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En los últimos años, los incendios forestales se han convertido en un grave riesgo para la conservación de los ecosistemas debido a las modificaciones en el régimen de los mismos, que están condicionadas por el cambio climático y el cambio en los usos del suelo. En el contexto de cambio global actual, el fuego en la cuenca mediterránea -y en particular en la Península Ibérica- se ha convertido no sólo en una perturbación necesaria y beneficiosa para la dinámica natural de los ecosistemas, sino también en un grave riesgo ecológico, social y económico (World Wide Fund for Nature, 2019). La tendencia observada en las últimas décadas es la disminución del número de incendios forestales a nivel mundial, aunque, debido al patrón de aumento de la frecuencia e intensidad de las sequías a lo largo de toda la cuenca mediterránea (Tramblay et al., 2020), se espera que la recurrencia, severidad, extensión y área de influencia de los incendios forestales aumente en los próximos años (Ruffault et al., 2020). Para poder gestionar correctamente los incendios forestales y afrontar estos eventos como herramientas de modelización del paisaje y obtención de energía (Naveh, 1994; Doerr y Santín, 2016) se debe tener en cuenta uno de los principales factores que determinan el régimen del fuego, la recurrencia, entendida como el número de incendios acaecidos en una zona determinada durante un período de tiempo dado (Johnson, 1992; Pausas et al., 2008; Santana, 2019).

The main objective of this study was to analyse the effect of recurrence and burn severity on ecosystem multifunctionality in Pinus pinaster forests. We selected a large wildfire that occurred in the Sierra del Teleno in 2012 (NW Spain), where we differentiated two recurrences and two burn severity situations. As a result, four scenarios were identified: low recurrence plus low severity, low recurrence plus high severity, high recurrence plus low severity, high recurrence plus high severity. In each one, a number of 1 m x 1 m plots proportional to the burned area were established. Three years after the wildfire we evaluated in each plot: (1) percentage of covered soil, (2) total percentage cover of herbaceous species, (3) percentage cover of each woody species, (4) total plant species richness. Also, a composite soil sample was collected from each plot. Chemical (total organic carbon, total nitrogen and available phosphorus) and microbiological (microbial biomass carbon) properties were analysed in each soil sample. The following variables were used as indicators of ecosystem functions: percentage of covered soil, total cover of herbaceous species, Pinus pinaster cover, total plant richness, total organic carbon, total soil nitrogen, available phosphorus and microbial biomass carbon. Another indicator of ecosystem functions was calculated: floral colours of shrub species diversity using the Shannon index. The values of each ecosystem function indicator were standardized. The indicators/functions of regulating ecosystem services were: Climate regulation (indicator: total % of organic soil carbon) and Erosion protection (indicator: covered soil %). The functions/ indicators of supporting ecosystem services were: soil fertility (indicator: total nitrogen and available phosphorous) and soil quality (indicator: microbial biomass C). The indicators/functions of cultural ecosystem services were: species diversity (indicator: plant species richness) and aesthetic value (indicator: the Shannon index of floral colours). The functions/indicators of provisioning ecosystem services were: grass for livestock (indicator: % cover of herbaceous species) and timber production (indicator: % cover of Pinus pinaster). The results indicated that all scenarios apart from low recurrence plus low severity negatively affected the multifunctionality of the ecosystems.

P. 1057–1069 Two drivers of global change that affect ecosystem function include wildland fire regimes characterised by frequent, severe fires and increased atmospheric nitrogen (N) deposition. However, their combined effect on the post-fire recovery of Mediterranean forests is still little known. We assessed the interactive effects of two fire severities and N addition on the rate and timing of seed germination of three woody species with different post-fire regeneration strategies in fire-prone forests: Pinus pinaster, an obligate-seeder species, and two facultative-seeder species, Pterospartum tridentatum (high-resprouting and low-seeding ability) and Halimium lasianthum (low-resprouting and high-seeding ability). Seeds were subjected to six combinations of temperature [control (no heat treatment), 60 °C (moderate fire severity) and 120 °C (high fire severity) for 5 min] and N fertilisation (without N and with addition of 4.17 g Nm−2 of solid granules of ammonium nitrate, equivalent to three times the current estimate of airborne N deposition in the study area) under laboratory conditions. We found that N fertilisation had a significant, negative effect on the rate of seed germination of the three species under study. Additionally, we detected no differences in P. pinaster germination among thermal treatments; while both P. tridentatum and H. lasianthum had significantly higher germination rates when submitted to high fire-severity conditions. Moreover, the average time of seed germination increased with N fertilisation for P. pinaster but increased after the thermal treatments for H. lasianthum. These results suggest that increased N availability under intense wildfire regimes may hinder post-fire seed germination, regardless of the species’ regeneration strategy, in fire-prone pine forests. SI

Projections of future wildfire regimes forecast an increased frequency of large high-severity fires that create very harsh environmental conditions and constitute a challenge to post-fire ecosystem regeneration. Under these new circumstances, better knowledge of the plant interaction mechanisms underlying post-fire seedling establishment success would aid restoration management to achieve the intended targets. We evaluated the combined effect of recurrent large stand-replacing fires and conventional post-fire restoration activities (salvage logging after a single large fire, and direct seeding and linear subsoiling plus seedling planting after two subsequent large fires) on tree seedling recruitment and performance (development, annual growth, and biomass) in the early stages of succession in fire-prone maritime pine ( Pinus pinaster Ait.) ecosystems. We quantified plant facilitative/competitive interactions between naturally recruited pine seedlings, neighbouring seedlings and potential nurse shrubs with different post-fire regeneration strategies (obligate seeders vs resprouters), by computing the relative interaction index (RII). The results evidenced that fire recurrence altered plant species composition and conditioned initial pine seedling recruitment and establishment, prevailing over the expected negative impact of salvage logging and positive impact of seeding. Seedling recruitment was sufficient to ensure natural tree regeneration after a single fire event and undermined by repeated fires. Both delaying burned timber removal during salvage logging operations and retaining immature dead trees without commercial value onsite in subsoiled stands enhanced seedling recruitment via facilitative interactions. Higher seedling growth and height under shrubs than in open ground resulted in lower aerial and root biomass, indicating elongation in response to shade, and net competition for resources. Inter-specific competition between naturally regenerated seedlings and shrubs was aggravated by intra-specific competition with neighbouring seedlings and by mechanical site preparation in subsoiled stands. All in all, post-burn increased soil fertility most likely counterbalanced the environmental stress created by fire, shifting the net outcome of plant interactions from positive (facilitation) to negative (competition). We recommend alternative post-fire management actions that decrease plant competition and take advantage of facilitation by residual burned wood, to ultimately accelerate ecosystem recovery after large stand-replacing fires.

This research aimed to estimate the splash erosion and its evolution during the first months in specific land uses after a forest fire. The study area was located in Congosto (North-West Spain), in the margins of Spanish drylands, after a wildfire occurred in May 2012, which burned 15.56 ha of scrubland and Pinus reforestation. Two different burned land uses were selected and compared to control areas: i) burned pine forest; and, scrublands. Rainfall intensity and the number, sizes and speed of raindrops were measured by an optical disdrometer and soil loss by funnels. Moreover, infiltration, soil moisture content, aggregate stability, water repellence, pH and organic matter were also measured. Results showed that the highest soil losses occurred in the burned areas, especially in the scrubland plots. The most influential factors were the presence of bare soil and the low vegetation recovery rate. Changes in soil properties did not significantly influence splash erosion, although an increase in the presence of smaller classes of aggregates could promote erosion in the scrubland. We conclude that the vegetation ecosystem restoration is the key issue to be considered after a wildfire, especially, in those types of land uses which are severely affected by the fire in the margins of drylands.

