Silviculture and Chusquea culeou die-off drive Nothofagus regeneration across a precipitation gradient in subantarctic mixed forests

Abstract

The success of tree regeneration following silvicultural interventions depends on its interaction with landscape-scale disturbances. In the mixed Nothofagus forests of northwesternPatagonia (Argentina), this study evaluates how site conditions modulate the recruitmentin response to the combined effects of silvicultural management and the mass die-offof Chusquea culeou. We quantified the density, composition, age, height, and mortalityof total tree regeneration (diameter at breast height<10 cm) of Nothofagus dombeyi, N.alpina, and N. obliqua (Nothofagaceae) in managed and unmanaged forests located inWest (2200 mm yr−1 mean precipitation), Middle (1800 mm yr−1), and East (1400 mmyr−1) sites. In the West and Middle sites, disturbances acted as compound disturbances,showed higher regeneration density and height in managed compared to unmanaged forest. Segmented regression revealed a regeneration pulse occurring between 2001 and2017, after C. culeou die-off. In the East site, where C. culeou is naturally sparse, regeneration showed delayed establishment and no mortality. Regeneration of the more lightdemanding N. dombeyi and N. obliqua was negatively correlated with C. culeou cover,whereas regeneration of the more shade-tolerant N. alpina declined under high canopyopenness. Regarding the density of established regeneration (height>2 m), the effect ofC. culeou on N. dombeyi became positive when canopy openness>40%, while the effecton N. alpina was negative when openness<15%. These results underscore the critical roleof disturbance interactions in creating temporal windows of opportunity for Nothofagusregeneration and highlight their implications for ecosystem resilience.