Dissolved ion analyses of stream water from bamboo forests: Implication for enhancement of chemical weathering by bamboo

抄録

Dissolved ion analyses of stream water were conducted monthly in three catchments of varying bamboo coverage of similar geological setting for one year. We found that the concentration of dissolved Si, non-sea salt Na, K, Mg, and alkalinity increased with the increase of bamboo coverage and we concluded that bamboo significantly contributes to chemical weathering. Based on the similar and constant Cl concentrations in stream water in the three catchments throughout the year, we simplified the system with respect to the evapotranspiration correction and basal runoff influence. Since calcite was not detected in the streambed sediment, non-sea salt Na and Ca are assumed to have originated from plagioclase, and thus the plagioclase weathering rate was calculated. The plagioclase weathering rate in bamboo forests was estimated to be more than 1000 mol ha^-1 yr^-1: twice as high as that in a control bamboo-free forest. The dissolved Si export rate of 0.11 mol/m²/yr from the two bamboo catchments is greater than that of bamboo-free catchment or reported data from rivers in other parts of the world. We discuss further the Si cycle in bamboo forests, comparing with that of bamboo-free forests.