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Salvage logging is thought to have negative impacts on soil functionality because it may increase soil compaction and reduce vegetation cover and soil organic matter content. We investigated whether and to what extent burning and subsequent logging initially altered soil functionality of a Mediterranean forest of Pinus halepensis M. Soil functionality indicators (e.g. soil enzyme activities, basal soil respiration, glomalin-related soil protein, and microbial carbon) were measured in March and October 2017 in unburned forest plots, nearby plots severely burned by wildfire in July 2016, and nearby burned plots severely burned by wildfire and then logged in December 2016 using a lightweight agricultural tractor. The results showed significant differences among three groups: unburned soils sampled in spring (1) and autumn (2), and burned soils (not subject or subject to logging) sampled in spring and autumn. In unburned plots, seasonality had a significant effect, which disappeared in burned plots regardless of whether they had been logged. The burned plots had higher content of organic matter and total nitrogen than the unburned soils but they were not correlated to higher soil respiration or microbial biomass. There were not any differences in any of the soil functionality indicators between the unlogged and logged burned plots. In addition, the burned plots had a higher glomalin-related soil protein content than the unburned soil in the autumn measurement. Overall, the results suggest a short-term wildfire impact of soil properties whereas logging using a lightweight tractor produced no significant impacts in this sparse Mediterranean pine forest.

Prescribed fires are becoming more widely used forest management tool to reduce both fuel load for fire prevention and high-severity wildfires. However, alterations to site conditions and influence on the natural regeneration of these fires in Mediterranean pine forests are still poorly known. Our study investigates how using prescribed fires before or after natural pine seed release could influence changes in germination and individuals’ early survival by altering the composition and structure of these Mediterranean habitats. We ran a seed-sowing experiment to analyse the recruitment patterns of three Mediterranean pine species (Pinus halepensis, Pinus pinaster and Pinus nigra) in three sites where prescribed fires were carried out. In each site, we sowed one representative pine species according to natural habitats. Three treatments (control: sowing without intervention; pre-fire: sowing before prescribed fires; and post-fire: sowing after prescribed fires) were established. In the sown experiment, we tested two biogeographical seed provenances (wetter and drier regions) per species to observe different capabilities of adaptation. Germination and survival of individuals were monitored during one year. We observed that the provenances from drier areas had higher germination and survival rates than those from the wetter ones. The three species seemed to undergo a negative effect in the burned plots. Within the burned area, the pre-fire seeds presented higher germination and early survival rates than post-fire. These outcomes could be useful in fire management planning as a tool to influence forest regeneration.

The soil microbiota is vulnerable to burning; however, it shows some resilience. No indices have yet been developed to assess fire damage related to soil biota. We evaluated the biological soil indices recorded by a Biolog EcoPlate System in a Mediterranean ecosystem. The experiment was carried out in an outdoor forest lysimeter facility (MedForECOtron), where we simulated burns with different burn severities. Burning increased the metabolic diversity of bacteria and most C-substrate utilization groups. Soil organic matter, phosphorus, electric conductivity, and calcium increased with increasing burn severity. Microbial richness and activity, as well as the integrated capacity of soil microbes to use a C source, lowered by burning, but recovered 6 months later. The functional diversity and amount of the C source used by microbes immediately increased after fire, and values remained higher than for unburned soils. We evaluated the changes in the vulnerability and resilience of fire-adapted ecosystems to improve their adaptive forest management. We found that the high burn severity reduced microbial richness, functional diversity, and the C source utilization of soil microbes (marked vulnerability to high temperatures), which recovered in the short term (high resilience). These results help to understand the main mechanisms of the effects of wildfire on semi-arid Mediterranean ecosystems, whose field validation will be helpful for fire prevention planning and restoration of burned areas.

Prescribed burnings reduce the biomass and the risk of wildfires but can also alter soil water repellency. The objective of this study is to evaluate the impact of several prescribed burnings in soil water repellency (SWR). In spring 2016, prescribed burns were carried out at three forest sites located in: (i) Beteta in a pure forest of Pinus nigra Arnold ssp. salzmannii; (ii) El Pozuelo in mixed forest stands of Pinus pinaster Aiton and Pinus nigra Arnold ssp. salzmannii; (iii) Lezuza in mixed forest stands of Pinus halepensis Miller and Pinus pinaster Aiton. Six plots were established in each study area: three burned and three unburned. SWR was measured before and immediately after prescribed burns following a 1-year periodic evaluation. There were seven sampling dates at Beteta and El Pozuelo and nine at Lezuza with six plots and six measurement transects in each plot (36 measurement transects on each date). Soil water content (SWC), soil temperature (ST) and soil organic matter (SOM) were also measured. Our results showed that SWR increased after burning to quickly return to normal values in Lezuza, after 1 month in El Pozuelo and after 1 year in Beteta. Moreover, a significant positive relationship between SWR and both SOM and ST, but a negative one with SWC, were observed, which led SWR to increase after fire passage, also in the summer months. Continuous monitoring of these study sites is recommended to determine if low-intensity burnings promote mid- to long-term changes in soil characteristics.

Prescribed burnings have been generally used for fuel reduction in Mediterranean forest ecosystems and in fire-prone areas. It is usually held that prescribed fire may alter microsite conditions, but very little is known about the impact of prescribed burning on Mediterranean pine species’ natural regeneration. In this study, we aim to know the effect of prescribed burning, soil preparation (scalping) and seed protection on the initial recruitment of Spanish black pine (Pinus nigra Arn. ssp salzmannii), maritime pine (Pinus pinaster Ait.) and Aleppo pine (Pinus halepensis M.) in the Cuenca Mountains (central-eastern Spain) after a 1 year of experiments. Our results indicated that the seed emergence rate was higher in the scalped plots for Maritime pine and Aleppo pine. In the case of Spanish black pine, differences comparing treatments for the emergence rate were weaker. Scalped and protected plots showed the highest seedling survival rate for Aleppo pine and Spanish black pine whereas protected and control plots perform better in the case of Maritime pine. Thus, seed protection is a crucial factor for ensuring seedling survival after the first growing season. By considering our results about early pine species recruitment, prescribed burning must be carefully planned when the natural regeneration of Spanish black pine, maritime pine and Aleppo pine is the aim.