We compared the structure of the arboreal layer and the diversity and species composition of the understory vegetation of three types of mature forest communities: oak (Quercus pyrenaica) and beech (Fagus sylvatica) forests and Scots pine (Pinus sylvestris) plantations. Our main aim was to determine whether differences in these variables existed and were due to the identity of the dominant tree species. We selected four stands or replicates per forest type located geographically close and with relatively similar conditions. We found no differences in the arboreal structure of oak and beech forests, which were characterised by great variability in tree size, while in case of plantations, this variability was lower at both the intra-stand (estimated by the coefficient of variation) and inter-stand (i.e. the four replicates harboured trees of similar sizes) scales. However, the highest variability in the canopy layer of natural forests was not consistently linked to greater understory species richness. Indeed, the lowest plant species richness was found in beech forests, while oak forests harboured the highest value at either the sampling unit (per m2) or stand scales. The greatest negative correlation between plant diversity and the environmental variables measured was found for litter depth, which was the highest in beech forests. The results obtained by the CCA indicated that the four replicates of each forest type clustered together, due to the presence of characteristic species. We concluded that pine plantations did not approach the environmental conditions of native forests, as plantations were characterised by singular understory species composition and low arboreal layer variability, compared to natural woodlands.

Species rich semi-natural grasslands are disappearing across Europe, affecting invertebrate diversity negatively. In NW Spain, the recent abandonment of traditional farming practices and the gradual decrease in grazing pressures are reducing the number and extent of montane grasslands. In this context, we investigated the composition of carabid beetle (Coleoptera, Carabidae) assemblages that inhabit semi-natural grasslands situated in long-term managed oak and beech forested landscapes. According to their spatial arrangement, the studied grasslands were classified into: (1) interior or gap grasslands (small and completely surrounded by continuous forest) and (2) exterior grasslands (large and connected to a variety of habitat types). Our results indicate that, within each forested landscape, the gap and exterior grasslands harboured particular carabid assemblages (i.e. exclusive or abundantly collected species), which were also distinct from the surrounding forest carabid fauna. Dissimilarities between gap and exterior grasslands in each landscape suggest great carabid diversity at the regional scale. We also detected species-specific responses as several carabids were mainly associated with gap or exterior grasslands. Consequently, in highly modified forested landscapes, semi-natural grassland remnants may constitute great value for the protection of the carabid fauna. Specifically, we recommend conservation strategies that preserve variety in grassland features and maintain proper management activities to prevent the loss of specialised species and a decrease in regional carabid diversity.

Producción Científica, We analysed the relationship between burn severity indicators, from remote sensing and field observations, and soil properties after a wildfire in a fire-prone Mediterranean ecosystem. Our study area was a large wildfire in a Pinus pinaster forest. Burn severity from remote sensing was identified by studying immediate post-fire Land Surface Temperature (LST). We also evaluated burn severity in the field applying the Composite Burn Index (CBI) in a total of 84 plots (30 m diameter). In each plot we evaluated litter consumption, ash colour and char depth as visual indicators. We collected soil samples and pH, soil organic carbon, dry aggregate size distribution (MWD), aggregate stability and water repellency were analysed. A controlled heating of soil was also carried out in the laboratory, with soil from the control plots, to compare with the changes produced in soils affected by different severity levels in the field. Our results shown that changes in soil properties affected by wildfire were only observed in soil aggregation in the high severity situation. The laboratory-controlled heating showed that temperatures of about 300 ◦C result in a significant reduction in soil organic carbon and MWD. Furthermore, soil organic carbon showed a significant decrease when LST values increased. Char depth was the best visual indicator to show changes in soil properties (mainly physical properties) in large fires that occur in Mediterranean pine forests. We conclude that CBI and post-fire LST can be considered good indicators of soil burn severity since both indicate the impact of fire on soil properties., Ministerio de Economía y Competitividad y el Fondo Europeo de Desarrollo Regional (FEDER), en el marco del proyecto GESFIRE (AGL2013-48189-C2-1-R), Junta de Castilla y León en el marco del proyecto SEFIRECYL (LE001P17)

Quercus pyrenaica dehesas have been traditionally used as communal extensive grazing systems in the Leon province (NW Spain). In this region, recent abandonment of rural areas and the subsequent gradual decrease in livestock load have led to the invasion of shrubs in the understory, increasing the risk of fires. Indeed, even if there is no need of creating new pasturelands for livestock breeding, the remaining landowners keep on burning to clear these montane patches. Alternatively, the regional administration encourages shrub cutting as a better way of managing these areas and preserving the pasturelands. Our aim was to determine the effects of the dehesa abandonment and shrub cutting on plant species richness (annual herbs, perennial herbs and woody plants) and species composition, as well as on topsoil properties. For that, we compared three types of dehesas with different management regimes: (1) grazed dehesas (used at the present), (2) abandoned dehesas (more than 20 years without grazing) and (3) dehesas where shrub cutting was applied after abandonment (i.e. cleared dehesas). We selected three replicates or stands per dehesa type. The highest organic matter content (O.M.), total nitrogen (N) and available phosphorus (P) were found in cleared dehesas, while the lowest values corresponded to the grazed ones. Abandoned dehesas were characterized by the highest values for available calcium (Ca2+). No significant differences were detected regarding the vegetation richness values (S alpha, gamma or beta), although higher mean values of S alpha and gamma were found in grazed dehesas, and lower values in the cleared ones. Concerning the vegetation life forms, grazed dehesas held significantly greater species richness and cover of annual herbs, while abandoned dehesas had significantly higher woody species cover. Both grazed and abandoned dehesas harboured plant species (38 and 13 species, respectively), which were exclusively found in one dehesa type. Contrary to that, cleared dehesas scarcely had “exclusive” species. To conclude, our results indicated that shrub cutting alone (not followed by livestock grazing) may cause loss of plant species richness, suggesting that it is not the most appropriate management method to restore vegetation, except for reducing the risk of fire.

We aimed to study tree effects on the chemical properties of forest soils. We compared soil features of three types of forest ecosystems, each with four stands (replicates): beech forests (Fagus sylvatica), oak forests (dominated by Quercus pyrenaica) and pine plantations (Pinus sylvestris). Five samples from the top 10 cm of soil were taken per stand, from which pH, organic matter content (O.M.), total nitrogen (N) and available calcium (Ca2+), magnesium (Mg2+), potassium (K+) and sodium (Na+) were determined. Litter layer depth was measured at each soil sampling point. We also measured tree density and crown diameters at each stand. Our results indicated that soil samples from the four pine plantation stands were more similar while oak and beech stands were characterised by great variability in terms of soil properties and leaf litter depth. Although the identity of the dominant tree species significantly influenced several topsoil chemical properties (increase in pH and available cations in oak forests and higher organic matter and total nitrogen in beech and pine ecosystems), there were other important factors affecting soil features that may be taken under consideration. Differences between soil properties of the three types of forest ecosystems were mainly related to the characteristics of the litter layer and less related to the tree layer structure. Finally, the establishment of pine plantations in naturally deciduous tree areas made the topsoil features more homogeneous.

