treatments."
What it means
The five University of Georgia (USA) researchers state that their study "provides an indication that future projected increases in CO2 and air temperature of 700 ppm and +2°C, respectively, are likely to increase loblolly pine growth in most, if not all, of its current range." And they say that "the large number of studies that have reported an increase in tree growth in elevated growth temperatures compared with current ambient temperature (Way and Oren, 2010) suggest that other species may respond similarly." Hence, there is reason to believe that rising atmospheric temperatures and CO2 concentrations will likely enhance the growth rates of a large percentage of all of earth's tree species.
Reference
Way, D.A. and Oren, R. 2010. Differential responses to changes in growth temperature between trees from different functional groups and biomes: a review and synthesis of data. Tree Physiology 30: 669-688.