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Grain was the most important food source in early modern Europe (c. 1500–1800), and its price influenced the entire economy. The extent to which climate variability determined grain price variations remains contested, and claims of solar cycle influences on prices are disputed. We thoroughly reassess these questions, within a framework of comprehensive statistical analysis, by employing an unprecedentedly large grain price data set together with state-of-the-art palaeoclimate reconstructions and long meteorological series. A highly significant negative grain price–temperature relationship (i.e. colder = high prices and vice versa) is found across Europe. This association increases at larger spatial and temporal scales and reaches a correlation of $$-\,0.41$$ - 0.41 considering the European grain price average and previous year June–August temperatures at annual resolution, and of $$-\,0.63$$ - 0.63 at decadal timescales. This strong relationship is of episodic rather than periodic (cyclic) nature. Only weak and spatially inconsistent signals of hydroclimate (precipitation and drought), and no meaningful association with solar variations, are detected in the grain prices. The significant and persistent temperature effects on grain prices imply that this now rapidly changing climate element has been a more important factor in European economic history, even in southern Europe, than commonly acknowledged.

Millennial-length tree-ring width chronologies are used to reconstruct temperature and place recent warming into historical context. The Simplon valley in the Western Central Alps is an ideal region for such a study as it provides historical timber back to medieval times which can be combined with temperature sensitive living larch trees. However, the exact provenance of the historical timber is unknown, but might origin from different elevations which potentially biases derived temperature reconstructions. To study the effect of elevation on tree growth and climate sensitivity, approximately 250 trees at three elevational levels (1500, 1700, and 2000 m a.s.l.) were sampled. Results indicate that the overall growth rate decreases with increasing elevation. Significant correlations between tree-ring width and summer temperature are recorded at tree sites ≥ 1700 m a.s.l. The comparison of the growth patterns between living trees and historical timber from Simplon Village (1476 m a.s.l.) reveals a most likely origin of the historical samples between 1700 and 2000 m a.s.l. When combining the data from the living trees at the different elevational levels with the historical timber, to produce three separate chronologies spanning the past 1200 years, substantial low frequency differences are recorded after RCS detrending the data. This finding demonstrates that the origin of samples in combined (living + historical) chronologies has a strong influence on long-term summer temperature reconstructions. It is thus important to analyse the growth characteristics of historical timber, and estimate their provenance in comparison to living trees, when producing millennial length chronologies.

Key message Whereas cold temperatures and artificial smoke pollution (during World War II) cause negative pointer years in northern Fennoscandian downy birches, mass outbreaks of Epirrita autumnata L. and Operophtera brumata Bkh. are the strongest growth-influencing and -synchronizing factor. Abstract Variations in radial tree growth of downy birch can be affected by short-term environmental changes. Here we examine the tree-ring width of downy birch trees for signals caused by three different disturbance factors: climatic extremes, insect outbreaks, and artificial smoke employed to hide the German battleship Tirpitz during World War II at the Kåfjord in northern Norway. Besides growth/climate response analysis using gridded climate data and a tree ring width-chronology of the studied birch trees, we analyze missing rings, pointer years, and the ability of recovery after severe disturbances on an individual tree basis using the percent change of the trees’ basal area increment with respect to a reference period. The downy birches reveal (1) a significant positive correlation with May and June temperatures, (2) a high growth sensitivity to moth epidemics (Epirrita autumnata L. and Operophtera brumata Bkh.), and (3) a distinct growth deviation in the year of intense but short-term artificial smoke pollution. We conclude that downy birches are not exclusively sensitive to unusual cold temperatures, but short-term artificial pollution and insect outbreaks cause similar growth declines in the year of occurrence. Whereas for temperature and pollution, the growth response is less coherent among trees, and fades within 2 years, the insect outbreaks synchronize growth among all downy birches. Growth declines during years of mass insect outbreaks can further be amplified by cold May and June temperatures. Our findings thereby improve the understanding of competing disturbance factors on single birch trees but also on the growth of a whole site in Fennoscandia and facilitates the detection of disturbances in birch chronologies.

