PARENT SESSION
Oral Session #42: Decomposition.
Presiding: K. Gross
Tuesday, August 6. 1:00 PM to 4:45 PM. Apache Meeting Room, TCC.
Direct and indirect effects of nitrogen fertilization on fungal growth and microbial enzymes in leaf litter decaying in a hardwood forest.
CARREIRO, MARGARET*,1, ECKARD-TRAMMELL, TARA1, LOVETT, GARY2, GRIFFIN, JACOB2, PATTERSON, SUSAN2, 1 University of Louisville, Louisville, KY2 Institute of Ecosystem Studies, Millbrook, NY
ABSTRACT- Nitrogen (N) deposition may affect litter decay rates indirectly by altering litter quality and soil microbial communities, and directly by increasing inorganic N availability in the forest floor. We conducted an experiment in New York's Catskill Mountains to determine the contribution of these three factors on decomposition by fertilizing sugar maple and beech plots for three years (50 kg N / ha / yr) and collecting litter from fertilized and unfertilized trees of each species. We placed leaves from both treatments in fertilized and unfertilized plots of their respective species. Litter in fertilized plots received two treatments, water and aqueous NH4NO3 (50 kg N / ha / yr) to separate effects of previous soil fertilization from additional current fertilization of litter and soil. Litter in the unfertilized plots received only water to determine microbial responses to litters from trees with different fertilization histories. We found that after decaying for 280 days fungal ergosterol concentrations in beech litter were depressed 33% by previously fertilized soil and current N treatment and by 33% to 54% in litter collected from fertilized trees compared with unfertilized trees. Ligninolytic enzyme activity was reduced 30% in beech litters decaying on previously fertilized soil and by current N treatment, and was 25% to 40% less in litter from fertilized trees compared with unfertilized trees. Maple litter from fertilized trees exhibited higher phosphatase activity suggesting microbes are phosphorus-limited.
KEY WORDS: decomposition, nitrogen, fungi, enzymes