PARENT SESSION
Oral Session 96: Forest Ecology V: Soils and Nutrient Cycling.
Presiding: G Newman and S Bigelow
Thursday, August 5, 8:00 AM to 11:30 AM, Meeting Room B 114.

Effects of litter nutrients and soil nutrient availability on decomposition along an experimental fire frequency experiment in oak savanna.

Hernandez, Daniel^*,1, Hobbie, Sarah^*,1, ¹ University of Minnesota, St. Paul, Minnesota, USA

ABSTRACT- The relative influence of variation in litter nutrients and soil nutrient availability on decomposition and microbial processes are not well understood. This two-year study utilized a gradient in soil nutrient availability and litter nitrogen (N) content developed as a result of an experimental fire frequency experiment. We investigated the relative role of substrate and soil nutrient availability in the decomposition of oak (Quercus ellipsoidalis) litter and how variation in these nutrient pools affects microbial processes. Oak litter with a range in initial N concentration was placed in litterbags across the soil nutrient gradient. We also deployed a second set of litterbags that received treatments of fungicide, bactericide, or both to examine the effects of possible microbial interactions in decomposition. At the end of one and two growing seasons, we measured litter carbon, N, and phosphorous content, and litter microbial biomass. Soil nutrient availability was measured using ion exchange resin bags throughout the growing season. Initial analyses indicate that both litter stoichiometry and soil nutrient availability affected rates of decomposition. High-N litter decomposed significantly more quickly than low-N litter. Site nutrient availability was also positively correlated with rates of decomposition, and N immobilization was higher in sites with high soil N availability. Both decomposition and N immobilization declined in response to the fungicide application, suggesting that rates of decomposition of oak litter at these sites is highly dependent on the N immobilization performed largely by the fungal community.

Key words: soil N availability, fire, decomposition, microbe interactions