Jet stream position explains regional anomalies in European beech forest productivity and tree growth

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. Here the authors show that extremes in the summer jet stream position over Europe create a beech forest productivity dipole between northwestern and southeastern Europe and can result in regional anomalies in forest carbon uptake and growth.This work was supported by Fundacio La Caixa through the Junior Leader Program (LCF/BQ/LR18/11640004) and the Universidad Politécnica de Madrid through the Programa Propio (PINV-18-SBSYN2-105-F1TXYR). The following authors acknowledge funding support. I.D.L.: Agnese N. Haury Visiting Scholar & Trainee Fellowship (Laboratory of Tree-Ring Research, University of Arizona), the Mobility Award Jose Castillejo, Ministry of Education, Spanish Government (CAS19/00331) and the Programa de Ayudas Beatriz Galindo, Secretaría de Estado de Universidades, Investigación, Desarrollo e Innovación (#BG20/00065). V.T.: National Science Foundation CAREER grant (AGS-1349942). B.A.: Spanish Ministry of Science and Innovation through the JeDiS project (RTI-2018-096402-B-I00). F.B.: project "Inside out" (#POIR.04.04.00-00-5F85/18-00) funded by the HOMING program of the Foundation for Polish Science co-financed by the European Union under the European Regional Development Fund. AB, AM, CSZ: Bavarian Ministry of Science and the Arts in the context of the Bavarian Climate Research Network (BayKliF). A.H.: PinCaR project (UHU-1266324) by ERD Funds, Andalucía Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020. EM-S: Swiss National Science Foundation project TRoxy (No. 200021_175888). A.S.J.: Natural Environment Research Council grants NE/V00929X/1 and NE/S010041/1. J.K., L.M., M.M.T., R.W., M.W.: research training group RESPONSE funded by the German Research Council (DFG Fi 846/8-1, DFG GRK2010). AMP: Romanian Ministry of Research, Innovation, and Digitization, Project-PN-19070506/Ctr. no. 12N/2019. I.C.P.: grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI within PNCDI III (PN-III-P4-ID-PCE-2020-2696). R.S.S.: DendrOlavide I (EQC2018-005303-P), Ministry of Science, Innovation and Universities, Spain; DendrOlavide II (IE19_074 UPO), VURECLIM (P20_00813) and VULBOS (UPO-1263216). T.L.: Slovenian Research Agency-research core funding no. P4-0107 Program research group "Forest Biology, Ecology and Technology". We thank Virgilio Gómez-Rubio for assistance and advice on the LMM development. We thank Christoph Dittmar, Wolfram Elling, and numerous students of the University of Applied Sciences Weihenstephan-Triesdorf for providing European beech tree-ring chronologies

Identification of Old-Growth Mediterranean Forests Using Airborne Laser Scanning and Geostatistical Analysis

The protection and conservation of old-growth forests (OGFs) are becoming a global concern due to their irreplaceability and high biodiversity. Nonetheless, there has been little research into the identification and characterization of OGFs of the oldest tree species in Mediterranean areas. We used forest inventory data, low-density airborne laser scanning (ALS) metrics, and geostatistical analysis to estimate old-growth indices (OGIs) as indicators of old-growth forest conditions. We selected a pilot area in European black pine (Pinus nigra subsp. salzmannii) ecosystems where the oldest known living trees in the Iberian Peninsula are found. A total of 756 inventory plots were established to characterize standard live tree and stand attributes. We estimated several structural attributes that discriminate old growth from younger age classes and calculated different types of OGI for each plot. The best OGI was based on mean tree diameter, standard deviation of tree diameter, and stand density of large trees (diameter > 50 cm). This index is useful for assessing old-growthness at different successional stages (young and OGFs) in Mediterranean black pine forests. Our results confirm that the estimation of OGIs based on a combination of forest inventory data, geostatistical analysis, and ALS is useful for identifying OGFsThis work was supported by the following projects: “Iberian Heritage Project”, funded by the Netherlands Organization for Scientific Research (NWO, project number 236-61-001), National Geographic Society-Waitts Grant Program (“Millennia old black pines and Andalusian Cultural Heritage to unravel human-environment interactions in the Western Mediterranean”, W329-14), the Biodiversity Foundation of the Ministry of Agriculture and Fisheries, Food and Environment (“Bosques viejos frente al cambio climático. Vulnerabilidad, capacidad adaptativa e implicaciones frente a la gestión forestal”, PRCV00433) and Ministry of Economy, Industry and Competitiveness (MINECO) (“El final del ciclo envejecimiento, mortalidad y regeneración en pinares mediterráneos, y su papel en la adaptación ante un ambiente en cambio (OLDPINE), AGL2017-83828-C2-2-R). The Ministry of Agriculture and Environment of the Regional Government of Andalusia provided the AF forest inventory data. AH have been supported by PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020). We thank the Forest Service at Cazorla, Segura y Las Villas Natural Park, for providing the forest inventory data and for their interest in the project. Debería de ser más completo: We are grateful to Teresa Moro from the Natural Park, and Valentin Badillo from the Cazorla, Segura and Las Villas Natural Park, for their interest and support. The forestry engineering students Raúl García-Raga and Carlos Maeztu (University of Huelva), and Alex Boninsegna (University of Padova) contributed to the fieldwork as part of their final thesis undergraduate studie

