Intensive Silvicultural Treatment: Impacts on Soil Fertility and Planted Conifer Response

The impacts of intensive silvicultural treatment on soil processes and fertility, as well as nutrition and growth of planted eastern white pine ( Pinus strobus L.) and white spruce [ Picea glauca (Moench) Voss] were examined 4 yr after planting and initial treatment. The impacts of three treatments, applied singly and in factorial combinations, were evaluated: (i) soil surface modification by scarification, (ii) fertilization, and (iii) vegetation control using herbicide. The most significant effects resulted from vegetation control. Nitrification increased significantly, soil total C and N declined, with accompanying decreases in soil pH and cation availability (K). With this same treatment, pine and spruce growth increased markedly in response to increases in light, moisture, and N. Scarification removed the nutrient reservoir in forest humus, resulting in decreased nutrient availability in the mineral soil, while fertilization had inconsistent effects on soil nutrient availability. However, neither scarification nor fertilization alone significantly affected growth; only their interactions with other treatments were important after 4 yr. During the period since planting, the effects of scarification and fertilization on conifer growth have declined, while effects of vegetation control have become much more prominent. The impact of losses of N and other nutrients as a result of vegetation control or scarification should become more evident as nutrient demand increases with plantation development.