Abstract:
Assessing the success of ecological restoration projects is necessary to justify the use of ecological restoration in natural resource management. The term success, however, is much debated within the field of restoration ecology. This study aims to determine measures of success and evaluate private revegetation plantings within the Rodney District, North Island, New Zealand. Under the Resource Management Act, Auckland District Council: Rodney offer greenfield restoration as a tool for mitigation of environmental effects to landowners wishing to subdivide. The scheme – Rule 7.14.4 was the first of its kind where applicants are required to produce a pre-planting site assessment, planting plan assessment and monitoring program to ensure a 90% plant survival rate until a five-year council sign off point. Little to no monitoring occurs after this council sign off. This study uses vegetation structure and composition as tools for measuring success over time. Three questions were asked to determine the level of success: One question based on structural success - “Has a forest of any kind been established?” using Ministry for the Environment forest criteria of 5m canopy height and 30% canopy cover. And two questions on compositional success - “Is this forest predominantly native?” measured using compositional characteristics “Is the forest similar to remnant forest within the area?” measured using comparisons to three reference ecosystems of remnant forest within the Rodney District. Field methods for vegetation sampling in this study were based upon the Point-Centered Quarter method (PCQ) by Mitchell (2015). Non-formal interviews with land-owners were also carried out to determine the state of ongoing management. Specific factors investigated were original planting mix, density, ongoing management/ maintenance, slope and aspect of sites as well as distance to remnant forest. These factors were compared to the success of each site using linear regression, pairwise comparisons and ANOVA analysis. Results showed a clear consequence with structural characteristics of basal area, height, canopy cover and seedling density increasing over time and compositional characteristics with an increase native species richness, native seedling richness and decrease in exotic species richness over time. Sites were found to be converging on remnant forests in structural characteristics however still significantly different in compositional characteristics. A nine/ten-year threshold was observed when sites underwent key structural and compositional developments, showing signs of successional changes. Enrichment planting and weed management were both found to significantly affect structural and compositional characteristics of the study sites. Overall sites were found to be on track to becoming restored forest ecosystems.