[__MatrixMan__]

Even if it's not typical, when circumstances are right they can store a lot of carbon in a hurry.

My garage is on the same level as my basement, so there's a 5' retaining wall on either side of it. Leaves blow around and get trapped in the corners. Once I didn't bother cleaning it up for several years and when I did I had to move several hundred pounds of new soil into my back yard because of how many leaves had decayed there. Small trees were growing in it.

Similar story with the drainage on the side of my house. Not long after I moved in a heavy rain filled my basement with water. I had to rent a machine to dig a trench on either side so that the back yard would stop becoming a pond when it rained. I'm sure this wasn't a problem in the 60's when it was built, but over time the decaying leaves from my neighbor's tree raised the ground level by something like 1.5 ft and spoiled the original slope (I eventually found the original grade, there was a whole brick patio down there).

We may have to be a bit more intentional than "plant a bunch of trees" to get this effect, but I think it's worth exploiting.