The upper and lower limits of the distribution of mature Avicennia marina lie between mean high water and mean sea level m open estuaries in southeastern Australia. Newly established seedlings are highly variable in abundance, but are rarely found in the saltmarsh or on mudflats. Their distribution is unlikely to be limited by dispersal because propagules disperse into the saltmarsh and to intertidal mudflats, but their establishment may be hmited by physicochemical conditions, interspecific competition and predation.The model that physicochemical conditions control the mtertidal limits of establishment of seedlings was accepted for propagules stranding in the saltmarsh but rejected for those stranding on mudflats. No seedlings established on saltmarsh sediments but similar numbers of seedlings established within light gaps in adult mangrove stands and on intertidal mudflats. The model that interspecific interaction with freelivmg macroalgae (Hormosira banksii) reduces the establishment of seedlings on mudflats covered with macroalgae or in stands with a ground cover of macroalgae was accepted. Under controlled conditions five times as many propagules established on cleared ground compared with ground covered with macroalgae. Predators also reduce seedling establishment, but the model that they preferentially act on propagules stranding on the mudflat was rejected. The low number of seedhngs found on mudflats without macroalgae appears to relate to wave and current efFects on establishment and the efFects of waterlogging or fouling on survival.

We examined relations between vegetation and soils, using multivariate methods, in hitherto poorly-known upland swamps on the Woronora Plateau, south of Sydney. A major trend in floristic composition was related to the height and cover of the herbaceous stratum and reflected a gradient in soil moisture and nutrients. A second trend in floristic composition was related to the height and cover of the shrub stratum, and may reflect the influence of recurring fires on certain dominant shrub species. Five plant communities were recognized on the basis of floristic composition and were distinguishable by their different soil habitats and/or structural characteristics. We report some of the highest species-richness values in the world (at scales of 1-15 m^) for shrub/sedge-dominated vegetation, with up to 70 vascular plant species in 15 m^. Variation in species richness is inversely related to the resource gradient and positively related to the penetration of light through the vegetation canopy. This pattern is consistent with resource-competition models and warrants further investigation.

Seed production and predispersal seed predation in the shrub Acacia suaveolens were examined over 3 consecutive years in eight populations in south-eastern Australia. Seed-crop sizes varied both between and within populations of different ages. Seed production was maximal in the first one to four flowering seasons after establishment, and then declined with plant age. The size of the annual seed-crop was also influenced by rainfall for that year.Predispersal seed predation varies between populations over fruiting seasons with the initial large seed-crops resulting in predator satiation. Within one fruiting season, no significant variation in the extent of predispersal seed predation was found in any of three populations studied. There were two major forms of predispersal seed loss: toss of whole fruits to Melanterius corosus (Coleoptera: Curculionidae) and external insect seed grazers, and loss of individual seeds within fruits to M. corosus. Exclusion experiments showed that seeds lost to these predispersal seed predators would otherwise have been matured by the parent plant. The effects of predispersal seed predation cannot be directly related to seedling recruitment. Indirectly, such predation may influence the dispersion of seeds in the soil profile and hence, subsequent recruitment.

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At focal sites within dry sclerophyll woodland and temperate rain forest, species were identified that were of low local abundance and hence in the tail of the rankabundance curve. We then asked the question: What proportion of tail species within a given community are constitutive members of the tail everywhere throughout their geographical range, versus what proportion are found as substantially more abundant somewhere within their range? Out of 55 tail species identified from dry sclerophyll woodland and 116 tail species identified from temperate rain forest, 91% and 95%, respectively, were significantly more abundant at other locations (''somewhere-abundant'' species), versus 9% and 5% ''everywhere-sparse'' species. Among eight attributes in dry sclerophyll woodland and nine attributes in temperate rain forest compared between somewhere-abundant and everywhere-sparse species, none discriminated consistently between the two groups of species. The size and dispersal morphology of seeds, flowering and fruiting durations and seasons, regeneration strategy after fire, size of geographical ranges, maximum plant height, and size class revealed no consistent distinctions. For the small minority of species that are everywhere-sparse, some general explanation may exist as to why they are in the tail of rank-abundance curves, though none was located among the attributes compared in this paper. For the majority of tail species that are somewhere-abundant, any explanation as to why they are in the tail will need to account for different outcomes in different places.