Changes in soil chemical properties and plant species composition during primary succession on an oceanic island

Abstract

Questions What is the influence of time and environmental factors such as climate and topography on soil chemical properties and composition of vascular plants during primary succession on lava flows of an oceanic island? How is compositional change characterized and which successional stages can be distinguished? Location La Palma, Canary Islands. Methods We sampled soil properties and vascular plants in 72 plots on a long-term chronosequence of 10 lava flows ranging in age between 40 and over 20,000 years in the semi-arid lowlands of La Palma Island. Soil properties were analyzed by general least-squares models (GLS), while canonical correspondence analysis (CCA), cluster analysis and multiresponse permutation procedures (MRPP) were applied to investigate compositional change. Results Soil characteristics and plant species composition during primary succession were strongly affected by substrate age but also by climatic and topographic factors. Values of most soil properties increased with lava flow age, while pH decreased. Soil organic matter, phosphorus, exchangeable calcium and ammonium revealed a positive correlation with mean annual precipitation. Lava flow age was always the most important independent factor determining plant assembly followed by mean annual precipitation. Four successional stages and their composition of indicator species, life strategies and species status could be defined. Alien species did not alter successional trajectories. Conclusion Time, climate and topography simultaneously affect soil properties and plant composition during primary succession on lava flows. The climatic windward–leeward gradient on La Palma Island influences plant colonization and soil development in the semi-arid coastal areas. Favorable conditions (moisture) can speed up primary succession. Compositional changes suggest convergence during primary succession. During the entire colonization process, dominant successional shrubs are endemics, highlighting the importance of evolutionary adaptation to volcanic disturbances.