A transect study of forests and woodlands on dolerite in the Eastern Tiers,Tasmania

In natural vegetation, individuals of different species are more often than not distributed contagiously and arranged as patches. In experimental studies on interference between plant species, this aspect has been neglected.In the experimental approach presented here the vegetation (seven plant species characteristic of woodland clearings) consists of a mosaic of hexagons of 16 m² each, in such a way that each monospecific plot of the honeycomb was surrounded by six hexagons planted with other species. In addition, there were separate hexagons without adjacent neighbours. In this way the fate of plants in plots, with and without the influence of vegetatively expanding neighbours could be compared.Ecological advantages of the method applied are a) a high degree of similarity with natural patterns of vegetation, b) the opportunity for the different species to consolidate their own microhabitat, which might have repercussions with regard to succession, c) the comparability of different monocultures with the corresponding units in the mixture.The species specific plant growth (and concurrent capture of nutrients) played an important role in the mechanism of interference (and subsequent succession). Allelopathic effects cannot be excluded.Nomenclature follows Heukels & Van Ooststroom (1973).The authors are indebted to Drs. A. J. de Neeling for his advice with regard to the experimental set-up.     

Numbers,species richness and equitability of coastal birds at Darwin,Northern Territory

Studies of the species richness and equitability were made of coastal birds at Darwin, Northern Territory, following censusing. A general decrease in numbers and species richness of indigneous and palaearctic migrants occurred in the wet season. Equitability values were depressed at the beginning of the wet season indicating an ecologically disturbed situation Freshwater discharge and its complex mixing patterns in neritic and estuarine water may be responsible for such a disturbance through its effects on the bird's food supply.     

Poor recovery of woody vegetation on sand and gravel mines in the Darwin region of the Northern Territory

Summary Sand sheets near Darwin support a distinct heathland vegetation type which includes the habitat of several threatened species. Sand and gravel are extracted from shallow mines in this region. Woody vegetation recovery in 31 small, shallow former sand or gravel mine sites near Darwin that were up to 27 years old was assessed and compared to paired unmined control sites. Recovery in vegetation structure within each mine was calculated as the percentage of that in the control site. Mined sites recovered about 50% of their stem count and canopy cover, but only about 10% of basal area and mature tree count. Gravel mines showed poorer recovery than sand mines. Time since mining had no significant effect on the extent of recovery, but deeper mines had significantly poorer recovery. Only 35% of woody species in sand controls were present in mine sites, and 41% of gravel control species were present in former mine sites. It is unlikely that recovery will significantly improve in coming decades. Sand mining affects about 40 ha of land per year in this region, but is likely to increase in the future. If Darwin expands to a population of 1 million people, and mine sites are not fully rehabilitated, all of the sand‐sheet vegetation in the region could be removed in the next 100 years. Improved rehabilitation and protection is crucial for the conservation of heathland vegetation in this region.     

The abundance and growth of Avicennia marina and Rhizophora stylosa in the low shore zone of Darwin Harbour,Northern Territory

Abstract The growth and distribution of the two mangrove seedling species, Avicennia marina (Forsk.) Vierh. and Rhizophora stylosa Griff., were studied in the low-shore zone at three locations along two estuaries of Darwin Harbour to determine how growth varied along the estuary and within the habitats of the low shore zone. The low shore environment was heterogenous for factors such as salinity and light, with substantial variation within and between locations. Seedlings of Avicennia were in higher densities in light gaps than in the adjacent forest, and density in both habitats decreased towards the mouth of the estuary. Growth of Avicennia seedlings, as measured through in situ growth trials and plant harvests, increased towards the mouth of the estuary. Results for Rhizophora seedlings were more complex although some similar trends were evident. This may have been due to the greater early survival of Rhizophora seedlings compared to Avicennia seedlings. The importance of propagule origin was investigated, for Rhizophora, by transplanting propagules between locations along one estuary. Increased seedling survival was observed at the propagule source site; however, this effect was subtle and probably not the most important factor affecting seedling survival at a site.     

