Topsoil properties and seedling recruitment inLavandula latifolia: stage‐dependence and spatial decoupling of influential parameters

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Abstract
This paper investigates the influence of topsoil texture and chemistry on long‐term patterns of seedling recruitment inLavandula latifolia(Labiatae), an evergreen Mediterranean shrub. The questions addressed are: (1) Are spatial patterns of seedling emergence and survival probabilities related to spatial variation in soil properties? (2) Are the two components of recruitment similarly influenced by the same soil parameters or, alternatively, are they influenced in different ways and/or by different soil parameters? (3) If the latter applies, then do the sets of soil parameters influencing emergence and survival show congruent patterns of spatial variation? Seed progenies from fourteen maternal families were sown at ten widely spaced field sites (between‐site distances in the scale of a few kilometers). Sites differed in average soil characteristics. There was also considerable variation in some soil parameters within sowing sites (distances between soil sampling points in the scale of meters). The seedling recruitment process was monitored for six years. Both the probability of one seed ofL. latifoliagiving rise to an emerged seedling, and the probability of an emerged seedling remaining alive six years past emergence and entering the juvenile age class, were significantly related to topsoil properties. Seedling emergence and survival tended to be influenced by largely non‐overlapping sets of soil properties that were related, respectively, to texture‐ and fertility‐related gradients. These two soil gradients tended to be uncorrelated at the scale of the study, and differed in the apportionment of variance among small (within sites) and large (between sites) spatial scales. While most variance in the emergence‐influencing, texture‐related gradient occurred at the between‐site scale, a considerably greater fraction of variance in the survival‐influencing, fertility‐related gradient occurred at the within‐site scale. It is suggested that, because of fine scale variability in soil fertility, local adaptations ofL. latifoliato soil textural properties enhancing seedling emergence will be easier to evolve than adaptations to fertility‐related features enhancing seedling survival.