Forestneeds

April 23, 2006

Alton Field Day Lessons

Filed under: Forestneeds_Notices,Timber Growing — shem kerr @ 4:44 am

23 year old SequoiaThe 20/04/06 Taranaki Farm Shelter and Forestry Association field day examined riparian plantings; pasture retirement; and progress on cypresses.

The farming locality of Alton on New Zealand's North Island, sits on a slightly cut gently sloping wave cut platform or marine terrace overlooking the South Taranaki Bight,the Tasman Sea, and for the Flat Earth Society right across the Southern Ocean to the South Pole. Average wind run speeds are a lot higher than where most sensible people actually choose to live. Occasional chill southerly gales pick up ocean salt spray and sweep it 40 km overland to burn the foliage off hedges as far as Inglewood. Within 50 years of arriving into a pimeval forested remnant of Gondwanaland, the Pakeha settlers had recreated a copy, albeit a windier version, of their denuded hawaiki. In the 1950s the Taranaki Farm shelter and Forestry Association was founded to help farmers understand how to establish shelter and woodlots on their properties; and to develop a positive attitude toward trees. Here's how this has been followed on Harvey Gibbs' farm.

Planted Kauri, Agathis australis, amongst bregenerating scrub in paddock fenced off from livestock This paddock has had livestock fenced out; here planted Kauri ( Agathis australis ) grow in regenerating scrub.

Alton Cubs/Scouts July 1991 riparian plantingThis stream side (riparian ) planting was done by Alton Cubs/Scouts July 1991.

Excavator-pruned C macrocarpa in sheltered gully Sheltered gully with excavator pruned Monterey cypress.

Harvey is presently trialing pasture nutrient management; comparing conventional chemical fertilizers against liquid applications that encourage soil and pasture micro-organisms, plus crushed limestone to adjust the soils base saturation ratio. The Gibbs family has also been growing cypresses.

Back in the early 1980s, New Zealand forestry scientists decided to improve the genetics of Cupressus macrocarpa. Seed was collected from 88 top quality C macrocarpa trees from throughout the country. ( Well that's their story. However they left out the most canker prone areas; and those most exposed to salt wind. ) The selection crieria was; freedom from canker; vigour; stem straightness; and freedom from fluting. At that time it was acknowledged that C macrocarpa is site specific, that it "grows well on fertile lowland sites", and that "pushed beyond those, growth and form rapidly deteriorate", and futhermore that "gains from tree improvement are likely to be fully realised only on the best sites". However,having said that, the first set of progeny trials was then planted on typically harder forestry land. In the early 1990s, it was next decided to follow up with trials on fertile farm sites. One was on Tony Gibbs' farm ( now Harveys ), using 37 of the individual "plus tree" seedlots. Tree spacing was to be at 3m x 5m . Four repititions of a ten tree row plot were planted for each seedlot. Row plots were considered to have merit by simplifying the design and giving a visual impression of differences between seedlots while retaining statistical validity. The ends of each plot were identified with numbered durable hardwood stakes. The trees were kept free of weed competition; and were on their way in the name of science.

Then the goats got in.

I would've first seen the trial about 1995. The survivors, and it was most of the trees, had pretty much recovered from goat attack; most of the plot marker stakes were still in place; and the trial looked quite promising with an absence of canker. Tree form was slightly dumpy, ie with a lack of pronounced apical dominance. Between then and now a fairly modest attempt has been made to clear prune the lower trunks while maitaining the trees' prcarious health; some thinning of trees most badly affected by canker has been done; and somehow a lot of the marker stakes have taken leave of absence. In an ideal set up all of this needn't've mattered. However, the combination of thinning; lack of markers and the fact that the rows of trees weren't actually planted 3m apart, nor in straight lines, butCupressus macrocarpa progeny trial sometimes woggly closer to 2m apart thus making it hard to navigate through the site and identify seedlots. Apical dominance is still not that great, branch diametre is larger, branch angle is steeper, presence of canker is greater, and growth rate is less, than should be the case for normal healthy progeny from 37 of the “top” 88 C macrocarpa trees in New Zealand. These trees aren't happy. They have hit the wall

15 year old C macrocarpa in light wellHow big should a C macrocarpa tree 15 years old be? Well, we might consider this 58cm dbh 15 year old specimen planted by Mike Cole on his father's farm at Kakaramea just a few kilometres along the road. (Photo at left )

And what should the crowns look like? Well probably not a lot wider and just as healthy and of similar height to those on Jim Phillips' 10 year old trees at Mimi.

Field day discussion indicated that genetics was the most important factor in success. The trees disagreed. If genetics was the biggest deal. Then the trial layout of 10 tree row plots should've made that quite obvious. However, nowhere were there more than 2 superior trees together in the space of 10 trees along the line. The discussion might've considered the acknowledgement(above ) that C macrocarpa is site specific; , or even to some degree micro-site specific; and that this was the major contributor to individual tree success. Let's take another example: that of the Rangitoto #3 tree, superior growth, and good form, free of canker every year of its 40 years. Yes, the family it came from has stood out in trials; and its own progeny have stood up with the best. Therefore genetics is an important factor. However, when the Rangitoto #3 stand was felled, seedlings from this one best tree in the stand were an across-the-site component of the replanting. At the time of the farm forestry special interest groups field day in October 2005, 14 months after planting. there was one row of 3 Rangitoto #3 trees 2m tall, whereas across the rest of the site the best of Rangitoto #3 progeny were at most 1m tall. The difference was that these 3 trees were planted adjacent to the exact same spot as their mother. So, it doesn't matter how good the genetics are, when pushed beyond the best sites, the growth and form of C macrocarpa rapidly deteriorates. Then, how do we know what is a good site? We cant know by guessing. We can only know beforehand by soil analysis; and while the crop is growing by foliar analysis. How do we make what we think is a good site closer to a near certainty? Planting into an existing governess crop can encourage the trees to grow taller rather than wider, ie, to put more energy into apical growth.

Cupressus macrocarpa, gorse and poplar This gorse covered slope at Kakaramea now has 5 year old C macrocarpa and poplars.
Although generally C lusitanica and its hybrids establish faster than on this slope on the Gibbs' farm at nearby Alton are of of the same age, have beenC lusitanica on southern slopeC macrocarpa, those fertilized, but are slightly less tall with bigger branches that will leave larger wounds when pruned.

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