Leaching of dissolved and particulate phosphorus via preferential flow pathways in a forest soil: An approach using zero‐tension lysimeters

Phosphorus (P) fluxes from forest soils are not well understood. For temperate zone forests, there is some evidence from watershed studies that P export occurs mainly in preferential flow pathways during storm events after dry periods. Therefore, we tested the practical applicability of a sampling approach, which should allow for quantifying P concentrations and fluxes. We used zero‐tension lysimeters, which were installed beneath the topsoil and in the subsoil at plots in the Tharandt Forest (Saxony, East Germany). Two storm events after dry periods were simulated by means of experimental sprinkler irrigation. Preferential flow water collected with the zero‐tension lysimeters was analyzed for total P (TP), particulate P (PP), dissolved organic P (DOP) and dissolved inorganic P (DIP), and the respective P fluxes were calculated. The results indicate that the experimental approach is applicable to estimate fluxes of different P fractions in preferential flow. Measured data point toward a distinct flushing of P in the first hours of heavy rainfall events with PP fraction playing a dominant role. In general, P concentrations decreased quickly during the first 2 h of irrigation and then remained constant. Initial concentrations and cumulative fluxes were highest in the subsoil samplers. For a better understanding of underlying processes, further research with a special focus on the PP fraction is necessary.