No abstract

In this study, on the aspects of the resilience of woody species to the passage of fire, we wanted to test the alveolar specificity represented by the size of the pores of the secondary xylem of the root system in Quercus coccifera L., Pore size assessment is based on measuring 100 pores in cross sections, from the roots of 10 shrubs. The aim of this study is to explain how the roots can maintain their vitality after passing a fire and thus guarantee regeneration. In addition to the vigor of the root system of this species, the release of pyrolysis gases and the propagation of heat by conduction are provided by the porosity of the material. The results show that the pores are qualified as “fine” in the initial wood with an average diameter of 83.35 µm. In final wood, they are "very thin" with 42.30 µm in diameter. The absence of oxygen and the less porous structure delay the combustion cycle of the root system, the roots distant from the surface are thus protected from proliferation by heat conduction and thus guarantee regeneration.

This study aims to evaluate the effect of dendrometric and ecological factors on the natural regeneration of the Atlas cedar "Cedrus atlantica Mannetti" in AinAntarforest,Algeria. This study wascarried out in 14 circular plots of 500 m2area.In order to quantify the seedlingclasses, six sub-plots of 1 m2were installed in each plot.The results of the dendrometric data showedthe presence of a "Gaussian distribution" with a dominance offruitingdiameters(37.5 and 57.5 cm).The results of ecological parameters revealedthat in high altitudes, above 1300 m, natural regeneration seemedto be relatively difficult (30% compared to low and medium altitudes). On slopes greater than 30%, seedlings of less than one year old were less present (20 % compared to the seven first plots). The role of the vegetation cover (40–0%), the litter cover (30–40%) and of the soil depth (shallow and deep) appearedto favor the survival of seedlings, especiallywhen they werestill young. The correlation analysis indicatedthat the different seedling classes became less numerous when altitude, slope and basal area increased.

No abstract

ABSTRACT:In order to describe and measure the evolution of vascular elements in time, we examined two groups of samples of the green oak (Quercus ilex Linnaeus) wood. These groups are on the same radial plane and come from two trees growing under identical conditions and with different ages. The first group is located in the internal zone between the 15 th and 19 th growth ring and the second group is situated in the external area before the sapwood. The analysis of results shows the outside zone with isolated, numerous and large vessels compared to the internal zone. The results also explain how the vascular elements develop in advanced age.