A big part of the blackwood cooperative (if we get funding) will be sharing experiences in growing blackwood. Only by sharing can we gain greater understanding and confidence. Here is a great 11-year-old blackwood plantation in north-west Tasmania. I’m writing this blog from just the photo and the owner’s emails. I’m looking forward to visiting the plantation in 2012.
Site selection and establishment
Red basalt soil in a relatively high rainfall area at an altitude of 300m provides pretty good conditions for growing commercial blackwood. I’m not sure what protection from browsing was used but it was obviously successful. Like much of north-west Tasmania the site is an exposed windy ridge. This exposure has been overcome by planting a windbreak on the western side and appears to have been effective so far, although the blackwoods are now getting above the windbreak.
The trees are obviously being pruned. But the plantation is definitely due for a thinning. At final stocking this plantation will have somewhere between 18 and 24 trees, so clearly a lot of the existing trees will have to go. Once the green crowns close (meet) then the lower part of the crown starts to die due to lack of light. This means the trees are seriously competing with each other and growth is slowing. It is better to stay ahead of this by thinning the stand to ensure there is no crown die-off and that growth remains at its maximum potential.
The intensive management of blackwood plantations means that competition between trees is not needed to control branching and improve stem form. Instead branches and stem form are managed by pruning. So the focus for commercial blackwood is to prune and keep the trees growing as fast as possible. So a lot of pruning effort here has gone onto trees that will become firewood. Some early expert advice may have helped optimise the management.
A site visit will tell how effective the management has been in creating trees that will continue to grow into valuable sawlogs. Nevertheless it is one of the best examples of blackwood plantation I’ve seen in Tasmania. This is a great example of using shelterbelts in what would otherwise we quite an exposed windy site. There is a lot of exposed ridge-top country in north-west Tasmania that could grow commercial blackwood provided shelter was available. Here is one example of how it can be done.
Thinning the plantation down to final stocking of ~200 trees per hectare will allow the crowns of remaining trees to fill out and maximise the growth potential of the site. The trees are now rather tall and thin so thinning may need to be done in two stages over 2-3 years to minimise the risk of windthrow.
Once I’ve visited the site I’ll provide an update. Thanks to the plantation owner for allowing me to share this story.