Cork oak vulnerability to fire: the role of bark harvesting, tree characteristics and abiotic factors

Forest ecosystems where periodical tree bark harvesting is a major economic activity may be particularly vulnerable to disturbances such as fire, since debarking usually reduces tree vigour and protection against external agents. In this paper we asked how cork oak Quercus suber trees respond after wildfires and, in particular, how bark harvesting affects post-fire tree survival and resprouting. We gathered data from 22 wildfires (4585 trees) that occurred in three southern European countries (Portugal, Spain and France), covering a wide range of conditions characteristic of Q. suber ecosystems. Post-fire tree responses (tree mortality, stem mortality and crown resprouting) were examined in relation to management and ecological factors using generalized linear mixed-effects models. Results showed that bark thickness and bark harvesting are major factors affecting resistance of Q. suber to fire. Fire vulnerability was higher for trees with thin bark (young or recently debarked individuals) and decreased with increasing bark thickness until cork was 3–4 cm thick. This bark thickness corresponds to the moment when exploited trees are debarked again, meaning that exploited trees are vulnerable to fire during a longer period. Exploited trees were also more likely to be top-killed than unexploited trees, even for the same bark thickness. Additionally, vulnerability to fire increased with burn severity and with tree diameter, and was higher in trees burned in early summer or located in drier south-facing aspects. We provided tree response models useful to help estimating the impact of fire and to support management decisions. The results suggested that an appropriate management of surface fuels and changes in the bark harvesting regime (e.g. debarking coexisting trees in different years or increasing the harvesting cycle) would decrease vulnerability to fire and contribute to the conservation of cork oak ecosystemsinfo:eu-repo/semantics/publishedVersio

Assessing changes in global fire regimes

PAGES, Past Global Changes, is funded by the Swiss Academy of Sciences and the Chinese Academy of Sciences and supported in kind by the University of Bern, Switzerland. Financial support was provided by the U.S. National Science Foundation award numbers 1916565, EAR-2011439, and EAR-2012123. Additional support was provided by the Utah Department of Natural Resources Watershed Restoration Initiative. SSS was supported by Brigham Young University Graduate Studies. MS was supported by National Science Centre, Poland (grant no. 2018/31/B/ST10/02498 and 2021/41/B/ST10/00060). JCA was supported by the European Union’s Horizon 2020 research and innovation program under the Marie Skłodowska-Curie grant agreement No 101026211. PF contributed within the framework of the FCT-funded project no. UIDB/04033/2020. SGAF acknowledges support from Trond Mohn Stiftelse (TMS) and University of Bergen for the startup grant ‘TMS2022STG03’. JMP participation in this research was supported by the Forest Research Centre, a research unit funded by Fundação para a Ciência e a Tecnologia I.P. (FCT), Portugal (UIDB/00239/2020). A.-LD acknowledge PAGES, PICS CNRS 06484 project, CNRS-INSU, Région Nouvelle-Aquitaine, University of Bordeaux DRI and INQUA for workshop support.Background The global human footprint has fundamentally altered wildfire regimes, creating serious consequences for human health, biodiversity, and climate. However, it remains difficult to project how long-term interactions among land use, management, and climate change will affect fire behavior, representing a key knowledge gap for sustainable management. We used expert assessment to combine opinions about past and future fire regimes from 99 wildfire researchers. We asked for quantitative and qualitative assessments of the frequency, type, and implications of fire regime change from the beginning of the Holocene through the year 2300. Results Respondents indicated some direct human influence on wildfire since at least ~ 12,000 years BP, though natural climate variability remained the dominant driver of fire regime change until around 5,000 years BP, for most study regions. Responses suggested a ten-fold increase in the frequency of fire regime change during the last 250 years compared with the rest of the Holocene, corresponding first with the intensification and extensification of land use and later with anthropogenic climate change. Looking to the future, fire regimes were predicted to intensify, with increases in frequency, severity, and size in all biomes except grassland ecosystems. Fire regimes showed different climate sensitivities across biomes, but the likelihood of fire regime change increased with higher warming scenarios for all biomes. Biodiversity, carbon storage, and other ecosystem services were predicted to decrease for most biomes under higher emission scenarios. We present recommendations for adaptation and mitigation under emerging fire regimes, while recognizing that management options are constrained under higher emission scenarios. Conclusion The influence of humans on wildfire regimes has increased over the last two centuries. The perspective gained from past fires should be considered in land and fire management strategies, but novel fire behavior is likely given the unprecedented human disruption of plant communities, climate, and other factors. Future fire regimes are likely to degrade key ecosystem services, unless climate change is aggressively mitigated. Expert assessment complements empirical data and modeling, providing a broader perspective of fire science to inform decision making and future research priorities.Peer reviewe

