Kelp forests in the eastern and northern Pacific commonly have complex three-dimensional structure, with many coexisting species. As in coral reefs, shading is a major mechanism of intra-specific and interspecific competition.ereocystis luetkeana often dominates northeastern Pacific kelp forests. It has a long stipe that is attached often to a small rock and is kept aloft by a gas-filled float. The fronds extend from the float. This makes for a very unstable arrangement and strong storms often uproot the plant.