Effect of climatic conditions and tree size on Austrocedrus chilensis–shrub interactions in northern Patagonia

We analyzed how the net balance of the interactions (facilitation and competition) between juvenile trees of Austrocedrus chilensis and shrubs, is affected by climatic conditions and tree size. We quantified the strength of the interactions using a relative facilitation intensity (RFI) index that expresses a proportional increment in plant response due to the presence of shrubs. RFI values were calculated for a range of plant sizes (0.15–5 m tall, and 0.1–10 cm of basal diameter) in two contrasting climatic years. Results showed an increase in the facilitative strength of shrubs, when the abiotic stress was more severe. In turn, an increase in the shrub size-density leads to a decrease in the facilitative strength. A. chilensis (D. Don) Pic Serm et Bizarri size was correlated with the light environment, and the latter imposed some morphological acclimations (large shoot–root ratio and specific leaf area with an increase in shade), that seems to influence its susceptibility to drought. Finally, in order to increase A. chilensis productivity, we used the information about the effect of climatic conditions and tree size to set preliminary vegetation management recommendations. Further research on plant thermal stress is required in order to understand the facilitation process in this species.