We studied the responses of carabid beetles to Pinus sylvestris ageing in four plantations aged 2–3, 10–12, 40–45 and 80 years, and one mature natural pine forest – in NW Spain. In 2003, a total of 16,866 carabid individuals (50 species) were collected using pitfall traps. Overall carabid abundance and species richness differed significantly among the five age classes with the highest values occurring in the youngest age class. The carabid assemblages of the initial stages of the ageing sequence differed considerably from the later stages that were relatively similar to each other – a consequence of differences in species dominance at specific age classes. Yet, the carabid assemblage of the 80-year-old stage did not approach that of the natural pine forest, but, unexpectedly, the 40–45-year-old age class did. Canopy cover and soil pH were the main environmental variables that affected the carabid distribution. We also detected species-level responses to the ageing process, with open habitat species more abundantly collected at the youngest stages and forest specialists at the older stages. We conclude that carabid beetles responded predictably to the pine plantation ageing process, and that although pine forests in NW Spain do not seem to provide habitat for unique species, they act as secondary habitats for forest specialist species.

The aim of this study was to analyse the regeneration of Pinus pinaster after wildfire and the possible inter and intraspecific competition during the first 3 years after fire. The study area is located in a P. pinaster stand in Leon province (NW Spain). Three study sites (S1, S2 and S3) were established in an area burned in 1998. In each site, three permanent plots (20 × 1 m) were marked. A total of 20 quadrats of 1 m 2 were studied in each plot. The number and height of pine seedlings 1, 2 and 3 years after fire was recorded in each quadrat. The regeneration of understorey vegetation in the quadrats was analysed concurrently. The significance of linear correlations among the number and height of seedlings and understorey vegetation cover was tested by calculating Pearson correlation coefficients.Seed germination and seedling emergence took place massively during the first year after the fire and decreased through time. The height growth was constant over the 3 years at site S2, while a growth burst could be observed between years 2 and 3 at sites S1 and S2. Also, pines from site S2 reached shorter maximum heights in all years compared to pines from site S1 and S3. The understorey vegetation showed minimal regeneration during the first year but then increased greatly with time. Woody understorey cover and total vegetation cover were negatively correlated with pine seedling density in sites with a high number of seedlings (e.g. S1 and S3). When woody cover, total cover and pine seedling density were low (e.g. S2), there were no correlations. There was a positive correlation between vegetation cover and the maximum height of Pinus seedlings in all study sites.

The influence of the temperature and its duration, that are among the most important components to determine the fire effects on soil properties, were studied in the 0–5 cm layer of a Humic Cambisol developed over siliceous conglomerates and under a shrub of Erica australis. Soil was sandy loam with 8.5 g 100 g− 1 of organic matter, pH of 4.7 and available P about 0.16 mg kg− 1. The water stability index (WSI) was 64.9, which was considered good. Differential thermal analysis (DTA) showed the presence of two peaks, one endothermic until 177 °C and other exothermic between 229 °C and 579 °C. Samples were heated at 100 °C, 200 °C and 500 °C during 5, 15, 30 and 60 min after reaching the selected temperature. To avoid a temperature gradient in the profile a sample layer of 2 cm depth was used. Soil heating to 100 °C at the four heating times and to 200 °C for 5 min did not produce significant changes in pH, organic matter, total N, C/N ratio, available P, extractable cations and WSI. Soils heated to 200 °C for 15, 30 and 60 min and 500 °C for 5 min, showed a significant increase in available P (from 0.9 to a maximum of 17.6 mg kg−1) and divalent cations (Ca2+ from 4.4 to 46.3 and Mg2+ from 1.5 to 8.7 mg kg− 1). For soils heated to 500 °C for 15, 30 and 60 min, a clear increase in soluble Na+ content (from 0.5 to 1.8 mg kg−1) and pH (from 5.5 to 8.1), in addition to a significant decrease in organic matter (from 8.7% to 2.4%) was detected. As a consequence an important decrease in WSI was found (from 64.9% to 54.3%).

The species composition of the plant community and the soil characteristics in Quercus pyrenaica ecosystems according to the degree of disturbance and the type of human intervention (burning, cutting, livestock grazing) were compared. Four types of oak communities were selected, each with five replicates: oak shrublands (SL), dehesas (DE) or open woodlands used for grazing, and two types of mature oak forest, one with abundant shrub biomass in the understory (FS) and the other with little shrub biomass in the understory (FO). A total of 175 species were found in the 20 sites studied, 52 appeared in a single site. The dehesas were the most different regarding species composition, with 30 species only found there. This was verified by a qualitative similarity analysis, in which the five dehesas formed a group clearly distinguishable from the other sites; the oak shrublands also formed a group, but it was not possible to distinguish between the mature oak forests with and without a shrubby understory. However, the soil characteristics were similar across all sites and differences could only be detected in organic matter and nitrogen content, which were significantly higher in the mature forests without a shrubby understory. When the plant community and soil characteristics were analysed as a whole using a canonical correspondence analysis, the separation of the dehesas was observed on the first axis, due to its greater richness and abundance in herb species, especially annuals. The other sites were ordered on the second axis, with greater differences between the oak shrublands, associated with higher shrub species cover, and the mature open forests, associated with forest herb species and a soil with a higher nitrogen, organic matter and cation exchange content. The mature forests with abundant shrub biomass were in an intermediate position. Therefore, although the differences in soil were not important and many species were common to all types of Q. pyrenaica communities, the type of human intervention did determine changes, as shown by the results of the multifactorial analyses. In addition, given that all the community types presented some species which were not found in the other types, greater biodiversity would be attained by preserving all of them.

We studied the effects of traditional forest management practices (i.e. forest exploitation activities such as burning, cutting and livestock grazing) on carabid beetle (Coleoptera, Carabidae) assemblages in Pyrenean oak forests of NW Spain. A total of 11 370 carabid individuals representing 61 species were collected by pitfall trapping from May to October 2004 in four types of traditionally managed oak ecosystems: “dehesa”, “mature open”, “mature closed” and “young”. These four management types experienced a variety of anthropogenic activities, resulting in differences in the structure and composition of the tree and understorey vegetation layers. We showed that the four management types were quite similar at the carabid assemblage level, mainly supporting open habitat and generalist species. The “dehesa” system was most distinct with a higher species richness (not significantly) and with several unique species, probably travelling from the adjacent grassland. However, many species responded significantly to the type of management, depending on the habitat associations of the species. We also found strong responses of some of the species to one type of management, either positive (exclusively collected from one management type) or negatively (completely absent). Shrub cover and soil organic matter content were the main environmental variables determining the carabid assemblage structure. At the regional scale, the four management types accounted for a high carabid beetle diversity. This diversity appears to be threatened by landscape homogenization, since traditional management practices are disappearing due to recent land-use changes in the area.

