AbstractThis thesis compares tree responses in naturally evolved and cultivated arboreal landscapes of Monsoonal Northern Territory. It examines the interactive effects of the carbon, hydrological and nutrient cycles, and cyclone and associated fire impacts influenced by climate, topography and soils, linked to geology.
Carbon stock in these arboreal communities increases linearly with stand basal area. Post-1940 increases in available moisture have tended to reduce tree carbon accumulation in disturbed savanna woodland, linked to stimulated grass growth, whereas in undisturbed monsoon rainforest and cultivated trees, growth rates have increased. Growth and, inversely, root failure in cyclones is positively correlated with topography-regulated drainage, which increases, and soil depth, which decreases with slope and elevation.
Both native and cultivated dicotyledon, rainforest, and particularly deciduous species have higher carbon assimilation rates and, apart from legume trees, higher storm tolerance than most evergreen species, such tolerance increasing with height and diameter. The reverse applies to palms, with both phyla showing a curvilinear response to taper.
Depth trends of vital nutrients, affecting fine root development, and failure, are more strongly correlated with soil organic carbon decrease than clay increase. Tree root density, and both moisture and nutrient decrease, is highest in the strata where these depth trends intersect. Carbon accumulation in response to nutrient cations is generally negative for native, and positive for cultivated trees, both increasing with Nitrogen and Phosphorus.
Tropical Cyclone Tracy altered the demographics of arboreal communities along the tracts — inland and, based on house damage patterns, radially from the cyclone centreline. The hypothesis that trees protected houses during TC Tracy was supported by empirical data in Darwin’s newer northern suburbs, but not in the older southern suburbs. There is sufficient evidence in this thesis to suggest that well-planned and well-managed urban tree cover can play important protective roles ameliorating microclimate, sequestering carbon and mitigating cyclone impacts in tropical, monsoonal cities.
|Date of Award||Mar 2010|
|Supervisor||Guy Stuart Boggs (Supervisor), Diane Pearson (Supervisor) & Andrew Campbell (Supervisor)|