Burnham activity quite innocent

Press, 5 September 1987, Page 22

Burnham activity quite innocent

Country Diary

Derrick Rooney

Strange things are happening rdown in the forest at Burnham, Must round the comer from the camp: blocks of scaffolding among the trees, reports £bf people entering the area oddly shaped equipSpment.

£._■ But it’s all quite innocent; it Z isn’t a dry run for a Fiji-style f£oup but part of an international project that in due might help tree-growers '’'in New Zealand and in developfng countries get the best possible returns from available land, ---with minimum ecological damSage-

| Productivity § predicting

»»■. The project, which is running in several counCtries, has the somwhat cumbersome title, “The Nutritional of Harvesting on Bsite Productivity.’’ Or for short, ’‘Project CPC JO." The atoas are _ to develop ways of predicting the ecological consequences and effects on long-term different intensities of tree harvesting, and to develop prescriptions which will enable forest managers to maintain or improve productivity witii every forest potation. f

This may not sound very exciting, and the proceeding of the project workshops held to date make very dry reading. But it is quite an important topic because any decline in the productivity of forest land can have widespread economic and social consequences.

Some types of forest — moist tropical for example — function on a very limited 'energy budget,” with a relatively high percentage of the available nutrients locked up in the living bionfass.

Harvesting such forests can have profound consequences. Project CPC 10 will not address this question directly but the information it is assembling will be of considerable significance. Information gleaned by scientists scrambling on scaffolding in a pine plantation at Bumham may therefore be of use to foresters at some future date in many countries. The Burnham plantation belongs to the Selwyn Plantation Board, which also helped last summer by providing labour for scrub-clearance work which was part of the study. The research is being done by staff of the Ministry of Forestry from the Forestry Research Centre at Ham. Research in the 25-hectare block actually predates the international project by a good few years, and has already produced information about site preparation and management that is very useful for forest planners and managers in this country. An earlier generation of trees on the site was severely windthrown in the 1975 windstorm and their replacements — managed in several different ways and planted

after several different site treatments — have been monitored throughout their life, now some nine years. Project CPC 10 was set up three years ago. The scaffolding is there because the research is effectively in two parts — one looking at the quantifiable productive consequences of various planting and weeding regimes and the other looking at internal growth mechanisms of tree and their interrelationship with understorey weeds. What is going on inside the tree? How does it distribute available nutrients in its stems, twigs, and foliage? Is competition for moisture more important than competition for nutrients? Does moisture stress in summer affect height and diameter growth equally? Do trees respond to drought and competition by changing their nutrient balance?

The only way to find the answers to such questions is for the scientists to put themselves, and their equipment, right up in the canopy of the trees — hence the scaffolding. A portable gasexchange unit and other equip- , ment are supplementing old-

fashioned observation and measurement of tagged stems. The research is planned to extend over a number of years, possibly the life, of the plantation. The more extensive international programme of which the research is a part is sponsored by the O.E.C.D.’s Intematioinal Energy Agency, and is being managed from New Zealand by the Ministry of Forestry. Other participating countries are Canada, Norway, Sweden, and the United States. A seminar to review progress to date is scheduled to be held in the •United States next month.

And now for something completely different — but still about trees. In New Zealand we like to boast that our forests are among the fastest growing in the world, even though we aren’t in quite the same class as, say, the Solomons, where hardwood sawlogs can be grown in 10 years, or Brazil, where eucalypts are harvested on a five to eight-year rotation.

But compared with parts of Europe and North America our growth rates are phenomenal — Corsican pines, for example, here on a 40 to 60-year

rotation, compared with up to 110 years in Europe. Radiata pine, without fertilizer or irrigation, grows to millable size in 20 to 25 years in most parts of New Zealand, a very good growth rate indeed. But what is our fastestgrowing tree?

No sign of slowing down

I’m interested in the answer to this, possibly through curiousity or a typically human obsession with the fastest, the biggest, and the best, but also because it gives me an .opportunity to boast I have on my own property a tree which has grown faster than any other I have seen in Canterbury. A manna gum, it was planted (by me) in January, 1975, so it is now 12-plus years old. The August windstorm in that year severely damaged it but it recovered, its growth spurted away. It is now about 22 metres tall, with a massive trunk, and show no sign of slowing down. Last I measured

its diameter at breast height — 60 centimetres. Back in January it was a mere stripling of 53cm. I offer no logical explanation for this remarkable growth. The tree has had no fertilising or extra irrigation and was planted among established trees and hedges, some of which are more than 40 years old. It now overshadows them.

As I travel round I keep my eyes peeled for interesting trees, and I have seen nothing in Canterbury to compare with this growth rate. The closest to it, perhaps are a group of eucalypts on a North Canterbury property, alongside the Hurunui River. These were measured late in 1983 by Mr Theo Russell, then a senior extension officer with the Forest Service. Subsequently he reported on the trees in the “New Zealand Tree Grower." The outstanding examples were Eucalyptus -delegatensis, age 23, height 28 metres, d.b.h. 83CM; Eucalyptus regnans, age 23, height 31 metres, d.b.h. 56.5 cm; Eucalyptus regnans, age 10, height 23.5 metres, d.b.h. 46cm. I have not seen these trees, but the last mentioned is clearly an outstanding specimen and it

would be most interesting to measure it again in 1993 to see it this rate of growth is maintained. It is, year for year, taller than my manna gum but has less volume. If there’s a better men of known age let’s hear about it

Flowering cherry plums

Still on trees: I had occasion to go to Ashburton on one wet day last week and the bright spot on an otherwise grey trip was the sight of hundreds of cherry-plum trees flowering along the bank of the Ashburton River, and on the Rakaia River terraces at Mead. The cherry plums along the creekbanks in our village have been flowering well, too. This must be one of the prettiest as well as one of the most naturalised trees, providing as it does a display of blossom in spring, fruit for wildlife (and human) fodder in summer, and bright leaf colour in autumn — surely a classic case of a naturalised plant which is a useful and attractive addition to our wild flora. The Irony is that it probably didn’t come into the country as a fruiting tree but as either a hedge or a rootstock on which other plum were grown.