搶救老樹的101種方法 (上)

印象中,在台灣山林鄉野間,總有許多參天古木,樹齡動輒數百甚至數千年,不過現在台灣多數的林木,其實並不長壽,因為有太多的人工造景,花台或是石磚 都會導致樹木無法呼吸,最後氣絕死亡。更可怕的是,還有樹癌之稱的「褐根病」, 威脅著所有林木。人生病了要看醫生,樹木其實也有醫生,只不過樹不會說話,不會喊痛,該怎麼治療,對症下藥呢?我們來看樹醫生怎麼為樹把脈。

2012年8月蘇拉颱風來襲, 風強雨大,光是台北市就被吹倒了一千多棵路樹。落枝甚至重擊路人,受害民眾憤而申請國賠,其實這些路樹並非無預警倒下,而是它們早已久病纏身 長年發出無聲的求救訊號。 

幫樹木治病的方法有很多,但到底誰的方式真正有用,沒個準。台灣有相當多樹木專家,會採取「外科手術」的方式治療樹木,他們切除潰爛部位,但需耗費二十至八十萬不等的價格。因此林試所積極成立樹木醫學中心,希望有樹醫證照制度,避免讓民眾為樹求醫,反成冤大頭,尤其是當民眾碰到有樹癌之稱的 「褐根病」。

褐根病能讓罹病大樹無風自倒,透過樹的病根,帶菌種苗或土壤,還能快速向四周擴散,相當難清除。

他叫傅春旭,他和褐根病纏鬥將近17年。會說纏鬥,是因為一顆樹染病,周遭樹都中標,很難預防。但早期並無人重視,結果就是褐根病在台肆虐。

[[傅春旭 研究員 林試所森林保護組 ]]
“我記得那個時候去開個會,他們覺得不嚴重,感染區只有1% 3%而已,一旦你沒有正視這個褐根病,在高雄的時候他們換土,種新的,你現在覺得它不嚴重,可是這個病土跟病根就帶著到處去了,未來它只會愈來愈大、愈來愈嚴重”

根據林木疫情鑑定資訊中心統計,褐根病疫區目前就多達一萬多個,要阻止褐根病擴散,傅春旭和林試所其他學者一起研究各種既存方式,來消滅樹癌。終於發現最有效的藥方,外科手術加上土壤燻蒸法。

[[李財萬 環境工程工作人員 ]]
“手術的做法,第一個先探測根系有沒有得病菌,得了病菌我們再做開挖”

將老樹染病的根部全都切除,磨平後,斷根的樹,還需要裝上鋼架支撐樹體防倒塌,並隨機採取樣本,依照林試所技轉的測試方式,確保病菌全都消滅。

[[黃兆君 環境工程負責人 ]]
“當我在做這棵的時候,我採了非常多的樣本,那其中也是有沒有清創乾淨的,那沒有清創乾淨的以後呢,那我們繼續再告訴我們現場的同仁,在哪一個編號
,他就會在我們編號上面再做清創, 再往深的裡面再挖得更多”

「一個菌」都不留是手術的目標,但走了樣的無根老樹,又該怎麼活下去呢?

[[李財萬 環境工程工作人員 ]]
“我們可以做開根的動作,跟導氣根的動作,導氣根的話,原先它有健康的導氣根,然後包覆水草,然後再加上一些培養土,然後殺菌、 開根,這樣就可以了”

勉強將老榕樹從死亡邊緣救回來,但還有麻煩事等著他們。業者必須要將土內一公分以上的細根,殘渣撿乾淨,集中起來焚化。而土壤的處理更是大工程。

[[張承均 副理 環境工程公司 ]]
外科手術我們在做異地燻蒸的時候,我們就是把它原有的感染範圍的土壤,我們全部移到旁邊,我們再異地去做燻蒸”

要去除褐根病菌的土壤,得下重手。

[[張承均 副理 環境工程公司 ]]
“因為我們現在所使用的這個藥劑,是使用98%的邁隆粒劑,那邁隆跟這個水拌合了之後,它就會產生一些氣體,來做一個殺菌的動作,戴一下這個護具,那因為邁隆有一定的毒性,所以我們必須施作的人都要佩戴塑膠手套跟口罩”


覆蓋兩層黑色塑膠布,再用帆布蓋住,讓邁隆的毒氣可以悶在布內,發揮到最佳的殺菌作用,同時防止毒氣快速外洩傷害人體。林試所強調,會建議用邁隆殺死褐根病,是相中這款農藥沒有殘留的問題。

[[傅春旭 研究員 林試所森林保護組 ]]
“我們在它的理化資料裡面,發現它在土壤25度C的半衰期,是0.75天,消失得很快”

傅春旭強調消毒過的土壤,兩個月後就能夠再使用,還能夠供農業用。美中不足的就是施作農藥時,會產生有毒氣體,破壞臭氧層,但救老樹難道沒有不傷害環境,兩全其美的方式嗎? 下週我們將帶您看到,如何用自然療法,來治療這些生病的樹。

Tree doctors fight to save ancient trees (2013/05/05)

Ancient trees are a key component of the Taiwanese landscape. Old trees can be hundreds or even thousands of years old. However, longevity is denied to many Taiwanese trees in part because of a fungal disease called “brown root rot.” Tonight we examine how Taiwanese arboreal experts are battling the disease and finding ways to heal these ailing trees. 

