Acacia mangium monocultures can catalyse the recovery of the tree community and aboveground carbon stock in the Philippines

Acacia mangium monocultures have been widely planted in national and internationally funded reforestation projects in the Philippines. Most plantations have been established for timber production, with the added benefits of enhancing ecosystem functions by capturing carbon (C) and restoring biodiversity. However, the impacts of A. mangium plantations are poorly examined. In this study, we assess the effects of A. mangium monocultures on above and below-ground C storage and the contribution of A. mangium and other tree species to aboveground C stock in reforestation sites at different ages and management stages. We also measured the presence of native species within a chrono-sequence of plantations, along with key soil characteristics. Sites studied were 2, 10, and 24-year-old plantations compared to reference states of Imperata cylindrica grasslands and remnant forests. Our results showed that A. mangium monocultures can transition toward native forest-like communities, with the 24-year-old plantation having an observed species richness of 24 ± 16.7 species compared to that of 45 ± 22.1 of the remnant forest. The shift from A. mangium monoculture to a co-dominance of multiple native species enabled the transition from short- to long-term aboveground C storage, which reached an average value of 79.2 Mg/ha. The topsoil (0–10 cm) C was similar to that of the remnant forest over time, with an average value among landcover types of 53.3 ± 7.9 Mg/ha. Soil pH oscillated following the dynamics of tree community establishment and growth, while total nitrogen and available phosphorus increased over time. We suggest that the versatile traits of A. mangium , occasional harvest for timber and charcoal, the small-scale natural disturbances, and the proximity of forest remnants acted synergistically to promote natural regeneration. Focused on local conditions of the Philippines, our study provides novel insights into the restoration potential of A. mangium plantations in similar tropical landscapes worldwide, offering evidence that it has potential in reforestation to be a nature-based solution for climate change and ecosystem services recovery. • Acacia mangium monocultures recovered aboveground C stock and tree community. • Naturally regenerating A. mangium monocultures promoted a shift to long-term C storage. • Monocultures o f A. mangium can facilitate ecological restoration and commercial benefits. • Plantations of A. mangium can serve as a transitional tool for forest recovery.