Annually resolved patterns of summer temperature over the Northern Hemisphere since AD 1400 from a tree-ring-density network

The development of annually-resolved estimates of summer temperature patterns over the mid-to-high latitudes of the Northern Hemisphere land masses is described. The estimates were derived from a calibration of an extensive network of tree-ring density chronologies, with data extending back as far as 1400 (though with greatly reduced spatial coverage prior to 1600). The chronology data were first gridded onto a 5° longitude by 5° latitude grid, followed by a local calibration and verification of each grid box series against observed April-to-September mean temperatures. It was demonstrated that calibration by simple linear regression of individual grid boxes in isolation (i.e., without using any non-local proxy or temperature information) yields a spatial reconstruction with suppressed variance when averaged over large areas. The local calibration was adapted, therefore, to ensure that the magnitude of sub-continental, regional-scale variations is realistically maintained, while still achieving significant skill at the grid-box scale. A second version of the reconstructed grids was also generated, by incorporating additional variations on century time scales that may have been removed by the original standardisation of the tree-ring density chronologies. The spatial extent of both versions (with and without the additional low-frequency variability) was extended using principal component regression, for all locations where a verification correlation of 0.4 or above was achieved. These reconstructions of summer temperature have significant skill, with an overall space-time correlation of around 0.7 for both the calibration and verification against observed temperatures

The climate sensitivity of Norway spruce [Picea abies (L.) Karst.] in the southeastern European Alps

Tree ring chronologies were developed from trees growing at two sites in Slovenia which differed in their ecological and climatological characteristics. Ring width, maximum latewood density, annual height increment and latewood cellulose carbon isotope composition were developed at both sites and time-series verified against instrumental climate data over the period (AD 1960–AD 2002). Ring width sensitivity to summer temperature is site-dependent, with contrasting responses at alpine and lowland sites. Maximum density responds to September temperatures, suggesting lignification after cell division has ended for the season. Stable carbon isotopes have great potential, responding to summer temperature at oth alpine and lowland stands. Height increment appears relatively insensitive to climate, and is likely to be dominated by local stand dynamics

An 11th century a.d. burnt granary at La Gravette, south-western France : preliminary archaeobotanical results

International audienceA thick layer of carbonised seeds was encountered in an 11th century a.d. room situated in the seigneurial part of the village of La Gravette. This paper presents the first results of charcoal and seed analyses which give information on the food products stored in the granary and on their arrangement there. Triticum aestivum/durum/turgidum was by far the most important stored crop, while Avena sp., then Hordeum vulgare, Secale cereale, Triticum monococcum and Vitis vinifera were secondary. Weeds were poorly represented. Charcoals were dominated by deciduous Quercus sp., and 11 additional wood taxa were recorded, including especially Fagus sylvatica, Fraxinus sp., Rosaceae, Corylus avellana, Acer campestre and Ulmus sp. According to the charcoal distribution, Quercus and Fagus were probably building materials while most of other taxa would have been used for basketry, wattling or joinery work. In the western part of the granary, naked wheat was stored in bulk. In the eastern part, various crops (at least naked wheat, barley, rye, oat and grape) were stored in small amounts, most of which were probably separated by light wooden structures. The cereal crops had largely been processed and cleaned. The stored products probably represent taxes paid to the lord who owned the granary

Resin tapping in Pinus pinaster: effects on growth and response function to climate

Dendrocronología sobre Pinus pinaster, como la recolección de resina y los factores climáticos han afectado a su crecimiento

Survival and long-term maintenance of tertiary trees in the Iberian Peninsula during the Pleistocene. First record of Aesculus L.

The Italian and Balkan peninsulas have been places traditionally highlighted as Pleistocene glacial refuges. The Iberian Peninsula, however, has been a focus of controversy between geobotanists and palaeobotanists as a result of its exclusion from this category on different occasions. In the current paper, we synthesise geological, molecular, palaeobotanical and geobotanical data that show the importance of the Iberian Peninsula in the Western Mediterranean as a refugium area. The presence of Aesculus aff. hippocastanum L. at the Iberian site at Cal Guardiola (Tarrasa, Barcelona, NE Spain) in the Lower– Middle Pleistocene transition helps to consolidate the remarkable role of the Iberian Peninsula in the survival of tertiary species during the Pleistocene. The palaeodistribution of the genus in Europe highlights a model of area abandonment for a widely-distributed species in the Miocene and Pliocene, leading to a diminished and fragmentary presence in the Pleistocene and Holocene on the southern Mediterranean peninsulas. Aesculus fossils are not uncommon within the series of Tertiary taxa. Many appear in the Pliocene and suffer a radical impoverishment in the Lower–Middle Pleistocene transition. Nonetheless some of these tertiary taxa persisted throughout the Pleistocene and Holocene up to the present in the Iberian Peninsula. Locating these refuge areas on the Peninsula is not an easy task, although areas characterised by a sustained level of humidity must have played an predominant role

Humans and fire: changing relations in early agricultural and built environments in the Zagros, Iran, Iraq

Fire-centred studies have recently been highlighted as powerful avenues for investigation of energy flows and relations between humans, materials, environments and other species. The aim in this paper is to evaluate this potential first by reviewing the diverse theories and methods that can be applied to investigate the ecological and social significance of anthropogenic fire, and second by applying these to new and existing data sets in archaeology. This paper examines how fire-centred approaches can inform on one of the most significant step-changes in human lifeways and inter-relations with environment and other species – the transition from mobile hunting-gathering to more sedentary agriculture in a key heartland of change, the Zagros region of Iraq and Iran, c. 12,000–8,000 BP. In the review and case studies multiple links are investigated between human fire use and environment, ecology, energy use, technology, the built environment, health, social roles and relations, cultural practices and catastrophic event

Stable oxygen isotopes in Romanian oak tree rings record summer droughts and associated large-scale circulation patterns over Europe

We present the first annual oxygen isotope record (1900 – 2016) from the latewood (LW) cellulose of oak trees (Quercus robur) from NW Romania. As expected, the results correlate negatively with summer relative humidity, sunshine duration and precipitation and positively with summer maximum temperature. Spatial correlation analysis reveals a clear signal reflecting drought conditions at a European scale. Interannual variability is influenced by large-scale atmospheric circulation and by surface temperatures in the North Atlantic Ocean and the Mediterranean Sea. There is considerable potential to produce long and well-replicated oak tree ring stable isotope chronologies in Romania which would allow reconstructions of both regional drought and large-scale circulation variability over southern and central Europe