Spatial structure of deciduous forest stands with contrasting human influence in northwest Spain

Five contrasting deciduous forest stands were studied to characterize the spatial structural variability in human-influenced forests. These stands are representative of cultural forest types widely represented in western Europe: one plantation, two coppices, one wood-pasture forest and one high forest stand. All stems with DBH > 5 cm were measured and mapped, and stem DBH distributions, spatial structure of DBH, spatial point patterns and spatial associations were analysed. Spatial autocorrelation for DBH was calculated with Moran’s I correlograms and semivariograms. Complete spatial randomness hypothesis for spatial point patterns, and both independence and random labelling hypotheses for spatial associations were analysed using Ripley’s K function. The results showed that tree sizes were conditioned by particular former management systems, which determined unimodal symmetric, positively skewed or compound DBH distributions. Spatial structure was more complex when human influence became reduced. Coppice stands showed clumped spatial patterns and independence among size classes, as a consequence of sexual and vegetative establishment of new stems in open areas. The largest clumping intensity was observed in the wood-pasture with an intermediate disturbance frequency and low inter-tree competition. The high forest stand displayed spatial traits consistent with the gap-dynamics paradigm, such as clumping of smaller trees, random arrangement of larger trees, negative association between juveniles and adults, and high structural heterogeneity. It can be expected that after cessation of human interference, coppices and wood-pastures would evolve to a more heterogeneous structure, probably with a higher habitat and species diversity.This research was partially supported by the Consejería de Medio Ambiente del Principado de Asturias (SV-PA-00-01).Peer reviewe

Spatio-temporal variation of early wood vessel features of Quercus robur L. along a climatic gradient in the northwestern iberian peninsula

Comunicación presentada en Rovaniemi (Finlandia) los días 13-18 de junio de 2010.Common European oak (Quercus robur L.) reaches its southwestern distribution limit in Europe close to the Northwestern Iberian Peninsula, where the transition to Mediterranean vegetation results in a progressive substitution of this species as xeric conditions increase. For this reason, xylem adaptations to drought conditions are relevant for the survival of these oaks, while their analysis by means of dendrochronological techniques can be useful to study their behavior in changing environments. For this work, we selected a network of 12 sites distributed all along Galicia (NW Spain), trying to characterize the transition to the Mediterranean climate within the region. Earlywood vessels were measured for 10 trees per site for a common period of 20 years, and combined into several growth variables combining vessel size and numbers (mean and maximum vessel area, number of vessels, total conductive area and conductivity), also considering the position within the ring. We used these data to build chronologies for each growth variable and site, which were compared by multivariate techniques. The results showed that vessel characteristics varied among sites according to the prevailing conditions along the gradient. Similarly, the comparison of time series provided a more detailed picture of the influence of climate on the adaptations of xylem anatomy. In summary, this works constitutes one of the first attempts to apply quantitative tree- ring anatomy to a network of site chronologies, and can be of relevance to the study of global chang

250-Year reconstruction of pollarding events reveals sharp management changes in Iberian ash woodlands

Producción CientíficaTree pollarding was a dominant management strategy of European forests for centuries creating open agroforestry landscapes with important cultural and environmental values. This traditional practice has been widely abandoned in last decades with a subsequent impact in terms of biodiversity and cultural loss. Central Spain hosts the largest and best-preserved area of pollarded narrow-leaved ash (Fraxinus angustifolia Vahl.) woodlands in Europe. The main aim of this research is to obtain rigorous historical records of pollarding frequency to get adequate information for traditional ash management. We used dendrochronological techniques to evaluate temporal changes of pollarding frequency and rotation length. We analysed the stand level synchrony and the effect of land property on pollarding activity from 322 trees growing in eight pollard stands in Central Spain. Pollarding events were unequivocally identified at tree level by a characteristic change in growth pattern. We identified 2426 tree-level pruning events with the first event dated in 1777. Historical pruning recurrence ranged between 5 and 10 years with higher pollarding frequency on private lands. Pruning events within each site were synchronous, suggesting the existence of a rotational schema within each stand. Pruning frequency decreased drastically in the 1970s matching with the depopulation of rural areas and the general abandonment of traditional practices. Pollarding practices have recovered in recent decades although with lower intensity and lacking the synchronic historical patterns. Providing technical and economic support to make this traditional activity profitably would have strong environmental revenue due the multiple ecosystem services provided by pollarded ashes.iuFOR Institute Unit of Excellence" of the University of Valladolid, funded by the Junta de Castilla y León and co-financed by the European Union (ERDF "Europe drives our growth") project (CLU-2019-01)Ministerio de Ciencia e Innovación y Agencia Estatal de Investigación - MCIN/AEI/10.13039/501100011033 project PROWARM (PID2020-118444GA-100),(IJC2019-040571-I),(grant PRE2018-084106)Junta de Castilla y León, projects, (VA171P20) and (IR2020-1-UVA08)Publicación en abierto financiada por el Consorcio de Bibliotecas Universitarias de Castilla y León (BUCLE), con cargo al Programa Operativo 2014ES16RFOP009 FEDER 2014-2020 DE CASTILLA Y LEÓN, Actuación:20007-CL - Apoyo Consorcio BUCL

