Document Type

Article

Journal/Book Title/Conference

Water, Air, Soil and Polution

Volume

85

Issue

3

Publisher

Springer Verlag

Publication Date

1995

Keywords

acidic deposition, ecosystem processes, nitrogen saturation, high elevation, southern Appalachian watershed

First Page

1647

Last Page

1652

Abstract

High-elevation red spruce-Fraser fir forests in the Southern Appalachian mountains: 1) receive among the highest rates of atmospheric deposition measured in North America, 2) contain old-growth forests, 3) have shown declines in forest health, 4) have sustained high insect-caused fir mortality, and 5) contain poorly buffered soils and stream systems. High rates of nitrogen and sulphur deposition (sim1900 and sim2200 Eq·ha–1·yr–1, respectively) are dominated by dry and cloud deposition processes. Large leaching fluxes of nitrate-nitrogen (100–1400 Eq·ha–1·yr–1) occur within the soil profile. We have expanded the study to the watershed scale with monitoring of: precipitation, throughfall, stream hydrology, and stream chemistry. Two streamlets drain the 17.4 ha Noland Divide Watershed (1676–1920m) located in the Great Smoky Mountains National Park. A network of 50 20x20 m plots is being used to assess stand structure, biomass, and soil nutrient pools. Nitrate is the predominant anion in the streamlets (weighted concentrations: 47 and 54 mgreq·L–1 NO3 –; 31 and 43 mgreq·L–1 SO4 2–). Watershed nitrate export is extremely high (sim1000 Eq·ha–1 yr–1), facilitating significant base cation exports. Stream acid neutralizing capacity values are extremely low (–10 to 20 mgreq·L–1) and episodic acidifications (pH declines of a full unit in days or weeks time) occur. Annual streamwater sulfate export is on the order of 770 Eq·ha–1yr–1 or about one-third of total annual inputs, indicating there is net watershed sulfate retention. The system is highly nitrogen saturated (Stage 2, Stoddard, 1994) and this condition promotes both chronic and episodic stream acidification.

Comments

Originally published by Springer Verlag. Author's PDF and HTML fulltext available through the author's website. Note: Article originally appeared in Water, Air and Soil Pollution.

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