THE 2ND CASEBOOK OF DR. D. R. SLATER

 

No. 112: "Cut It Out!"

 

I often tell my students that arboricultural practice often develops before there is any science that validates it. A good recent example is where some arborists are suggesting that crown reducing an ash tree affected by ash dieback disease (Hymenoscyphus fraxineus) can result in re-invigorating the tree's crown. Well, for that example, let's do a scientific trial - so we know we are not wasting time and resources...

 

Visiting Lithuania's capital city, Vilnius, my host kindly took me to what is probably the oldest oak in the city, growing at the edge of a large and beautiful park. The tree, however, has had a lot of crown treatments to it - so although it's stem is a good size, it does look rather 'battered' (as shown).

 

One obvious aspect of this veteran tree is that it has been treated by an old European tree practice - of cutting out a decayed section of its stem. There is a wedge-shaped gouge-out of the stem, with chainsaw marks evident (as shown) - where someone has, as a treatment, removed a decaying section of this oak stem with a chainsaw in the hope of preventing further decay in the rest of the remaining stem.

 

I know - some of you reading this will be horrified! 😱😱😱

 

There is some logic associated with this old practice:

 

🔸That it is analogous to how patients with a severely infected limb or body part are sometimes treated - by removal of that part to save the rest of the body.

🔸That, for sure, a decay fungus builds its strength from the food resources it has available to it - by carving out this decaying wood, one is reducing the resources the fungus is feeding upon, as well as removing much of its mycelium.

 

However, has this practice ever been validated as a good treatment for trees by scientists? No. And some counter arguments are:

 

🔹You are essentially doing more harm than good - reducing the structural strength of the stem and cutting through any barriers to decay that the tree may have created naturally.

🔹There is no way in which such a crude treatment could remove ALL the fungal mycelium - so the 'infection' will persist.

 

LESSON LEARNT: Sometimes, an idea of how to treat a tree is tried - and if it appears successful, others might jump onboard with it. However, far better to be patient, wait for an objective trial of the technique that finds the pros and cons of it - before treating valuable trees (like this one) in an irreparable way. Tree science needs to get ahead of tree care practice, essentially, so those practices are verified as positive actions for the tree - and not detrimental.

 

**《史雷特博士第二本病例集》

第112號：「把它切掉！」**

我常告訴學生，樹藝的實務往往先於科學驗證而發展。最近一個很好的例子是：有些樹藝師建議，對受白樺褐斑病（Hymenoscyphus fraxineus）影響的白蠟樹進行冠層縮減，可以重新活化樹冠。對於這種說法，我們應該做一個科學試驗——這樣才能確定我們沒有在浪費時間與資源。

造訪立陶宛首都維爾紐斯時，接待我的朋友帶我去看城裡可能最古老的一棵橡樹，它生長在一座美麗大公園的邊緣。然而，這棵樹的冠層曾接受過許多處理——所以雖然樹幹尺寸可觀，但看起來有些「遍體鱗傷」（如圖）。

這棵老樹最明顯的特徵之一，是它曾接受過一種古老的歐洲樹木處理方式——把樹幹腐朽的部分切除。樹幹上有一個楔形的挖除區，明顯可見鏈鋸痕跡（如圖）——有人把這段腐朽的橡樹幹切掉，作為一種治療，希望能阻止腐朽繼續蔓延到剩餘的樹幹。

我知道——你們當中有些人看到這裡一定會震驚！😱😱😱

這種古老做法其實有一些邏輯：

🔸它類似於醫學上對嚴重感染的肢體或器官進行切除，以保全身體其他部分。 🔸腐朽菌確實依賴可利用的食物資源來壯大——把腐朽木挖掉，等於減少真菌的食物來源，也同時移除大量菌絲體。

然而，這種做法是否曾被科學家驗證為對樹木有益？答案是：沒有。也有一些反對的理由：

🔹你基本上是在造成更大的傷害——削弱樹幹的結構強度，並切穿樹木可能已自然形成的腐朽阻隔。 🔹這種粗糙的處理方式不可能移除所有真菌菌絲——所以「感染」仍會持續。

得到的教訓：

有時，一個樹木處理的想法被嘗試後，看起來似乎成功，其他人便跟著採用。然而，更好的方式是保持耐心，等待客觀的技術試驗，找出其優缺點——再用於珍貴的樹木（像這棵）上，以免造成無法挽回的傷害。樹木科學必須走在樹木養護實務之前，確保這些做法是真正對樹木有益，而不是有害。

 

資料來源:

 

Duncan Slater PhD