Planting and fertilizing trees are investments in the next commercial stand, not reinvestments in the forest. They are investments in a potential product. We do not reinvest in maintaining the health of biological processes because we do not see the forest, only the commercial product. We do not reinvest because we insist that ecological variables are really constant values that we need not consider. Before I can answer this question, you must understand that all things in Nature's forest are neutral when it comes to any kind of human valuation.
Nature has only intrinsic value.
Consider, for example, the coniferous forests of the Pacific Northwest in which Douglas fir and western hemlock predominate in the old- growth canopy. Herein lives the spotted owl, which preys on the flying squirrel as its stable diet. The flying squirrel, in turn, depends on truffles, the below-ground fruiting bodies of mycorrhizal fungi. Flying squirrels, having eaten truffles, defecate live fungal spores onto the forest floor, which, upon being washed into the soil by rain, inoculate the roots of the forest trees. These fungi depend for survival on the live trees, whose roots they inoculate, to feed them sugars, which the trees produce in their green crowns.