As you enter the south meadow, there used to be a spot where the arboretum piled debris like tree limbs, dug-up blackberries, etc. Once the pile got to a certain size, and it was the right time of year, they would burn it. The last time I remember them burning anything, it was about 3 or 4 years ago. Sizable burn piles, such as the one that happened here, basically bake the ground because of the intense heat created. Essentially, this kills all of the plants and destroys the soil's ecosystem. The first plants that reestablish the spot are usually nonnative species. In this case, Himalayan blackberry, teasel, and a species of thistle dominate this area.
These areas will start to grow larger. Blackberries can easily create dense thickets and shade out other plants. There are plenty of examples of blackberries creating impenetrable thickets around the arboretum, especially along the river bank. Teasel is a biennial and can quickly spread out of control. In the second photo below, you can see the dense mat being created that will hinder other plants from growing. Parts of the south meadow are already covered with thick stands of teasel.
I’ve seen this phenomenon occur where the forest service has burned huge slash piles in places where they have been thinning the trees. I don’t know if they still use this practice.
These areas require a considerable amount of effort to restore, so it is best to avoid creating them.
Note
Sorry I haven’t posted more lately. I’ve been a little under the weather.
