Bayesian classification of catchments using spatial data: a first step to improved modelling of catchment effects on stream ecological condition

A major challenge facing freshwater ecologists and managers is the development of models that link stream ecological condition to catchment scale effects, such as land use. Previous attempts to make such models have followed two general approaches. The bottom-up approach employs mechanistic models, which can quickly become too complex to be useful. The top-down approach employs empirical models derived from large data sets, and has often suffered from large amounts of unexplained variation in stream condition.

We believe that the lack of success of both modelling approaches may be at least partly explained by scientists considering too wide a breadth of catchment type. Thus, we believe that by stratifying large sets of catchments into groups of similar types prior to modelling, both types of models may be improved. This paper describes preliminary work using a Bayesian classification software package, ‘Autoclass’ (Cheeseman and Stutz 1996) to create classes of catchments within the Murray Darling Basin based on physiographic data.

Autoclass uses a model-based classification method that employs finite mixture modelling and trades off model fit versus complexity, leading to a parsimonious solution. The software provides information on the posterior probability that the classification is ‘correct’ and also probabilities for alternative classifications. The importance of each attribute in defining the individual classes is calculated and presented, assisting description of the classes. Each case is ‘assigned’ to a class based on membership probability, but the probability of membership of other classes is also provided. This feature deals very well with cases that do not fit neatly into a larger class. Lastly, Autoclass requires the user to specify the measurement error of continuous variables.

Catchments were derived from the Australian digital elevation model. Physiographic data werederived from national spatial data sets. There was very little information on measurement errors for the spatial data, and so a conservative error of 5% of data range was adopted for all continuous attributes. The incorporation of uncertainty into spatial data sets remains a research challenge.

The results of the classification were very encouraging. The software found nine classes of catchments in the Murray Darling Basin. The classes grouped together geographically, and followed altitude and latitude gradients, despite the fact that these variables were not included in the classification. Descriptions of the classes reveal very different physiographic environments, ranging from dry and flat catchments (i.e. lowlands), through to wet and hilly catchments (i.e. mountainous areas). Rainfall and slope were two important discriminators between classes. These two attributes, in particular, will affect the ways in which the stream interacts with the catchment, and can thus be expected to modify the effects of land use change on ecological condition. Thus, realistic models of the effects of land use change on streams would differ between the different types of catchments, and sound management practices will differ.

A small number of catchments were assigned to their primary class with relatively low probability. These catchments lie on the boundaries of groups of catchments, with the second most likely class being an adjacent group. The locations of these ‘uncertain’ catchments show that the Bayesian classification dealt well with cases that do not fit neatly into larger classes.

Although the results are intuitive, we cannot yet assess whether the classifications described in this paper would assist the modelling of catchment scale effects on stream ecological condition. It is most likely that catchment classification and modelling will be an iterative process, where the needs of the model are used to guide classification, and the results of classifications used to suggest further refinements to models.

Refuge in the land of liberty : France and its refugees, from the revolution to the end of asylum, 1787-1939

France has a long tradition of asylum for refugees. Since the Revolution, this has made it the land of liberty (pays de la liberte) and the land of asylum (la terre d'asile)." "In practice, responses have been shaped less by principle than by political and social conditions. Various refugee movements - from the late eighteenth-century Lowlands, to Spanish and Italian liberals in the 1820s, Polish nationalists in the 1830s. German social revolutionaries of 1848-9, anti-Bolsheviks from the Russian Revolution, Christians from the former Ottoman Empire, and Jews from Nazi Germany - have met with mixed responses, which shifted uneasily between sympathy, principle, pragmatism, and open hostility." "This book examines the tensions between refugee rights and political responses to refugees, and between humanitarian concern for their plight and hostility to their imposition on the state. Increasingly punitive measures against refugees saw, in 1939, the end of asylum in the internment of republican exiles from the Spanish Civil War.