The aim is to compare the diversity of the understory in Quercus pyrenaica communities according to the type of human intervention (grazing, obtaining wood or firewood, forest fires). This interaction results in a modification of the characteristics of the arboreal layer and shrub cover. Four types of oak communities were selected, each with five replicates: communities with a high density of shrubby oak (oak shrublands), open woodlands (“dehesas”), mature oak woods with abundant woody biomass in the understory and mature oak woods with little woody biomass in the understory. In each study site, we quantified the size of the trees (height, trunk perimeter and crown diameter) and their density, woody cover in the understory and species richness as well as diversity using the Shannon index, on both a small scale (per m2) and for the total of each community. A clear difference was observed between the dehesas and the oak shrublands, the two community types with higher human intervention (the dehesas, with sustainable use for grazing and the oak shrublands, the most degraded due to repeated fires), in the principal components analysis carried out with these variables. The other two community types, considered more mature forests, presented an intermediate location on the principal components analysis. However, there was no clear relationship between the different community types and the diversity values. No differences were observed in total species richness, except that the number of annuals being significantly higher in the dehesas. Nor was it possible to detect any differences using the Shannon index, except for the oak shrublands which, although with a great variability among them, had a lower mean diversity than the other community types. The distance between trees was positively correlated to diversity, measured using the Shannon index, and to annual species richness and negatively correlated to woody cover in the understory. The variability in the distance between trees (associated with clumped distributions) was positively correlated to spatial heterogeneity, measured as Sβ. The size of the trees had very little correlation to species diversity. As a whole, the results obtained show the difficulty involved in making generalised conclusions on the effects of disturbances on plant diversity.

The aim of this study is to compare the recovery dynamics in three shrub communities subjected to experimental burning and cutting, and situated on an altitudinal gradient. Climatic features are different in each area, but all had the common characteristic of very homogeneous vegetation cover before the disturbances, with only one shrub species clearly dominant, a different taxon in each area, and with different regeneration strategies. The first area was a heathland dominated by Calluna vulgaris, situated at an altitude of 1600 m, with a continental climate (mean annual precipitation 1320 mm). The second area was a heathland dominated by Erica australis, located at an altitude of 1000 m (mean annual precipitation 840 mm). The third area was a Cistus ladanifer shrubland, located at 900 m altitude, with a Mediterranean climate similar to that of the previous area, but with lower mean annual precipitation (470 mm). Erica australis recovers by vegetative resprouting, but Cistus ladanifer is an obligate seeder, as is Calluna vulgaris in these areas. Each experimental disturbance was carried out over 100 m2 in each area. Post-fire recovery is faster in Cistus ladanifer: 2 years after burning there was 40% cover vs. less than 20% in the other two species. However, recovery after cutting was similar for Cistus ladanifer and Erica australis. Calluna vulgaris recovers very slowly, with cover values below 20% even 10 years after both disturbances. Cover of dominant shrub species is negatively correlated with cover of herbaceous species. So different recovery of dominant species lead a different community dynamic in each area.

p. 147-156 Se estudió el efecto de la reforestación con diferentes combinaciones de especies nativas en la dinámica de recuperación de un matorral dominado por Erica australis sometidos a fuego experimental. Las hierbas sembradas estuvieron muy bajo cubierta durante todo el período de estudio. Entre las especies de arbustos, Cytisus spp. se desarrolla para cubrir por encima del 50% a partir del cuarto año después de la siembra en las parcelas donde se sembró y colonización se observó en los que no sembradas desde el noveno año. Quercus pyrenaica tienen una tasa de supervivencia del 50%, pero su altura media no llega a 40 cm después de nueve años. Las especies arbustivas y herbáceas presentes en la zona antes de la quema experimental se caracterizan por su gran capacidad de recuperación, el rebrote vegetativamente o recuperándose de la semilla. Por ello no es posible detectar diferencias significativas entre las parcelas sometidas a los diferentes tratamientos de revegetación y los controles relacionados con arbolado, herbáceas o cobertura total, ni son las diferencias significativas observadas en la diversidad contada a número de especies (riqueza). El buen desarrollo de Cytisus spp. apunta a un cambio fisonómico importante y esto, junto con la alta tasa de supervivencia, aunque no el crecimiento hasta el momento, de Q. pyrenaica puede influir en la dinámica de la comunidad a largo plazo SI

This paper is part of a wider study in which different combinations of species were assayed for the revegetation of experimentally burnt heathlands. In this particular case, we determined whether there was any interaction between the dominant species, Erica australis, which recovered by vegetative resprouting, and the only successful woody species sown, Cytisus sp., eight years after fire and seven years after sowing. A detailed study was carried out on each square metre of cover and height of both species in three 160 m2 plots. Total cover exceeded 100% in all subplots sown with Cytisus, whereas it did not reach 65% in the others, when both species coexist together. There was an inverse correlation between the covers of both species and a positive correlation between the height of Erica australis and the cover and the height of Cytisus. There was no significant difference in Erica cover in plots sown with Cytisus and plots not sown. There could be some competition for light, but both species are capable of coexisting with high canopy overlap, for at least some time. Cytisus is expanding from the seeded subplots, suggesting that the dense cover of Erica australis does not impede the establishment of Cytisus.

The effects of wildfire on vegetation regeneration in communities dominated by Quercus pyrenaica and those dominated by Pinus pinaster in NW Spain were compared. In order to study changes in the composition and structure of both types of community, permanent plots were established in areas dominated by Q. pyrenaica and those dominated by P. pinaster. All were burned by wildfires at the end of summer. In each plot a permanent transect of 20 m ×1 m was established. Basal cover of the plant species present was analysed. In both types of community the global cover values generally increased throughout the study period. In the oak communities the species that appear in the first years are those that will dominate in the mature stage, like Q. pyrenaica and Erica australis. Both species are typical resprouters: from shoots on the rhizome or the stem of subterranean roots in the case of Q. pyrenaica and from lignotubers in the case of E. australis. Among the other species, herbaceous perennials dominated during the first year after the fire, Luzula lactea being the most representative. The percentage of bare soil decreased very rapidly after the first year of regeneration. However, in the P. pinaster communities the species that appeared with higher cover values during the first and second year after fire were seeders, like P. pinaster and Halimium alyssoides. Other species that appeared in these communities were Chamaespartium tridentatum, and E. australis. Amongst the herbaceous perennials, the most representative species was the Liliacea Ornithogalum umbellatum, which appeared throughout the study period in all the burned plots. The percentages of bare soil were higher than in the oak communities. Structural parameters such as diversity and specific richness were much higher in the community dominated by oak than in the pine stand. In general, regeneration after wildfire in the Pinus community was slower than in oak communities.

Erica australis heathlands in Leon province (NW Spain) have high resilience to disturbances and their post-fire recovery is very fast. The risk of soil erosion is high in the first few months after fire. The aim of this study is to investigate the effects on post-fire succession of sowing grass (Agrostis capillaris and Festuca rubra) and legume (Lotus corniculatus) seeds in a heathland burned by a summer wildfire, and to determine the most suitable native herbaceous species combination for protecting the soil in the first few phases of recovery. Fifteen permanent 4 m2 plots are established in the burned area; four treatments and a control (unsown) are applied, each with three replicates. Three similar unburned plots are also considered (unburned control). Total cover is significantly higher in the sown plots in relation to the control in the first few months after sowing, but there are no differences after 18 months. Lotus corniculatus appears only in the first year and has no effect on the total cover. F. rubra appears earlier than Agrostis capillaris, but decreases significantly in cover after 18 months. Shrub species have the highest cover in the control plots and the lowest in the Agrostis plots. The correspondence analysis shows that the trend for vegetation in all plots reaches similar species composition by the time of final sampling. The last sampling of sown plots shows greater similarity to the control plots than the sampling of these plots within the first year. The fast initial growth of F. rubra, together with its decrease and subsequent low cover from the second year, make it more preferable than Agrostis capillaris for purposes of soil protection. However, additional research, both species- and site-specific, is necessary, as different responses due to different post-fire conditions and pre-fire species composition can have important implications on community dynamics.

