Influence of light, water stress and shrub cover on sapling survival and height growth: the case of A. unedo, F. ornus and S. domestica under Mediterranean climate
Abstract
Resprouter species are of great interest for Mediterranean forest resilience as they can survive fire or drought by activating dormant vegetative buds to produce regrowth. Understanding which factors control the early growth and survival of these species is needed to develop strategies to enhance stand resilience. In this study, three broadleaved resprouter species, two trees—Fraxinus ornus and Sorbus domestica—and a shrub—Arbutus unedo—were planted under a gradient of pine cover. Sapling survival and height growth were monitored for 6 years, 2 years after their plantation, as well as light and shrub cover. We developed a two-strata forest water balance model, which produces a water stress index. We aimed to determine the effect of light, water stress and shrub cover on sapling survival and height growth using a modelling approach. We found that high levels of transmittance had a negative impact on both survival and height growth of F. ornus and S. domestica, while it had a positive effect on A. unedo growth. Water stress was found to negatively affect survival and height growth of all species. Lastly, shrub cover had an overall positive effect on the survival and growth of saplings, indicating a facilitating effect of the shrubs. Our results suggest that shade-tolerant tree species like F. ornus and S. domestica are more suited to moderate and light cover, while photoinhibition-tolerant shrub species like A. unedo are more adapted to open conditions. To maximize sapling survival and growth, we recommend preserving the shrubby understorey when present
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