Contrasting patterns of litterfall seasonality and seasonal changes in litter decomposability in a tropical rainforest region

The seasonality of litter inputs in forests has important implications for understanding ecosystem processes and biogeochemical cycles. We quantified the drivers of seasonality in litterfall and leaf decomposability using plots throughout the Australian wet tropical region. Litter fell mostly in the summer (wet, warm) months in the region, but other peaks occurred throughout the year. Litterfall seasonality was modelled well with the level of deciduousness of the site (plots with more deciduous species had lower seasonality than evergreen plots), temperature (higher seasonality in the uplands), disturbance (lower seasonality with more early secondary species) and soil fertility (higher seasonality with higher N : P/P limitation) (SL total litterfall model 1 = deciduousness + soil N : P + early secondary sp.: r2 = 0.63, n = 30; model 2 = temperature + early secondary sp. + soil N : P: r2 = 0.54, n = 30; SL leaf = temperature + early secondary sp. + rainfall seasonality: r2 = 0.39, n = 30). Leaf litter decomposability was lower in the dry season than in the wet season, driven by higher phenolic concentrations in the dry, with the difference exacerbated particularly by lower dry season moisture. Our results are contrary to the global trend for tropical rainforests; in that seasonality of litterfall input was generally higher in wetter, cooler, evergreen forests, compared to generally drier, warmer, semi-deciduous sites that had more uniform monthly inputs. We consider this due to more diverse litter shedding patterns in semi-deciduous and raingreen rainforest sites, and an important consideration for ecosystem modellers. Seasonal changes in litter quality are likely to have impacts on decomposition and biogeochemical cycles in these forests due to the litter that falls in the dry season being more recalcitrant to decay

The hookworm Ancylostoma ceylanicum: an emerging public health risk in Australian tropical rainforests and Indigenous communities

Ancylostoma ceylanicum is the common hookworm of domestic dogs and cats throughout Asia, and is an emerging but little understood public health risk in tropical northern Australia. We investigated the prevalence of A. ceylanicum in soil and free-ranging domestic dogs at six rainforest locations in Far North Queensland that are Indigenous Australian communities and popular tourist attractions within the Wet Tropics World Heritage Area. By combining PCR-based techniques with traditional methods of hookworm species identification, we found the prevalence of hookworm in Indigenous community dogs was high (96.3% and 91.9% from necropsy and faecal samples, respectively). The majority of these infections were A. caninum. We also observed, for the first time, the presence of A. ceylanicum infection in domestic dogs (21.7%) and soil (55.6%) in an Indigenous community. A. ceylanicum was present in soil samples from two out of the three popular tourist locations sampled. Our results contribute to the understanding of dogs as a public health risk to Indigenous communities and tourists in the Wet Tropics. Dog health needs to be more fully addressed as part of the Australian Government's commitments to "closing the gap" in chronic disease between Indigenous and other Australians, and encouraging tourism in similar locations

Terrestrial habitat requirements of nesting freshwater turtles

Because particular life history traits affect species vulnerability to development pressures, cross-species summaries of life history traits are useful for generating management guidelines. Conservation of aquatic turtles, many members of which are regionally or globally imperiled, requires knowing the extent of upland habitat used for nesting. Therefore, we compiled distances that nests and gravid females had been observed from wetlands. Based on records of \u3e 8000 nests and gravid female records compiled for 31 species in the United States and Canada, the distances that encompass 95% of nests vary dramatically among genera and populations, from just 8 m for Malaclemys to nearly 1400 m for Trachemys. Widths of core areas to encompass varying fractions of nesting populations (based on mean maxima across all genera) were estimated as: 50% coverage = 93 m, 75% = 154 m, 90% = 198 m, 95% = 232 m, 100% = 942 m. Approximately 6–98 m is required to encompass each consecutive 10% segment of a nesting population up to 90% coverage; thereafter, ca. 424 m is required to encompass the remaining 10%. Many genera require modest terrestrial areas (\u3c200 m zones) for 95% nest coverage (Actinemys, Apalone, Chelydra, Chrysemys, Clemmys, Glyptemys, Graptemys, Macrochelys, Malaclemys, Pseudemys, Sternotherus), whereas other genera require larger zones (Deirochelys, Emydoidea, Kinosternon, Trachemys). Our results represent planning targets for conserving sufficient areas of uplands around wetlands to ensure protection of turtle nesting sites, migrating adult female turtles, and dispersing turtle hatchlings