Response of vegetation and vertebrate fauna to 23 years of fire exclusion in a tropical Eucalyptus open forest,Northern Territory,Australia

Abstract This opportunistic study compares the vegetation, fuel loads and vertebrate fauna of part of a 120‐ha block of tropical open forest protected from fire for 23 years, and an adjacent block burnt annually over this period. Total fuel loads did not differ significantly between the unburnt and annually burnt sites, but their composition was markedly different, with far less grassy fuel, but far more litter fuel, in the unburnt block. There were major differences between treatments in the composition of trees and shrubs, manifest particularly in the number of stems. There was no overall difference in plant species richness between the two treatments, but richness of woody species was far higher in the unburnt treatment, and of annual and perennial grasses, and perennial herbs in the annually burnt treatment. Change in plant species composition from annually burnt to unburnt treatment was directional, in that there was a far higher representation of rainforest‐associated species (with the percentage of woody stems attributable to ‘rainforest’ species increasing from 24% of all species in the annually burnt treatment to 43% in the unburnt treatment, that of basal area from 9% to 30%, that of species richness from 8% to 17%, and that of cover from 12 to 47%). The vertebrate species composition varied significantly between treatments, but there was relatively little difference in species richness (other than for a slightly richer reptile fauna in the unburnt treatment). Again, there was a tendency for species that were more common in the unburnt treatment to be rainforest‐associated species. The results from this study suggest that there is a sizeable and distinct set of species that are associated with relatively long‐unburnt environments, and hence that are strongly disadvantaged under contemporary fire regimes. We suggest that such species need to be better accommodated by fire management through strategic reductions in the frequency of burning.     

Crusted scabies; a 2-year prospective study from the Northern Territory of Australia

BackgroundScabies is listed as a neglected tropical disease by the World Health Organization. Crusted scabies affects vulnerable and immunosuppressed individuals and is highly contagious because of the enormous number of Sarcoptes scabiei mites present in the hyperkeratotic skin. Undiagnosed and untreated crusted scabies cases can result in outbreaks of scabies in residential facilities and can also undermine the success of scabies mass drug administration programs.Methods and principal findingsCrusted scabies became a formally notifiable disease in the Northern Territory of Australia in 2016. We conducted a 2-year prospective study of crusted scabies cases notified between March 2016 and February 2018, with subsequent follow up for 22 months. Demographics, clinical and laboratory data, treatment and outcomes were analysed, with cases classified by severity of disease.Over the 2-year study period, 80 patients had 92 episodes of crusted scabies; 35 (38%) were Grade 1 crusted scabies, 36 (39%) Grade 2 and 21 (23%) Grade 3. Median age was 47 years, 47 (59%) were female, 76 (95%) Indigenous Australians and 57 (71%) from remote Indigenous communities. Half the patients were diabetic and 18 (23%) were on dialysis for end-stage kidney failure. Thirteen (16%) patients had no comorbidities, and these were more likely to have Grade 3 disease. Eosinophilia was present in 60% and high immunoglobulin E in 94%. Bacteremia occurred in 11 episodes resulting in one fatality with methicillin-susceptible Staphylococcus aureus bacteremia. Two other deaths occurred during admission and 10 others died subsequent to discharge consequent to comorbidities. Treatment generally followed the recommended guidelines, with 3, 5 or 7 doses of oral ivermectin depending on the documented grade of crusted scabies, together with daily alternating topical scabicides and topical keratolytic cream. While response to this therapy was usually excellent, there were 33 episodes of recurrent crusted scabies with the majority attributed to new infection subsequent to return to a scabies-endemic community.ConclusionsCrusted scabies can be successfully treated with aggressive guideline-based therapy, but high mortality remains from underlying comorbidities. Reinfection on return to community is common while scabies remains endemic.     

Comparison of leaf litter ant communities in woodlands, lowland forests and montane forests of north-eastern Tanzania

Ants were extracted in Winkler bags from sifted leaf litter sampled in arange of forest and woodland types in and around Mkomazi Game Reserve innorth-eastern Tanzania, including the Eastern Arc Mountains of South Pare andWest Usambara. A total of 87 ant species were recorded, of which 32.2% were onlyrecorded from montane forests (1400–1850 m altitude), 6.9%only from lowland forest (540–810 m), 19.5% only fromwoodland (300–1080 m), and 16.1% in all three forest types.Of the 28 species recorded only from montane forests, 12 species were only foundin the Mkomazi forests, four only in the Pares and seven species only in theUsambaras. Sites of similar altitude grouped together in a cluster analysis, andspecies richness decreased with an increase in altitude. The lowland forest andclosed woodland sites did not form distinct communities. To ensure preservationof ant species, forests from a full range of altitudes need to be conserved.This study confirms the status of the West Usambara forests as having a highlyendemic biota, and the critical need to adequately conserve the remainingvestiges of montane forest within Mkomazi Game Reserve.     

