Adaptation and restoration of Mediterranean forests: the role of the hidden half

Although the root system represents approximately half of the plant biomass, due mainly to difficulties in methodology, it is still poorly investigated and understood. However, Flora Mediterranea 27 — 2017 29 the root system provides essential functions to the plant such as anchorage and water and nutrient uptake. Moreover, in order to cope with environmental constrains, plant roots show high plasticity, which can give important information on specific plant adaptation mechanisms. For example, coarse roots displacement shows a clear asymmetry when plant grows on slope conditions. Thus, root plasticity knowledge may implement plant reforestation and/or afforestation activities, such as seedlings establishment, on steep slopes or in those areas where a prevailing wind occurs. Fine roots, which respond to a strict cost-benefit analysis, are fast produced and discarded in a complex seasonal dynamics and modify their development depending on the soil water availability. In this case, in areas characterized by a seasonal drought period, studying fine root compartment may indicate the best species or genotype for an assisted migration approach. Finally, as all models predict a worsening of climate change effects on Mediterranean vegetation, independently from the type of forest restoration strategy that will be adopted, studies regarding how roots will cope and respond to these stressors become of primary importance.