Forest sustainability depends on reliable tree regeneration but seedling survival is affected by climate change and disturbance. Based on seed introduction experiments, we compared recruitment of native pine species in central Spain in totally burned, thinned, and dense stands of Spanish black pine ( Pinus nigra Arn. ssp salzmannii ). Seed sources included P. nigra from three elevations bracketing its range, as well as the fire-adapted species maritime pine ( P. pinaster ) and the mesic-adapted species Scots pine ( P. sylvestris ). In addition, seed predation effect was also tested. Small and large herbivores as well as rodents were excluded using cages. All seeds had high viability in laboratory germination tests and all displayed high emergence in field trials. However, unprotected seedlings and those that emerged in thinned or dense stands did not survive the first growing season. Surviving seedlings were only found in totally burned stands. Protected P. nigra seedlings had the highest survival, reaching 23%. Protected seedlings of P. pinaster and P. sylvestris averaged 11.5% and 10.9%, respectively. Unprotected seedlings of any species had less than 2% survival. The unexpected result of higher mortality under a sheltering canopy compared with open post-wildfire conditions may be due to wetter spring during the experiment. Overall, the results indicate that native species currently still regenerate best within the environment of their present range, even though future climate or fire disturbance may lead to distributional shifts. Protection is necessary for successful pine regeneration in the study region.

Fire has always been a driving factor of life on Earth. Now that mankind has definitely joined the other environmental forces in shaping the planet, lots of species are threatened by human-induced variation in fire regimes. Soil-dwelling organisms, i.e., those organisms that primarily live in soil, suffer the numerous and different consequences of fire occurrence that are, however, often overlooked compared to those on vegetation and wildlife. Most of these organisms live in the uppermost soil layer, where fire-imposed temperatures on the ground are the highest insofar as they are lethal or dangerously upset natural habitats. This contribution is a reasoned collation of findings from a number of works conducted worldwide that aims to gain insight into the immediate and longer-term impacts of single or repeated wild or prescribed fires on one group of soil-dwelling organisms or more. In fire-prone ecosystems, fire is a controlling factor of soil biota biodiversity and activity, but also where it is infrequent its ecological footprint can be substantial and lasting. Generally, the immediate fire impact on soil biota is strictly related to the peak temperatures reached on the ground and their duration, and on a set of soil properties and water content. Vertebrates can escape overheating death by running away, searching for wet niches or burrowing deep into soil. Invertebrates and microorganisms, which have little or no mobility, succumb more easily to fire, but make up for this intrinsic vulnerability thanks to their greater fecundity at the population level. Fire or burn severity, which can generally be defined as loss of organic matter aboveground and belowground, is the key factor of the indirect fire effects on soil-dwelling biota; whereas controlled burns do not often imply any substantial and lasting shift from the original situation, extreme and vast wildfires can have major consequences that may be severer than direct killing. In fact lairs are devastated, nutrient pools are heavily affected, food webs are upset, soil temperature and moisture regimes change, and toxic pyrogenic compounds remain in soil. All types of organisms can recolonise the burned area from their sanctuaries, provided that land use does not change, e.g., to pastures or arable fields, and prompt enough vegetation re-sprouting and/or encroachment prevent substantial soil erosion. Each major taxon has genera or species with useful traits and behaviours to resist fire or to recover from its unwelcome environmental legacy sooner than others. If burned soil does not undergo other fires that occur too closely together for the typical fire regime of that particular area, most of its living components are generally capable of returning to pre-fire levels in times that depend on a series of factors, such as fire severity and post-fire rainfall.

Retranslocation, resorption and relocation of nutrients are important adaptive mechanisms developed by plants to acquire the amount of the nutrients required for growth. They are usual mechanisms in deciduous and conifer trees that occur in Mediterranean regions where drought periods are usual. Soil factors, environmental characteristics and species factors are key drivers of nutrient retranslocation in conifers but is not well understood how soil fertility or intraspecific competition influences the process. We studied retranslocation in Pinus halepensis Mill. stands showing different site quality (differences in climate and intraspecific competition) occurring in Southeast Spain. We monitored reforested mature Aleppo pine forests in stands with differences in site quality, climate and intraspecific competition. Stands were characterised, the content of nutrients of soil and green samples (twigs and pine needles) were recorded, and seasonal nutrient retranslocation was obtained. Site characteristics were related to growth rate and nutrient content of foliage and soil. We evaluated whether the retranslocation of nutrients from older to younger foliage was related to the current-year growth rate and to the nutritional status of the plant as influenced by intraspecific competition. Foliar macronutrient concentrations and the amount of retranslocated macronutrients were seasonal, with differences related to site quality and tree density. As a general trend, nutrient concentrations increased after drought (autumn) and decreased during the growth period (spring). However, some micronutrients (mainly Na and Fe) decreased during both periods. The retranslocation pattern in Aleppo pine reinforced the hypothesis that pine adaptations to drought- and fire-prone habitats are linked to the resilience of these forest types. We developed scientific knowledge to assist decision making in adaptive forest management; e.g. fertilizer recommendations or reforestation programmes.

