Assessing the success of restoration plantings at Cape Foulwind, New Zealand

Abstract

Holcim (New Zealand) Ltd. operate a quarry near Cape Foulwind, New Zealand Quarrying operations have a dramatic effect on the environment. Consequently, the company has developed a restoration strategy that aims to mitigate the environmental and visual impacts of quarry operations. The objective of this study was to determine how successful the restoration plantings at Cape Foulwind have been to date. Achieving restoration success is dependent upon meeting the goals established for the restoration project. The specificity, appropriateness, and ease of measurement of these goals play a large part in determining the level to which restoration plantings can be deemed successful. The six planted restoration study sites investigated (planted 3 to 22 years prior to this study) were compared with three forest remnant sites, acting as a reference. Determination of the level of restoration success involved investigation of both ecosystem structure and functional attributes. Vegetation composition, ground active invertebrates and various ecosystem attributes, including soil, litter depth and decomposition, and seed rain were investigated using numerous diversity indices and ordination techniques where appropriate. The results of this study suggest that while complete success of these restoration plantings has not yet occurred, attributes necessary for initial success were present. Planted restoration sites were facilitating the entry of novel regenerating species. The current limiting factor to progression within the planted restoration study sites appears to be the lack of full canopy cover, and subsequent development of suitable microclimatic conditions. A large difference was apparent in composition and abundance of ground active invertebrate communities in planted restoration and remnant study sites. Of the environmental variables investigated, litter depth was found to be the key driver of invertebrate distribution over the nine study sites. Holcim's restoration plantings at Cape Foulwind have successfully provided new habitat for native biodiversity, while facilitating development of ecosystem structure and functioning. Importantly, they are increasing the connectivity between the native forest remnants that are present, enhancing the aesthetic appeal of the quarry area.