Physical and chemical drivers of vegetation in groundwater-source pools on the Bogong High Plains, Victoria

Abstract

The wetland communities intimately associated with groundwater sources in the Australian alps are poorly documented compared with the broader (and more obvious) alpine peatlands. In the present work, we report on the vegetation observed immediately around such sources and the characteristics of the supplying groundwater so as to understand the likely factors controlling the observed vegetation assemblage. Thirty-two groundwater sources were identified across three catchments on the Bogong High Plains, Victoria (Australia), and the vegetation associated with these sources surveyed. Groundwater sources occurred across a range of altitudes (1667–1854 m), independent of aspect, and were hydrologically connected to (upstream of) peatlands. Localised mounding adjacent to the groundwater sources resulted in the formation of pools (‘groundwater source pools’). The vegetation within the pools was dominated by bryophytes, with the aquatic bryophyte Blindia robusta the most common species. The groundwater was deficient in major ions, and similar to rainwater apart from elevated concentrations of CO2 accumulated in the groundwater-recharge process. The high CO2 concentrations, combined with the near-constant temperature conditions provided by sustained groundwater flow, are thought to be likely drivers for the high abundance of B. robusta. Although the relative contributions of rain and snow to aquifer recharge are not fully understood for the Australian Alps, these ecosystems are likely to be vulnerable to the changes in precipitation regime that are predicted under climate-change scenarios.