Moderate effects of species mixing on the growth and drought response of Austrocedrus chilensis in northern Patagonia

Abstract

Accelerated climate warming, marked by rising temperatures and reduced precipitation, intensifies droughts, causing severe impacts on forest ecosystems. The mechanisms underlying the loss of tree vigor due to climate warming, are not fully understood. Overall, it appears that vigor loss is moderately controlled by regional climatic patterns and species admixture, as intra- and inter-specific interactions within a stand influence tree growth and drought performance. However, the role of the species mixing under climatic stress remains inconclusive. Here, we applied a dendroecological approach to assess growth trends, climatic responses, and drought performance in Austrocedrus chilensis trees growing under three species stand mixtures (pure, mixed, and diverse) in Patagonia, Argentina. Along the precipitation gradient, the general relationship between A. chilensis growth and moisture availability is driven by regional climatic conditions, while the response to individual extreme events is modulated by species mixing. We found that trees in mixed and diverse stands exhibited a positive growth trend in the recent decades, suggesting a beneficial effect of species combination; though the evidence remains limited on whether this complementarity lessens growth response during droughts. The drought response of A. chilensis was mainly shaped by the precipitation gradient rather than by stand admixture effects. However, species mixing may buffer regional climate impacts, slightly enhancing drought resilience. Comparing nearby stands with different compositions (pure vs. mixed) revealed varying climate-growth relationships, suggesting a coherent species-mixing effect on species growth. In conclusion, this relationship between stand diversity and functioning appears to be influenced by site-specific factors and species identity.