Shrubland responses to experimental burning, cutting and ploughing treatments were studied over 15 years in two shrubland communities dominated by Erica australis. The treatments represent the most frequent forms of anthropogenic disturbances experienced by these communities throughout their history. The response to burning and cutting treatments is similar, and the succession process is characterised as autosuccession. The highest values for herbaceous annuals and perennials were observed in the third and fourth years. Generally, herbaceous species remain present throughout the study period, while woody taxa ones increase their cover values over time. The quantity of herbaceous species present is in inverse proportion to the quantity of woody taxa. The woody species that appear immediately after treatments are sprouting species, namely Erica australis and Arctostaphylos uva-ursi. The response to ploughing is slower, reflecting the recovery mechanism (seedlings). However, after 15 years, there are no significant differences in regeneration between treatments. The first stages of this post-ploughing succession are dominated by annual species until the fourth or fifth years, after which woody species begin to dominate and herbaceous taxa decrease considerably. Woody species with high germination values are Halimium alyssoides and Halimium umbellatum. These shrubland communities have a very high resilience to such perturbations and start regenerating rapidly, reaching the original state in about 9 years. The appearance of the climax arboreal species of the area, Quercus pyrenaica, when it comes from germination, occurs 15 years after the perturbations. © 2002 Editions scientifiques et medicales Elsevier SAS. All rights reserved.

Regeneration after experimental disturbances (burning, cutting and ploughing) was studied in a heathland dominated by Calluna vulgaris (L.) Hull located in NW Spain. Regeneration of C. vulgaris was better after burning and ploughing than after cutting. When cut, this species was replaced by another resprouting ericaceous species, Erica tetralix L. Calluna seedlings suffered high mortality in the third and fourth years after all treatments. Herbaceous species, which dominated during the first year of the secondary succession, were gradually replaced by woody species characteristic of that area from the sixth and seventh years after cutting and burning, and during the tenth year after ploughing. Multivariate analysis showed a clear separation between the different treatments, reflecting different responses in the community to different disturbances and partly reflecting the vegetation status before disturbance.

The response of woody species to experimental burning, cutting andploughing was studied for a period of twelve years in a shrub community in NWSpain. The treatments represent the perturbations most frequently imposed bymanon these shrub communities throughout history. The response to burning is muchfaster than the response to cutting. The response to ploughing is slower due tothe regeneration mechanism that species use: germination. In general, thedominant species, Erica australis, influences theregeneration patterns of the rest of the species, which make up the community.There is a significant increase in the cover of woody species until the fourthyear, and of herbaceous species until the third year. Subsequently,Erica australis attains dominance, returning to itsoriginal spatial occupancy and cover values, removing the herbaceous speciesandnegatively influencing the growth of woody ones like Halimiumumbellatum, Halimium alyssoides and Quercuspyrenaica. Both Erica australis andChamaespartium tridentatum regenerated by sprouting in theburnt and cut plots, and by germination in the ploughed plot.Arctostaphylos uva-ursi only recovers after burning andploughing. Halimium alyssoides, Halimium umbellatum, Ericaumbellata and Calluna vulgaris regenerate bygermination in the three plots. Differences in cover values and spatialoccupancy during the first years of succession tend to be eliminated twelveyears after treatment and most of the species tend to recover their initialcover values. These shrubland communities have a high degree of resilience dueto the strong sprouting potential of the component species.

Recovery after cutting and burning in two series of experimental shrubland plots dominated by Cistus laurifolius and Cistus ladanifer, respectively, was studied over 11 years. The two communities tend to recover by an autosuccession process after disturbances, with Cistus species being dominant from the first or second year. The greatest diversity is recorded in the first few years after the disturbances, with higher species richness, basically herbaceous ones, and lower dominance effect. Cover by woody species tends to increase but from the fourth year the differences are not significant. The highest herbaceous cover is after one year and the peak is more marked in the cut plots. Herbaceous species cover decreases afterwards and there are small changes in the different years but without clear trends. When all the samplings are compared by a TWINSPAN, the first division separates both communities and the second division the initial and the final phases from each community. The separation between cut and burnt plots is only observed in the final phases.

The response of the woody species to experimental cutting was studied for a period of fifteen years in a shrub community of NW Spain. This treatment represents the disturbance most frequently imposed by humans on these shrub communities throughout history. The dominant species, Erica australis, influences the regeneration patterns of the rest of the species which make up the community. There is a significant increase in the cover values of the woody species until the fourth year and of the herbaceous ones until the third year. Since then Erica australis attains the spatial occupancy and cover values it originally had, removing the herbaceous species and negatively influencing the growth of some woody ones like Halimium umbellatum and H. alyssoides. Both Erica australis and Genistella tridentata sprout after cutting. Arctostaphylos uva-ursi does not recover. Halimium alyssoides, H. umbellatum. Erica umbellata and Calluna vulgaris regenerate by germination. These shrubland communities have a high degree of resilience due to the strong sprouting potential of the component species.[fr]L'étude porte sur la régénération des espèces ligneuses après coupe, sur une durée de 15 ans, dans une lande dominée par Erica australis. Ce traitement experimental est l'un des plus fréquemment utilisés dans ce type de commimautés. L'espèce dominante Erica australis agit sur les types de régénération des autres espèces. On observe un accroisement significatif des taux de couverture pour les espèces ligneuses jusqu'au 4ème. année et jusqu'au Sème, année pour les herbacées. À partir de ce moment. Erica australis retrouve les valeurs d' origine, en limitant les taux des herbacées et en diminuant la croissance de quelques espèces ligneuses comme Halimium umbellatum et H. alyssoides. La régénération par rejet est le mécanisme principal pour Erica australis comme pour Genistella tridentata. Halimium alyssoides, H. umbellatum. Erica umbellata et Calluna vulgaris se régénèrent par semences, tandis que Arctostaphylos uva-ursi ne se régénère d'aucune manière. 15 ans après la coupe, on ne note aucune difference [es]En un brezal dominado por Erica australis se ha estudiado durante un periodo de 15 años la respuesta de regeneración después del tratamiento de corta de todas las especies leñosas . Este tratamiento experimental representa uno de los más frecuentes a los que este tipo de comunidades se ve sometido. La especie dominante, Erica australis, influye sobre los patrones de regeneración del resto de las especies que componen la comunidad. Hay un incremento significativo de los valores de cobertura de las especies leñosas hasta el cuarto año y en el caso de las herbáceas hasta el tercer año. A partir de este periodo, Erica australis alcanza los valores de cobertura que presentaba en origen, desplazando a las herbáceas e influyendo negativamente en el crecimiento de algunas leñosas como Halimium umbellatum y H. alyssoides. Tanto Erica australis como Genistella tridentata emplean como mecanismos de regeneración principal el rebrote vegetativo. Arctostaphylos uva-ursi no se recupera. Halimium alyssoides, H. umbellatum. Erica umbellata y Calluna vulgaris se regeneran por germinación. A los quince años de la corta este tipo de comunidades no presenta diferencias significativas con la situación que presentaban en estado original.

