Subalpine gully‐head ribbon fens of the Lammerlaw and Lammermoor Ranges, Otago, New Zealand

Abstract

Vegetation patterns of subalpine gully‐head mires were investigated in the flat‐topped Lammerlaw and Lammermoor Ranges, South Island, New Zealand. Two intensively studied mires each consist of a series of peaty terraces and scarps. Terraces may contain pools, elongated downslope in the narrow, lower altitude mire, but across slope in the broader, upper mire. A crest occurs on some terrace lips, and marginal “spillways” (channel‐like zones) occur down some scarps. Some mires have drained by subsurface pipes. Vegetation analysis distinguished between grassland or herbfield on gully sides, vegetation of mire margins, showing aspect differences on the steeper, lower mire, and the vegetation of gully floors, including oligotrophic mire centre vegetation and species‐poor pools. The crests, though warmer, bore no special vegetation type. Mineral soil beneath the peat indicates a previous non‐mire vegetation, which has subsequently paludified. Scarp slumps indicate downslope creep of organic material. Peat fissures, and mineral, vegetation, and erosion dams all appear to have initiated development of some pools. Mires are designated gully‐head ribbon fens. Patterning appears to be accentuated because of the mires’ gully‐head location on broad‐topped ranges, and drainage of soligenous water from upslope gully sides. These apparently unique fens give insight into patterning in aapa mires, and merit special conservation.

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