What silviculture regime should I choose?
The silviculture or management regime you use to manage your forest will depend on the market you target and your site characteristics.
Before you plant your site
Before you plant you should think about the following to help you choose a regime:
- What are the costs of each regime?
- How much wood will you get out of it?
- What mix of log grades can you expect to get from each regime?
- What are the missed opportunities of choosing a particular regime? For example, if you do not prune or thin, you might miss out on additional revenue like selling the thinned trees for biomass.
- What’s your assessment of the market in 30 years’ time?
- What market are you targeting?
- What’s your site like?
- What species are you planting?
Types of regimes
There are 4 main silviculture regimes – unpruned with no thinning, pruned with no thinning, pruned and thinned, and unpruned and thinned.
Unpruned with no thinning
Also known as plant and leave or millennium regime, this produces industrial grades that are currently:
- mulched into pulp and paper
- exported for industrial uses like boxing timber for the construction industry.
There is a large demand from China for this type of timber.
Pruned with no thinning
This regime is used for growing narrow appearance grade logs for the domestic market.
Pruned and thinned
This regime produces structural and appearance grade timber. It is mainly used for the domestic market with a small demand from Japan.
Unpruned and thinned
This regime produces structural grade timber. There is demand from China, Korea, Japan and the domestic market.
Pruning is removing a tree’s lower limbs to produce higher value wood free from knots. Pruning commonly involves thinning to a lower stocking rate than other regimes to encourage greater diameter logs.
Pruning is the most expensive management regime. Before deciding to prune, look at:
- Your location. What’s the availability of labour in your area? What logs will your local mills take? What end market are you targeting?
- Your site’s terrain. The steeper the site, the harder and more expensive it is to prune and thin.
- Your soil’s fertility. This will affect the growth and stiffness of your trees. If your soil is fertile, then it can support more trees. If the soil is low quality, then you will need to do some thinning.
Forest management trends
The Forest Owners Association publishes a brochure each year, jointly released by the Ministry for Primary Industries. This brochure:
- contains background information and statistical data on our forest industry
- includes a breakdown of the forest management trends.
There are 3 broad grades of timber – industrial, structural and appearance.
Industrial grade timber
Industrial grade timber usually comes from the top one-third of logs or from logs that have not been pruned or thinned. Appearance and strength do not matter so this section of the tree is not pruned. This timber is used for things like construction boxing and pallets.
Structural grade timber
Structural grade timber usually come from the middle-third and lower-third parts of the log. This is the timber grade used in construction for things like framing and roof truses.
Appearance grade timber
Appearance grade timber usually comes from the bottom one-third of a log, which commonly has been pruned. Because of their clean, knot free appearance, they are used for things like furniture and weatherboards.
The National Exotic Forest Description published by the Ministry for Primary Industries has regional lookup tables for Radiata pine and Douglas fir. These can tell you what logs you can expect to have, under what regime, after how many years.
Radiata pine stocking rates
Radiata pine is normally planted at about 1,000 to 1,250 stems per hectare. If you choose to prune or thin your trees, then your final stocking rates change to:
- 200 to 400 stems per hectare for pruned regimes
- 400 to 500 stems per hectare for structural regimes.
Depending on where you are there may be opportunity to sell thinned trees and prunings to biomass energy consumers.