Seasonal Phosphorus Dynamics in a Forest Stream Water Following Different Harvests

Even small changes in phosphorus concentrations in stream water could cause eutrophication because of very low level of phosphorus concentrations in natural waters. I investigated the impact of strip cut and clear cut on phosphorus concentrations in stream water at the Hubbard Brook Experimental Forest and investigated stream water phosphorus concentrations as a function of flow rate and season (as well as cutting history). Mean phosphate concentrations in the control (undisturbed forest) increased $1.9{\mu}g\;L^{-1}\;to\;2.6{\mu}g\;L^{-1}$, while strip cut treatment increased phosphate concentrations in stream water $2.2{\mu}g\;L^{-1}\;to\;3.7{\mu}g\;L^{-1}$ during the same period. There was no significant effect of clear cut treatment on phosphate concentrations in stream water. No relationships were found between discharge rate and phosphate concentrations, but the magnitude of fluctuation were increased during two decades in undisturbed forest: $1-5{\mu}g\;L^{-1}$ from 1963 to 1975 and $1-12{\mu}g\;L^{-1}$ from 1983 to 1995. Based on this study, forest harvests with buffer zone will not make a problem by imported phosphate to cause eutrophication in natural water.