Abstract: Average dry weight and nutrient levels in current foliage from red spruce and balsam fir seedlings and saplings in the understory of a 25-year old aspen and birch stand were observed 3 years after N, P, and lime treatments were applied. Elemental concentrations were plotted as a function of needle weight and quantity of element per needle. This allows interpretation of treatment effect on overall nutrient levels for both concentration and quantity of each element in the foliage. In balsam fir, dry weight per needle was significantly increased by N fertilizer. Nitrogen also significantly affected levels of ash, N, P, K, Ca, Fe, Mn, Zn, and Na in balsam fir foliage. In red spruce, dry weight per needle, N, and Fe levels all responded to N fertilizer; P fertilizer affected P foliar concentration and lime significantly affected Mn levels. In both species there were significant interactions among the N, P, and lime treatments, indicating that response to one element varied according to the other elements added simultaneously. Balsam fir needles were heavier and contained higher levels of nutrients than red spruce needles. The magnitude of changes in elemental levels was generally greater for balsam fir than for red spruce.

In the early 1980s there were several published reports of recent, unexplained increases in mortality of red spruce in the Adirondack Mountains and the northern Appalachian Mountains of the eastern United States. These reports coincided with documentation of reductions in radial growth of several species of pine in the southeastern United States, and with the severe, rapid, and widespread decline of Norway spruce, silver fir, and some hardwoods in central Europe. In all of these instances, atmospheric deposition was hypothesized as the cause of the decline. (Throughout this volume, we use the term "decline" to refer to a loosely synchronized regional-scale deterioration of tree health which is brought about by a combination of stress factors. These may be biotic or abiotic in nature, and the combinations may differ from site to site. ) Heated public debate about the causes and possible cures for these forest declines ensued. Through the course of this debate, it became clear that information about forest health and air pollution effects on forests was inadequate to meet policymakers' needs. Ecology and Decline of Red Spruce in the Eastern United States addresses that gap for eastern spruce fir forests and represents the culmination of a great deal of research conducted in recent years. The focus is on red spruce because the decline of red spruce was both dramatic and inexplicable and because of the great amount of information gathered on red spruce.