Reforestation with multiple tree species is a promoted strategy to mitigate global change and to improve forest resistance against natural hazards. Dryland reforestation often fails because seedlings suffer from harsh conditions in degraded areas. Positive species interactions can overcome recruitment drawbacks by ameliorating environmental stress, but there is a strong need to advance functional insights from well-designed experiments.
The study examines the vitality of 19,712 tree seedlings from 12 species in a Mediterranean common garden experiment (Sardinia). Vitality was assessed as an integrated index of foliage discoloration and defoliation measures, which are in dry areas potential indicators of early plant performance. The experimental design properly replicated all monocultures and a selection of mixed communities with different levels of species richness (SR) and functional diversity (FD). From the second year onwards, a water availability treatment (irrigated versus non-irrigated) was added to the design.
The study concludes that local neighborhood facilitation provides essential assistance for broad-leaved trees passing a critical seedling stage in semi-arid regions. This knowledge can contribute to increased success rates in forest rehabilitation in these regions.
Van de Peer, T., Mereu, S., Verheyen, K., Costa Saura, J.M., Morillas, L., Roales, J., Lo Cascio, M., Spano, D., Paquette, A., Muys, B. 2017. Tree seedling vitality improves with functional diversity in a Mediterranean common garden experiment. Forest Ecology and Management 409, 614–633.