【気候変動】地球温暖化に動じない植物

Plants can acclimate their respiration to increased temperatures, as with global warming, much better than previously thought, reports a paper published in Nature. The study shows that trees are able to adapt their respiration rates to long-term temperature increases more effectively than earlier short-term studies found, indicating that plants are likely to play less of a role than previously suggested in speeding up global warming through accelerated respiration and CO2 emissions as the world warms.

Plant respiration makes a substantial contribution to atmospheric CO2 levels, with plants emitting six times more CO2 than fossil fuel burning. Plant respiration increases with temperature, so it has been suggested that global warming could trigger a positive-feedback loop. However, plants can adjust their metabolism, or acclimate, to higher temperatures, which could offset this effect, but the extent of such acclimation to longer-term increased temperature had remained unknown.

Peter Reich and colleagues measured how 10 North American tree species in forest conditions acclimated their leaf respiration over a 3-5 year period to 3.4°C of warming. They show that, owing to acclimation, respiration increased by only 5%, compared to an expected 23% increase in respiration without acclimation, meaning that acclimation eliminated 80% of the increase in leaf respiration expected for non-acclimated trees. They suggest that increases in respiration rates for terrestrial plants, - and the associated increase in atmospheric CO2 concentration - resulting from global warming may be less than anticipated.