Forgotten giants: Robust climate signal in pollarded trees

Producción CientíficaTree ring records are among the most valuable resources to create high-resolution climate reconstructions. Most climate reconstructions are based on old trees growing in inaccessible mountainous areas with low human activity. Therefore, reconstruction of climate conditions in lowlands is usually based on data from distant mountains. Albeit old trees can be common in humanized areas, they are not used for climate reconstructions. Pollarding was a common traditional management in Europe that enabled trees to maintain great vitality for periods exceeding the longevity of unmanaged trees. We evaluate the potential of pollarded deciduous oaks to record past climate signal. We sampled four pollarded woodlands in Central Spain under continental Mediterranean climate. We hypothesized that pollarded trees have a strong response to water availability during current period without pollarding management, but also in the period under traditional management if pruning was asynchronous among trees. Moreover, we hypothesized that if climate is a regional driver of oak secondary growth, chronologies from different woodlands will be correlated. Pollard oaks age exceeded 500 years with a strong response to Standardized Precipitation-Evapotranspiration Index (SPEI) from 9 to 11 months. Climate signal was exceptionally high in three of the sites (r2 = 0.443–0.655) during low management period (1962–2022). The largest fraction of this climate signal (≈70 %) could be retrieved during the traditional management period (1902–1961) in the three sites where pollarding was asynchronous. Chronologies were significantly correlated since the 19th century for all the studied period, highlighting a shared climate forcing. We identified critical points to optimize pollard tree sampling schema. Our results show the enormous potential of pollarded woodlands to reconstruct hydroclimate conditions in the Mediterranean with a fine spatial grain. Studying pollarded trees is an urgent task, since the temporal window to retrieve the valuable information in pollarded trees is closing as these giants collapse and their wood rots.Junta de Castilla y León-Consejería de Educación [IR2020-1-UVA08; VA171P20]EU LIFE Soria Forest Adapt [LIFE19 CCA/ES/001181]Ministerio de Ciencia e Innovación - AEI (IJC2019-040571-I)Ministerio de Ciencia e Innovación - AEI (PRE2018-084106

Vertical cliffs harbor millennia‐old junipers in the Canary Islands

Producción CientíficaThe ability of trees to endure for millennia, surpassing human lifetimes, and survive the most destructive human and natural hazards is astonishing. But what is the ecological role of tree longevity? Are old trees more than impressive nature wonders? Can ancient trees become effective genetic reservoirs able to recover bygone ecosystems? Oceanic islands are ideal ecosystems to address these questions, as they have experienced recent and intense human-induced environmental changes. In the Canary Islands in the northeastern Atlantic Ocean, human colonization since the fifth century BCE (Rodríguez-Varela et al., 2017) added logging, fire, and grazing pressure to a territory already experiencing regular volcanic activity. Tenerife Island is the most populated island of the Canary Islands archipelago and harbors the largest subalpine ecosystems in the entire Macaronesian Biogeographic Region. Woodlands in the Tenerife subalpine environment were once formed by the Canary Island juniper (Juniperus cedrus Webb. & Berthel.; hereafter juniper; Machado & Galván, 2012, García-Cervigón et al., 2019), but historical human pressure restricted its distribution to inaccessible spots, away from human activity, such as cliffs. [parte del texto]Comunidad de Madrid, Grant/Award Number: REMEDINAL TE-CM (S2018/EMT-4338)Junta de Castilla y León-Consejería de Educación, Grant/Award Numbers: (VA113G19), (VA171P20) y (IR2020-1-UVA08)Ministerio de Ciencia e Innovación, Grant/Award Numbers: LAUREL (PID2019-109906RA-I00), (PRE2018-084106) and PROWARM (PID2020-118444GA-100)Ministerio de Economía, Industria y Competitividad. Grant/Award Number: (IJC2019-040571-I)Secretaría de Estado de Investigación, Desarrollo e Innovación, Grant/Award Number: spRING (CGL2017-87309-P

