The salt-marsh vegetation of New Zealand
Haacks, Manfred; Thannheiser, Dietbert
Observations of salt-marshes were undertaken throughout the three main islands of New Zealand. The proportion of introduced vascular plant species – either deliberately or accidentally introduced – within the salt-marshes is, at 49 %, slightly higher than it is for New Zealand's vegetation in general. The bulk of species come from the Holarctic which can be explained by the history of European settlement and trade links. Observations of species richness along 13 degrees of latitude reveal an increase of species from the subtropical north of New Zealand to the cool temperate south. Altogether some 74 species could be found within the salt-marshes of New Zealand seven of them being endemic. As in other parts of the world, the most severe human impacts to salt-marshes in New Zealand are drainage, reclamation for industrial plants and agriculture. Furthermore, introduced species have not only altered the natural composition of salt-marsh communities, in some cases they have become established as solitary stands which cover sometimes large areas. Besides, the introduction of species have changed the topography of estuaries as well. By applying the phytosociological method of Braun-Blanquet, 27 associations and rankless communities of salt-marsh vegetation were differentiated and are presented in constancy tables. Three associations (Leptinelletum dioicae, Plagianthetum divaricati, and Puccinellietum walkeri) are endemic to New Zealand. The sigmasociological approach was also applied on the salt-marsh vegetation of New Zealand. As a result, the Juncetum kraussii Geosigmetum consisting of four vegetation complexes (sigmeta) was described. Resemblance of the New Zealand salt-marshes to those of Australia was discussed.