Preliminary results of afforestation of brackish sludge mounds

High population density and intensive use of land in Flanders (Northern Belgium) have resulted in a shortage of land to dump dredged sediments. In search of an area efficient solution, a mound was constructed and afforested; 50-114% more dredged sediment per unit area could be discarded by constructing mounds with a height of 6.6 m compared to conventional disposal sites. To prevent erosion, the mound was afforested. Preliminary results of tree growth and changes in soil conditions are demonstrated. Tree survival and height growth are highest in the dominant wind direction sc. the SW-NE axis. On the slopes, parallel with the dominant wind direction, tree mortality up to 80% was observed. The increase of the soil organic carbon content from 3.1 to 3.8% could be partly put down to the growth of tree roots. This increase in organic carbon has far-reaching consequences for potential soil sanitation. The high amount of CaCO₃ in the soil protects the mound from internal or external acidification for the next centuries. After four growing seasons, electric conductivity was reduced to the threshold for salt sensitive plants.