Persistence of early growth of planted Picea mariana seedlings following clear-cutting and drainage in Quebec wetlands

A study was carried out to test the persistence of the early effects of forest drainage and planting position on the growth of black spruce (Picea mariana (Mill.) BSP) seedlings planted in eight drained forested wetland cutovers. Initial results, 2 years after planting, had shown that seedling response was most affected by planting position within the microtopography, and to a lesser extent, by distance to the drainage ditch. Persistence of these effects was tested by measuring the survival and growth rates of seedlings for an additional 4 years after planting. Increased growth owing to raised planting position was maintained over time. The small effect of distance to ditch on seedling growth observed after two growing seasons did not evolve into larger differences over time, and after 6 years there was no significant effect of distance to drainage ditch. Given the marginal growth improvements of black spruce seedlings planted closer to the ditch, drainage networks with narrow ditch spacing are not necessary on these site types after clear-cutting.