Deschampsia cespitosa subalpine tussockland on the Green Lake landslide, hunter mountains, Fiord ecological region, New Zealand

Abstract

The tussock grass Deschampsia cespitosa, considered to be conspecific with the very polymorphic taxon which is cosmopolitan in temperate and cold regions, is currently classed amongst the 62 "vulnerable" indigenous vascular species for New Zealand. Previously more widespread here, the species' demise in certain regions within the last century has been attributed to grazing and/or competition from aggressive introduced grasses. This study provides the first quantification of the flora, vegetation, and soil of an indigenous grassland stand dominated by D. cespitosa. Cover-abundance data were recorded from 15 randomly placed quadrats in a localised intact stand of D. cespitosa subalpine tussockland, occupying an ancient landslide depression in eastern Fiordland. These data are related to comparable information gathered from adjacent, more extensive, Chionochloa rubra ssp. cuprea (copper) tussockland. Multivariate analysis confirmed the distinction of the two stands in terms of species abundance but indicated continuous floristic variation among the 51 plant taxa recorded. The floristic similarity for the two stands was 49%, which was not statistically significant, whereas that for the cover-abundance data was only 5%. Soils under the site-specific D. cespitosa stand were classified as silt loams while those of the C. rubra ssp. cuprea (copper) tussockland are sandy clay loams with water content, organic matter, and root mass all much higher in the former. The Fiordland population showed no signs of grazing use despite the presence of introduced herbivores. Only one non-aggressive grass, amongst the three exotic species, was recorded. On the basis of this study, D. cespitosa tussockland is proposed as a new indigenous vegetation type for New Zealand.