THE REGENERATION OF A FOREST

Press, Volume CV, Issue 31042, 23 April 1966, Page 5

THE REGENERATION OF A FOREST

Ten Years’ Hard Work At Balmoral

[Specially written for “The Press" by RODGER KINGSBUR I ] TEN years have passed since the most disastrous exotic forest fire ever to occur in a New Zealand State forest destroyed 6000 acres of the 24,000-acre Balmoral forest. But from the blackened waste has sprung a new forest of strong, healthy trees.

Trees which cost £222,000 to grow were damaged or destroyed in the uncontrolled blaze which raced through the forest on the week-end of November 26-27, 1955. In the face of a full north-west gale, and hampered by lack of heavy equipment, fire-fighters had little chance of stopping the fire, which ran three miles through a 5000-acre block of 30 to 35-year-old pine in three hours.

Unchecked, the fire leapt 180 ft across the Christchurch-Hanmer Spring’s main highway and a double fire break on each side of the road, and set fire to another block containing more than 2200 acres of timber. Wind direction during the fire changed frequently. Had it remained steady it is probable that more of the forest would have been saved through the use of firelines to prevent spread on the flanks. It was the wind changes, coupled with the velocity, which did the damage.

It is believed the fire began from a root burning underground from a minor fire the night before. When the soil caved in there were sufficient embers to be fanned into flame by the strong winds then blowing. In spite of all efforts to control it, this fire spread so quickly it jumped ahead chains at a time to cwfer about 10 acres to the west of the Balmoral road firebreak. At 10.40 a.m. the wind, blowing for short periods at velocities exceeding 70 miles an hour from the north-west, started three spot fires on the edge of a previously winddamaged compartment to the east of the Balmoral road firebreak. These fires “crowned” immediately and an uncontrollable fire developed. 75 m.p.h. Wind Within minutes acres of green trees were ablaze. The smoke rose thousands of feet and drifted over Christchurch. The wind, estimated gusting up to 75 miles an hour, sent flames 200 to 300 ft long racing through the tree tops. By midday it had reached the highway. Fire-engines came from Waiau, Culverden, Christchurch and Nelson. There were private tankers and farmers’ trucks with 400gallon tanks and drums of water, dozens of private cars and trucks, and a private pump worked from the Hurunui river. Forestry workers from the West Coast, Golden Downs, Ashley, Eyrewell and Hanmer Springs were helped by local people and troops from Burnham. All the timber destroyed was pine. The 4000-acre block was mostly Corsican pine planted in 1925, with some ponderosa pine and other varieties planted between 1918 and 1925. The plantation to the east of the main road comprised mainly radiata pine. Together the blocks contained 3,000,000 trees. Reasons For Fire In the “New Zealand Journal of Forestry” in 1958. Mr K. W. Prior, then forester at Balmoral, says the primary reasons for the fire were the maldistribution of age classes, and the initial layout of the forest. It was the inflammable material in the windthrown and thinned-to-waste areas which made it possible for such a holocaust. He says the fire proved that, except for access, the system of firebreaks established as the forest was planted was quite useless. A system of firebreaks orientated with the direction of the prevailing wind, and breaking up the forest into small narrow compartments, would j have been infinitely more effective.

An inspection of Balmoral was made by a representative of the Department of Agriculture in 1962 with a view to considering the agricultural potential of the area. Mr Prior had earlier suggested

that a considerable percentage of the forest should be used for farming purposes to avoid the danger of total destruction by fire. Farming Proposal The conclusions reached from the inspection were that, “there is no easy way of converting Balmoral into farming land; it will be expensive to do so, and certainly no outsider would take it on under the present conditions.” This referred to most of Balmoral but a different situation exists with regard to the river flats along the Hurunui river and this is a matter under consideration at the present time. There are other reasons why Balmoral cannot be considered for farming, notably the fact that it is Canterbury's major exotic timber resource now that Eyrewell has been blown down. It is estimated that Canterbury will be short of timber by 1975-1980 and any reduction in the area of Balmoral would increase the expected deficit. At the time Mr Prior’s article was published it was fairly confidently considered that the only method to combat nassella tussock was by tree planting. He believed therefore that large areas of infested land would become available for this purpose to replace the forest land converted to farm land. However, firebreaks have been sown with lucerne, and wide “cross-wind” firebreaks created where two electricity lines pass through the forest. Good Seed Bed From the outset the Forest Service was hopeful that regeneration of Balmoral would occur by natural means, as pine cone seeds are very often unharmed by fires and germinate under suitable conditions of their own accord. The ash left after trees have been burned also provides an excellent seed bed. Previous forest fires, particlularly that I at Taupo, supported this view.

