PARENT SESSION
Poster Session #27: Nutrient Cycling I.
Tuesday, August 6. Presentation from 5:00 PM to 6:30 PM. Exhibit Hall B & C, TCC

Effects of N deposition on N cycling in annual grasslands of southern California.

SIRULNIK, ABBY^*,1, MEIXNER, THOMAS¹, ALLEN, EDITH¹, ¹ University of California at Riverside, Riverside, CA

ABSTRACT- The objective of this experiment was to study the effects of nitrogen deposition on litter decomposition and the variability and distribution of plant available nitrogen in annual grasslands that occur in areas historically dominated by coastal sage scrub. The study was conducted for two years at sites that occur at the high and low nitrogen (N) deposition ends of an air pollution gradient in southern California. Annual grass litter from the high deposition site had lower carbon to nitrogen ratios than grass litter from the low deposition site. Grass litter from the high N deposition site decomposed faster than litter from the low deposition site when decomposition occurred at the high deposition site or fertilized plots, but not on unfertilized plots. During the winter (rainy season), the high deposition site and fertilized plots at the low deposition site had significantly higher levels of soil extractable nitrogen than the low deposition site (unfertilized plots) in the top 10 cm. During the spring (growing season), there were no significant differences in the top 10 cm. The high deposition site had greater levels of N at a depth of 50 cm during the spring and at 75 cm during the winter, spring, and summer. The fertilized plots had greater N levels than the unfertilized plots at 25 and 50 cm during the winter and at 75 cm during all four seasons.

KEY WORDS: Nitrogen, Decomposition, Deposition, Grasslands