Seasonal changes in content of root starch and soluble carbohydrates in 4-6-year old Betula pubescens and Populus tremula

Roots of 4-6-year old European aspen and pubescent birch were collected monthly during 1983-87 and 1983-88, and analyzed to determine their starch, fructose and glucose concentration. Carbohydrate concentrations in aspen roots fluctuated with low levels in May-June. Seasonal variation was not as consistent in birch roots as in aspen roots. The drop during May-June occur as consistently in birch. Total carbohydrate concentrations in roots of birch collected form six latitudes (56-67° N.) in Sweden showed similar patterns of variation. There were no significant difference between starch concentrations among roots of different diameters (2-11 mm), nor did concentrations differ between sites at different distances (5-25 cm) from the main stem. It was difficult to visually differentiate between low and medium starch levels. Some practical implications of the results are discussed.