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Tree rings provide an invaluable long-term record for understanding how climate and other drivers shape tree growth and forest productivity. However, conventional tree-ring analysis methods were not designed to simultaneously test effects of climate, tree size, and other drivers on individual growth. This has limited the potential to test ecologically relevant hypotheses on tree growth sensitivity to environmental drivers and their interactions with tree size. Here, we develop and apply a new method to simultaneously model nonlinear effects of primary climate drivers, reconstructed tree diameter at breast height (DBH), and calendar year in generalized least squares models that account for the temporal autocorrelation inherent to each individual tree's growth. We analyze data from 3811 trees representing 40 species at 10 globally distributed sites, showing that precipitation, temperature, DBH, and calendar year have additively, and often interactively, influenced annual growth over the past 120 years. Growth responses were predominantly positive to precipitation (usually over ≥3-month seasonal windows) and negative to temperature (usually maximum temperature, over ≤3-month seasonal windows), with concave-down responses in 63% of relationships. Climate sensitivity commonly varied with DBH (45% of cases tested), with larger trees usually more sensitive. Trends in ring width at small DBH were linked to the light environment under which trees established, but basal area or biomass increments consistently reached maxima at intermediate DBH. Accounting for climate and DBH, growth rate declined over time for 92% of species in secondary or disturbed stands, whereas growth trends were mixed in older forests. These trends were largely attributable to stand dynamics as cohorts and stands age, which remain challenging to disentangle from global change drivers. By providing a parsimonious approach for characterizing multiple interacting drivers of tree growth, our method reveals

Tree rings provide an invaluable long-term record for understanding how climate and other drivers shape tree growth and forest productivity. However, conventional tree-ring analysis methods were not designed to simultaneously test effects of climate, tree size, and other drivers on individual growth. This has limited the potential to test ecologically relevant hypotheses on tree growth sensitivity to environmental drivers and their interactions with tree size. Here, we develop and apply a new method to simultaneously model nonlinear effects of primary climate drivers, reconstructed tree diameter at breast height (DBH), and calendar year in generalized least squares models that account for the temporal autocorrelation inherent to each individual tree's growth. We analyze data from 3811 trees representing 40 species at 10 globally distributed sites, showing that precipitation, temperature, DBH, and calendar year have additively, and often interactively, influenced annual growth over the past 120 years. Growth responses were predominantly positive to precipitation (usually over ≥3-month seasonal windows) and negative to temperature (usually maximum temperature, over ≤3-month seasonal windows), with concave-down responses in 63% of relationships. Climate sensitivity commonly varied with DBH (45% of cases tested), with larger trees usually more sensitive. Trends in ring width at small DBH were linked to the light environment under which trees established, but basal area or biomass increments consistently reached maxima at intermediate DBH. Accounting for climate and DBH, growth rate declined over time for 92% of species in secondary or disturbed stands, whereas growth trends were mixed in older forests. These trends were largely attributable to stand dynamics as cohorts and stands age, which remain challenging to disentangle from global change drivers. By providing a parsimonious approach for characterizing multiple interacting drivers of tree growth, our method reveals

European forests are expanding and becoming denser following the widespread abandonment of farmland and rural areas. Spontaneous forest regrowth provides a cost-effective opportunity to restore ecosystems, enhance multifunctionality and sustainability and mitigate climate change. Yet, little is known about the goods and services that such forests provide to people. We assessed the changes in nature's contributions to people (NCP) from spontaneous forest regrowth, i.e. forest expansion and densification, in South-West Europe. We investigated 65 forest plots in four different landscapes with contrasting ecological and societal contexts. Two landscapes are located in rural areas undergoing human exodus and forest expansion and densification; the other two, in peri-urban areas with intense land use and forest densification but negligible expansion. For each forest plot, we estimated variables related to ten out of the 18 main NCP defined by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). Regulating and material NCP were addressed using variables measured in the field as proxies. Non-material NCP were studied through stakeholder interviews. Our results show across the cases that forest expansion and densification are generally associated with greater climate regulation and energy provision. Changes in other NCP, especially in non-material ones, were strongly context-dependent. The social perception of spontaneous forest regrowth was primarily negative in rural areas and more positive in peri-urban landscapes. Passive restoration through spontaneous forest expansion and densification can enhance regulating and material NCP, especially when adaptive management is applied. To optimise NCP and to increase the societal awareness of and interest in spontaneous forest regrowth, the effects of this process should be analysed in close coordination with local stakeholders to unveil and quantify the many and complex trade-offs involved

