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The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30 in modelled gross primary productivity and 50 in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.

The mechanistic pathways connecting ocean-atmosphere variability and terrestrial productivity are well-established theoretically, but remain challenging to quantify empirically. Such quantification will greatly improve the assessment and prediction of changes in terrestrial carbon sequestration in response to dynamically induced climatic extremes. The jet stream latitude (JSL) over the North Atlantic-European domain provides a synthetic and robust physical framework that integrates climate variability not accounted for by atmospheric circulation patterns alone. Surface climate impacts of north-south summer JSL displacements are not uniform across Europe, but rather create a northwestern-southeastern dipole in forest productivity and radial-growth anomalies. Summer JSL variability over the eastern North Atlantic-European domain (5-40E) exerts the strongest impact on European beech, inducing anomalies of up to 30% in modelled gross primary productivity and 50% in radial tree growth. The net effects of JSL movements on terrestrial carbon fluxes depend on forest density, carbon stocks, and productivity imbalances across biogeographic regions.

En el presente trabajo se ha llevado a cabo el estudio de la influencia del clima en el crecimiento secundario de las masas de encina (Quercus ilex subsp. ilex) del Parque Natural del Montnegre y el Corredor, Barcelona. Se enmarca en un convenio de colaboración ente el INIA y la Diputación de Barcelona. La finalidad de este convenio es conocer el comportamiento de las masas del Parque para poder gestionarlas de forma adecuada, dado que los encinares de esta zona presentan la singularidad de ser gestionados como masas irregulares, a diferencia de los del resto de la Península Ibérica. La metodología utilizada para establecer las relaciones entre el clima y el crecimiento ha sido el análisis por correlaciones simples. Para ello se ha generado una cronología o serie media que cubre un periodo de 44 años (1967-2011) a partir de 19 rodajas cortadas a la altura del diámetro normal. Las muestras provienen de los árboles dominantes de parcelas de 10 metros de radio distribuidas a lo largo de toda el área de estudio. Una vez seleccionadas las muestras se procedió a su datación, sincronización y estandarización. Finalmente, se determinó el crecimiento medio por año en una cronología o serie media representativa de toda la masa. Se establecieron las correlaciones mensuales y estacionales entre los crecimientos medios anuales de dicha cronología y las dos variables climáticas que se consideraron las más relevantes: precipitación y temperatura. Para ellos se utilizó un paquete del software libre R, pdlR, en la elaboración de la cronología y Microsoft Excel para hallar las correlaciones. Los resultados muestran que la temperatura no resulta determinante en el crecimiento de las encinas analizadas en el área de estudio. Sin embargo, si se han establecido correlaciones para la precipitación. Se dan valores significativos positivos para los meses de septiembre y octubre del año anterior al crecimiento, así como para la precipitación acumulada de los grupos de meses que los contienen

Old-growth forests, particularly those located at the interface between different bioregions, are unevaluable sources of long-term vegetation dynamics and historical stand response to natural and anthropogenic disturbances. Although old-growth forests are scarce, the information gathered studying them may assist forest ecosystem restoration and management under forthcoming climate and land-use changes. We analysed how complementary dynamics of a mixed old-growth forest composed by temperate (Fagus sylvatica, Quercus petraea) and submediterranean (Quercus pyrenaica) tree species were driven in response to global changes in the last two centuries. The old-growth forest, named El Hayedo de Montejo, is located at the interface between the Mediterranean and temperate bioregions in the centre of the Iberian Peninsula. The populations of temperate species growing in El Hayedo de Montejo (F. sylvatica and Q. petraea) are at the dry and warm edges of their natural distribution area in Europe, whereas the submediterranean species Q. pyrenaica is at the core of the distribution range. In order to analyse the long-term dynamics, we developed basal area increment and disturbance chronologies for each of the tree species under study. Furthermore, we assessed the climate influence on tree growth during the most recent decades. Our results reveal historical shifts in forest dominance (as reflected by growth) induced by changes in climate and forest management between temperate and sub-Mediterranean species. This was particularly noticeable for F. sylvatica and Q. pyrenaica the least and most drought-tolerant species, respectively. A reduction in growth of F. sylvatica unprecedented in the context of the last two hundred years was observed during the last decades concurrent with forest densification and marked changes in climate. Conversely, both oak species seem to be better suited to current environmental conditions as expressed by increasing growth rates.

The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 1901 to 2000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and land– atmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase in iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetation–climate feedbacks are currently still poorly constrained by observational data.