Running bamboo is notoriously fast spreading and difficult to remove. What keeps its population balanced in the wild, and prevents it from crowding out the competition? I tried googling, but was inundated with gardening advice, horror stories, and assault / offensive gardening (some of the latter two presumably covering the same incident from both sides). My google-fu failed, I couldn’t really find any info about natural population controls of running bamboo in the thicket of tall tales and gardening advice.
It is the same as other easily spreading plants. In their native habitats there are checks like diseases and predators. When you move them out of those habitats they can thrive at a new level because of the lack of those things.
Do they eat enough to kill it and the root system off? My understanding is if the roots survive they just keep spreading anyway?
Leaves/shoots are where the energy comes from. If they get destroyed enough the root will die. Usually gardeners just aren’t that patient.
Not only diseases and predators keep them in check, there are also other plants that can effectively compete with them in their native range too
Bamboo is monocarpic (true bamboo at least.). The huge clonal colony flowers once and dies, even below ground. The seeds that fall grow the next generation.
Bamboo species tend to all flower at the same time at the end of a years or decades long cycle. This bottlenecks how much it can spread clonally (underground roots) but gives it another method to spread.
Rats, mice, and other rodents eat the seeds, so there is some ecosystem regulation already
Places with good habitat but no native bamboos like Hawaii have really bad problems with colonies taking over huge areas