Time for Coleridge shelter to be renewed

Press, 4 March 1989, Page 22

Time for Coleridge shelter to be renewed

Country Diary

Derrick Rooney

When construction started on the Lake Coleridge power station in the early years of this century — with material brought on a long haul from Christchurch in waggon trains drawn by traction engines — the site was so exposed that on some days work had to stop because of the risk of injury from windblown objects. Even carpenters and electricians working inside had to stop occasionally because the noise of gusts, and pebbles striking the buildings, made it impossible for them to concentrate on their work.

So as construction went on, another essential job was begun on the steep slopes above and alongside the powerhouse. Thousands of seedlings of hardy conifers were-planted to shelter the powerhouse and village from nor’westers that pound down the Rakaia Valley. Nearly eight decades later, these plantations are a textbook example of the ability of blocks of trees to shelter and enhance the microclimate.

In the Lake Coleridge village gardens, flowers, trees and shrubs from many parts of the world flourish. On islands, verges, and almost any vacant ; spot alongside the village streets, > a wide range of exotic and ' indigenous trees and shrubs has ? beew-planted and thrive. Even a '■ a kauri from Northland grows

well. However, like other living things, conifer plantations and shelter belts have a life span and must be renewed from time to time. The oldest plantations at Coleridge are now ending their days. Some of the blocks are “overmature,” and their numbers are being progressively reduced by the winds they were intended to exclude. In the last 12 months, Electricorp, which now owns the power station and surrounding area, has begun a harvesting programme in which the plantations will be felled and replanted — over a period of years, so that the shelter, and the pine woodland character of the area will be maintained. The value of the shelter these plantations have provided q«er the decades is incalculable.

Their residual value, though, can be measured more readily. Over the last year, thousands of radiata and Corsican pine logs have been sold to three “local" sawmills — at Methven, Hororata, and Darfield — and the radiata trees have yielded Electricorp a net income equivalent to $304 per hectare per year over the 55-year life of the stands.

Stronger but more slender Corsican logs from a 73-year-old stand are providing a slightly lower, but still highly satisfactory, return of $264 per hectareyear.

Even a block of poorly grown Ponderosa pine, the scopulorum variety, is returning some income. A Christchurch mill has taken the logs for boxwood at a price equivalent to $5O per hec-tare-year over the 58-year life of the stand.

The log sales were negotiated by the Ministry of Forestry consulting service, which has a contract with Electricorp to manage the plantations. Very little is being wasted since poorer trees which fail to meet sawlog standards are being sold for chipwood, pulping, or firewood. Farm foresters from Central and North Canterbury, who have a special interest in the Coleridge plantings because of thenassociation with the Hart Pine-

turn there, had an opportunity last week to see the harvesting programme, assess the quality of the logs, and look at the replanting proposals. A field day was arranged by Lucy Wybourne, an M.O.F. forestry consultant, who is supervising the logging programme.

One of the first questions asked was this: Why, when the timber market generally is regarded as depressed, were the plantations being felled now? Because, said Miss Wybourne, they were beginning to deteriorate. An increasing number of trees was being windthrown, and the timber volume was decreasing as a result. The age, and competition between the trees because of their close spacing, meant that growth had effectively ceased. The M.0.F., said Miss Wybourne, had been able to negotiate a satisfactory stumpage with the local mills for sawlogs. The better logs, classed as peelers, were being sold off the skid to a West Coast factory. Miss Wybourne declined, when pressed by farm foresters, to divulge the stumpage being paid by the mills, other than in terms of income per hectare. But from other sources, I understand that the radiata fetched about $26 a tonne, which is probably a rea«nable price in present circuminces.

The 73-year-old Corsican pines, west of the powerhouse, were planted at very close spacing, about 2000 stems to the hectare, and had been untended and unthinned throughout their life. Despite this, the stand had in recent years attracted a lot of interest among foresters because of the large numbers of highquality poles it contained. According to one of the Central Canterbury farm foresters, Mr P. G. Smail, of Hororata, these could have been sold to Sweden in the 1970 s at a premium price. In the event, most of them are being sold as sawlogs in 1988 and 1989. Corsican pine is slower growing than radiata but much hardier, and yields stronger and heavier timber. It is highly rated for posts and poles. “Like many other farm foresters,” remarked Mr Smail, “I grow and sell radiata posts, but I buy Corsican for my own use.” Corsican pine is not naturally durable, but it may be treated in the same way as radiata. Mainly because of its longer rotation, it is more expensive to grow than radiata. However, when, questioned, Miss Wybourne said she had no hesitation in recommending replanting with Corsican. This time, the initial planting density will be lower (1600 stems to the hectare) and the stand will be primed and thinned.

“More management might have resulted in a better return from the first rotation,” she said. According to sawmillers, Corsican pine does not at present command a premium for sawlogs. Should it? Yes, according to Dudley Franklin, research field leader with the Forest Research Institute at Rangiora. “Stumpage is such a small component of the end cost of timber that I would expect a good margin for quality.”

Old and untended .radiata stands usually contain a mixture of good and poor trees, but a feature of Corsican stands, according to Mr Franklin, is their uniformity. In surveys made by the F.R.1., Corsican pine has consistently scored as the best species for high-country planting. Both it and Ponderosa pine will grow at a higher altitude, and on colder sites, than radiata. The Ponderosa block, also planted at very close spacings and left untended and unpruned, contained at 50 years old a large number of small stems, many with spiral grain which rendered them useless for milling. Even at its best the soft Ponderosa wood is not highly regarded for timber, pulping or chipping. However, the species should not be dismissed out of hand, said Nick Ledgard, the scientist responsible fc&.the high-country tree survey. Ponderosa grows 10

to 15 per cent faster than Corsican. Because of its softness, the timber, which can be machinestapled, is useful for boxes and pallets. Its future at Lake Coleridge seems non-existent, however, and the site it occupied will be replanted in radiata, stands of which have been yielding about 1100 cubic metres of logs per hectare. Like the Corsican, the radiata will be replanted at half the original density, then pruned and thinned to enhance the final crop. The new rotation of trees will be planted directly into the slash and litter left after logging. Conventional site preparation is not considered to be economic on this steep slope. Improved strains of radiata now available will be planted this winter, to give the young trees a head start Natural regeneration of less desirable seedlings — bound to occur on this site — will be discouraged by oversowing with grasses and legumes, and by grazing. There is a certain urgency about the commencement of this work, convincingly demonstrated by a nof’west gale the night before the field day. An area of about five hectares of mature radiata, downslope from a block that had been clearfelled, windthrown. Some of the treeswere uprooted

and some were smashed or broken. Further down the slope, Douglas fir trees were flattened by the pines falling on top of them. In places windthrown trunks are heaped three or four deep. Miss Wybourne was philosophical about the damage. “I had expected it to happen sooner or later,” she said. “Windthrow is always on the cards when you start opening up an old stand. It is one of the hazards of logging in this area.”

Dramatic though the windthrow appears, the actual loss may be modest — perhaps 10 to 15 per cent of the logs, perhaps less. Tony Brand, of Brand Logging, a contractor felling and extracting the trees, is confident that his crew will recover most of the fallen stems. “I don’t believe the gale will cause much loss at all,” he said. “It will just make our job much harder.” The problem may not occur in the next rotation because the new generation of Coleridge trees will be wider spaced and better managed. They should be less vulnerable to windthrow, even in one of those Rakaia gales than can pick up pebbles and smash them through windows. NEXT WEEK: The Hart arboretum — whart is its future? ?