SEED BANKS AND VEGETATION OF 3 CONTRASTING SITES IN AN URBAN EUCALYPTFOREST RESERVE

Grass species, sedges and dicotyledons in the vegetation and the burie d germinable seed of a natural subtropical eucalypt forest, a mown and a road bank site were identified in four consecutive seasons and the data peeled to give a more precise assessment of taxa present each yea r. Differences in the relative proportions of taxa, differences in spe cies density, origin and life history of grass species in the seed ban k and vegetation, as well as differences in biomass and rate of germin ation of buried germinable grass seed, in the three sites were investi gated. In all three sites, grasses were the dominant taxa of the groun d stratum of the vegetation with each site having its own group of mai nly perennial grasses. The seed banks were dominated by grasses in the forest site, sedges in the mown site and dicotyledons in the road ban k site. There were significant differences in species density of grass es in both the vegetation and buried germinable seed between sites, wi th the forest site having a significantly lower species density in its seed bank than the mown and road bank sites, and the vegetation of th e forest and mown sites having a lower species density than the road b ank site. However, there was a high correlation between the grass spec ies of the vegetation and the buried,germinable seed in each of the th ree sites - the species which dominated the vegetation also dominated the biomass of buried germinable seed in each site. The mown and road bank sites had larger numbers and biomass of buried germinable grass s eed than the natural forest site. There were no differences in the num ber of days to first germination and the number of days to 50% germina tion of the buried germinable seed between any of the sites. Exotic gr ass species were present in the seed banks of the forest, mown and roa d bank sites. Exotics were prevalent in the vegetation of the mown and road bank sites but not evident in the vegetation of the forest site. Exotic species with higher buried germinable seed numbers and similar germination rates to the native species are likely to have a competit ive advantage over the native species. It appears that the mown and ro ad bank sites, may net as reservoirs for the more competitive exotic g rass species, enabling them to invade the seed banks of the forest are as.