[Context] European forests are expanding and becoming denser following the widespread abandonment of farmland and rural areas. Yet, little is known about the goods and services that spontaneous forest regrowth provide to people., [Aims] We assessed the changes in nature’s contributions to people (NCP) from spontaneous forest regrowth, i.e. forest expansion and densification, in South-West Europe., [Methods We investigated 65 forest plots in four different landscapes with contrasting ecological and societal contexts. Two landscapes are located in rural areas undergoing human exodus and forest expansion and densification; the other two, in peri-urban areas with intense land use and forest densification but negligible expansion. For each forest plot, we estimated variables related to ten out of the 18 main NCP defined by the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services (IPBES). Regulating and material NCP were addressed using variables measured in the field as proxies. Non-material NCP were studied through stakeholder interviews., [Results] Our results show across the cases that forest expansion and densification is generally associated with greater climate regulation and energy provision. Changes in other NCP, especially in non-material ones, were strongly context-dependent. The social perception of spontaneous forest regrowth was primarily negative in rural areas and more positive in peri-urban landscapes., [Conclusion] Passive restoration through spontaneous forest expansion and densification can enhance regulating and material NCP, especially when adaptive management is applied. To optimise NCP and to increase the societal awareness of and interest in spontaneous forest regrowth, the effects of this process should be analysed in close coordination with local stakeholders to unveil and quantify the many and complex trade-offs involved in rural or peri-urban social perceptions.

European forests are expanding and becoming denser following the widespread abandonment of farmland and rural areas. Spontaneous forest regrowth provides a cost-effective opportunity to restore ecosystems, enhance multifunctionality and sustainability and mitigate climate change. Yet, little is known about the goods and services that such forests provide to people. We assessed the changes in nature's contributions to people (NCP) from spontaneous forest regrowth, i.e. forest expansion and densification, in South West Europe.We investigated 65 forest plots in four different landscapes with contrasting ecological and societal contexts. Two landscapes are located in rural areas undergoing human exodus and forest expansion and densification; the other two, in peri¿urban areas with intense land use and forest densification but negligible expansion. For each forest plot, we estimated variables related to ten out of the 18 main NCP defined by the Intergovernmental Science Policy Platform on Biodiversity and Ecosystem Services (IPBES). Regulating and material NCP were addressed using variables measured in the field as proxies. Non material NCP were studied through stakeholder interviews. Our results show across the cases that forest expansion and densification are generally associated with greater climate regulation and energy provision. Changes in other NCP, especially in non material ones, were strongly context¿dependent. The social perception of spontaneous forest regrowth was primarily negative in rural areas and more positive in peri-urban landscapes. Passive restoration through spontaneous forest expansion and densification can enhance regulating and material NCP, especially when adaptive management is applied. To optimise NCP and to increase the societal awareness of and interest in spontaneous forest regrowth, the effects of this process should be analysed in close coordination with local stakeholders to unveil and quantify the many and complex trade-offs involved i

Key message This special issue gathers articles arising from the ERA-NET BiodivERsA3 research project “Unraveling the Potential of Spontaneous Forest Establishment for Improving Ecosystem Functions and Services in Dynamic Landscapes (SPONFOREST)”. Using a broad spectrum of research approaches, they provide detailed insights into how new forest stands establish and which consequences the establishment process has for their character and functioning.

