SPONFOREST focuses on five study systems located in rural landscapes of France and Spain, two countries that have experienced strong increments in forest cover during the past decades (France: 35% since 1945, Spain: 25% since 1950). The case studies present a wide range of ecological and societal contexts, including the larger metropolitan area of Barcelona as well as sparsely populated mountain ranges. Each case study focuses on one major forest tree species within its landscape context and investigates at least 15 forest stands that have established or strongly expanded since 1950 and are dominated by this tree species. The dynamics and ecological consequences of forest regrowth are investigated using a broad spectrum of disciplines including dendroecology, population genetics, functional ecology, remote sensing, and landscape analysis. The empirical data inform a demo-genetic model of forest stand expansion. The societal implications of forest regrowth are assessed using standardized surveys and in-depth expert interviews with stakeholders and policy makers. 

Please note that further details about our case studies can be found in the following synthesis paper: 

• Martín-Forés I, Magro S, Bravo-Oviedo A, Alfaro-Sánchez R, Espelta JM, Frei T, Valdés-Correcher E, Rodríguez Fernández-Blanco C, Winkel G, Gerzabek G, González-Martínez SC, Hampe A,  Valladares F (2020) Spontaneous forest regrowth in South-West Europe: consequences for nature’s contributions to people. People and Nature 2: 980-994. pdf

Case Study 1: Pedunculate oak forests in the Landes de Gascogne, south-western France

Responsible researchers: Arndt Hampe & Bastien Castagneyrol, BIOGECO, France

The Landes de Gascogne region in SW France harbours the largest forest plantation in Europe with almost a million hectares of pure maritime pine (Pinus pinaster) stands. Pine planting began in the mid 19^th century in a formerly largely deforested area. Since then, the region has experienced a very effective spread of Pedunculate oak (Quercus robur) and other broadleaved tree species. Today, thousands of small stands of oak-dominated broadleaf forest grow scattered across the landscape. Such stands are largely exempt from forest management. Many are actively expanding, favoured by a recent change in silvicultural management that tends to conserve oaks recruiting within adjacent pine plantations as a means of biological pest management. Common local uses include coppicing for fire wood, hunting, and the collection of fruits and mushrooms. 

Related references

• Gerzabek G, Oddou-Muratorio S, Hampe A (2017) Temporal change and determinants of maternal reproductive success in an expanding oak forest stand. Journal of Ecology 105: 39-48.
• Valdés-Correcher E, van Halder I, Barbaro L, Castagneyrol B, Hampe A (2019) Insect herbivory and avian insectivory in novel native oak forests: divergent effects of stand size and connectivity. Forest Ecology and Management 445: 146-153.
• Alfaro-Sánchez R, Valdés-Correcher E, Espelta JM, Hampe A, Bert D (2020) How do social status and tree architecture influence radial growth, wood density and drought response in spontaneously established oak forests? Annals of Forest Science 77: 49.

Case Study 2: Spanish juniper forests in the Alto Tajo Natural Park, central Spain

Responsible researchers: Fernando Valladares & Irene Martín-Forés, MNCN, Spain

Parkland type woodlands formed by Spanish juniper (Juniperus thurifera) constitute a singular vegetation that characterises the high plains of the inner Iberian Peninsula. They grow under an exceptionally harsh continental climate with cold winters and hot-dry summers that imposes strong constraints on the establishment of other tree species. Spanish juniper is endemic to the western Mediterranean Basin and occupies ca. 600,000 ha in Spain, with 117,000 ha being monospecific forests. These have a long history of fragmentation and depletion by traditional agriculture and livestock grazing. Yet a massive rural exodus in the region since the 1950s has spurred a vigourous expansion and densification of the remaining forests that benefit from the lack of competing land uses.

 Related references

• Acuña-Míguez B, Valladares F, Martín-Forés I (2020) Both mature patches and expanding areas of Juniperus thurifera forests are vulnerable to climate change but for different reasons. Forests 11: 960
• Villellas J, Martín-Forés I, Mariette S, Massot M, Guichoux E, Acuña-Míguez B, Hampe A, Valladares F (2020) Functional distance is triggered more strongly by environmental factors than by genetic relatedness in expanding Juniperus thurifera forest stands. Annals of Forest Science 77: 66.
• Alfaro-Sánchez R, Espelta JM, Valladares F, Acuña-Míguez B, Martín-Forés I (2021) Disentangling the role of sex dimorphism and forest structure as drivers of growth and wood density in expanding Juniperus thurifera L. woodlands. Annals of Forest Science 78: 86.

