Growth and survival of shoots, roots, and mycorrhizal mycelium in clonal Sitka spruce during the first growing season after planting

Abstract

Rooted cuttings of three Sitka spruce (Piceasitchensis (Bong.) Carr.) clones were grown out of doors in 2 m tall acrylic tubes of peat that projected from the tops of insulated boxes. During the year, periodic measurements were made of temperature and the growth of shoot, root, and extramatrical mycelium of mycorrhizal fungi. Differences were found between clones in total shoot and root growth and in their periodicity, especially in the timing of the onset of root dormancy in the winter. No fine root death was observed during a 7-month period of observation. Most of the plants became colonized by mycorrhizal fungi, and fruiting bodies were produced in the tops of the tubes. Two of the clones were colonized by Thelephoraterrestris (Ehr.) Fr., but in a third clone some plants were colonized by T. terrestris and others by Laccariaproxima (Boud.) Pat. The extramatrical mycelium of T. terrestris grew at about half the rate of the main roots during the summer, and by November it had grown a mean distance of 22 to 25 cm, depending upon the tree clone colonized. The mycelium grew slowly during the winter when the main roots were dormant. The L. proxima mycelium grew much more slowly than the T. terrestris, and it disappeared during the autumn.