Pollen productivity estimates of key European plant taxa for quantitative reconstruction of past vegetation: a review

Information on the spatial distribution of past vegetation on local, regional and global scales is increasingly used within climate modelling, nature conservancy and archaeology. It is possible to obtain such information from fossil pollen records in lakes and bogs using the landscape reconstruction algorithm (LRA) and its two models, REVEALS and LOVE. These models assume that reliable pollen productivity estimates (PPEs) are available for the plant taxa involved in the quantitative reconstructions of past vegetation, and that PPEs are constant through time. This paper presents and discusses the PPEs for 15 tree and 18 herb taxa obtained in nine study areas of Europe. Observed differences in PPEs between regions may be explained by methodological issues and environmental variables, of which climate and related factors such as reproduction strategies and growth forms appear to be the most important. An evaluation of the PPEs at hand so far suggests that they can be used in modelling applications and quantitative reconstructions of past vegetation, provided that consideration of past environmental variability within the region is used to inform selection of PPEs, and bearing in mind that PPEs might have changed through time as a response to climate change. Application of a range of possible PPEs will allow a better evaluation of the results.     

Evaluating Swiss pollen productivity estimates using a simulation approach

We simulated pollen assemblages for 11 sites on the Swiss Plateau (Schweizer Mittelland) based on a low resolution land cover map and pollen productivity estimates (PPE) from this region. A comparison between observed and simulated pollen data demonstrated that the majority of the simulated pollen proportions were within a range of 5% of over- or underestimation, and that at eight of the 11 sites the dominant taxon was correctly estimated. The modelled sum of arboreal pollen was correct within ±11% at nine sites. Our results indicate that the PPE established for the Swiss Plateau can be used to simulate pollen assemblages with reasonable accuracy. Moreover, our results justify the use of the POLLSCAPE simulation using the Prentice-Sugita model and its variations of pollen dispersal and deposition in more complex topographic landscapes than those to which they have hitherto been applied.     

Neolithisation at the site Brandwijk-Kerkhof, the Netherlands: natural vegetation, human impact and plant food subsistence

Brandwijk-Kerkhof (ca. 4600 to 3630 cal b.c.) is a Neolithic site, located on a river dune in the Dutch Rhine/Maas river area. The natural vegetation and human impact upon it have been investigated by analysis of pollen and macroremains from four cores that are located at increasing distances up to 20 m from the site. The relationship between the strength of human impact on the vegetation and the distance of the cores from the river dune has been investigated as well. The results show that the natural vegetation on top of the river dune consisted of deciduous woodland, while in the surrounding wetlands alder carr and eutrophic marsh vegetation dominated. Human impact of limited strength resulted in more open and disturbed vegetation. There is no correlation between the strength of the evidence of human impact in the pollen diagrams and the distance of the cores from the river dune. The evidence for presence of crop plants from the cores is compared with evidence from the excavation. The first presence of crop plants from ca. 4200 b.c. onwards corresponds with data from other Dutch wetland sites. Large-scale local crop cultivation cannot however be demonstrated. Electronic supplementary material The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Woodland management at the Swedish middle Neolithic site of Alvastra? A new perspective

It is often argued that the repetitive removal of branches to improve the quantity and the quality of wood, i.e. woodland management, has been practiced in Europe from the Mesolithic and/or Neolithic onwards. The Neolithic pile dwelling of Alvastra in Sweden has been mentioned in textbooks as a classical example of this practice. The conclusion about woodland management at Alvastra was primarily based on palynological data, which do not provide any direct evidence. Is it correct to conclude that woodland management was practiced at Alvastra? To investigate that, this paper reviews the previous arguments and interpretations, focusing on wood data, and by comparing archaeological data with modern wood data. First, the assemblage of vertical posts from the latest excavations at Alvastra include a wide range of taxa, showing opportunistic use of the woody vegetation. Second, while the dendrochronological analysis of Quercus and Ulmus carried out in the 80 s has clearly indicated that the trees used for the posts grew under highly similar conditions and that particularly many Quercus trees started to grow more or less at the same time, the reason for the partially simultaneous start of growth remains unknown, and the posts used for the construction of the site do not provide evidence of repetitive removal of trunks from stools. Finally, analysis of the age/diameter data of the Corylus wood indicates the use of branches from unmanaged vegetation, while age data of Salix do not support management either. In conclusion, the data do not support the hypothesis of woodland management at Neolithic Alvastra, and it is most likely that people did not practice woodland management. This outcome corresponds to the conclusions in some of the previous publications about the site.

