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Abstract

This paper presents results of a phenological study on European larch (Larix decidua Mill.) trees growing in two localities at altitudes differing by 325 m. In both cases, trees grew in mixed stands of the 2nd age category. It was found out that there was a great variability in beginnings and durations of individual phenological stages. These differences were influenced above all by weather conditions existing in individual years. Temperature requirements of European larch were evaluated on the base of sums of temperatures. Obtained results indicated that the onset of spring phenological stages was dependent on temperatures of air and soil already at the end of winter and then in early spring. Measurements performed in the higher locality demonstrated that in recent years there was a slightly earlier beginning of the growing season and that the duration of spring phenological stages was shorter. On the other hand, however, the onset of autumnal phenological stages was delayed, and they continued till the late autumn. The growing season was prolonged and sums of temperatures were higher. The evaluation of obtained data corroborated the existence of a vertical phenological gradient. Therefore it can be concluded that a long-term prolongation of the growing season to the detriment of dormancy could show a negative effect on the health condition and stability of forest stands.