Mulching application and salvage logging are often performed in forests after wildfire to avoid soil erosion and recover timber values, respectively. Mulch may increase soil moisture and decrease contrasted temperatures, which thus promotes seedling recruitment, whereas logging operations may destroy seedlings or generate soil compaction, which may enhance soil erosion and to cause plant seedling damage. We investigated whether and to what extent postfire mulching application and logging initially altered some mineral soil properties and pine seedling density and growth in contrasting Mediterranean climate sites (Lietor, in SE. Spain, in semiarid climate and A Gudina in NW Spain, in subhumid climate). Twelve plots were set up among four different experimental conditions (mulching + salvage logging, mulching + no salvage logging, no mulching + salvage logging, and no mulching + no salvage logging) in the two sites (semiarid and. subhumid climates). The subhumid site was affected by fire in autumn and the semiarid site was affected by fire in summer. Mulching was applied one and three months after wildfire in A Gudina and Lietor, respectively, whereas logging was applied three months after mulching in Lietor and immediately after mulching in A Gudina. One year after wildfire in A Gudina (Pinus pinaster Ait. stands) and two years after wildfire in Lietor (Pinus halepensis M. stands), all surviving seedlings in each plot were counted. Our results suggest that soil organic matter content and total nitrogen were significantly affected by treatments at Lietor (semiarid climate), whereas no differences were detected at the A Gudina site (subhumid climate). Results confirmed that regardless of whether tree felling took place, mulch treatment improved seedling density (over 40% higher when mulching was applied) and seedling height in the short term in a semiarid climate. The limited water availability and the light demands of pine species could be decisive for understanding the effect of mulching and logging operations for initial seedling recruitment in Lietor. The mulching + logging combination showed the highest seedling density at A Gudina (subhumid climate), which could be related to increased light availability after tree felling. Seedling height, stem dry weight, root length, leave-covered shoot length and leave-covered shoot dry weight were always higher in mulching + salvage logging plots at A Gudina. Our results generally suggest the compatibility between mulching and logging, which enhance initial seeding recruitment in burned semiarid and subhumid Mediterranean pine forests.

In recent decades, fire regimes have been modified by various factors such as changes in land use, global change or forest management policies. The vulnerability of Mediterranean terrestrial ecosystems is increasing due to more severe and frequent droughts. This study aimed to determine the plant response of ecosystems during the short-term post-fire period by relating alpha diversity, floristic richness and tree recruitment dynamics to burn severity 5 years after a wildfire. Our results conclude that in the short term, Pinus halepensis Mill. stands in southeastern Spain quickly recovered alpha diversity values, mainly in areas burned with low severity. We observed that moderate and high severities affected the ecosystem more significantly, showing higher values for the Shannon Index but lower for the Simpson index. Pine recruitment was higher in burned areas, and we found the highest number of Aleppo pine seedlings under a moderate burn severity. Post-fire regeneration functional groups (obligate seeders and resprouters) were promoted under moderate and high burn severity, increasing their abundance. Annual species (mainly herbs) colonized burned areas, persisting with higher presence under moderate burn severity. Restoration tools should be focused on reducing fire severity, mainly in areas at high risk of desertification, and promoting resistance, vulnerability and resilience of these ecosystems.

Salvage logging is the commonest post-fire emergency action, but has unclear ecological effects. In the Mediterranean Basin, drought periods and fire regimes are changing and forest management should be adapted. In summer 2009, a mid-high severity fire burned 968 ha of Aleppo pine (Pinus halepensis Mill.) forest in southeast Spain, which was submitted to salvage logging six months later. In spring 2010, plots were set in untreated and logged areas to monitor the recruitment and survival of the main tree species and three companion species: Stipa tenacissima L. (resprouter), Cistus clusii Dunal and Rosmarinus officinalis L. (obligate seeders). We evaluated responses to different scenarios in relation to intensification of summer droughts and forest management to obtain differences in water stress, growth, and gas exchange to cope with summer drought. Drought was induced by using rain-exclusion shelters and recorded ecophysiological characteristics were obtained with a portable gas exchange system. The main tree species recruitment was poor, but companion species showed a high survival ratio. Lower water stress was found for obligate seeder seedlings, which was higher in logged areas with induced drought. The initial post-fire stage was similar for the studied areas. However, after two drought periods (2010 and 2011), significant differences were found in the morphological and ecophysiological responses. In the unmanaged area, the biggest size of individuals due to the most marked increases in height and coverage were observed mainly in resprouter S. tenacissima. In the area submitted to salvage logging, the growth ratios in plots with induced drought were lower, mainly for seeders. Greater productivity was related to higher transpiration, stomatal conductance, and net photosynthetic ratio, but lower water use efficiency was found in obligate seeders with no drought induction, and S. tenacissima obtained higher values in untreated areas. Our results confirm that both forest management and intensification of summer droughts influenced the resilience and productivity of the ecosystems in the short term. Adaptive forest management after fire can imply successful survival and recovery of plant communities in the mid to long term. This study provide a scientific basis to develop tools for the post-fire restoration of serotinous pine forests occurring in low-altitudinal areas of the Mediterranean Basin, prone to summer droughts and fire events.

International audience; Key messageTo implement adaptive management in post-fire-regenerated Aleppo pine forests, we developed specific biomass equations in two early-thinned climatically contrasting stands. We found thinning enlarged biomass components, although climate primarily constrained biomass accumulation and biomass allocation.• ContextThe increase in burnt surface by wildfires in the Mediterranean Basin has triggered the proliferation of large unmanaged forested areas, particularly Aleppo pine stands in drier and lower altitudinal areas. These young naturally regenerated stands require specific biomass models for accurate carbon stock quantification.• AimsThe aim of this study is to analyse the effects of climate (dry vs. semiarid), age and forest management (early thinning) on biomass accumulation and biomass allocation of young Pinus halepensis components: stem, crown (crown wood, needles and cones) and roots.• MethodsWe sampled 251 individual Aleppo pine trees across an age sequence of 5–16 years old to develop component biomass equations.• ResultsWe observed that biomass allocation differed with climate, age and tree density. The crown was the largest biomass fraction, followed by root fraction and stem fraction. At the most limiting site (semiarid climate), we found major reproductive efforts, which may be shaped by adaptive traits to recurrent fires or recurrent drought episodes.• ConclusionClimate was the first limiting factor to constrain biomass accumulation and biomass allocation. Thinning played a key role in promoting positive effects on biomass components at both sites, which were enlarged under less stressful site conditions (dry climate). These results may help managers understand how altering stand density promotes more resilient forests.