Productivity and nutrient content of Juncus kraussii in an estuarine marsh in south-western Australia

Juncus kraussii, which is the dominant emergent macrophyte in the marshes of the Blackwood River Estuary, has an estimated net above-ground production there of 0.3 to 1.3 kg dry weight m-2 yr-1. A high standing crop of live culms is present throughout the year and dead material generally exceeds live. New culms are produced throughout the year, but especially during the warm season. Growth and senescence of culms also occurs throughout the year although there is evidence for increased growth in the warm season. Concentrations of nitrogen and phosphorus are given on a per g dry weight and per m2 basis. Some 60% of the nitrogen and 50% of the phosphorus remain in the dead culm material, the remainder being retranslocated. Sodium and, especially, potassium are readily retranslocated during senescence, but calcium and magnesium are much less mobile

The nutrients and plants of Lake Joondalup, a mildly eutrophic lake experiencing large seasonal changes in volume

Lake Joondalup is a shallow body of fresh water in a calcareous stable dune system 6 km from the ocean. The fringing and aquatic vegetation is described. Cation ratios resemble sea water apart from relatively high calcium, attributed to leaching from limestone. Seasonal changes in volume greatly affect ionic concentrations. A bloom of the green alga Dispora coincides with low volume and high ion levels. Total nitrogen is relatively high compared with phosphorus. The surrounding land is becoming urbanized, and the data provide a baseline for future reference

Productivity of Ruppia: Seasonal changes and dependence on light in an Australian estuary

Ruppia shows seasonal changes in biomass with peak standing crops which differ between sites and years, but which are usually at a maximum in late spring and early summer. Ruppia produces annually some 75–500 g dry wt. m−2 in the estuary, and the total annual net production for the whole estuary is of the order of 700–1900 tonnes dry wt. Mesh enclosures were used to investigate effects of shading on standing crop. Increased light attenuation significantly reduces the contribution of this species to primary production. With increased duration of shading, higher light intensities are required to sustain high standing crops. Ruppia may be precluded if its ambient light intensity is reduced by 80% or more for up to 100 days; a reduction by 20% for 250 days results in a significant decrease in biomass

The vegetation of the Blackwood River estuary, southwest Australia

(1) The standing crop and productivity of the main primary producers (the sources of autochthonous detritus) were measured in a West Australian estuary which has a shallow estuarine basin, two small lagoons and a tidal river, and which has marked seasonal changes in salinity. (2) Standing crops of phytoplankton (mainly diatoms) are small in the open water; no blooms were observed during 3 yr. In sporadic sampling the highest concentration of chlorophyll 'a' was 1-98 jig I -1. Sediments contain more chlorophyll (as microscopic algae) per unit area than does the water column. Small phytoplankton stocks are attributed to low nutrient concentration when light flux and temperature are high and water-residence time low. (3) Macroscopic algae (twenty species) are most prominent in the summer marine phase. Their distribution is very patchy, and they have a small total biomass. (4) There are four benthic angiosperms in the estuary. The greatest contributor to production in open water is Ruppia, which is the most widely distributed of these, and has a peak dry-weight standing crop of 503 g m-2. (5) The fringing marshes are mainly dominated by Juncus kraussii, which reaches a dry-weight standing crop of about 5 kg m-2. (6) Based on general distribution, standing crops and published seasonal data, it is estimated that Ruppia produces about 700-1900 tonnes (dry weight) yr- 1, Juncus about 1000-4500, and the paperbark trees (Melaleuca spp.) of the marsh about 800 tonnes yr- 1 in leaf litter. Most of this organic material must become available as detritus, as only Ruppia is grazed appreciably

The relationship between phosphorus fractions, phosphatase activity and fertility in three rain forest soils

This study investigates the availability of phosphorus and the forms of bound soil phosphorus present in three rain forest stands in north eastern Queensland. The soil types investigated differed significantly with respect to total soil phosphorus, with fertility decreasing in soils from basaltic to alluvial to granitic origin. At all sites only a small proportion of total phosphorus was available for plant uptake, with most being bound in organic matter and inorganic forms. A pot experiment was set up with Alphitonia petriei which was grown in soil collected from each of the three sites. After four months there was a significant difference in the dry weights, with plants showing stunted growth in the granitic soil collected from the site with the lower available phosphorus concentrations. These plants also had significantly higher root to shoot ratios and lower intracellular concentrations of phosphorus. Root phosphatase activity was greater for plants grown in soil low in available phosphorus