Vegetation succession and recovery of ecological values in the southern Queensland Brigalow Belt

Abstract

Broadscale land-clearing in the Queensland Brigalow Belt has resulted in widespread decline in ecological values including biodiversity loss and impairment of ecosystem processes and functions. More than 90% of brigalow ecological communities, i.e. those that have Acacia harpophylla, F. Muell. ex Benth (Brigalow) as a dominant and co-dominant, have been entirely cleared or severely degraded in recent decades. In spite of this wide-ranging disturbance, partial ecological recovery may be possible in the Queensland Brigalow Belt through the retention of regrowth brigalow stands. Few studies, however, have quantitatively examined brigalow vegetation succession, particularly in the context of cost-effective ecological restoration. This study used a chronosequence approach to examine how species richness, abundance and structure change in brigalow woodlands with years since clearing. Floristic and structural characteristics were surveyed in 18 brigalow stands, of varying years since clearing, in the southern Queensland Brigalow Belt. Linear models were fitted for years since clearing versus total number of woody species, tree cover, shrub cover, herbaceous cover and litter cover. Regrowth brigalow communities were found to follow the inhibition model of succession, with Acacia harpophylla assuming dominance. The linear models suggested that at least 90 years of recovery would be required post-clearing, before regrowth woodlands regained 90% of the species richness and structural characteristics of mature woodlands. Management practices such as thinning the dominant species and allowing for the accumulation of logs and litter may be necessary for promoting recovery of vegetation diversity and structural heterogeneity.