CaptuRING: A do‐it‐yourself tool for wood sample digitization

Producción CientíficaStandard procedures to obtain high-quality images of wood samples have become a bottleneck in the digitization of dendrochronology. Digitization is currently dominated by flatbed scanners, but the use of these devices is limited by sample length and surface flatness. Although several solutions based on digital photography have been published, they lack effective digitization processes or are too expensive to be widely adopted. Free open-source software and hardware has emerged as an alternative to create research tools that combine reduced costs with high reliability. Here we present CaptuRING, an open-source tool for wood sample digitization combining a do-it-yourself hardware based on Arduino® with a DSLR camera and a free open-source software with an easy-to-use graphical user interface. We compared CaptuRing with image acquisition from a standard flatbed scanner Epson® V750PRO. CaptuRING outperforms scanner image resolution and sharpness, while it removes sample size limitations. Moreover, CaptuRing performs this task in less than half of the time needed by Epson® V750PRO flatbed scanner. CaptuRING emerges as a reliable and low-cost tool to capture high-resolution images of wood samples boosting current digitization processes. The combination of free open software and hardware empowers dendrochronology to advance in wood sample digitization.Junta de Castilla y León, project OUTBREAK (VA171P20) and (IR2020-1-UVA08)Ministerio de Ciencia, Innovación y Universidades, grant number (CGL2017-87309-P) (MGH PRE2018-084106) and project PROWARM (PID2020-118444GA-I00)Universidad Politécnica de Madrid (through Project RP200060107

Tree-ring distinctness, dating potential and climatic sensitivity of laurel forest tree species in Tenerife Island

Producción CientíficaMacaronesian laurel forests are the only remnants of a subtropical palaeoecosystem dominant during the Tertiary in Europe and northern Africa. These biodiverse ecosystems are restricted to cloudy and temperate insular environments in the North Atlantic Ocean. Due to their reduced distribution area, these forests are particularly vulnerable to anthropogenic disturbances and changes in climatic conditions. The assessment of laurel forest trees’ response to climate variation by dendrochronological methods is limited because it was assumed that the lack of marked seasonality would prevent the formation of distinct annual tree rings. The aims of this study were to identify the presence of annual growth rings and to assess the dendrochronological potential of the most representative tree species from laurel forests in Tenerife, Canary Islands. We sampled increment cores from 498 trees of 12 species in two well-preserved forests in Tenerife Island. We evaluated tree-ring boundary distinctness, dating potential, and sensitivity of tree-ring growth to climate and, particularly, to drought occurrence. Eight species showed clear tree-ring boundaries, but synchronic annual tree rings and robust tree-ring chronologies were only obtained for Laurus novocanariensis, Ilex perado subsp. platyphylla, Persea indica and Picconia excelsa, a third of the studied species. Tree-ring width depended on water balance and drought occurrence, showing sharp reductions in growth in the face of decreased water availability, a response that was consistent among species and sites. Inter-annual tree-ring width variation was directly dependent on rainfall input in the humid period, from previous October to current April. The four negative pointer years 1995, 1999, 2008 and 2012 corresponded to severe drought events in the study area. This study gives the first assessment of dendrochronological potential and tree-ring climate sensitivity of tree species from the Tenerife laurel forest, which opens new research avenues for dendroecological studies in Macaronesian laurel forests.Ministerio de Ciencia, Innovación y Universidades (projects PID2019-109906RA-I00, PID2020-118444GA-100 and PID2019-106908RA-I00/AEI/10.13039/501100011033)Ministerio de Ciencia, Innovación y Universidades (predoctoral contract PRE2018-084106)Ministerio de Economía, Industria y Competitividad (project CGL2017-87309-P and postdoctoral grant IJC2019-040571-I)Junta de Castilla y León (projects VA113G19 and IR2020-1-UVA08)Universidad de Valladolid (predoctoral contract 113-2019PREUVA22)Comunidad de Madrid (project S2018/EMT-4338

