The origin and persistence of alpine vernal ponds in mineral soils

Little is known of the processes that create and maintain vernal ponds in mineral soils in alpine environments. On the Central Plateau, Tasmania, we tested the hypotheses that vernal pond complexes on mineral soils formed in response to the underlying topography of a glacio-fluvial plain; relate to present day topography; resulted from past damming by organic accumulation; are moulded by wind. The underlying topography did not relate to the surface ponds, nor were they on steeper slopes than adjacent areas without ponds. The morphology of the ponds and the morphological and edaphic characteristics of the pond complexes and adjacent areas are consistent with an origin by organic material damming. The strongest winds orientate most ponds, rather than the aspect of the slope. Sediments were preferentially caught on sticky traps to the northeast of the ponds, away from fierce prevailing southwesterly winds. Temperature measurements and fortnightly observation showed non-concordant patterns of variation in water levels in the ponds. We deduce that the complexes of vernal ponds may have formed in previous moister conditions more favourable to organic matter accumulation, possibly in the early Holocene, and are maintained by a faster rate of accumulation of mineral and organic particles in the tussock grassland adjacent to the ponds than in the ponds themselves. © 2019 John Wiley & Sons, Ltd.