Amazon trees vulnerable to fire and climate combination
15 April 2014 Last updated at 13:18
By Mark KinverEnvironment reporter, BBC News
An increase in the frequency of fires and drought-like conditions could result in an ecological
tipping point
火災和如乾旱般情況的頻率增加，可能會導致引爆生態臨界點
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The combination of fire and extreme weather could accelerate tree mortality in the Amazon,
a study has suggested.
Researchers said field experiments showed that severe droughts could trigger dieback of
forests in the near-term.
Efforts to curb deforestation needed to be accompanied by initiatives to stop land management
fires spreading into adjoining forest reserves, they added.
一項研究表示，火災和極端天氣的結合，可能會加速亞馬遜樹木的死亡率。
研究人員說，實地實驗表明，嚴重的乾旱可能在短期內引發森林枯死。
他們補充說，努力遏制森林砍伐需要配套舉措，開始制止燒林土地管理以防止大火蔓延到
毗鄰的森林保護區。
The findings appear in the Proceedings of the National Academy of Sciences.
Co-author Paulo Brando, a researcher from Brazil's Amazon Environmental Research Institute
and the Woods Hole Research Center, US, explained that the findings were based on data
gathered from a long-running field experiment, described as the first of its kind.
In 2004, the team established three plots in the south-east Amazon - one of which was burned
annually, another was burned every three years, while the remaining one was left untouched as
a control plot.
這項發現發表在美國國家科學院的出版。
合著者保羅·白蘭度，來自巴西的亞馬遜環境研究院和伍茲霍爾研究中心，美國研究人員解釋說，
該研究結果的基礎是從一個長期運行的實地試驗，可謂開創收集數據的先河。
2004年，該小組在亞馬遜東南方成立了三個地塊來試驗 - 其中之一每年被燒毀，另一個每三年
被燒毀一次，而其餘的則原封不動作為對照區。
Aerial photo of experimental plots: annual burn (left); burned every three years (centre) and unburned/control (right). The dashed line indicates the forest edge/interior zone
(Image: P.Brando/PNAS)
航空照片試驗林域：每年焚燒（左）; 每三年焚燒（中心）和未燃/控制（右）。虛線表示
在森林邊緣/內部防區（圖片：P.Brando /美國國家科學院院刊）
"If we burned every year, we did not have enough fuel (leaves and trees) to drive a high intensity
fire - fires that will kill a lot of trees - so we published a few papers saying that this kind of forest
was quite fire resistant," explained Dr Brando.
“如果我們每年都焚燒森林，我們沒有足夠的燃料（樹葉和樹木）來驅動高強度火源 - 火源將
殺死很多樹 - 所以我們發表了幾篇論文說，這種森林相當抗火“ 白蘭度博士解釋說。
An increase in the amount of sunlight reaching the ground raised the forest's ambient
temperature
到達地面的日照量增加提高了森林的環境溫度
But he told BBC News that the team was surprised in 2007: "We burned both plots
(fourth burn for the annual plot and second burn for three-year plot) and both plots responded
really strongly to the fires.
"There was a shift in the system from a forest to a savannah-like environment… grasses
were invading the forest and there were fundamental changes within the ecosystem.
但他告訴BBC新聞，在2007年團隊很驚訝於新發現：“我們燒了兩個區塊（每年焚燒的
第四年和三年焚燒一次的第二循環）且兩個林域對火災回應強烈。
“從森林到大草原般的環境，系統有了轉變，...草入侵了森林，並在生態系統中有了根本
性的變化。
He added that drought conditions during that year triggered the change: "There were more
leaves and twigs on the ground, they were drier so the fires were quite intense.
"To our surprise, the major effects were not observed in the plot we burned every year but
rather in the one we burned every three years.
"This was because there was more time for fuel accumulation, and also it was because the
productivity of that plot was still quite high, whereas in the [annual burn] plot, the fuel was being
removed every year and the productivity of the system was reduced."