Wildfire effects on Pinus halepensis Mill. plantations in a semi-arid region of north-eastern Algeria. A case study of Zenadia forest, Sétif

Fire is considered as the most important factor responsible for the diminution of Algerian forested area. Every year, thousands of hectares of vegetation burn affecting different species. The natural Aleppo pine forests have been the most affected, but recently, fire tends to affect also the planted forests. The effect of fire on Aleppo pine natural stands is well documented ; however, there is a lack of knowledge on planted ones. The objectives of this paper were to assess the fire effects on Pinus halepensis plantations in northern Algeria in terms of floristic diversity and pine regeneration. Floristic diversity surveys were performed three years after fire in burned and unburned plots, using the Braun-Blanquet method. Additionally, the number and height of P. halepensis seedlings were assessed and continued to be monitored in the best regenerated area four, six, eight, and ten years after fire occurrence. The floristic surveys performed showed large differences between the unburned and the burned plots, both in terms of vegetation structure and plant diversity. Three years after fire, the burned plots were dominated by an herbaceous layer and had a much higher floristic richness when compared with the unburned plots. Pine regeneration was absent in the unburned area, while in the burned area it reached up to nearly three seedlings per m2 after three years. Seedling density decreased over time while maximum height increased up to two meters ten years after fire. Our results suggest that prescribed burning, associated to selective logging, could be an interesting management tool to explore in these artificial stands. This could create forest gaps that would permit the natural regeneration of Aleppo pine and others species, favouring multi-strata forest and biodiversity.Le feu est considéré comme le plus important facteur responsable de la régression des forêts algériennes. Chaque année, des milliers d’hectares de végétation brûlent en affectant différentes essences. Les peuplements naturels de pins d’Alep sont les plus touchés, mais récemment, le feu a tendance à affecter également les forêts plantées. L’effet du feu sur les peuplements naturels de pin d’Alep est bien documenté ; toutefois, il y a un manque de connaissances au sujet des peuplements plantés. L’objectif de cet article est d’évaluer les effets du feu sur les plantations de Pinus halepensis dans le nord de l’Algérie, notamment en termes de diversité floristique et de régénération post- incendie. Des relevés floristiques ont été réalisés trois ans après le feu dans les parcelles brûlées et d’autres non brûlées servant de témoins en utilisant la méthode de Braun-Blanquet. Le nombre et la hauteur des plants des pins ont été également notés. La collecte de ces dernières données a été poursuivie dans la partie mieux régénérée à quatre, six, huit et dix ans après le passage du feu. Les relevés floristiques ont montré de grandes différences entre ceux réalisés dans le reboisement non brûlé et la zone brûlée, à la fois en termes de structure de la végétation et de la diversité floristique. Trois ans après le feu, les parcelles brûlées ont été dominées par la strate herbacée et avaient une richesse floristique beaucoup plus élevée en comparaison avec le reboisement non brûlé. La régénération du pin était absente dans la forêt non brûlée, tandis que dans la zone brûlée elle a atteint près de deux plants par m2 trois ans après feu. La densité des semis a diminué au fil du temps alors que la hauteur maximale a augmenté pour atteindre les deux mètres, dix ans après le feu. Nos résultats suggèrent que le brûlage dirigé, associé à des coupes sélectives, pourrait être également un outil de gestion intéressant à explorer dans ces peuplements artificiels. Cela pourrait créer des trouées forestières qui permettraient la régénération naturelle de pin d’Alep et d’autres espèces, favorisant ainsi le développement d’une forêt multistrates et de la biodiversité.Madoui Amar, Catry Filipe X., Kaabeche Mohamed. Wildfire effects on Pinus halepensis Mill. plantations in a semi-arid region of north-eastern Algeria. A case study of Zenadia forest, Sétif. In: Ecologia mediterranea, tome 42 n°1, 2016. pp. 79-92

