Created dune slack wetlands effectively host rare early successional turf communities in a dynamic dunefield, New Zealand

Abstract

Dune slack wetlands should be relatively unhindered by challenges in recovering the hydrology, geochemistry and biological structure affecting other created habitats, thus presenting a simple exemplar of restoration’s success. The Manawatū coast, New Zealand, has one of the most actively prograding parabolic dunefields in the world. In 1992 a study of Tawhirihoe Scientific Reserve, Tangimoana, first described three significant wetlands in dune slacks, the floor of these wetlands containing several rare perennial turf-forming species (<4 cm tall), which were in decline. A practical experiment creating wetlands in 1996 resulted in appropriate turf habitat, and was repeated on a larger scale in 2008. A survey of the vegetation and environment of the 3 natural and 3 created wetlands was conducted in 2009–2010 summer. Seven vegetation communities were identified, the three earliest successional communities containing rare turf species. The largest wetland contained the broadest range of communities, but other natural wetlands were successionally older. The most recently created wetland has only the earliest successional phase. All wetlands progressively infill with aoelian sand over the decades, rates depending on their locations and sizes, accelerating succession to exotic vegetation. Turf communities containing rare wetland plants appear to exist for only about two decades, highlighting their temporary nature. Deliberate wetland creation remains the most promising management strategy for their perpetuation in small reserves within dynamic dunelands, but even in these simple environments, restoration impediments are easy neither to predict nor to forestall.