The aim of this study is to compare the recovery response of Cistus ladanifer L. tothree experimental treatments in terms of seedling growth and population dynamics.A uniform area was chosen in the province of Le& oacute; n (NW Spain), in which C. ladanifer was clearly dominant with a mean cover of 70%. Three plots were established and subjected to experimental burning, cutting, and plowing in July1989. The changes in the C. ladanifer population were surveyed over 10 years (from1990 to 1999). The number of Cistus seedlings, the height of each, and the total Cistus cover percentage were recorded for every sampling period. There were no Cistus shoots from vegetative sprouting. The lowest density was recorded in the plowed plot and the highest in the burned one, as was expected from a species whose germination is stimulated by heat; ten years after treatments, density in the burned plot is still significantly higher. A tendency towards stabilization in cover was observed in the three plots, with the highest ...

Changes produced in runoff and sediment levels before and after fire and during the revegetation process were examined using a rainfall simulator. The area was burned in an experimental fire, reaching temperatures from 35° to 563° C. Then it was revegetated using different species combinations. Fifteen permanent plots were established in the burnt area (4 treatments and a control replicated three times). Simulated rainfall of 15 mm per 5 min was applied in each treatment. No significant differences were found in sediment yield and runoff between treatments, but greatest runoff was observed to occur immediately after the fire. A significant relationship was found between runoff and woody cover, and a decrease in runoff can be observed as cover increases. The relationship between sediment yields and runoff rates was also positive. The low rates observed during rainfall simulation are due to the effect of natural vegetation rather than revegetation treatments. The high organic matter content also had an infl...

Arctostaphylos uva-ursi uses vegetative resprouting to recover rapidly after disturbances. This study aims to widen knowledge of its regeneration response, so it was subjected to experimental cutting and burning. Fifteen pairs of small circular plots (50 cm diameter) were situated at random in an area where this species is abundant and forms homogeneous carpets with close to 100% cover. One plot of each pair was burned and the other one was cut. Initial biomass was estimated as dry weight from the cut plots. A 50 cm diameter circular sampling quadrat, divided into two concentric circles, was used in order to determine cover recovery and the way in which this occurred (predominantly by colonization from outside or uniformly over the whole surface). Initial recovery was very fast after both disturbances, exceeding 30% cover from the fourth month. Recovery of aboveground biomass was also similar on comparing both types of disturbance, but statistically significant differences with respect to initial values were detected.

The germination capacity of Quercus pyrenaica seeds subjected to different temperatures (60°C, 100°C and 150°C for 1 and 5 minutes) and mechanical scarification was studied. Germination increased after mechanical scarification and heat treatment at 60°C for 1 minute. Germination percentages for the rest of the treatments were lower than those for the control, but statistically significant differences (p < 0.05) were only observed between 150°C for 5 minutes and the other treatments (except for 150°C for 1 minute). These results show that seed germination of Quercus pyrenaica would not be affected by soil temperatures reached during a low intensity fire or by the action of agents which can mechanically damage the external coat.

The response of Erica australis to experimental burning, cutting and ploughing treatments was studied in two heathland communities where it was dominant. The treatments represent those most frequently originated by humans on these heathland communities throughout history. The response of this species in a community where it is dominant and there is no strong interspecific competition was also compared to that produced by it in a community where there is competition. It can be observed that the response to burning and cutting treatments is very similar with very fast spatial occupation in the first few years. From the point of view of time cover values increased in a pronounced manner during the first few years and this increase was stabilized from the fourth year. However, from this moment on a greater increase in this species' maximum height is evident. The response to ploughing is slower according to recovery mechanism (seedlings). Recovery is comparatively less in the area where there is no strong competition than in that where it exists between species. Resume Dans deux communautes de bruyere dominees par Erica australis on a etudie la reponse de cette espece aux traitements experimentaux de brulage, coupe et labour. Ces traitements representent les actions les plus frequentes que l'homme a exerce sur ces communautes de bruyere tout au long de l'histoire. De la meme facon, on a fait la comparaison de la reponse de cette espece quand elle se trouve dans une communaute dominee principalement par elle, ou elle n'y a pas une forte competition entre les especes, avec la reponse quand elle se situe dans une communaute ou plusieurs especes coexistent. On observe que la reponse aux traitements de brulage et coupe est tres semblable, en presentant une occupation spatiale tres rapide pendant les premieres annees. Du point de vue temporel, leurs valeurs de couverture augmentent de facon plus prononcee pendant les premieres annees, et c'est a partir de la quatrieme annee que ce developpement se stabilise. Cependant, c'est a partir de ce moment la qu'on remarque une augmentation plus grande en ce qui concerne la hauteur maximale de cette espece. La reponse au traitement de labour est plus lente en relation avec la regeneration par semences. L'effet de la competition se traduit par une recuperation qui suit un mode d'augmentation oppose a la situation originaire. Dans la surface ou il n'existe pas une forte competition, la recuperation est comparativement plus faible que dans la station ou il y existait une competition entre les especes. Mots cles: Maquis, Mecanismes reproductives, Perturbations experimentales, Regeneration, Rejets

P. 331-339 Se muestrearon ecosistemas dominados por Quercus pyrenaica desde poco tiempo después de haberse quemado hasta 5 años tras el incendio. Se comparó la composición florística con la anterior al fuego, si se disponía de datos, o con el óptimo climácico, en caso contrario. En dos de las zonas, las mejor conservadas antes del incendio, se observa, ya desde los primeros muestreos, una composición específica semejante a la de zonas similares no quemadas. En las zonas previamente más degradadas, se aprecia un aumento de especies leñosas no arbóreas, indicando la tendencia a la sustitución del bosque primitivo por formaciones de matorral NO

Recovery after experimental burning and cutting in a shrubland of Cistus laurifolius in NW Spain has been studied. The community was homogeneous prior to the disturbances, and tended to recover through a process of autosuccession. It was tested whether in a small space (two 100 m2 plots) there was a greater similarity among individual subplots (12) in five consecutive years, or among the five subplots considered in each plot in the same year. By comparing space and time beta diversity using analysis of variance, no significant differences were observed, which indicates that temporal changes are not of a greater magnitude than space heterogeneity, even on such a small scale. Changes in time are characterized by an increase in cover by woody species, mainly Cistus laurifolius, or a decrease in the diversity and richness of species. Space heterogeneity (differences between subplots) does not seem to be determined by environmental gradients, since the sampling surface is very small, and may be due to the effect of some annual or perennial species, which are not dominant and only appear in some subplots, probably due to random dispersal.

