SUCCESSION OF A MACROPHYTE COMMUNITY IN A CONSTANT TEMPERATURE RIVER1

Abstract

The relationship of community metabolism to community structure in a 567‐m stretch of the spring‐fed San Marcos River, Texas, was studied during a period of autotrophic succession after a dredging operation. In general, plant biomass increased throughout the study period. Species diversity of submersed macrophytes increased sharply in the immature community, but there was a general decrease in diversity in the older community. Light intensity limited gross photosynthesis. An inverse relationship existed between photosynthetic efficiency and light intensity. The observed 29:1 ratio of plant surface area to streambed may be about optimum for maximum use of solar energy by the plant community. Community metabolism in the immature community fluctuated as differences in light intensity acted on low biomass and few species. As succession developed in the ecosystem with increase in species and biomass, ecological stability increased until only autotrophic conditions existed even under low light intensity.