Talk, Gesellschaft für Ökologie (GfÖ) Annual Meeting 2015, Göttingen: 2015-08-31 - 2015-09-04
On oceanic-volcanic islands primary succession is one of the major processes of species assembly and vegetation formation due to the frequent creation of sterile volcanic soils from volcanic eruptions and lava flows. Previous studies suggest that speed and trajectory of primary succession are influenced by lava flow age, temperature and moisture availability, but also by the status of species present (e.g. non-natives, endemics, etc.). Whereas other archipelagos have been well studied (Hawaii, Azores, Mascarenes), primary succession on the Canary Islands is understudied so far. However, succession on this subtropical archipelago might show different succession patterns and trajectories due to the relative aridity of the islands compared to more tropical or temperate islands. Here, we present the first study on primary succession on lava flows from the Canary Islands using the southern part of La Palma, one of the youngest islands of the archipelago, as our model system. La Palma offers a more than 500-year-old chronosequence of historically dated lava flows, varying in age as well as in prevalent environmental conditions such as temperature and precipitation. We sampled all vascular plants, mosses and lichens in 16 m2 plots, enabling a full assessment of succession processes. We find that species richness shows a unimodal relation with age, temperature and precipitation, and a negative linear relationship with topographic complexity. However, no clear successional groups of species composition were identified, indicating that primary succession on the Canary Islands develops by stochastic filling of additional species rather than clear successional groups, as is the case in other systems (e.g. glacier forefields). Studying primary succession on volcanic islands is not only important to identify successional patterns and processes but might also allow a better assessment of the possible existence (or non-existence) of gene flow barriers for evolutionary studies.