Relationships among Functional Properties of Californian Grassland

Abstract

ECOLOGISTS have become increasingly interested in general properties of communities and the relationships among species diversity, biomass, productivity, dominance and stability. Both verbal¹ and mathematical² models have been proposed to relate these properties. These models are important as initial generalizations in a developing predictive theory of ecology. The available data, however, are largely from planktonic systems and these data are contradictory. For example, Margalef³ has concluded from his extensive studies of marine systems that productivity and dominance are inversely related to stability and diversity. Increasing species diversity in the community leads to decreased dominance and productivity but increased stability. Patten⁴, however, has concluded that “high productive capacity is associated with high diversity” in summer plankton communities of Virginia's York River. Studies of grasslands on California's San Francisco peninsula, reported here, provide the first rigorous development of the relationships among diversity, dominance, productivity and stability of terrestrial communities. This report extends Margalef's general model to terrestrial systems and provides strong support for it as a valid description of general properties of communities.