The timing and nature of floristic and structural changes during secondary succession in wet forests

Abstract

The timing and nature of floristic and structural changes to vegetation were documented during secondary succession in wet forests in the Victorian Central Highlands from 3 to > 100 years after severe disturbance by timber-harvesting or wildfire. A chronosequence of five forest age-classes was employed. Vegetation surveys were conducted in two 15 × 50 m sampling quadrats in each of 12 replicate sites in each forest age-class between April 2000 and June 2001. Frequencies of occurrence of 67 floristic variables (plant taxa, other vegetation elements and litter components) were used to distinguish among plant communities in the different forest age-classes. Structural comparisons were made among the age-classes using species richness, floristic variability (i.e. spatial heterogeneity), trunk diameter and stem density of Mountain Ash Eucalyptus regnans F.Muell. and heights of forest strata. Most patterns of change showed a clear unidirectional trend from the youngest to the oldest age-class. Much of the floristic change occurred within a few decades of disturbance, but some of the structural changes continued throughout succession. Vegetation changes were generally attributable to natural succession, but a few differences between young forests that regenerated after timber-harvesting and older forests that originated after wildfire were likely to be due to the different disturbance histories. The pattern of vegetation change during secondary succession in forests after severe disturbance can influence the pattern of forest use by birds. The findings of this study thus formed the foundation of an examination of the community and behavioural responses of diurnal birds to secondary succession.