A Life-Cycle Approach to Understand Consequences of Silvopastoral Use on Two Native Tree Species of Northern Patagonia

Silvopastoral use in native forests could impact population dynamics of key tree species, with contrasting effects at different life cycle stages. Prior studies in South American temperate forests have mainly focused on initial stages, lacking a comprehensive understanding of the entire life cycle within productive systems. We assessed the population dynamics of two key species of mixed forests in northern Patagonia (Austrocedrus chilensis and Nothofagus dombeyi) under two silvopastoral use intensities (high vs. low), using demographic techniques and population projection models. Over 3 years, we quantified vital rates (survival, fertility, growth, reversion and stasis) and used matrix models to calculate deterministic population growth rates (λ). High-intensity silvopastoral use had predominantly negative effects on the elements of the projection matrices of A. chilensis, whereas N. dombeyi exhibited mostly positive or no changes. As a result, projections indicated slight population decreases for A. chilensis (mostly λ < 1) at high silvopastoral use levels compared to low levels, while N. dombeyi showed similar projections (λ ≅ 1) between use levels. Decreased λ for A. chilensis resulted mainly from lower adult tree survival, while early life stages had limited influence on λ for these long-lived species. In summary, silvopastoral use affects population dynamics of key tree species of these mixed forests of northern Patagonia, with implications for sustainable management. Our findings highlight the importance of considering the entire life cycle and suggest targeted practices to enhance A. chilensis populations.