Two-year-old red spruce (Picearubens Sarg.) seedlings were grown in a poorly buffered soil from a high-elevation site in the Great Smoky Mountains and exposed for 16 weeks to acid mist and rain chemically similar to that occurring at high-elevation sites in the southern Appalachian Mountains. Measurements of seedling growth, root distribution, saturated net photosynthesis, dark respiration, and nutrient content were made to test the hypothesis that acid deposition had caused reductions in the carbon economy noted at high-elevation sites in previous field studies. The role of base cation depletion in these changes was examined by evaluating soil amendments of Ca, Mg, or Ca plus Mg. Acidified rain and mist reduced (i) the apparent carbon economy of foliage, (ii) seedling growth, and (iii) rooting depth in these controlled greenhouse studies. Changes in gas exchange physiology paralleled responses observed for sapling trees in the field with increasing elevation and included both reduced net photosynthesis and increased dark respiration. Calcium deficiency induced by acid deposition is apparently an important mechanism underlying physiological responses of red spruce previously observed in the field. Calcium addition to soil partially reduced the effects of acid deposition, but observed responses suggest that both foliar- and soil-driven reactions are involved. Changes in carbon metabolism associated with reduced Ca availability, when high levels of acid deposition are superimposed on poorly buffered soils, support the inferential association of acid deposition with growth decline of mature red spruce in high-elevation forests of the Appalachian Mountains.

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Rates of net photosynthesis and dark respiration of red spruce (Picearubens Sarg.) foliage were examined in relationship to soil and foliar nutrient status at three elevations across each of three mountains in the southern Appalachians. These studies tested our previously stated hypothesis that increased dark respiration and reduced growth were associated with natural or induced nutrient deficiency at higher elevation sites. A consistent and highly significant reduction in the ratio of net photosynthesis to dark respiration was found at the highest sites on each mountain compared with lower sites, as had been previously reported for the initial two test sites. This response was produced by significant increases in dark respiration that were associated with low foliar calcium levels and high foliar aluminum levels found at the higher elevation sites in this region. Net photosynthesis was generally comparable between sites. A consistently inverse relationship between dark respiration and foliar calcium was found across highest and lowest elevation sites, while the midelevation sites, where calcium:aluminum ratios were highest, showed less evidence of respiratory response to calcium. Calcium in shoots was significantly reduced in association with increasing levels of soil aluminum in the rooting zone across all sites. Collectively, these studies suggest that reduced calcium supply, occurring in association with competitive inhibition of calcium uptake by high concentrations of aluminum found in soil, may have reduced the availability of carbon for red spruce growth at higher elevation sites. Inferential evidence examined, including atmospheric deposition levels, soil solution chemistry, and historical tree-ring chemistry, suggests that acidic deposition would have been a contributing factor in inducing or amplifying calcium deficiency.

Exploratory studies were initiated at two high-elevation red spruce (Picearubens Sarg.) stands in the Great Smoky Mountains of western North Carolina to document the magnitude and physiological basis of differences in tree growth at the two sites. Increment core data indicate that conditions have become relatively less favorable for mature trees at the upper site during the past 20 years and that annual height growth of sapling trees has been 40% less at that site compared with a similar site at an elevation 215 m lower. Seasonal measurements of net photosynthesis and dark respiration rates of saplings indicated that differences in sapling growth rates at the upper site were associated with increases in dark respiration and less favorable net photosynthesis:dark respiration ratios. Basal diameter increment was most closely associated with differences in current net photosynthesis rates among trees at the upper site, whereas height and diameter growth of the upper canopy related most closely to the net photosynthesis rate among lower-elevation trees. Reduced foliar calcium and magnesium, reduced foliar chlorophyll, increased foliar aluminum, and low ratios of calcium:aluminum were found at the upper site. Tissue and soil aluminum levels that are in the range of those associated with aluminum toxicity to red spruce provide a preliminary indication that current high atmospheric inputs of the strong anions SO4 and NO3 to acidic soils may be adversely affecting growth and physiology of trees at the high-elevation site.

Habitat valuation methods are most often developed and used to prioritize candidate lands for conservation. In this study the intent of habitat valuation was to inform the decision-making process for remediation of chemical contaminants on specific lands or surface water bodies. Methods were developed to summarize dimensions of habitat value for six representative aquatic and terrestrial contaminated sites at the East Tennessee Technology Park (ETTP) on the US Department of Energy Oak Ridge Reservation in Oak Ridge, TN, USA. Several general valuation metrics were developed for three broad categories: site use by groups of organisms, site rarity, and use value added from spatial context. Examples of use value metrics are taxa richness, a direct measure of number of species that inhabit an area, complexity of habitat structure, an indirect measure of potential number of species that may use the area, and land use designation, a measure of the length of time that the area will be available for use. Measures of rarity included presence of rare species or communities. Examples of metrics for habitat use value added from spatial context included similarity or complementarity of neighboring habitat patches and presence of habitat corridors. More specific metrics were developed for groups of organisms in contaminated streams, ponds, and terrestrial ecosystems. For each of these metrics, cutoff values for high, medium, and low habitat value were suggested, based on available information on distributions of organisms and landscape features, as well as habitat use information. A companion paper describes the implementation of these habitat valuation metrics and scoring criteria in the remedial investigation for ETTP. r