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Gaseous CO 2 concentrations and concomitant air temperatures were measured within a CO 2 -emitting valley-mofette in Central Italy. ‘Il Bossoleto’ is a bowl-shaped, 5 m deep depression with several active CO 2 vents that continuously emit high amounts of dry CO 2 gas. Using a meteorological measurement mast, air temperatures and CO 2 concentrations were recorded every 40 cm, from the bottom up to a vertical elevation of 6.4 m. The data reveal a transient, natural CO 2 gas lake with three daily phases: a stratified, a homogeneous (up to 80% CO 2 ) and an empty gas phase. The stratified gas lake builds up during the evening and night hours. After solar irradiation in the early morning, the lake evolves over a short time period into two distinct layers: at the bottom, a 2–2.6 m high homogenous gas lake with CO 2 concentrations up to 80% and on top of it a gas layer with low CO 2 concentrations. Due to infrared absorption by CO 2 the temperatures inside the homogenous lake rises up to 60 °C (greenhouse effect). During the morning hours thermal heating leads to a collapse and complete emptying of the gas lake within tens of minutes, leaving Bossoleto free of CO 2 during the day. [ABSTRACT FROM AUTHOR]

Abstract: Earth degassing specifically of carbon dioxide CO2 is of increasing interest with respect to the global carbon budget, related climate effects, earthquake and volcano eruption mechanisms, as well as plant physiological reactions in gas-rich environments. Investigations in all of these disciplines require the detection of surface CO2 degassing structures and quantification of their emissions. We introduce minimal thermal change detection based on infrared imaging as a new remote sensing tool for the detection of earth surface thermal anomalies suiting among others to discover earth degassing locations of any origin. The method allows for seamless areal search and monitoring of degassing structures in any terrain. As proof of concept infrared imaging measurements were performed at the Bossoleto vent on the eastern master fault of the Siena Graben (Tuscany, Italy). It is known for the migration of a large amount of CO2-rich gas from deep geothermal reservoirs. Field data acquired confirmed the qualification of the method. Detection of CO2 degassing locations from infrared image time series worked reliably and optimal detection conditions were identified (dry, calm, cloudless weather between dusk and dawn). A simple model of heat exchange processes involved and observed was developed. In a first attempt this model was applied to determine the gas exit temperature, the area of gas thermal reach and the gas flux from recorded image series. It is the first method that allows remote areal survey of mofette fields and the associated CO2 flux quantification sole from infrared image time series. [Copyright &y& Elsevier]

Abstract: Photosynthetic competence in vegetative and reproductive structures of the early-flowering Common Snowdrop (Galanthus nivalis L.) was studied by the use of chlorophyll (Chl) fluorescence techniques as well as of oxygen exchange measurements. The white Snowdrop flower consists of three outer tepals and three shorter inner ones, which latter are chararacterized by specific green marks, commonly considered as nectar guides. All the Chl-containing organs (leaves, inner tepals, stalks, capsules) examined were photosynthetically active showing medium to high potential quantum efficiencies of photosystem II () after dark adaption. With increasing photon flux densities electron transport rates, actual quantum yields and photochemical quenching coefficients of the main photosynthetic organs decreased in the order: leaf, stalk and tepal. At moderate PFDs the inner tepals reached maximum electron transport rates, which came up to about 60% of concomitant developing leaves. Maximum net photosynthesis of the inner tepals (1.9μmolO2 m−2 s−1) was about one-fourth of the fully developed leaves (7μmolO2 m−2 s−1). Apart from their main function in attracting and guiding animal pollinators, a second relevant function is proposed for the green patterned inner tepals in performing an efficient photosynthesis and providing the flower and the developing seeds with photo-assimilates. [Copyright &y& Elsevier]

