Understanding how agroforestry systems biodiversity drives ecosystem services in degraded habitats

Agroforestry (AF) systems are widely implemented in degraded habitats owing to their potential for ecological restoration. However, the mechanisms by which different levels of biodiversity-taxonomic diversity (TD) and functional diversity (FD)influence ES provisioning along degradation gradients remain unclear. This study examined three habitat types in the karst region of southern China: non-degraded (KND), potentially lightly degraded (PKD), and moderately to heavily degraded (MKD). Using statistical analyses such as Analysis of variance (ANOVA), principal component analysis (PCA), redundancy analysis (RDA), and hierarchical partitioning, we quantitatively assessed the relative contributions of TD and FD to ES in AF systems. Biomass, net primary productivity (NPP), carbon stock, Microclimate Regulation Index (MRI), Soil Quality Index (SQI), and Ecological Rebirth Sense Index (ERSI) were higher in MKD and PKD than in KND. However, except for ERSI (F = 12.512, p = 0.007), the other metrics did not show significant differences among habitats (p > 0.05). In the KND, TD primarily drove variability, highlighting the importance of species dominance in relatively favorable environments. In contrast, in the degraded habitats (PKD and MKD), FD played a more significant role, as indicated by the RDA species scores and independent contributions, suggesting that FD enhanced system stability through trait combinations and redundancy effects, mitigating the negative impact of species loss. This study provides a framework for assessing biodiversity-ecosystem service (BES) relationships and addresses a critical research gap regarding the role of biodiversity in ES provisioning within degraded habitats. This study offers a scientific basis for the ecological restoration and sustainable management of AF systems.