Landscape Implications of Contemporary Abandonment of Extensive Sheep Grazing in a Globally Important Agricultural Heritage System

[EN], In Southern Europe, the abandonment of the traditional transhumant system where sheep graze lowland areas during winter and distant mountain systems during summer has led to an important cultural loss and still poorly understood ecological consequences. We investigate the landscape-scale implications of contemporary sheep grazing patterns in a Globally Important Agricultural Heritage System (GIAHS). Our analysis showed a heterogeneous use of mountain grazing areas between 1990 and 2020. The areas most used by sheep had more abundance of pasture, fewer forests, and structurally different landscapes than those that had been fully abandoned by sheep. Likewise, we have detected decreasing trends in landscape diversity in those areas not used by sheep over the study period, whereas landscape heterogeneity is maintained in those areas grazed by sheep. Our study constitutes an original analysis of landscape patterns and shifts in relation to extensive sheep grazing by using novel approaches that combine interviews, updated satellite time series, and state-of-the-art landscape analysis techniques. Likewise, our results constitute a benchmark as they inform on the importance of preserving extensive sheep grazing if we aim to maintain the cultural heritage, and traditional diverse landscape and the semi-natural grasslands in the Mountains of León.SIEuropean Union Next-Generation EU fundsCESEFORMAP

Short-term effects of nitrogen deposition on soil microbial biomass in Calluna heathlands NW Spain: critical loads

[EN] We evaluate the short-term effects of different N deposition loads on nutrient dynamic of soil microbial biomass in Cantabrian heathlands. A surplus of 10 kg N ha-1 yr-1 above N background deposition was required to increase soil microbial biomass N content in old Calluna heathlands, while a surplus of 20 kg N ha-1 yr-1 was required in young ones. The increase of atmospheric N deposition showed no change in soil microbial biomass C content. This caused a decrease in C:N ratio with the highest N deposition loads, being linked to a bacterial biomass dominance against fungal dominanceS

Fuel build-up promotes an increase in fire severity of reburned areas in fire-prone ecosystems of the western Mediterranean Basin

