Economic aspects of sawmill residue use for tree seedling establishment on surface mines

Although the beneficial effects of bark mulch to tree seedling survival and growth on surface mines are well documented, its economic performance is less well established. The decision to use bark mulch 1n establishing tree seedlings on such harsh sites must involve consideration of both the anticipated biological gains and the associated costs. A stUdy was undertaken to examine the economic aspects of hardwood bark mulch use, over four growing seasons, with respect to Virginia pine and European alder seedling survival and height growth. For both species, average cost trends indicate that the added expense of applying bark mulch was more than offset by the increased survival attained. This was also observed for European alder height growth, but not for that of Virginia pine. Marginal costs indicate that different mulching rates may be desirable for different objectives. Where survival is of primary importance, no economic incentive exists for applying more than 2.5 em of bark. Where tree height growth is the parameter of interest, however, 5 crn of mulch is more economically attractive than 2.5 cm.