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

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 microbabitats 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.