BASIC DECISIONS AND PRINCIPLES IN FOREST MANAGEMENT The implementation of a silvicultural system involves a number of decisions on the type of operations to employ at the various phases of the development of a stand or group of trees. These operations can affect one or more key stand variables, such as tree species composition, stand density and age structure, stand edges, or site conditions, which in turn influence the provision of a range of ecosystem services. Furthermore, within any given FMA, a particular criterion of sustainability (e.g., aspects of biodiversity, public preference for forest landscapes) may vary with different stages of tree growth.