Tuesday, November 6, 2007
215-8

Does Acid Deposition Affect Nutrient Dynamics in Forest Leaf Litter?.

Prinith Munasinghe1, Kathryn Piatek1, William Peterjohn2, and Mary Beth Adams3. (1) Division of Forestry and Natural Resources, West Virginia Univ., Percival Hall, PO Box 6125, Morgantown, WV 26506, (2) Department of Biology, West Virginia Univ., 5214 Life Sciences Bldg, P.O. Box 6057, Morgantown, WV 26506, (3) USDA-FS (Forest Service), Timber & Watershed Laboratory, PO Box 404, Parsons, WV 26287

To understand the effects of acid deposition on nutrient dynamics in foliar litter, we carried out a litter decomposition study at the long-term soil productivity study at the Fernow Experimental Forest in West Virginia. Acid deposition was simulated by ammonium sulfate additions and treatments were whole tree harvest (control), whole tree harvest plus ammonium sulfate additions (ammonium sulfate), and whole tree harvest plus additions of both ammonium sulfate and dolomite (lime).
Mass loss of litter at the end of first twelve months was significantly affected by treatments (p = 0.0442). The rate of mass loss was significantly higher in the control than in the lime treatment. At twelve months, carbon content in the control was significantly lower than in the lime and ammonium sulfate treatments. It appears that carbon in leaf litter of lime and ammonium sulfate treatments had a longer residence time. Throughout the twelve months of decomposition, calcium mineralized in all treatments. Calcium content at twelve months, was significantly lower (p<0.0001) in the control than in the ammonium sulfate treatment. 
The rate of net nitrogen immobilization in the first seven months was lower  in the ammonium sulfate treatment than in other treatments and it was significant at six (p=0.0122) and seven months (p=0.0019). Forest productivity may be affected by acid deposition (ammonium sulfate treatment), as nitrate leaches from soil together with basic cations, such as calcium. Phosphorus content at the end of twelve months was significantly affected by treatments (p<0.0001). Phosphorus immobilized throughout the twelve months of decomposition in the ammonium sulfate treatment but, in both control and lime treatments phosphorus immobilized only during the first seven months and mineralized at twelve months. It appears that acid deposition influence increased phosphorus immobilization during litter decomposition and thereby may limit phosphorus availability for forest tree growth.