Workshop Report: Poplar and willow planting for Land Overlay 3A, Gisborne, East Coast region

Desktop exercise approach

The aim of the desktop exercise was to establish consensus among workshop participants on the following key areas:

  1. Could effective erosion control be expected if planting regimes were restricted to Land Overlay 3A or would additional land surrounding the 3A delineation require to be treated;
  2. Differentiating between erosion features requiring land use change to reforestation (blanket planting in pines, closely spaced poles/wands, reversion) versus those erosion features that could be retained in a pastoral regime by using pole/wand planting regimes to control erosion;
  3. Having decided that space planted poles/wands were the most appropriate treatment, what were the best planting densities for specific erosion features.

Sixteen workshop participants were provided with aerial and oblique photographs and a 3D digital image of various sites that included 11 gullies, 10 earthflows and 6 slip/slump complexes. Other relevant information provided were mean annual rainfall, elevation, climate zone, geology, LUC unit and an outline and size (hectares) of the Land Overlay 3A area surrounding each erosion feature.

Site by site, each participant was required to select one of 20 pre-set treatment options as being the most appropriate primary treatment required to deliver an effective erosion control outcome. In selecting a planting treatment option, participants were asked to take into account whether or not they considered additional land area outside of the depicted 3A polygon would also require treatment, and if so indicate whether it would be greater or less than 50 percent of the watershed.

In discussions before the start of this exercise it was clear that some participants were uneasy at being restricted to choosing a single treatment option per erosion feature. It was decided by consensus that if no single treatment alone was felt to be sufficient to stabilise the feature in question, participants could chose a combination of treatments provided they denoted which option would be the primary treatment. The selection of a high, medium and low pole planting density of 200–500 spha, 75–200 spha and under 75 spha, respectively, was in the belief that the range was adequate and where implemented would provide effective erosion control to any erosion feature within the delineated 3A Overlay classed as the worst eroding land in the Gisborne District.

The treatment options included:

Plantation forestry @ 1250 spha

  1. All Land Overlay 3A plus treatment of over 50 percent of watershed.
  2. All Land Overlay 3A plus treatment of under 50 percent of watershed.
  3. All 3A area only.
  4. Part of 3A area only.

Spaced pole planting @ 200–500 spha

  1. All Land Overlay 3A plus treatment of over 50 percent of watershed.
  2. All Land Overlay 3A plus treatment of under 50 percent of watershed.
  3. All 3A area only.
  4. Part of 3A area only.

Spaced pole planting @ 75–200 spha

  1. All Land Overlay 3A plus treatment of over 50 percent of watershed.
  2. All Land Overlay 3A plus treatment of under 50 percent of watershed.
  3. All 3A area only.
  4. Part of 3A area only.

Spaced pole planting @ under 75 spha

  1. All Land Overlay 3A plus treatment of over 50 percent of watershed.
  2. All Land Overlay 3A plus treatment of under 50 percent of watershed.
  3. All 3A area only.
  4. Part of 3A area only.

Paired planting along watercourse

  1. Within 3A area only.
  2. Within and outside 3A.
  3. Retirement (indigenous reversion).
  4. No treatment.

Each participant made his/her decision independently and without discussion with other participants. Handwritten responses were entered and analysed in Microsoft Excel.

Contact for Enquiries

East Coast Forestry Project
Ministry of Agriculture and Forestry
Cnr Grey St & Childers Rd
1st Floor ZGFM Building
PO Box 2122
Gisborne 4040

Tel: +64 6 986 8691
Fax: +64 6 986 8697

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