Links between climate, drought and minimum wood density in conifers

As the global climate warms, increased aridity is expected to become a major determinant of forest productivity and tree growth. In gymnosperms, wood density quantified at seasonal to annual scales can be related to changes in tracheid lumen size due to alterations in soil water availability. In this way, minimum wood density (MND) has been shown to respond negatively to early growing-season precipitation in several conifers because dry conditions reduce tracheid lumen size and consequently increase MND. We investigated if this relationship between spring precipitation and MND applies to four conifer species (Abies alba, Pinus sylvestris, Pinus nigra, Juniperus thurifera) in NE Spain from mesic (A. alba, P. sylvestris) to xeric (P. nigra, J. thurifera) conditions. We further assessed how climate, precipitation, and drought-affected tree-ring width (TRW) and MND at several time scales to test if water shortage in spring increases MND and decreases TRW over time and seasonally. Lastly, we quantified the post-drought MND recovery. We found the strongest negative correlations between MND and spring precipitation in P. nigra followed by J. thurifera. In these two species, the associations between MND and 9-month long droughts peaked in early spring (P. nigra, r=−0.73; J. thurifera, r=−0.50). Juniperus thurifera presented a better post-drought recovery (decrease in MND), followed by P. nigra and P. sylvestris. We conclude that MND is a reliable and accurate proxy of drought severity during spring in conifers subjected to seasonal water shortage. MND can be used as an early-warning indicator of short- and long-term changes in the responses of trees to water shortage.Spanish Ministry of Economy “Fundiver” project (CGL2015-69186-C2-1-R). FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimento, Empresas y Universidad 2014–2020 (PinCaR project UHU-1266324)

Growth and resilience responses of Scots pine to extreme droughts across Europe depend on pre‐drought growth conditions

Global climate change is expected to further raise the frequency and severity of extreme events, such as droughts. The effects of extreme droughts on trees are difficult to disentangle given the inherent complexity of drought events (frequency, severity, duration, and timing during the growing season). Besides, drought effects might be modulated by trees’ phenotypic variability, which is, in turn, affected by long‐term local selective pressures and management legacies. Here, we investigated the magnitude and the temporal changes of tree‐level resilience (i.e., resistance, recovery, and resilience) to extreme droughts. Moreover, we assessed the tree‐, site‐, and drought‐related factors and their interactions driving the tree‐level resilience to extreme droughts. We used a tree‐ring network of the widely distributed Scots pine (Pinus sylvestris ) along a 2800 km latitudinal gradient from southern Spain to northern Germany. We found that the resilience to extreme drought decreased in mid‐elevation and low productivity sites from 1980‐1999 to 2000‐2011 likely due to more frequent and severe droughts in the later period. Our study showed that the impact of drought on tree‐level resilience was not dependent on its latitudinal location, but rather on the type of sites trees were growing at and on their growth performances (i.e., magnitude and variability of growth) during the pre‐drought period. We found significant interactive effects between drought duration and tree growth prior to drought, suggesting that Scots pine trees with higher magnitude and variability of growth in the long term are more vulnerable to long and severe droughts. Moreover, our results indicate that Scots pine trees that experienced more frequent droughts over the long‐term were less resistant to extreme droughts. We therefore conclude that the physiological resilience to extreme droughts might be constrained by their growth prior to drought, and that more frequent and longer drought periods may overstrain their potential for acclimation.Marie Skłodowska-Curie Individual Fellowship (PROJECT ID: 749051-REFOREST), Postdoctoral grant (IJCI-2015-25845, FEDER funds), RTI2018-096884-B-C31, RTI2018-096884-B-C33 projects (Ministry of Ministry of Science, Innovation and Universities, Spain), VULBOS project (UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020), PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020), Bavarian Ministry of Science, Bavarian Climate Research Network (bayklif). project DENDROKLIMA by the German Waldklimafond (FKZ 28W-C-4-077-01), ST327 Bavarian State Ministry for Food, Agriculture, and Forestry. Landesforst MecklenburgVorpommern, Landeskompetenzzentrum Forst Eberswalde and Nordwestdeutsche Forstliche Versuchsanstalt

