HR: 11:50h
AN: C41D-07    [PDF]
TI: Irreverent Soils: Nitrogen Dynamics In Taiga Forests During Winter
AU: * Kielland, K
EM: ffkk@uaf.edu
AF: Institute of Arctic Biology, University of Alaska, Fairbanks, AK 99775
AB: We measured annual net nitrogen mineralization, nitrification, and amino acid production in situ across a primary successional sequence in interior Alaska, USA. Net N mineralization rates during the growing season from green-up (late May) through freeze-up (late September) accounted for approximately 60% of the annual inorganic N flux, whereas the remaining N was released during the apparent dormant season. Nitrogen release during winter occurred primarily during October-January with only negligible N mineralization during early spring in stands of willow, alder, balsam poplar and white spruce. By contrast, black spruce stands also exhibited substantial mineralization after snow melt during early spring. The high rates of N mineralization in late autumn through early winter coincides with high turnover of fine root biomass in these stands, suggesting that labile substrate production, rather than temperature, is a major controlling factor over N release in these ecosystems. The results are consistent with the low temperature sensitivity of N mineralization previously documented for taiga soils, and demonstrate that measurements of soil processes restricted to the growing season may greatly underestimate annual flux rates of inorganic nitrogen in high-latitude ecosystems.
DE: 0400 Biogeosciences
DE: 1615 Biogeochemical processes (4805)
DE: 1851 Plant ecology
DE: 1863 Snow and ice (1827)
SC: Cryosphere [C]
MN: 2003 Fall Meeting