Quaternary, Volume 2, Issue 4 (December 2019) – 6 articles

A 4 m core was extracted from the center of a peatland located in the Drugeon valley (France). Thirteen radiocarbon dates were used to build a robust age model. Testate amoebae were used for reconstructing mire surface wetness. High-resolution pollen analysis of the sequence reconstructed 9 millennia of development of the peatland and its surrounding vegetation. During the early/middle Holocene (9500 to 5800 cal BP), warm conditions led to high evapotranspiration and low water levels. The vegetation history is characterized by the development of a Pinus and a mixed Quercus forest. From 5800 cal BP, testate amoebae show wetter conditions, indicating the onset of the cooler Neoglacial period. The cooling is also evidenced by the development of Abies and Fagus trees, replacing the oak forest. The first indicators of human impact appear at about 4800 cal BP, and indicators of farming activity remains very rare until ca. 2600 cal BP, at the beginning of the Iron Age. The development of the peatland responded to climatic fluctuation until 2600 cal BP, after which human impact became the main driver. The last millennium has been characterized by sudden drying and the spread of pine on the peatland. Full article

The purpose of this Milankovitch review is to explain the significance of Quaternary DNA studies and the importance of the recent methodological advances that have enabled the study of late Quaternary remains in more detail, and the testing of new assumptions in evolutionary biology and phylogeography to reconstruct the past. The topic is wide, and this review is not intended to be an exhaustive account of all the aDNA work performed in the last three decades on late-Quaternary remains. Instead, it is a selection of relevant studies aimed at illustrating how aDNA has been used to reconstruct not only environments of the past, but also the history of many species including our own. Full article

Temperature-index modeling is used to determine the magnitude of temperature depression in the northern Sawatch Range required to maintain steady-state mass balances of six reconstructed glaciers at their extent during the local Last Glacial Maximum (LLGM), dated at ~21 ka. Assuming no significant differences in precipitation compared to modern values, mean annual temperatures in the region were on average 8.8 + 0.5/– 0.8 °C cooler than they are today. Allowing for modest (± 10 cm) increases or decreases in precipitation, required temperature depressions only differ by ±0.2 °C. Temperature depression in the northern Sawatch Range is consistent, although slightly greater, with those determined in other ranges in Colorado using similar approaches. The estimates presented here are, however, substantially less than those suggested by several downscaled simulations of global Last Glacial Maximum (LGM) climate, that might be due to the need for improved calibration of such downscaled simulations, or the models from which they are derived. Our estimates of LGM temperature depression are considerably greater than that previously determined in the study area and those in two other ranges in Colorado derived using different methodologies, the latter being most likely responsible for the discrepancies. Full article

The Toledo Mountains are a mid-elevation mountain range that separates the Tagus and Guadiana basins in the central area of the Iberian Peninsula. The location of these mountains allows the development of typical Mediterranean vegetation with some Atlantic influence. Consequently, typical broadleaved evergreen Mediterranean vegetation currently dominates the regional landscape, with the remarkable presence of more mesophilous species in sheltered and more humid microsites such as gorges (e.g., Prunus lusitanica, Taxus baccata, Ilex aquifolium) and mires/bogs (e.g., Betula pendula susbp. fontqueri, Erica tetralix, Myrica gale). Palaeoecological studies in these mountains are essential to understand the long-term ecology and original distribution of these valuable communities and are key to assess their resilience. Understanding the hazards and opportunities faced in the past by the plant communities of the Toledo Mountains is necessary to enhance the management and protection of those species currently threatened. This study focuses on El Perro mire, a peatland on the southern Toledo Mountains (central Spain) where climatic variability has played a major role in landscape dynamics at multi-decadal to millennial timescales. Climatic events such as the 4.2 ka cal. Before Present (BP) or the Little Ice Age triggered relevant landscape changes such as the spread and latter decline of birch and hazel forests. Human communities also seemed to be affected by these events, as their resilience was apparently jeopardized by the new climatic conditions and they were forced to find new strategies to cope with the new scenarios. Full article

The analysis of plant macrofossils in peatland ecosystems has been widely used for the climatic and ecological reconstruction of the Holocene in the high latitudes of the northern hemisphere. By contrast, perhaps associated with rarity of these ecosystems, this proxy has barely been explored for southern Europe. In this work, a compilation and review of existing knowledge on the study of plant macrofossils of peatlands in southern Europe has been carried out, both from a paleoenvironmental perspective and in terms of biodiversity dynamics. Although small in surface area, the peatlands of southern Europe stand out for their diversity (botanical, edaphogenic, morphological, etc.), which has allowed the recovery of a large number of macrofossils from both vascular plants and bryophytes. The southern zone of Europe contains refuge zones with a high plant diversity that have not suffered the intense glaciation of the northern zones, this allows a continuous record since the beginning of the Holocene and the detection of climatic events in lower latitudes, where the ice recession was earlier. Full article

It has recently been argued that pre-Columbian societies in the greater Amazon basin during the Late Holocene were subject to “adaptive cycling”. In this model, cultures practicing “intensive” land use practices, such as raised field agriculture, were vulnerable to perturbations in hydroclimate, whereas “extensive” land use patterns, such as polyculture agroforestry, are viewed as more resilient to climate change. On the basis of radiocarbon data, the relative rise and fall of late pre-Columbian cultures and their inferred patterns of land use in six regions are highlighted to exemplify this model. This paper re-examines the radiocarbon evidence marshalled in favour of adaptive cycling, demonstrating that alleged temporal patterning in these data are overwhelmingly likely due to a combination of sampling effects, lack of statistical controls, and unacknowledged uncertainties that are inherent to radiocarbon dating. The outcome of this combination of factors seriously limits the possibility of cross-referencing archaeological data with palaeo-ecological and -climatological data without controlling for these effects, undermining the central archaeological pillar in support of adaptive cycling in Amazonia. This paper illustrates examples of such mitigation measures and provides the code to replicate them. Suggestions for how to overcome the serious limitations identified in the Late Holocene radiocarbon record of Amazonia are presented in the context of ongoing debates on inferring climatic causation in archaeological and historical datasets. Full article