Which matters more for wood traits in Pinus halepensis Mill., provenance or climate?

This is a pre-copyedit version of an article published in Annal of Forest Science. The final authenticated version is available online at: http://doi.org/10.1007/s13595-020-00956-yContext: It is essential to disentangle the influence of climate from the effect of provenance on inter- and intra-annual wood traits to identify populations’ responses to climate changes. This will be even more relevant in the drought-prone Mediterranean region, where species have high genetic differentiation among populations. Aims: We investigated the effects of provenance and climate driving Pinus halepensis Mill. wood traits, as imprinted phenotypic adaptations to the Mediterranean climate. Methods: Inter- and intra-annual wood trait variation (ring-, early-, and latewood width, wood density) was studied by microdensitometry in 8 provenances from Spain, France, Greece, and Italy in a common-garden experiment. We related wood traits and density fluctuations with inter-annual climate variations at the trial site and the provenance origin. Results: Provenances showed distinct responses to climate regarding tree growth, wood density, and intra-annual fluctuations. Density fluctuations in latewood were more frequent than in earlywood. Climate at the provenance origin was a more important force for density fluctuations than climatic variations at the planting site, with different trends between coastal and inland provenances, and higher frequency of latewood fluctuations in provenances from arid and semiarid sites. Conclusion: Differences in P. halepensis wood density fluctuations confirmed the imprinted origin provenance control in response to climate variations and indicated a relation with local adaptation of these xylem anatomical features. Moreover, the position of these fluctuations in rings reflected the high plasticity of P. halepensis to cope with high intra-seasonal variability of climatic conditions. This underlines the importance of considering tree-ring features for the selection of provenances in reforestation material for conservation and silvicultural programs.PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014–2020); SFRH/BPD/105656/2015, (SFRH/ BPD/111307/2015), FCT with funds from POPH (Portuguese Operational Human Potential Program), QREN Portugal (Portuguese National Strategic Reference Framework), FSE (European Social Fund). Spanish Ministry of Economy, Industry and Competitiveness IJCI-2015-25845, MCIU funds, CoMo-ReAdapt (CGL2013-48843-C2-1-R) project, RTI2018-096884-B-C31 and RTI2018-096884-B-C33 Ministry of Science, Innovation and Universities, VULBOS project UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014–2020

Novel approach to assessing residual biomass from pruning: A case study in Atlantic Pinus pinaster Ait. timber forests