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

Influencia de la poda en el desarrollo de masas de Pinus radiata D. Don y Pinus pinaster Aiton en Asturias

Esta tesis evaluó la influencia de diferentes intensidades de poda sobre el crecimiento, desarrollo y persistencia de masas regulares jóvenes de Pinus radiata D. Don y Pinus pinaster Aiton en Asturias, dentro de una selvicultura sostenible enfocada a la producción de madera de calidad

Radial Growth and Wood Density Reflect the Impacts and Susceptibility to Defoliation by Gypsy Moth and Climate in Radiata Pine

Drought stress causes a reduction in tree growth and forest productivity, which could be aggravated by climate warming and defoliation due to moth outbreaks. We investigate how European gypsy moth (Lymantria dispar dispar L., Lepidoptera: Erebidae) outbreak and related climate conditions affected growth and wood features in host and non-host tree species in north-western Spain. There, radiata pine (Pinus radiata D. Don) plantations and chestnut (Castanea sativa Mill.) stands were defoliated by the moth larvae, whereas Maritime pine (Pinus pinaster Ait.) was not defoliated. The gypsy moth outbreak peaked in 2012 and 2013, and it was preceded by very warm spring conditions in 2011 and a dry-warm 2011–2012 winter. Using dendrochronology we compared growth responses to climate and defoliation of host species (radiata pine, chestnut) with the non-host species (Maritime pine). We also analyzed wood density derived from X-ray densitometry in defoliated and non-defoliated trees of radiata pine. We aimed to: (i) disentangle the relative effects of defoliation and climate stress on radial growth, and (ii) characterize defoliated trees of radiata pine according to their wood features (ring-width, maximum and minimum density). Radial growth during the outbreak (2012–2013) decreased on average 74% in defoliated (>50% of leaf area removed) trees of radiata pine, 43% in defoliated trees of chestnut, and 4% in non-defoliated trees of Maritime pine. After applying a BACI (Before-After-Control-Impact) type analysis, we concluded that the difference in the pattern of radial growth before and during the defoliation event was more likely due to the differences in climate between these two periods. Radiata pines produced abundant latewood intra-annual density fluctuations in 2006 and 2009 in response to wet summer conditions, suggesting a high climatic responsiveness. Minimum wood density was lower in defoliated than in non-defoliated trees of radiata pine prior to the outbreak, but increased during the outbreak. The pre-outbreak difference in minimum wood density suggests that the trees most affected by the outbreak produced tracheids with wider lumen and were more susceptible to drought stress. Results of this study illustrate (i) that the pattern of radial growth alone may be not a good indicator for reconstructing past defoliation events and (ii) that wood variables are reliable indicators for assessing the susceptibility of radiata pine to defoliation by the gypsy moth

Climate warming predispose sessile oak forests to drought-induced tree mortality regardless of management legacies

