Analysis of phenological functional traits as a contribution for a network of Biodiversity - Ecosystem Functioning (BEF) experiments: the International Diversity Experiment Network with Trees (IDENT)

Forests play a significant role in climate change mitigation by acting as "sinks", absorbing carbon fromthe atmosphere and storing it in biomass and soils. Reforestation with multiple tree species is consideredas an important strategy for improving forest resistance against natural threats. However, particularly indrylands, reforestation often fails because seedlings suffer from severe environmental conditions indegraded areas (Gómez-Aparicio, 2009).The adoption of polyculture plantations, instead of conventional large-scale monocultures, provides longtermbenefits for dealing with climatic uncertainties (van der Plas et al., 2016). The relationship betweenbiodiversity and forest functioning is primarily explored in mature systems, but interactions mechanisms inthe early forest stages are much less investigated.As positive interactions between species could help to overcome environmental stress leading toimproved survival of seedlings, there is a strong need to better understand how the different componentsof diversity, i.e., species richness and functional diversity, contribute to ecosystem functioning (Tobner etal., 2016).The International Diversity Experiment Network with Trees (IDENT) (Tobner et al., 2014; Verheyen et al., 2016)investigates questions related to intraspecific trait variation, complementarity, and environmental stressconducting research at several hierarchical levels: within individuals, neighborhoods, and communities.The goal of IDENT is to identify some of the mechanisms through which individuals and species interact topromote coexistence and the complementary use of resources. Temporal complementarity, i.e. use ofresources at different times of the year, is believed to be one of the mechanisms leading to positive BEFrelationships. In this sense, it is fundamental to understanding how species differently regulate theirphenological phases. This study was conducted in the experimental garden located at the nursery "St.Antonio - Sardinian Forest Authority" in Macomer, Italy (40°14' N; 8°42' E; 640 m above sea level). Theexperimental design properly replicated all monocultures and a selection of mixed communities withdifferent levels of species richness (SR) and functional diversity (FD) considering a total of 12 species (Vande Peer et al., 2018).