Boa Constrictor of the Plant World (U8)
The tall mound of tangled stems (cold weather) or foliage (growing season) that you see here consists entirely of Asian bittersweet, normally a climber of trees.
After starting as a delicate stem in the understory, the bittersweet stem latched onto surrounding plants to reach the canopy. In the more favorable light environment it became thicker and woody as it spiraled around the trunk of the host tree and sent out more stems.
The rotting tree trunk now enveloped by the mound was probably brought down by a very heavy load of stout bittersweet stems. Now that the host tree is down, there is so much available light that new bittersweet stems don't need to grow upwards anymore. They simply spiral onto each other close to the ground.
Like many other introduced plant species, the Asian bittersweet is an effective colonizer of recently disturbed ground. It produces abundant fruits that are attractive to birds and grows well in challenging soil conditions.