Tree rings of Scots pine (Pinus sylvestris L.) as a source of information about past climate in northern Poland

Scots pine (Pinus sylvestris) is a very common tree in Polish forests, and therefore was widely used as timber. A relatively large amount of available wood allowed a long-term chronology to be built up and used as a source of information about past climate. The analysis of reconstructed indexed values of mean temperature in 51-year moving intervals allowed the recognition of the coldest periods in the years 1207–1346, 1383–1425, 1455–1482, 1533–1574, 1627–1646, and 1694–1785. The analysis of extreme wide and narrow rings forms a complementary method of examining climatic data within tree rings. The tree ring widths, early wood and late wood widths of 16 samples were assessed during the period 1581–1676. The most apparent effect is noted in the dry summer of 1616. According to previous research and our findings, temperature from February to March seems to be one of the most stable climatic factors which influenced pine growth in Poland. Correlation coefficients in the calibration and validation procedure gave promising results for temperature reconstruction from the pine chronology

Imaging of Disease Dynamics during Meningococcal Sepsis

Neisseria meningitidis is a human pathogen that causes septicemia and meningitis with high mortality. The disease progression is rapid and much remains unknown about the disease process. The understanding of disease development is crucial for development of novel therapeutic strategies and vaccines against meningococcal disease. The use of bioluminescent imaging combined with a mouse disease model allowed us to investigate the progression of meningococcal sepsis over time. Injection of bacteria in blood demonstrated waves of bacterial clearance and growth, which selected for Opa-expressing bacteria, indicating the importance of this bacterial protein. Further, N. meningitidis accumulated in the thyroid gland, while thyroid hormone T4 levels decreased. Bacteria reached the mucosal surfaces of the upper respiratory tract, which required expression of the meningococcal PilC1 adhesin. Surprisingly, PilC1 was dispensable for meningococcal growth in blood and for crossing of the blood-brain barrier, indicating that the major role of PilC1 is to interact with mucosal surfaces. This in vivo study reveals disease dynamics and organ targeting during meningococcal disease and presents a potent tool for further investigations of meningococcal pathogenesis and vaccines in vivo. This might lead to development of new strategies to improve the outcome of meningococcal disease in human patients

Spatio‐temporal patterns of tree growth as related to carbon isotope fractionation in European forests under changing climate

Aim To decipher Europe-wide spatiotemporal patterns of forest growth dynamics and their associations with carbon isotope fractionation processes inferred from tree rings as modulated by climate warming. Location Europe and North Africa (30‒70°N, 10°W‒35°E). Time period 1901‒2003. Major taxa studied Temperate and Euro-Siberian trees. Methods We characterize changes in the relationship between tree growth and carbon isotope fractionation over the 20th century using a European network consisting of 20 site chronologies. Using indexed tree-ring widths (TRWi), we assess shifts in the temporal coherence of radial growth across sites (synchrony) for five forest ecosystems (Atlantic, Boreal, cold continental, Mediterranean and temperate). We also examine whether TRWi shows variable coupling with leaf-level gas exchange, inferred from indexed carbon isotope discrimination of tree-ring cellulose (Δ13Ci). Results We find spatial autocorrelation for TRWi and Δ13Ci extending over up to 1,000 km among forest stands. However, growth synchrony is not uniform across Europe, but increases along a latitudinal gradient concurrent with decreasing temperature and evapotranspiration. Latitudinal relationships between TRWi and Δ13Ci (changing from negative to positive southwards) point to drought impairing carbon uptake via stomatal regulation for water saving occurring at forests below 60°N in continental Europe. A rise in forest growth synchrony over the 20th century together with increasingly positive relationships between TRWi and Δ13Ci indicate intensifying drought impacts on tree performance. These effects are noticeable in drought-prone biomes (Mediterranean, temperate and cold continental). Main conclusions At the turn of this century, convergence in growth synchrony across European forest ecosystems is coupled with coordinated warming-induced drought effects on leaf physiology and tree growth spreading northwards. Such a tendency towards exacerbated moisture-sensitive growth and physiology could override positive effects of enhanced leaf intercellular CO2 concentrations, possibly resulting in Europe-wide declines of forest carbon gain in the coming decades

Signal strength and climate calibration of a European tree-ring isotope network

We present the first European network of tree ring δ 13C and δ 18O, containing 23 sites from Finland to Morocco. Common climate signals are found over broad climatic-ecological ranges. In temperate regions we find positive correlations with summer maximum temperatures and negative correlations with summer precipitation and Palmer Drought Severity Indices (PDSI) with no obvious species-specific differences. Regional δ 13C and δ 18O chronologies share high common variance in year-to-year variations. Long-term variations, however, exhibit differences that may reflect spatial variability in environmental forcings, age trends and/or plant physiological responses to increasing atmospheric CO2 concentration. Rotated principal component analysis (RPCA) and climate field correlations enable the identification of four sub-regions in the δ 18O network - northern and eastern Central Europe, Scandinavia and the western Mediterranean. Regional patterns in the δ 13C network are less clear and are timescale dependent. Our results indicate that future reconstruction efforts should concentrate on δ 18O data in the identified European regions

Water-use efficiency and transpiration across European forests during the Anthropocene

International audienc

Water-use efficiency and transpiration across European forests during the Anthropocene

The Earth’s carbon and hydrologic cycles are intimately coupled by gas exchange through plant stomata. However, uncertainties in the magnitude and consequences of the physiological responses of plants to elevated CO2 in natural environments hinders modelling of terrestrial water cycling and carbon storage. Here we use annually resolved long-term 13C tree-ring measurements across a European forest network to reconstruct the physiologically driven response of intercellular CO2 (Ci) caused by atmospheric CO2 (Ca) trends. When removing meteorological signals from the 13C measurements, we find that trees across Europe regulated gas exchange so that for one ppmv atmospheric CO2 increase, Ci increased by 0.76 ppmv, most consistent with moderate control towards a constant Ci=Ca ratio. This response corresponds to twentieth-century intrinsic water-use efficiency (iWUE) increases of 14 ±10 and 22 ± 6% at broadleaf and coniferous sites, respectively. An ensemble of process-based global vegetation models shows similar CO2 effects on iWUE trends. Yet, when operating these models with climate drivers reintroduced, despite decreased stomatal opening, 5%increases in European forest transpiration are calculated over the twentieth century.This counterintuitive result arises from lengthened growing seasons, enhanced evaporative demand in a warming climate, and increased leaf area, which together oppose effects of CO2-induced stomatal closure. Our study questions changes to the hydrological cycle, such as reductions in transpiration and air humidity, hypothesized to result from plant responses to anthropogenic emissions

NOAA/WDS Paleoclimatology - European Tree-Ring Oxygen Isotope Network from 1600-2013 CE

This archived Paleoclimatology Study is available from the NOAA National Centers for Environmental Information (NCEI), under the World Data Service (WDS) for Paleoclimatology. The associated NCEI study type is Climate Reconstruction. The data include parameters of instrumental with a geographic location of Europe. The time period coverage is from 350 to -70 in calendar years before present (BP). See metadata information for parameter and study location details. Please cite this study when using the data