Reducing weed biomass by burning and grazing can adversely affect frogs

The impacts of weed management on native biodiversity are often overlooked. Burning and grazing plots of land in isolation and in combination, were used to experimentally reduce the biomass of introduced para grass (Urochloa mutica(Forssk.) T.Q.Nguyen)) in a North Queensland wetland. Frogs were monitored to assess the impact of these management trials. Marbled frogs (Limnodynastes convexius-culus Macleay) declined in response to all management treatments, and their abundance was correlated with vegetation biomass. The abundance of spotted marsh frogs (Limnodynastes tasmaniensis Günther) was not related to weed control treatments, but was influenced by the distance of the experimental plot from the nearest woodland. The decline of these frog species in response to management trials indicates that knowledge about impacts of planned weed control is critical, to inform management of taxa that may be affected

Weeds in pasture ecosystems - symptom or disease?

Plant species that become weeds in pasture ecosystems require the same resources as useful forage plants - light, water, carbon dioxide. oxygen and mineral nutrients. Their weediness stems from the fact that they package those resources in a form that makes them unavailable as livestock forage. Weed species are either strongly competitive for resources. or they exploit an absence of competitors in disturbed situations. Ecologically-based weed management must discover means of reducing the capacity of weeds to capture resources and of recapturing those that are already tied up in weed populations. Heavy grazing of palatable pasture species reduces the competition faced by invading weeds. Effective biological control agents: reduce the capacity of weeds to capture resources and make them potentially available to more favourable plant species. Pastures that experience high levels: of disturbance provide more opportunities for weeds to establish. Weeds can be interpreted as diseases of pasture but they may also be symptoms that indicate an unhealthy pasture

Weed Biology: a foundation for weed management

Information on the biology of weeds is an impor rant component in the development of integrated control strategies. While 3 complete understanding of their ecology would be ideal, obtaining the answers to just some key ecological questions will help substantially. In an attempt to gain a better understanding of a weed problem and its solution, land managers frequently ask questions about the weed's ecology, including. How long do individual plants live?: How long does it take young plants to become reproductive?; How long will it take fur the seedbank to be depleted once adult plants are removed from a site?; How and how far is the seed dispersed?: and What is the frequency and scale of seedling recruitment? Controlling weeds is an expensive business. A better understanding of their biology will help improve control techniques and ease the financial burden on land managers

Burning season influences the response of bird assemblages to fire in tropical savannas

Fire plays a pivotal role in structuring ecosystems and often occurs as a human-mediated disturbance for land management purposes. An important component of fire regime is the season of burn. In tropical savannas, most fire management occurs during the dry season; however, wet season burning is often used for pastoral management and may be useful for controlling introduced plant species. We used replicated, experimental fire treatments (unburnt, dry season burnt and wet season burnt), spanning two habitats (riparian and adjacent open woodland), to examine the short- (within 12 months of fire) and longer-term (within four years of fire) changes of bird assemblages in response to wet and dry season burning in tropical savannas of northern Australia. Within 12 months of fire, we observed higher abundances of birds in the burnt treatments, although some species (e.g., red-backed fairy-wren, Malurus melanocephalus) were rarely observed in burnt sites. Dry season burnt sites contained higher abundances of insectivores and granivores, while wet season burnt sites had more carnivores. Four years following burning, dry season burnt sites were characterized by lower abundances, especially of nectarivores and granivores. Dry season burnt sites also contained a different assemblage than wet season burnt sites, but few differences were observed between wet season burnt and unburnt sites. Our results confirm that differences in fire regimes can substantially alter bird assemblages, especially in riparian zones, and emphasize the importance of incorporating burning season in fire management strategie

The role of fire in germinating Wild Rice (Oryza meridionalis), an annual grass of northern Australian wetlands threatened by exotic grass invasion

Para Grass (Urochloa mutica (Forssk.) Nguyen) has\ud invaded large areas of north Australian wetlands, out-competing native flora. Post-fire observations indicated that the native grass, Wild Rice (Oryza meridionalis Ng), re-established where gaps in Para grass mats had been created by burning. We tested whether it was fire itself or simply the removal of Para Grass that promoted Wild Rice, by subjecting comparable buried seed batches to one of three treatments:fire (at two intensities) and no fire. Subsequent germination tests confirmed current laboratory research that suggests post-fire promotion of Wild Rice is not a function of fire per se (neither heat or smoke) but is likely to be due to the removal of the smothering grass layer, even though fire is a efficient way of removing Para Grass

Generating Approximate Geographic Descriptions

Georeferenced data sets are often large and complex. Natural Language Generation (NLG) systems are beginning to emerge that generate texts from such data. One of the challenges these systems face is the generation of geographic descriptions referring to the location of events or patterns in the data. Based on our studies in the domain of meteorology we present a two staged approach to generating geographic descriptions. The first stage involves using domain knowledge based on the task context to select a frame of reference, and the second involves using constraints imposed by the end user to select values within a frame of reference. Because geographic concepts are inherently vague our approach does not guarantee a distinguishing description. Our evaluation studies show that NLG systems, because they can analyse input data exhaustively, can produce more fine-grained geographic descriptions that are more useful to end users than those generated by human experts.