HR: 1340h
AN: B43A-0241    [Abstracts]
TI: Invasion By A Nitrogen-Fixing Tree Increases Decomposition Rates In Hawaiian Lowland Wet Forests: The Importance Of Stand-Level Controls
AU: * Hughes, R F
EM: fhughes@fs.fed.us
AF: Institute of Pacific Islands Forestry; USDA-Forest Service, P.O. Box 4370;60 Nowelo Street, Hilo, HI 96720 United States
AU: Uowolo, A L
EM: auowolo@fs.fed.us
AF: Institute of Pacific Islands Forestry; USDA-Forest Service, P.O. Box 4370;60 Nowelo Street, Hilo, HI 96720 United States
AU: Perry, C H
EM: chperry@fs.fed.us
AF: Institute of Pacific Islands Forestry; USDA-Forest Service, P.O. Box 4370;60 Nowelo Street, Hilo, HI 96720 United States
AB: Decomposition represents the primary pathway that fixed carbon and nutrients move from vegetation to soils; substantial changes to decomposition likely will have associated impacts on soil C storage and nutrient availability. We investigated how invasion by a non-native N-fixing tree, Falcataria moluccana - by increasing N and P inputs via litter fall and soil nutrient availability - altered decomposition processes in lowland wet forests growing on young lava flows of eastern Hawaii. We measured rates of mass loss and N and P dynamics for leaf litter of six native and non-native tree species common to Hawaiian forests. Initial litter quality of the six species varied considerably, with 2-, 4-, 5-, and 7-fold differences in leaf mass per area, %N, lignin:N, and %P values, respectively. Litterbags of each leaf litter type were placed in both native-dominated and Falcataria-invaded stands on a 300-year-old lava flow of Kilauea Volcano, and decomposition rates were determined over a one-year period. Leaf litter of 5 of the 6 species decayed twice as fast in Falcataria-invaded stands compared to native-dominated stands. Although decay rates varied among the 6 litter types within a given stand, significant differences were limited to litter types exhibiting the fastest (in the native-dominated forest) and slowest (in the Falcataria-invaded forest) decay rates, with the majority of litter types decaying at similar rates. Immobilization or release of N and P during decomposition was similarly affected by forest type; in most cases, substantially more initial N and P mass was released from a given litter type in invaded stands compared to native stands. However, such differences primarily were due to differences in mass loss between forest type; when initial N and P remaining were plotted against mass remaining, nutrient dynamics of a given litter type were similar between forest types, and distinct differences among litter types were apparent. While prior research emphasizes the importance of litter quality controls on decomposition, our results indicate strong stand-level (or site quality) controls on decomposition rates, with litter quality playing a more important role for nutrient dynamics during decomposition.
DE: 4806 Carbon cycling (0428)
DE: 4815 Ecosystems, structure, dynamics, and modeling (0439)
DE: 4845 Nutrients and nutrient cycling (0470, 1050)
SC: Biogeosciences [B]
MN: Fall Meeting 2005