We analyze annually resolved tree-ring stable carbon (I´13C) and oxygen (I´18O) isotopic chronologies from Swiss stone pine (Pinus cembra L.) in Romania. The chronologies cover the period between 1876 and 2012 and integrate data from four individual trees from the Calimani Mts in the eastern Carpathians where climatic records are scarce and starts only from 1961. Calibration trials show that the I´13C values correlate with local April-May relative humidity and with regional to larger scale (European) summer precipitation. I´18O correlates significantly with local relative humidity, cloud cover, maximum temperature, as well as European scale drought conditions. In all cases, the climate effects on I´13C values are weaker than those recorded in the I´18O data, with the latter revealing a tendency towards higher (lower) values of I´18O during extremely dry (wet) years. The most striking signal, however, is the strong link between the interannual I´18O variability recorded in the Calimani Mts and large-scale circulation patterns associated with North Atlantic and Mediteraneean Sea sea surface temperatures. High (low) values of I´18O occur in association with a high (low) pressure system over the central and eastern part of Europe and with a significantly warmer (colder) Mediterranean Sea surface temperature. These results demonstrate the possibility of using tree ring oxygen isotopes from the eastern Carpathians to reconstruct regional drought conditions in eastern Europe on long-term time scales and larger scale circulation dynamics over the pre-instrumental periods.

X-ray microdensitometry on annually resolved tree-ring samples has gained an exceptional position in last-millennium paleoclimatology through the maximum latewood density (MXD) parameter, but also increasingly through other density parameters. For 50 years, X-ray based measurement techniques have been the de facto standard. However, studies report offsets in the mean levels for MXD measurements derived from different laboratories, indicating challenges of accuracy and precision. Moreover, reflected visible light-based techniques are becoming increasingly popular, and wood anatomical techniques are emerging as a potentially powerful pathway to extract density information at the highest resolution. Here we review the current understanding and merits of wood density for tree-ring research, associated microdensitometric techniques, and analytical measurement challenges. The review is further complemented with a careful comparison of new measurements derived at 17 laboratories, using several different techniques. The new experiment allowed us to corroborate and refresh "long-standing wisdom" but also provide new insights. Key outcomes include (i) a demonstration of the need for mass/volume-based recalibration to accurately estimate average ring density; (ii) a substantiation of systematic differences in MXD measurements that cautions for great care when combining density data sets for climate reconstructions; and (iii) insights into the relevance of analytical measurement resolution in signals derived from tree-ring density data. Finally, we provide recommendations expected to facilitate futureinter-comparability and interpretations for global change research.

Grain was the most important food source for a majority of the population in early modern Europe (c. 1500–1800). The price level and volatility had huge societal effects: high prices tended to increase mortality, decrease fertility as well as affect overall consumption patterns. To what extent climate variability influenced the long-term grain price evolution in early modern Europe has for a long time been a matter of debate. Recent advances in high-resolution palaeoclimatology and historical climatology have made it possible to reassess the grain price–climate relationship in time and space with unprecedented detail (Esper et al. 2017). We analyse the climate signal in 56 multi-centennial long series of annual prices of barley, oat, rye, and wheat across Europe. The grain price–climate relationship in regional clusters of grain price data is analysed using both tree-ring based temperature reconstructions, documentary-based temperature reconstructions, tree-ring based drought reconstructions, and early temperature and precipitation instrumental data, considering possible different climate responses in each grain type and different seasonal targets. In addition, we systematically investigate whether, and to what extent, the imprints of variations in solar forcing, including possible lag effects, can be detected in the grain prices.We find a highly significant and persistent negative temperature–price relationship (i.e., cold = high prices and vice versa) across all of Europe and for all four grain types using both temperature reconstructions and instrumental temperature data. Excluding the Thirty Years’ War (1618–1648) and the period following the French Revolution (1789), this relationship is as strong as r = –0.41 between the annual average of all the 56 included European grain price series and the reconstructed June–August temperature for the previous year. The correlations to drought and precipitation are, on the other hand, mainly insignificant and inconsistent in time and space. The evidence for the existence of the effect of solar forcing variations on early modern European grain prices is not strong, although we can detect statistically significant grain price–solar forcing relationships for certain regions. In conclusion, we find much stronger evidence than hitherto reported for long-term temperature imprints on historical grain prices in Europe, implying that temperature variability and change have been a more important factor in European economic history, even in southern Europe, than commonly acknowledged. Reference:Esper J., et al., 2017. Environmental drivers of historical grain price variations in Europe. Clim. Res. 72: 39–52.

