ENVIRONMENTAL RELATIONSHIPS OF FLORISTIC VARIATION IN THE ALPINE VEGETATION OF SOUTHEAST AUSTRALIA

Australian alpine vegetation is confined to the southeast of the conti nent and the island of Tasmania, it exhibits strong geographic pattern s of floristic variation. These patterns have been attributed to varia tion in edaphic conditions resulting from geographic variation in subs trate, climate and glacial history. This edaphic hypothesis is tested using floristic and environmental data from 166 quadrats distributed t hroughout the floristic and geographic range of Australian alpine vege tation. Environmental vector fitting in three-dimensional ordination s pace, the number of significant environmental differences between all pairs of 17 floristic groups and overall statistical analyses of the e nvironmental differences between communities suggest a primacy of clim atic variables over edaphic variables in explaining the broad patterns of floristic variation. Continentality, summer warmth, summer rainfal l and winter cold all provide a better statistical explanation of flor istic variation than the most explanatory of the edaphic variables, ex tractable P. The environmental variables that best discriminate the gr oups at each dichotomy of the divisive classification of the floristic data are largely climatic at the upper two levels, with edaphic, topo graphic and biotic variables being generally more important than clima tic variables at the lower levels. Many of the edaphic variables that were most important in discriminating dichotomous groups were relative ly insignificant in the broader analyses, suggesting that it is import ant to partition large data sets for environment/floristic analyses. T he results of such partitioning show that the environmental factors mo st important in influencing floristic variation in alpine vegetation i n Australia vary by location and geographic scale.