HR: 16:45h
AN: H34C-04    [Abstracts]
TI: Changes in Nutrient Concentrations After a Chaparral Wildfire
AU: * Meixner, T
EM: tmeixner@hwr.arizona.edu
AF: University of Arizona, Room 122B Bldg. #11 Hydrology and Water Resources, Tucson, AZ 85721 United States
AU: Fenn, M
EM: mefenn@attglobal.net
AF: USFS/PSW Riverside Forest Fire Laboratory, 4955 Cany0on Crest Drive, Riverside, CA 92507 United States
AU: Rademacher, L
EM: lrademacher@pacific.edu
AF: University of The Pacific, Geosciences 3601 Pacific Avenue, Stockton, CA 95211-000 United States
AU: Hogue, T
EM: thogue@seas.ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering, Los Angeles, CA 90095 United States
AU: Kong, H
EM: kongh@seas.ucla.edu
AF: UCLA, Department of Civil and Environmental Engineering, Los Angeles, CA 90095 United States
AU: Morissey, S
EM: skmbruin@excite.com
AF: California State University Los Angeles, Department of Geological Sciences 5151 State Univesrity Drive, Los Angeles, CA 90032 United States
AB: Wildfires and their biogeochemical consequences are not fully understood in western ecosystems. Since 1995 several watersheds in the San Bernardino have been monitored at varying frequencies and for varying chemical constituents. In the fall of 2003 several but not all, of these watersheds burned during the Old Fire. Since few treatment-control catchment scale studies exist for evaluating the consequences of stand replacing wildfire, the monitored streams of the San Bernardino Mountains offer a rare opportunity to investigate the biogeochemical impacts of wildfire. Previous studies on the effect of fire have generally used controlled or simulated wildfire burns. A few available studies use the approach presented here: serendipity. This study must rely on weekly and monthly baseflow samples of stream chemical composition due to the experimental design implemented for the control (unburned locations) in the pre-fire time frame. This sample frequency emphasizes baseflow and groundwater conditions within the catchments. The chemical data from baseflow conditions in the control and treatment catchments show no difference in the first year immediately post fire. However data during the second year post-fire indicate that nitrate and potassium concentrations in the burned watersheds were increased relative to the control catchments and the concentrations of other chemical constituents were relatively unchanged. These results highlight two important points about groundwater chemical response to wildfire disturbance, at least in the chaparral forests of southern California, and possibly the wider chaparral communities of the southwest. First, changes in nutrient concentration may have a significant time lag that will depend on the groundwater characteristics of the specific setting. Second, because of these time lags, the changes in dissolved load concentrations caused by wildfire might have their largest impact on stream water quality for a long time period.
DE: 1022 Composition of the hydrosphere
DE: 1030 Geochemical cycles (0330)
DE: 1632 Land cover change
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1845 Limnology (0458, 4239, 4942)
SC: Hydrology [H]
MN: Fall Meeting 2005