Effect of drainage and microtopography in forested wetlands on the microenvironment and growth of planted black spruce seedlings

Black spruce (Picea mariana (Mill.) BSP) seedlings were planted on eight drained forested wetland cutblocks to study the effects of soil type, distance from drainage ditch, and microtopography on the physical conditions of the rooting zone and on seedling growth, survival, and physiology. After two growing seasons, providing a raised planting spot had a greater impact on seedling growth than locally intensive drainage. Less saturated, better aerated, and warmer rooting zone on hummocks increased foliar N and Ca concentrations, which led to significantly greater relative growth rate, terminal shoot height growth, diameter, and survival compared with the seedlings in hollows. The effect of drainage on seedling growth is not conclusive. Depth of the aerobic layer and soil water content at 10 cm depth were similar at all distances to the ditch despite a significantly lower water table level in the 5-m plot. Thus, no significant differences were observed as a function of distance to drainage ditch for water relation and growth parameters except for better height growth in the 5-m plot the second year after planting. Water table levels were identical for both soil types and consequently growth was similar on wet mineral and organic soil types.