Plant coexistence and the niche

How large numbers of competing plant species manage to coexist is a major unresolved question in community ecology. The classical explanation, that each species occupies its own niche, seems at first unlikely because most plants require the same set of resources and acquire these in a limited number of ways. However, recent studies, although few in number and incomplete in many ways, do suggest that plants segregate along various environmental niche axes, including gradients of light, soil moisture and root depth, and that partitioning of soil nutrients occurs, possibly through the mediation of microbial symbionts, some of which are more species specific than was previously thought. Although it is unlikely that niche separation along environmental axes is the only mechanism of coexistence in any large community, the evidence now suggests that it plays a more significant role than has been previously appreciated. More research into the consequences of various known tradeoffs is likely to uncover further cases of niche separation facilitating coexistence.