Ecosystem-specific dependence of plant diversity and forest structure on substrate age

The age of ecosystems can strongly influence ecological processes, structural complexity, species composition, and overall ecosystem functioning. Even where bedrock type is similar, differences in geological age may lead to varying performances and characteristics of biological communities, despite comparable successional stages. 

Ecosystem maturity should not be equated with ecological succession. Rather, it refers to the long-term development of sites over extended timescales (exceeding 10,000 years) under broadly similar climatic conditions. In this context, substrate age can shape local biodiversity, disturbance regimes, and vegetation structure. These long-term developmental dynamics differ fundamentally from short-term successional processes (typically less than 100 years), which generally operate at smaller spatial scales and rarely influence entire ecosystems. 

This distinction is particularly relevant in island environments, where recurring volcanic activity often creates a spatial mosaic of substrates of different ages and developmental stages within the same ecosystem type. We inferred maturity from substrate age, contrasting the volcanically active south (< 150 ka) with the dormant north (> 420 – 780 ka) on the oceanic island La Palma 

Comparative analyses of vegetation diversity (including α and β diversity) and forest structure at different stages of maturity show that, in addition to climatic factors, the maturity and substrate age of the ecosystem can also have a significant influence on species richness, the degree of endemism, the composition of the community and the vertical structure. These effects differ in the two examined plant communities. 

These results underline that long-term ecosystem development plays an important, but context-dependent, role in shaping biodiversity and vegetation structure.