Controls on the Development of Vegetation (240 KB)
A positive feedback mechanism is identified whereby the development of vegetation depends on its level of development. The implications for land use impacts such as global warming are identified.
Shrub Encroachment in Woodlands (173 KB)
Around 40 years of observations are summarised to identify how woodlands develop and function, and how they respond to land use impacts. Key deficiencies in knowledge are identified.
Structural Classification of Vegetation (update) (200 KB)
Structural vegetation classifications were developed to identify relationships between vegetation and the environment. They have increased in importance with global warming as vegetation structure is significant for levels of carbon sequestration and potential rates of CO2 fixation. Anomalies in the scheme most used to classify Australian vegetation are identified and the scheme developed to increase applicability and remove anomalies without increasing complexity.
Vegetation: Continuum or Discrete States? (1MB)
Environmental legislation treats vegetation similarly to species when they have very different attributes. A key issue is whether vegetation forms discrete states, as with species, or a continuum. This issue is addressed by way vegetation survey results for central Queensland, central Sweden, and SW Queensland. The conservation implications of the conclusions are discussed.
Conservation Aspects of Vegetation Dynamics (368 KB)
Legislation on conservation has evolved through protection to preservation with the requirements often relating to values rather than entities. This focus on preservation denies a fundamental characteristic of biology that populations and communities inevitably change if only because of the life cycles of individuals. The implications of plant life cycles for the development and sustainability of particular forms of vegetation are examined.
Competition between trees and grasses (120 KB)
In this paper soil factors affecting the competition between trees and grasses are examined.
Acacia - Eucalypt Strategies for Water & Nutrients (116 KB)
The relative distribution of eucalypt and acacia dominated communities is characterised by acacias dominating on clay in a broad band across central Australia and eucalypts elsewhere. These patterns are examined relative to the physiological characteristics of the species, the amount and seasonality of water availability, its moderation by soils, and their effects on nutrient availability.
Tree Recruitment in a Poplar Box Woodland (161 KB)
The density of recruitment of poplar box and shrub seedlings was measured in intact poplar box woodland vegetation and adjacent woodland areas that had been subject to various impacts. The results are used to demonstrate the dependence of the recruitment of poplar box on the density and hence life cycles of the trees.
Analysis of competition in spruce-pine-birch communities in Central Sweden (263 KB)
Estimates foliage abundance for different plant components in spruce, pine, and birch forests in central Sweden were used to examine competitive relations between species in different environments. It is suggested that the relative dominance of tree species reflects the interaction between water and nutrients in plant competition. The competitive situation for the understory components varies with the tree species. In the floristically simple system structurally complex systems can be obtained where few factors operate.
Component Replacement of Trees, Shrubs & Grass in a Poplar Box Woodland interpreted from Spatial Variability (275 KB)
The relative amounts of foliage of the plant components of Eucalyptus populnea woodland systems were measured and interpreted as points in a replacement series. The lack of mutual exclusion between components was not satisfied and this is attributed to incomplete resource utilisation. It is suggested that environmental variation is confounded with temporal variation such that woodlands do not represent states of full utilisation of resource.
Effects of fire & mowing on mixed Themeda - Heteropogon grasslands (128 KB)
Effects of season and frequency of fire and mowing on Themeda, Heteropogon and `other grass species' were evaluated in experimental plots in central coastal Queensland. The relative proportions of grasses were little affected by burning but mowing strongly promoted Themeda. It is concluded that the change in dominance from T. triandra to H. contortus in grazing lands is due to the grazing rather than fire.
Effects of tree killing & livestock in a poplar box (Eucalyptus populnea) woodland on ground layer vegetation & some surface soil properties (379 KB)
Effects of killing trees and grazing were investigated by measuring ground layer vegetation and surface soil properties along transects between trees in poplar box systems. There were marked gradients away from trees for virtually all variables and these were used to evaluate impacts. All impacts from grazing were adverse whereas tree killing produced both adverse and beneficial changes. It is concluded that there is unused potential for herbage production in the cleared grazing land but it would be difficult to sustain.
An evaluation of water balance for heath vegetation using simulation (754 KB)
Water balance was simulated using 70 years rainfall data for Pinaroo for different vegetation types. Results are compared with native heath vegetation which tends to an optimum pattern of water use in two locations. Plants introduced with agriculture are unlikely to achieve such an optimal pattern of water use.
Water potential of trees and shrubs in intact & modified poplar box (Eucalyptus populnea) woodlands (213 KB)
Measurements of dawn water potential were obtained for trees and shrubs growing within plots in adjacent brigalow and poplar box communities. Shrub water status was enhanced with tree killing but this relationship is confounded by grazing. The results are discussed in relation to rooting distribution and non-uniform profiles of soil water potential.
Suppression of Wheat Growth by Different Tree Species (95 KB)
Change in the height of wheat away from the boles of different native tree species was measured when crop development depended largely on stored soil water. The suppression of wheat varied with species demonstrating that species selection for shelter belts will affect pasture growth.
On the Relationship Between Vegetation Classification & Environmental Association (280 KB)
The validity of an assumed correlation between vegetation and the physical environment is examined and the implications considered in relation to the classification of vegetation. It is concluded that plant competition limits the usefulness of current classificatory methods and that elucidation of community-environment interrelationships requires methods which allow separation of environmental and competitive effects.
Vegetation Mapping Issues (305 KB)
This paper briefly addresses some of the fundamental issues in vegetation classification and mapping.