J.W.
I had goldens which are pretty close to labs. The more you restrict the area they are in the more they destroy. My dogs didn't dig much and when they did it was because I forgot to put out water. Yup they dig for water. Leave a hose out they will chew through it for water. I put a device on the faucet that they can lick and get all the water they wanted, they never dug after that.
Maybe I had strange dogs, who knows.
Okay I just caught the tree part. How hot was it? They will also dig to get to the cool dirt if they are hot.