Suchergebnisse

The concept of spatial synchrony in ecology refers to the presence of coordinated time fluctuations in certain characteristics that can be observed in plant and animal communities inhabiting an area. It is a well-known phenomenon common to virtually every taxon, but comparatively little attention has been given to the study of the temporal coherence of forest tree performance across biogeographical gradients. In forest ecosystems, tree growth dynamics is primarily driven by climatic variability (i.e., the Moran effect). Due to rapid climate change, trees are increasingly pushed to their physiological limits up to the level that many populations are facing immediate risk of extinction. The characterization of synchrony patterns in tree growth can provide clues on the relevance of emerging climatic threats on forests, as new combinations of precipitation and temperature are entraining tree performance worldwide. In this regard, comprehensive and systematic approaches to analyse spatiotemporal dynamics of tree growth are needed. Here, we present a methodology for disentangling and interpreting how the variability and common signal strength of tree growth (or other traits) are structured in tree-ring networks. It is grounded on mixed modelling principles and broadens well-known theoretical principles in dendrosciences. Based on this approach, we describe the essential properties of spatial synchrony in tree growth at multiple geographical scales. We also discuss the potential of this methodology to discern early warning signals of climate change impacts on forest ecosystems. ; T.A.S. acknowledges support of ERANET-Mundus (European Commission). This study was supported by the project 2014 SGR1141 (Catalan Government).

Context: Pinus pinaster Ait. is found in the Iberian Peninsula under Mediterranean and Atlantic conditions. Both climates encounter each other in Galicia (NW Spain), where two bioclimatic regions can be differentiated: coastal and inland. A breeding program was launched in the coastal area, with two breeding and deployment areas delimited. Aims: We analyse plasticity patterns across regions in a coastal breeding population to assess the suitability of current breeding areas and how genetic material will likely respond to future climate. Methods: Total height at ages 3 and 8 years was assessed in 16 trials established along the coast and in inner Galicia. Clustering of environments with similar genotypic performance, family sensitivities to climatic factors and stability analyses were performed. Results: Sizeable genetic variation in plasticity was found among families, and crossover genotype-by-environment interactions were detected within and between regions. It was unfeasible to regionalize Galicia into alternative areas of stable genotypic performance. Only the cold regime was found to noticeably underlie the array of phenotypic responses to changing environmental conditions. Conclusion:s Results: suggest that previous delimitation in two breeding areas is pointless and indicate reduced effects of a changing climate towards Mediterranean conditions on decreasing population fitness. ; This study was partially supported by the research grants RTA05-173, RTA07-100 and PSE310000. Field trials were established and maintained by the Forestry Research Centre of Lourizán under the Forest Genetic Improvement Programme of Galicia, funded by the European Union and Xunta de Galicia. Raúl de la Mata enjoyed a scholarship funded by Xunta de Galicia.

High-latitude terrestrial ecosystems are crucial to the global climate system and its regulation by vegetation. Since productivity of boreal forests is much limited by low summer temperatures, it is expected that trees subjected to warming are progressively decreasing their regional growth coherence in the last decades. In this study, we used a comprehensive network of indexed ring-width records to assess 20th-century spatiotemporal patterns of climatic sensitivity of forest growth around the Urals mountain range above 60 °N (ca. 750,000 km2). This area offers an excellent opportunity to test for warming effects as most north Eurasian conifers (including Larix, Picea and Pinus species) are found along a north-to-south temperature gradient across contrasting soil hydrothermal regimes (permafrost and permafrost-free). We observed positive associations between indexed ring-width and summer temperature over the past century, decreasing southwards. However, weaker (permafrost) or non-significant (permafrost-free) relationships were consistently found at the local and regional scales after 1960. A cointegration analysis indicated that tree-growth release from cold limitation significantly reduced the degree and spatial extent of synchronous growth at short- (annual) and long-term (decadal) scales, most likely by exposing forests to endogenous (local) factors (e.g., competition, soil properties, nutrient availability) and species-specific reactions. Whereas the loss of temperature sensitivity progressively reduced non-permafrost synchrony by 50% over the whole 20th century, permafrost forests decreased their synchrony only after the 1960s, by 20%. Radial growth was enhanced in permafrost sites, as suggested by increasing basal area increment. Our results unequivocally link a substantial decrease in temporal coherence of forest productivity in boreal ecosystems to a growth release from cold limitation that is concurrent with regional warming trends. This emerging pattern points to increasing dependence on local drivers of the carbon balance and the role as carbon sinks of forests in the northern Ural region. ; This study was funded by the European Union's Seventh Framework Programme (INTERACT project), grant agreement SYNCHROTREES, the Spanish Government (grant number AGL2015-68274-C3-3-R) and the Russian Science Foundation (project number 18-14-00072).

