Dinámica de los pinares de montaña bajo gestión forestal sostenible en un contexto de cambio global

Resumen

The main objective of this thesis is to assess the influence of sustainable forest management at different scales on the dynamics of Pinus sylvestris L. (Scots pine) stands in Central Spain as well as the effects of global change on Mediterranean forests. Firstly, the influence of ecological factors and of the intensity of regeneration fellings on the first stages of the regeneration of P. sylvestris at microscale are assessed. Additionally, several statistical approaches are used to model forest regeneration and the weaknesses and strengths of each are discussed. The alternative approaches show that the number of P. sylvestris seedlings is positively related to heavy fellings and negatively related to sodium content (Chapter 2). On a larger scale (plot level), a spatio-temporal recruitment model is proposed. This model determines the spatial distribution of the saplings as a function of the size of adult trees and the distance between adult trees and saplings. The model detects a negative association between the diameter of adult trees and number of saplings up to a distance of 7 m (Chapter 3). Chapter 4 analyses the way in which two management systems affect the carbon stored in forest pools over the rotation period. The results reveal that less severe management systems with longer rotation periods increase carbon fixation. On the other hand, neither the forest management nor the stand age have a significant effect on the carbon stored in the soil. Finally, the shifts in distribution and changes in abundance of P. sylvestris and Quercus pyrenaica Willd. (Pyrenean oak) as a result of global change over the last 40 years are assessed in the Sierra of Guadarrama (Comunidad de Madrid) are assessed (Chapter 5). Furthermore, it is addressed the performance of a novel method to calculate the significance of climatic variables as auxiliary variables and to estimate which part of the variance is linked to the mean function and which part is linked to the space-time autocorrelation in space-time universal kriging and co-kriging distribution models. The results indicate that both the distribution and the abundance of P. sylvestris remained relatively constant, whereas the distribution and abundance of Q. pyrenaica increased significantly. As a consequence, the area where the two species coexist has increased three fold.