Despite Mediterranean ecosystems' high resilience to fire, both climate and land use change, and alterations in fire regimes increase their vulnerability to fire by affecting the long-term natural recovery of ecosystem services. The objective of this work is to study the effects of fire severity on biochemical soil indicators, such as chemical composition or enzymatic activity, related to time after fire and natural vegetation recovery (soil-plant interphase). Soil samples from three wildfires occurring 3, 15 and 21 years ago were taken in the south-eastern Iberian Peninsula (semiarid climate). Sampling included three fire severity levels in naturally regenerated (and changing to shrublands) Pinus halepensis Mill. forests. In the short-term post-fire period, phosphorus concentration, electrical conductivity and urease activity were positively linked to fire severity, and also influenced β-glucosidade activity in a negative relationship. During the 15–21-year post-fire period, the effects related to medium-high fire severity were negligible and soil quality indicators were linked to natural regeneration success. The results showed that most soil properties recovered in the long term after fire (21 years). These outcomes will help managers and stakeholders to implement management tools to stabilise soils and to restore burned ecosystems affected by medium-high fire severity. Such knowledge can be considered in adaptive forest management to reduce the negative effects of wildfires and desertification, and to improve the resilience of vulnerable ecosystems in a global change scenario. This study was supported by a grant for research initiation provided by the Excma. Diputación Albacete (DIPU4-AB2015) and by the funds provided by University Castilla-La Mancha to the Forest Ecology Research Group. The authors with to thank the Spanish Institute for Agricultural and Food Research and Technology (INIA) for the funding awarded through National Research Projects GEPRIF (RTA2014-00011-C06).

Soil respiration is a major carbon pathway sensitive to environmental changes. Using prescribed burnings to reduce fuel accumulation and lower risks of large-scale wildfires has recently become more important. Prescribed burning can significantly alter the soil environment, but its effect in practice on soil respiration is not sufficiently understood. We evaluated the effects of prescribed burning on soil respiration before and after burning (May–July 2016). Prescribed burning was conducted in two natural pine areas by comparing a mixed stand of Pinus nigra Arn. ssp. salzmannii with Pinus pinaster Ait. to a pure stand of Pinus nigra Arn. ssp. salzmannii in the central Iberian Peninsula. Soil respiration was measured by an EGM-4 (Environmental Gas Monitor) infrared gas analyser in both burned and unburned (control) plots. Burnings were low-intensity, and slightly more energetic in the pure stand given its larger litter volume. Post-burning soil respiration followed a similar evolution to that in the control plots, but was greater in the pure stand burned zone and slightly lower in the burned plots in the mixed stand. No significant differences were found in any stand. Soil respiration significantly changed in temporal evolution due to increasing temperatures when summer began. We conclude that prescribed fire induces no changes in SR immediately after fire. This study helps understand how prescribed burnings can affect soil respiration in pure and mixed Spanish black pine forest stands.

Wildfires play a significant role in many different elements of Mediterranean forest ecosystems. In recent years, prescribed fires have started being used more often as a fuel reduction tool, and also as silvicultural treatment to help the regeneration and health improvement of stands. Apart from the fact that fire may alter microsite conditions, very little is known about the impact of prescribed burning on natural regeneration or plant species renewal in Mediterranean pine forests. Likewise, knowledge about the influence of seedling predators on post-fire regeneration is still scarce. In this study, we aimed to compare the effects of seedling predation on recruitment in earlier stages after prescribed burnings in three pine stands in Central Spain: a pure stand of Pinus nigra; a mixed stand of Pinus halepensis and Pinus pinaster and a mixed stand P. nigra with P. pinaster. In situ we superficially sowed seeds from two different species. In the sowing experiment, we tested two different seed provenances (drier and more humid spanish regions) for each species. In all, 60 plots (30 burned, 30 unburned) per site, with 10 seeding units per plot and more than 20,000 seeds, were used in the whole study. Seedling predation was evaluated by replicating the seeding units inside and outside a wire cage as protection for rodents and birds. Our results showed that prescribed fires alter initial seedling predation intensity: predation was significantly higher in the seedlings grown in the plots affected by prescribed fire. The individuals sown before the fire passed showed slightly more predation than those sown after fire passage. Provenances did not appear as an important predation drive. Understanding the role of the predation associated with these treatments can help improve Mediterranean pine forest management.

Understanding the changes in physicochemical and microbiological soil properties induced by straw soil mulching is very important in the Mediterranean environment, where forest ecosystems are particularly prone to erosion and degradation risks. To fill this gap, this study has evaluated the seasonal changes (from spring to autumn) in important physicochemical soil properties, such as pH or soil organic matter, and enzymatic activities, such as urease or dehydrogenase activities, in burned (treated with mulching or not) plots, compared to non-burned soils, after a wildfire occurred in a Pinus halepensis M. forest. Monitoring activity has confirmed that the treatment of burned soils with straw mulching improves its functionality in the short term. More specifically, although soil pH was stable and electric conductivity noticeably reduced, the organic matter was higher in burned and mulched soils compared to non-burned soils. The increases of basal respiration as well as microbial carbon and glomalin contents after mulching indicated higher activity of soil microorganisms and increased carbon and nitrogen storage. Moreover, all microbiological and enzymatic activities improved, except for dehydrogenase activity (DHA). Overall, this study highlights that soil functionality of wildfire-affected areas significantly benefits with straw mulching treatment.

Sustainable forest management ought to include the production of non-use value, mainly in forests with low value of direct production. Predictions on climate change points out increase in aridity and changes in fire regime (increasing fire risk, recurrence and severity), particularly in the Mediterranean Basin. However, we have to question whether this implies a decrease in forest resilience and productivity. In summer 1994, large forest fires burned a huge surface of Aleppo pine stands in Spain. In areas naturally regenerated, we carried out early thinning and sampled 18 plots. In winter 2008 and 2009, we inventoried all pine trees in sampling plots, recording total height, diameter and canopy cover for scaling-up results to stand-level estimation. In addition, we destructively sampled 54 individual pine trees, selecting various thinning and dating treatments, to measure and estimate biomass and partitioning. The date of thinning influenced allometric relationships, earlier thinning stimulated the productivity of individual pine saplings, increasing the three components of carbon intake. Although, the total net carbon value was lower in almost all thinned plots (at least for short periods after thinning), differences were actually found depending on the cutting age and thinning severity. Control and thinned plots (mainly those thinned earlier and heavier) showed similar amounts of carbon but comprised in a low number of living trees with high productivity. Thus, productivity and carbon storage assessment should be monitored, in the long-term, to check prediction of proposed models for evaluation on early treatments.

