Soil seed banks and post‐fire seed deposition across a forest ‐ fynbos ecotone in the Cape Province

Abstract

Abstract. The relative sizes and composition of soil seed banks, the influence of fire and the post‐fire deposition of seeds were investigated in a riparian forest and adjacent fynbos and transitional vegetation in Swartboskloof. Brief complementary studies of soil seed banks were conducted in poorly‐developed forest and scree forest soils. Numbers of species in each vegetation type were very similar, but there were fewer seeds in riparian forest soil than in the transitional and fynbos zones. These patterns were not repeated in poorly‐developed forest and scree forest. No effects of fire on soil seed banks were detected. Forest soil had relatively large numbers of seeds stored at 10 to 15 cm deep, with many zoochorous and few myr‐mecochorous seeds. Anemochorous and ornithochorous seeds of forest species formed a major component of seed deposition within the transitional and fynbos zones in the first year after fire. The numbers of anemochorous forest seeds in the fynbos declined with distance from the forest edge. The deposition of ornithochorous forest seeds was less closely related to distance from the source, and was not exclusively associated with the presence of tall or fruit‐bearing shrubs. Regeneration after canopy‐destroying disturbance in the forest is likely to emanate from the soil seed banks of pioneer species which now or previously occurred on forest margins. Seed availability does not appear to limit colonization of fynbos by forest species soon after fire.