Regional ecological risk assessment using a relative risk model: A case study of the Darwin Harbour,Darwin, Australia

There are many proposed and ongoing commercial, industrial, and residential developments within the Darwin Harbour catchment in Northern Australia, to accommodate the projected population growth over the next 20 years. Hence, it is necessary to ensure the balance between these developments and ecosystem conservation. We evaluated ecological risk for the Darwin Harbour using a relative risk model (RRM). The catchment was divided into 22 risk regions based on small catchment boundaries and their homogeneity. Through the RRM, we ranked and summed the stressors and habitats within regions. The interaction between stressors and habitats were modeled through exposure and effect filters. The ecological assessment endpoints were maintenance of the mangrove health and the maintenance of water quality. The risk regions—Myrmidon Creek, Blackmore River, Bleesers Creek, and Elizabeth River—showed the highest total relative risk for ecological assets. These risk regions had a high percentage cover of industrial, commercial, and residential areas; diffuse entry points; and climate change effects. Creek A, Sandy Creek, West Arm, and Pioneer Creek were the risk regions with lowest total relative risk scores. The RRM is a robust application that is suitable for a large geographic area where multiple stressors are of concern.     

The forests and woodlands of Labrador, Canada: ecology, distribution and future management

Labrador, Canada is the last relatively undeveloped landmass of Boreal and subarctic Canada. Its land area is over 288,000 km², with less than 1% developed, and a human population of below 30,000. Labrador is greater than 60% forest- and woodland-covered and over 30% tundra, soil and rock barrens. We review the ecology and distribution of forests, woodlands, and related vegetation of Labrador within the context of climate, forest site index, landform, soils, and disturbance. Recent ecosystem management through a public planning process with emphasis on past and future comanagement and development with traditional and western scientific principles is currently underway. Plant–animal interactions, traditional uses by aboriginal groups, and early history are also reviewed.     

A further study of genetic distance among Australian Aborigines: Nine tribes in the Northern Territory

Summary A study of genetic distance has been carried out between 9 Aboriginal tribes in the Northern Territory of Australia. The B statistic of Balakrishnan and Sanghvi (1968) was employed and the analysis was based on the variability demonstrated in 8 blood groups, serum protein and enzyme systems. The genetic distance relationships were found to be correlated with linguistic differences amongst the tribes as well as with the geographic distance separating them.

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Zusammenfassung Eine genetische Abstands-Studie von 9 Eingeborenen-Stämmen im nördlichen Australien wurde ausgeführt. Die B-Statistik von Balakrishnan u. Sanghvi (1968) wurde angewendet. Die Analyse geht von den Unterschieden aus, die in 8 Blutgruppen, im Serum-Protein und bei den Enzym-systemen demonstriert wurden. Die genetische Abstands-Verwandtchaft wurde mit linguistischen Unterschieden und mit der räumlichen Entfernung, in der die Stämme wohnen, in Beziehung gesetzt.

     

Spatial and temporal variability in benthic processes along a mangrove-seagrass transect near the Bangrong Mangrove,Thailand

Benthic primary production and nutrient dynamics were examined along a transect in the Bangrong mangrove forest in Thailand. Six stations were established extending from a high-intertidal site within the mangrove forest to low-intertidal flats and seagrass beds in front of the mangrove forest. Benthic processes (O₂ and CO₂ fluxes) and nutrient dynamics (mineralization, sediment-water fluxes, pore water and sediment pools) were measured under light and dark conditions during wet and dry seasons over a 2-yr period. The sediments were mostly autotrophic, only the mangrove forest sites were net heterotrophic during the wet season. Maximum daily net primary production was found at the non-vegetated tidal flats (40–75 mmol O₂ m^-2d^-1), where light and nutrient availability were highest. The variation in benthic mineralization along the transect was minor (1.6–4.3 mmol CO₂ m^-2h^-1) and did not reflect the large changes inorganic matter content (organic carbon: 0.7–4.2% DW) and quality (C:N ratio varied from 25 to 100), suggesting that the mineralizable pool of organic matter was of similar magnitude at all sites. There was only minor seasonal variation in rates of mineralization. The net primary production showed more variation with lower rates in the mangrove forest (reduced with 74%) and higher rates at the tidal flats (increased with 172%) and in the seagrass beds (increased with 228%) during the wet season. The nutrient pools and fluxes across the sediment-water interface were generally low along the transect, and the sediments were efficient in retaining nitrogen in the nutrient limited mangrove/seagrass environment. Pools and fluxes of phosphorus were generally very low suggesting that benthic primary production was phosphorus limited along the transect. This revised version was published online in July 2006 with corrections to the Cover Date.     

