title: Responses of soil nitrogen dynamics in a Mojave Desert ecosystem to manipulations in soil carbon and nitrogen availability.
abstract: We investigated the effects of changes in soil C and N availability on N mineralization, nitrification, denitrification, NH(3) volatilization, and soil respiration in the Mojave Desert. Results indicate a C limitation to microbial N cycling. Soils from underneath the canopies of Larrea tridentata (DC.) Cov., Pleuraphis rigida Thurber, and Lycium spp. exhibited higher rates of CO(2 ) flux, lower rates of NH(3) volatilization, and a decrease in inorganic N (NH(4)(+)-N and NO(3)(-)-N) with C addition. In addition to C limitation, soils from plant interspaces also exhibited a N limitation. Soils from all locations had net immobilization of N over the course of a 15-day laboratory incubation. However, soils from interspaces had lower rates of net nitrification and potential denitrification compared to soils from under plant canopies. The response to changes in C availability appears to be a short-term increase in microbial immobilization of inorganic N. Under controlled conditions, and over a longer time period, the effects of C and N availability appear to give way to larger differences due to spatial location. These findings have implications for ecosystems undergoing changes in soil C and N availability due to such processes as desertification, exotic species invasions, or elevated atmospheric CO(2) concentration.
authors.affiliation: 601 Science and Engineering Building, University of Arkansas Stable Isotope Laboratory, University of Arkansas, Fayetteville 72701, USA. smschae@uark.edu
authors.forename: S M
authors.initials: SM
authors.lastname: Schaeffer
authors.forename: S A
authors.initials: SA
authors.lastname: Billings
authors.forename: R D
authors.initials: RD
authors.lastname: Evans
mesh_terms: D000641:Ammonia / Q000032:analysis; D001682:Biological Availability; D002140:California; D002244:Carbon / Q000032:analysis* / Q000378:metabolism*; D002245:Carbon Dioxide / Q000032:analysis; D003889:Desert Climate; D017753:Ecosystem; D009584:Nitrogen / Q000032:analysis* / Q000378:metabolism*; D012987:Soil; D012988:Soil Microbiology; D014835:Volatilization
chemical_list: D012987:Soil; D002245:Carbon Dioxide; D002244:Carbon; D000641:Ammonia; D009584:Nitrogen