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The original version of this Article contained an error in the Data Availability section, which incorrectly read ‘All data will be freely available via https://www.ams.ethz.ch/research.html.’ The correct version states ‘http://www.ams.ethz.ch/research/published-data.html’ in place of ‘https://www.ams.ethz.ch/research.html’. This has been corrected in both the PDF and HTML versions of the Article.

Growth of old trees in cold-limited forests may benefit from recent climate warming and rising atmospheric CO2 concentrations (ca) if age-related constraints do not impair wood formation. To test this hypothesis, we studied old Mountain pine trees at three Pyrenean high-elevation forests subjected to cold-wet (ORD, AIG) or warmer-drier (PED) conditions. We analyzed long-term trends (1450–2008) in growth (BAI, basal area increment), maximum (MXD) and minimum (MID) wood density, and tree-ring carbon (δ13C) and oxygen (δ18O) isotope composition, which were used as proxies for intrinsic water-use efficiency (iWUE) and stomatal conductance (gs), respectively. Old pines showed positive (AIG and ORD) or stable (PED) growth trends during the industrial period (since 1850) despite being older than 400 years. Growth and wood density covaried from 1850 onwards. In the cold-wet sites (AIG and ORD) enhanced photosynthesis through rising ca was likely responsible for the post-1850 iWUE improvement. However, uncoupling between BAI and iWUE indicated that increases in iWUE were not responsible for the higher growth but climate warming. A reduction in gs was inferred from increased δ18O for PED trees from 1960 onwards, the warmest site where the highest iWUE increase occurred (34%). This suggests that an emergent drought stress at warm-dry sites could trigger stomatal closure to avoid excessive transpiration. Overall, carbon acquisition as lasting woody pools is expected to be maintained in aged trees from cold and high-elevation sites where old forests constitute unique long-term carbon reservoirs. We are very grateful to several projects financed by “Organismo Autónomo de Parques Nacionales” (projects 12/2008 387/2011). E.G. was funded by a Juan de la Cierva post-doctoral research contract (FJCI-2014-19615, MEC, Spain). Spanish (AMB95-0160, CGL2011-26654) and EU projects ISONET (contract EV K2-2001-00237) and MILLENNIUM (017008–2) also supported this study by contributing additional datasets.

The increasing carbon dioxide (CO2) concentration in the atmosphere in combination with climatic changes throughout the last century are likely to have had a profound effect on the physiology of trees: altering the carbon and water fluxes passing through the stomatal pores. However, the magnitude and spatial patterns of such changes in natural forests remain highly uncertain. Here, stable carbon isotope ratios from a network of 35 tree-ring sites located across Europe are investigated to determine the intrinsic water-use efficiency (iWUE), the ratio of photosynthesis to stomatal conductance from 19012000. The results were compared with simulations of a dynamic vegetation model (LPX-Bern 1.0) that integrates numerous ecosystem and landatmosphere exchange processes in a theoretical framework. The spatial pattern of tree-ring derived iWUE of the investigated coniferous and deciduous species and the model results agreed significantly with a clear south-to-north gradient, as well as a general increase in iWUE over the 20th century. The magnitude of the iWUE increase was not spatially uniform, with the strongest increase observed and modelled for temperate forests in Central Europe, a region where summer soil-water availability decreased over the last century. We were able to demonstrate that the combined effects of increasing CO2 and climate change leading to soil drying have resulted in an accelerated increase of iWUE. These findings will help to reduce uncertainties in the land surface schemes of global climate models, where vegetationclimate feedbacks are currently still poorly constrained by observational data.

Four Nordic temperature proxies based on tree growth at the northern timberline – ring-width from Sweden and Finland, maximum latewood density from Sweden, and height increment from Finland – were compared. Three indexing methods were used to enhance the low (centennial and above), medium (decadal-to-multidecadal) and high (decadal-to-interannual) frequencies. The proxies are shown to have a strong temperature signal (common variance) at the interannual-to-multidecadal scale, while the multidecadal-to-centennial trends are less coherent, perhaps reflecting intra-regional differences in growing conditions but more likely due to the more noisy regional curve standardization method used to retain the longest trends. Various methods of combining the four proxy series were explored and tested by comparison with four long temperature records from northern Fennoscandia. Only relatively high-frequency, spline-indexed series produced consistently positive verification statistics as a reconstruction model for summer temperature using all four proxies. Copyright © 2012 John Wiley & Sons, Ltd.

Minimum blue intensity measurements of resin-extracted Pinus sylvestris (L.) samples, conducted using a flat-bed scanner and commercially available software, are shown to provide a robust and reliable surrogate for maximum latewood density. Blue intensity data from 15 trees, from three stands, are reported relative to a standard blue-scale in a manner similar to grey-scale calibration in x-ray densitometry. The resulting time series are highly correlated with x-ray densitometry data generated from the same samples and preserve the same high level of signal strength. Sensitivity to summer climate variables is similar to that identified in the relative density record, demonstrating that minimum blue intensity can also be used for the study of climate change. While not a replacement for the powerful range of x-ray densitometry techniques, blue intensity provides an inexpensive and accessible alternative for accessing palaeoclimatic information.