The combined effects of local adaptation and phenotypic plasticity influencing plant performance are relevant to understand the capacity for genetic responses to climate change. Pinus halepensis is a native species of low- to mid-elevation Mediterranean forests with a high ecological value in drought-prone areas. Thus, it is of utmost importance to determine its adaptive structure for key traits such as growth or survival. Here, we analyse a highly unbalanced dataset collated from different common-garden networks that cover the distribution range of the species. A total of 82 range-wide populations were evaluated in nine Mediterranean trials located in Israel, Italy and Spain. A climate classification of populations allowed for the definition of six different groups, or ecotypes, which showed contrasting performances for tree height and survival at age 15. The effects of ecotypic differentiation and among-ecotypes genetic variation in plasticity were disentangled by fitting stability models accounting for interaction and heteroscedasticity in genotype-by-environment tables. For growth, a Finlay–Wilkinson model suggested high predictability of ecotypic plastic responses in P. halepensis, as described by different linear reaction norms. However, differences in mean height of ca. 15% among ecotypes dominated intra-specific patterns of tree growth across trials, pointing to preponderance of genotypic adaptation over differential ecotypic plasticity in this species. For survival, ecotypic differences were approximately constant across trials, suggesting lack of genotype-by-environment effects. Sub-humid cool climate populations from the eastern Mediterranean (e.g., Greek populations) showed general adaptation and high sensitivity to improved growing conditions, as opposed to populations from the driest ecological extreme of the species (e.g., south Spain and Maghreb populations), which exhibited specific adaptation to harsh environments. Altogether, our results indicate a general adaptive syndrome by which less reactive ecotypes to ameliorated conditions (e.g., non-water-limited) would be associated with high survival rates and low growth. The reported ecotypic differentiation constitutes the basis for tailoring intra-specific responses to climate and disentangling the relationship between adaptive variation and resilience towards climatic warming for this exemplary Mediterranean pine. ; This study was funded by the Spanish Government (FUTURPIN project, grant number AGL2015-68274-C3-3-R MINECO/FEDER). We acknowledge the collaboration of the Spanish network of forest genetic trials (GENFORED) and especially of Maria Regina Chambel and Eduardo Notivol for data accessing and technical cooperation. GDM wishes to thank Ernesto Fusaro and Francesco Righi (CREA-PLF) for their contribution in gathering data and for establishing the Italian trials. TK wishes to thank the Merle S. Cahn Foundation and the Monroe and Marjorie Burk Fund for Alternative Energy Studies; Mr. and Mrs. Norman Reiser, together with the Weizmann Center for New Scientists; and the Edith & Nathan Goldberg Career Development Chair.

In the Mediterranean, mixed forests of Aleppo pine and holm oak are widespread. Generally considered a transition stage in the succession towards climax oak communities, niche segregation may also contribute to the prevalence of these communities. So far, there is increasing evidence of hydrological niche segregation, with the two species showing complementary water use and seasonal growth patterns. However, it remains unknown whether interspecific interactions affect the response to climate and the mid-term (decadal) growth and water-use efficiency of pines and oaks in mixed stands. Here, we combined tree-ring chronologies, built on different competition classes within a mixed stand, with a spatially explicit assessment of individual growth and wood carbon isotope discrimination (∆13C), as a proxy of intrinsic water-use efficiency, and compared these results with previously reported water uptake patterns. We found that competition with pines modulated the climate response of oaks, whereas pine climate response was insensitive to competition. On the other hand, pine density affected only pine growth, whereas oak competition affected both species. We conclude that the presence of pines had negligible or even positive effects on the oaks, but competition with neighbor oaks limited their ability to recover after drought. Conversely, pines experienced greater drought stress under competition, with both oaks and pines ; This research was funded by the Spanish Government through Projects CGL2011-26654 and RTI2018-094691-B-C31 (MCIU/AEI/FEDER, EU). J.P.F. was supported by Reference Group H09_20R (Gobierno de Aragón, Spain).