Case Study 3: Beech forests in the Catalan Pre-Pyrenees, north-eastern Spain

Responsible researchers: Josep Maria Espelta & Joan Pino, CREAF, Spain

The Catalan Pre-Pyrenees are a large and complex system of foothills that run parallel to the main Pyrenees mountain range in Catalonia (NE Spain). A Mediterranean mountain-type climate with moderate temperatures and abundant precipitation allows the development of extensive deciduous broadleaf forests dominated by European beech (Fagus sylvatica). Such forests, while common in Central Europe, approach here their southwestern range limits. The area experienced massive depopulation during the second half of the 20^th century, which has spurred widespread expansions of secondary beech forests into former pasturelands. The fact that increasing drought episodes have been predicted to threaten the continued persistence of beech in the region draws particular interest to the question whether these novel beech forests are responding to modern climate change in a similar way than long-established ones. Today, novel beech forests are primarily used for extensive sylviculture, hunting and recreation.

Related references

• Alfaro-Sánchez R, Jump AS, Pino J, Díez-Nogales O, Espelta JM (2019) Land use legacies drive higher growth, lower wood density and enhanced climatic sensitivity in recently established forests. Agricultural and Forest Meteorology 276: 107630.
• Espelta J, Cruz-Alonso V, Alfaro-Sánchez R, Hampe A, Messier C, Pino J (2020) Functional diversity enhances tree growth and reduces herbivory damage in secondary broadleaf forests but does not influence resilience to drought. Journal of Applied Ecology 57: 2362-2372.
• Guerrieri R, Correia M, Martín-Forés I, Alfaro-Sánchez R, Pino J, Hampe A, Valladares F, Espelta JM (2021) Land-use legacies influence tree water-use efficiency and nitrogen availability in recently established European forests. Functional Ecology 35: 1325-1340.

Case Study 4: Holm oak forests in the Barcelona metropolitan area, north-eastern Spain

Responsible researchers: Josep Maria Espelta & Joan Pino, CREAF, Spain

The metropolitan area of Barcelona is one of the most industrialized and populated areas in the northern rim of the Mediterranean Basin. A heterogeneous topography gives rise to strong environmental variability in terms of landscape structure, habitat types, and human disturbance. Forests are concentrated along the pre-coastal and coastal ranges, while adjacent lowlands are dominated by croplands and urban areas. Spontaneous forest expansion into abandoned agricultural lands was especially intense during the second half of the 20^th century, and ca. 30% of the present-day forest cover have appeared during the last decades. Holm oak (Quercus ilex) is the dominant tree species in many of these secondary forest patches that harbour a rich flora and fauna. Other relevant ecosystem services include their role as efficient carbon sinks and local recreation areas, while they might also contribute to increment fire hazards.

Related references

• Ruíz‐Carbayo H, Bonal R, Pino J, Espelta JM (2018) Zero‐sum landscape effects on acorn predation associated with shifts in granivore insect community in new holm oak (Quercus ilex) forests. Diversity and Distributions 24: 521-534.
• Ruíz-Carbayo H, Pino J, Bonal R, James PM, Hampe A, Molowny-Horas R, Espelta JM (2020) Insect herbivory in novel Quercus ilex L. forests: the role of landscape attributes, forest composition and host traits. Annals of Forest Science 77: 32.
• Tello-García E, Gamboa-Badilla N, Álvarez E, Fuentes L, Basnou C, Espelta JM, Pino J (2021) Plant species surplus in recent peri-urban forests: the role of forest connectivity, species’ habitat requirements and dispersal types. Biodiversity and Conservation 30: 365-384.

Case study 5: Atlas cedar forests in the future Mont Ventoux and Luberon Regional Natural Park, south-eastern France

Responsible researchers: Thomas Boivin & François Lefèvre, URFM, France

Atlas cedar (Cedrus atlantica) has been introduced in low and mid-altitude mountain ranges of southern France since the middle of the 19th century with the aim to restore the depleted local forest cover by establishing stands capable of natural regeneration. Today, Atlas cedar is mainly found in the Languedoc-Roussillon and Provence-Alpes-Côte-d'Azur regions. The species has vigorously expanded since its introduction in the Luberon and Mont Ventoux mountains and is today the dominant forest tree species on ca. 20,000 hectares. It forms continuous stands as well as more or less isolated patches formed by the abrupt mountain topography that characterizes the study area.  Atlas cedar forests have become a resource of notable local interest that provide multiple ecosystem services including the production of high-quality timber, hunting grounds, and opportunities for tourism and recreation. They are also used as seed sources for reforestation activities in other regions, as Atlas cedar's proven drought resistance makes it a tree of choice for foresters in many Mediterranean climate areas.

Related references

• Lefèvre F, Fady B, Fallour-Rubio D, Ghosn D, Bariteau M (2004) Impact of founder population, drift and selection on the genetic diversity of a recently translocated tree population. Heredity 93: 542-550.
• Fallour-Rubio D, Guibal F, Klein EK, Bariteau M, Lefèvre F (2009) Rapid changes in plasticity across generations within an expanding cedar forest. Journal of Evolutionary Biology 22: 553-563.
• Doublet, V., Gidoin, C., Lefèvre, F, Boivin T (2019) Spatial and temporal patterns of a pulsed resource dynamically drive the distribution of specialist herbivores. Scientific Reports 9: 17787 .