Influence of mulching and tree shelters on 4-year survival and growth of zeen oak (Quercus canariensis) seedlings

We assessed the effect of mulching and tree shelters on the establishment and early growth of zeen oak (Quercus canariensis Willd.) during the first 4 years after planting in Northwestern Tunisia. Five mulch types (Italian Stone Pine (Pinus pinea L.), Lentisk (Pistacia lentiscus L.), and a combination of Italian Stone Pine and Lentisk (organic mulches), gravel (inorganic mulch) and control), and three tree shelter types (non-vented and vented tree shelters, and control) were tested. An increase in the number of internodes occurred under the gravel mulch, while a reduction in survival was found for the lentisk mulch. Tree shelters had no effect on survival, but increased mean height growth and reduced mean diameter growth during the 4 years (excepting a non-significant effect for vented tree shelter at year four). Comparison of the annual shoots and growth units (GU) between sheltered and unsheltered plants according to year of formation revealed two growth phases. In first phase, shoots were totally or partially inside the shelters; mean length of annual shoots and GU were greater for sheltered plants. The second phase was characterized by shoots emerging from shelters; mean length of annual shoots and GU were similar for all plants, with or without tree shelters. Results suggest that the use of tree shelters, particularly vented shelters, could contribute to the improvement of the artificial regeneration of zeen oak. The use of mulching alone or in combination with tree shelters did not improve zeen oak performance in the field

First-year effects of tree shelters and mulching on survival and growth of zeen oak (Quercus canadensis Lamk.) seedlings planted in North-western Tunisia

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

Development of cork oak (Quercus suber L.) seedlings in response to tree shelters and mulching in northwestern Tunisia

The need for reforestation in cork oak (Quercus suber L.) areas is challenged by difficulties. Principal among these is herbivory of young plants, vegetative competition, and slow growth rates of cork oak seedlings. We evaluated the early development of cork oak seedlings treated using tree shelters and mulching in northwestern Tunisia. We tested three tree shelter treatments (non-vented, vented, and control) to shield seedlings from animal damage and five mulch types to control competing vegetation (Italian Stone Pine, Lentisk, combination of Italian Stone Pine and Lentisk (organic mulches), gravel (inorganic mulch) and no mulch). At the end of the two-year experiment, sheltered seedlings were 89-99% taller than unsheltered seedlings and had higher numbers and lengths of shoot growth flushes. In contrast, both stem diameter growth and dry weight biomass (from samples extracted after two years) were significantly reduced inside tree shelters. Root-to-shoot ratio was not significantly different in sheltered vs. unsheltered seedlings, suggesting that tree shelters do not adversely affect this parameter. Mulching alone did not favour growth, but could be beneficial when combined with tree shelters. The combination of vented tree shelters and gravel mulch was the most effective treatment for promoting diameter, height and stem volume growth. © 2013 Northeast Forestry University and Springer-Verlag Berlin Heidelberg