Charcoal from the Congo Basin : palaeo-botanical evidence for climate change?

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Growth trends reveal the forest structure during Roman and Medieval times in Western Europe: a comparison between archaeological and actual oak ring series (Quercus robur and Quercus petraea)

At some point in time, man has influenced nearly all forests in Western Europe. Most of the original forest cover has been converted to arable land and pastures, or has been cut for the supply of firewood and construction timber. In order to secure a sustainable source of firewood, the structure of the remaining forests was often altered. Especially coppice of European oak became increasingly popular during the Roman era and the Middle Ages. Ring-width series of oak trees from Roman times and Medieval settlements were recorded. In order to extract more detailed information regarding past forest structure and management, those series were compared to growth patterns of contemporary oak. The modern oaks were selected on forests sites in Flanders (northern Belgium) with well-known structure and management. Some remarkable similarities in growth patterns were observed. These findings yield tentative assumptions regarding past forest structure and management.Les tendances de croissance révèlent la structure des forêts en Europe Occidentale aux époques Romaines et Médiévales : comparaison entre séries d'accroissements annuels archéologiques et contemporains (Quercus robur et Q. petraea). Au cours de l’histoire, l’homme a influencé quasiment toutes les forêts en Europe. De grandes surfaces boisées ont été transformées en champs et pâtis ou ont été abattues pour récolter du bois de chauffage et de construction. Pour s’assurer d’une source durable de bois de chauffage, la structure des forêts restantes a souvent été adaptée. Surtout les bois de taillis de chêne sont devenus très populaires pendant la période romaine et au Moyen Âge. Des séries dendrochronologiques de chênes provenant d’établissements romains et médiévaux ont été analysées. Pour obtenir plus d’informations précises concernant la structure et la gestion des forêts antérieures, les séries ont été comparées avec celles de chênes contemporains. Ces chênes modernes ont été sélectionnés dans des forêts, avec des structures bien connues, situées en Flandres (Belgique). Quelques similarités remarquables observées dans les modèles de croissance ont permis de formuler des hypothèses concernant la structure et l’aménagement des forêts antérieures

A pHantastic ammonium response

Plant roots have to orchestrate their growth pattern to access available nutrients. Root architecture is governed by auxin that locally steers growth and development of lateral roots, thereby increasing the uptake capacity. A new mechanism for ammonium acquisition by influencing cellular auxin import has been defined

The earliest iron-producing communities in the Lower Congo region of Central Africa : new insights from the Bu, Kindu and Mantsetsi sites

In 2015 the KongoKing research project team excavated the Bu, Kindu and Mantsetsi sites situated in the Kongo-Central Province of the Democratic Republic of Congo (DRC). All are part of the Kay Ladio Group. This is the first detailed publication on this cultural group, to which no contemporary ones can currently be linked, either from the Atlantic coast of Congo-Brazzaville or from along the Congo River and its tributaries upstream of Kinshasa. Dated to between cal. AD 30 and 475, these settlements mark the presence of what are so far the oldest known iron-producing communities south of the Central African equatorial forest. Evidence for metallurgy is associated with remants of polished stone axes, which were perhaps being used for ritual purposes by this point in time. The charcoal remains found at the sites indicate a savanna environment that was more wooded in Kindu and Mantsetsi than in Bu

Influence of drought on tree rings and tracheid features of Pinus nigra and Pinus sylvestris in a mesic Mediterranean forest

We investigated the influence of climate on the ring width and xylem anatomy of two co-occurring pines (Pinus nigra Arn. and P. sylvestris L.) in the mountains of east-central Spain in order to test their utility for dendroclimatic reconstructions. We developed chronologies of ring width, mean lumen diameter and mean cell-wall thickness (in the earlywood, latewood, and the total annual ring) and the number of cells between 1960 and 2006. Drought, expressed as the standardized precipitation-evapotranspiration index (SPEI), was the main climatic driver of tree radial growth, although trees were also sensitive to temperature (negative effect in previous autumn and current summer) and precipitation (with a general positive effect). P. sylvestris response was stronger to climate of the current year, whereas the effect of previous-year climate was more important for P. nigra. Warm and dry summers reduced ring width, tracheid lumen, and wall thickness in both species, whereas warm winter-spring temperatures had the opposite effect, primarily for P. sylvestris. Previous-year or early-season conditions mainly affected earlywood features, whereas latewood was more responsive to summer climate. Overall, climate appeared to be a stronger limiting factor for P. sylvestris. During periods of drought, cell-wall thickness was reduced while lumen width increased in the latewood of P. sylvestris. This could compromise its hydraulic safety against drought-induced cavitation as our site was close to the southern and dry edge of the species distribution area. Our results suggest that anatomical variables record different and stronger climate information than ring width variables, especially in P. sylvestris. Reconstruction models for SPEI at the 3-month scale were developed for July–August and September– October using principal components regression. The best models included anatomical and width variables of both pine species suggesting that tracheid chronologies can be useful for drought reconstructions especially at mesic sites or with species that encode a mixed drought and temperature-precipitation signal