UPWASH AND DOWNWASH OF POLLEN AND SPORES IN THE UNSATURATED SURFACE-LAYER OF SPHAGNUM-DOMINATED PEAT

The vertical movement of Corylus and Cedrus pollen and of Lycopodium spores in Sphagnum and peat was studied in a factorial experiment with four flow regimes (no flow, downward, upward, alternate down and up), three injection depths (1, 5 and 9 cm below the surface) and three forms of packing (natural, hand-packed at natural density, haphazard). The experiment lasted for 36 d. The results were corrected for compaction and differential recovery of pollen and spores, but the main results were unaffected by these corrections. Downward, upward and alternating flows moved the median pollen position by about 1.5 cm during the experiment. The flows also increased the interquartile span by 2 cm: about 25% of grains moved at least 3 cm. The velocity of upward flow is probably more than sufficient to overcome the rate of sinking of pollen and spores in the unsaturated zone. Reversals of flow may be of importance in dislodging grains into the main channels again.