GEOLOGIC CONTROL ON PLANT BIODIVERSITY IN BANKS PENINSULA, SOUTH ISLAND, NEW ZEALAND

Rocky outcrops have a significant relationship with rare and endemic species by providing a safe haven from human influences on the land and a specific type of environment that is suitable for less common species, yet to what extent does the nature of the rock play? To investigate this relationship, we investigate what control does the underlying volcanic geology of Banks Peninsula have on the location and spread of rare and endemic species. We proposed a two-fold hypothesis: on a small scale we anticipated that the chemical makeup of different rock types is preferable to some species over others, and on a large scale we expected to see rocky outcrops create an extreme environment where only rare and endemic species, or exotics, can live. The study investigated five case studies of rare or endemic species across multiple environmental and geological gradients in Banks Peninsula. At each site, environmental and geologic features were recorded and rock and soil samples were collected and analyzed using a portable x-ray fluorescence (PXRF) to determine chemical properties. On a small scale, we found that for the species Hebe lavaudiana, there was a significant geochemical control on where the species could be found, most significantly around primary nutrient gradients. On a large scale, we found geologic structure and indirect geologic influences, such as the creation of a microclimate and ability to retain soil, both showed to have a significant control on where the remaining four species could live. While each species demonstrated a different primary geologic control to their location and spread, all five studies highlighted the relationship between geodiversity and biodiversity and the importance of rocky outcrops as unique habitats. This insight has just scratched the surface on this highlighted relationship and future studies are required that analyze these connections in order to create a framework for preservation of rare and endemic species.

Keywords: geodiversity, rocky outcrop, geochemical make-up, environment, habitat island, conservation, rare and endemic species, vegetation-environment relationship