Soil Changes Associated with Cessation of Sheep Grazing in the Canterbury High Country, New Zealand

Soil degradation has been implicated as a cause of the poor vegetation condition over much of the unimproved tussock grassland in the South Island high country and as a threat to the sustainability of extensive pastoralism (Parliamentary Commissioner for the Environment, 1991; South Island High Country Review Working Party, 1994). A key requirement for assessment of sustainability is an ability to monitor indicators of temporal trends in natural resources such as soils and vegetation, and to understand the impact of land use on these trends (Basher, Floate and Watt, 1992). Vegetation degradation (e.g., loss of biomass and species diversity) in the presence of grazing by stock, and subsequent recovery in the absence or reduction of grazing has been documented at many sites in the Canterbury high country (e.g., Scott, Dick and Hunter, 1988; Rose, Platt and Frampton, 1995; Treskonova, 1991). The extent of soil changes associated with this degradation is less clear. However, loss of organic matter and decline in soil nutrient status has been implicated as a cause of Hieracium spread in the high country (Parliamentary Commissioner for the Environment, 1991). L.R. BASHER and I.H. LYNN