INVESTIGATION OF ACID DEPOSITION EFFECTS ON SOUTHERN APPALACHIAN RED SPRUCE (Picea rubens) BY DETERMINATION OF CALCIUM, MAGNESIUM, AND ALUMINUM IN FOLIAGE AND SURROUNDING SOIL USING ICP-OES

Abstract

Red spruce (Picea rubens) are conifers found at high elevations (above 1370 m) sites in the Southern Appalachian Mountains. A decline of red spruce forests in the Southern Appalachian Mountains caused by atmospheric acid deposition has been reported since the 1970s. Acid deposition leaches essential nutrients (calcium and magnesium) out of the soil and increases the availability of toxic metals (aluminum) to plants. Acid deposition effects on red spruce forests were investigated by determining aluminum, calcium, and magnesium in foliage and surrounding soils using inductively coupled plasma optical emission spectrometry (ICP-OES). There was some correlation in nutrient or toxic metal concentrations found in the foliage or surrounding soils of red spruce trees with respect to elevation and geography of red spruce forests located in the Southern Appalachian Mountains. The majority of the results indicated that foliar nutrient or toxic metal concentrations from red spruce trees did not correlate with soil metal concentrations. Life stage of red spruces trees were independent of foliar or soil metal concentrations. A previously developed model using soil calcium/aluminum molar ratios suggested that almost all sample sites located in the Southern Appalachian Mountains are at high risk of adverse forests health effects. A comparison of red spruce sapling foliar calcium/aluminum ratios at Clingman's Dome, North Carolina/Tennessee, suggested a possible improvement since the 1980s in red spruce forest health. A comparison of sapling red spruce foliar calcium and magnesium concentrations with previous studies, which spanned 40 years, at Richland Balsam, North Carolina, suggested an improvement in red spruce health since 1994.

Keywords:

• acid deposition
• aluminum
• Blue Ridge Parkway
• calcium
• exchangeable cations
• foliage
• Great Smoky Mountains National Park
• ICP-OES
• inductively coupled plasma optical emission spectrometry
• magnesium
• Mount Mitchell State Park
• Picea rubens
• red spruce
• Southern Appalachian Mountains

ACKNOWLEDGMENTS

The ICP-OES instrument employed in this research was partially funded by an award from the National Science Foundation Division of Undergraduate Education (NSF Award 995022 CCLI-A & I). The authors would like thank Dr. Thomas Martin for his assistance with the statistical analysis and Luke Wilson for his help with sample collection.

Notes

CD, ML, and SM are located within the Great Smoky Mountains National Park (NC/TN); RB, WRK, and YF are located on the Blue Ridge Parkway (NC); MM and CA are located in the Mt. Mitchell State Park (NC).

^a All concentrations in µg/g.

MA = mature; SP = saplings; SE = seedlings.

Follow Hypothesis : Higher elevation sites were expected to exhibit lower nutrient (Ca & Mg) concentrations and higher toxic metal (Al) concentrations due to acid deposition.

Reject Hypothesis : Higher elevation sites have higher nutrient (Ca & Mg) concentrations and lower toxic metal (Al) concentrations.

Statistically the Same : Higher elevation sites have the same nutrient (Ca & Mg) concentrations and the same toxic metal (Al) concentrations.

^a All concentrations in µg/g.

Follow Hypothesis : Western sites were expected to exhibit lower nutrient (Ca & Mg) concentrations and higher toxic metal (Al) concentrations due to acid deposition.

Reject Hypothesis : Western sites have higher nutrient (Ca & Mg) concentrations and lower toxic metal (Al) concentrations. Statistically the Same : Western elevation sites have the same nutrient (Ca & Mg) concentrations and the same toxic metal (Al) concentrations.

*Based on the model developed by Cronan and Grigel.^{[ 22 ]}

NR* = No standard deviation reported.