他補充說，在那一年的乾旱條件下引發的變化：“有更多的樹葉和樹枝在地面上，他們是
那麼乾燥以至於大火焚燒相當激烈。
“讓我們驚訝的是，主要的效果影響並不是在每年焚燒的而是每三年焚燒的林域。
“這是因為有更多的時間可進行燃料累積，也正是因為那林域區塊的生產力還是相當高，
而在[每年焚燒]的區域，每年燃料被刪除和系統的生產力減少。“
Changing landscape
變化的景觀
The combination of climate change, land-use change and fire may much more destructive”
Prof Yadvinder MalhiUniversity of Oxford氣候變化，土地利用變化和焚火的結合，可更加具破壞性“
牛津 MALHI大學 Yadvinder教授 說明Dr Brando said the abrupt high tree-mortality rates had a lasting impact on the landscape as
grasses invaded the space once occupied by trees.
白蘭度醫生說，突發性高樹木死亡率對景觀產生了持久的影響即一旦草入侵則會佔用樹木
的空間。
"You do not need drought anymore to observe high density fires because grasses can
accumulate way more fuel than the native, wood vegetation," he explains.
“你不再需要一段乾旱期去觀察高密度的火災，因為草可以比原生，木植被積累的方式產生
更多的燃料，”他解釋說。
As well as observing the loss of a number of tree species, Dr Brando said there were wider
ecological consequences as a result of losing tree cover.
"Burned plots were four degrees warmer because they had fewer leaves and less capacity to
cool down the system through photosynthesis," he observed.
除了觀察一些樹種的損失，白蘭度醫生表示，失去樹木覆蓋的結果，有更廣泛的生態後果。
“燒地的地塊溫度較林區高四度更溫暖了，因為他們的葉子較少，使得其少於通過光合作用
以冷卻系統容量，”他說。
"So we have seen major changes, not only in species composition but in the functionality of the
forest as well; it cycles less water because it is warmer and stores less carbon."
Climate models suggest that the probability of severe droughts in the region are likely to be
much more common by the end of the century.
“因此，我們已經看到了重大的變化，不僅在物種組成，且在於森林的功能，以及它的水循
環變少，因為它更溫暖且儲存較少的碳。”
Drought-like conditions and fire combined to change the landscape in the experiment's plots
在實驗區塊林域 乾旱樣的條件和焚火相結合，改變了實驗的地塊景觀
At an international conference held at the University of Oxford in 2012, researchers presented
findings that suggested tropical forests in Africa could be more resilient to future climate change
than the Amazon and other forested regions.
2012年在牛津大學舉行的一次國際會議上，研究人員提出了調查結果，提議非洲的熱帶森林
可能比亞馬遜和其它森林地區會更適應未來的氣候變化。
Scientists at the gathering concluded that tree species in Africa's tropical forests had endured
a number of climatic catastrophes over the past 4,000 years.
科學家們聚會的結論是在非洲的熱帶森林樹種因在過去的4000年已經經歷了若干氣候災難。
During that period, the African forests had lost species that would have been potentially vulnerable,
while the remaining species were "relatively adaptable... to quite rapid changes in rainfall,"
explained conference organiser Yadvinder Malhi, from the university's Environmental Change
Institute.
速變化 ......相對而言具適應性”來自大學的環境變化研究所會議組織者Yadvinder MALHI，解釋說。
Responding to Dr Brando's findings, Prof Malhi said: "Much of current scientific opinion suggests
that intact tropical forests may be quite resilient to climate change, but the combination of climate change, land-use change and fire may be much more destructive.
回應白蘭度博士的研究結果，MALHI 教授說：“大部分現有的科學觀點認為，完整的熱帶森林
可能對應對氣候變化更具適應性，但氣候變化，土地利用變化和焚火的結合可能更具有破壞性。
Prof Malhi, who was not involved in the study, added that these ideas have rarely been demonstrated
in practice.
"What is unique about this study - a long-term experiment that took a lot of stamina and persistence
to implement - is that it directly demonstrates the effects of this deadly combination of factors, and enables exploration of the details of the ecological processes and interactions involved," he told BBC News.
MALHI 教授，並沒有參與這項研究 ，補充說，這些想法很少被證明在實踐中。
“關於此研究是獨特的 - 一項長期的實驗，花了很多精力和毅力來實現的 - 就是它直接演示這一致
命組合的效果，並能夠啟用生態過程和相互作用的細節探索參與，“他告訴BBC新聞。
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