Tapada Nacional de Mafra, um caso de sucesso no restauro do coberto florestal em áreas ardidas

A Tapada Nacional de Mafra (TNM) – Centro Turístico, Cinegético e de Educação Ambiental, é gerida desde 1998 por uma régie-cooperativa de responsabilidade limitada, é um espaço de carácter fortemente florestal inserido no conjunto histórico-cultural formado pelo Palácio Nacional de Mafra, Jardim do Cerco e pela originalmente designada Tapada Real de Mafra Detentora de um importante património natural, a TNM constitui um espaço multifuncional que decorre da diversidade de valências, posicionando-a como espaço privilegiado de biodiversidade, memória histórica e cultural, turismo e lazer, educação ambiental, gestão sustentável dos recursos, conhecimento científico, aprendizagem e demonstração, tendo por missão promover a sua preservação e valorização em respeito pelos seus valores, património e história. Em Setembro de 2003, um incêndio florestal afetou 70% do coberto vegetal, com elevados prejuízos na riqueza florestal e faunística existente. Iniciou-se de imediato a extração da madeira queimada e elaborou-se o novo plano de ordenamento. Em 2004 iniciou-se o processo de recuperação das áreas ardidas visando a reposição dos valores ambientais e paisagísticos, a implementação de um plano de defesa da floresta contra incêndios, a proteção das espécies faunísticas com elevado interesse conservacionista e a exploração de matérias primas de origem florestal. No mesmo ano iniciaram-se os inventários para monitorização e estudo da regeneração natural, das ações de rearborização e do impacte dos herbívoros, tendo em vista analisar a capacidade regenerativa e desenvolvimento dos novos povoamentos. Pretende-se fazer uma análise retrospetiva da evolução da TNM desde a situação anterior ao incêndio, apresentando os primeiros resultados da evolução da regeneração florestal, analisa-se a situação atual e apresentam-se as estratégias para a sua gestão sustentável. Esta experiência constitui um exemplo de restauração do coberto florestal pós incêndio, em conciliação com a valorização ambiental, a gestão cinegética e a sustentabilidade ambiental e económica destes espaços florestaisinfo:eu-repo/semantics/publishedVersio

Ambrosia Beetle Attacks in Mediterranean Cork Oak Forests Following Fire: Which Factors Drive Host Selection?

Mediterranean Basin forest ecosystems are recurrently affected by wildfires. The occurrence of insect pests following fire may be a critical factor affecting tree survival and forest recovery. Although ambrosia beetles are viewed with increasing concern, information about the host selection and colonization behavior of these beetles in Mediterranean broadleaf forests is very scarce and inexistent in areas affected by wildfires. After a forest fire in Portugal, we selected 841 burned and unburned cork oak trees and assessed the presence and intensity of ambrosia beetle attacks, as well as other tree characteristics, and used generalized linear models to investigate the factors driving host selection. In contrast with burned oaks, where beetle attacks were frequent, the unburned trees were little affected. Attacks in the burned forest were more frequent in larger trees that suffered higher fire severity, in trees being exploited for cork (but with thicker bark), and in trees that were closer to the unburned area. A contagious effect to neighboring unburned trees was not observed, and cork harvesting in subsequent years following fire also did not increase the probability of beetle attacks. These results help us to understand the risk of ambrosia beetle attacks and improve forest management in cork oak forests

Ambrosia Beetle Attacks in Mediterranean Cork Oak Forests Following Fire: Which Factors Drive Host Selection?

