Skip to main content

Impact of weed invasion on Kahikatea forest fragments in the Waikato region and review of the ‘Green Wheel’ recovery ranking tool

TR 2019/02

Report: TR 2019/02

Author: Mark C Smale

About this report

The Waikato Regional Council aims to create a “Kahikatea Forest Green Wheel” to help landowners and resource managers measure how similar a given kahikatea forest fragment is to the most healthy and functioning example we could expect in the contemporary ecological and economic setting. A monitoring plan for forest fragmentation is part of the Council’s 2018-2028 Long Term Plan.

The Green Wheel, adapted from the Ecosystem Recovery Wheel developed by the Society for Ecological Restoration Australasia, comprises a suite of abiotic and biotic attributes that reflect changes in ecosystem condition along a continuum from degraded to intact (or vice versa). Each is accorded a score from a five-star rating system, and visually presented on a wheel graphic, to enable landowners or site managers to quickly identify areas that need improvement, and track restoration progress towards a higher or lower functioning state over time.

A list of ecosystem attributes and relevant sub-attributes has been proposed for assessing the health and functioning of kahikatea forest fragments in the Waikato Region. These are grouped under the Pressure, State, Response framework used by the council for monitoring and reporting on the state of the environment.

The attributes and associated scoring system for a Kahikatea Forest Fragment Green Wheel are presented, along with proposed field datasheets and a completed example for a real-life kahikatea fragment. Recommendations include suggested methods for collecting information to apply each standard, and whether best applied by the landowner/site manager, a specialist contractor, or via GIS analysis.

Although iwi interest in the results of this work could be high (given their involvement in kahikatea forest conservation and restoration) it is not considered that the way this work was completed or the methods used would be of particular interest. For this reason, we consider this work to be low risk but we do intend to make the report freely available to iwi within the Waikato. Please note that, there is a need to publish the report and make the information available to the whole community so that they can make their land use/management decisions based on all available information for the weeds control at the Kahikatea fragmentation.

An example of the potential interest is the Maniapoto Trust at the Otorohanga district has some restoration activities for the kahikatea forest fragmentation.

Read or download the report

Impact of weed invasion on Kahikatea forest fragments in the Waikato region and review of the ‘Green Wheel’ recovery ranking tool [PDF, 3.2 MB]

  Executive summary
1 Introduction
2 Objectives
3 Study sites
4 Methods
4.1 Green wheel review
4.2 Fieldwork
4.3 Data analysis
5 Results
5.1 Green wheel review
5.2 Ecological integrity by the plot method
5.2.1 Species occupancy by characteristic alluvial kahikatea forest species
5.2.2 RPMS weed frequency
5.2.3 Proportion of trees, saplings and seedlings comprised by indigenous species
5.2.4 Ecological integrity by the Plot method
5.3 Ecological integrity by the Green Wheel method
5.4 Change in total alien species, RPMS weed and threatening weed species richness
5.5 Change in indigenous vascular floristic richness
5.6 Change in basal area (≈biomass)
6 Discussion
6.1 Comparison of ecological integrity assessed by the Green Wheel and plot-based methods
6.2 Differences in lower-tier composition between recently fenced and long-fenced sites
6.3 Most widespread weed species
6.4 Minimum size for full complement of representative kahikatea species
6.5 Change in basal area
7 Conclusions
8 Recommendations
Appendix 1: Characteristic alluvial kahikatea forest species
Appendix 2: Photographs of kahikatea forest fragments
Appendix 3: Green Wheel Scores