Growth and development of ash (Fraxinus excelsior L.) seedlings on different humus types under a closed forest canopy

Abstract

In Sep. 1995, in stands with ash and oak - beech, 116 two to four-year-old ash (Fraxinus excelsior L.) seedlings were selected in 12 plots in order to assess collar diameter growth, number of leaves, branches and growth flushes (episodes) per seedling, produced during the next two years. At the same time, 30 seedlings were selected to measure the root length and the root: shoot ratio. Seedlings were growing on different levels of soil fertility (humus types of typical mull, acid mull and mull moder), under a dense canopy (2.5% light intensity). The investigation reveals that, under the high shade of the stands, the length of roots as well as root: shoot ratio is greater on more fertile sites (typical mull and acid mull), than on less fertile site (mull moder). However, the mean root length of the seedlings in this deciduous forest never reaches 9 cm, presenting a limited growth on the various humus types and a rather low stability in the thick litter layer on the mull moder humus type. There are no significant differences (P < 0.05) in growth and foliage development of the seedlings produced on the different humus types. After 2 growing seasons, the mean diameter increment does not exceed 0.6 mm. The mean number of branches and leaves increases respectively with 1 and 4-5 units per seedling and that of the growth flushes varies from 2 to 3 units per seedling. As a whole under the full canopy, ash seedlings prove a very poor response to the humus types. The study suggests a proper felling in the closed canopy of the stand in order to encourage the growth and foliage development of the ash seedlings growing on the different humus types.