Mediterranean forests are especially prone to fire, a periodic disturbance that affects all the ecosystem components in different ways. Gathering knowledge on the particular responses and rate of recovery of multiple ecosystem components following a wildfire is crucial to reliably evaluate its consequences on biodiversity. Using eight sampling transects, we studied the changes in four ecosystem components (topsoil, plants, carabids, and staphylinids) during three years after a spring wildfire in a Quercus pyrenaica forest; and compared them with the surrounding unburnt forest (hereafter control). We found great variety of responses to fire suggesting each component may deal with this recurring disturbance via different adaptations, and that the time spent to recover to pre-disturbance conditions depends on the group of focus. Topsoil characteristics were highly variable and minor differences were found between burnt and control transects. Plant community was considerably affected by fire but rapidly recovered exceeding the control forest in species richness and cover, partly due to proliferation of annual herbs. However, plant species composition differed between burnt and control forests during the whole study period. Carabid beetles were more abundant and richer in species in the burnt forest, thanks to the arrival of seed predators favoured by post-fire drier and warmer conditions. Staphylinid beetle composition differed between control and burnt transects during the whole period, although their abundance was strongly variable. Distinct post-fire plant, carabid and staphylinid species composition suggests scattered low-intensity wildfires in this region may help to maintain habitat heterogeneity benefiting biodiversity at the landscape scale. Mediterranean forests are especially prone to fire, a periodic disturbance that affects all the ecosystem components in different ways. Gathering knowledge on the particular responses and rate of recovery of multiple ecosystem components following a wildfire is crucial to reliably evaluate its consequences on biodiversity. Using eight sampling transects, we studied the changes in four ecosystem components (topsoil, plants, carabids, and staphylinids) during three years after a spring wildfire in a Quercus pyrenaica forest; and compared them with the surrounding unburnt forest (hereafter control). We found great variety of responses to fire suggesting each component may deal with this recurring disturbance via different adaptations, and that the time spent to recover to pre-disturbance conditions depends on the group of focus. Topsoil characteristics were highly variable and minor differences were found between burnt and control transects. Plant community was considerably affected by fire but rapidly recovered exceeding the control forest in species richness and cover, partly due to proliferation of annual herbs. However, plant species composition differed between burnt and control forests during the whole study period. Carabid beetles were more abundant and richer in species in the burnt forest, thanks to the arrival of seed predators favoured by post-fire drier and warmer conditions. Staphylinid beetle composition differed between control and burnt transects during the whole period, although their abundance was strongly variable. Distinct post-fire plant, carabid and staphylinid species composition suggests scattered low-intensity wildfires in this region may help to maintain habitat heterogeneity benefiting biodiversity at the landscape scale.

Traditional management practiced over centuries in Mediterranean cultural landscapes has led to singular agrosilvopastoral ecosystems such as dehesas. Recent abandonment of dehesa management has resulted in shrub encroachment, habitat homogenisation and increased fire risk. Mechanical shrub cutting to decrease biomass load creates novel cleared dehesas with yet unknown consequences for the ecosystem function. We investigated the effects of these land use changes on ground dwelling beetles (carabids and staphylinids) as model organisms by comparing traditionally grazed, long-time abandoned and newly cleared dehesas. Land use changes affected beetle species composition by altering habitat structure (e.g., litter layer) and the availability of feeding resources. Grazed dehesas held the highest number of exclusive species and particular functional guilds of carabid seed eaters and staphylinid coprophiles, utilizing food resources related to the presence of grazing livestock (annual herbs and coprophagous insects). Beetle assemblages of abandoned dehesas, resembling those known from surrounding human disturbed oak forests, exhibited the lowest abundance and greatly differed from beetle assemblages of grazed dehesas. Shrub clearance after dehesa abandonment benefited opportunistic beetle predators feeding on decomposers associated with cutting slash left on the ground. The habitat structure and beetle species composition of cleared dehesas slightly approached those of grazed dehesas, therefore suggesting shrub cutting as a first step towards restoration of abandoned dehesas. However, since livestock grazing is an essential driver of ground dwelling beetle composition, it should be promoted after shrub cutting in cleared dehesas to restore the characteristic assemblages, species interactions and ecosystem function of grazed dehesas. Traditional management practiced over centuries in Mediterranean cultural landscapes has led to singular agrosilvopastoral ecosystems such as dehesas. Recent abandonment of dehesa management has resulted in shrub encroachment, habitat homogenisation and increased fire risk. Mechanical shrub cutting to decrease biomass load creates novel cleared dehesas with yet unknown consequences for the ecosystem function. We investigated the effects of these land use changes on ground dwelling beetles (carabids and staphylinids) as model organisms by comparing traditionally grazed, long-time abandoned and newly cleared dehesas. Land use changes affected beetle species composition by altering habitat structure (e.g., litter layer) and the availability of feeding resources. Grazed dehesas held the highest number of exclusive species and particular functional guilds of carabid seed eaters and staphylinid coprophiles, utilizing food resources related to the presence of grazing livestock (annual herbs and coprophagous insects). Beetle assemblages of abandoned dehesas, resembling those known from surrounding human disturbed oak forests, exhibited the lowest abundance and greatly differed from beetle assemblages of grazed dehesas. Shrub clearance after dehesa abandonment benefited opportunistic beetle predators feeding on decomposers associated with cutting slash left on the ground. The habitat structure and beetle species composition of cleared dehesas slightly approached those of grazed dehesas, therefore suggesting shrub cutting as a first step towards restoration of abandoned dehesas. However, since livestock grazing is an essential driver of ground dwelling beetle composition, it should be promoted after shrub cutting in cleared dehesas to restore the characteristic assemblages, species interactions and ecosystem function of grazed dehesas

Changes in the chemical characteristics of soil and postfire plant succession were studied in eight oak (Quercus pyrenaica) ecosystems in the Province of Leon (NW Spain) during the first 3 years following the fire. An increase in organic matter, C/N ratio, available K, and P resulting from the fire was observed. It was also observed that with time, these parameters tended to decrease. However, there is a great difference in values in sites with the same regeneration age (e.g., 925–975 kg ha‐1 of available K 1 month following the fire, but 225–935 kg ha‐1 2 years following the fire). It was therefore appropriate to compare the values for each site in successive years. A study into the relationship between vegetation and the edaphic conditions by canonical correspondence analysis shows the importance of initial conditions, given that the regeneration process is an autosuccession.

The aim of this study was to define the species richness patterns over a period of 15 years during the vegetation recovery process after disturbances (burning, cutting and ploughing) in heathlands. Three communities were selected: two dominated byErica australisand one dominated byCalluna vulgaris. The alpha and gamma diversity patterns were site specific and influenced by the ecological traits of dominant shrub species. The shrubland dominated byErica australis, typical resprouters with a fast regeneration, showed the highest values of alpha and gamma diversity during the first 7 years of regeneration. The heathland dominated byCalluna vulgaris, an obligate seeder, had a contrasting pattern of alpha and gamma diversity, as the highest values appeared from year 7 until year 14. Thus, the speed of regeneration of the dominant shrub species could be the main factor affecting structural parameters in these communities. Species richness patterns did not vary in relation to the different types of perturbation. Cutting and burning would be the most suitable forestry management strategies to conserveErica australisheathlands, but burning is more appropriate inCalluna vulgarisones because cutting modified this community.