​​​​​​​Fire Ecology is the official journal of the Association for Fire Ecology[EN] Background Fire‑vegetation feedbacks can modulate the global change effects conducive to extreme fire behavior and high fire severity of subsequent wildfires in reburn areas by altering the composition, flammability traits, and spatial arrangement of fuels. Repeated, high‑severity wildfires at short return intervals may trigger long‑term vegetation state transitions. However, empirical evidence about these feedbacks is absent in fire‑prone ecosystems of the west‑ern Mediterranean Basin, where the response of fire activity has been enhanced by contemporary socioeconomic and land‑use changes. Here, we evaluated whether fire severity differs between initial burns and subsequent wild‑fires in reburn areas (fire‑free periods = 10–15 years) of maritime pine and Aleppo pine forests, holm oak woodlands, and shrublands in the western Mediterranean Basin, and whether there is a relationship between the severity of such interactive wildfire disturbances. We also tested how the type of ecosystem and changes in vegetation structure after the initial wildfires influence these relationships. We leveraged Landsat‑based fire severity estimates for initial and last wildfires using the Relativized Burn Ratio (RBR) and Light Detection and Ranging (LiDAR) data acquired before the last wildfire. Results Fire severity of the last wildfire was significantly higher than that of the initial wildfire for each dominant ecosystem type in reburn areas. These differences were very pronounced in maritime pine forests and shrublands. For consistency, the same patterns were evidenced for the fire severity in reburn and first‑entry areas of the last wild‑fire for each dominant ecosystem type. Fire severity of the last wildfire in forests and woodlands (particularly maritime pine‑dominated) raised with increasing severity of the previous wildfire to a greater extent than in shrublands. Pre‑fire fuel density in the lower vegetation strata (up to 4 m high in maritime and Aleppo pine forests, as well as in shrub‑lands, and up to 2 m high in holm oak forests) was significantly higher in reburn than in first‑entry areas of the last wildfire. Conclusions Our results suggest that land managers should promote more fire‑resistant landscapes to high fire severity by minimizing fuel build‑up and thus fire hazard through pre‑fire fuel reduction treatments such as pre‑scribed burning[ES] Antecedentes La retroalimentación entre el fuego y la vegetación puede modular los efectos del cambio global que conducen al comportamiento extremo del fuego y a una alta severidad de fuegos subsiguientes en áreas de interacción entre incendios. Esto se puede producir mediante alteraciones en la composición, características de inflamabilidad, y la disposición espacial del combustible. Los incendios repetidos, de alta severidad en intervalos de tiempo cortos, pueden producir transiciones a largo plazo sobre el estado de la vegetación. Sin embargo, la evidencia empírica sobre estas retroalimentaciones está ausente en los ecosistemas propensos al fuego en la cuenca oeste del Mediterráneo, donde la respuesta a la actividad del fuego ha aumentado por las actividades socioeconómicas y el cambio en los usos del suelo. En este trabajo, evaluamos si la severidad del fuego difiere entre incendios iniciales y subsiguientes en áreas con fuegos recurrentes (período libre de incendios de 10–15 años), en bosques de pino marítimo y pino de Alepo, en bosques de encinas y en matorrales de la cuenca oeste del Mediterráneo, y si existe una relación entre la severidad de estas perturbaciones interactivas. Testeamos asimismo cómo el tipo de ecosistema y cambios en la estructura de la vegetación después de los incendios iniciales influencian esas relaciones. Potenciamos las estimaciones de severidad basadas en LANDSAT para los incendios iniciales y finales, usando el Ratio Relativo a de Quema (Relativized Burn Ratio o RBR en inglés), y datos LIDAR adquiridos antes del último incendio. Resultados La severidad del último incendio fue significativamente más alta que la del fuego inicial para cada tipo de ecosistema dominante en áreas de interacción de incendios. Estas diferencias fueron muy pronunciadas en bosques de pino marítimo y en matorrales. Consistentemente, los mismos patrones fueron evidenciados para la severidad de los incendios en áreas de interacción de incendios y en aquellas en que el fuego entró por vez primera durante el último incendio para cada tipo de ecosistema. La severidad del último incendio en bosques (particularmente los dominados por pino marítimo) aumentó con una la severidad del incendio anterior en mayor grado que en matorrales. La densidad del combustible preincendio en los estratos de vegetación bajos (hasta 4 m de altura en bosques de pino marítimo y de Alepo, como también en matorrales, y hasta 2 m de altura en bosques de encinas), fueron también significativamente más altos en las zonas de interacción de incendios que en la primera entrada del fuego durante el último incendio. Conclusiones Nuestros resultados sugieren que los gestores del territorio deben promover paisajes más resistentes a la alta severidad, minimizando el aumento de la carga de combustible y por lo tanto el riesgo de incendio, mediante tratamientos de reducción del combustible, como por ejemplo quemas prescriptasSIThis study was fnancially supported by the Spanish Ministry of Science and Innovation in the framework of LANDSUSFIRE project (PID2022-139156OBC21) within the National Program for the Promotion of Scientifc-Technical Research (2021-2023), and with Next-Generation Funds of the European Union (EU) in the framework of the FIREMAP project (TED2021-130925B-I00); by the Regional Government of Castile and León in the framework of the IA-FIREXTCyL project (LE081P23); and by the Portuguese Foundation for Science and Technology in the frame of project UIDB/04033/2020. José Manuel Fernández-Guisuraga was supported by a Ramón Areces Foundation postdoctoral fellowshi