Aleppo pine (Pinus halepensis Mill.) is found in discontinuous bands along the Mediterranean Basin, usually at low elevations and in dry climates. This study was conducted to relate bioclimatic zones and geographic distribution with representative individual tree of populations for cone number and weight from the driest to the wettest Aleppo pine forest zones. Epidometric values were recorded in all sample stands in the monitoring plots set in 79 native populations from the Algerian border to the eastern coast of Tunisia, representing a wide range from each region in northern Africa. Simple and multiple regressions were performed on the data. Results showed that the canopy seed bank increased according to elevation, latitudinal and longitudinal gradients. The simple regression analysis showed a latitudinal effect positively relating increasing latitude to greater cone crop. Similarly, longitudinal and elevation variations were related to significant differences in cone dimensions. Higher average seed mass was related to populations located westwards or at higher elevation. The multiple regression analysis indicated that the longitudinal variations were the most determinant geo-positional factors in Aleppo pine cone dimensions and average seed mass in natural Aleppo pine forests in Tunisia.

Fire is an ecological factor in ecosystems around the world, made increasingly more critical by unprecedented shifts in climate and human population pressure. The knowledge gradually acquired on the subject is needed to improve fire behaviour understanding and to enhance fire management decision-making. This issue (Volume 28, issue 7, International Journal of Wildland Fire) is Part 2 of a special issue aimed at synthesising ongoing research on preventive management and post-fire restoration, including characterisation of the wildland–urban interface (WUI) and assessing the post-fire restoration of wilderness and WUI areas. Landscape management was also investigated using remote sensing techniques and simulation modelling to improve ecosystem resilience. As in Part 1 (Volume 28, issue 5, International Journal of Wildland Fire), the current issue covers diverse forest settings under scenarios of changing climate and land use. The broad geographical range of these studies highlights key similarities of wildfire issues around the world, but detailed data show unique local circumstances that must be considered. The new information from these six papers helps advance fire ecology and management during a period of rapid change.

Although fire is an intrinsic factor in most terrestrial biomes, it is often perceived as a negative disturbance that must be suppressed. The application of successful fire prevention policies can lead to unsustainable fire events for ecosystems adapted to a specific fire regime. In addition, new climate and land use scenarios are influencing fire parameters and ecosystem services. Consequently, adaptive forest and landscape management must include knowledge on vulnerability, resistance and resilience of terrestrial ecosystems. To help address this need, we convened a special issue (divided in two separate parts) to synthesise ongoing research focused on obtaining a better understanding of wildfire response decisions and actions, including preventive management and post-fire restoration. We conceived a collection of research studies covering a wide diversity of geographical settings characterised by different climates and forest types, under scenarios of changing climate and land use. Here, we summarise the key findings from the six papers published in the first section of the special issue. They deal with diverse topics and assessments, such as adaptions to fire regimes, the effects of burn severity on the plant–soil interface, and post-fire management taking advantage of indices obtained from satellite images (dNBR, NDVI), dendrochronology, soil sampling and analysis of biological indicators. We highlight the new knowledge developed to enhance fire management decision making in a time of rapidly changing scenarios around the world.

Mediterranean communities have been historically conditioned by fire and have therefore developed adaptive traits. Serotiny is a strategy that increases fire resilience by storing seeds in the canopy, protecting them from heat and delaying their dispersion. Aleppo pine is an important serotinous tree species in the low altitude, near-coastal Mediterranean Basin. Differences in serotinous and non-serotinous cones have been detected previously but in order to resolve a gap in the knowledge on seed adaptation to fire, we focused this study on two fire-prone habitats in southern Italy. Several cones were sampled and opened in an oven at two different temperatures in order to group seeds according to provenance and cone type (serotinous or non-serotinous). The sampled seeds were weighed and their coats were removed. Seed size, embryo diameter and nutritive tissue thickness were recorded. We found that seeds with greater weight and size came from the more humid site and from non-serotinous cones. Also, we observed wax and cutine cells formed a thicker seed coat in seeds from the more humid site using a scanning electron microscope. The scanning electron microscopy/energy dispersive X-ray spectroscopy showed higher Si and Ca concentrations in the covers of serotinous seeds. Seeds from different provenance and cone types have anatomic and morphological differences that confer different properties against heating. This knowledge can improve post-fire management and promote restoration tools.

Increasing anthropic pressure is making forest fires more frequent in the Mediterranean Basin and therefore affecting the response of native flora and fauna. Two large fires occurred in summer, 1994, in the Southeastern Iberian Peninsula. Aleppo pine, the main tree species, regenerated naturally after the fire. In this study we are interested in strategies for maximizing Aleppo pine tree recovery and conservation of its ecosystem. We performed thinning and pruning in the pine tree stands 5 and 10 years after the fire and took measurements on structural patterns and plant diversity using several indices. In addition, we measured macro-lichen and faunal diversity indirectly. Results show significant differences between treated-burned plots and untreated-unburned plots. The plots thinned 10 years after the fire and the unburned plots (mature stands) showed a regular, non-aggregated distribution and a low diameter differentiation. Also, these plots showed similar plant diversity values. The silvicultural treatments did not significantly affect the fauna and lichen index values. The high intensity of thinning and late pruning applied to young Aleppo pine stands improved the structural pattern and plant diversity.

During the last few decades, the number of forest fires has been increasing in the Mediterranean Basin due to several factors, among others global warming. Large burned areas are promoting a higher number of naturally regenerated stands which are being poorly managed in general, causing the risk of new wildfires to increase. The most important conifer in dry areas is Pinus halepensis Mill., a well-adapted species to fire-prone habitats due to its high post-fire seeding capacity. High seedling density in the regenerated areas produces high inter-specific competition, which could induce low cone production related to an insufficient amount of seeds stored in the canopy for post-fire recolonization (immaturity risk); adequate young pine tree stand management is therefore required, mainly based on thinning and pruning. In this study different thinning intensities, with and without pruning, were tested in two Aleppo pine post-fire regenerated areas at 5 and 10 years after a fire event. Significant relationships between seed and cone characteristics to site, treatment, cone age and cone type were found. Also the relatively little importance of Aleppo pine seeds in the soil seed bank was checked. The optimal management strategies for Aleppo pine forests in good site quality 5 years after fire was a final density of 1600 trees ha−1 (plus pruning after 5 years) or 800 trees ha−1 as well as a final density of 800 trees ha−1 plus pruning after 10 years. In poor site quality, the best method was no treatment or thinning to 1600 trees ha−1 5 years after fire plus pruning after another 5 years. This management policy can produce benefits in the reproductive processes of Aleppo pine after fire regeneration, as it shortens the juvenile phase and promotes a higher amount of closed cones stored in the canopy, thus increasing the canopy seed bank and reducing the immaturity risk.

