Warm nights stimulate rainforest tree growth
February 04, 2013
Rainforest trees grown at higher nighttime temperatures put on more than twice as much weight as their counterparts grown under normal circumstances
Rainforest trees grown at higher nighttime temperatures put on more than twice as much weight as their counterparts grown under normal circumstances, according to a new study by scientists at the Smithsonian Tropical Research Institute. This result may force climate modelers who assume trees grow slower at increased temperatures to reconsider the impacts of climate change on tropical forests.
Although global temperatures rose on average by about 0.2°C per decade since 1975, the tropics warmed more quickly, with an average temperature increase of about 0.26°C per decade. And nighttime temperatures rose even faster than daytime temperatures, at least in central Panama. According to Alexander Cheesman, a postdoctoral fellow who co-authored the study with STRI staff scientist Klaus Winter: “Meteorological monitoring on Panama's Barro Colorado Island revealed an increase in nighttime temperatures of 1.5 °C since 1971.” Seemingly small changes may appear insignificant but they mean our biological support systems may soon experience temperatures more extreme than anything felt in the last million years. Researchers subjected fig and balsa tree seedlings to increased nighttime temperatures. The increase in biomass they observed counters conventional wisdom: increased respiration at higher temperatures is supposed to reduce plant weight gain.
“Our results are in total contrast to the assumptions that global climate modelers build their predictions on. As one of my colleagues said: ‘It's not photosynthesis that's driving growth; it's growth that must be driving photosynthesis,' but we have not shown that yet. We clearly need to scale up from seedlings to trees. All of this would be very easy to test if we had giant temperature-controlled greenhouse domes,” says Winter. Reference: Cheesman, A.W. and Winter, K. 2012. Elevated night-time temperatures increase growth in seedlings of two tropical pioneer tree species. New Phytol. 2012 Dec 21. doi: 10.1111/nph.12098.