The seed bank in Pinus stand regeneration in NW Spain after wildfire

P. 22-31In the Cantabrian area (northwest Spain) Pinus stands occupy many of the original shrub communities that have been considered unproductive. These Pinus stands represent the vegetation which is most affected by fire. Regeneration after fire may occur in different ways: by resprouting or by germination or both. Germination was the only regeneration mechanism in Pinus species that appeared in these areas. The aim of this study is to determine the role of the soil seed bank in regeneration in this type of ecosystem. In order to carry out the study, three communities dominated by Pinus sylvestris which had suffered wildfires were chosen. In each of the three experimental sites of Pinus sylvestris stands the seed bank composition and above-ground vegetation were studied. The results allowed three species groups in the seed bank to be differentiated: those favoured by fire, amongst which some hardseeds, mainly belonging to Cistaceae and Leguminosae, were found; another group formed by outsider or opportunist species from outside the community and which used anemochory as their main dispersion mechanism; and the third group formed by those negatively affected, amongst which were species using vegetative resprout as the main regeneration mechanism. The species of greatest quantitative importance in the seed bank was Erica australis. In general, anemochorous species were predominant in the soil seed bank. During the first stages of succession chamaephytes were dominant and in the two years after fire therophytes were. No great similarity was observed between the bank composition and field vegetation from a qualitative viewpoint, due to differences in the presence of seeds of outsider plants in the bank and to the significance of the resprouting species in the field.S

Influence of high temperatures on seed germination of a special Pinus pinaster stand adapted to frequent fires

P. 129–136This study examines the effect of fire on the germination of Pinus pinaster seeds from a population with special adaptations to this type of disturbance, due to the high frequency of fires to which they have been subjected. The action of fire was simulated in the laboratory using thermal shocks. Temperatures of 60, 90, 120, 200 and 300 °C were used for exposure times of 1 and 5 min. The viability of seeds of this species from the soil seed bank of a population subjected to a wildfire was also evaluated. The results show that germination is not increase by a thermal treatment. The effect is negative at temperatures above 90 °C and exposure times of 1 min with a significant decrease in, or even no, germination. Therefore the seeds cannot stand high temperatures and reproductive effort is placed on serotinous cone development and the production of high numbers of seeds. The high viability of the seeds from the area burned by wildfire, immediately after the fire and 1 year later, show the high potential of the soil seed bank to contribute to the regeneration of the burned area

Soil-plant relationship in Calluna heathlands after experimental burning and nitrogen fertilization, studies from NW Spain

[EN] We studied changes in the relationship between soil nutrient content and plant species richness in Calluna heathlands after seven years of experimental burning (B) and nitrogen fertilization (NF). Our results indicate that both the treatments (B, NF, B+NF) and modification of several soil characteristics (total N, available Na, and C:N ratio) reflected in a significant increase in plant species richnessS

Disruption of trophic interactions involving the heather beetle by atmospheric nitrogen deposition

P. 436-445Elevated nitrogen (N) deposition impacts the structure and functioning of heathland ecosystems across Europe. Calluna plants under high N-inputs are very sensitive to secondary stress factors, including defoliation attacks by the heather beetle. These attacks result in serious damage or death of Calluna, its rapid replacement by grasses, and the subsequent loss of heathland. We know very little about the mechanisms that control the populations and trigger outbreaks of the heather beetle, impeding proper management measures to mitigate the damage. We investigated the effects of N deposition on the relationships between the heather beetle, its host plant, and two arthropod predators at building (rejuvenated through fire) and mature heathlands. The study combines field manipulation experiments simulating a range of N deposition rates (0, 1, 2, 5 g N m−2 year−1 for 2 years, and 5.6 g N m−2 year−1 for 10 years), and food-choice laboratory experiments testing the preferences of adults and larvae of the heather beetle for N-treated Calluna plants, and the preferences of predators for larvae grown on plants with different N-content. The larvae of the heather beetle achieved the highest abundances after the long-term (10-year) addition of N at mature Calluna plots in the field. Contrary to the adults, the larvae foraged preferentially on the most N-rich Calluna shoots under laboratory conditions. Predators showed no aggregative numerical responses to the accumulation of heather beetle larvae at high N-input experimental plots. During the feeding trials, predators consumed a small number of larvae, both in total and per individual, and systematically avoided eating the larvae reared on high-N Calluna shoots. Our study showed that the most severe defoliation damage by the heather beetle is inflicted at the larval stage under prolonged availability of high-N inputs, and that arthropod predators might not act as effective regulators of the beetle's populations.S

Plant and vegetation functional responses to cumulative high nitrogen deposition in rear-edge heathlands

