Soil scarification favors natural regeneration of Pinus pinea in Lebanon forests: Evidences from field and laboratory experiments

Joseph Nakhoul (1) , Mathieu Santonja (2) , Catherine Fernandez (2) , Stephane Greff (2) , Anne Bousquet-Mélou (2) , Sylvie Dupouyet (2) , Nabil Nemer (3) , Salim Kattar (4) , Jihad Abboud (4) , Bernard Prévosto (5)

1 INRAE - Institut National de Recherche pour l’Agriculture, l’Alimentation et l’Environnement
2 IMBE - Institut méditerranéen de biodiversité et d'écologie marine et continentale
3 Department of Agricultural Sciences
4 LIU - Lebanese International University
5 RECOVER - Risques, Ecosystèmes, Vulnérabilité, Environnement, Résilience

Pinus pinea is an important species for ecological and economic reasons in the Mediterranean area and especially in Lebanon. However, conditions of its natural regeneration have received little attention. Our study aimed to test the influence of soil disturbances, predation and autotoxicity on pine regeneration. A seed sowing field experiment was conducted in a mature stand in which two types of soil disturbances were tested (soil scarification and litter burning) in presence or absence of predation. In addition, a laboratory experiment evaluating the influence of litter (present, absent or burned) and green needle leachates (i.e. in order to mimic potential autotoxicity) on seed germination and seedling growth was conducted. Results showed a strong effect of soil disturbance, in particular soil scarification which promoted seedling emergence and early survival, whereas the role of predation was low. Forty to sixty days after seed installation, seedling density peaked at 14.9 ± 0.4 seedling.m in the scarification treatment, 13.1 ± 0.4 in the burning treatment and 8.4 ± 0.4 in the control treatment. However, an unexpected high mortality rate was recorded at the end of the field experiment in all treatments, as after seven months seedling density dropped to 0.2 ± 0.02. In the laboratory experiment, we emphasized an autotoxic effect of green needle aqueous extract on seed germination and seedling growth in the presence of litter. This allelopathic effect could be potentially linked to the presence of quinic acid which was measured as the major metabolite detected in needle aqueous extracts. In conclusion, we recommend soil preparation treatments to favour seedling emergence in combination with thinning to achieve seedling development on the long term.

Mots clés: Litter burning; Germination; Seedling survival; Allelopathic effect; Seedling emergence; Soil disturbances

Domaines: Biodiversité et Ecologie

Joseph Nakhoul, Mathieu Santonja, Catherine Fernandez, Stephane Greff, Anne Bousquet-Mélou, et al.. Soil scarification favors natural regeneration of Pinus pinea in Lebanon forests: Evidences from field and laboratory experiments. Forest Ecology and Management, 2020, 459, pp.117840. ⟨10.1016/j.foreco.2019.117840⟩. ⟨hal-02436399⟩