HR: 09:15h
AN: H51A-06    [PDF]
TI: Effects Of Forest Roads On Internal Biogeochemical Pathways In Tropical Catchments
AU: Sidle, R C
EM: sidle@slope.dpri.kyoto-u.ac.jp
AF: Kyoto University, Geohazards Division, Gokasho, Uji, Kyoto, Kyoto, 611-0011 Japan
AU: Noguchi, S
EM: noguchi@affrc.go.jp
AF: Japan International Research Center for Agricultural Sciences, 1-1, Ohwashi, Tsukuba, Ibaraki, Ibaraki, 305-8686 Japan
AU: Rahim, N A
EM: rahimnik@frim.gov.my
AF: Forest Research Institute Malaysia, Kepong, Kuala Lumpur, 52109 Malaysia
AU: Ziegler, A D
EM: thaihawk@hotmail.com
AF: National University of Singapore, Department of Geography, 1 Arts Link, Kent Ridge, Singapore, 117570 Singapore
AB: Knowledge of the effects of forest roads on biogeochemical processes within headwater catchments is limited in the tropics. Hydrological response along with fluxes and yields of fine sediment ($<$ 250 mm) and dissolved nutrients (e.g., DOC and K+) were measured from a 50-m segment of logging road and the greater catchment (13 ha; harvested in winter 1999-2000) in Peninsular Malaysia during four consecutive storms in December 2002. Due to very low infiltration capacities, Hortonian overland flow was generated almost instantaneously on the road surfaces during the storm events. Maximum specific flux of sediment, DOC and K+ were observed during the fourth storm with the highest intensity, precipitation, and antecedent moisture: 5.15 kg/sec/ha, 473 g/sec/ha, and 465.81 g/sec/ha at the road segment; and 37.81 g/sec/ha, 53.27 mg/sec/ha, and 17.83 mg/sec/ha at the catchment outlet, respectively. The average enrichment ratio, i.e., road yield divided by catchment average yield on an unit area basis, for four storms was always greater than ten-fold (72.3, 16.1, and 12.4 for sediment, DOC, and K+, respectively), indicating the road surface produced disproportionately high amounts of those elements relative to the other parts of the catchment. The relatively high enrichment ratio for sediment relative compared to DOC and K+, suggests that subsurface and riparian sources also contributed to fluxes of dissolved nutrients. Furthermore, the enrichment ratio for DOC and K+ were generally higher during low intensity storms, indicating that a higher proportion of the catchment yield was attributed to roads, probably because the other parts of the catchment were not as hydrologically responsive. Thus, even for relatively small rain events with dry antecedent conditions, forest roads may alter internal biogeochemical pathways by acting as a source of dissolved nutrient and sediment (with adsorbed nutrients) and by redirecting natural hydrological pathways into the stream.
DE: 1800 HYDROLOGY
DE: 1803 Anthropogenic effects
DE: 1806 Chemistry of fresh water
SC: Hydrology [H]
MN: 2003 Fall Meeting