Understanding the relative contributions of competition and climate on individual tree growth is critical to project realistic forest dynamics under projected climate scenarios. Furthermore, present competition levels may reflect legacies of past use. Here, we analyze the effects of climate, site conditions and competition on radial growth in three Scots pine stands located along an altitudinal gradient in central Spain. Current stand structure and retrospective analyses of radial growth (basal area increment, BAI) were used to model changes in tree growth as a function of a spatially-explicit competition index (CI) and climate. Linear mixed-effects models were employed to model BAI and to quantify the growth responses to climate of trees under low and high competition levels. Competition effects on growth were steady over time regardless of tree age. High competition levels negatively affected growth since negative exponential functions characterized the CI-BAI relationships. Tree growth sensitivity to climate increased with decreasing competition intensity. Growth at high elevations was mainly limited by low winter temperatures, whereas warm spring enhanced growth at middle elevations and warm late summer temperatures constrained growth at low elevation. Growth responsiveness to climate is enhanced under low competition levels. Overall, current competition is a more relevant driver of recent growth than climate. Proactive forest management should be adopted to reduce the vulnerability of Scots pine forests currently subjected to higher competition levels and warmer and drier conditions. © 2015 Elsevier B.V.

In fire-and drought-prone Mediterranean forests tree growth and regeneration depend on the moisture regime between fires. Therefore, post-fire tree regeneration will depend on moisture conditions and how they are altered by fire recurrence and climate warming. Aleppo pine forests are the most abundant Circum-Mediterranean ecosystems subjected to frequent wildfires and summer droughts. Because both stressors constrain their reproduction and growth patterns across diverse ecological conditions, these forests represent a suitable system to test how moisture availability drives post-fire regeneration. Aleppo pine is an obligate seeder species that reproduces at an early age after fire. Such precocious behaviour poses the question as to whether post-fire regeneration depends on moisture conditions and the coupling between female cone production and growth. Here, we evaluate if female cone production and radial growth are linked at the tree level in post-fire Aleppo pines by comparing a dry v. a very dry site and considering stands with three different tree densities in south-eastern ESP. We found that trees with higher basal areas produced more female cones and this positive association intensified as the water balance improved. Aleppo pines from the very dry site were more precocious in reproductive terms than pines of the same age from the dry site, but long-term cone production was lower at the very dry site. Lower tree density enhances the resilience of xeric post-fire Aleppo pine forests, in growth and reproduction terms, but this effect can be reversed by droughts. Overall, a more positive water balance improves post-fire regeneration by enhancing growth and cone production. Thus, silvicultural treatments such as thinning should be applied by taking into account the post-fire water balance to maximise growth and cone production in Aleppo pine stands. Our findings illustrate how climate warming could hamper post-fire tree regeneration by aggravating drought stress.