P. 980-990Elevated atmospheric nitrogen (N) deposition is a major driver of change, altering the structure/functioning of nutrient-poor Calluna vulgaris-heathlands over Europe. These effects amply proven for north-western/central heathlands may, however, vary across the ecosystem's distribution, especially at the range limits, as heathlands are highly vulnerable to land-use changes combined with present climate change. This is an often overlooked and greatly understudied aspect of the ecology of heathlands facing global change. We investigated the effects of five N-fertilisation treatments simulating a range of N deposition rates (0, 10, 20, and 50 kg N ha−1 yr−1 for 1 year; and 56 kg N ha−1 yr−1 for 9 years) on the Calluna-plants, the plant functional groups, species composition and richness of two life-cycle stages (building/young- and mature-phase) of Calluna-heathlands at their rear-edge limit. Our findings revealed a dose-related response of the shoot length and number of flowers of young and mature Calluna-plants to the addition of N, adhering to the findings from other heathland locations. However, cumulative high-N loading reduced the annual growth and flowering of young plants, showing early signs of N saturation. The different plant functional groups showed contrasting responses to the cumulative addition of N: annual/perennial forbs and annual graminoids increased with quite low values; perennial graminoids were rather abundant in young heathlands but only slightly augmented in mature ones; while bryophytes and lichens strongly declined at the two heathland life-cycle stages. Meanwhile there were no significant N-driven changes in plant species composition and richness. Our results demonstrated that Calluna-heathlands at their low-latitude distribution limit are moderately resistant to cumulative high-N loading. As north-western/central European heathlands under high-N inputs broadly experienced the loss of plant diversity and pronounced changes in plant species dominance, rear-edge locations may be of critical importance to unravel the mechanisms of heathland resilience to future global change.S

Influence du feu sur le stock de semences dans le sol d’une forêt de Quercus faginea du Nord-Ouest de l’Espagne

Formerly Annales des Sciences Forestières[EN] A study was carried out on the effect of a fire on the seed bank of a Quercus faginea forest situated close to the town of Palencia (NW Spain). Soil samples were taken at two depths: upper layer at 0-2 cm and deeper at 2-5 cm, in a burned area and in one nearby which did not suffer from the fire. The specific richness values, obtained 2 years after the fire, in samplings carried out in the field as well as the soil seed bank were higher in the burned area than the control. The number of germinated seeds was also higher in the burnt area than the control and more abundant in the surface stratum than the deeper one in both areas. In the control area the richness was 33 species, while in the burned area the richness was greater by five species. On the other hand, the cover value was 58 % in the burned area and 61 % in the control area[FR] On a étudié l’effet d’un incendie sur le stock de semences d’une forêt de Quercus faginea située à Palencia (NW de l’Espagne). Pour atteindre cet objectif, on a pris deux séries d’échantillons du sol respectivement à deux niveaux de profondeur : 0-2 cm et 2,5 cm dans une zone brûlée et dans une zone avoisinante non incendiée. Deux ans après l’incendie, la présence des espèces, aussi bien dans les échantillons prélevés sur le terrain que dans le stock de semences du sol, était plus importante dans la zone brûlée que dans la zone témoin. Le nombre de semences ayant germé était plus élevé dans la zone brûlée que dans la zone témoin et aussi plus important dans la strate superficielle que dans la strate profonde des deux zones. Dans la zone témoin, on a identifié 33 espèces, contre 38 espèces dans la zone brûlée. Par ailleurs le couvert était de 58 % dans la zone brûlée et de 61 % dans la zone témoinSIUniversity of Valladolid supported the production of this wor

The footprint of large wildfires on the multifunctionality of fire-prone pine ecosystems is driven by the interaction of fire regime attributes