To encourage the germination of seed, contractors used scarifiers to push soil over the seeds.

The task was both large and urgent, and was beyond the departmental resources of manpower and equipment. So contractors put seven tractors into the burned areas and they worked 16 hours a day, seven days a week. Progress was delayed by wind-thrown trees and junior woodsmen from the Golden Downs training school cleared ahead of the tractors with chain saws.

The operation was completed at a cost of less than £2 an acre.

The effect of scarifying was to break up the soil, cover the seeds and conserve moisture, and prevent their being eaten by birds. Germination in the radiata pine block, much of which was scarified, was profuse. Seed fall from Corsican pine did occur, with some natural regeneration resulting without scarification, but the contrast between scarified and unscarified blocks was marked. First Seedlings In addition, the Corsican pine block contained small areas of Pinus banksiana (Jack pine) and Pinus muricata (Bishop’s pine). These two species seeded profusely in response to the fire, and natural regeneration of both was fairly heavy. The difficulties encountered were to remove the undesirable P. muricata and P. banksiana, establish the desirable radiata pine, or Corsican pine, and ensure that the desirable species suppressed the undesirable. The Balmoral fire came at the start of one of the worst droughts in Canterbury’s history. Features of the drought were high temperatures, low humidities, and frequent north-west winds. Under these conditions light falls of rain did not penetrate the ground and were quite ineffective.

The first seedlings appeared in mid-February, but in insignificant quantities. Germination in quantity did not begin until after the drought broke on March 19. Almost immediately profuse germination took place on scarified ground, and scattered seedlings appeared elsewhere. The bulk of the seed germinated by the end of May. The total germination between March, 1956, and

July, 1957, is estimated at 17.000 seedlings an acre.

Early, heavy thinning encouraged diameter growth and later thinning to 300 to the acre gave example choice for the selection of good form trees. Many selected trees are now nearly 30ft high.

The young trees had to survive heavy frosts which tended to lift them from the ground. Another problem was a noctuid caterpillar which fed on the stem and leaves of the young trees, and birds, cut worm and grass grub also took a toll. Trees Planted Young trees from the Ashley State Forest nursery were planted in the Corsican pine blocks. Salvage of Balmoral timber was not suspended; but in September, 1956, sawmillers were given the opportunity to buy green timber again, because the proportion of sap stain was increasing in the burned radiata pine. Twenty-one logging contractors operating in the forest and about half of the burned-out area of radiata pine was salvaged. What are the fire prevention measures in operation in Balmoral Forest today? During periods of extreme danger all personnel are withdrawn from the forest, and patrols are sent out to cover “blind” areas. Throughout the fire season a fire look-out is constantly maintained. The development of markets unavailable before the fire has permitted logging to a plan designed to ensure a better spread of age classes throughout the forest and within compartments. This means continuous areas of forest in one condition, with periodic concentration of fire hazardous vegetation are broken up into smaller areas at different stages of development. This results in a smaller build-up of fire hazardous vegetation at different times in each area. Better Firebreaks There has been a steady development in sowing firebreaks to lucerne, a fire safe ground cover, and the unusual step has been taken of granting long term leases over State Forest land on the forest perimeter to encourage the development of fields in lucerne. When two power transmission lines were put through the forest it was necessary to utilise the breaks so created as major firebreaks, although they were not ideally situated as “into-the-wind” breaks.

Another important factor has been the introduction of more efficient radio communication. Should a fire occur in Balmoral an efficient fire fighting organisation is available, as it was in 1955, based on the principles of early detection, rapid transport of all men and equipment, and the use of proven fire fighting methods by well drilled crews. After the fire is controlled the safety of the forest is assured by patrolling until it is certain the fire is out.