freely. In many cases the mineral soil is intentionally exposed, encouraging germination by providing a moister seedbed than the leaves and needles that normally cover the forest floor. The severity of the cut depends on the species being targeted: fewer trees are removed for species that tolerate more shade, more trees removed for species that require more light. It is important that just enough light be given to establish the desired species, without inviting undesired species that require more light. In other situations, the undesired species is more shade tolerant than the desired species. In this case, foresters will forgo the preparatory cut (which might invite early germination of the undesired shade-tolerant) and perform a heavier than normal establishment cut, giving the desired species enough resources to establish and outgrow the undesired species. The (partial) overstory removal quickly follows, continuing to give the desired species the resources to outgrow its competitor. In the example below, the very shade tolerant balsam fir established in an earlier harvest, and is preventing the establishment of moderately shade tolerant eastern white pine. Overstory removal or partial overstory removal is performed to give more light to the established seedlings, allowing them to grow freely. This is the most important part of the shelterwood system because the site's resources are deliberately transferred from one generation of trees to the next. Without this cutting, seedlings will stagnate or even die as the crowns of the older trees grow. All the mature trees may be removed, or some may be left as reserves. These will continue to grow and may be harvested several decades later, or may be left to die of old age and contribute ecological values to the site. Shelterwood with reserves Keeping the shelterwood for a longer time than just the regeneration can be called the irregular shelterwood method, delayed shelterwood method, extended shelterwood method, shelterwood with reserves or reserve shelterwood. It maybe done to get additional growth on the overwood trees to get extra-large diameters for woods for speciality purposes and products. It also enhances the scenery and is important for some biota. There may be ecological and social needs wanted at a landscape level mitigating for their retention. Femelschlag When this series of treatments is performed across an entire stand, it is called a uniform or regular shelterwood. Irregular shelterwoods take a variety of forms, and are becoming increasingly popular on small woodlots