Modelling Pinus pinea forest management to attain natural regeneration under present and future climatic scenarios

Abstract

Natural regeneration-based silviculture has been increasingly regarded as a reliable option in sustainable forest management. However, successful natural regeneration is not always easy to achieve. Recently, new concerns have arisen because of changing future climate. To date, regeneration models have proved helpful in decision-making concerning natural regeneration. The implementation of such models into optimization routines is a promising approach in providing forest managers with accurate tools for forest planning. In the present study, we present a stochastic multistage regeneration model for Pinus pinea L. managed woodlands in Central Spain, where regeneration has been historically unsuccessful. The model is able to quantify recruitment under different silviculture alternatives and varying climatic scenarios, with further application to optimize management scheduling. The regeneration process in the species showed high between-year variation, with all subprocesses (seed production, dispersal, germination, predation, and seedling survival) having the potential to become bottlenecks. However, model simulations demonstrate that current intensive management is responsible for regeneration failure in the long term. Specifically, stand densities at rotation age are too low to guarantee adequate dispersal, the optimal density of seed-producing trees being around 150 stems·ha −1 . In addition, rotation length needs to be extended up to 120 years to benefit from the higher seed production of older trees. Stochastic optimization confirms these results. Regeneration does not appear to worsen under climate change conditions; the species exhibiting resilience worthy of broader consideration in Mediterranean silviculture.Key words: multistage models, transition probability, stochastic spatial optimization, stochastic simulation, climatic change.Résumé : La sylviculture fondée sur la régénération naturelle est de plus en plus considérée comme une option fiable pour l'aménagement forestier durable. Cependant, il n'est pas toujours facile de réussir à établir une régénération naturelle. Récem-ment, de nouvelles préoccupations ont été soulevées en raison des futurs changements climatiques. Jusqu'à présent, les modèles de régénération se sont avérés utiles pour la prise de décision concernant la régénération naturelle. L'application de ces modèles dans des routines d'optimisation est une approche prometteuse pour fournir aux aménagistes forestiers des outils précis pour la planification forestière. Dans la présente étude, nous présentons un modèle de régénération stochastique multistage pour les forêts aménagées de Pinus pinea L. du centre de l'Espagne où la régénération a historiquement été infructueuse. Le modèle est en mesure de quantifier le recrutement en fonction de différentes méthodes sylvicoles et de divers scénarios climatiques, en plus d'optimiser le calendrier d'aménagement. Le processus de régénération de cette espèce a montré une forte variation interannuelle et tous les sous-processus (production, di...

Natural regeneration in Iberian pines: A review of dynamic processes and proposals for management

“…This is in full accordance with the findings of Awada et al (2003), which reveal that P. pinea seedlings can actually tolerate some degree of shading in the initial stages of development. The same observations show that individuals emerging in autumn and closer to adult trees are more likely to survive than seedlings from spring cohorts and isolate individuals (Manso et al, 2014a).…”

“…In this way, regeneration can be considered as a multistage process ( Fig. 1) consisting of underlying consecutive subprocesses that often can be identified as a series of successive survival thresholds for potential seedlings (Pukkala & Kolström, 1992;Manso et al, 2014a). The process begins with the supply of seeds from soil or aerial seedbanks, but seed supply is commonly highly variable at different spatial and temporal scales.…”

Optimizing silviculture in mixed uneven-aged forests to increase the recruitment of browse-sensitive tree species without intervening in ungulate population

“…Namely, several factors which influence the establishment of tree seedlings were not included in the model, e.g., site features (Ameztegui & Coll 2015), tree fertility and dispersal (Amm et al 2014). Stochastic modeling and optimization can partially decrease the uncertainty associated with the response of a forest to silvicultural treatments (Manso et al 2014, Pukkala 2015. Another disadvantage of our optimization was that the impact of ungulates was not directly incorporated into modelling, meaning that scientific evidence on the effectiveness of silviculture for silver fir conservation versus ungulate population control is only deductive.…”

“…However, optimization techniques have not been extensively used in silviculture and no attempts have been made to schedule scenarios that increase the proportion of browse-sensitive tree species in juvenile stages at a given browsing pressure. We identified Manso et al (2014) as the only study that uses the optimization technique to evaluate the suitability of silvicultural alternatives for establishing natural regeneration in temperate forests. However, their study considers pure even-aged stands of a light-demanding species with no incidence of ungulate browsing.…”

A model-based analysis of climate change vulnerability of Pinus pinea stands under multiobjective management in the Northern Plateau of Spain

“…Local die-off processes in less-productive areas have already been identified for stone pine forests in the Central Range of Spain Spathelf et al 2014). This effect will be aggravated by the predicted failure on natural regeneration for the species under drier conditions (Manso et al 2014). For instance, our simulations predict a 95 % drop in CP that will not only affect the profitability of these stands, but also greatly limit natural regeneration.…”