Climate warming-related drought could become a major driver of large-scale forest dieback. However, little is known about how past management legacies modulate the climate-growth responses during recent dieback episodes in central European oak forests. Here, we examine the role played by past management –unmanaged old-growth vs. managed forests– in recent tree mortality events occurring in Quercus petraea (Matt.) Liebl. stands across large areas of western Romania. We analyze how stand structure (tree size, competition) and climatic factors (drought, temperature and precipitation) drive tree radial growth patterns in neighboring standing dead and living trees. We analyzed basal area increments (BAI) trends, past management legacies and climate- and drought-growth relationships during the 20th century to distinguish the roles and interactions on recent warming-induced dieback. We observed that temperature rises and changes in atmospheric water demand during growing season let to increasing drought stress during the late 20th century affecting both managed and unmanaged forests. Dead trees from old-growth and managed forests showed lower growth than living trees after dieback onset. In both forests, dead and living trees displayed divergent growth patterns after dry 1980s, indicating that dieback was triggered by severe extreme conditions. Dead trees from managed stands experienced significant stronger growth reductions after 1980s though they experienced less tree-to-tree competition than dead trees in old-growth forest. High stand density negatively drove growth and enhanced climate sensitivity in old-growth stands. Competition acted synergistically with climate warming and drought causing tree mortality regardless of the management legacies in of Q. petraea forests. Our retrospective assessment of growth rates in relation with climate and structure changes offers valuable information for further forest conservation and management decisions of Q. petraea forests. These findings highlight the importance of past uses legacies driving recent forest dieback in temperate oak forests, making them more vulnerable under forecasted climate-warming related droughts in central Europe.Nemoral Forests under Climate Extremes (NEMKLIM Project, grant number 3517861300), German Federal Agency for Nature Conservation (Bundesamt für Naturschutz,BfN), German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany, project PN 19070506, Romanian National Authority from Scientific Research and Innovation, Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020- 2696, within PNCDI III. projects VUL-BOS project (UPO-1263216 and PinCaR (UHU-1266324), FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020), project LESENS (RTI2018-096884-B-C33), Spanish Ministry of Science, Innovation and Universities.This work was supported by NEMKLIM project: Nemoral Forests under Climate Extremes (NEMKLIM Project, grant number 3517861300), financed by the German Federal Agency for Nature Conservation (Bundesamt für Naturschutz,BfN) and the German Federal Ministry for the Environment, Nature Conservation and Nuclear Safety, Germany and by project PN 19070506 financed by Romanian National Authority from Scientific Research and Innovation. I.C. Petritan was supported by a grant of the Romanian Ministry of Education and Research, CNCS-UEFISCDI, project number PN-III-P4-ID-PCE-2020- 2696, within PNCDI III. R. S ´anchez-Salguero was supported by VUL-BOS project (UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020) and LESENS (RTI2018-096884-B-C33) project from the Spanish Ministry of Science, Innovation and Universities. A. Hevia was supported by PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020). We are also grateful to Lucian Toiu, Nicu Tudose, George Sarbu and Gheorghe Stefan for help in collecting field data. We appreciate the permission and logistic support given by staff of the Barzava and Codrii Beiusului si Sfanta Maria Forest Districts, we are grateful especially to eng. Gheorghe Marc and eng. Jeno Ferko. The authors declare no conflicts of interest

Improving spatial synchronization between X-ray and near-infrared spectra information to predict wood density profiles

Wood density is one of the most important physical properties of the wood, used in improvement programs for wood quality of major timber species. Traditional core sampling of standing trees has been widely used to assess wood density profiles at high spatial resolution by X-ray microdensitometry methods, but alternative methods to predict wood properties quality are also needed. Near-infrared (NIR) spectroscopy, a non-destructive technique, is being increasingly used for wood property assessment and has already been demonstrated to be able to predict wood density. However, the estimation of wood density profiles by NIR has not yet been extensively studied, and improved models using spectra information (NIR) and X-ray data need to be developed. To this end, partial least square regression (PLS-R) models for predicting wood density were developed at a 1.4 mm spatial resolution on Pinus pinaster wood cores, with an improved spatial synchronization along the tangential and radial directions of the strip, between X-ray data and NIR spectra. The validation of the best model showed a high coefficient of determination (0.95), low error (0.026) and no outlier. Compression wood samples were not detected as outliers and were correctly predicted by the model. However, pith spectra were detected as outliers and its predicted values were overestimated by 33% due to unusual spectra suggesting a diverse chemical composition. The results suggest that NIR-PLS models obtained can be used for screening maritime pine wood density profiles along the radii at 1.4 mm spatial resolutioninfo:eu-repo/semantics/publishedVersio

Radial growth and wood density reflect the impacts and susceptibility to defoliation by gypsy moth and climate in radiata pine

