Influence of higher rain intensities on phosphorus movements in the upper half meter of macroporous clay soil

摘要

In climate change scenarios, the frequency of high-intensity rain events in Sweden is assumed to increase. In a plot experiment at Ultuna, Uppsala, the influence of rain intensities on phosphorus (P) transport in the uppermost 0.5 m of a clay soil was studied at 16 locations. A rain simulator, 0.5 x 0.5 m and mounted 1 m above the soil surface, was used to simulate 85-500 min rain sequences causing small (4-9 mm h(-1)) and large (22-28 mm h(-1) and one extreme at 37 mm h(-1)) steady water fluxes (intensity) in the underlying soil profile. Water percolated to a zero-tension collector tray at 0.5 m depth where drain water and its sediment load was sampled at discrete time intervals. The total P (TP) mass flux ranged, at low intensity, between 12-92 mu g m(-2) min(-1) (average 28.1 mu g m(-2) min(-1)) and, at high intensity, between 83-375 mu g m(-2) min(-1) (average 168.5 mu g m(-2) min(-1)) and 648 mu g m(-2) min(-1) at the extreme intensity. The soluble reactive (inorganic) P (SRP) mass flux ranged, at low intensity, between 1-65 mu g m(-2) min(-1) (average 10.0 mu g m(-2) min(-1)) and, at high intensity, between 6-205 mu g m(-2) min(-1) (average 47.9 mu g m(-2) min(-1)) and 495 mu g m(-2) min(-1) at the extreme intensity. Thus, in the intensity range 4-28 mm h(-1), TP and SRP increased, on average, by approximately 12% (mu g m(-2) min(-1)) per unit increase in intensity (mm h(-1)). The results of this study demonstrate increased sediment and P loss/mobility for clay soil under increased precipitation intensity predicted under climate change.