The long tradition in dendroclimatological studies across Fennoscandia is mainly due to the exceptional strong temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world’s advanced multi-millennial-long ring width and density based climate reconstructions have been developed in northern Fennoscandia, it is still unclear if differences in micro-site ecology have been considered sufficiently in previous studies. In order to assess the effects of moist lakeshores versus drier inlands on forest productivity, we present a Fennoscandia-wide network of 44 Scots pine ring width chronologies from 22 locations between 59°-70°N and 16°-31°E. Clustering into coastal settings in northern Norway, continental sites in the lee of the Scands north of the polar circle, and locations south of the polar circle, our network reveals a general dependency of pine growth rates on latitude and July temperature. Differences between moist and dry sites are likely caused by associated effects on soil temperature. While trees at moist micro-sites at western locations exhibit higher growth rates, this pattern inverses under the more continental conditions of the east, where increased ring widths are found at drier sites. In addition to the latitudinal increase in growth sensitivity to July temperature, pines at moist sites tend to show a higher dependency to summer warmth. The highest temperature sensitivity and growth coherency is found in those regions where July temperatures range between 11.5 and 13.5°C and May precipitation totals fall below 100mm. This study not only emphasizes the effects of micro-site ecology on Fennoscandian tree growth, but also provides guidance for the selection of sampling sites for climate reconstructions.

Pinus sylvestris tree-ring delta C-13 and delta O-18 records from locally moist sites in central and northern Sweden contain consistently stronger climate signals than their dry site counterparts. ...

Spatial covariance in the simulated temperature evolution over the past millennium has been reported to exceed that of multiproxy-based reconstructions. Here we use tree ring-based temperature reco ...

We present the longest high-elevation tree-ring width dataset in the Mediterranean reaching back to the 6th century CE. The network includes 101 living and 92 relict Pinus heldreichii Christ trees from four differently exposed sites in the 2100–2200 m a.s.l. elevation range of Mt. Smolikas in the Pindus Mountains in Greece. Though the sites were all sampled within a distance of 1550–2014 = 0.65–0.87), indicating site exposure might affect tree-ring formation. We here explore the consequence of exposure differences on the climate signals in an eastern Mediterranean treeline ecotone. Temporally stable growth/climate relationships reveal similar seasonal patterns among the four sites, but differences in signal strength. P. heldreichii growth at Mt. Smolikas is significantly controlled by temperature in April (r 1951–2014 = 0.33–0.50) and precipitation in June-July (r 1951–2014 = 0.23–0.42), which emphasizes the overall importance of an early growth onset and subsequent moisture conditions. The association between stem growth and April climate is strongest in the South-facing stand, supporting the significance of higher insolation rates at this thermally privileged site. Strongest summer precipitation signals are found in the NE-facing stand, where trees seem to benefit least from an early growth onset and where reduced meltwater supply may enhance the dependency on early summer precipitation. The significance of spring temperature on tree growth in all four sites constrains the emergence of a distinct summer precipitation signal in the Mt. Smolikas high elevation ecotone. Exploration of the site-specific influences on a new millennium-long tree-ring width dataset is an important step towards an improved understanding of long-term climate variability in the Eastern Mediterranean. Site-related differences in climate sensitivity in the high-elevation tree-ring network at Mt. Smolikas indicate that both temperature and precipitation during different seasons could potentially be reconstructed if distinct site exposures (S versus NE) are considered.

