Valuing acorn dispersal and resprouting capacity ecological functions to ensure Mediterranean forest resilience after fire

Abstract

Ecological processes within forests provide vital ecosystem services to society, most of which depend on the persistence of tree cover that can be altered after the impact of a disturbance. The aim of the present study was to examine the role of seed dispersal and resprouting that mediate resilience to large fires and evaluate the economic costs that these ecological functions provide. We used field data from 412 plots of the Spanish National Forest Inventory providing information on pre-and post-fire conditions of Mediterranean Pinus spp. and Quercus spp.-dominated forests. Then, we determined the need for restoration (N Rest ) and estimated the minimum pre-fire densities needed to ensure adequate post-fire cover. Economic valuations were assessed through three different scenarios (Sc) of possible human-management actions aimed at ensuring proper post-fire tree cover: Sc. 1) a prefire management scenario evaluating the costs of planting Quercus spp. seedlings in the understory, mimicking the whole dispersal function; Sc. 2) a pre-fire scenario in which enrichment plantations increased the densities of natural oaks; and Sc. 3) a post-fire scenario where the restoration is done through planting pines within the burned area. Approximately 90% of the burned area (371 out of 412 plots) was able to recover after fire supporting the view that Mediterranean forests are resilient to fire. This resilience was primarily mediated by biotic seed dispersal and posterior resprouting of tree species. These ecological functions saved between 626 and 1,326 €/ha compared to the human-management actions. Ensuring key ecological processes within forests increases forest resilience and recovery after fire leading to a generally significant saving of economic resources. In a perspective of increased future impact of disturbances and decrease availability of economic resources for forest management, the implications of the present study can be far reaching and extended to other forest planning exercises.

Stand-level drivers of tree-species diversification in Mediterranean pine forests after abandonment of traditional practices

“…Advancing knowledge of the ecological factors driving tree-species diversification in Mediterranean forest stands is of major interest, due to the particular vulnerability of this bioclimatic region to the effects of global change (Lindner et al, 2010). In the particular case of black pine-dominated forests, for example, the occurrence of natural diversification processes allowing resprouting species such as oaks to establish in the pine understory is reportedly essential for rapid vegetation recovery after the occurrence of large wildfires (Puerta-Piñero et al, 2011).…”

Viewing forests through the lens of complex systems science

“…The oak stumps reflect past coppice management for charcoal and firewood. The European jay (Garrulus glandarius) disperses acorns into pine stands from old isolated trees growing in nearby fields (Puerta-Pinero et al 2012). The presence of these oaks increases the present adaptability of these forests to fire, because unlike pines, oaks are able to resprout and rapidly establish ground cover and a tree overstory after fires (Rodrigo et al 2004).…”

Hardwood seedling establishment below Aleppo pine depends on thinning intensity in two Mediterranean sites

“…Mixed pine-hardwood forests are expected to be more resilient to disturbances than monospecific pine stands (Jactel et al 2009;Vallejo et al 2006), particularly to allow quicker vegetation recovery after frequent large fires (Puerta-Piñero et al 2012). Favoring the establishment of resprouting hardwood seedlings under Aleppo pine stands is thus recommended, but no clear management methods have yet been established.…”

“…In contrast, hardwood species are mostly resprouters: they have the ability to regrow from dormant buds and belowground reserves after a fire, which promotes faster vegetation recovery and makes them less vulnerable to high fire frequencies (Pausas et al 2004;Schelhaas et al 2010). Resprouter species can thus be considered keystone species for fire-resilient forests (Puerta-Piñero et al 2012). Furthermore, monospecific Aleppo pine stands have been shown to be highly sensitive to insect attacks (Maestre and Cortina 2004) and to reduce plant species richness and diversity in the understory (Chirino et al 2006), whereas mixed pine-hardwood stands are shown to be less sensitive to pest outbreaks and herbivory (Jactel and Brockerhoff 2007), to potentially host greater biodiversity (Cavard et al 2011), and to be more resilient to disturbances and changing environmental conditions for a number of ecosystem processes (Jactel et al 2009;Yachi and Loreau 1999).…”