A high altitude observation of the beautiful firetail Stagonopleura bella from East Gippsland, Victoria

There has been little research on the ecological requirements of the Beautiful Firetail Stagonopleura bella, and its habitat preferences are poorly understood. On mainland Australia, the Beautiful Firetail is generally considered to be a bird of coastal regions and the lowlands. This note reports an observation of Beautiful Firetails on the Great Dividing Range at a height of more than 1100 metres above sea level from an atypical habitat for mainland Australia. It appears that the observation may be the highest altitude at which this species has been recorded on the mainland.

Studies in supervisory practice : the effectiveness of the practicum in teacher education in the Northern Territory

In this thesis we descend into the swampy lowlands to meet with student-teachers and their supervisors and observe them working together at different sites across the Top End of Australia. In the process we discover the multiple relationships that comprise the practicum text and the discomforting untidiness and unwieldiness, as well as the awkwardness of complexity, which surrounds research into supervisory practice. The thesis demonstrates the need to attend to the subjectivities of the participants and highlights the conflicting attitudes, beliefs, interests, and desires which are only partially realised or understood. It moves us beyond language to the sentient world of anger, love, disgust, hope, fear, despair, joy, anguish, and pain and we become immersed in a murky, incoherent, interior world of hints, shadows, and unfamiliar sounds, a world of lost innocence and conflict in which knowledge is truly embodied. Encompassing a view of supervision as moral praxis, particular attention was given to the care and protection of the self and a romanticist conception of the self was seen to predominate. The thesis demonstrates the part played by positioning and agency in the process of subjectification, the importance of emotional and relational bonding in the emergence of collegiality, the tactics of power employed by supervisors, the struggle for personal autonomy, the presence of anxiety induced by failure to pro vide feedback, the inculcation of guilt, and the complex interplay of age-related and gender effects. Attention is also given to the degree to which supervisors adopt reflective and constructivist approaches to their work. The stories reveal that supervision is much more than advising student-teachers on curriculum content, resource availability and lesson presentation. It is a process of interiority in which supervisors may need to provide emotional support in the face of displacement and disorientation, and assume the role of an abiding presence, someone capable of imaginative introjection, someone who ‘knows’. Particular attention is paid to the language of supervision which was marked by indirection, diffidence, imprecision, irony, and understatement. At the same time, the agonistic nature of language associated with the politics of the personal is made apparent. Whilst in the opinion of Liaison Lecturers, context-of-site did not appear to matter as far as acquiring teaching competence was concerned, the failure to attend to context-of-site affected how student-teachers engaged with difference and diversity. In spite of attempts to contest the myths of Aboriginal education and interrupt the discourse of impoverishment, colonialist attitudes and resistance to liberatory education persisted. The thesis ends with suggestions for alternatives to the traditional practicum and discusses the introduction of Field-Based Teacher Education into Northern Territory schools.

Conservation of tropical forest tree species in a native timber plantation landscape

Tropical terrestrial environments are becoming dominated by anthropogenic land-uses, making retention of biodiversity in production landscapes of critical conservation importance. Native timber plantations may represent a land-use capable of balancing production and conservation by potentially supporting understorey plant and tree species otherwise restricted to old-growth forests, with little impact on yield. In this study we investigated the conservation value of native plantation forests in the lowlands of New Britain, Papua New Guinea. We compared the composition of tree species (≥10. cm DBH) of unlogged forest to those of different aged native Eucalyptus deglupta plantations and intervening (historically logged) secondary forests. We found a high capacity for biodiversity conservation within plantations, with 70% of forest tree species persisting in mature plantations (13-15. years old). However, compositional analyses revealed lower numbers of large individuals (≥10. cm DBH) in both late-successional and non-vertebrate-dispersed species in the plantations, indicating the difficulty of retaining mature old-growth forest trees in production land-uses. Secondary forest protected by conservation reserves was compositionally indistinct to unlogged forest. Our results demonstrate the potential for tropical native timber plantations to contribute to the retention of biodiversity. However, appropriate management is required to ensure the persistence of source populations of old-growth forest tree species. With careful planning a balance between production and conservation can be achieved in lowland tropical regions.