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While scientists have long believed that higher temperatures will cause a delay in fall, a new study suggests that, by contrast, tree leaves tend to die and fall off earlier. In question: the trees would be “satiated” in CO2 Faster. Bad news questioning the carbon capture capacity of trees.
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[EN VIDÉO] A beautiful timelapse of leaves taking on their autumn hue Each fall, the leaves on the trees turn yellow, red, or orange before falling. This timelapse illustrates in two minutes this slow and sublime evolution seen in macro thanks to 6,000 photographs patiently assembled.
Another scientific certainty called into question! Contrary to what we thought the lengthening of summer from to global warming do not delay falling tree leaves in autumn, but move it forward! ” Previous models assumed that as autumns get warmer in the next century, theAutumn it will be delayed for two or three weeks », Explains Philip James, one of the authors of the new study published in Science. ” Two decades of field observation show that the fall was delayed by 0.25 days per year “, Reports for example a 2014 study published in Nature Climate Science. But according to Philip James, a professor ofecology from the University of Salford (UK): ” By 2100, when seasons growth of trees it will last 22 to 34 days longer, leaves will drop from trees three to six days earlier today. “
The satiety effect
The explanation of this paradox is in two words: the satiety effect. ” It’s kind of the same mechanism we observe in humans: if you start eating earlier, you’ll be full faster. », Described a CNN Constantin Zohner, researcher at ETH Zurich and co-author of the study. Trees have a file limited photosynthetic capacity during the season, he explains. ” If the tree absorbs more CO2 in spring and summer due to the early start of the season, it will mechanically lose its leaves in early autumn. For every 10% increase in photosynthetic activity during the growing season in spring and summer, the trees lose their leaves, on average, eight days earlier, the study says.
Using a combination of field observations, laboratory tests and modeling, the experts followed six Cash European leafy trees expired (horse chestnut, silver birch, Beech tree European, European, Downy and Rowan larch) over the past six decades. ” Autumn temperatures and day length have been the two main environmental factors in so far senescence leaves. We have identified a third which is self-limited productivity. », Constantin Zohner emphasizes.
When global warming worsens global warming
It might sound anecdotal: after all, taking pictures of yellow-orange forests a week in advance shouldn’t bother many people. Yet the leaves fall a week earlier, or a week of photosynthesis less … and therefore a week less to absorb coal. Or when global warming makes global warming worse! ” The only way to solve this problem would be to allow trees to increase their total capacity ofabsorption du CO2 “, Claims Philip James. But how ? We will have to plant forests ofgenetically modified trees ? We have until 2100 to think about it.
In 2100, plants will grow for another two weeks due to CO2
Article by Janlou CHaput published on 04/26/2014
Global warming can affect plant growth. The increase in temperature and the level of CO2 itself can make herbaceous plants survive for 14 days more in a year by 2100 than today, although this depends on the territories.
The The earth’s climate is evolving. With massive releases of greenhouse gases (including the famous carbon dioxide CO2) related to human activities, our planet heats, leading to profound upheavals in the biosphere. The environment of the polar species is limited, others ecosystems go wrong, so the wildlife and flora may not always know how to adapt.
The installations they are the first to be affected and evident effects are already being felt. The analysis shows that in the United States, between 1900 and today, the time between the last spring thaw and the first negative temperatures in the fall has lengthened by two weeks. Across the Atlantic, the consequences were measured on plants: between 1971 and 2000, the flowering was brought forward by a week, while senescence was postponed by four days.
It has already been shown that increasing the temperature favors the plant growth. But that’s not the only factor directly involved: excess CO2 would also intervene. But at what height? This is what Heidi Steltzer came from Fort Lewis College from Durango (Colorado, United States), wanted to make an estimate.
CO2 extends plant growth by eight days
This research was conducted in grasslands Wyoming for a period of five years, starting in 2006. In the midst of these grassy expanses, plots of about 8.5 m2 they were continuously heated by 1.5 ° C above seasonal averages during the day and another 3 ° C at night. Other fractions of the field benefited from a CO level2 50% more than the current one. Finally, some graphs have exploited both parameters in order to mimic the conditions predicted in 2100.
Only six kind of herbs or shrubs were followed by botanists. The timing of the appearance of the leaves or flowers, ripening of the seeds or yellowing of the leaves. It was difficult to give a correct estimate as the variability was significant from year to year and according to species. However, averaging, the researchers found that plants growing in the only heated parts of the soil saw their growth lengthen by 6.2 days. On plots that combine high temperatures and excess CO2, the growth of the plant was spread over another 14.2 days, we can read in the review Nature.
For the first time, therefore, we have an estimate of the effect of carbon dioxide on the flora of the prairie. However, these observations may differ from region to region, as they depend on soil moisture. In fact, when the rate of CO2 rises, the plant gradually closes its stomata, the pores through which gases are exchanged. On the other hand, the water contained in the plant evaporates less, hence the vegetable lose less. Consequently, it takes less. Growth ends when the soil has emptied its water. Now the liquid of life is not always the limiting factor.
What effects on the 2100 ecosystem?
The consequences of this observation remain to be measured. Although it is difficult to go into general predictions and extrapolations, scientists strongly assume thisecosystem they will be affected, both positively and negatively. For example, in such circumstances, the breeding season could be shortened. Bad news for pollinators if they’re not in sync with the flower cycle. But also for the plants themselves, which depend on these animals to further colonize the earth.
On the other hand, you also need to see life from the bright side, and some species will certainly benefit from this new environment. Nature hates emptiness, the place left vacant by the big losers in this story will soon be filled in order to fight for a balanced ecosystem. Once again, these rearrangements will be largely attributable to Man.
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