Due in part to their fast growth and large size, these pioneer tree species provide important structure and function, for example, in food web dynamics, nutrient cycling, erosion control, and as a habitat for fish (as trees and branches fall into the river) and wildlife.
There’s that old saying that no man steps into the same river twice. This is very true; rivers are naturally dynamic, and the streamside, or riparian, plant species that live along their banks have adapted to the ever-shifting landscape that results from cycles of flooding and summer drought.
Periodically, though, the path of the river shifts dramatically, and a bend of the river channel gets cut off and abandoned by the main flow of water (see time lapse images below). The result of both processes is the creation or renewal of patches of cleared land, upon which new vegetation can germinate and grow. In some bends in the river, the river moves a little bit each year, eroding the outer bank and growing the inner one (called a point bar).
On this cleared land along both the main channel and the abandoned channels of a river, the new plants that begin to grow are typically good pioneers the early arrivers that have strategies to deal with lots of environmental stresses.