Forestry residual biomass from pruning operations is an important, though little studied, potential resource. Residues normally remain in the stand, since tools for their accurate quantification do not exist and it has no particular end use. Traditional tree biomass estimation models consider the whole-tree, but estimating pruned biomass requires the development of more specific equations. This work provides a modelling approach for assessing biomass along the stem and the corresponding residual biomass from forest pruning, and quantitative results from different pruning intensities in Pinus pinaster Ait. are presented. Two types of models were considered: allometric biomass equations (whole-tree) and biomass ratio equations (tree by height along the stem), and the 2-parameter Weibull distribution function resulted in the best characterization. Diameter at breast height was the best explanatory variable in all equations, and model accuracy increased when models were combined with total tree height for the tree stem and thicker branches, or with crown ratio for the remaining tree crown components. This study provides a powerful tool to estimate residual pruned biomass, enabling its better management as a valuable source of bioenergy, as well as the importance in nutrient balance and fire risk which it plays in a sustainable forestry productionWe thank the Forest Services of the Government of the Principality of Asturias for access to the forests used in this study and for financial support. Thank you to people from CETEMAS (L. González, M. García, P. Vallejo) and SERIDA (J.C. Hernández) for their participation in the fieldwork. Thank you to Ronnie Lendrum for reviewing the English and FORRISK project (Interreg IV B SUDOE 2007–2013) for its support during data analysis. Andrea Hevia was financially supported during fieldwork and data analysis by the Spanish Ministry of Education and Science through the FPU scholarship program (Reference AP2006-03890)S

Assessing the effect of pruning and thinning on crown fire hazard in young Atlantic maritime pine forests

Management of fuel to minimize crown fire hazard is a key challenge in Atlantic forests, particularly for pine species. However, a better understanding of effectiveness of silvicultural treatments, especially forest pruning, for hazard reduction is required. Here we evaluate pruning and thinning as two essential silvicultural treatments for timber pine forests. Data came from a network of permanent plots of young maritime pine stands in northwestern Spain. Vertical profiles of canopy bulk density were estimated for field data and simulated scenarios of pruning and thinning using individual tree biomass equations. Analyses of variance were conducted to establish the influence of each silvicultural treatment on canopy fuel variables. Results confirm the important role of both pruning and thinning in the mitigation of crown fire hazard, and that the effectiveness of the treatments is related to their intensity. Finally, models to directly estimate the vertical profile of canopy bulk density (CBD) were fitted using the Weibull probability density function and usual stand variables as regressors. The models developed include variables sensitive to pruning and thinning interventions and provide useful information to prevent extreme fire behavior through effective silvicultureWe thank the Forest Services of the Government of the Principality of Asturias for financial support and access to the forests used in this study. Funding during data analysis was provided by projects SCALyFOR (AGL2013-46028-R), GEPRIF (RTA2014-00011-C06-04), PLURIFOR (SOE1/P4/F0112 Interreg SUDOE) and FORRISK (SOE3/P2/F523 Interreg IV B SUDOE). Andrea Hevia was financially supported during fieldwork and data analysis by the Spanish Ministry of Education and Science through the FPU scholarship program (Reference AP2006-03890)S

Modelling the vertical distribution of canopy fuel load using national forest inventory and low-density airbone laser scanning data

The fuel complex variables canopy bulk density and canopy base height are often used to predict crown fire initiation and spread. Direct measurement of these variables is impractical, and they are usually estimated indirectly by modelling. Recent advances in predicting crown fire behaviour require accurate estimates of the complete vertical distribution of canopy fuels. The objectives of the present study were to model the vertical profile of available canopy fuel in pine stands by using data from the Spanish national forest inventory plus lowdensity airborne laser scanning (ALS) metrics. In a first step, the vertical distribution of the canopy fuel load was modelled using the Weibull probability density function. In a second step, two different systems of models were fitted to estimate the canopy variables defining the vertical distributions; the first system related these variables to stand variables obtained in a field inventory, and the second system related the canopy variables to airborne laser scanning metrics. The models of each system were fitted simultaneously to compensate the effects of the inherent cross-model correlation between the canopy variables. Heteroscedasticity was also analyzed, but no correction in the fitting process was necessary. The estimated canopy fuel load profiles from field variables explained 84% and 86% of the variation in canopy fuel load for maritime pine and radiata pine respectively; whereas the estimated canopy fuel load profiles from ALS metrics explained 52% and 49% of the variation for the same species. The proposed models can be used to assess the effectiveness of different forest management alternatives for reducing crown fire hazardWe are grateful to the Galician Government and European Social Fund (Official Journal of Galicia—DOG n° 52, 17/03/2014, p. 11343, exp: POS-A/2013/049) for financing the postdoctoral research stays of Dr Eduardo González-Ferreiro at different institutions. Copyright of LiDAR data, Instituto Geográfico Nacional-Xunta de GaliciaS