Vegetation classification in south-western Australia's Mediterranean jarrah forest: New data, old units, and a conservation conundrum

Abstract

Conservation reserve selection is guided by vegetation classification and mapping. New survey data and improvements in the availability of archived data through online data-sharing platforms enable updated classifications and the critique of existing conservation criteria. In the Northern Jarrah Forest Region of south-western Australia, percentage-based targets using 'forest ecosystem units' (15% of each unit) and the systematic conservation planning principles of 'comprehensiveness, adequacy and representativeness' underpin the State's reserve network. To assess the degree of community-level heterogeneity within the forest ecosystem units, new survey data for the forest (30 000 plots) were classified using a non-hierarchical clustering algorithm. Results were assigned to the National Vegetation Information System, and community groups defined at the Association level (Level V). Significant community level heterogeneity was found, including 15 communities in the dominant 'jarrah woodland' unit, and 13 in the 'shrub, herb and sedgelands' unit. Overall, this research highlights limitations in the current reserve system, including the influence of scale on percentage-based targets and 'representativeness'. A multi-scale approach to reserve selection, based on a quantitative, floristic, hierarchical classification system, would improve the level of scientific rigour underlying decision-making.