effects of stand thinning and artificial shading on epicormic bud emergence in pedunculate oak (Quercus robur L.)

• Published in: Forestry (London) 1988, Vol.61 (1), p.45-59
• Main Authors: Wignall, T.A, Browning, G
• Format: Article
• Language: English
• Subjects: Agronomy. Soil science and plant productions; Artificial regeneration. Forest nurseries. Planting; Biological and medical sciences; budbreak; canopy; Cropping systems. Cultivation. Soil tillage; epicormics; Forestry; Fundamental and applied biological sciences. Psychology; General agronomy. Plant production; inhibition; light transmission; Quercus robur; shade; thinning; Tillage. Tending. Growth control
• ISSN: 0015-752X; 1464-3626
• DOI: 10.1093/forestry/61.1.45

Although previous studies have shown stand thinning increases oak wood quality defects due to epicormic branch development, thinning failed in experiments at three different sites to stimulate epicormic bud emergence or later growth in either the first, second or third years. This was in spite of much higher irradiances beneath the thinned canopies, which transmitted 73 percent more light than the unthinned stand during the summer months. Irradiances beneath the thinned stands were increased by only 13 percent in the period during the spring when the epicormic shoots emerged from the bole of the trees, preceding expansion of the leaf canopy. When, using artificial shading, the intensity of light incident on the bole of trees in a thinned stand was reduced by 80 percent, without affecting bark tempertures, the numbers of epicormic shoots which emerged was similar to that on unshaded trees. Epicormic shoot emergence from the boles of thinned trees was completely prevented by excluding light from the bole with aluminium foil, which also reduced bark temperatures. When the foil was substituted by black polythene, which raised bark temperatures, the inhibition of epicormic shoot emergence was only 88 percent. These results indicate that epicormic shoot emergence is not stimulated by increased exposure of the epicormic buds to light in thinned stands, and that light is not normally a major factor controlling epicormic bud emergence. The decrease in wood quality associated with epicormic shoots produced by thinned stands appears on this evidence to be the result of a long term promotion of epicormic branch growth and longevity. Thinning in July, rather than during the winter months, inhibited epicormic shoot emergence the next spring.