Draining Forested Wetland Cutovers to Improve Seedling Root Zone Conditions

Depth to water table, thickness of the aerobic layer and soil water content were measured before and after digging one drainage ditch on each of eight waterlogged forested wetland cutovers in order to determine the effect of the distance to the ditch on seedling root zone conditions. Drawdown of the water table ranged from 23 cm at 3 m to 6 cm at 60 m from the ditch and was similar on mineral and organic soils. The ditch significantly lowered the water table up to a distance of 60 m where the water table was maintained below the 20 cm depth 25% more often than on the undrained control. Soil water content was reduced by drainage in the top 10 cm layer and the depth of the aerobic layer increased by 6 to 9 cm. This significant improvement of the soil moisture regime in the seedling rooting zone was similar at 7 and 40 m from the ditch, indicating that a dense ditch network may not be necessary to enhance seedling growth.