     

The burden of skin disease and eye disease due to onchocerciasis in countries formerly under the African Programme for Onchocerciasis Control mandate for 1990, 2020, and 2030

BackgroundOnchocerciasis (“river blindness”) can cause severe morbidity, including vision loss and various skin manifestations, and is targeted for elimination using ivermectin mass drug administration (MDA). We calculated the number of people with Onchocerca volvulus infection and onchocercal skin and eye disease as well as disability-adjusted life years (DALYs) lost from 1990 through to 2030 in areas formerly covered by the African Programme for Onchocerciasis Control.MethodsPer MDA implementation unit, we collated data on the pre-control distribution of microfilariae (mf) prevalence and the history of control. Next, we predicted trends in infection and morbidity over time using the ONCHOSIM simulation model. DALY estimates were calculated using disability weights from the Global Burden of Disease Study.ResultsIn 1990, prior to MDA implementation, the total population at risk was 79.8 million with 26.0 million (32.5%) mf-positive individuals, of whom 17.5 million (21.9%) had some form of onchocercal skin or eye disease (2.5 million DALYs lost). By 2030, the total population was predicted to increase to 236.1 million, while the number of mf-positive cases (about 6.8 million, 2.9%), people with skin or eye morbidity (4.2 million, 1.8%), and DALYs lost (0.7 million) were predicted to decline.ConclusionsMDA has had a remarkable impact on the onchocerciasis burden in countries previously under the APOC mandate. In the few countries where we predict continued transmission between now and 2030, intensified MDA could be combined with local vector control efforts, or the introduction of new drugs for mopping up residual cases of infection and morbidity.     

What’s in a hearth? Seeds and fruits from the Neolithic fishing and fowling camp at Bergschenhoek,The Netherlands,in a wider context

This paper presents new results from the Early Neolithic Dutch wetland site of Bergschenhoek (ca. 4200 cal b.c., Swifterbant Culture), which are compared with finds from similar features and sites. The data indicate the presence of predominantly eutrophic, nutrient-rich reed and forb vegetation and suggest the preparation of meals consisting of fish and fruits. The finds from the hearth, dominated by uncarbonised remains of wetland taxa, form a remarkable part of the find assemblage. Therefore, the discussion concerns assemblages, deposition processes and interpretations of uncarbonised and carbonised finds from hearths at comparable, contemporary sites. The wide variation of macroremains assemblages of hearths indicates that plant deposition in hearths is understood only partly and remains a topic for further research.     

Late Mesolithic and Early Neolithic human impact at Dutch wetland sites: the case study of Hardinxveld-Giessendam De Bruin

Evidence of human impact on the vegetation obtained from pollen diagrams at sites in the process of neolithisation is often difficult to detect. Apart from aspects like site function and occupation intensity, methodological aspects play a considerable role. In the Rhine-Meuse delta in the Netherlands, neolithisation is documented at the Final Mesolithic sites Hardinxveld-Giessendam Polderweg and Hardinxveld-Giessendam De Bruin and the local Early Neolithic sites of Brandwijk-Kerkhof and the Hazendonk, covering the period of 5500–2500 cal. b.c. The off-site core from Hardinxveld-Giessendam De Bruin supports earlier results that human influence on the vegetation at Hardinxveld is restricted and difficult to distinguish from natural vegetation disturbance. Human impact is more easily recognisable in the diagrams of Neolithic phases at Brandwijk-Kerkhof and the Hazendonk that show evidence of both domestic animals and cereals. Continuing neolithisation and also research methodology, including the location of the pollen cores, may play a role in this. It is tested whether the use of a new pollen sum excluding extra-regional taxa increases the visibility of human impact.     

Estimating past vegetation openness using pollen–vegetation relationships: A modelling approach

We used a modelling approach to assess past landscape openness in mid-Holocene natural vegetation. Two simple landscape scenarios were modelled: a first landscape was based on the “Vera cycle” hypothesis for western Europe, including different phases of herbivore-induced vegetation change and regeneration, while a second landscape was created based on views how a mid-Holocene natural vegetation may have looked like on the Swiss Plateau according to the closed canopy theory. These simulated landscapes were used to produce pollen assemblages by means of a pollen dispersal and deposition model. The resulting modelled pollen assemblages were then compared to a typical mid-Holocene pollen record from the Swiss Plateau. Our results indicated that the mid-Holocene pollen record is likely to be the result of a closed beech forest. However, the vegetation cover on the Swiss Plateau had components from both the closed woodland and the wood pasture landscape designs, with the latter likely at frequently disturbed or naturally open habitats.     

Microbotanical Evidence of Domestic Cereals in Africa 7000 Years Ago

The study of plant exploitation and early use of cereals in Africa has seen over the years a great input from charred and desiccated macrobotanical remains. This paper presents the results of one of the few examples in Africa of microbotanical analyses. Three grave contexts of phytolith-rich deposits and the dental calculus of 20 individuals were analysed from two Neolithic cemeteries in North and Central Sudan. The radiocarbon-dated phytoliths from the burial samples show the presence of Near East domestic cereals in Northern Sudan at least 7000 years ago. Phytoliths also indicate the exploitation of wild, savannah-adapted millets in Central Sudan between 7500 and 6500 years ago. The calculus samples contained starch grains from wheat/barley, pulses and millets, as well as panicoid phytoliths. This evidence shows that Near East domestic cereals were consumed in Northern Africa at least 500 years earlier than previously thought.