Principles of Nutrient Management for Sustainainable Forest Bioenergy Production

Nutrient management is an important part of ensuring sustainable forest production. Essential concepts for managing site nutrients are built upon considerable knowledge of soils, tree nutrient demands, and how these are impacted by silviculture, harvesting, and other management practices. Managers must first clearly define forest management objectives, and how bioenergy production or carbon dioxide (CO2) offset objectives might require special consideration. Managers must also examine how silviculture, harvesting, and other management practices might affect nutrient pools and availability. Soil fertility management practices are designed in response to these initial evaluation steps. Fertility management alternatives may include altering management practices that affect the distribution of harvested tree branches, foliage and tops, as well as involve addition of fertilisers, use of nitrogen (N) fixing plants, or the application of wood ash. When planting on sites with pre-existing nutrient deficiencies, it may be necessary to add nutrients in order to obtain merchantable tree growth over the short and long term. Nutrient management principles may also be required to minimise offsite impacts of management practices, for example, on water quality or climate change. Managers must determine what nutrients need to be applied to forested sites, appropriate amendment rates and their timing, and take into account the relationships among nutrients, soil, climate, and plant processes throughout the rotation. Soil and foliar analysis and the use of soil and plant bioassay tools can assist in these evaluations. Sustainable management practices require that nutrient control strategies also evaluate economic and energy balances, and that if necessary, management practices, including nutrient amendments, are modified to ensure that they are sustainable. Examples of forest nutrient management practices are described.