Species Richness of Plant Communities: Relationship With Community Growth and Structure

The species richness of the overstorey of plant communities, receiving maximum solar radiation for the region, is correlated with the annual growth rate of that stratum. The species richness of the understorey is influenced firstly by the amount of solar energy transmitted through the overstorey and secondly by the proportion of community photosynthates translocated to inflorescence and seed production in that stratum. In plant communities where an overstorey is reduced or absent, the growth form of the ground-stratum plants will determine the proportion of the community photosynthates translocated to flower and seed production. Only a small proportion of community photosynthates will be directed to seed production in plant communities with shrubby understoreys. In savanna communities, overgrazing will convert the ground stratum from a perennial tussock grass growth form either to a rhizomatous, lawn-like growth form or to an annual growth form. In semiarid to arid environments, the annual growth...