Abstract

Transition from flower to seedling encompasses major processes that define the success of the tree regeneration, and consequently, its study is crucial in the context of forest management. Here, we analysed the transition probability of the reproductive cycle of two Nothofagus species, which formed pure and mixed forests in coastal and mountain geographic locations of Tierra del Fuego (Argentina). Pure deciduous N. pumilio (Np), pure evergreen N. betuloides (Nb), and mixed N. pumilio–N. betuloides (M) forests in coasts and mountains (3 forest types × 2 geographic locations × 20 replicas = 120 replicas) were evaluated. Reproductive structures (female flowers, fruits, seeds, sound seeds, emerged seedlings and surviv- ing seedlings up to 2 years) were studied since 2012–2018. Our results suggested that transition probabilities from flower to surviving seedlings varied inter-annually between N. pumilio and N. betuloides. The hazard ratio in the transition showed an influence of the cohorts and the geographic location on N. pumilio, while forest type and geographic location influenced on N. betuloides. Flower to fruits and seed to seedling were the most critical process in all forest types and locations. Cumula- tive transition probabilities (female flowers to 2-year-old seedlings) for N. pumilio were 0.3–46.2% in Np and 1.4–30.2% in M, and pure and mixed forests reached similar probabilities only in cohort 3. For N. betuloides, these were 2.8–24.4% in Nb and 0.0–6.5% in M. Both Nothofagus species showed a better performance of pure forests in mountains (15.9–46.2% Np; 3.8–24.8% Nb) than in coasts (0.3–16.1% Np; 2.8–5.3% Nb). Through this integrated approach, considering the full reproductive cycle, it is possible to quantify the influence of canopy composition and inter-annual variability in natural forest dynamic, and allows to identify the critical stages of tree recruitment in pure and mixed Nothofagus forests.