Limestone erosion pavements
Erosion pavements scattered amongst grassland Matiri Range, western Nelson (Peter Williams)
Erosion pavements are flat to gentle slope areas that have been bared of topsoil formed through chemical weathering. They may or may not have large cracks and fissures, depending on rock type, that do not support gravel or colluvium and occur on ridges, mountain tops and plateaux rather than on tors or rock stacks. They do not include coastal turfs, even where these occur on coastal erosion pavements. They range in size from small inter-tussock spaces to patches many metres across. They commonly support only small appressed herbs, e.g., Craspedia spp., Epilobium spp., Raoulia spp.
Synonyms
Alvar
Where do they occur?
They are scattered through the South Island lowlands in association with Amuri limestone from south Marlborough to north Otago, wherever the regolith has been stripped by water and wind. They have probably dramatically increased in frequency and area since humans arrived, due to grazing and burning. Most lowland limestone escarpment in dry eastern South Island have their upper margin, convex creep slopes stripped of their previous regolith to expose an underlying pavement They are particularly common on the subalpine limestone plateaux of western Nelson.
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Limestone erosion pavements:
Presence by Region -
Limestone erosion pavements:
Presence by Territorial Authority
Notable flora and fauna
Threatened and rare plants include nationally critical moonwort (Botrychium lunaria), Chaerophyllum basicola, Mt Burnett sedge (Carex dolomitica), Castle Hill forget-me-not (Myosotis colensoi), Crassula multicaulis, simplicia (Simplicia buchananii), Gentianella calcis subsp. calcis, Melicytus aff. obovatus (c) CHR 393733; Mt Owen) and Ranunculus (a) (AKU 19876; Hope); nationally endangered Melicytus (a) (CHR 355077; Matiri Range); declining Tetrachondra hamiltonii and range restricted Craspedia sp. (f), and Carex calcis. Naturally uncommon species include Poa sudicola, New Zealand anemone (Anemone tenuicaulis), Enys sedge (Carex enysii), Myosotis spathulata, and limestone cushion poa (Poa acicularifolia subsp. acicularifolia).
No information is available on threatened and rare fauna.
Threat status
Not threatened (Holdaway et al. 2012)Threats
Introduced gasses and flatweeds can be invasive, especially along fissures and cracks. Grazing by deer or large mammals is likely to be a problem only where there is sufficient foliage, but hares have been noted eating even individual plants in the middle of pavements. Ironically, as described above, farming and stock grazing have probably increased the overall area of limestone erosion pavement. As with all limestone features, mining can be an issue.
Further reading
Bell CJE 1973. Mountain Soils and Vegetation in the Owen Range, Nelson 2. The Vegetation. New Zealand Journal of Botany 11: 73-102.
Druce AP, Williams PA, Heine JC 1987. Vegetation and flora of Tertiary calcareous rocks in the mountains of Western Nelson, New Zealand. New Zealand Journal of Botany 25: 41-78.
Heine JC, Williams PA, Druce AP. 1987. Soils of Tertiary calcareous rocks in the mountains of Western Nelson, New Zealand. New Zealand Journal of Botany 25: 17-40.
Links
Limestone Pavement Conservation (United Kingdom)