In the Mediterranean, mixed forests of Aleppo pine and holm oak are widespread. Generally considered a transition stage in the succession towards climax oak communities, niche segregation may also contribute to the prevalence of these communities. So far, there is increasing evidence of hydrological niche segregation, with the two species showing complementary water use and seasonal growth patterns. However, it remains unknown whether interspecific interactions affect the response to climate and the mid-term (decadal) growth and water-use efficiency of pines and oaks in mixed stands. Here, we combined tree-ring chronologies, built on different competition classes within a mixed stand, with a spatially explicit assessment of individual growth and wood carbon isotope discrimination (∆13C), as a proxy of intrinsic water-use efficiency, and compared these results with previously reported water uptake patterns. We found that competition with pines modulated the climate response of oaks, whereas pine climate response was insensitive to competition. On the other hand, pine density affected only pine growth, whereas oak competition affected both species. We conclude that the presence of pines had negligible or even positive effects on the oaks, but competition with neighbor oaks limited their ability to recover after drought. Conversely, pines experienced greater drought stress under competition, with both oaks and pines. ; This research was funded by the Spanish Government through Projects CGL2011-26654 and RTI2018-094691-B-C31 (MCIU/AEI/FEDER, EU). J.P.F. was supported by Reference Group H09_20R (Gobierno de Aragon, Spain).

Stable isotopes in tree rings provide climatic information with annual resolution dating back for centuries or even millennia. However, deriving spatially explicit climate models from isotope networks remains challenging. Here we propose a methodology to model regional precipitation from carbon isotope discrimination (Δ13C) in tree rings by (1) building regional spatial models of Δ13C (isoscapes) and (2) deriving precipitation maps from Δ13C-isoscapes, taking advantage of the response of Δ13C to precipitation in seasonally dry climates. As a case study, we modeled the spatial distribution of mean annual precipitation (MAP) in the northeastern Iberian Peninsula, a region with complex topography and climate (MAP = 303–1086 mm). We compiled wood Δ13C data for two Mediterranean species that exhibit complementary responses to seasonal precipitation (Pinus halepensis Mill., N = 38; Quercus ilex L.; N= 44; pooling period: 1975–2008). By combining multiple regression and geostatistical interpolation, we generated one Δ13 C-isoscape for each species. A spatial model of MAP was then built as the sum of two complementary maps of seasonal precipitation, each one derived from the corresponding Δ13C-isoscape (September–November from Q. ilex; December–August from P. halepensis). Our approach showed a predictive power for MAP (RMSE = 84 mm) nearly identical to that obtained by interpolating data directly from a similarly dense network of meteorological stations (RMSE = 80–83 mm, N= 65), being only outperformed when using a much denser meteorological network (RMSE=56–57 mm, N=340). This method offers new avenues for modeling spatial variability of past precipitation, exploiting the large amount of information currently available from tree-ring networks. ; This work was funded by the Marie Curie project SMARTREES (MC-ERG-246725, European Union, FP7), and Spanish project PALEOISOTREE (CGL2009-13079-C02-01). J.d.C. is supported by a FPI fellowship (MCINN, Spain). JPF is supported by the Ramón y Cajal programme (RYC-2008-02050, MCINN, Spain).

Understanding climate change impacts on drought-prone forests is a critical issue. We investigated ring-width and stable isotopes (Δ13C and δ18O) in two Pinus sylvestris stands of the cold-dry Siberian forest-steppe growing under contrasting climatic trends over the last 75 years. Despite regional warming, there was increasing precipitation during the growing period at the southern site (MIN) but increasing water deficit (WD) at the northern site (BER). Intrinsic water use efficiency (WUEi) increased similarly (ca. 22%) in response to warming and rising atmospheric CO2. However, the steady increase in WUEi was accompanied by divergent growth patterns since 1980: increasing basal area increment (BAI) in MIN (slope = 0.102 cm2 year−2) and decreasing BAI in BER (slope = −0.129 cm2 year−2). This suggests that increased precipitation, mediated by CO2 effects, promoted growth in MIN, whereas intensified drought stress led to decreased carbon gain and productivity in BER. When compared to warm-dry stands of eastern Spain, the WUEi dependence on WD was three-fold greater in Siberia. Conversely, BAI was more affected by the relative impact of water stress within each region. These results indicate contrasting future trajectories of P. sylvestris forests, which challenge forecasting growth and carbon sequestration in cold-dry areas. ; This study was funded by the Spanish Government (grant number AGL2015-68274-C3-3-R) and the Russian Science Foundation (project numbers 14-14-00295, sampling and tree-ring data obtainment and 14-14-00219-P, mathematical approach). We acknowledge P. Sopeña and M.J. Pau for technical assistance.