Management of burnt forests is a topic that should include monitoring of burnt areas immediately after burning, in order to implement emergency actions that ensure conditions for ecosystem recovery. However, if excessive regeneration is observed, early silvicultural treatments have to be implemented to assist the natural recovery of the ecosystem. This paper discusses the effects of silvicultural management in two burnt areas naturally regenerated. One of the study areas was located in southern Albaceteprovince, covered of Aleppopine (Pinus halepensis Mill.) stands that were burnt in summer 1994. The other area was located in eastern Cuenca province, showing Holm oak (Quercus ilex L. ssp. ballota (Desf.) Samp) stands burnt twice in summer 1993 and 2001. The objective of the current study was to monitor the biomass recovery and carbon stock in two different ways: direct field sampling and calculation of stocks by using available published datasets. Direct sampling showed that in 2010 (nine years after fire), lower amounts of carbon were stored in the young Holm oak standards which were not totally recovered from previous thinning, carried out two years ago. In 2010, sixteen years after the fire and nine after thinning, high intensity thinning contributed to improve the total amount of carbon stock in tree biomass in theAleppo pine stands. In addition, values for unthinned areas were similar to those obtained from the Third Spanish National Forest Inventory. In this study we highlight the interest of implementing a classical tool of silvicultural management in the adaptive forest management of regenerating areas. We propose to consider the inclusion of young regenerated stands in carbon stocks, at least at province and regional level., El manejo de las masas forestales incendiadas debe incluir un seguimiento desde el primer momento tras el incendio, optimizando la implementación de medidas urgentes que aseguren unas condiciones mínimas para la regeneración natural del ecosistema. Sin embargo, ante una regeneración excesiva, se deben plantear tratamientos selvícolas tempranos como apoyo a la recuperación del ecosistema. En este trabajo se discuten los efectos del clareo temprano en dos zonas incendiadas y regeneradas de manera natural situadas en el este peninsular, una en el sur de Albacete con masas de pino carrasco (Pinus halepensis Mill.) quemadas en el verano de 1994, y otra al este de Cuenca, con masas de carrasca (Quercus ilex L. ssp. ballota (Desf.) Samp), quemadas repetidamente en los veranos de 1993 y 2001. El objetivo de este estudio es monitorizar la recuperación de biomasa y el almacenamiento de carbono de estas masas naturales, mediante muestreo directo en campo y por cálculo de existencias obtenidas de bases de datos públicas. El método directo mostró que la disminución del carbono almacenado en las especies estudiadas fue debido a la reducción inicial del número de árboles, que en los encinares no se había recuperado totalmente en 2010 (dos años después del tratamiento y nueve tras incendio). En 2010, dieciséis años después del incendio y seis tras el tratamiento silvícola, obtuvimos que en el pinar, los clareos de alta intensidad mejoraron la capacidad de la masa arbórea para almacenar carbono. Además, los valores de carbono almacenado en la biomasa arbórea en áreas no tratadas eran comparables a los valores del Tercer Inventario Forestal Nacional. Por tanto, se pone de relieve el interés del uso de la implementación de esta herramienta de manejo selvícola en un manejo forestal adaptativo y se propone la inclusión de masas jóvenes en regeneración dentro de los cálculos de almacenaje de carbono, al menos a niveles provinciales y regionales.

[EN] This report describes an international summer course, "Tree Rings, Climate, Natural Resources, and Human Interaction", held in Valsain, Spain, in summer of 2012. The course, with 14 participants from three countries (Spain, Algeria, and Russia), included basic training in dendrochronology skills as well as applied projects in dendroclimatology, dendroecology and dendrogeomorphology.

In the current framework of climate change, the Mediterranean Basin fire regime is being modified. In the southeast of the Iberian Peninsula, Pinus halepensis is the principal tree species of forest stands. A revision of the post-fire Aleppo pine stands evolution has been performed, showing different behaviours in its natural regeneration. Regeneration is not always guaranteed, promoting whether a large regeneration or an absence of it requiring forest restoration. Both cases need monitoring in the short, medium and long term, in order to improve its post-fire management, and therefore assess which treatments are suitable to carry out at each time., En el contexto actual de cambio global y en particular, de cambio climático, el régimen de incendios en la Cuenca Mediterránea se está viendo modificado. En el sureste de la Península Ibérica Pinus halepensis es la especie arbórea principal de las masas forestales. En este trabajo se ha realizado una revisión sobre la evolución de las masas de pino carrasco después de incendio, observando diferentes comportamientos en su regeneración natural. Esta regeneración no siempre está garantizada, dando lugar a una elevada densidad de brinzales o bien una ausencia total de los mismos pudiendo requerir una restauración forestal. Ambos casos demandan un seguimiento de la masa a corto, medio y largo plazo, para mejorar su manejo post-incendio, y así valorar qué tipo de tratamientos son precisos llevar a cabo en cada momento.