Predicting spatial variation in the upper limit of trees on the alpine mountains of Lutruwita/Tasmania

Climate change threatens obligate alpine plants with restricted distributions, especially where mountain peaks are not far above the climatic treeline (henceforth ‘treeline’), as in Lutruwita/Tasmania where there are at least ten plant species that are only known to occur above the treeline and many more that only occur in alpine vegetation above and below the treeline. In a context of global warming, it is important to know the elevation of the treeline on each of the numerous alpine habitat islands in the state. Using the satellite image and contour layers in LISTmap, the highest elevation of trees on 49 alpine islands that had peaks above their treeline was determined. I then derived a predictive equation that explained 80.1% of the variance in this dataset and applied it to 141 alpine peaks. This analysis indicated that there were ten peaks on which the modelled treeline was more than 250 m elevation below the summit and 12 peaks on which the modelled treeline was more than 125 m in elevation above the summit. These results indicate that species extinctions in the alpine zone may not be imminent but are possible, especially for the eight Tasmanian endemics that are only known from above the treeline. Modelling of alpine lower limits and of the environmental ranges of the potentially threatened species is desirable.

Keywords:

alpine, climate change, climatic treeline, Lutruwita, Tasmania.