Masterarbeit

Diameter distributions of Pinus canariensis across environmental gradients

Moritz Stehmann (01/2025-07/2025)

Betreuer: Carl Beierkuhnlein, Robert Weigel

Climatic conditions and fire events are important drivers impacting the vegetation patterns on La Palma. Characteristic for La Palma are the natural pine forests stands consisting mainly out of the endemic species Pinus canariensis. P. canariensis is known for its broad ecological amplitude enabling P. canariensis to spread from near the coast line up until the treeline. It is also known for its fire resistance. The pinewoods are especially crucial for the islands freshwater availability, due to the promotion of fog condensation. This study aims to investigate the role of elevation on the Diameter at Breast Height (DBH) skewness to evaluate the demographic composition of pine forests stands across La Palma’s environmental gradient. To do so, field measurements (155 plots, 588 trees) and remote sensing data were combined, and a clustering based of on a Principal Component Analysis (PCA), paired with a Kolmogorov-Smirnov-Test (KS-Test) was performed. Lastly, Generalized Additive Models (GAMs) were fitted. Regardless of climatic conditions, the DBH skewness of pine forest stands on La Palma does not differ significantly between sites. Furthermore, DBH skewness is not significantly influenced by the elevation, while temperature variables, annual precipitation, and time since the last fire event significantly affect the DBH skewness. This suggests that the regeneration of P. canariensis largely depends on the occurrence of disturbance events, intraspecific competition and micro-climatic variability, highlighting that favorable growing conditions do not necessarily turn into a demographically stabler population structure. It remains unclear how the pine woods will develop in the future, especially under climate change induced pressure.