Reproductive Strategies in Herbaceous Plant Communities During Succession

Abstract

Reproductive strategies of herbaceous plants were analyzed in three successional communities. The communities were a 1—yr old—field, 10—yr old—field, and forest. Analyses included measurement of community—wide reproductive effort (reproductive dry wt/total dry wt) at 3—wk intervals throughout one growing season. Reproductive effort was highest in the 1—yr field. There was essentially no difference in reproductive effort between plants in the 10—yr old—field and forest communities; both exhibited relatively low reproductive effort. Reproduction in the 1—yr and 10—yr fields was highly synchronous; there was little synchrony of reproduction in the forests. This may indicate a more efficient utilization of resources throughout the growing season in the forest. Analyses also included measurement of numbers of seeds per plant produced by dominant species in each community. Number of seeds per plant in the 1—yr and 10—yr fields was relatively high, while number of seeds per plant was comparatively low in the forest. The ratio of root:total biomass increased with successional age, reflecting a proportionately larger expenditure of energy on competitive structures in the forest. Also, goldenrods, dominants in the 10—yr field, were found to possess 1 characteristic of an r—strategy (i.e., large number of small seeds) and a characteristic of a K—strategy (i.e., low reproductive effort). This apparent paradox was explained by relating these characteristics to the selective pressures that might produce them. In addition, the empirical data provide support for expanded concepts of reproductive strategies.