2 .pdf files: File 1. Author's article final version, Post-Print (19 Pags.- 4 Figs.- 2 Tabls.). File 2. Supplementary Materials (3 Figs.- 2 Tabls.- 1 Model Equation)., Aim Previous work demonstrated the global variability of synchrony in tree growth within populations, that is, the covariance of the year‐to‐year variability in growth of individual neighbouring trees. However, there is a lack of knowledge about the causes of this variability and its trajectories through time. Here, we examine whether climate can explain variation in within‐population synchrony (WPS) across space but also through time and we develop models capable of explaining this variation. These models can be applied to the global tree cover under current and future climate change scenarios. Location Global. Time period 1901–2012. Major taxa studied Trees. Methods We estimated WPS values from a global tree‐ring width database consisting of annual growth increment measurements from multiple trees at 3,579 sites. We used generalized linear mixed effects models to infer the drivers of WPS variability and temporal trends of global WPS. We then predicted WPS values across the global extent of tree cover. Finally, we applied our model to predict future WPS based on the RCP 8.5 (2045–2065 period) emission scenario. Results Areas with the highest WPS are characterized by a combination of environments with both high mean annual temperature (>10°C) and low precipitation (, E.T. and M.V. were partially supported by National Science Foundation ‐ Partnership in International Research and Education (OISE‐1743738) and National Science Foundation ‐ Paleo Perspectives on Climate Change (AGS‐1702439). R.S.‐N. is funded by a “Juan de la Cierva” postdoctoral grant FJCI‐2017‐31595. E.T., M.S., R.S.‐N. and M.D.L. are supported by the Government of Aragón through the “Program of research groups” (group H38, “Clima, Agua, Cambio Global y Sistemas Naturales”). A.L. was supported by grant EVA4.0, No. CZ.02.1.01/0.0/0.0/16_019/0000803, financed by OP RDE and by the U.S. Department of Agriculture Forest Service.

Outbreaks of the larch budmoth (LBM) in the European Alps are among the most documented population cycles and their historical occurrence has been reconstructed over 1200 years. Causes and consequences of cyclic LBM outbreaks are poorly understood and little is known about populations near the margin of the host's distribution range. In the present study, we quantify historical LBM outbreaks and associated growth reductions in host trees (European larch). Tree-ring data collected from 18 sites between approximately 500 and 1700 m a.s.l. in the Northern pre-Alps are compared with data from the Western Alps and Tatra Mountains, as well as with nonhost Norway spruce. Highly synchronized host and nonhost growth in the Northern pre-Alps shows that periodic LBM outbreaks are largely absent near the distributional limit of larch. By contrast, growth patterns in the Western Alps LBM core region are indicative of LBM events. Although climatic conditions in the Northern pre-Alps and Tatra Mountains would allow LBM outbreaks, low host plant abundance is likely the key driver for the absence of cyclic outbreaks in these regions. The results obtained in the present study suggest that, in addition to the climatic conditions, host-species abundance is critically important for the occurrence of periodic LBM outbreaks and the determination of the respective outbreak range.

