Moisture content can be a dominant factor affecting combustion especially in live fuels due to the wide range of moisture content that can be encountered with vegetation. Laboratory experiments are used to study the fire dynamics of Mediterranean Pinus halepensis needles under a range of fuel and flow conditions. A set of 80 experiments with good repeatability were conducted in the Fire Propagation Apparatus (FPA) fire calorimeter. The burning behavior is measured in terms of the evolution of the mass loss rate and the heat release rate from ignition till burn out for different forced flow velocities. Recently collected live and dead needles are compared here for the first time. Additionally, live samples aged for 15 months after collection are presented as an alternative to study changes in live needles. Two different moisture conditions are considered, fresh and oven-dry. The most flammable samples are fresh dead and 15 months aged needles, followed by oven-dry dead, and oven-dry live needles. The least flammable is fresh live needles. Overall, the results show that fire physics and chemistry vary with the fuel and flow conditions, and that moisture content is not the only difference between live and dead fuels, but that the needle bed physicochemical mechanisms matters as well. The loss of volatiles and other changes induced during oven drying is seen to lead to significant differences in the burning behavior.

Macrofossils (mostly leaves) and sporomorphs (pollen and spores) preserve conflicting records of plant biodiversity during the endPermian (P-Tr), Triassic-Jurassic (Tr-J), and end-Cretaceous (K-T) mass extinctions. Estimates of diversity loss based on macrofossils are typically much higher than estimates of diversity loss based on sporomorphs. Macrofossils from the Tr-J of East Greenland indicate that standing species richness declined by as much as 85% in the Late Triassic, whereas sporomorph records from the same region, and from elsewhere in Europe, reveal little evidence of such catastrophic diversity loss. To understand this major discrepancy, we have used a new high-resolution dataset of sporomorph assemblages from Astartekløft, East Greenland, to directly compare the macrofossil and sporomorph records of Tr-J plant biodiversity. Our results show that sporomorph assemblages from the Tr-J boundary interval are 10-12% less taxonomically diverse than sporomorph assemblages from the Late Triassic, and that vegetation composition changed rapidly in the boundary interval as a result of emigration and/or extirpation of taxa rather than immigration and/or origination of taxa. An analysis of the representation of different plant groups in the macrofossil and sporomorph records at Astartekløft reveals that reproductively specialized plants, including cycads, bennettites and the seed-fern Lepidopteris are almost absent from the sporomorph record. These results provide a means of reconciling the macrofossil and sporomorph records of Tr-J vegetation change, and may help to understand vegetation change during the P-Tr and K-T mass extinctions and around the PaleoceneEocene Thermal Maximum.ompilations of stratigraphic ranges of land plants through geological time do not show abrupt declines in taxonomic diversity (1-3). This contrasts sharply with the history of animal life, which is marked by five geologically rapid decreases in global taxonomic diversity, known as mass extinctions (4, 5). This fundamental difference between the evolutionary histories of plants and animals may be due to the persistence of higher plant taxa, and has led to the suggestion that plants are more resistant to mass extinction than animals (1, 6-9). Despite this, studies of fossil plants during times of faunal mass extinction have revealed extensive ecological disruption and decreased plant genus/species diversity on local and regional scales (8, 9), suggesting that plants are not immune to the myriad environmental changes accompanying mass extinctions.However, plant fossils preserve conflicting records of diversity loss during these critical intervals in Earth history. Estimates of diversity loss based on macrofossils (mostly leaves) are typically much higher than estimates of diversity loss based on sporomorphs (pollen and spores). The end-Permian mass extinction [P-Tr; ∼251 million years ago (Ma)] in Australia saw a 97% regional diversity loss of macrofossils but a 19% loss of sporomorph diversity (8, 10), and the end-Cretaceous mass extinct...

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.

It has been hypothesized that predecessors of today's bryophytes significantly increased global chemical weathering in the Late Ordovician, thus reducing atmospheric CO2 concentration and contributing to climate cooling and an interval of glaciations. Studies that try to quantify the enhancement of weathering by non-vascular vegetation, however, are usually limited to small areas and low numbers of species, which hampers extrapolating to the global scale and to past climatic conditions. Here we present a spatially explicit modelling approach to simulate global weathering by non-vascular vegetation in the Late Ordovician. We estimate a potential global weathering flux of 2.8 (km3 rock) yr−1, defined here as volume of primary minerals affected by chemical transformation. This is around three times larger than today's global chemical weathering flux. Moreover, we find that simulated weathering is highly sensitive to atmospheric CO2 concentration. This implies a strong negative feedback between weathering by non-vascular vegetation and Ordovician climate.

A high-resolution palaeoecological study of the shelly invertebrate macrofauna across two marine Triassic–Jurassic boundary sections in the UK (St. Audrie's Bay and Lavernock Point) is presented. Loss of taxonomic richness occurs in the upper Westbury Formation to lower Lilstock Formation (late Rhaetian), but if sample size is taken into account there is little convincing evidence of a catastrophic marine extinction. There is, however, good evidence for significant palaeoecological change in the benthic marine ecosystem at this time. The immediate post-event recovery interval in the upper Lilstock Formation is characterized by assemblages of low abundance, low diversity, high dominance and low evenness. Body-sizes of taxa that survived the event and originated afterwards were low until the later Hettangian. Recovery to higher abundance, higher diversity and higher evenness is recorded in the Psiloceras planorbis Zone. Recovery of the benthic ecosystem in the aftermath of the Late Triassic event was disrupted by marine anoxia and shows additional similarities to the (much slower) recovery that followed the Late Permian event. The pattern of body-size changes recorded in the shelly fossil record closely matches that of the trace fossil record. Shell thickness trends do not support a biocalcification crisis during the Late Triassic biotic event.