First-year effects of tree sbelters and mulching on survival and growth of Zeen Oak (Quercus canariensis Lamk.) seedlings planted in North-Western Tunisia

Abstract

Forest plantations in North-western Tunisia suffer high early seedling mortality and slow growth. The objective of this paper is to evaluate the survival and growth of planted Zeen Oak (Quercus canariensis Lamk.) in response to tree shelters and mulching. Three tree shelters (non-vented tree shelter, vented tree shelter, and control with no shelters) and five mulch types (Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk (organic mulches), gravel (inorganic mulch) and no mulch) were tested. One year after establishment, seedling mortality rate was very low (2.36 %) and was not significantly affected by any of the studied factors. Seedlings growing inside tree shelters responded with significant increases in height exceeding 50 % that of unsheltered seedlings. This enhanced growth is due to larger number of growth units per annual shoot, and longer annual shoots and growth units. In contrast, the stem diameter growth was severely reduced inside tree shelters, resulting in narrow stems with insufficient strength to support their weight. The unsheltered seedlings were shorter and sturdier, with significantly larger basal diameter in response to the lack of shelter. Mulching had no significant impact on early survival, basal stem diameter or height growth. However, a small beneficial effect, resulting in an increase in the number of internodes and the GU (growth units) length was observed under inorganic mulch suggesting that growth conditions under inorganic mulch were slightly improved. Our results suggest that tree shelters, especially the vented type, could improve the growth of Zeen Oak seedlings planted in North-western Tunisia.