Changes in western Waikato frost flat heathland, 2013/14-2021

Report: TR 2023/15

Authors: Mark Smale, Neil Fitzgerald, Norman Mason (Manaaki Whenua – Landcare Research)

The pre-European extent of frost-flat heathland is estimated to have been several tens of thousands of hectares but this has been reduced by an order of magnitude since c. 1930 by land development for agriculture and forestry to a few thousand hectares, mostly at one extreme site (Rangitaiki Conservation Area, Bay of Plenty).

The few intact remaining frost flats are highly fragmented and susceptible to a range of threats, such as weed invasion (especially contorta pine, Pinus contorta), climate change leading to a lighter and less frequent frost regime, and nutrient enrichment through topdressing drift. The influence of the surrounding matrix on survival prospects is unknown but is likely to be significant.

Permanent vegetation monitoring plots were established in the remaining substantial frost-flat heathlands in the western Waikato Region in January–May 2013 and in January 2014, and remeasured from April to June 2021. Changes in vegetation composition and structure over this period were assessed for Waikato Regional Council.