Notes on West coast (NZ) blackwoods

IanBrown

New Zealand blackwood grower and co-author of the blackwood growers handbook Ian Brown has posted a useful and detailed update on his view of current blackwood management. It makes for thoughtful reading for current and prospective blackwood growers.

Here’s the handbook:

http://www.nzffa.org.nz/farm-forestry-model/species/blackwood/#Blackwood handbook

Here’s the update:

http://www.nzffa.org.nz/nzffa-member-blogs/ian-browns-blog/notes-on-west-coast-blackwoods/

I have two comments on Ian’s notes:

Firstly on the issue of blackwood growth rate and wood quality.

Certainly current research shows that growth rate has little to no impact on blackwood wood quality in terms of heartwood colour and basic density.

But my PhD research showed that blackwood wood quality can vary enormously from tree to tree. This is supported by numerous other studies, and is shown to be mostly genetically based.

So if you want good quality wood from plantation blackwood you need to plant good quality genetic stock.

Unfortunately we don’t yet have a blackwood selection and breeding program.

Fortunately the incidence of poor wood quality genes is relatively low.

Also note that research shows there is no correlation between heartwood colour and wood basic density.

Secondly on the issue of pruning height.

Pruning height will obviously affect the final value of the crop and in a big way since most of the value is in the clear pruned log.

Where the site dictates that you can only prune to 4 metres so be it.

But a fully stocked blackwood plantation of 200 trees with an average tree diameter of 60cm dbh pruned to 6 metres will have approximately 300 cubic metres of clear grade premium blackwood per hectare. Only prune to 4 metres and the volume of clear grade blackwood comes down to 215 cubic metres per hectare a reduction of 28%!!

Whilst you have the trees growing you may as well get the most value out of them that you can.

Thanks to Ian Brown for posting his comments.

Advertisements

7 responses to “Notes on West coast (NZ) blackwoods

  1. So a few items from Ian Brown’s blog post:

    – Form pruning at 6 to 7 years old too late to limit malformation? Why would this be the case?

    Double/multiple leaders can begin in the first year. Waiting until age 6 is far too late. Annual pruning is recommended.

    – ‘Twould be interesting to have some indication of site quality with respect to soil fertility at the NZ sites mentioned. Sounds like a lot of them are crappy soil. I wonder how these would compare to sites in the Otways or Strzeleckis on volcanic/ferrosol or good quality dermosol. These Victorian sites would also have satisfactory temperature and rainfall profiles. Ian mentions his NZ site on volcanic soil that has reached 57cm MTD at 31 years.

    – 3m – 4m as a reasonable target log length at some sites.

    See my comment in the article above re lost value.

    – Wider logs are better. But will they attract a premium in Vic/Tasmania?

    Good question. Ian quotes Don Britton. But Brittons are not buying and milling plantation grown blackwood in a competitive market. They operate in a highly subsidized and protected market. And its not just the order of the price difference but also the magnitude of the price difference.

    – So if blackwood crowns have touched and retreated as Ian puts it, they won’t spread again after thinning?

    They may spread out again but the damage to the crown structure has already been done and can’t be undone.

    Cheers.

  2. – Form pruning at 6 to 7 years old too late to limit malformation? Why would this be the case?

    Gordon Double/multiple leaders can begin in the first year. Waiting until age 6 is far too late. Annual pruning is recommended.

    So if you leave leaders until the tree is 6-7 years old and then prune what is the outcome? Does the tree concentrate growth in the remaining leader? If this is the case you will still end up with a sawlog but with a larger occlusion where the leader was removed than would have been the case if the leader had been removed earlier. And the sawlog above the leader would achieve a millable diameter slower than would have been the case if excess leaders had been removed earlier. If this is what happens with late form pruning its suboptimal but will still deliver a sawlog albeit slower. Or does something else happen?

    – So if blackwood crowns have touched and retreated as Ian puts it, they won’t spread again after thinning?

    Gordon They may spread out again but the damage to the crown structure has already been done and can’t be undone.

    The tree just wants a crown to photosynthesise. Which generally speaking I would have thought is better served by a bushier crown if there is no competitive shading. What’s the damage done to the crown structure that can’t be undone after crowns have touched and the crown has retracted?

    Thanks

    David

    • Hi David,

      Leader pruning:

      “If this is what happens with late form pruning its suboptimal but will still deliver a sawlog albeit slower. Or does something else happen?”

      Suboptimal is right! Do you want to produce the very best clear grade blackwood sawlog?

      If you wait until age 6 you will have a very large branch/pruning scars that will take years to heal and may allow rot into the stem in that time, and hence compromise the whole tree! Pruning small branches annually is much easier and achieves a better outcome.

      Crown structure:

      My take on blackwood crown structure is that it is best to give the blackwoods ample space to allow the crowns to develop – spread out. Big broad crowns as Ian Nicholas would say. If you delay thinning (a very common problem) the crowns become narrow with lots of acute branch angles which are then susceptible to fork breakage. I suspect fork angle is partly genetic but strong crown competition doesn’t help.

      Also retreating crowns due to competition is blatant loss of photosynthetic capacity and loss of productivity. Avoid at all costs!!

      Cheers

      Gordon

  3. Gordon, I have a few comments I wish to share regarding Ian’s NZFFA blackwood blog.
    David has miss-read what Ian is saying regarding form pruning. As you pointed out, it begins at age 1 and is generally completed by age 6-7, with clearwood pruning and thinning to final stocking completed by age 10. From this point, what are realistic growth rates? I have referred you to the 2007 growth model on previous occasions. As Ian has pointed out, to get a blackwood stand at 200 sph attaining an average diameter of 60cm is only possible at the very best sites. Sites in NZ where such growth is possible is on very fertile soils, with high rainfall and warm temperatures. Having visited many of the sites in NZ that Ian refers to I can assure you even the best sites here in Tas or Vic are not going to achieve these sort of growth rates. So what is a realistic volume that a grower might expect on good sites here in south Oz?
    The 2007 growth model indicates an average site attaining a MTD (mean top diameter) of 49cm by age 35 at 200sph, rising to 52cm for an above average site. Keep in mind MTD is the average diameter of the largest 50sph, not the average diameter at breast height. If you want to achieve 60cm then stocking needs to be reduced to 100sph.
    Let’s consider individual log volumes for 5.5m logs (with pruning to ~6m).
    60cm dbh log has ~1.3 cube, 55cm ~1.1 and 50cm ~0.9.
    I’ve been critical of your volume estimates previously for the reason that they are not realistic. Malcolm McKenzie (an experienced grower from NZ) has also suggested that 150 cube / ha is more realistic than the 300 cube figure from the Growers Manual (this figure was based on an earlier growth model and the expectation that some unpruned sawlog material is included in the volume). I will repeat this again in the hope that others such as David may have a more realistic expectation of what to expect. On a reasonable quality site expect ~150 cube of pruned butt log per ha at 200 sph by age 40. On the best sites we have, 200 cube / ha may be possible.
    Malcolm McKenzie and Paul Millen are examples of what growers should be doing, value-adding of logs on farm and selling sawn timber, not logs!

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s