Tree growth response to drought partially explains regional-scale growth and mortality patterns in Iberian forests

Tree-ring data has been widely used to inform about tree growth responses to drought at the individual scale, but less is known about how tree growth sensitivity to drought scales up driving changes in forest dynamics. Here, we related tree-ring growth chronologies and stand-level forest changes in basal area from two independent data sets to test if tree-ring responses to drought match stand forest dynamics (stand basal area growth, ingrowth, and mortality). We assessed if tree growth and changes in forest basal area covary as a function of spatial scale and tree taxa (gymnosperm or angiosperm). To this end, we compared a tree-ring network with stand data from the Spanish National Forest Inventory. We focused on the cumulative impact of drought on tree growth and demography in the period 1981–2005. Drought years were identified by the Standardized Precipitation Evapotranspiration Index, and their impacts on tree growth by quantifying tree-ring width reductions. We hypothesized that forests with greater drought impacts on tree growth will also show reduced stand basal area growth and ingrowth and enhanced mortality. This is expected to occur in forests dominated by gymnosperms on drought-prone regions. Cumulative growth reductions during dry years were higher in forests dominated by gymnosperms and presented a greater magnitude and spatial autocorrelation than for angiosperms. Cumulative drought-induced tree growth reductions and changes in forest basal area were related, but initial stand density and basal area were the main factors driving changes in basal area. In drought-prone gymnosperm forests, we observed that sites with greater growth reductions had lower stand basal area growth and greater mortality. Consequently, stand basal area, forest growth, and ingrowth in regions with large drought impacts was significantly lower than in regions less impacted by drought. Tree growth sensitivity to drought can be used as a predictor of gymnosperm demographic rates in terms of stand basal area growth and ingrowth at regional scales, but further studies may try to disentangle how initial stand density modulates such relationships. Drought-induced growth reductions and their cumulative impacts have strong potential to be used as early-warning indicators of regional forest vulnerability.This study was financially supported by Xunta de Galicia, Grant/Award Number PGIDIT06PXIB502262PR, GRC GI-1809; INIA, Grant/Award Number RTA2006-00117; CANOPEE, 2014-2020-FEDER funds, Spanish Science Ministry RTI2018-096884-B-C31, RTI2018-096884-B-C33, AGL2017-83828-C2-2R, RTI2018-096884-B-C3,1 and RTI2018-096884-B-C32 projects. Gabriel Sangüesa-Barreda was supported by a “Juan de la Cierva-Formación” grant from MINECO (FJCI 2016-30121). Antonio Gazol and Paloma Ruiz-Benito were supported by a project “2018 Leonardo Grant for Researchers and Cultural Creators, BBVA Foundation.” Ana-Maria Hereş was supported by the project PN-III-P1-1.1-TE-2019-1099 financed by the Romanian Ministry of Education and Research through UEFISCDI. Raúl Sánchez-Salguero was supported by VULBOS project (UPO-1263216, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020). Paloma Ruiz-Benito was supported by the Community of Madrid Region under the framework of the multi-year Agreement with the University of Alcalá (Stimulus to Excellence for Permanent University Professors, EPU-INV/2020/010) and the University of Alcalá “Ayudas para la realización de Proyectos para potenciar la Creación y Consolidación de Grupos de Investigación.” Andrea Hevia was supported by PinCaR project (UHU-1266324, FEDER Funds, Andalusia Regional Government, Consejería de Economía, Conocimiento, Empresas y Universidad 2014-2020).Peer reviewe