PUBLISHED: JULY 2011

Evaluating Restoration Success in Urban Forest Plantings in Hamilton, New Zealand

by D. Bruce MacKay1, Priscilla M. Wehi1,2, and Bruce D. Clarkson1

1 Department of Biological Sciences, University of Waikato, Private Bag 3105, Hamilton 3240, New Zealand

2 Address correspondence to B.D. Clarkson, email b.clarkson@waikato.ac.nz

Abstract

To evaluate the success of restoration efforts in young urban plantings, we assessed 66 experimental plots in gully systems in Hamilton City, New Zealand, and adjacent areas. We compared vegetation change in restored patches planted with native species to vegetation in naturally regenerating patches and mature native forest. A range of variables was used to assess ecosystem functional, structural, and compositional attributes. Different planting and maintenance regimes and environmental factors likely to affect the success of plantings were also evaluated. Vegetation change towards the mature forest reference state was found to be rapid in twenty plots. However, twelve plots showed limited progress towards this state, with low numbers of lianas and epiphytes and low native species recruitment, regeneration, and species diversity.

Management treatments found to be beneficial for a plot's ecological condition included good-quality maintenance and a low level of human disturbance. Diverse planting and enrichment planting (addition of species after initial planting) were more beneficial if they were linked to good maintenance. Proximity of seed sources was important for good ecological condition. The research supports the concept of multiple restoration pathways but not the idea of a closely defined assembly order (deterministic sequence) for the vegetation community. The findings suggest that restoration in isolated urban patches requires species enrichment within, or peripheral plantings near, patches. The regeneration and dispersal functions appear to be more important for successful restoration than composition on site. Human disturbance should be actively managed to maximize restoration success.

Keywords: enrichment planting, restoration, regeneration, succession, urban, vegetation composition, management