Reproductive characteristics of Drosophila hibisci in the Northern Territory, Australia

Reproductive traits of Drosophila hibisci collected at 18 sites in the Northern Territory (NT) of Australia in May, 1998, as well as at two sites in north Queensland, in June, 1998, were compared to those from earlier work on a cline in ovariole number in D. hibisci along the east coast of Australia. The flies in the NT were considerably smaller, but had more ovarioles than comparably-sized flies on the east coast. Although the flies on the east coast showed an increasing number of ovarioles in populations at increasing distances from the equator, these new populations, both on the east coast and in the NT, reversed this trend, producing a generally U-shaped pattern of ovariole number with latitude among all populations. The northernmost and southernmost populations allocate more to ovariole numbers than populations in intermediate latitudes. Ovariole number is closely related to body size of females in all populations, but the regression coefficient is small at intermediate latitudes and increases at the northern and southern ends of the distribution. Egg volumes primarily varied with body size of the female (positive) and number of ovarioles per female (negatively), producing a generally inverted U-shaped pattern of egg volumes with latitude. Reproductive allocation patterns, but not thorax size or ovariole number, varied significantly in two samples taken 10 days apart at one NT site. This variation probably results from environmental differences across generations of developing larvae and is consistent with our earlier suggestion of substantial effects of the environment, primarily rainfall and temperature, on reproductive allocation in D. hibisci.     

A geospatial evaluation of Aedes vigilax larval control efforts across a coastal wetland,Northern Territory,Australia

Adjacent to the northern suburbs of Darwin is a coastal wetland that contains important larval habitats for Aedes vigilax (Skuse), the northern salt marsh mosquito. This species is a vector for Ross River virus and Barmah Forest virus, as well as an appreciable human pest. In order to improve aerial larval control efforts, we sought to identify the most important vegetation categories and climatic/seasonal aspects associated with control operations in these wetlands. By using a generalized linear model to compare aerial control for each vegetation category, we found that Schoenoplectus/mangrove areas require the greatest amount of control for tide‐only events (30.1%), and also extensive control for tide and rain events coinciding (18.2%). Our results further indicate that tide‐affected reticulate vegetation indicated by the marsh grasses Sporobolus virginicus and Xerochloa imberbis require extensive control for Ae. vigilax larvae after rain‐only events (44.7%), and tide and rain events coinciding (38.0%). The analyses of vector control efforts by month indicated that September to January, with a peak in November and December, required the most control. A companion paper identifies the vegetation categories most associated with Aedes vigilax larvae population densities in the coastal wetland. To maximize the efficiency of aerial salt marsh mosquito control operations in northern Australia, aerial control efforts should concentrate on the vegetation categories with high larval densities between September and January.     

A computer model of succession and fire response of the high-altitude Eucalyptus forest of the Brindabella Range,Australian Capital Territory

The BRIND model, a computer model of the high altitude forests in the Brindabella Range near Canberra (Australian Capital Territory), is documented and the results of a series of tests on the model are provided. The BRIND model simulates a 1/12 ha forest stand by computing the growth of each individual tree in the stand. It considers establishment and death of trees on a tree-by-tree basis using stochastic functions. The model also simulates the effects of prescribed fire and wildfire on the forests. The model presently is restricted to southeasterly facing slopes (moist, sheltered situations) above 850 m in altitude. The BRIND model is tested in four ways: (1) A single example simulation (for 500years) is inspected for agreement with stand dynamics in wet sclerophyll forests. (2) By varying wildfire frequency, the model is used to develop a succession diagram for forests in the alpine ash (E. delegatensis) zone of the Brindabella Range. This diagram is considered in terms of the successional patterns described for this ecological zone. (3) By subjecting the model to different climatic conditions and wildfire frequencies, a simulated altitude zonation is developed. This simulated pattern of forest types is compared with the extant forest types in the Brindabella Range. (4) The model is tested on its ability to duplicate basal area, stocking density, and average diameters for different age stands found in an independent data set. The model was found to simulate patterns of vegetation that resemble those of the forests of the Brindabella Range in both space and time. The successional pattern was found to be complex and to differ from classic theories of succession originating with Clements. Potential model applications are discussed     