German Science Foundation [161/9-1]; National Natural Science Foundation of China [41325008]; [RNF 15-14-30011]

The long tradition of dendroclimatological studies in Fennoscandia is fostered by the exceptional longevity and temperature sensitivity of tree growth, as well as the existence of well-preserved subfossil wood in shallow lakes and extent peat bogs. Although some of the world’s longest ring width and density-based climate reconstructions have been developed in northern Fennoscandia, it is still unclear if differences in micro-site ecology matter, and if so, whether they have been considered sufficiently in previous studies. We developed a Fennoscandia-wide network of 44 Scots pine ring width chronologies from 22 locations between 59°–70 °N and 16°–31 °E, to assess the effects of moist lakeshores and dry inland micro-sites on tree growth. Our network reveals a strong dependency of pine growth on July temperature, which is also reflected in latitude. Differences in forest productivity between moist and dry micro-sites are likely caused by associated effects on soil temperature. While trees at moist micro-sites at western locations exhibit higher growth rates, this pattern is reversed in the continental eastern part of the network, where increased ring widths are found at drier sites. In addition to the latitudinal increase in growth sensitivity to July temperature, pines at moist sites exhibit an increased dependency of summer warmth. The highest temperature sensitivity and growth coherency, and thus greatest suitability for summer temperature reconstructions, is found in those regions where July mean temperatures range between 11.5 and 13.5 °C, and May precipitation totals do not exceed 100 mm. Our study not only provides guidance for the selection of sampling sites for tree ring-based climate reconstructions, but also reveals the effect of micro-site ecology on Fennoscandian forest growth. The manifestation of micro-site effects varies substantially over the Fennoscandian boreal forest and is predominately triggered by the geographical setting of the stand as expressed by differing abiotic site factors.

Stable hydrogen isotopes ratios of lignin methoxyl groups (expressed as δ2HLM) of wood have been shown to reflect the climate-sensitive δ2H values of precipitation (expressed as δ2Hprecip) modulated by a large uniform negative isotope fractionation. However, a detailed calibration study among temporal variabilities of δ2HLM in tree-ring series, site-specific δ2Hprecip and climate parameters has not been performed yet. Here, we present annually resolved δ2HLM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near stations of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the Deutsche Wetterdienst (DWD) meteorological observatory at Hohenpeißenberg (southern Germany; ~ 48° N, 11° E). The measured nine δ2HLM tree-ring series (common period of overlap 1916-2015) show a strong coherency as indicated by highly significant (p

Stable hydrogen isotope ratios of lignin methoxyl groups (δ2HLM) of wood have been shown to reflect climate-sensitive δ2H values of precipitation (δ2Hprecip). However, a detailed calibration study between high-resolution δ2HLM and δ2Hprecip data has not been performed yet. Here, we present annually resolved δ2HLM values from nine tree-ring series (derived from four Fagus sylvatica L. trees) collected near a station of the Global Isotope Network of Isotopes in Precipitation (GNIP) and the meteorological observatory at Hohenpeisenberg (Germany; ~48°N, 11°E). The nine δ2HLM tree-ring series show highly significant inter-series correlations (Rbar = 0.52) over the common period of overlap 1916–2015 and no sign of a major juvenile trend affecting the first decades of growth. When compared with local instrumental data, the combined δ2HLM chronology is most indicative for annually averaged δ2Hprecip values. In line with this finding, the δ2HLM chronology shows similar climatic imprints as commonly observed for European stable water isotopes. We find the highest correlation (r = 0.72, p

Addressing timely and relevant questions across a multitude of spatiotemporal scales, state-of-the-art interdisciplinary drought research will likely increase in importance under projected climate change. Given the complexity of the various direct and indirect causes and consequences of a drier world, scientific tasks need to be coordinated efficiently. Drought-related research endeavors ranging from individual projects to global initiatives therefore require prioritization. Here, we present 60 priority questions for optimizing future drought research. This topical catalogue reflects the experience of 65 scholars from 21 countries and almost 20 fields of research in both natural sciences and the humanities. The set of drought-related questions primarily covers the drought monitoring, impacts, forecasting, climatology, adaptation, as well as planning and policy. The questions highlight the increasingly important role of remote sensing techniques in drought monitoring, importance of drought forecasting and understanding the relationships between drought parameters and drought impacts but also challenges of drought adaptation and preparedness policies.

