Abstract Tropical forests harbour high taxonomic and phytochemical diversity, with specialised metabolites mediating ecological interactions likely contributing to species coexistence. However, tropical forest loss threatens the existence of many tree species, with a risk of irreversible loss of yet undiscovered phytochemicals. While restoration efforts often target taxonomic recovery, the assembly of phytochemical diversity during restoration remains underexplored. In this study, we characterised the phytochemical diversity of naturally regenerating woody species in a biodiversity enrichment experiment consisting of 52 tree islands varying in area and planted tree diversity, embedded in an industrial oil palm plantation in Sumatra, Indonesia. Using untargeted metabolomics, we characterised phytochemical diversity among 76 regenerating woody species from 34 families occurring 10 years after tree islands establishment. Furthermore, we examined how island area and planted tree diversity influenced phytochemical diversity via stem density and diversity of the regenerating woody species. In addition, we assessed the relationship between chemical dissimilarity (pairwise and of the overall community) and community assembly. We found 27,122 phytochemical features, from which around 40% were alkaloids and terpenoids, while 17% remained unclassified, suggesting the presence of novel metabolites. Phytochemical diversity increased with tree island area, whereas the initial planted tree diversity had no significant effects. The effect of area was mediated by the diversity of regenerated species, whereas stem density had no effect. When accounting for sampling coverage, island area also showed a direct positive effect on phytochemical diversity, suggesting additional area‐associated mechanisms beyond differences in sampling completeness. Community‐level chemical structure showed a weak tendency towards overdispersion, suggesting that species tend to be chemically more dissimilar to their neighbours than expected by chance. Synthesis. Our study shows that establishing tree islands within oil palm plantations can enhance phytochemical diversity through natural regeneration. Larger tree islands support higher species diversity and phytochemical diversity, underscoring the role of area in restoration. These insights are important to advance our understanding of the role of phytochemistry in ecosystem recovery and to guide restoration practices aiming to enhance biodiversity and phytochemical diversity in human‐modified landscapes.
Montoya‐Sánchez et al. (Sun,) studied this question.