Germinable soil seedbanks in native pastures near Crows Nest, south-east Queensland

Abstract

The soil seedbanks in three patch types (tall grassland, short sward and lawn) were measured in native pastures near Crows Nest, south-east Queensland in two experiments. In the first experiment, seedbanks were measured at four sites, and in the second, the variation in seedbanks during the year was measured at one site. In each experiment the size and composition of the seedbanks were determined by germinating the seeds in soil samples. In the first experiment, total seed numbers ranged from ~6000 to 12,000 per m2. There were no significant differences between sites for total seeds or for seeds of any species group except legumes which comprised only a small portion of the seedbanks. There were significant differences between patch types for total seeds and for the following species groups, medium tussock grasses, short tussock grasses, stoloniferous grasses, legumes and forbs but not large tussock grasses and sedges. Total seed numbers, and those of medium tussock grasses, stoloniferous grasses and forbs were highest in the lawn patches and lowest in the short sward patches. Legumes had higher numbers in the tall grassland patches than in other patch types. In the second experiment, there were large differences between total seed numbers at the different sample dates (January, May, September and November). Numbers were highest in January and then declined throughout the year. This pattern was largely a reflection of the changes in numbers of forb seeds, the species group with the most seeds. There were no significant differences between patch types for total seeds but there were for medium tussock grasses, stoloniferous grasses, sedges and forbs. There was no relationship between the composition of the pasture sward and the composition of the seedbank for any of the three patch types. Twenty-eight species were allocated to persistent and transient seedbank types; all seedbank types occurred in all three patch types. The major species in the seedbanks were sedges (Cyperus gracilis, C. sesquiflorus), forbs (Gamochaeta spp., Paronychia brasiliana, Daucus glochidiatus) and Eragrostis spp.