Adaptive Strategies of Seedlings of Four Mediterranean Co-Occurring Tree Species in Response to Light and Moderate Drought: A Nursery Approach

In Mediterranean environments, light and water are clearly dominant ecological drivers of seedling growth and survival, and their interaction could modify productivity and forest composition. We examine the early response of seedlings of four co-occurring Mediterranean tree species (Pinus pinea, Juniperus thurifera, Quercus ilex and Quercus faginea) grown in the nursery to differing light and water availability conditions. Morphological (survival, height, biomass) and physiological (shoot midday water potential, net photosynthesis, transpiration rate, stomatal conductance, Fv/Fm, PSII and ETR) traits were studied, along with biomass allocation traits and drought resistance and plasticity indices. A significant effect of both factors was mainly shown for growth and morphological traits, while survival, physiological traits and allometry were affected by either water availability or light, being more remarkable the effect of water availability over light. Drought severely limited Q. faginea's survival under both light intensities. The high plasticity of J. thurifera and Q. ilex seedlings to different light and water availability environments will confer these two species with an adaptive advantage in the early growth stages in comparison with P. pinea and Q. faginea seedlings. Thus, to maintain the codominance of the four species, silvicultural interventions should focus on the joint management of all of them.

Automated summary

In Mediterranean environments, both light and water availability significantly affect the growth and survival of seedlings. Water availability has a greater impact on growth and morphological traits compared to light, while survival, physiological traits, and allometry are more affected by water availability or light. Juniperus and Quercus seedlings show higher plasticity to different light and water availability conditions, which gives them an advantage in early growth stages compared to Pinus and Quercus faginea seedlings.