Prescribed fire has been widely used as a fuel reduction tool and silvicultural treatment in Mediterranean forest ecosystems. However, other than the fact that fire may alter microsite conditions, little is known about the impact of prescribed burning on the natural regeneration of Spanish black pine (Pinus nigra Arn. ssp. salzmanii). In this study, we compared the effects of post dispersal seed predation, prescribed burning and vegetation treatment (brushing) on initial recruitment of Spanish black pine in both pure and mixed (with maritime pine, Pinus pinaster Ait.) stands during one year (2014) in the Cuenca Mountains (central-eastern Spain). Seedling recruitment in both pure and mixed stands was negatively affected by prescribed burning but was improved by the vegetation treatment. Post dispersal seed protection was an important factor for seed emergence and early survival success. Prescribed burning must be carefully planned in forest management aimed at regeneration. The influence of fire on natural regeneration should be taken into account for developing guidelines for the management of black pine forests, mainly in the Mediterranean Basin. © 2016 Elsevier B.V.

In fire-and drought-prone Mediterranean forests tree growth and regeneration depend on the moisture regime between fires. Therefore, post-fire tree regeneration will depend on moisture conditions and how they are altered by fire recurrence and climate warming. Aleppo pine forests are the most abundant Circum-Mediterranean ecosystems subjected to frequent wildfires and summer droughts. Because both stressors constrain their reproduction and growth patterns across diverse ecological conditions, these forests represent a suitable system to test how moisture availability drives post-fire regeneration. Aleppo pine is an obligate seeder species that reproduces at an early age after fire. Such precocious behaviour poses the question as to whether post-fire regeneration depends on moisture conditions and the coupling between female cone production and growth. Here, we evaluate if female cone production and radial growth are linked at the tree level in post-fire Aleppo pines by comparing a dry v. a very dry site and considering stands with three different tree densities in south-eastern ESP. We found that trees with higher basal areas produced more female cones and this positive association intensified as the water balance improved. Aleppo pines from the very dry site were more precocious in reproductive terms than pines of the same age from the dry site, but long-term cone production was lower at the very dry site. Lower tree density enhances the resilience of xeric post-fire Aleppo pine forests, in growth and reproduction terms, but this effect can be reversed by droughts. Overall, a more positive water balance improves post-fire regeneration by enhancing growth and cone production. Thus, silvicultural treatments such as thinning should be applied by taking into account the post-fire water balance to maximise growth and cone production in Aleppo pine stands. Our findings illustrate how climate warming could hamper post-fire tree regeneration by aggravating drought stress. © 2015 IAWF., We thank the Spanish Ministry of Science and Innovation for its funding and support to the Forest Ecology Research Group (UCLM, Albacete) in Projects CYCIT-AGL 2008-03602/FOR; AGL 2011-27747/FOR and CONSOLIDER-INGENIO 2010: MONTES (CSD 2008-00040) and FEDER funds. R. Sánchez-Salguero thanks the financial support received from the University of Córdoba-Campus of Excellence ceiA3. We also thank Javier Hedo and Enrique Hernández for their field assistance, and Helen Warburton for reviewing the English.

Despite the low timber productivity of Mediterranean Pinus halepensis Mill. forests in south-eastern Spain, they are a valuable carbon sequestration source which could be extended if young stands and understories were considered. We monitored changes in biomass storage of young Aleppo pine stands naturally regenerated after wildfires, with a diachronic approach from 5 to 16 years old, including pine and understory strata, at two different quality sites (dry and semiarid climates). At each site, we set 21 permanent plots and carried out different thinning intensities at two ages, 5 and 10 years after fires. We found similar post-fire regeneration capacity at both sites in terms of total above-ground biomass storage ~6 Mg ha−1 (3 Mg ha−1 of the above-ground pine biomass plus 3 Mg ha−1 of the above-ground understory biomass), but with a contrasting pine layer structure. Generally, across the diachronic study, the earlier thinning reduced biomass stocks at both sites, except for the best quality site (the dry site), where the earliest thinning (applied at post-fire year 5) enlarged carbon storage by 11 % as compared to non-thinned plots. We found root:shoot ratios of an average 0.37 for the pine layer and 0.45 for the understory layer. These results provided new information which not only furthers our understanding of carbon sequestration in low timber productivity Mediterranean forests, but will also help to develop new guidelines for sustainable management adapted to the high-risk terrestrial carbon losses of fire-prone areas.

The Mediterranean Basin is a fire-prone area. Pinus halepensis Mill. is a naturally growing conifer which is frequently used for reforestation and restoration as it displays some degree of adaption to fire. One of the traits conferring tolerance to fire is the frequent presence of serotinous cones that are thought to protect seeds from fire damage. We checked for the physiological responses of seeds to different intensities of fire and related them to the degree of serotiny of the cones. Germination percentage, mean germination rate and enzymatic activity (α-amylase and protease) were recorded for seeds burned either free or enclosed in cones. We included as experimental factors the following: fire intensity, serotiny and time during which seeds were stored in cones after harvesting and germination stage. Burned seeds (released and enclosed) developed in serotinous cones exhibited higher heat insulation. In released seeds, germination was decreasing according to increasing fire intensity, although we found differences depending on site, serotiny and time stored after harvesting. The enzymatic activity was also found to be related to serotiny and fire intensity. Serotiny is an adaptive trait increasing the tolerance to fire which should be promoted in natural and restored populations.

