drylands

Woody plants in arid and semi-arid environments may enhance soil nutrient status, the so-called ‘fertile island’ effect, but this mechanism has never been tested in the drylands of New Zealand. In this study I investigated effects of Kunzea serotina, Discaria toumatou, Rosa rubiginosa, and Coprosma propinqua on soil properties in the drylands of central Otago, New Zealand. Soils had significantly higher organic matter under C. propinqua and significantly higher nitrate and phosphorus concentrations under K.

New Zealand has a unique opportunity to reshape the future of 1.2 million hectares, or 5% of the country. Since 1990, land clearance and development in the South Island high country have removed large areas of native vegetation, destroying already tenuous endemic species populations, and rare and threatened ecosystems. Important ecosystems and ecological values have been subtly or dramatically degraded through tenure review, discretionary consents, and invasions of plant and animal pests.

In many New Zealand dryland grass and shrubland areas, native and exotic woody species are invading, but it is unclear what environmental factors favour native dominance. One possibility is that differences in soil nutrients and moisture, or a combination of these factors, differentially affect the growth and hence invasive potential of native and exotic woody dryland species. We tested the prediction that native woody species outperform exotic woody species under low-nutrient and dry soil conditions.

The introduced brushtail possum (Trichosurus vulpecula) is the most important wildlife host of bovine tuberculosis in New Zealand and is considered to be a major environmental and agricultural pest. Dry grassland ecosystems in New Zealand include some of the least protected and most threatened native biota. Drylands cover 19% of the country, but there is little published information on the population density of invasive brushtail possums in these environments, and previous estimates are not based on quantitative methods.