Photo from Pexels by Alex Rusin
As the days shorten and temperatures drop in the northern hemisphere, leaves begin to turn. We can enjoy glorious autumnal colours while the leaves are still on the trees and, later, kicking through a red, brown and gold carpet when out walking.
When temperatures rise again in spring, the growing season for trees resumes. Throughout the warmer months, trees take carbon dioxide from the atmosphere and store it in complex molecules, releasing oxygen as a byproduct. This, in a nutshell, is the process of photosynthesis. The more photosynthesis, the more carbon is locked away.
We know that carbon dioxide is a major driver of climate change, so the more that can be taken out of the atmosphere by plants, the better. With the warmer climate leading to a longer growing season, some researchers have suggested that more carbon dioxide would be absorbed by trees and other plants than in previous times. But a new study has turned this theory on its head and could have profound effects on how we adapt to climate change.
The researchers, led by Deborah Zani at the Swiss Federal Institute of Technology, studied the degree to which the timing of colour changes in autumn tree leaves was determined by the growth of the plant in the preceding spring and summer.
Temperature and day length were traditionally accepted as the main determinants of when leaves changed colour and fell, leading some scientists to assume that warming temperatures would delay this process until later in the season. Studying deciduous European tree species, including horse chestnut, silver birch and English oak, the authors of the new study recorded how much carbon each tree absorbed per season and how that ultimately affected when the leaves fell.
deciduous [dɪˈsɪdʒuəs]: adj. 落叶性的，脱落性的；非永久性的
Using data from the Pan European Phenology Project, which has tracked some trees for as long as 65 years, the researchers found in their long-term observational study that as the rate of photosynthesis increased, leaves changed colour and fell earlier in the year. For every 10% increase in photosynthetic activity over the spring and summer growing season, trees shed their leaves, on average, eight days earlier.
Climate-controlled experiments on five-year-old European beech and Japanese meadowsweet trees suggest what could be behind this unexpected result. In these trials, the trees were exposed to full sun, half shade or full shade. The results show that there is a limit to the amount of photosynthesis that a tree can carry out over a growing season. Think of it like filling a bucket with water. It can be done slowly or quickly, but once the bucket is full, there is nowhere for any more water to go.
This research shows that deciduous trees can only absorb a set amount of carbon each year and once that limit is reached, no more can be absorbed. At that point, leaves begin to change colour. This limit is set by the availability of nutrients, particularly nitrogen, and the physical structure of the plant itself. Nitrogen is a key nutrient which plants need in order to grow, and it's often the amount of available nitrogen that limits total growth. This is why farmers and gardeners use nitrogen fertilisers, to overcome this limitation.
Together, these constraints mean that carbon uptake during the growing season is a self-regulating mechanism in trees and herbaceous plants. Only so much carbon can be taken up.
herbaceous [hɜːˈbeɪʃəs]: adj. 草本的；绿色的；叶状的
In a world with increasing levels of carbon in the atmosphere, these new findings imply that warmer weather and longer growing seasons will not allow temperate deciduous trees to take up more carbon dioxide. The study's predictive model suggests that by 2100, when tree growing seasons are expected to be between 22 and 34 days longer, leaves will fall from trees between three and six days earlier than they do now.
This has significant implications for climate change modelling. If we accept that the amount of carbon taken up by deciduous trees will remain the same each year regardless of the growing season, carbon dioxide levels will rise more quickly than was previously expected. The only way to change this will be to increase the capacity of trees to absorb carbon.
Plants that aren" alt="研究发现：气候变暖导致秋天树叶提前变色掉落">
秋天是一年中最美的季节，因为有绚丽多彩的树叶和金灿灿的落叶铺就的“地毯”。新研究指出，今后你看到这一秋日美景的时间要提前了，因为气候变暖将让秋天的树叶提早变色和掉落。 Photo from Pexels by Alex Rusin As the days shorten and temperatures drop in the northern hemisphere, leaves begin to turn. We can enjoy glorio...
A photo captures the changing colors of autumn in Beijing. [Photo by He Jianyong/for chinadaily.com.cn]
Autumn, wherever it is, always has something to recommend itself. In North China, however, it is particularly limpid, serene and melancholy. To enjoy its atmosphere to the full in the onetime capital, I have, therefore, made light of travelling a long distance from Hangzhou to Qingdao, and thence to Peiping.
There is of course autumn in the South too, but over there plants wither slowly, the air is moist, the sky pallid, and it is more often rainy than windy. While muddling along all by myself among the urban dwellers of Suzhou, Shanghai, Xiamen, Hong Kong or Guangzhou, I feel nothing but a little chill in the air, without ever relishing to my heart's content the flavour, colour, mood and style of the season. Unlike famous flowers which are most attractive when half opening, good wine which is most tempting when one is half drunk, autumn, however, is best appreciated in its entirety.
It is more than a decade since I last saw autumn in North. When I am in the South, the arrival of each autumn will put me in mind of Peiping" alt="美文翻译赏析：《故都的秋》">
Photo by Timothy Eberly on Unsplash
September 23, 2019, marks the start of a new season—but what exactly you should call that season depends on where in the world you are and whom you ask. In Great Britain, the third season of the year usually has only one name: autumn. But if you hop across the Atlantic, you'll find that people use both fall and autumn interchangeably when referring to this time of year, making it the only season in the English language with two widely accepted names. So what is it about the season that makes it so special?
According to Dictionary.com, fall isn" alt="为什么美国人把秋天叫作fall？真相原来是这个！">
学英语的人一般都知道，秋天有autumn和fall两种说法，只不过英国人一般把秋天叫作autumn，而美国人在指代秋天的时候常常会用另一个说法：fall（落下）。有的人以为autumn是传统说法，而fall是现代别称，其实fall的历史比autumn还要悠久。 Photo by Timothy Eberly on Unsplash September 23, 2019, marks the start of a new season—but what exactly y...
Only desolation has autumn been known to arouse;
I would say an autumn day is much better than spring morn.
Autumn, a season brandishing gold, orange and reddish hues, is for much of the world one of the most beautiful seasons. This is certainly the case for Hangzhou. Boasting spectacular scenery throughout the year, the vibrant city offers its visitors a place to fall in love with during the autumn.
Xixi National Wetland Park has long been known for its rustic views and well-preserved wetlands. Covering an area of 1,150 hectares, the park has a variety of plants and trees, including persimmon, pomegranate, willow, camphor, bamboo, mulberry, plum, peach, elm, maple, poplar, hibiscus and reed. When autumn comes, the park is dotted with reed flowers and red persimmons.
Qixia Mountain stands in Qixia Town, about 13.6 miles from northeastern Nanjing City. During the late autumn, the crimson autumnal leaves are as red as roses. Many Nanjing families enjoy going out to appreciate the colors of the season.
When dew forms in late autumn, it transforms the entire hill into a beautiful spectacle. Several lovely green pines mix with the many maple trees, adding a special charm to the place.
The autumn in Beijing is the best season to enjoy the spectacular scenery of red leaves in Beijing" alt="推荐！秋游季节最美的几个地方，你打卡了没？">
Different from the south, autumn in the north is more obvious and beautiful. In the south, all the year round are green, but in the north, there are many colors. Autumn is golden yellow. When it comes to autumn, the leaves and grass turn to yellow gradually....