Management Implications

Results from modeling efforts may also inform resource managers regarding the need for possible intervention and protective strategies to reduce or mitigate the impacts of air pollution. For example, forest sensitivity maps could be used to identify forest tracts where N or S loads remain above critical loads and where liming may be needed to sustain the health and productivity of forests. In recent decades, lime has been routinely applied to forests in Europe to counter pollution-induced losses of base cations, (e.g., Materna 2002, Meiwes 1995, Saarsalmi and Mälkönen 2001), and experimental trials in the United States have shown reductions in decline symptoms when sugar maple forests received lime applications (Long and others 1997, Moore and others 2000, Wilmot and others 1996). However, lime addition can be costly and difficult to apply over forest landscapes. Modeling results could help identify areas of particular vulnerability to Ca depletion and better target regions where interventions such as lime addition may be most beneficial and cost effective. Another management option is to modify harvesting intensity in particularly vulnerable areas by extending rotation lengths or limiting the biomass removed (stem only vs. whole-tree harvesting). A reduction in harvesting intensity could be used to lower the export of Ca from the forest during the time required for air pollution reductions to be achieved.