TREES FOR CONTROL OF NASSELLA

Press, Volume CI, Issue 29856, 23 June 1962, Page 6

TREES FOR CONTROL OF NASSELLA

Thirteen years ago the Forest Service took over 400 acres at Omihi which had been declared a nassella reserve and planted it in trees. Several varieties were planted, and today there is a fine stand of potential timber. The value of trees as a means of control for nassella has been argued for many years, particularly more recently since the new herbicides and topdressing and oversowing techniques have been developed, but it is generally agreed that afforestation has a definite place as an adjunct to the rehabilitation and development of infested land.

Of the 400 acres planted in the Omihi State Forest in 1949. 86 acres were planted in Pinus radiata, 236 in Corsican pine, 85 in Douglas fir, 20 in Lawson iana and the rest in small blocks of larch, Thuya and Pinus ponderosa. With the exception of the Lawsonianas. these have generally established very well and the effective cover keeping out the light has suppressed the nassella. Although in the odd patches throughout the forest where it is a little open a few tussocks are still growing, they are pale and sickly, and it is doubtful whether any of them have ever seeded. Soil samples have been taken recently to test the number of nassella seeds in the ground that are still viable. During a' visit to the forest this week, Mr H. V. Hinds, conservator of forests-in Canterbury, described the history of the trees. The Pinus radiata, now between 35ft and 49ft high, were originally planted six feet apart at 1200 to the acre to give quicker cover, and experimental blocks are now being thinned to test the level of nassella regrowth which may occur. Dominant trees are also being pruned, and the thinning is being done to leave about 400 to the acre. In another 12 years or so they will be thinned to about 150 to 200 to the acre.

One block was thinned by felling about two years ago and the fallen material seems to be keeping the light out until the crowns of the living trees close in again. The other block was thinned by poisoning which is cheaper and leaves the ground more accessible for pruning work. As well as the trees, dense growth of cocksfoot on the edges of roads is suppressing nassella well and only odd tussocks are showing on the roads and firebreaks. The most effective cover, however, is in the Douglas fir block where the trees, although slower in growing, have completely excluded the light and only the rotting stumps of old tussock can be seen. The Corsican pines have also grown well, although much more slowly than the radiata, and have suppressed the tussock. Mr Hinds said that in establishing trees in this type of country the grass which grew up in the first year was a problem and the young trees frequently had to be freed in the second year. If possible a furrow should be ploughed and the trees planted in the furrow. In 1957 the service extended the Omihi forest by buying another block of 930 acres nearby which was not as badly infested and the first 100 acres was planted the next year. Later the annual

plantings were stepped up to 200 acres a year and more may be done this year if the trees are available. Most of the trees are radiata with Corsican pines being planted on the drier and harder faces and tops. In these areas, however, belts of radiata in triple rows are being planted down the leading ridges to give some shelter and barrier to seed blow until the slower-growing Corsicans take over. Mr Hinds said that within five years trees would give effective cover in nassella areas but even in two years there was a definite diminishing of seed blow. As well as the trees the grass which sprang up with the freedom from grazing had a smothering effect. At the back of the Wash creek block of properties taken over this year by the Lands and Survey Department. the Forest Service has constructed an all-weather vehicle track into part of the 930-acre forestry block and this will be linked up with a road which runs into the block from the Omihi end. Here, on an area which was “kill sprayed” during the Lands and Survey Department control programme earlier in the year, the service is planting about a quarter of’a million trees. Seven men at present are planting between 3000 and 4000 trees a day on moderate to steep slopes with the trees about five feet apart.

As the forest borders one of the Lands and Survey Department’s blocks and is within easy distance of another, the service hopes that some pf this land will be diverted for forestry. Although the emphasis is on retaining the land for farming, there are quite a number of areas

which are broken or too steep for working and would be suitable for trees. Expansion of the Omihi forest would make it a more economic forestry unit. In the utilisation of timber distance from markets is an important factor. In the present recession in the timber trade the first area to feel the effects was Hamner Springs—the furthest from Christchurch— and then Balmoral. With the estimated need for an additional 40,000 acres of trees to make Canterbury self-sufficient in timber by the year 2000, the distance fac-

tor needs to be considered in the planting of new areas. "We don't want to go right out into the backblocks,” Mr Hinds said. This is why the Ashley State Forest is considered so potentially valuable. Growth is good, better than at Balmoral or Eyrewell, and it is not in competition with farming. Gorse is being controlled. Forestry was not claimed to be the whole answer to nassella control, but it was felt it could play an important part in association with other measures on adjacent farm land, Mr Hindis said.