![Sample our Environment & Agriculture journals, sign in here to start your access, latest two full volumes FREE to you for 14 days]({"type":"image" , "src" : "/sda/5934/TOC-Subject-Sample-2021-Environment-Agriculture.jpg"})
Abstract
The cover of the adventive heath Calluna vulgaris in seral tussock grassland of northern Tongariro National Park and the influence of C. vulgaris on the rates of indigenous shrub invasion of the grasslands were assessed by relating species canopy cover and height to environmental and temporal factors using generalised additive models. C. vulgaris now dominates virtually all of the area previously covered in Chionochloa rubra tussock grassland below 1200 m over 52 km2 on the northern ringplain. Only on basin floors, and the even frostier or poorly drained hollows, does C. rubra persist as a conspicuous species, but at generally less than 10% crown cover. Native shrubs are invading C. vulgaris shrubland in a process partly explicable in terms of time elapsed since the last fire, slope, topographical position, and altitude. On sideslopes at 900 m a.s.l. Leptospermum scoparium and Dracophyllum longifolium colonise and exceed the cover of C. vulgaris 38 years after burning; on crests the native shrubs take at least 60 years to dominate; and they take 75 years on basin floors. At 1100 m the times for this transformation are almost doubled. These slow rates of change, coupled with the extensive areas of early seral vegetation and the topographical dominance of crests and basin floors, point to C. vulgaris remaining a conspicuous component of ringplain landscapes for at least another 40 years.
Rates of native shrub invasion of tussock grassland without C. vulgaris showed somewhat faster initial rates, but little difference after 70–80 years.
