An unusual climbing dune, Big Hellfire Pass, Stewart Island, New Zealand: exploration through environment, vegetation and trait patterns

Abstract

Big Hellfire Dune on the western coast of Stewart Island/Rakiura, New Zealand, is an unusual dune climbing 220 m in altitude on the Ruggedy Range, to dissipate on the leeward side of Hellfire Pass. To record vegetation and environmental characters we ran six transects parallel to the coast, at 50‐m altitudinal intervals up the dune. Topography reflected substrate and sand deposition patterns. Wind speed was higher further up the dune, and conductivity and water content were lower, while organic matter and pH did not change. The dune has a rich native flora, with very few exotic species. Analysis defined four plant communities, reflecting openness, and cover of Ficinia spiralis , extent of marginal shrubland of Brachyglottis rotundifolia , and presence of some forest species. The adaptive ability of dune plants was investigated in relation to altitude, using leaf traits. The most widespread species B. rotundifolia and F. spiralis adapt with thicker, shorter, wider leaves, shorter petioles and lower specific leaf areas closer to the coast, and again at the Pass. Vegetation patterns appear to be driven by rainfall and the stability of the fine, even‐sized sand, not by altitude. Anthropogenic disturbances from invading weeds and trampling from exotic mammals threaten Big Hellfire Dune, requiring monitoring to protect this unusual climbing dune.

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