Academic literature on the topic 'Chionochloa rigida'

The effects on soils and vegetation of 13 years of fertilising and grazing on previously unfertilised South Island high country are described. Vegetation cover, and the values of organic carbon, nitrogen and pH in topsoils at 38 sites sampled on a high country farm in 1978 and 1979, before any topdressing or oversowing had been begun, were compared to values at the same sites in 1992, after soils had been progressively fertilised with a total of 1100 kglha of 28% sulphur-superphosphate and oversown with legumes. In 1992 the cover of native species such as silver tussock (Poa cita), narrow-leaved snow tussock (Chionochloa rigida) and scabweed (Raoulia australis) and the area of bare ground had declined relative to cover of these species in 1978179, whereas cover of introduced pasture species tolerant of grazing had increased. Mouse-ear hawkweed (Hieraciurnpilosella) was recorded at only 4% of sites in 1978179 but was present at half the sites in 1992. Organic carbon in topsoils rose from a mean value of 3.3% in 1978179 to 5.5% in 1992. There was insignificant change of total nitrogen values. The pH of topsoils (0-7.5 cm) declined at 36 out of the 38 sites. The average pH decline was 0.41 units (from 5.81 in 1978179 to 5.40 in 1992), and the largest pH decline was 0.7 pH units. Results from an additional seven sites outside the main survey area suggest that the pH decline occurs on upper midslopes and near-ridge sites (about 10% of the land area) rather than on lower midslopes and toeslopes. If topdressing and the associated pH decline continue, then by the year 2005, pH will be close to 5.0 in topsoils, and lime will be needed to maintain legume-based pasture production on the affected soils. Approximately 1 tonne of lime per hectare every four years is estimated to be required to offset the pH decline. The present (1993) cost of applying lime is about $5.50 per stock unit per year and on present returns from livestock and wool, liming would be uneconomic.

This thesis set out to examine the soils, plants, lichens, invertebrates and common skinks along a gradient of habitat modification. This gradient was represented by ten study sites, of varying management histories, in a mid altitude tall tussock (Chionochloa spp.) grassland in eastern Central Otago. One extreme of the gradient was represented by intact tall tussock plants with a high density of inter tussock vegetation. The other extreme was represented by intensively managed exotic pasture. Native plants, invertebrates and reptiles were present along the entire gradient of modification and there was a clear threshold in the diversity of native plants along the gradient. This threshold was reached after the management practice of ploughing was applied to a site. Sites that had not been ploughed were found to be similar in their native plant diversity, and all unploughed sites had significantly higher native plant diversity than unploughed sites. There was considerable variation in the abundance of individual plant and Coleoptera species along the modification gradient. The most intensively modified sites had the lowest plant diversity, the lowest abundance and diversity of Orthoptera, as well as the lowest abundance of common skinks. Sites with low levels of modification contained a higher abundance of common skinks, and, native forbs, lichens and bryophytes than the more intensively modified sites. With regard to individual plant and Coleoptera species recorded, there were generally not clear thresholds for their presence and absence along the modification gradient. Rather, there was a gradual turnover for most species along the gradient such that the plant and Coleoptera community at opposing ends of the gradient had less species in common sites of similar modification levels. A high proportion of the Coleoptera species observed were present in all sites, suggesting that disturbance has selected for an adaptive generalist life trait, and that the species remaining comprise the resilient portion of the Coleoptera fauna. The relationship between Coleoptera communities and the gradient of modification was scale dependent, with the strongest relationship being observed at the largest scale measured. The hypothesis that faunal diversity and abundance would be best predicted by the structural diversity of the vegetation rather than by plant species diversity was tested. Structural diversity was strongly correlated (p < 0.01) with Coleoptera diversity, and Coleoptera abundance whereas plant species diversity was not. However, plant species diversity was a stronger correlate of common skink abundance than plant structural diversity. The structural diversity of the vegetation has the potential to be measured remotely and could be a correlate for faunal diversity and abundance when undertaking landscape scale studies. This thesis demonstrates that native biota exists within the agricultural environment of the mid-altitude tall tussock (Chionochloa rigida) grasslands of eastern Central Otago despite intensive modification in some areas. The findings suggest that it is possible to integrate the objectives of agriculture and the conservation of some faunal groups especially for the more resilient species. However, this study also indicates that relatively unmodified sites are valuable reservoirs of biodiversity in the mid altitude zone and it is recommended that the limited number of lightly modified sites that remain in the mid altitude zone be conserved.