Spatial and Temporal Patterns in the Dry Seasonal Subtropical Rainforests of Eastern Australia, with Particular Reference to the Vine Thickets of Central and Southern Queensland

Abstract

A study was undertaken of floristic patterns in remnant dry seasonal rainforest (semievergreen vine thicket) in central and southern Queensland. Quantitative (basal area and canopy cover) and binary vegetation data were collected from 75 sites using a multiple nearest-neighbours sampling technique. Areas covered by samples varied between 0.025 and almost 0.1 ha. Approximately half the sites occurred on fine-grained sediments, chiefly siltstone, shale and mudstone. Mean numbers of species in sample of (32) canopy trees ranged from 14 in south-eastern Queensland to 7 in the Central Highlands region. Many of the latter stands were dominated by 'Macropteranthes leichhardtii'. Data were analysed using a range of classificatory and ordination procedures. An agglomerative procedure using the Bray-Curtis coefficient and UPGMA clustering provided more satisfactory groupings of sites than divisive methods. Eight site groups were distinguished on the basis of cover data for tree and shrub species and were described in terms of structure, site features and frequent species. Presence/absence data from the sites were incorporated into a regional floristic database covering the Brigalow Belt Biogeographic Region. There was broad agreement between the species and community patterns from the detailed survey and the bioregional analysis, with 3-4 coastal and subcoastal vine thicket groups and 3-4 inland groups ... Over the 20-25 years since establishment of the transect, there have been significant changes in species composition and abundance in both the vine thicket and the brigalow/vine thicket communities. Numbers of species have increased overall in both communities, hut abundance of some species, notably 'Acacia harpophylla' and 'Opuntia tomentosa', declined. There has also been an increase in numbers of intermediate and larger stems (>2.5cm diameter), hut an even larger decrease in smaller stems (>30cm high, but <2.5cm diameter). There results suggest that no effective recruitment has occurred since establishment of the transect. The results from Brigalow Research Station are discussed in relation to broader species and community patterns in vine thickets.