Skip to main content
Dryad

What factors influence the extent of midstorey development in Mountain Ash forests?

Data files

Dec 14, 2020 version files 382.37 KB

Abstract

The midstorey is a critical component of the structure of many kinds of forest globally. We constructed statistical models of the factors influencing the percentage cover of two dominant Acacia spp. (Montane Wattle [Acacia frigiscens]) and Silver Wattle [Acacia dealbata]) in the midstorey of Mountain Ash (Eucalyptus regnans) forests in mainland south-eastern Australia. We modelled the influence on the percentage cover of two these two species of Acacia of : (1) the age of the overstorey eucalypts (which corresponded to the time elapsed since the last major stand-replacing disturbance), and (2) environmental drivers (slope, aspect, elevation, and topographic wetness).

Stand age was an important factor influencing the percentage cover of both Montane Wattle and Silver Wattle. We found evidence of a non-linear, humped-shaped percentage cover-stand age relationship for the percentage cover of Montane Wattle, with the highest values in stands of Mountain Ash that were 30-60 years old. There were no differences in percentage cover among other age classes. The highest values for the percentage cover of Silver Wattle were for stands regenerating after the 2009 fire with markedly lower levels of cover in other age classes. There were no differences in cover between other age classes. Although our data contained evidence of inter-specific differences between Montane Wattle and Silver Wattle in their response to stand age, both species persisted as a midstorey component in old growth Mountain Ash forest.

 No environmental covariates influenced the percentage cover of Montane Wattle or Silver Wattle. Both tree species occur well beyond our study region and the set of environmental conditions we modelled may therefore not be limiting the occurrence of these tree species. We suggest that disturbance is the key driver of site occurrence of the Montane Wattle and Silver Wattle in the Mountain Ash forests of the Central Highlands of Victoria.