This chapter analyzes the post-fire regeneration of Mediterranean broadleaved forests, the factors that may constrain this process and the best alternatives to improve the structure and dynamics of these forests after fire. Most Mediterranean broadleaved species share in common their ability to resprout from a protected bud bank after disturbances such as fire. Yet, this ability may vary depending on the species considered, the intensity and recurrence of fire events, the quality of the site and some individual characteristics (e.g. plant size). Even though resprouting after fire assures a rapid recovery of the vegetation cover and other crucial processes and ecosystem services, these young and dense forests with multi-stemmed resprouted individuals may not fit the modern socioeconomic demands and may even become very sensitive to the spread of new fires. Therefore, a selective thinning of resprouts, retaining the larger and dominant ones, has been recommended. This management alternative has been shown to increase growth rates of retained resprouts, to raise the forest canopy and to encourage sexual reproduction. Nevertheless, attention must be paid to the new wave of resprouts that may appear after thinning. In this chapter we analyze the main constrains that affect the natural regeneration of Mediterranean broadleaved forests after fire and the best alternatives to manage natural regeneration arisen through resprouting in these areas.

Regeneration response after prescribed burning, cutting and uprooting in experimental heatland plots dominated by Erica autralis subsp. aragonensis , was studied. The highest percentage cover of annual species was observed two years after the treatment. From that moment the therophytes tended to decrease and were replaced by perennial species natural to the community. The temporal heterogeneity calculated shows the greatest changes in the initial stages. Regeneration was by an autosuccession process, slower in the case of the uprooted plots due to the greatest impact.

Cytisus scoparius and Genista florida regenerate after fire by stump-sprouting but also by seed. Seeds of these species were heated to a range of temperatures similar to those registered on the surface soil during natural fires (from 50 to 150 °C) and a range of exposure times (from 1 to 15 min). No germination was observed at high temperatures, ≥130 °C, when the exposure time was 5 min or more. However, moderate heat treatments (at 70 and 100 °C) significantly increased the rate of germination relative to controls. Cytisus scoparius is more favoured by fire action than Genista florida, with germination rates slightly greater following 100 °C for 5 min and 130 °C for 1 min than after mechanical scarification.

We investigated the responses of carabid beetles to habitat type at the local scale in traditionally managed “dehesa” ecosystems in NW Spain. The beetles were sampled from two habitat types (central grassland and surrounding forested zone) of five “dehesa” ecosystems, from May to October 2004. Atotal of 4,374 carabid individuals and 55 species were captured using pitfall trapping. Most of the species were collected from both habitat types, probably due to open spaces created between old-growth trees in the forested zone. Differences in carabid assemblage composition were found mainly due to Harpalus species characteristic from the central grassland and a few forest specialist species exclusively found in the forested zone. The maintenance of the “dehesa” structure may be of importance for carabid species adapted to the variety of habitats created, and requires the continuation of traditional management practices.

p. 161-166 Se analizan muestras de suelo recogidas antes y después de un fuego experimental en un brezal en la provincia de León (España). Los bancos de semillas fueron evaluados para contar los números de plántulas que aparecen de Erica australis y Calluna vulgaris. Un total de 2.285 semillas viables / m2 antes de grabar y 1177 semillas viables / m2 después del incendio fueron estimados para Erica australis, y 90 y 690 semillas viables / m2, respectivamente, de Calluna vulgaris. Después del incendio el número de semillas viables / m2 de Erica australis habían disminuido, mientras que hubo un aumento considerable en el número de germinable semillas / m2 de Calluna vulgaris. Ni plantones ni brotes de Calluna vulgaris había aparecido en las parcelas 10 meses después del incendio. Erica australis se recuperaron principalmente por brotes después del fuego SI

p. 441-447 Quercus pyrenaica es una especie de roble de amplia distribución en la Península Ibérica, que ha sido objeto de alteraciones drásticas, tales como el fuego, llevando a una disminución significativa en su cubierta. El objetivo principal de este estudio fue realizar un comparativo análisis de la regeneración post-incendio de dos ecosistemas de Quercus pyrenaica. Antes de ser quemado por un incendio forestal al final del verano en 1985, el primer ecosistema presenta un estrato arbóreo desarrollado, mientras que la segunda fue en una etapa estrato arbustivo. En cada ecosistema una parcela permanente se estableció y se tomaron muestras para un período de 6 años después de la perturbación. Las tasas de colonización de diferente biológica Se estimaron los tipos, así como los parámetros estructurales que definen la comunidad: la diversidad de especies, riqueza y uniformidad. Estos resultados nos permitieron determinar un modelo de sucesión post-incendio para estos ecosistemas. La composición de especies de post- fuego de los dos sitios fue similar, pero la abundancia de especies particulares variar como una función de la abundancia pre-fuego SI

The interactions between the trees and the herbaceous community near them are multiple and complex (1, 2, 4). The objective of this work was to determine the manner in which these interactions affect the structure of the herbaceous community and whether this effect can be described as a function of distance from the trees and of the orientation.

The tree vegetation formations have been subjected to numerous recurring fires which cause important change in the structure and compossition of the vetetation. The degree of fire action on vegetation mainly depends on the time of year, since it conditions extrinsic factors to the tree stand like climate, and intrinsic factors such as vegetation humidity, the accumulation of combustible material and so on… (6). The response of the vegetation is expected to differ because the vegetation is at different phenological stages which condition its capacity to regenerate, either from stump sprouting, seed germination or both processes together (1, 3, 5). The aim of this paper is to compare regeneration response in Ouercus pyrenaica tree masses burnt by natural fires in spring and summer.

The aim of this study was to determine the effect of fire recurrence on the structural characteristics, in particular biodiversity, of different communities in Sanabria Natural Park (Castilla y Leon Region, Spain). Fourteen sites, ten Erica australis heathlands and four Quercus pyrenaica stands, two mature oak forests and two oak shrublands, were chosen. All of them had different levels of fire recurrence and different ages since the last fire. Data on fires occurring in the study area since 1990 are available. Sampling was carried out in July 2005. A 10 x 10 m plot was located in the centre of each site; in each plot, ten 1m 2 quadrats were studied and all the species present were quantified as visual cover percentage. A sampling by layers was also carried out in the same quadrats, estimating total plant cover in each layer. Plant species diversity was measured as richness (number of species). Alpha diversity (diversity/m 2 ), gamma diversity (diversity/plot), and beta or pattern diversity (S beta = S gamma / mean S alpha) were analysed. Structural diversity was calculated by the Shannon index, using plant cover data in the different layers. An affinity analysis was carried out considering all the species present. The dendrogram showed two groups: Erica australis heathlands and Quercus pyrenaica oak stands. The effect of fire recurrence on species composition was not observed in either case. A PCA was carried out in order to determine whether recurrence or the time elapsed since the last fire had any effect on species diversity or community structural diversity. Differentiation between the oak stands and the heathlands was also observed in this case. There was higher herbaceous species richness and more structural diversity in the oak stands. Stratification was noticeably lower in the heathlands, although they usually had higher woody species richness. No ordination depending on the time elapsed since the previous fire or recurrence was observed. Therefore, changes in community structure caused by fire recurrence in a relatively short period, such as that considered (15 years), are not noticeable in areas adapted to frequent fires. Nevertheless, repeated fire impedes the progress of succession and slows down its initial immature stages. These recover by autosuccession following repeated fire and persist as heathlands or oak shrublands. Although fires occur in mature oak forests, only the understory is affected, thus maintaining greater diversity and structural complexity.

The first phases of regeneration of two Cistus species (Cistus laurifolius and Cistus ladanfer) are compared in experimental plots that were subjected to different treatments: cutting and burning. In both treatments the parameters used were: seedling number, height and cover. Differences between their rowth are discussed and compared with that of Erica australis subsp. aragonensis, that can resprout vegetatively.