B.J. Bailey’s scientific contributions

Litterfall from a Melaleuca forest was investigated as part of chemical cycling studies on the Magela Creek floodplain in tropical, northern Australia. The forest contained two species of tree, Melaleuca cajaputi and Melaleuca viridiflora, with a combined average density of 294 trees ha–1. The M. viridiflora trees had diameter breast height measurements ranging from 11.8 to 62.0 cm, median class 25.1–30.0cm and a mean value of 29.21.0 cm, compared to 13.0 to 66.3 cm, 30.1–35.0cm and 33.51.0cm for M. cajaputi trees. A regression model between tree height, diameter breast height and fresh weight was determined and used to calculate average tree weights of 7751.6kg for M. viridiflora and 10091.6kg for M. cajaputi, and a total above-ground fresh weight of 2630.3t ha–1. The weight of litter recorded each month on the ground beneath the tree canopy ranged from 582103 to 2176376 g m–2 with a monthly mean value of 110551 g m–2. The coefficient of variation of 52% on this mean indicates the large spatial and temporal variability in litter distribution over the study site. This variability was greatly affected by the pattern of water flow and litter transport during the Wet season. Litterfall from the trees was evaluated using two techniques - nets and trays. The results from these techniques were not significantly different with annual litterfall collected in the nets being 705 25 g m–2 and in the trays 71649 g m–2. The maximum monthly amount of litterfall, 108 55g m–2, occurred during the Dry season months of June–July. Leaf material comprised 70% of the total annual weight of litter, 48029 g m–2 in the nets and 495 21 g m–2 in the trays. The tree density and weight of litter suggest that the Melaleuca forests are highly productive and contribute a large amount of material to the detrital/debris turnover cycle on the floodplain.

The size and species composition of plant populations arising from sediment seedbanks of three communities (Pseudoraphis, Hymenachne and Oryza grasslands) on the Magela Creek floodplain were compared under experimental (moist and flooded) conditions. The mean number of seedlings produced in the moist-treatment ranged from 8000 to 15 400 m−2, and in the flooded-treatment ranged from 3800 to 7100 m−2. Seed from 33 taxa germinated: 22 from the Oryza-, 13 from the Pseudoraphis- and 18 from the Hymenachne-site samples. The Pseudoraphis-site seedbank was closer in composition to that of the Hymenachne-site and Oryza-site seedbank. In terms of the species present the Pseudoraphis-site seedbank closely reflected that of its community on the floodplain, whereas the Hymenachne-site and Oryza-site seedbanks were not as closely related to the composition of their respective floodplain communities. Indices of diversity and evenness point to the relative homogeneity of species seedbank production in the moist-treatment of Pseudoraphis- and Hymenachne-site samples, compared with that in both treatments of the Oryza-site samples and the flooded-treatment of Pseudoraphis- and Hymenachne-site samples. Pseudoraphis spinescens (R.Br.) Vick. with a relatively small, but persistent seed dominated the seedling composition of the Pseudoraphis- and Hymenachne-site samples.

Describes the physico-chemical and biological characteristics of the 250 km2 of the Magela floodplain. The phytoplankton community is very diverse with >160 diatom taxa and 530 taxa from other groups. Chlorophyll values were not generally high except during blooms. The macrophytic flora was also diverse with 225 species, 139 being annuals. The floristic composition and foliage cover of the ten main macrophyte communities varied seasonally, the abundance and floristic richness of the wet season contrasting with the sparse cover of the dry season. Invertebrates demonstrated vast temporal and spatial differences in species abndance. Species diversity was greatest during the wet season. The distribution and habitat selection and abundance of the fishes and amphibia were influenced by the occurrence of floodwaters during the wet season. The water birds were also numerous and diverse: usage of the floodplain varied seasonally with >200 000 occurring during the dry season when food resources were scarce elsewhere. -from Authors

Outlines the climate and geomorphological origin of wetlands in the Northern Territory, and describes the distribution and vegetation of saltmarshes, mangrove swamps, intermittent swamps, seasonally-covered floodplains and lakes. The conservation status of wetlands is reviewed, considering the distribution and ownership of wetland reserves, aboriginal use of wetlands, and threats and management problems (feral animals, pollution, introduced species, mangrove degradation, saltwater intrusion, tourism and recreation, and pastoral activities). Aspects of wetland conservation and maintenance are noted. -P.J.Jarvis