Plant diversity and the mechanism for its maintenance in tropical forests
热带森林植物多样性及其维持机制

It is well known that plant species diversity is highest in tropical forests. With regard to the mechanisms for the maintenance of tropical plant diversity, different hypotheses have been put forward, but until now, no convincing theory has appeared. Different researchers have obtained different conclusions , from which has arisen heated debate. This review discusses four mechanisms that are frequently invoked to explain the coexistence of the great number of plant species in tropical forests, these being Niche differentiation, Predatory pressure, Life history tradeoffs, and Lottery competition. Niche differentiation is evident from the non-random spatial distributions along micro-environmental gradients and plays an important role in sustaining high biodiversity. Pests reduce the survival and growth rate of seedlings near conspecific adults, thereby freeing space for other plant species. Pest pressure remains a promising but not widely proven mechanism for plant coexistence in tropical forests. Life history tradeoffs do occur a-mong tropical forest plants, and thus allow a large number of species to coexist. Suppressed by the canopy, understory plants rarely come into competition with one another, and chance becomes an important determinant of the recruitment of understory plants.