Exploring the relationship between forest age and utilitarian plant diversity in the socio-ecological systems of the Brazilian semi-arid.

The increasing conversion of secondary forests into anthropogenic areas, such as croplands, pastures, or homegardens, has been the focus of ecological studies investigating the impacts of human activities on biodiversity. Ethnobiological studies suggest that environmental changes influence the selection of useful plants by local communities, especially in landscapes transformed into mosaics of forests of different ages, affecting their repertoires of useful plants. This study investigated how forest age (early forest, young forest, and mature forest) influenced the richness, composition, versatility, utilitarian redundancy, and the functional trait dimension of plants known to be useful by rural communities, in areas of Cerrado transitioning to Caatinga, in Northeast Brazil. The results indicated that forest age influenced the richness, composition, versatility, and functional trait dimension of useful plants. A higher number of useful species and greater versatility of uses were recorded in young forests, compared to other forests. No relationship was found between forest age and the utilitarian redundancy of useful plants. Our findings highlight that the studied socio-ecological systems perceive forest age as a determinant for the utilization of useful plants. Resource acquisition by people follows a logic of maximizing benefits over costs, making forests in intermediate successional stages more attractive. However, the absence of differences in utilitarian redundancy among these forests of different ages suggests that these human populations may also choose other successional stages for utilitarian purposes. This indicates that the functional trait dimension of plants known to be useful varies across forests of different ages. Our study demonstrates that forests at intermediate successional stages harbor a greater number of useful plants, compared to early and late-stage forests. These findings highlight the importance of such fragments for the provision of plant resources and reinforce the need to develop targeted management and conservation strategies to maintain these essential ecosystem services for human populations.