Effects of interspecific competition on periodic shoot elongation in oak seedlings

Abstract

The effects of interspecific competition on periodic shoot elongation of Quercuspetraea (Matt.) Liebl. and Quercusrobur L. seedlings were investigated in two experiments. In the first experiment, conducted under field conditions, young oaks were grown under various levels of grass and shrub competition. The number of growth flushes produced by the seedlings was assessed on three dates during the summer. In the second experiment, conducted under controlled conditions, seedlings were grown under various levels of competition and watering regimes. Biweekly measurements of shoot elongation were made during two consecutive growing seasons. Seedlings grown with competition produced fewer growth flushes during the growing season, and those flushes were delayed. They also produced fewer growth units during each flush and those growth units were shorter. All the seedlings grown without competition flushed at the same time during the entire growing season. On the contrary, the seedlings grown with competition showed synchronous flushing in spring, but became asynchronous later in the growing season.