Distribution, composition and environmental correlates of high-altitude gravelly pavement herbfields in north-eastern Victoria, Australia

Abstract

Context Gravelly pavement herbfields are a rare, geographically restricted community found in high mountain areas of south-eastern Australia. Gravelly pavement plant communities occur where there is continuous waterflow, with vegetation comprising sparse, semi-aquatic species on a rock or gravel substratum. Aims This study aimed to further the understanding of the community on the Bogong High Plains, Victoria, by asking questions relating to their location, structure and floristic composition. In particular, we ask what determines the distribution of pavement communities at the landscape-scale; and what abiotic factors govern between- and within-site vegetation patterns? Results Gravelly pavement communities were associated with groundwater outflows and are likely to be formed by an interaction between surface waterflow and slope. This work adds to the current understanding of wetland types in high-mountain Australia because, to our knowledge, this relationship has not been previously described. Floristic patterns vary with slope and elevation, with high-elevation pavements on steep slopes being floristically dissimilar to those at lower elevation on flatter slopes. Species richness was consistent across sites and only a few species were found at high abundance. Within-site patterning is apparent in most pavements, attributable to abiotic factors such as rockiness and water availability, leading to characteristic vegetation patterns. Species such as the sedge Oreobolus pumilio occur on the margins of pavements where water levels are variable, whereas forbs such as Psychrophila introloba are typically found in the middle of pavements where there is constant water supply. Conclusions Gravelly pavement communities are groundwater-dependant ecosystems, restricted at the landscape-scale and contain many rare species and, as such, deserve higher levels of protection than is currently offered.