Ice core-based estimates of past volcanic eruptions are the main forcing of the last millennium climate model simulations. Understanding the timing and magnitude of eruptions is thus critical for assessing the dynamics of the Earth’s climate system. Uncertainty associated with a major event in the 1450s, originally attributed to the South Pacific Kuwae eruption in 1452 and recently shifted to 1458, fundamentally alters model simulations, their comparison with proxy-based climate reconstructions, and any subsequent historical interpretation. Here, we compile a Northern Hemisphere tree-ring network of 25 maximum latewood density chronologies extending back over the past 650+ years to analyze the 1450s temperature deviations. Statistically robust warm season temperature reconstructions from 20 of these records reveal a spatially coherent and exceptional cooling in 1453. Summer cooling ranged from −0.4 °C in the Swiss Alps to −6.9 °C in the Polar Urals (Russia) and was generally stronger across the Eurasian high latitudes and northwestern North America. Year 1453 also marks the onset of a 15-year cold period during which network mean temperatures ranged from −2.5 °C in 1453 to −0.5 °C in 1468. In contrast, the years 1459 (−1.0 °C) and 1460 (−0.4 °C) were not exceptionally cold in the contemporary context. These findings suggest either that the original dating pointing to a major eruption in 1452 (and large-scale cooling in 1453) was correct or that the eruption left no substantial climatic fingerprint in Northern Hemisphere temperature proxies. The latter appears less likely as sulfate aerosol deposits associated with the 1450s event are found in ice cores of both hemispheres.

Mountain forests offer a range of socio-economic and ecological services, e.g. provid- ing wood harvest products, serving as hotspots of biodiversity and fulfilling protective functions. In the European Alps, where these environments are dominated by drought-sensitive Norway spruce, it has been questioned whether these services can be secured in the substantially warmer and drier climates predicted for the mid-to-late 21st century. Here, we compile a tree-ring width network of 500 spruce trees from the Northern Limestone Alps to assess growth reactions to drought events and evaluate the long-term impact of the recent temperature shift through ana - lyses along elevational transects. Our dataset covers a larger region in the Northern European Alps extending 250 km from west to east and encompassing an altitudinal range of 1200 m (from 500 to 1700 m a.s.l.). Climate-growth analyses reveal spatially varying drought sensitivities within this spruce network, with elevation (along with associated hydrothermal changes) being the key drivers behind the varying responses. Trees at lower elevations are affected negatively by drought and high temperatures, but at higher altitudes, spruce benefits from warmer climatic con- ditions. However, despite a sharp temperature increase of ~1°C since the 1990s, we observed nei- ther growth suppression at the lower elevation sites nor growth increase at higher elevation sites. These findings reveal the ability of mountain forests to adapt to an unprecedented temperature shift, suggesting that adaptation to forthcoming climate changes might not require a shift in tree species composition in the Northern Limestone Alps.

To study the decay of coarse woody debris (CWD) in forest ecosystems, it is necessary to determine the time elapsed since tree death, which is difficult at advanced decay stages. Here, we compare two methods for age determination of CWD logs, dendrochronological cross-dating and radiocarbon analysis of the outermost tree ring. The methods were compared using samples from logs of European beech, Norway spruce and Sessile oak decomposing in situ at three different forest sites. For dendrochronological cross-dating, we prepared wood discs with diameters of 10–80 cm. For radiocarbon analysis, cellulose was isolated from shavings of the outermost tree rings. There was an overall good agreement between time of death determined by the two methods with median difference of 1 year. The uncertainty of age determination by the radiocarbon approach did not increase with decreasing carbon density, despite incomplete separation of chitin from the extracted cellulose. Fungal chitin has the potential to alter the radiocarbon signature of tree rings as the carbon for chitin synthesis originates from different sources. Significant correlations between year of tree death and carbon density of wood were found for beech and spruce, but not for oak due to relatively small decreases in carbon density within 50–60 years. Total residence times of CWD were calculated from these correlations and revealed 24 years for beech and 62 years for spruce. The uncertainty of total residence times results mainly from huge natural variability in carbon density of CWD rather than uncertainty in the age determination. The results suggest that both methods are suitable for age determination of CWD.

