A Proposal for the Classification of Tree-Dominated Vegetation in Australia

Abstract

None of the systems for classifying natural vegetation in the northern hemisphere can be satisfactorily applied to the Australian vegetation. Current Australian systems are also inadequate, being simplistic, covering only part of the range of vegetation or being based on extrinsic environmental attributes. The system proposed here for tree-dominated natural vegetation in Australia is based on a hierarchy of intrinsic attributes. It aims to establish classes, which can accomodate any community of tree-dominated natural vegetation in Australia, in a structured system with various scales of resolution (levels of clustering) based on physiognomy, floristics and spatial occupancy. The classification is intended for use in organizing vegetative data for general purposes, for relating information derived from special classifications to the vegetation as a whole and for comparing vegetation patterns with patterns of environment or disturbance. The physiognomic attributes of growth form and foliage type of the dominant layer define formation classes and formations respectively. Growth form of the subordinate layer(s) defines subformations, while physiognomic types are based on leaf size, phenology and stand complexity. Floristic attributes are used to determine generic classes, alliances and associations. Spatial attributes (height and density of dominants) with six classes in each are used to describe the space occupied by the stand, which is largely the result of recent growing conditions and the history of disturbance. This system avoids the implication of environmental attributes in terms such as rainforest, swamp forest or alpine woodland, and the use of structural stereotypes such as closed-forest or tall open-forest. Clumpwood is introduced as a new formation class, characterized by woody plants with multiple stems arising from lignotubers, rhizomes or roots. Clumpwood is a class equivalent to woodland (dominated by short-boled single-stemmed trees) and shrubland (dominated by shrubs with a single stem that branches at or near ground level so that no trunk is formed). Clumpwoods are widespread and floristically diverse; the best-known examples are composed of mallees, which are multistemmed plants of Eucalyptus.