In August 2012, Typhoon Saola’s strong winds felled more than a thousand trees in Taipei alone. Falling branches can injure pedestrians, leading victims to seek compensation from the state. However, these sidewalk trees did not snap without any warning. Instead, they were chronically ill and have been silently crying out for help all these years.

There are many ways to treat arboreal illnesses, but it’s not clear which methods are most effective. Nor is it clear which “tree surgeons” are best, though their costs range from NT$200,000 to NT$800,000. The Taiwan Forestry Research Institute has founded an arboreal medical center that hopes to clear up this confusion by establishing an arboreal physician certification standard. The certification would help the public identify trustworthy tree doctors. This is especially important in difficult cases such as brown root rot, which is commonly referred to as “tree cancer.”

Brown root rot can cause mighty trees to fall without warning. Through the diseased roots, infected seedlings or soil can spread quickly and be difficult to remove.

This is Fu Chun-hsu傅春旭, a researcher at the Taiwan Forestry Research Institute who has been battling brown root rot for 17 years. Fu says that once a tree is infected, nearby trees are all susceptible. It’s also difficult to prevent. However, brown root rot was not taken seriously in the past. This allowed the disease to run amok. 

Fu Chun-hsu
Associate Researcher, TFRI
I remember going to a meeting where others thought it was unimportant because the area of infection was only 1 to 3 percent. In Kaohsiung they changed the soil and planted new trees. It didn’t seem severe at the time, but the diseased soil and roots were moved elsewhere. In the future, the problem will only get bigger and more serious.

According to the Forest Disease Information Center, there are as many as 10,000 areas of brown root rot infection. To stop the spread of brown root rot, Fu and other researchers have been studying existing methods for eliminating the “tree cancer.” They discovered that the most effective prescription is to combine surgery with soil fumigation.

Li Tsai-wan
Environmental Engineer
The surgical method is to first test to see if the roots have been infected. If they’re infected, we start digging. 

Once infected roots have been severed and sanded, the tree has to be supported by steel frames to prevent it from toppling. And random samples must be taken and analyzed using special methods to ensure that all of the fungus has been destroyed.

Huang Chao-chun
Environmental Engineer
When I was working on this tree, I took a lot of samples. Some were not fully cleansed of fungus. Those that were still infected were identified by serial number. Further cleaning was then conducted by digging deeper.

Cleansing the roots of fungus is the goal of the operation. However, trees would have difficulty surviving without any roots.

Li Tsai-wan
Environmental Engineer
We can stimulate root growth and guide aerial roots. For aerial roots we use existing, healthy roots that are covered in grass and water. We then add fertilizer and disinfectants.

The old banyan is barely rescued from the brink of death. But more troublesome tasks await. Operators must collect roots longer than 1 centimeter and incinerate them. Soil treatment is an even bigger task.

Chang Cheng-chun
Environmental Engineering Manager
During surgery we take the soil in the original infected area and move it to a remote location for fumigation.

Heavy-handed treatment is required to remove brown root rot disease from the soil.

Chang Cheng-chun
Environmental Engineering Executive
The spray we use contains 98 percent dazomet granules that form gaseous compounds when mixed with water. When treating the soil, workers must wear this protective equipment. Because dazomet is toxic, those who apply it need to wear rubber gloves and a mask.

The soil is covered with two layers of black plastic sheeting and a layer of tarpaulin to contain the dazomet fumes. This maximizes killing of the fungus and prevents the rapid dispersal of fumes, which is harmful to humans. The Taiwan Forestry Research Institute emphasizes that dazomet is chosen because it decomposes without environmental residue.

Fu Chun-hsu
Associate Researcher, TFRI
Chemical data shows that in soil at 25 degrees Celsius, dazoment’s half-life is 0.75 days. It disappears very quickly.

Fu says that the decontaminated soil can be reused after two months, even for agriculture. Unfortunately, harmful greenhouses gases are produced when the pesticide is applied. Next week we will examine whether there are natural ways to heal trees without damaging the environment.

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