Abstract
The shift in dominant species with time in grasslands has been a major concern of studies of grassland ecology. In this article, I reviewed the two theories which have been recently proposed to explain successional changes in component species in grasslands by the two plant ecologists, Tilman and Berendse. The both theories are based on the same assumption that the changes in dominant species are caused by the changes in resource environments and the differences in growth response to resource availability among species. However, the two theories differ in the underlying biological factors responsible for the changes in dominant species in grasslands. TILMAN suggested the trade-off between root and shoot functions as a critical factor causing changes in dominant species, whiles BERENDSE suggested the trade-off between biomass productivity per unit nitrogen and nitrogen loss rate per unit biomass. These theories seem to be useful in explaining the changes in the component species from tall grasses to short grasses or Zoysia species in Japanese swards.