War has an immediate and obvious effect on people and communities, but its impacts on local ecology can be more subtle. This paper shows how one military encounter in the Second World War has left a clear legacy in the northern forests of Norway, trackable more than seventy years later. We used annual growth rings of ∼180 pine and ∼30 birch trees as witnesses of the deployment of the German battleship Tirpitz at the Kafjord. The Tirpitz was the target of several Allied air attacks, but the Kriegsmarine (German navy from 1935 to 1945) used artificial smoke, consisting of chlorosulfonic acid and zinc/hexachloroethane, to hide the ship. These smoke-screen actions throughout 1944 caused pine forests surrounding the Kafjord to exhibit a strong and unusual growth decline during the following year. Severe defoliation and limited photosynthetic activity likely triggered this decline. The tree damage extended up to 4 km away from the Tirpitz. In the most extreme case, growth was interrupted for nine years. ‘Warfare dendrochronology’ could help to evaluate potential environmental impacts of the Second World War on forest health and composition elsewhere in the European theatre.

Tree-ring stable isotopes, providing insight into drought-induced eco-physiological mechanisms, are frequently used to reconstruct past changes in growing season temperature and precipitation. Their climatic response is, however, still not fully understood, particularly for data originating from non-extreme, mid-latitude environments with differing ecological conditions. Here, we assess the response of δ(13)C, δ(18)O and tree-ring width (TRW) from a temperate mountain forest in the Austrian pre-Alps to climate and specific drought events. Variations in stem growth and isotopic composition of Norway spruce, common beech and European larch from dry, medium and moist sites are compared with records of sunshine, temperature, moisture, precipitation and cloud cover. Results indicate uniform year-to-year variations in δ(13)C and δ(18)O across sites and species, but distinct differences in TRW according to habitat and species. While the climate sensitivity of TRW is overall weak, the δ(13)C and δ(18)O chronologies contain significant signals with a maximum sensitivity to cloud cover changes (r = -0.72 for δ(18)O). The coherent inter-annual isotopic variations are accompanied by substantial differences in the isotopic signatures with offsets up to ∼3‰ for δ(13)C, indicating species-specific physiological strategies and varying water-use efficiencies. During severe summer drought, beech and larch benefit from access to deeper and moist soils, allowing them to keep their stomata open. This strategy is accompanied by an increased water loss through transpiration, but simultaneously enables enhanced photosynthesis. Our findings indicate the potential of tree-ring stable isotopes from temperate forests to reconstruct changes in cloud cover, and to improve knowledge on basic physiological mechanisms of tree species growing in different habitats to cope with soil moisture deficits.

Growth response to climate differs between species and elevation. Fir is the most drought-tolerant species. The mountain forests are robust to the climatic changes until now. Alpine mountain forests provide a wide range of ecological and socio-economic services. Climate change is predicted to challenge these forests, but there are still considerable uncertainties how these ecosystems will be affected. Here, we present a multispecies tree-ring network of 500 trees from the Berchtesgaden Alps (Northern Limestone Alps, Southeast Germany) in order to assess the performance of native mountain forest species under climate change conditions. The dataset comprises 180 spruce, 90 fir, 110 larch and 120 beech trees from different elevations and slope exposures. We analyse the species with respect to: (1) the general growth/climate response; (2) the growth reaction (GR) during the hot summer in 2003 and (3) the growth change (GC) resulting from increasing temperatures since the 1990s. Spruce is identified as the most drought-sensitive species at the lower elevations. Fir shows a high drought tolerance and is well suited with regard to climate change. Larch shows no clear pattern, and beech remains unaffected at lower elevations. The unprecedented temperature increase of the last decades did not induce any distinct GC. The mountain forests of the Berchtesgaden Alps appear to be robust within the climatic changes until now.