The termite (Isoptera) fauna of a monsoonal rainforest near Darwin, northern Australia

Abstract  Termite species richness, frequency of occurrence and functional diversity at Holmes Jungle Nature Reserve, a monsoon rainforest patch in northern Australia, was investigated at the end of the wet season in 2003. A sampling protocol that employed direct search, soil pits and baiting techniques was used to sample litter, wood, mound, soil and arboreal nest microhabitats for termites. Five species from five genera and three families (Mastotermitidae, Rhinotermitidae and Termitidae) were recorded. This included the first record of Ephelotermes taylori (Hill) from monsoon forest in Australia. The family Termitidae was dominant and represented 70% of termite occurrences. Termites were most frequently encountered in carton runways on tree trunks, followed by lying dead wood and baits. Four nesting habits were represented: arboreal, epigeal, hypogeal and within wood. The arboreal nest-builder Nasutitermes graveolus (Hill) accounted for 61% of termite encounters. Epigeal mound-building species were rare. Wood-feeders were the only trophic group represented. Relatively high activity of Mastotermes darwiniensis Froggatt was recorded at baits within 2.5 months. The low species richness recorded at Holmes Jungle is consistent with the low diversity reported for Australian rainforests generally, but remains relatively depauperate compared with other monsoon forest and savanna habitats of the Northern Territory.     

Dynamics and management of some coastal dune woodlands near The Hague,The Netherlands

Changes are reported of Crataegus-Betula dune woodlands between 1950–1980 from Meijendel, a calcareous coastal dune system near the city of The Hague, The Netherlands, which is used as a water catchment area. It concerns both woodlands in degradation stage and, more common, woodlands on the increase. Changes were recorded with help of successive vegetation maps, air photos and permanent plot observations. Woodland increase usually occurs on places with groundwater at or near the surface, either because of natural circumstances or as a result of artificial groundwater recharge through infiltration as part of the water catchment activities. The management of both types of woodland is discussed.Nomenclature follows Heukels-van der Meijden (1983), Flora van Nederland, 20th ed. Wolters-Noordhoff, Groningen. Nomenclature of mosses follows Margadant & During (1982), Beknopte Flora van Nederlandse Blad- en Levermossen, Thieme, Zutphen.The authors have pleasure in thanking their colleagues from the Dune Water Works who supplied data on hydrology.     

A comparison of Aedes vigilax larval population densities and associated vegetation categories in a coastal wetland,Northern Territory,Australia

Darwin's northern suburbs border an extensive coastal reed and upper mangrove wetland recognized as an important larval habitat for Aedes vigilax (Skuse), the northern salt marsh mosquito, an established vector for Ross River and Barmah Forest viruses and an appreciable pest species. We sought to identify the most important vegetation categories associated with Ae. vigilax breeding to maximize the efficiency of mosquito control efforts. Using a generalized linear model with negative binominal distribution and log link, this study compares larval densities, determined by focused dipping, between 13 discernable vegetation categories. The incidence rate ratios (RR) generated can be used to compare the magnitude of larval densities for each vegetation category, compared with the reference category. Aedes vigilax larval densities were almost ten times greater in artificial drainage areas (RR=9.82), followed by tide‐affected reticulate (Sporobolus/Xerochloa) areas (RR=8.15), then Schoenoplectus/mangroves (RR=2.29), compared with the reference vegetation category “lower mangroves.” Furthermore, larval densities were highest in May, due to tidal inundation, for drainage areas and tide‐affected reticulates (RR=12.2, 11.7, respectively) compared with March, the reference month. Thus, to maximize the efficiency of aerial salt marsh mosquito control operations in this wetland, larval control is best accomplished by concentrating on drains, Schoenoplectus/mangroves, and tide‐affected reticulate areas, commencing early after the wet season. These results should apply to other areas of salt marsh mosquito breeding across northern Australia.