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Ashes to ashes: long term E. regnans study comes full circle

bark punch

Figure 1. The bark punch after a hard day on the job

Pilodyn

Figure 2. Pilodyn … no longer welcome in airliner cabins

Pilodyn depth scale

Figure 3. Pilodyn depth scale – hard enough to see here, let alone in the dim dark recesses of a closed forest at twilight.

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Des Stackpole
School of Plant Science
University of Tasmania

and

Rod Griffin
Griffin Tree Improvement  Pty. Ltd.

First we have Des Stackpole's side of the story ...

Here we are at the famous EP27 trial of inbred, outcrossed and open pollinated Mountain Ash at Mount Worth in the cold, wet an­d muddy South Gippsland hills.  The trial was planted as part of APM’s forest revegetation of abandoned farms in the “Heartbreak Hills” of the Strzelecki ranges in the same year that Collingwood lost the grand final re-match with North Melbourne. Now the landowner wants to bring in the harvest so it’s time for some final measurements...


I approach my first visit to the 30 year old trial with some trepidation, anticipating the usual archaeology: sifting litter for rusted wire or crumpled aluminium, or reconstructing the trial from wonky spacing that leads to disorientation and uncertainty. But lo! And behold! The trial rears out of the mist, and with great relief we note its straight lines, regular spacing, and plot corners marked with stout, labelled treated pine posts. Terrific!


Part one of the job was to develop a rapid method for describing the abundance of floral initials, buds and successive seed crops on the crown. This had to be suited to rapid assessment to be done during the commercial harvest planned for November. The scenario involves assessors darting to the crown after each tree is dropped (in an OH&S compliant manner) to assess the flowers and fruits, then getting back out of the way while an increasingly grumpy machine operator processes the tree and drops the next.  Method development was hampered by the cold, wet southerly wind that arrived on schedule (as threatened by the Weather Bureau).  The thrashing trees scuttled the plan to climb and lop target trees, so in the end we felled sub-dominants, scored the numbers of buds etc., and arrived at an ocular logarithmic method as the most appropriate.  

Part two invoked measurement of wood density and bark thickness on all live trees.  Our three-man crew proved the appropriate complement, with a man deployed to one of (i) removing a window of bark from each live tree using a rectangular punch, (ii) whacking a steel pin into each tree using a set force, and shouting this intelligence to (iii) the third man busy with the book and pencil. With respect to task (i), the punch is driven by a two pound hammer and six blows are usually enough to cleanly remove a weetbix-sized bark portion. Unfortunately the mild steel did not survive such punishment for 450 trees (Fig 1). With respect to task (ii), the pilodyn’s  (Fig 2) famous spring is reputed to discharge with the same force over a million cycles.  Readers may not be surprised to learn that the pilodyn is no longer permitted as airline carry-on luggage.  

In June the daily ration of useable daylight under a Eucalyptus regnans canopy deep in a Gippsland gully is barely sufficient for our team to measure the pilodyn penetration of the 450 relevant trees, and by 1600 hours the operator (yours truly) was reaching for the bifocals (Fig 3), and we only just finished with light to spare. Results, of course, will be analysed in the fullness of time ...

The 30 year old trees are impressive and include many of 70 cm diameter. These are developing basal buttresses and approach 50 metres in height.  Festooned with rough tree ferns, the trial resembles a stout natural regrowth stand, rendering understandable the error of preservationists who once sought to reclassify these plantations as national parks.

And a comment from Rod ...

Des’s struggle against the elemental powers of the Gippsland winter has nicely set us up for the final phase of the EP27 saga. His ocular logarithmic method may be a real breakthough (I am still awaiting a debrief) - sounds vaguely mystical, but then a lot of stats are aren’t they?


As I described in a Biobuzz note last year, we will shortly be collecting OP seed from around 20 dominant trees to obtain a "population t estimate". This will complete our description of the expressed breeding system of
E. regnans at all stages from the parental natural stands through to the first flowerings of their self-thinned OP progeny. There are not too many comparable data sets in the literature!


The bark and pilodyn data sets are added value. Because of the genetic structure of the families in the trial we will be able to make heritability estimates for these traits. Nobody is breeding mountain ash these days but it can’t hurt to know that a bit more about the genetics of an important eucalypt.  This project also gives Des a bit more chance to polish his writing skills.

Biobuzz issue 9, August 2009