Topic 11.2: Site Preparation and Planting

Given that most forestry plantations are located on soils that are not suitable for intensive agriculture due to low fertility, droughtiness, or other factors, managers of short-rotation plantations are faced with the considerable challenge of maintaining and, if possible, improving site conditions.  As in natural forest management, maintenance of productivity in plantations requires avoidance of soil compaction and erosion. Also as in natural forests, most of the nutrients that are or will be available to plantation trees are located in the trees themselves, in litter, and in soil organic matter.  It is therefore critical to protect these stores of nutrients and to avoid other site damage, most of which occurs during harvesting, site preparation, and replanting operations, all of which are more intensive in plantations than in managed natural forests.  Avoidance of nutrient losses due to harvesting is particularly problematic where whole trees and not just bark-free boles are harvested.  Where bark, branches, and leaves are removed from the site, the nutrients taken with them have to be replenished.  Perhaps more difficult is replacing the other functions that the harvested biomass would eventually have performed as soil organic matter by helping to maintain soil structure and increasing soil nutrient-holding capacity.

Loss of nutrients and organic matter, as well as physical degradation of soil (e.g., compaction and erosion) need to be carefully monitored  and minimized in intensively managed  plantations.  The greatest site deterioration is associated with short-rotation whole-tree harvesting by clearcutting and yarding with heavy equipment (e.g., bulldozers) on steep slopes with wet soil.  When such harvesting practices are followed by windrowing (=pushing into linear piles) and burning of slash (=logging debris), future yields are likely to diminish substantially.  In addition to avoiding such treatment, site productivity can be enhanced by using cover crops to avoid inter-rotational surface soil exposure and interplanting with nitrogen-fixing trees.  Use of wind-breaks, minimum tillage site preparation methods, and judicious use of herbicides for weed control can also contribute to avoiding site deterioration.