EFFECTS OF ESTABLISHMENT METHOD ON ROOT FORM OF LODGEPOLE PINE AND SITKA SPRUCE AND ON THE PRODUCTION OF ADVENTITIOUS ROOTS

Root systems of lodgepole pine and Sitka spruce were measured 15 years after establishment from bare-rooted transplants and direct sowing on a ploughed peat site. On one sample the root systems were divided into eight sectors in plan view for dry weight analysis and measurements were made on branching frequency. On another sample the five largest lateral roots on the Sitka spruce were dissected and sectioned to find whether they originated from the original root system or adventitiously from the stem.Root system form was considerably influenced by the ploughing, with the largest part of the dry weight contained in sectors which included the plough ridge. Although both species were affected to the same degree by the ploughing, statistical analysis showed that the distribution of root weight was more symmetric in the spruce than in the pine. Rooting depth, which was limited by waterlogging, was greater in pine than in spruce, and the development of a taproot from the seedling radical in the direct sown trees did not influence maximum rooting depth. The frequency of major root branches and the incidence of branches arising from injury were similar in all treatments.In the spruce, most of the transplants had major roots of adventitious origin, but adventitious roots were uncommon in the direct sown trees. In the transplants adventitious roots were most frequent (74-84 per cent) in the two largest of the five main roots and least abundant (10 per cent) in the two smallest. The size class distribution of the five main roots was less even in the transplants than in the sown trees, with greater allocation to the largest roots. © 1990 Oxford University Press.