The current chapter describes the ecological context and post-fire management practices for the most important and fire-prone coniferous tree species in the Mediterranean Basin, the serotinous pine trees. The state of art about evolution, habitat and adaptive strategies of Pinus halepensis Mill, Pinus brutia Ten. and Pinus pinaster Aiton are included. The management of burned areas, from emergency to long-term actions, are included but also the influence of climate change and the changing fire dynamics are discussed. To illustrate it, we included some case studies for the serotinous pine species in both Eastern and Western Mediterranean Basin.

Aleppo pine had a large forest cover in North Africa and along the Mediterranean basin which management is not fully developed and new forest tools are required. In this research, the forest structure, epidometric characteristics and allometric relationships were studied in 79 plots covering four bioclimatic zones from natural even aged forests of Aleppo pine located between eastern Algeria to the western coastal part of Tunisia. To characterize the forest structure three sampling methods were carried out: classical inventories (recording all pine trees), and two simplified approach using one average size or five dominant pine tree per plot. Annual growth increment and cone production were only calculated for the average size tree. Furthermore, the analysis of variance showed non-significant differences recorded between bioclimatic zones in trunk or crown diameter using the two simplified approach. Moreover, a significant decrease from wetter to drier areas in total height, crown height, cone seed production was observed only for average size tree method. However, the analysis of covariance showed significant differences between both approaches in total height, trunk diameter and crown coverage which were largely influenced by the pine tree density. In future investigations, we confirmed previous research that the dominant tree is a good sampling method to examine the site fertility, whereas the average size tree constitutes a valuable approach to study the population growth and reproduction. El pino carrasco muestra una gran cobertura forestal, tanto en el norte de África como en toda la Cuenca Mediterránea, cuyo manejo no está totalmente desarrollado lo que requiere nuevas herramientas de manejo. En esta investigación, se estudiaron la estructura forestal, las características epidométricas y las relaciones alométricas de 79 parcelas distribuidas a lo largo de cuatro zonas bioclimáticas en bosques regulares de pino carrasco situados entre el este de Argelia y la costa este de Túnez. Para caracterizar la estructura forestal se aplicaron tres métodos de muestreo: inventario clásico (midiendo todos los pies) y dos propuestas más sencillas, usando un árbol medio o cinco pies dominantes por parcela. El análisis de varianza no mostraba diferencias significativas de las mediciones de diámetro de tronco y de copa realizadas entre las distintas zonas bioclimáticas usando ambos métodos. Por otra parte, se observó una disminución significativa de las zonas más húmedas a las más secas en altura toral, altura de copa y producción de semillas fue observada aplicando el método de árbol medio. Además, el análisis de covarianzas mostraba diferencias significativas, usando ambas metodologías, en los valores medios de altura total, diámetro de tronco y cobertura de copa que mostraron estar influenciados por los valores de la densidad de arbolado de cada zona. Para futuras investigaciones, confirmamos estudios previos que apuntaban que la propuesta de muestreo de árboles dominantes como un buen método de muestreo para caracterizar la calidad de sitio mientras que la de árbol medio constituye una valiosa propuesta para el estudio del crecimiento de poblaciones y sus características reproductivas.

In the Mediterranean Basin, the number of large-scale fires and, consequently, the area of regenerated forests after a fire have been increasing over the last few decades. Mediterranean pine tree stand regeneration shows differences in growth and reproductive characteristics depending on site quality. Aleppo pine (Pinus halepensis Mill.) is an important obligate seeder species occupying a large surface in this area. In order to study growth and reproductive characteristics depending on different climatic conditions, six sites with similar characteristics (edaphic, exposure, slope) burned in the summer of 1994 were selected along a climate gradient. Different precipitation values determined three different ombroclimates: dry-subhumid, dry and semi-arid. Ten years after the fires, data on growth and cone production were collected from these areas in order to study the pattern of growth and reproduction and the influence of site quality (climate) on them. Results showed significantly higher values for growth and several cone characteristics; furthermore, they were positively related to site quality. Viability and seed germination percentages were higher in sites located in dry-subhumid areas. Serotiny was highest in dry locations (southern sites), and lower percentages were found in low tree density sites. The number of reproductive trees was higher northwards and the reproductive phase was reached in younger stands with lower tree density. In conclusion, results showed a geographical gradient based upon growth and reproductive characteristics, decreasing southwards in contrast to serotiny, which increases in southern sites. Density was found to be a significant factor influencing overall pine stand development.

During the last few decades thousands of hectares of Holm oak (Quercus ilex subsp. ballota) forests have burned in Spain due to the increase in the number of large forest fires. This species is able to resprout after disturbance, so a high density coppice stand regenerates naturally after a fire. In SE Spain, a wildfire affected a Holm oak forest in August, 1993, and another fire occurred in July, 2001. A study was carried out to assess the influence of fire recurrence on the CO2 sink capacity of this forest but also the influence on the soil composition. For this research, several plots were defined and set in the burned area. All resprouts within plots were measured (diameter at 30 cm above ground) and selected individuals were subjected to destructive tests to estimate biomass (above and below ground). By applying allometric relationships to all resprouts, the biomass of the different plots was estimated. To estimate the annual CO2 sink in the study plots, the dry biomass obtained was multiplied by determined conversion factors. A large resprouting event occurred 3 months after the last fire and the estimated biomass suggested that recurrent fires could be negatively related to the vitality of the Holm oak shoots. Results also showed the important contribution of these coppice forests as a CO2 sink. However, fire recurrence decreased the presence of the main soil components and it was not significantly affected by treatments. These results allowed us to establish that the CO2 sink capacity is negatively affected by successive fires. This tendency could be changed by silvicultural treatments aimed to improve growth, vitality and adequate reproduction. Management models of coppice Holm oak stands are needed in order to improve CO2 sink capacity.

