Archived project

Forest resilience and post-disturbance dynamics: the role of species composition and structure

Goal: This project includes the papers in Martina Sánchez-Pinillos's PhD thesis. It aims at contributing to the assessment and quantification of forest resistance and resilience to natural disturbances with the final aim of getting insights into the processes underlying post-disturbance dynamics. To this purpose, it combines the development of methodological approaches with practical applications for different forest types and disturbance events.

Date: 15 September 2014 - 3 June 2019

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Martina Sánchez-Pinillos
added 4 research items
The persistence of non-serotinous pines in Mediterranean forests can be threatened by climate-mediated changes in fire regimes that may favor the dominance of resprouters or other fire-adapted species. Recovery of non-serotinous pines after large wildfires is often determined by their ability to grow under the canopy of promptly established resprouters. Mechanisms of facilitation or competition between resprouters and pines will thus have a profound effect on forest dynamics. We examined here the effect of neighboring oak resprouts on Pinus nigra Arn. ssp. salzmannii saplings 18 years after a wildfire. We determined the net outcome of interactions between oaks and pines and how they vary with the life stage and size of the interacting plants or the environmental conditions. We did not find any net facilitative effects of oaks on pine sapling growth. The sensitivity of pines to neighbors varied markedly with pine size, and to a lesser extent, with water availability during the growing season. Our findings suggest a self-reinforcing hierarchical process by which early-dispersed seedlings growing in low-competitive microsites can grow faster, mitigating neighboring competition in the later stage of canopy closure. These results entail a potentially critical role of management practices to promote post-fire recovery of non-serotinous pines under expected changing conditions of disturbance regimes.
Understanding ecosystem vulnerability is essential in risk management to anticipate disasters. While valuable efforts have been made to characterize vulnerability components (exposure, sensitivity, and response capacity) at particular ecosystem stages, there is still a lack of context-specific studies accounting for the temporal dimension of vulnerability. In this study, we developed a procedure to identify the main natural dynamics of monospecific and mixed forests and to assess the variations of sensitivity and response capacity to fire along successional dynamics. In the procedure, we generated forest chronosequences by summarizing the dynamics between consecutive surveys of permanent plots into a set of longer successional trajectories represented in a multidimensional space. Then, we calculated several variables of sensitivity and response capacity to fire of forest stages associated with each trajectory and we assessed their variation along succession. The procedure was applied to Mediterranean forests in Spain dominated by a pine species poorly adapted to severe crown fires. We found that forest vulnerability components varied differently among successional trajectories, which depended on the composition and structure of their initial stages and the environmental context in which they occurred. Autosuccessional dynamics of pine forests showed relatively low sensitivity to fire along trajectories. However, their response capacity was related to the changes in shrub cover. In contrast, diversifying dynamics showed an increasing sensitivity to fire, but also a higher response capacity the greater the functional diversity along succession. These results highlight the need for considering the temporal dimension of vulnerability in risk management and the importance of assessing sensitivity and response capacity as independent components of vulnerability that can be modified through management at critical forest stages.
Martina Sánchez-Pinillos
added a project goal
This project includes the papers in Martina Sánchez-Pinillos's PhD thesis. It aims at contributing to the assessment and quantification of forest resistance and resilience to natural disturbances with the final aim of getting insights into the processes underlying post-disturbance dynamics. To this purpose, it combines the development of methodological approaches with practical applications for different forest types and disturbance events.