Abstract
Limestone ecosystems in New Zealand contain disproportionately high ecological and botanical values. Over 150 native plant species are limestone specific (i.e., calcicolous), and of these, a third are classified as nationally critical. The main threat to the survival of many calcicolous species is competition from invasive weeds, particularly Festuca rubra L. subsp. rubra from the family Poaceae. Currently, there is no effective management strategy for this perennial grass. The aim of this study was to compare different removal methods for F. rubra rubra and to assess which of these methods are effective at promoting the establishment of two rare limestone species Gentianella calcis Glenny et Molloy subsp. calcis, family; Gentianaceae and Lepidium sisymbrioides Hook.f, family; Brassicaceae. This study was conducted to inform future management of rare New Zealand limestone ecosystems. Experiments were carried out at two field sites, Waipata Scientific Reserve and Wai O Toura Scenic Reserve, as well as under glasshouse conditions. Mowing, spraying and digging were used as control methods for F. rubra rubra on limestone ecosystems. Soil samples were collected to investigate the seed bank of both sites. Under glasshouse conditions, the growth of L. sisymbrioides was monitored under different management conditions. The growth and survival of nursery raised G. calcis calcis when translocated into different weed removal treatments was also monitored. Digging and removing grass and associated root mass was the most effective management technique for removing F. rubra rubra. Applying this mechanical removal technique on a larger scale should prove more effective as most of the bare-ground will be much further away from any external weed seed sources (aside from any remaining weed species seeds still present in the ground). L. sisymbrioides was found to grow better in higher light conditions. Future management of this species should consider planting L. sisymbrioides away from other, larger species that have the potential to shade it. G. calcis calcis planted into plots where F. rubra rubra and root mass had been mechanically removed showed, on average, the highest rates of survival, flowering output, and recruitment success when compared to the other treatments. The ‘Digging’ method on a larger scale would be an effective method for reintroducing planted G. calcis calcis grown in a nursery from seed, back in the wild, thus increasing the wild population.