Aquatic Macrophyte Seed Bank in Lake Onalaska, Wisconsin. Long Term Resource211 Monitoring Program

摘要

Submersed aquatic vegetation, dominated by Vallisneria americana Michx., declined211u001edramatically in lake Onalaska (Navigation Pool 7, on the Upper Mississippi River) 211u001efollowing drought conditions in the late 1980s. Coinciding with the decline were 211u001emarked increases in the abundance of Myriophyllum spicatum L., particularly in 211u001eareas vacated by V. americana. Recent evidence indicates that much of the lake 211u001ehas remained unvegatated, by that since 1994, beds of V. americana have made a 211u001epartial recovery. While the prodution of vegetative propagules may largely 211u001eaccount for increases in populations of both species, the extent to which seed 211u001eproduction may contribute to their expansion in the lake is unknown. To assess 211u001ethe germination potential and distrubiton of the aquatic macrophyte seed bank in 211u001eLake Onalaska, sediment cores (5 cm deep) were collected from 74 sampling sites 211u001ein July 1995. Seedling emergence from sediments was observed in an environmental 211u001egrowth chamber operated at 25 C and a 14-hr photoperiod over a period of eight 211u001eweeks.