The growth/climate relationship of theoretically temperature-controlled high-elevation forests has been demonstrated to weaken over recent decades. This is likely due to new tree growth limiting factors, such as an increasing drought risk for ecosystem functioning and productivity across the Mediterranean Basin. In addition, declining tree growth sensitivity to spring temperature may emerge in response to increasing drought stress. Here, we evaluate these ideas by assessing the growth/climate sensitivity of 1500 tree-ring width (TRW) and 102 maximum density (MXD) measurement series from 711 and 74 Pinus uncinata trees, respectively, sampled at 28 high-elevation forest sites across the Pyrenees and two relict populations of the Iberian System. Different dendroclimatological standardization and split period approaches were used to assess the high- to low-frequency behavior of 20th century tree growth in response to temperature means, precipitation totals and drought indices. Long-term variations in TRW track summer temperatures until about 1970 but diverge afterwards, whereas MXD captures the recent temperature increase in the low-frequency domain fairly well. On the other hand summer drought has increasingly driven TRW along the 20th century. Our results suggest fading temperature sensitivity of Iberian high-elevation P. uncinata forest growth, and reveal the importance of summer drought that is becoming the emergent limiting factor of tree ring width formation in many parts of the Mediterranean Basin. © 2014 Elsevier B.V., We thank the personnel of the PNOMP and PNAESM National Parks, A.Q. Alla and G. Sangüesa-Barreda for their help during the sampling and in dendrochronological analyses and also in making Fig. 1. We thank Loïc Schneider (WSL) for his collaboration in making Fig. A14. This study was supported by projects 012⁄2008 and 387⁄2011 (Organismo Autónomo Parques Nacionales, MMAMRM, Spain) and by a JAE-CSIC grant to J.D.G. J.J.C. acknowledges the support of ARAID. We also acknowledge funding by projects, which further contributed to build this data set (FoRmat EUENV4-CT97-0641, CiCyTAMB95-0160). We thank the editor and two anonymous reviewers for their constructive comments, which helped us to improve the manuscript.

Tree-ring widths from 880 living, dry dead, and subfossil northern Swedish pines (Pinus syl vestris L.) have been assembled into a continuous and precisely dated chronology (the Torneträsk chronology) covering the period 5407 BC to ad 1997. Biological trends in the data were removed with autoregressive standardization (ARS) to emphasize year-to-year variability, and with regional curve stan dardization (RCS) to emphasize variability on timescales from decades to centuries. The strong association with summer mean temperature (June–August) has enabled the production of a temperature reconstruction for the last 7400 years, providing information on natural summer-temperature variability on timescales from years to centuries. Numerous cold episodes, comparable in severity and duration to the severe summers of the seventeenth century, are shown throughout the last seven millennia. Particularly severe conditions suggested between 600 and 1 BC correspond to a known period of glacier expansion. The relatively warm conditions of the late twentieth century do not exceed those reconstructed for several earlier time intervals, although replication is relatively poor and confidence in the reconstructions is correspondingly reduced in the pre-Christian period, particularly around 3000, 1600 and 330 bc. Despite the use of the RCS approach in chronology construction, the 7400-year chronology does not express the full range of millennial-timescale temperature change in northern Sweden.

Times Cited: 0; International audience; Trees can take up and assimilate contaminants from the soil, subsurface, and groundwater. Contaminants in the transpiration stream can become bound or incorporated into the annual rings formed in trees of the temperate zones. The chemical analysis of precisely dated tree rings, called dendrochemistry, can be used to interpret past plant interactions with contaminants. This investigation demonstrates that dendrochemistry can be used to generate historical scenarios of past contamination of groundwater by chlorinated solvents at a site in Verl, Germany. Increment cores from trees at the Verl site were collected and analyzed by energy-dispersive X-ray fluorescence (EDXRF) line scanning. The EDXRF profiles showed four to six time periods where tree rings had anomalously high concentrations of chlorine (Cl) as an indicator of potential contamination by chlorinated solvents.

In New Zealand human cryptosporidiosis demonstrates spring and autumn peaks of incidence with the spring peak being three times greater in magnitude than the autumn peak. The imbalance between the two peaks is notable, and may be associated with the high livestock density in New Zealand. In the summer and autumn the cryptosporidiosis rate was positively associated with temperatures in the current and previous month, highlighting the importance of outdoor recreation to transmission. No associations between spring incidence and weather were found providing little support for the importance of drinking-water pathways. Imported travel cases do not appear to be an important factor in the aetiology of cryptosporidiosis in New Zealand.

In 1945 Storglaciaren located in the Kebnekaise massif, northern Sweden, was selected for a long term study of the climatic impact on glaciers and an annual mass balance programme was initiated. Si...

Mass balance measurements for the balance years 1985/86, 1986/87 and 1987/88 and calculations of the volume changes since the last maximum around 1915 have been carried out for Sydostra Kaskasatjak...