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Florida Lake Management Society Annual Conference, Naples, Florida, June 4 – 7, 2007

THE INFLUENCE OF WATER DEPTH AND VEGETATION MANAGEMENT ACTIVITIES ON GIANT BULRUSH IN LAKE OKEECHOBEE

Chuck Hanlon South Florida Water Management District, Lake Okeechobee Division West Palm Beach, FL

Controlled pond and greenhouse studies were conducted to evaluate the influence of water depth-on giant bulrush (Scirpus californicus) seed germination and establishment and the impact of herbicide treatments on mature bulrush. Seed germination and establishment were tested

under two inundation regimes using shaded and unshaded replicates. More were either placed at depths of 0, 10, 25 or 50 cm immediately, or seed germinate on exposed moist sediment before being inundated to test depth. observed predominantly in treatments with exposed substrate (0 cm). Only

than 2,400 seeds were allowed to Germination was 3 seedlings were

observed in the unshaded 10 cm treatment whereas inundations or the 10 cm shaded treatment. Bulrush was exposed throughout the study. Plants inundated

no germination was observed at deeper stem density was greatest when substrate to 50 cm at the slow inundation rate had

similar densities to those inundated cm produced the fewest density of

to 10 and 25 cm, whereas plants inundated immediately to 50 stems. Plant biomass and inflorescence density was greatest

for plants inundated to 0 cm and stem density, total plant biomass,

10 cm. Exposure to the herbicide Diquat significantly reduced stem height and the plants ability to produce seed. In the lake,

long-term monitoring of stem herbicide treatments have on changes in the areal coverage

density was used to further evaluate the effect water depth and bulrush. Remote sensing also was used to quantify temporal of bulrush along more than 30 km of shoreline. Similar to the

controlled

studies,

stem

density

tended

to

decrease

with

increased

water

depth

and

plants

treated

with Diquat required nearly a bulrush in Lake Okeechobee herbicide treatments.

year to recover to pre treatment is stressed by high lake stage,

densities. Results high turbidity and

indicate that exposure to

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NOTES

Session 7A – Page 7

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