Mediterranean Basin forest ecosystems are recurrently affected by wildfires. The occurrence of insect pests following fire may be a critical factor affecting tree survival and forest recovery. Although ambrosia beetles are viewed with increasing concern, information about the host selection and colonization behavior of these beetles in Mediterranean broadleaf forests is very scarce and inexistent in areas affected by wildfires. After a forest fire in Portugal, we selected 841 burned and unburned cork oak trees and assessed the presence and intensity of ambrosia beetle attacks, as well as other tree characteristics, and used generalized linear models to investigate the factors driving host selection. In contrast with burned oaks, where beetle attacks were frequent, the unburned trees were little affected. Attacks in the burned forest were more frequent in larger trees that suffered higher fire severity, in trees being exploited for cork (but with thicker bark), and in trees that were closer to the unburned area. A contagious effect to neighboring unburned trees was not observed, and cork harvesting in subsequent years following fire also did not increase the probability of beetle attacks. These results help us to understand the risk of ambrosia beetle attacks and improve forest management in cork oak forests

Eucalypt Recruitment and Invasion Potential in Protected Areas of the Iberian Peninsula under Current and Future Climate Conditions

Eucalyptus globulus Labill. stands have been expanding in protected areas (sites) of the Natura 2000 network in the Iberian Peninsula (Iberia). This expansion is mostly human-driven, but there is increasing evidence of plant recruitment and escape from cultivation areas. Therefore, it is important to assess the recruitment and invasion potential of sites and associated habitats and how future climate may change this potential. Here, we use SDMs to project current and future climatic suitability for E. globulus recruitment in Iberia and combine this suitability with local factors to rate the current recruitment potential of eucalypt stands. This potential is then extrapolated to neighbour areas in Natura 2000 sites to assess the invasion potential. The results show a wide recruitment range along coastal regions of western and northern Iberia (83,275 km2) and a northward contraction under climate change, similar to the trend projected for plantation suitability. Recruitment potential of any level was identified in 989 km2, while invasion potential was identified in 878 km2 across 176 Natura 2000 sites. Heathlands and riparian forests were associated with the largest recruitment and invasion potential areas. This study may help in preventing further negative impacts in protected areas and habitats already affected by E. globulus expansion

Data from: Site- and tree-related factors affecting colonization of cork oaks Quercus suber L. by ambrosia beetles in Tunisia

Key message: Ambrosia beetles are emerging globally as important agents of tree death and decline. In this work, we observed highly variable attack intensity by ambrosia beetles in cork oak stands in Tunisia. A correlation between the proportion of infested trees and average temperature was found. Tree diameter and tree phytosanitary variables further contribute to the attack densities of ambrosia beetles. Results can be relevant for preventive measures aiming to conserve this natural forest heritage. Context: Cork oak woodlands comprise a unique Mediterranean ecosystem supporting rich biological diversity and providing multiple services. A decline of cork oak forests has been observed in several regions of the Mediterranean Basin in the last four decades, which can be related to climate change, novel biotic agents, and changes in management practices. The ambrosia beetles have been one of the major biotic agents associated with cork oak decline, mostly in the western Mediterranean. Aims: Assess the presence and attack densities of ambrosia beetles in cork oak Tunisian forests. Methods: A total of 15 sites located in North Western of Tunisia, comprising 729 sample trees were evaluated. Using generalized linear models, the presence and density of ambrosia beetles’ holes were related to tree and site variables. Variables related to climate, tree (dendrometric parameters, debarking intensity) and biotic agents were examined. Results: The proportion of trees attacked per site varied from 0 to 100%; in four sites it exceeded 50%. At the site level, the average temperature and tree diameter were the main variables explaining the proportion of attacked trees. Sites with warmer climates showed higher incidence of ambrosia beetles. At the tree level, the presence of attacks increased with tree diameter and concomitantly with intensity of debarking, as well as the presence of tree trunk cavities. Conclusion: The presence and density of insect attacks were related to tree diameter, area of debarking, and phytosanitary conditions. However, 19% of the trees attacked by ambrosia beetles had no signs of other biotic agents or decline. At the site level, attack rates increased with temperature and tree diameter. A warmer climate may change insect behavior from that of a non-agressive pest to that of an agressive bark beetle. Adaptive forest management practices are needed to reduce infestations