[EN] Drought stress causes a reduction in tree growth and forest productivity, which could be aggravated by climate warming and defoliation due to moth outbreaks. We investigate how European gypsy moth (Lymantria dispar dispar L., Lepidoptera: Erebidae) outbreak and related climate conditions affected growth and wood features in host and non-host tree species in north-western Spain. There, radiata pine (Pinus radiata D. Don) plantations and chestnut (Castanea sativa Mill.) stands were defoliated by the moth larvae, whereas Maritime pine (Pinus pinaster Ait.) was not defoliated. The gypsy moth outbreak peaked in 2012 and 2013, and it was preceded by very warm spring conditions in 2011 and a dry-warm 2011–2012 winter. Using dendrochronology we compared growth responses to climate and defoliation of host species (radiata pine, chestnut) with the non-host species (Maritime pine). We also analyzed wood density derived from X-ray densitometry in defoliated and non-defoliated trees of radiata pine. We aimed to: (i) disentangle the relative effects of defoliation and climate stress on radial growth, and (ii) characterize defoliated trees of radiata pine according to their wood features (ring-width, maximum and minimum density). Radial growth during the outbreak (2012–2013) decreased on average 74% in defoliated (>50% of leaf area removed) trees of radiata pine, 43% in defoliated trees of chestnut, and 4% in non-defoliated trees of Maritime pine. After applying a BACI (Before-After-Control-Impact) type analysis, we concluded that the difference in the pattern of radial growth before and during the defoliation event was more likely due to the differences in climate between these two periods. Radiata pines produced abundant latewood intra-annual density fluctuations in 2006 and 2009 in response to wet summer conditions, suggesting a high climatic responsiveness. Minimum wood density was lower in defoliated than in non-defoliated trees of radiata pine prior to the outbreak, but increased during the outbreak. The pre-outbreak difference in minimum wood density suggests that the trees most affected by the outbreak produced tracheids with wider lumen and were more susceptible to drought stress. Results of this study illustrate (i) that the pattern of radial growth alone may be not a good indicator for reconstructing past defoliation events and (ii) that wood variables are reliable indicators for assessing the susceptibility of radiata pine to defoliation by the gypsy mothSIFunding for this research was provided by the Local Government of Cubillos del Sil (Spain) through the contract Seguimiento y bases para la gestión de las masas forestales afectadas por defoliación de Lymantria dispar en el municipio de Cubillos del Sil

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

A multi-proxy framework to detect insect defoliations in tree rings: a case study on pine processionary

Assessing and reconstructing the impacts of defoliation caused by insect herbivores on tree growth, carbon budget and water use, and differentiating these impacts from other stresses and disturbances such as droughts requires multi-proxy approaches. Here we present a methodological framework to pinpoint the impacts of pine processionary moth (Thaumetopoea pityocampa), a major winter-feeding defoliator, on tree cover (remote-sensing indices), radial growth and wood features (anatomy, density, lignin/carbohydrate ratio of cell walls, δ13C and δ18O of wood cellulose) of drought-prone pine (Pinus nigra) forests in north-eastern Spain. We compared host defoliated (D) and coexisting non-defoliated (ND) pines along with non-host oaks (Quercus faginea) following a strong insect outbreak occurring in 2016 at two climatically contrasting sites (cool-wet Huesca and warm-dry Teruel). Changes in tree-ring width and wood density were analyzed and their responses to climate variables (including a drought index) were compared between D and ND trees. The Normalized Difference Infrared Index showed reductions due to the outbreak of –47.3% and –55.6% in Huesca and Teruel, respectively. The D pines showed: a strong drop in growth (–96.3% on average), a reduction in tracheid lumen diameter (–35.0%) and lower lignin/carbohydrate ratios of tracheid cell-walls. Both pines and oaks showed synchronous growth reductions during dry years. In the wet Huesca site, lower wood δ13C values and a stronger coupling between δ13C and δ18O were observed in D as compared with ND pines. In the dry Teruel site, the minimum wood density of ND pines responded more negatively to spring drought than that of D pines. We argue that multi-proxy assessments that combine several variables have the potential to improve our ability to pinpoint and reconstruct insect outbreaks using tree-ring data