The number of forest fires, their severity and recurrence, the surface burned and the duration of fire risk season have increased in the Mediterranean basin over the last few decades. These factors promoted an increase of naturally regenerated, unmanaged pine forests and as a consequence, the risk of new wildfires. Aleppo pine (Pinus halepensis mill.) is an obligate seeder adapted to fire-prone habitats, and a very important timber species affected by this phenomenon. In eastern Spain alone more than 100 000 ha of Aleppo pine forests were burned in summer, 1994. One of the forests (naturally regenerated) was selected in order to design an adequate post-fire management model. Several plots were set in two different sites of the fires considered. Silvicultural treatments were carried out at five and ten years after the fire. All trees in the selected plots were marked and monitored. Growth, reproductive characteristics and several allometric parameters were measured in the treated plots. Several measurements in burned (all treated and control plots) and unburned plots were recorded in order to obtain structural patterns and biodiversity indices, The plots thinned ten years after the fire and the unburned plots showed a regular, non-aggregated distribution pattern and low diameter differentiation. Also, these thinned plots showed biodiversity characteristics similar to mature stands. The increases and final values for growth and reproductive characteristics measured in the monitored plots were different for each site but thinning improved growth and the amount of seeds stored in the canopy, thus insuring a more successful regeneration should fire affect the same site again in the early life stages. The optimal management policy obtained improves growth and reproductive processes, shortens the juvenile phase, accelerates the mature age and increases the canopy seed bank. It reduces the immaturity risk and improves the post-fire resilience.

Pinus halepensis Mill., a widespread, low elevation conifer common in Mediterranean Basin, shows a dual reproductive strategy: post-fire obligate seeder (from serotinous cones) and an early coloniser (from non-serotinous cones). Release of seeds encased in serotinous cones is induced either by fire (pyriscence, serotiny or bradychory) or by drying (xeriscence). Morphological differences in serotinous and non-serotinous cones in natural populations of P. halepensis in Southeastern Italy were analyzed. Relationships between tree size (diameter class) and serotiny were checked by counting and sampling serotinous and non-serotinous cones. The macro and microscopic characteristics that could affect cones’ opening were measured in sampled cones. Protection against high temperatures offered by wood scales was also evaluated by applying different temperatures and time exposures, and following the inner thermal raise. Results showed that non-serotinous cones had bigger resin ducts and more separate scales. Also it was highlighted that ovuliferous scales of serotinous cones were bigger and thicker. These scales had more lamellated (multilayered) sclereid cells, and were significantly thinner with a shorter lumen diameter. Continuous temperature-monitoring heat tests inside cones showed that temperatures close to the cone axis were rather low, so seed germination was not influenced. Results confirm that serotinous cones are more compact, rigid and consistent than non-serotinous cones. These characteristics explain the lower insulation, seed protection and the ease opening of non-serotinous cones as well. In conclusion, opening mechanism of pinecone scales under the effect of fire or dry conditions seem related to anatomic differences and it provides seeds with an efficient protection against heat.

In Spain, wildfires have increased during the last decades with Pinus halepensis forests being the most affected. Cone differentiation and the early flowering of this species in comparison to other native Spanish species, are traits considered as adaptations to postfire regeneration. The high recurrence of fires promotes a high increase in young and immature pine stands with low capability of regeneration. In this study, silvicultural treatments such as thinning and pruning were carried out 5 years after fire in eleven years old P. halepensis stands located in dry and semi-arid sites in SE Spain. The formation of male and female strobili, production of serotinous grey, mature brown and new green cones were recorded six years after treatments. Seed production and germination percentage were also tested. Results showed acceleration in cone and viable seed production in thinned plots, with some differences between sites being recorded. Serotinous cone production also increased as a result of this treatment. Pinus halepensis / thinning / pruning / postfire / reproduction

In Spain, many Pinus halepensis Mill. forests have been seriously affected by significant forest fires in the past decade, in 1994 alone, more than 100 000 ha were burned in Eastern Spain. In order to study the reproductive characteristics of P. halepensis after forest fires, six locations were selected in four areas affected by serious fires in the summer of 1994, and the following different precipitation zones were studied: dry-subhumid, dry and semi-arid. Ten years after the fires, data relevant to the production of pine cones: serotinous (grey), mature (brown), immature (green) and opened cones, was collected from areas with natural post-fire regeneration. Various cone and seed characteristics, such as pine cone seed number and weight, and germination percentage, were measured. The results showed greater production of cones and strobili in high-density sites. The biggest cone sizes (volume) and seed number per cone were related to site quality (dry-subhumid precipitation zone). Also, viability and germination percentages were higher with better site quality, with significant differences in values for serotinous and non-serotinous cones. Despite these differences, the canopy seed bank was large enough to ensure regeneration in this area for this age stand.

Coppice forest stands of Quercus ilex have been one of the forest types most impacted by fire in Spain. After fire, their capability to resprout produces a high density of stems that requires thinning in order to avoid stagnation within the stands. In August 1993 and July 2001, two consecutive fires affected a Quercus ilex coppice stand in SE Spain. This study investigated the effects of different post‐fire thinning treatments and recurrent fires on stock and net new carbon increment (NNCI) in a 6‐year‐old coppice stand. Four degrees of thinning were applied: medium thinning (to a final density of 5000 trees ha–1), drastic thinning (to 1800 trees ha–1), full felling (all trees removed) and no thinning (control). Results showed NNCI was within the lower limit of the average global values reported for net primary productivity of terrestrial ecosystems. The best thinning treatment to maximise both current annual NNCI and mean annual NNCI stimulation, and keep new resprouting within reasonable levels was medium thinning. However, recurrent fires caused the observed net primary productivity to decrease, which allowed us to conclude that stump vitality is affected by successive fires, at least the first year after a new fire.

In 1994, six large fires occurred along a climate gradient in Eastern Spain. Ten-year-old trees were selected in the plots established for each location affected by fire. Each selected tree was measured for height and trunk diameter, the number of female strobili and cones, and grouped into four types. A geographical gradient was determined to study growth by latitude and variations in reproductive characteristics. Height and diameter values decreased southwards with the exception of the lowest-density tree location, where trunk diameters were similar to those in northern locations. Strobilus and cone production were higher in lower tree density locations owing to intraspecific competition and higher availability of water, nutrients and light. Serotiny levels were highest in southern locations, although lower percentages were found in the southern locations with low tree density. The number of reproductive trees was higher with lower tree density. The reproductive phase was reached in the lowest tree density site (also low site quality) and nearly reached in the most northern locations (high tree density as well as high site quality). Results showed a geographical gradient based on growth and reproduction dynamics, where serotiny levels are higher in southern locations. Density was shown to be a significant factor influencing overall pine stand development.