[EN], Background Mediterranean ecosystems dominated by Pinus pinaster Ait. (maritime pine) are subject to a shift from fuel-limited to drought-driven fire regimes, characterized by an increasing wildfire extent, recurrence, and severity. Previous studies have not addressed the interacting effects of fire recurrence and severity on the ecosystem multifunctionality (EMF) of maritime pine forests, although complex relationships between such fire regime attributes are expected. Here, we evaluated the medium-term effects of fire recurrence and severity on the EMF response of unmanaged, native pine ecosystems dominated by Pinus pinaster in the western Mediterranean Basin. We considered four key ecosystem functions computed from functional indicators (carbon regulation, decomposition, soil fertility, and plant production), which were pooled into an EMF construct. The fire regime effects on the trade-offs and synergies between the considered ecosystem functions were also analyzed. Results Multiple ecosystem functions responded differentially to fire recurrence and severity. Fire recurrence had a strong effect on soil fertility, decomposition, and plant production functions. No significant effects of fire severity on any of the individual functions were detected. However, both fire regime attributes interacted to determine soil fertility and decomposition functions, suggesting that their performance is only impaired by fire severity when fire recurrence is low. The differing responses to the fire regime attributes among ecosystem functions fostered a significant EMF response to fire severity and its interaction with fire recurrence, indicating that the effect of fire severity on EMF was stronger under low fire recurrence scenarios, even when relationships between individual functions and fire severity were weak. Fire recurrence caused significant trade-offs between functions to emerge. However, these trade-offs were not strong enough to differ significantly from the intrinsic trade-offs (i.e., regardless of the fire regime) of maritime pine ecosystems. Conclusions Our results indicated the need to use an integrative approach to assess the response of ecosystem functioning to the fire regime in maritime pine ecosystems. Adaptive management responses are necessary towards the minimization of repeated burnings and the reduction of the fuel load in unmanaged maritime pine stands of the western Mediterranean Basin with similar characteristics to those analyzed in this study.[ES], Antecedentes Los ecosistemas mediterráneos dominados por pino marítimo (Pinus pinaster Ait.) están sujetos a cambios en regímenes de fuego limitados por el combustible hacia regímenes conducidos por la sequía, y caracterizados por un incremento en la extensión, recurrencia y severidad de los incendios. Estudios previos no han abordado los efectos interactivos de la recurrencia y severidad del fuego en la multifuncionalidad de los ecosistemas (EMF) en bosques de pino marítimo, aunque cabe esperar relaciones complejas entre estos atributos del regimen de fuego. En este trabajo, evaluamos los efectos a medio plazo de la recurrencia y severidad en la respuesta de la multifuncionalidad de los ecosistemas (EMF) de bosques nativos dominados por pino marítimo no gestionados en la cuenca Mediterránea occidental. Consideramos cuatro funciones clave calculadas a partir de indicadores funcionales (regulación del carbono, descomposición, fertilidad del suelo, y producción egetal) los cuales fueron agrupados en un constructo EMF. Los efectos del régimen de fuego sobre las sinergias y contrapartidas entre las funciones ecosistémicas también fueron analizados. Resultados Múltiples funciones ecosistémicas respondieron diferencialmente a la recurrencia y severidad. La recurrencia del fuego tuvo un efecto muy fuerte en la fertilidad del suelo, en la descomposición y en las funciones de producción. Ningún efecto significativo de la severidad del fuego fue detectado en ninguna de las funciones individuales. Sin embargo, los atributos de ambos regímenes de fuego interactuaron para determinar las funciones de fertilidad y descomposición, sugiriendo que su rendimiento es afectado por la severidad solo cuando la recurrencia del fuego es baja. Las diferentes respuestas a los atributos de los regímenes de fuego entre las funciones ecosistémicas promueven una respuesta significativa de la EMF a la severidad del fuego y su interacción con la recurrencia, indicando que el efecto de la severidad sobre la EMF fue más fuerte bajo escenarios de baja recurrencia, aun cuando las relaciones entre funciones individuales y la severidad fueran débiles. La recurrencia del fuego causó la aparición de ontrapartidas significativas entre funciones. Obviamente, estas contrapartidas no fueron lo suficientemente fuertes para diferir significativamente de aquellas intrínsecas (i.e., independientemente del régimen de fuego) en los ecosistemas de pino marítimo. Conclusiones Nuestros resultados indican la necesidad de usar una aproximación integrada para determinar la respuesta del funcionamiento al régimen de fuego en ecosistemas de pino marítimo. Respuestas de manejo adaptativo son necesarias para la minimización de quemas repetidas y la reducción de la carga de combustible en rodales de pino marítimo no gestionados en la cuenca Mediterránea, con características similares a aquellos analizados en este estudio.SIAEIBritish Ecological SocietyPortuguese Foundation for Science and Technolog