The importance of seed trees in the dioecious conifer Pilgerodendron uviferum for passive restoration of fire disturbed southern bog forests



Biological legacies are important for ecosystem recovery following disturbance as demonstrated by studies in the northern hemisphere. Southern bog forests dominated by the conifer Pilgerodendron uviferum in Northern Patagonia are a typical case of an ecosystem with low resilience to disturbance by fire, which kills most trees and seeds, on which the species depends for regeneration. In this study, we hypothesize that the natural recovery of P. uviferum populations in burned areas is limited by seed availability and this limitation may be exacerbated by the dioecy of the species. Using a multi-scaled approach, we quantified the seed dissemination potential from P. uviferum seed trees, assessed the suitability of substrates for the germination of seedlings, and finally analysed the spatial distribution of seed trees of the species at the landscape level. Our results indicate that 70 years after a fire on Chiloé Island (43°S), natural regeneration from seed trees can assist the recovery of P. uviferum populations following large-scale fire disturbance, but their effect is limited at a landscape level owing to a low number of reproductive female trees (0.3 trees ha−1) and limited seed dispersal (<20 m). In this context, a mixed passive-active restoration approach that takes into account the spatial pattern and sex of seed trees could be the most effective and efficient option to restore not only P. uviferum forests in North Patagonia, but also other heavily disturbed forests with few remnant seed trees, in particular of dioecious species.