HR: 1340h
AN: B13C-0237    [Abstracts]
TI: The influence of mixed forest litters on decomposition processes affecting soil organic matter dynamics
AU: * Nicholson, V
EM: vtnicholson@ucdavis.edu
AF: University of California Davis, 1 Shields Ave Department LAWR , Davis, CA 95616 United States
AU: Horwath, W
EM: wrhorwath@ucdavis.edu
AF: University of California Davis, 1 Shields Ave Department LAWR , Davis, CA 95616 United States
AU: Wu, J
EM: wujianjun@zju.edu.cn
AF: University of California Davis, 1 Shields Ave Department LAWR, Davis, 95616
AU: Powers, R
EM: rpowers@czone.net
AF: University of California Davis, 1 Shields Ave Department LAWR, Davis, 95616
AB: The interaction among diverse plant litters during decomposition can influence processes that dictate soil organic matter (SOM) dynamics. Forest plantation management practices typically include the planting of singletree species and the removal of understory shrubbery. Understory removal is generally seen as a beneficial practice as it tends to reduce competition for moisture and nutrients. However, the elimination of understory species creates a monospecific litter environment that may affect microbial diversity and SOM dynamics. To identify potential mechanisms, we conducted a laboratory microcosm study of soils from two research plantations of ponderosa pine with understory present (UP) and understory absent (UA). Litter amendments were applied as pine-only (P) and pine-ceanothus mixtures (PC), uniformly labeled with 13C and 15N in a reciprocal-label design. This designed allowed us to partition all litter- and soil-derived C and N pools. There were significant interactions between vegetation history and litter amendment in C and N mineralization patterns with the net turnover of both soil- and pine-derived C and N in the P treatments compared to the PC treatments. Vegetative history influenced microbial activity and litter degradation. UP soils showed increased microbial respiration and extractable N but decreased litter mineralization (13CO2) and DOC as compared to the UA soils. Litter additions also influence C and N cycling especially in UA soils. Mixed litter additions increased microbial respiration and litter degradation while decreasing extractable N as compared to single litter additions in the UA soil. This suggests that mixed litters can increase microbial incorporation of important nutrients like C and N as compared to monocultures. These results suggest that plantation management may be improved by modifying the traditional monoculture approach to incorporate more diverse litter inputs.
DE: 1615 Biogeochemical processes (4805)
SC: Biogeosciences [B]
MN: 2004 AGU Fall Meeting