CONSERVATION OF SOIL

Press, Volume LXXXIII, Issue 25141, 24 March 1947, Page 8

CONSERVATION OF SOIL

EFFECT OF ASHLEY STATE FOREST

DOWNLANDS CATCHMENT AREA

The Ashley State Forest, a few miles north of Rangiora. presents what is probably one of the best examples in the South Island of the value of tree planting in the prevention of erosion in a downlands catchment area. It is an illustration in support of one of the principal points in the policy of the Soil Conservation and Rivers Control Council. “The future wellbeing of this country depends on the productivity of the land, but the permanence of the soil which is threatened by soil erosion is fundamental,” states the council. “One of the necessary steps to cope with this threat is the planting of suitable trees.” Although the Ashley forest was established by the State for the production of timber, its two-fold effect has now become obvious. It is the effect of the forest in halting erosion in a rain-fed watershed that makes the scheme of vital interest to catchment boards throughout New Zealand. The forest reserve covers an area of 5000 acres, and takes in the downlands watershed between the Makerikeri river, which flows into the Ashley, and the south branch of the Kowai river. So far only 2000 acres have been planted, and the State Forest Service’s present plan is to extend the forest at a rate of 300 acres a year. Two of the main streams in the area are Stony creek and Fox’s creek, which are fed by many tributary gullies. It is the area which forms the watershed for Stony creek which shows to best effect the result of the tree planting, as the greater part of the Fox’s creek area has not yet been covered. A representative of “The Press" was recently shown over the reserve by the forest ranger (Mr J. D. Barron) and the forest foreman (Mr C Arps), who pointed out many places in the main valley and the smaller gullies feeding it where land in potential danger of slips had been held by the trees. Control of Stream An example of the results of afforestation was given by Mr Arps, who lived on the property before it was taken over as a Government reserve. He stated that after any heavy rain Stony creek had become a torrent, that the area at the bottom of the main valley had flooded, and that a continuous stream of shingle and boulders had come down with the water. After the firsts two or three years of planting operations a noticeable change had taken place, and now, even during the winter. Stony creek was a well regulated stream. The wettest period for many years was in 1945. when nearly 53 inches of rain was recorded at the forest observatory. The stream kept well within the limits of its banks. The Ashley forest is one of the Tnain catchment areas affecting a large district of valuable farm land at Sefton. This low-lying district has, in the past, suffered greatly through flooding and shingle spreads after long periods of heavy rain. Although the forestry scheme at Ashley is not expected to solve this problem completely, soil erosion authorities agree that the tree planting already finished and the programme that is contemplated for the next few years will do much to alleviate the trouble.

The Ashley forest project was undertaken in 1939 by the Government after representations by the North Canterbury Advisory Qompiittee on Tree Planting, which was becoming concerned at the rapid spread of gorse and the consequent deterioration of the -land. About two-thirds of the trees already planted are pinus radiata. The area adjacent to the homestead block in the Stony creek valley was planted, first, and some of the pines there are now 35 feet high. Low pruning has begun for the first siliviculture treatment and for fire protection.

Corsican pines, because of their hardy nature, have been planted extensively on the ridges, while Douglas firs, which are more brittle before they become firmly established, are placed in the shelter of the gullies. A panoramic view of the forest from the Summit road gives the best indication of the work carried out since the forest was started seven years ago. Wide fire breaks divide each year’s planting. More than 25 miles of roads have already been built on the reserve. and these will be extended to give access to the big area of land to be planted in the future.

This Year’s Planting Planting at the headwaters of Fox’s creek will probably be* started in May. The area inspected there did not reveal any large scale erosion, the principal reason being that since the State Forest Service took over the land the burning off of scrub has been avoided. Mr Barron said that the planting of the area would be facilitated if fires were put down the gullies, but the risk would be too great. Heavy rains after the burning off might mean considerable erosion on the hillsides. Before this season’s trees can be planted, tracks will have to be slashed through the heavy scrub. All the young trees for this year’s programme have been grown at the forest nurseries. Wrenching operations for hardening off these trees will be started after the first heavy rain. The trees will be- left in the ground for a few weeks after that, and then will be lifted and trimmed. The importance of the Ashley State Forest scheme from the point of view of catchment boards was commented on by the Soil Conservation Officer for North Canterbury (Mr R. D. Dick). “This is the most spectacular demonstration in our area of the value of trees in regulating the run-off- of water xfrom downy country.” said Mr Dick “The country there had been grazed and burned for a nuumber of years and the protective covering of soil had been lost. On this low fertility soil the water-holding power of trees is most pronounced.”