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The native annual Sorghum populations of the Australian wet-dry tropics are highly resilient to dry season fires. During the early wet season, however, fires that occur after the new grass population has emerged can cause catastrophic population crashes. We examined savanna plots that had been burnt in this way, and compared them with adjacent unburnt plots. We found that Sorghum densities in the burnt plots were lower on average by a factor of 10, but that some fires had reduced the density only to one-third of the unburnt plots. It is not clear whether these differences relate directly to site or seasonal factors, or to differences in the way the burning was carried out. Other vegetation components responded to the fires differently: forbs (dicotyledonous herbs) increased in cover, while perennial grasses, woody plants, and overall species richness, were not significantly affected.The amount of leaf litter declined. A population model for Sorghum based on the demography of unburnt populations predicted that they should recover from a wet season burn, taking 7-16 years to return to normal densities. However, the actual field populations did not seem tobe recovering, suggesting that wet season fires not only lower densities, but may also fundamentally change population processes in theseannual grasses. [ABSTRACT FROM AUTHOR]

A general decline in populations of some savanna mammal species has occurred since the mid- 1980s in a fairly pristine national park environment in the Australian wet-dry tropics. Terrestrial native rodentshave exhibited the greatest decline and marsupials the least. Duringthe same period, waterholes have dried up and the previous strong association of mammals with riparian vegetation has diminished. A regional index of the level of groundwater was developed from 16 unexploited bores from across the northern half of the Northern Territory. Predicted mean groundwater values over 28 years showed a strong increasethroughout the 1970s and a similar decrease throughout the 1980s. Using data since 1986, strong correlations between mammal numbers and groundwater levels for the preceding two years, and much weaker relationships with rainfall, were obtained. In turn, the groundwater levelswere best correlated with an eight-year running mean of rainfall forboth Darwin and Alice Springs and an eleven-year running mean for the Southern Oscillation Index. Extrapolating backward in time, cumulative pressure variation at Darwin showed two extended periods of predicted low groundwater values, 1900s--1920s and 1940s. Both periods were preceded by the last records of a number of now-extinct mammals from central Australia. A third trough in the early 1960s suggests another period of extinction in central Australia, previously unappreciated due to the lack of survey work in the 1950s. Further, by this analysis, the past 20 years has been the best period for mammals since weather records commenced. Analysis of continental-scale distributions of mammals showed evidence of fluctuations suggesting rocky areas are important refuges for some species during periods of low groundwater levels. In contrast to those in savanna habitats, the mammals of the extensive wetland areas fluctuated in harmony with rainfall on a short-term basis except where habitat is flooded. It is the species whichoccur [ABSTRACT FROM AUTHOR]

Fire is a dominant feature of tropical savannas throughout the world, and provides a unique opportunity for habitat management at the landscape scale. We provide the background and methodology for a landscape-scale savanna fire experiment at Kapalga, located in Kakadu National Park in the seasonal tropics of northern Australia. The experimentaddresses the limitations of previous savanna fire experiments, including inappropriately small sizes of experimental units, lack of replication, consideration of a narrow range of ecological responses and an absence of detailed measurement of fire behaviour. In contrast to those elsewhere in the world, Australia's savannas are sparsely populated and largely uncleared, with fires lit primarily in a conservation, rather than pastoral, context. Fire management has played an integral role in the traditional lifestyles of Aboriginal people, who haveoccupied the land for perhaps 50 000 years or more. Currently the dominant fire management paradigm is one of extensive prescribed burning early in the dry season (May-June), in order to limit the extent and severity of fires occurring later in the year. The ecological effects of different fire regimes are hotly debated, but we identify geo-chemical cycling, tree demography, faunal diversity and composition, phenology, and the relative importance of fire intensity, timing and frequency, as critical issues. Experimental units ('compartments') at Kapalga are 15-20 km2 catchments, centred on seasonal creeks that drain into major rivers. Each compartment has been burnt according to one of four treatments, each replicated at least three times: 'Early'--fires lit early in the dry season, which is the predominant management regime in the region; 'Late'--fires lit late in the dry season, as occurs extensively in the region as unmanaged 'wildfires';'Progressive'--fires lit progressively throughout the dry season, such that different parts of the landscape are burnt as they progressively [ABSTRACT FROM AUTHOR]

Examines the distribution of termite communities in tropical Australia. Relationship between soil characteristics and diversity of termites; Implication of the ability of termites to exploit low fertility systems for the size structure of the vertebrate community; Evidence of a reciprocal relationship between termites and mammals.

Examines the impact of water buffalo on the monsoon forest ecosystem in Kakadu National Park. Calculation of the sum of the distances to important features of human activity; Features of human activity; Examination of monsoon forest sites by simple linear regression.