Evaluating Structural Complexity in Secondary Habitats and Its Functional Implications in Tenerife, Spain

Oceanic islands are biodiversity hotspots but remain highly threatened and underrepresented in ecological research. Structural complexity is a key biodiversity indicator that can be measured across different habitats and along successional gradients. It is driven by both abiotic and biotic factors, such as climate and species diversity, and is believed to be related to biomass accumulation. In Tenerife (Canary Islands), little is known about structural complexity in secondary habitats despite their large spatial extent across the island. This study quantifies structural complexity in four main secondary habitats in Tenerife through the measurement of the Stand Structural Complexity Index (SSCI), derived from terrestrial laser scanning (TLS), a remote-sensing technique. A total of 19 plots were sampled across the four secondary communities and compared with 18 plots from their corresponding primary counterparts. SSCI values were averaged per plot resulting in a total of 37 observations. Permutation ANOVA results showed no significant differences between secondary and primary SSCI values, except between pine forest and its secondary community, Escobonales. Structural complexity components were further explored using principal component analysis (PCA). Vegetation architecture differs across habitats type and successional status, suggesting distinct ecological configurations. Finally, the relationship between structural complexity and above-ground biomass (AGB) was examined using a robust mixed linear model. No significant relationship was detected, although habitats with higher SSCI generally exhibited higher biomass. Overall, our results suggest that secondary habitats may contribute to ecosystem functioning through their structural complexity where primary vegetation has been largely replaced. Structural complexity metrics such as SSCI therefore represent a promising tool for conservation planning, ecosystem monitoring and management in oceanic islands.