研究發現：城裏的樹長得快但死得早

你也許知道城裏老鼠和鄉下老鼠的區別，但你知道城裏的樹和鄉下的樹有什麼不同嗎？研究發現，城裏的樹生長速度比鄉下的樹高出四倍，但死亡率是後者的兩倍多。這是爲什麼呢？

Trees in cities 'live fast but die young' compared to rural forests, warns a new study.

一項新研究警告說，相比鄉間樹林裏的樹，城裏的樹“長得快但死得早”。

Researchers found that trees in urban areas die faster than ones in the countryside as higher levels of carbon dioxide make it harder for the plant to survive.

研究人員發現，城區樹木的壽命比鄉間樹木短，因爲城市二氧化碳濃度更高，讓樹更難存活。

City-dwelling trees suffer a net loss of carbon storage which means trees produce less energy from the air.

生長在城裏的樹碳儲量是淨虧損的，這意味着樹用空氣轉化成的能量更低。

Now researchers say more must be done to tackle the environmental impacts of urbanisation.

研究人員表示，必須做更多工作來應對城市化對環境的影響。

Ian Smith, a PhD student of Boston University in the United States, said: 'Cities are at the forefront of implementing climate mitigation policies including urban greening, to combat rising temperatures and atmospheric CO2 concentrations.

美國波士頓大學的博士生伊恩·史密斯說：“爲了對抗氣溫升高和大氣中二氧化碳濃度變高，在推行城市綠化等減緩氣候變化的政策時，城市是處於最前線的。”

'We find that tree planting initiatives alone may not be sufficient to maintain urban canopies in older cities like Boston.

“我們發現光是種樹也許不足以在波斯頓等老城市保持樹冠覆蓋率。”

'Due to the age and size structure of the existing canopy, efforts to aid in the establishment and preservation of tree health are imperative for increasing urban tree cover and maximising the wide range of ecosystem services provided by the urban canopy.'

“由於現有綠樹的年齡和大小結構，想要增加城市裏的綠樹覆蓋面積，讓城市樹冠提供的生態系統服務範圍最大化，就必須努力增進和保護綠樹健康。”

The research team used a model to forecast short-term changes among street trees for several planting and management scenarios.

研究團隊用了一個模型，通過多種植樹和管理方案來預測街道樹木的短期變化。

Researchers applied the model to estimated tree growth, mortality and planting rates both among trees in Boston city and forests in rural Massachusetts.

研究人員用這個模型來預估馬薩諸塞州波斯頓市和鄉間森林的樹木的生長情況、死亡率和種植成活率。

It was discovered that rates of carbon cycling and mean diameter growth rates among urban trees were nearly four times faster in the city than the countryside.

研究發現，城市樹木的碳循環率和平均直徑增長速度比鄉間樹木高出近四倍。

mean[min]: adj. 平均的

But the positive findings were outweighed by net loss of carbon storage and high mortality losses - which are more than double than trees in rural forests.

但是這一積極的研究發現被淨損失的碳儲量和高死亡率抵消了——城市樹木的死亡率是鄉間樹木的兩倍多。

The study, published in the journal PLOS ONE, has prompted scientists to urge communities to do more to establish and preserve trees which are essential to increasing street-tree canopy cover and carbon storage in vegetation.

發表在《科學公共圖書館·綜合》期刊上的這項研究促使科學家敦促社區更努力地去種植和保護樹木，這對於增加街道樹冠覆蓋率和植被的碳儲量至關重要。

Researchers say strategic combinations of planting and maintenance will be needed to secure urban sustainability but more needs to be done to develop understanding of urban trees and their ecosystems - which may differ from rural forests.

研究人員表示，爲了保證城市可持續發展，需要在戰略上把種樹和保護綠樹結合起來，但還需要增進對城市樹木及其生態系統的瞭解，這一點可能有別於鄉間森林。