Phosphorus retention in streams draining pine and hardwood catchments in the southern Appalachian Mountains

SUMMARY. 1. This study was designed to determine how catchment use affects stream phosphorus retention by comparing retention in streams draining three mixed hardwood catchments and three catchments that were planted in white pine in the 1950s.
2. Catchments of similar area and stream discharge were chosen and phosphorus uptake was measured monthly in each catchment along with temperature, discharge, velocity, coarse particulate organic matter (CPOM), fine particulate organic matter (FPOM), and microbial respiration associated with FPOM.
3. On an annual basis, average phosphorus retention was not different between streams draining pine and hardwood catchments nor were there significant differences between physical (temperature, velocity and discharge) or biological (CPOM, FPOM and respiration) parameters based on catchment type. However, discharge was more variable in streams draining pine catchments.
4. Because phosphorus uptake was correlated with discharge, phosphorus retention was also more variable in streams draining pine catchments. Storms caused a greater increar.e in discharge and loss of phosphorus in pine streams than in mixed hardwood streams, but discharge returned to baseline more quickly in pine streams.
5. We suggest that discharge regimes and phosphorus dynamics of streams draining pine catchments are less resistant to change but more resilient than streams draining mixed hardwood forests.