Plant fire-adaptive traits mediate long-term fire recurrence impact on the potential supply capacity of ecosystem services and their resilience.

Fire-induced changes in vegetation composition due to fire-regime intensification are leading to alterations in ecosystem services that might threaten their future sustainability. Fire recurrence, in particular, could be a key driver shaping ecosystem service resilience in fire-prone ecosystems. This study evaluates the impact of fire recurrence, over twenty-four years, on the potential supply capacity of ten regulating, provisioning, and cultural services selected as critical services by stakeholders and experts. We assessed fire effects in four fire-prone landscapes dominated by species with different functional-traits response to fire (i.e., obligate seeder vs resprouter species). Trends in the potential supply capacity linked to fire recurrence were estimated by applying a supervised classification of Land Use and Land Cover (LULC) classes performed using Landsat imagery, associated to an ecosystem service capacity matrix adapted to the local socio-ecological context. In landscapes dominated by seeders, fire recurrence broke off the potential supply capacity of services traditionally associated to mature forest cover (i.e., the predicted probability of a decrease in the potential supply capacity of climate regulation, timber, wood fuel, mushroom production, tourism, landscape aesthetic, and cultural heritage occurred with high fire recurrence). In landscapes dominated by resprouter species, the effect of fire recurrence was partially buffered in the short-term after fire and no substantial differences in trends of change were found (i.e., equal predicted probability in the potential supply capacity of ecosystem services regardless of fire recurrence). We detected two new opportunities for ecosystems service supply associated to fire recurrence: livestock and honey production, especially in sites dominated by seeders. These findings provide valuable information aiming at recovering post-fire ecosystem service potential supply to partially counterbalance the loss in the socio-ecological system. When the main post-fire restoration goal is preserving ecosystem service resilience in fire-prone ecosystems, establishing management strategies focused on promoting resprouter species could aid mitigating the fire-driven loss of their supply capacity.

Effect of fire factors (smoke, ash, charcoal and heat) on seeds of plant species.

The effect of the main fire factors (smoke, ash, charcoal and heat) can influence the germination of species through their seeds. Hence, a methodology has been devised in order to have a common protocol for those who work in this area and serve as a valuable tool to compare different species that can be beneficial or detrimental to the conditions of a forest fire. Moreover, the methodology was completed with a check of the viability of the seeds before starting the germination process and another viability test with the non-germinated seeds (dormant or dead) after carrying out the germination test. In this way, the study of the main factors of fire, in combination with the study of the viability of the seeds, can be very useful to know the reproductive behaviour of herbaceous, shrub and tree species in a forest fire scenario. In addition, from the data obtained during the germination process of the seeds, a series of explained parameters can be obtained to better interpret the data acquired from the laboratory experiment and subsequent comparison. For all these reasons, the study of the germination of species in laboratory conditions can help us understand how they behave in the field.

Fire regimes shape diversity and traits of vegetation under different climatic conditions.

Changes in climate and land use are altering fire regimes in many regions across the globe. This work aims to study the influence of wildfire recurrence and burn severity on woody community structure and plant functional traits under different environmental conditions. We selected three study sites along a Mediterranean-Oceanic climatic gradient, where we studied the fire history and burn severity of the last wildfire. Four years after the last wildfire, we established 1776 1-m2 plots where the percentage cover of each woody species was sampled. We calculated (i) structural parameters of the community such as total cover, alpha species richness, evenness and diversity (Shannon diversity index), and (ii) vegetation cover of each functional group (differentiating life forms, eco-physiological traits and regenerative traits). Focusing on community structure, results showed increases in species richness and diversity as wildfire recurrence increased, but this effect was partially counterweighted in the areas affected by high severity. In relation to functional groups, we found that increases in recurrence and severity fostered transition from tree- to shrub-dominated ecosystems. Non-arboreal life form, high specific leaf area, N2-fixing capacity, resprouting ability and heat-stimulated germination were advantageous traits under high recurrences and severities, and low seed mass was advantageous under high recurrence situations. We suggest that the strength of the effects of wildfire recurrence and burn severity on vegetation structure and traits might vary with climate, increasing from Oceanic to Mediterranean conditions. In the Mediterranean site, recurrence and severity were strongly related to traits associated with germination (seed mass and heat-stimulated germination), whereas in the Oceanic site the strongest relationships were found with a resprouting-related trait (bud location). This study identifies changes in vegetation structure and composition in scenarios of high recurrence and severity, and provides useful information on plant traits that could be key in enhancing vegetation resilience.