Global biomass burning: a synthesis and review of Holocene paleofire records and their controls

Plant exploitation and ethnopalynological evidence from the Wadi Teshuinat area (Tadrart Acacus, Libyan Sahara)

Taxonomic identification of pollen and spores uses inherently qualitative descriptions of morphology. Consequently, identifications are restricted to categories that can be reliably classified by multiple analysts, resulting in the coarse taxonomic resolution of the pollen and spore record. Grass pollen represents an archetypal example; it is not routinely identified below family level. To address this issue, we developed quantitative morphometric methods to characterize surface ornamentation and classify grass pollen grains. This produces a means of quantifying morphological features that are traditionally described qualitatively. We used scanning electron microscopy to image 240 specimens of pollen from 12 species within the grass family (Poaceae). We classified these species by developing algorithmic features that quantify the size and density of sculptural elements on the pollen surface, and measure the complexity of the ornamentation they form. These features yielded a classification accuracy of 77.5%. In comparison, a texture descriptor based on modelling the statistical distribution of brightness values in image patches yielded a classification accuracy of 85.8%, and seven human subjects achieved accuracies between 68.33 and 81.67%. The algorithmic features we developed directly relate to biologically meaningful features of grass pollen morphology, and could facilitate direct interpretation of unsupervised classification results from fossil material.

/pdf/classification-of-grass-pollen-through-the-quantitative-1wqrcygh9n.pdf

Classification of grass pollen through the quantitative analysis of surface ornamentation and texture

Despite the dominance of grasslands during the last glacial period, especially in South America, the highly uniform morphology of Poaceae pollen grains has so far allowed only very few palynological studies based on Poaceae pollen. In our study we compare two methods of distinguishing between South American grassland ecosystems based on quantitative morphology of Poaceae pollen grains. We investigated data sets from Paramo in southern Ecuador, Campos de Altitude and Campos in south-eastern and southern Brazil as well as data sets from the Pampa in Argentina by measuring the pollen grain length, grain width, pore diameter and annulus width. Firstly we investigated the potential influence of chemical treatment of pollen grains on pollen grain size as well as the measurement setting for defining the boundary conditions for using Poaceae pollen grains in a palaeoecological investigation. Finally the measured pollen grain parameters were analyzed by comparison of average grain length using statistical tests. This approach reveals highly significant differences in average grain size between all grassland ecosystems. Assuming that a certain grain size range can be assigned to a certain Poaceae taxon, conclusions about differences and similarities in taxa composition can be derived. We used two methods of multivariate data analysis. One uses the pollen grain parameters directly for a Principle Component Analysis (PCA). The other is an already established method in grassland ecology which defines parameter based pollen grain types to investigate similarities between grassland ecosystems. Both approaches confirm the results of the grain length analysis. In this work we demonstrate that the method we developed has the potential to provide acquisition of so far inaccessible information on spatial and temporal patterns and dynamics of South American grasslands.

https://link.springer.com/content/pdf/10.1007%2Fs00334-010-0265-z.pdf

Poaceae pollen grain size as a tool to distinguish past grasslands in South America: a new methodological approach

The transition to early agriculture on the North European Plain is a much debated issue in which emphasis is placed on the available pollen evidence. It has been suggested that cereal cultivation was probably practiced in the upland areas and surplus yields were brought to the wetland sites. An alternative model that gives special attention to crop assemblages, flooding, and yields and is illustrated with evidence from the type‐location sites of Swifterbant, dated between 4300 and 4000 BC, envisions cereal cultivation in the wetlands themselves. Evidence for early agriculture is found in particular in pollen diagrams, diatom analysis, and large numbers of cereal remains. It appears that small‐scale cereal cultivation may have been possible and attractive in addition to hunting and gathering in wetland sites because of their variety of biotopes, including areas suitable for agriculture.

/pdf/cereal-cultivation-at-swifterbant-neolithic-wetland-farming-1at93m13x7.pdf

Cereal cultivation at Swifterbant?: Neolithic Wetland Farming on the North European Plain

Grain and annulus diameter as criteria for distinguishing pollen grains of cereals from wild grasses

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Grain and annulus diameter as criteria for distinguishing pollen grains of cereals from wild grasses