Drought is the main abiotic stress affecting Mediterranean forests. Root systems are responsible for water uptake, but intraspecific variability in tree root morphology is poorly understood mainly owing to sampling difficulties. The aim of this study was to gain knowledge on the adaptive relevance of rooting traits for a widespread pine using a non-invasive, high-throughput phenotyping technique. ; This work was partly funded by the Spanish Government, grant numbers AGL2015-68274-C3-3-R (MINECO/FEDER) and RTI2018-094691-B-C31 (MCIU/AEI/FEDER, EU). E. Lombardi was supported by a AGAUR FI-2020 pre-doctoral fellowship (with the support from the Secretariat for Universities and Research of the Ministry of Business and Knowledge of the Government of Catalonia and the European Social Fund). J. P. Ferrio was supported by Reference Group H09_20R (Gobierno de Aragón). U. Rodríguez-Robles acknowledges the National Council for Science and Technology of Mexico (CONACyT), grant number 332356

The assessment of genetic differentiation in functional traits is fundamental towards understanding the adaptive characteristics of forest species. While traditional phenotyping techniques are costly and time‐consuming, remote sensing data derived from cameras mounted on unmanned aerial vehicles (UAVs) provide potentially valid high‐throughput information for assessing morphophysiological differences among tree populations. In this work, we test for genetic variation in vegetation indices (VIs) and canopy temperature among populations of Pinus halepensis as proxies for canopy architecture, leaf area, photosynthetic pigments, photosynthetic efficiency and water use. The interpopulation associations between vegetation properties and above‐ground growth (stem volume) were also assessed. Three flights (July 2016, November 2016 and May 2017) were performed in a genetic trial consisting of 56 populations covering a large part of the species range. Multispectral (visible and near infrared wavelengths), RGB (red, green, blue) and thermal images were used to estimate canopy temperature and vegetation cover (VC) and derive several VIs. Differences among populations emerged consistently across flights for VC and VIs related to leaf area, indicating genetic divergence in crown architecture. Population differences in indices related to photosynthetic pigments emerged only in May 2017 and were probably related to a contrasting phenology of needle development. Conversely, the low population differentiation for the same indices in July 2016 and November 2016 suggested weak interpopulation variation in the photosynthetic machinery of mature needles of P. halepensis. Population differences in canopy temperature found in July 2016 were indicative of variation in stomatal regulation under drought stress. Stem volume correlated with indices related to leaf area (positively) and with canopy temperature (negatively), indicating a strong influence of canopy properties and stomatal conductance on above‐ground growth at the population level. Specifically, a combination of VIs and canopy temperature accounted for about 60% of population variability in stem volume of adult trees. This is the first study to propose UAV remote sensing as an effective tool for screening genetic variation in morphophysiological traits of adult forest trees. ; This work was supported by the Spanish Government (MINECO/FEDER grant number AGL2015‐68274‐C3‐3‐R).

