Tom's Blog

Wednesday, July 31, 2019

Surprising resilience of a black walnut tree

As I discussed in a 2017 post, black walnut (Juglans niger) is one of the bad guys in oak savanna restoration.

As that post also discussed, walnut trees are fairly difficult to eradicate permanently. Recently, Kathie and I have found a good example of this (see photo below).

This greatly deformed tree is close to what we call the “Circle Prairie”, a small mostly remnant prairie that I have    discussed in detail in the post linked here. 

There was a large walnut tree formerly in the middle of the Circle Prairie. It was removed in the winter of 2015-2016. To get rid of the substantial amount of wood (small branches, limbs, and trunk), the tree was cut up and piled adjacent to another walnut tree, the one shown in the photo here. There was a lot of wood, and a large pile was built. When the pile was finished, just before starting the fire, one of the crew climbed to the top of the burn pile and lopped off the main trunk of the tree being used as an anchor. (The intention was to also throw the wood of the anchor tree on the burn pile.)

The roaring fire of this burn pile was tended and consolidated in our usual manner. The intention was when we were finished to end up with only ashes. Unfortunately, the crew ran out of time and the anchor tree, topped and coal black, remained as a ghost.

Fast forward to July 25, 2019. Kathie was doing some weeding in the Circle Prairie and noticed the strange tree shown in the photo. The tree is growing vigorously with several large leafy branches. The trunk is pitch black, attesting that it was this tree that participated in the burn pile of 2 ½ years ago.

Explanation? Probably because of the cold weather when the burning took place, some dormant buds near the top of the tree survived the fire and resprouted. But how did the cambium survive that very hot fire, attested to by its black trunk? Presumably the temperature did not get hot enough on the side of the trunk away from the fire.

We have plans to remove this outlandish tree sometime next winter.


Blogger Jake Lloyd said...

How does a native tree that fire resilient not earn its place in a fire adapted savanna? I think there was early settler bias against black walnuts which is why they weren't mentioned often and that they were actually part of Midwestern savanna systems. Just my opinion.

August 1, 2019 at 2:52 PM  
Blogger FrankOnABike said...

Any mature tree is going to be fire tolerant. And what would the settlers have against black walnut anyway? Anyway the surveyors would not have a bias, and black walnuts are rarely recorded in the surveyors notes of the 1830’s. I’ve read hundreds of these and have only seen black walnut recorded once.

August 1, 2019 at 6:08 PM  
Blogger Jake Lloyd said...

This comment has been removed by the author.

August 2, 2019 at 5:41 AM  
Blogger FrankOnABike said...

I believe there was some bias by surveyors as to the trees they chose to reference section corner locations. I have never heard an explanation as to why, but perhaps its because oaks were larger and more prominent or known to be durable and have a long lifespan, therefore being good reference points? Non the less, the surveyors were obligated to record everytree they encounter while running the transects on section lines, there should be no bias there. In southern Wisconsin oak species outnumbered all other trees more than 10 to 1.

August 2, 2019 at 8:22 AM  
Blogger Jake Lloyd said...

Thanks that's kind of what I was thinking too as far as witness trees. It's a little different here in southern MI, but oaks particularly white and black oak far outnumber other species in the surveyors notes. There's also very little mention of walnut in the notes here but other pioneer species are indicated such as aspen, poplar and dogwood so that moots the bias argument. I found some information that stated German settlers in PA actually considered walnuts an indicator of fertile soils, which I thought was interesting. My experience with prescribed fire has been that walnuts are fire tolerant at a pretty early age since they develop corky bark when they're young. They also appear to be prolific resprouters, like oaks. I guess that's why it baffles me that they wouldn't fit the fire adapted landscape.

August 2, 2019 at 8:36 AM  

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