In mofette fields, natural carbon dioxide springs, organisms have to stand extreme CO 2 concentrations up to 100%. These hostile conditions are spatially small-scaled and further influenced by earth tides, wind and temperature. The present project investigated the influence of increased atmospheric CO 2 concentration on spiders as representatives of above-ground organisms by means of pitfall traps in three mofette fields, differing in habitat conditions in the Plesná valley, eastern Cheb Basin, Czech Republic. Among the 71 recorded spider species four were rarely found in the Czech Republic. A canonical correspondence analysis revealed significant influences of environmental parameters on the spider assemblages. Two groups of spiders are clearly distinguishable, one being positively influenced by humidity and the second by temperature. A cluster analysis showed distinct and congruent results: spider assemblages of pitfall traps at spots with a mean CO 2 concentration above 7.6% grouped close together and this grouping was independent of site. At >7.6% CO 2 significantly fewer individuals and species were found in comparison to areas with lower CO 2 concentration. Between 2.5 and 10% CO 2 , spiders indicated increased CO 2 concentrations much more sensitively than endogeic organisms (Nematoda, Collembola) in a nearby mofette field. Unlike in nematodes, collembolans and plants, no mofettovageous or mofettophilous spiders were detected. In contrast to humidity, CO 2 concentration and temperature, the vegetation cover was not among the factors, which significantly influenced spiders. This is explained by the fact that mofettophilous plants occurred at spots where almost no spiders could live. In a field experiment, most Pardosa pullata males tested passed a 30 cm long corridor with increased carbon dioxide concentration. These results and that of pitfall traps showed that relatively large and wandering specimens respectively were able to transit moderately hostile spots. Further experiments are necessary to find out if there is any active avoidance of high-CO 2 areas by spiders. [ABSTRACT FROM AUTHOR]

Mofette fields, i.e. geogenic, cold CO2-exhaling gas vents occurring naturally in regions of tectonic or volcanic disturbances provide an excellent opportunity to investigate long-term responses of the soil biota to increased CO2 concentrations. The upper centimeters of mofette soils present a small-scale mosaic of different CO2 and O2 concentrations: From up to 100% CO2 and 0% O2 around local degassing vents to ambient soil atmosphere (<2% CO2). The present field study investigated the influence of CO2 on the community structure of Collembola as representatives of the air-filled fraction of the pore system and of Nematoda as inhabitants of soil water films. Canonical correspondence analyses revealed strong correlations between soil faunal communities and environmental measures, above all CO2 concentration, organic matter content and plant coverage. An increase in CO2 concentration was followed by a steady decline in collembolan and nematode species richness and collembolan densities, but below a threshold of 62% CO2 had no significant effect on overall nematode densities. Collembolans developed viable populations at up to 20% CO2, where some mofettophilous species had their highest densities and frequencies, but other more general species also occurred (66% of overall collembolan densities). Nematodes, on the other hand, maintained individual-rich populations at up to 62% CO2, but above 20% CO2 nematode communities consisted almost entirely (97.6%) of three mofettophilous species: one feeding on bacteria, one on fungi and one on plant roots. Likely a combination of active and passive life phases together with temporal and micro-scale changes in environmental conditions allows survival of few mofettophilous species under CO2 conditions too extreme for most other species. The finding that mofettophilous species maintained denser populations in high CO2 patches, with species optima between 3% and 40% CO2, indicates that they even profit from CO2 degassing, presumably via changes in food supply or due to the lack of competitors. [ABSTRACT FROM AUTHOR]

The precise date of the Laacher See eruption (LSE), central Europe's largest Late Pleistocene volcanic event that occurred around 13,000 years ago, is still unknown. Here, we outline the potential of combined high-resolution dendrochronological, wood anatomical and radiocarbon (14C) measurements, to refine the age of this major Plinian eruption. Based on excavated, subfossil trees that were killed during the explosive LSE and buried under its pyroclastic deposits, we describe how a firm date of the eruption might be achieved, and how the resulting temporal precision would further advance our understanding of the environmental and societal impacts of this event. Moreover, we discuss the relevance of an accurate LSE date for improving the synchronization of European terrestrial and lacustrine Late Glacial to Holocene archives. • Previous age estimates of the Laacher See Eruptions (LSE) around 12,900 years are still diverging and imprecise. • The combination of dendrochronology, wood anatomy, and 14C measurements holds the potential to establish a precise LSE date. • An absolute calendric date of the LSE would improve the synchronization of European Late Glacial to Holocene archives. [ABSTRACT FROM AUTHOR]