Vegetation in water-limited ecosystems relies strongly on access to deep water reserves to withstand dry periods. Most of these ecosystems have shallow soils over deep groundwater reserves. Understanding the functioning and functional plasticity of species-specific root systems and the patterns of or differences in the use of water sources under more frequent or intense droughts is therefore necessary to properly predict the responses of seasonally dry ecosystems to future climate. We used stable isotopes to investigate the seasonal patterns of water uptake by a sclerophyll forest on sloped terrain with shallow soils. We assessed the effect of a long-term experimental drought (12 years) and the added impact of an extreme natural drought that produced widespread tree mortality and crown defoliation. The dominant species, Quercus ilex, Arbutus unedo and Phillyrea latifolia, all have dimorphic root systems enabling them to access different water sources in space and time. The plants extracted water mainly from the soil in the cold and wet seasons but increased their use of groundwater during the summer drought. Interestingly, the plants subjected to the long-term experimental drought shifted water uptake toward deeper (10-35 cm) soil layers during the wet season and reduced groundwater uptake in summer, indicating plasticity in the functional distribution of fine roots that dampened the effect of our experimental drought over the long term. An extreme drought in 2011, however, further reduced the contribution of deep soil layers and groundwater to transpiration, which resulted in greater crown defoliation in the drought-affected plants. The present study suggests that extreme droughts aggravate moderate but persistent drier conditions (simulated by our manipulation) and may lead to the depletion of water from groundwater reservoirs and weathered bedrock, threatening the preservation of these Mediterranean ecosystems in their current structures and compositions. ; This research was supported by the Spanish Government projects CGL2010-17172 and 609 Consolider Ingenio Montes (CSD2008-00040), by the Catalan Government project SGR 610 2009-458 and the European Research Council Synergy grant ERC-2013-SyG-610028 611 IMBALANCE-P. A.B. acknowledges an FPI predoctoral fellowship from the Spanish 612 Ministry of Economy and Competitiveness that supported his visit to UC Berkeley.

1. Climate warming increases vulnerability to drought in Mediterranean water-limited forests. However, we still lack knowledge of the long-term physiological responses of coexisting pine species in these forests regarding their ability to cope with warming-induced drought stress. 2. We investigated spatiotemporal patterns of tree performance for five isohydric pines with partially overlapping ecological niches in the eastern Iberian Peninsula along an altitudinal gradient: Pinus halepensis = Pinus pinaster ≤ Pinus nigra ≤ Pinus sylvestris ≤ Pinus uncinata. 3. Using indexed tree-ring widths (TRWi), we assessed the changes in the temporal coherence of radial growth (growth synchrony, âC) over the period 1902-2011 across three elevation belts: low ≈1100 m; mid = 1615 m; high = 2020 m. We also examined by mixed modelling whether TRWi showed an increased coupling with leaf-level gas exchange (inferred from indexed carbon isotope discrimination, Δ13Ci) by enhanced stomatal regulation in response to an amplified regional drought stress. 4. Increasingly negative annual water balances (decrease in annual precipitation minus evapotranspiration = −4·8 mm year−1; 1970-2011) prompted more synchronous growth of coexisting pines between low- and mid-elevation belts, with âC rising from 0·25 ± 0·04 (1902-1951) to 0·62 ± 0·05 (1962-2011). This effect was coupled with tighter stomatal regulation at mid-elevation as indicated by high correlations between TRWi and Δ13Ci (>0·60 from the mid-1970s onwards) which resembled those found at low elevation. Simultaneously, TRWi vs. Δ13Ci uncoupling occurred at the high-elevation belt across species. 5.Weaker growth-climate relationships as elevation increased highlighted the major role of the altitude-dependent thermal gradient in growth responsiveness to drought; however, an intensified Δ13Ci response to spring water availability across elevation belts observed from mid-1970s onwards suggested regional shifts in tree physiological activity linked to earlier seasonal drought impacts. Warming-induced drought stress is spreading to higher altitudes in Iberian pinewoods as multispecies growth is linked to progressively tighter stomatal control of water losses reflected in wood Δ13C. ; T.A.S. and J.P.F acknowledge ERANET-Mundus (European Commission, Grant agreement 20112573) and the Ramón y Cajal program (RYC-2008-02050) respectively. A.A.K. benefitted from a visiting grant (University of Lleida). This study was supported by projects AGL2015-68274-C3-3-R (MINECO/FEDER) and 2014 SGR1141 (Catalan Government). We acknowledge P. Sopeña and M.J. Pau for technical assistance and G. Sangüesa-Barreda for field sampling.

