Scientists grew 19 species of plant at a range of temperatures, monitoring respiration rates. They calculated how temperature related to two common measures of leaf performance: leaf mass per unit of leaf area, and leaf nitrogen content. They then used the results to predict the effects of higher temperatures on the respiration of whole ecosystems. They found that the ability of plants on land to absorb and sequester carbon is indeed likely to weaken as temperatures rise. This is the first time plant respiration’s response to temperature, or ‘acclimation’, has been measured to produce an accurate cross-species picture that can be used in wider climate models. The default setting of the climate model used in the research, produced by the Hadley Centre for Climate Prediction and Research, does not include acclimation. It assumes that as the climate gets hotter, plants’ CO₂ emissions grow exponentially.

‘A commonly-held expectation is that including acclimation in models should slow the acceleration of plant respiration as temperatures rise’ explains Dr Rosie Fisher, a climate modeller at the University of Sheffield. ‘Actually, we found that it had very little effect on the predictions.’ The research, published in Global Change Biology, suggests that in some areas, such as tropical rainforests, carbon emissions may fall as temperatures rise. But worldwide the effect will be negligible. This is partly because forests in cold climate – 40% of the world’s woodland – would become less effective as stores of carbon. These findings strengthen the case of those warning about the dangers posed by climate change,’ says Dr Jon Pitchford, a biological mathematician at the University of York and another of the paper’s authors. ‘They challenge the idea that the planet’s plant life will adjust to increased temperatures in a uniform fashion that will, in turn, help ameliorate global warming’, he adds. As well as respiring, plants take in carbon dioxide and emit oxygen when they photosynthesise. ‘The caveat of this experiment is that we only looked at one side of the plant carbon economics equation, respiration,’ Fisher says. ‘There is no clear agreement on how photosynthesis acclimates to temperature; this is a more complicated question and more experimental research is needed.’ http://www3.interscience.wiley.com/journal/120119111/abstract?CRETRY=1&SRETRY=0 http://planetearth.nerc.ac.uk/news/story.aspx?id=261