Seedling establishment in Olea europaea: Seed size and microhabitat affect growth and survival

• Published in: Écoscience (Sainte-Foy) 2004, Vol.11 (3), p.310-320
• Main Authors: Rey, P.J, Alcantara, J.M, Valera, F, Sanchez-Lafuente, A.M, Garrido, J.L, Ramirez, J.M, Manzaneda, A.J
• Format: Article
• Language: English
• Subjects: Cotyledons; forest trees; Leaf area; Microhabitats; mortality; Olea eropaea var. sylvestris; Olea europaea; Pine trees; Plant ecology; Plants; Seed size; Seedling growth; Seedlings; seeds; Trees; wild plants
• ISSN: 1195-6860; 2376-7626
• DOI: 10.1080/11956860.2004.11682838

We investigated the effects of seed size and microhabitat on the dynamics of seedling establishment in Olea europaea. We tested the hypothesis that the type of microhabitat suitable for O. europaea recruitment is influenced by microhabitat-specific relationships between seed size and seedling growth rate. To test this hypothesis we conducted field experiments evaluating seedling growth and survival as a function of seed size, microhabitat (determined by presence/absence of scrub cover), and competition (established by means of seedling density gradients). Our results show that, first, seed size was related to seedling size and to differential growth rate. Second, seedling growth rate was negatively correlated with initial seedling size, although this correlation varied among microhabitats and temporally. Third, seedling survival differed between microhabitats and was positively affected by initial seedling size until the end of the summer drought. Finally, the effect of seedling size on survival was partly mediated by its negative relationship with growth rate. However, the combined effect of size and growth on seedling survival varied between microhabitats. We conclude that establishment depended on microhabitats through facilitation and inhibition processes, and that seed size-related growth rate strongly affected seedling fate. It is noteworthy that the effectiveness of the size-correlated growth depended on microhabitat. Nous avons étudié les effets de la taille des graines et du microhabitat sur la dynamique d'établissement des plantules chez l'olivier (Olea europaea). Nous avons vérifé l'hypothèse selon laquelle le type de microhabitat favorable au recrutement de O. europaea est influencé par des relations existant entre la taille des graines et le taux de croissance des plantules qui sont spécifiques au microhabitat. Nous avons mené des expériences sur le terrain visant à évaluer la croissance et la survie des plantules en fonction de la taille des graines, du microhabitat (déterminé par la présence ou l'absence de couvert arbustif) et de la compétition (établie à l'aide de gradients de densité de plantules). La taille des graines est reliée à la taille des plantules et au taux de croissance différentiel. Le taux de croissance des plantules est corrélé de façon négative à la taille initiale des plantules. Cette corrélation varie toutefois dans le temps selon les microhabitats. La survie des plantules diffère entre les microhabitats et est influencée