Summary: Many ecologically important forest trees from dry areas have been insufficiently investigated for their ability to adapt to the challenges posed by climate change, which hampers the implementation of mitigation policies. We analyzed 14 common‐garden experiments across the Mediterranean which studied the widespread thermophilic conifer Pinus halepensis and involved 157 populations categorized into five ecotypes. Ecotype‐specific tree height responses to climate were applied to projected climate change (2071-2100 ad), to project potential growth patterns both locally and across the species' range. We found contrasting ecotypic sensitivities to annual precipitation but comparatively uniform responses to mean temperature, while evidence of local adaptation for tree height was limited to mesic ecotypes. We projected intriguing patterns of response range‐wide, implying either height inhibition or stimulation of up to 75%, and deduced that the ecotype currently experiencing more favorable (wetter) conditions will show the largest inhibition. Extensive height reductions can be expected for coastal areas of France, Greece, Spain and northern Africa. Our findings underline the fact that intraspecific variations in sensitivity to precipitation must be considered when projecting tree height responses of dry forests to future climate. The ecotype‐specific projected performances call for management activities to ensure forest resilience in the Mediterranean through, for example, tailored deployment strategies. ; This study was funded by the Spanish Government (MCIU/AEI/ coordinated grants AGL2015‐68274‐C3‐3‐R and RTI2018‐094691‐B).

Aims Harsh edaphic environments harbor species with different soil affinities. Plant's responses to specific edaphic constraints may be compromised against re- sponses to prevalent stresses shared with other semi- arid environments. We expect that species with high edaphic affinity may show traits to overcome harsh soil properties, while species with low affinity may respond to environmental constraints shared with arid environments. Methods We quantified the edaphic affinity of 12 plant species co-occurring in gypsum outcrops and measured traits related to plant responses to specific gypsum con- straints (rooting and water uptake depth, foliar accumu- lation of Ca, S and Mg), and traits related to common constraints of arid environments (water use efficiency, macronutrients foliar content). Results Plants in gypsum outcrops differed in their strategies to face edaphic limitations. A phylogenetic informed PCA segregated species based on their foliar Ca and S accumulation and greater water uptake depths, associated with plant responses to specific gypsum lim- itations. Species' gypsum affinity explained this segre- gation, but traits related to water or nutrient use efficien- cy did not contribute substantially to this axis. Conclusions Plant's specializations to respond to spe- cific edaphic constraints of gypsum soils do not limit their ability to deal with other non-specific environmen- tal constraints ; The author thanks the Yesaires team, es- pecially to Daniel A. Rodríguez Ginart, for making the fieldwork of quantification of species gypsum affinity possible. We thank Dr. Sara Palacio (IPE) and two anonymous reviewers for their helpful revisions and comments on the manuscript. RSM was supported by the Ministry of Science and Innovations (FPU grant FPU17/00629). JPF was supported by Grupo de Referencia H09_20R (Aragón regional government, Spain). Financial support was provided by the Valencian Regional Government (GV/2016/ 187) and the Spanish Ministry of Science, Innovation and Univer- sities ...

Summary: Progress in high‐throughput phenotyping and genomics provides the potential to understand the genetic basis of plant functional differentiation. We developed a semi‐automatic methodology based on unmanned aerial vehicle (UAV) imagery for deriving tree‐level phenotypes followed by genome‐wide association study (GWAS). An RGB‐based point cloud was used for tree crown identification in a common garden of Pinus halepensis in Spain. Crowns were combined with multispectral and thermal orthomosaics to retrieve growth traits, vegetation indices and canopy temperature. Thereafter, GWAS was performed to analyse the association between phenotypes and genomic variation at 235 single nucleotide polymorphisms (SNPs). Growth traits were associated with 12 SNPs involved in cellulose and carbohydrate metabolism. Indices related to transpiration and leaf water content were associated with six SNPs involved in stomata dynamics. Indices related to leaf pigments and leaf area were associated with 11 SNPs involved in signalling and peroxisome metabolism. About 16-20% of trait variance was explained by combinations of several SNPs, indicating polygenic control of morpho‐physiological traits. Despite a limited availability of markers and individuals, this study is provides a successful proof‐of‐concept for the combination of high‐throughput UAV‐based phenotyping with cost‐effective genotyping to disentangle the genetic architecture of phenotypic variation in a widespread conifer. ; This work was supported by the Spanish Government, grant number RTI2018‐094691‐B‐C31 (MCIU/AEI/FEDER, EU).