Infrared remote sensing of Earth degassing - Ground study

Geodynamical processes e.g., volcanoes, often cause degassing at the Earth surface. The geogas emanates via mineral springs, water mofettes, or dry mofettes. It is assumed that the emerging gas influences the temperature of the spring or mofette water, respectively and the surface temperature of the soil at and around the dry gas vents. This causes a thermal anomaly in comparison to the close vicinity. Under specific conditions this effect should be extractable from remotely acquired infrared images allowing detection, mapping and monitoring of gas vents/springs within large areas and short times. This article describes preparatory investigations for which emanating Earth gas was simulated by leading compressed air into the ground and releasing it in some depth via a metal lance. The thermal effect at the surface was observed from a nearby thermovision camera in summer and winter under varying meteorological conditions. A procedure was developed to reliably identify gas release areas within the recorded thermal images of the scene. The investigations are aiming at studies to be performed later in the Western Bohemia (Czech Republic) earthquake swarm region where especially CO2 of magmatic origin from European SubContinental Mantle (ESCM) emanates

Why some stems are red: cauline anthocyanins shield photosystem II against high light stress

Red-stemmed plants are extremely common, yet the functions of cauline anthocyanins are largely unknown. The possibility that photoabatement by anthocyanins in the periderm reduces the propensity for photoinhibition in cortical chlorenchyma was tested for Cornus stolonifera. Anthocyanins were induced in green stems exposed to full sunlight. PSII quantum yields (ФPSII) and photochemical quenching coefficients were depressed less in red than in green stems, both under a light ramp and after prolonged exposures to saturating white light. These differences were primarily attributable to the attenuation of PAR, especially green/yellow light, by anthocyanins. However, the red internodes also had less chlorophyll and higher carotenoid:chlorophyll ratios than the green, and when the anthocyanic periderm was removed, small differences in the ФPSII of the underlying chlorenchyma were retained. Thus, light screening by cauline anthocyanins is important, but is only part of a set of protective acclimations to high irradiance. Hourly measurements of ФPSII on established trees under natural daylight indicated a possible advantage of red versus green stems under sub-saturating diffuse, but not direct sunlight. To judge the wider applicability of the hypothesis, responses to high light were compared for red and green stems across five further unrelated species. There was a strong, linear, interspecific correlation between photoprotective advantage and anthocyanin concentration differences among red and green internodes. The photoprotective effect appears to be a widespread phenomenon

Towards a dendrochronologically refined date of the Laacher See Eruption

The precise date of the Laacher See eruption (LSE), central Europe’s largest Late Pleistocene volcanic event that occurred around 12,900 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 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, and outline how the proposed, interdisciplinary dating approach can be applied to other large, yet undated, volcanic eruptions

Precise date for the Laacher See eruption synchronizes the Younger Dryas

The Laacher See eruption (LSE) in Germany ranks among Europe’s largest volcanic events of the Upper Pleistocene. Although tephra deposits of the LSE represent an important isochron for the synchronization of proxy archives at the Late Glacial to Early Holocene transition, uncertainty in the age of the eruption has prevailed. Here we present dendrochronological and radiocarbon measurements of subfossil trees that were buried by pyroclastic deposits that frmly date the LSE to 13,006 ± 9 calibrated years before present (bp; taken as ad 1950), which is more than a century earlier than previously accepted. The revised age of the LSE necessarily shifts the chronology of European varved lakes relative to the Greenland ice core record, thereby dating the onset of the Younger Dryas to 12,807 ± 12 calibrated years bp, which is around 130 years earlier than thought. Our results synchronize the onset of the Younger Dryas across the North Atlantic–European sector, preclude a direct link between the LSE and Greenland Stadial-1 cooling, and suggest a large-scale common mechanism of a weakened Atlantic Meridional Overturning Circulation under warming condition

Seasonal Dynamics of Mobile Carbon Supply in Quercus aquifolioides at the Upper Elevational Limit

Many studies have tried to explain the physiological mechanisms of the alpine treeline phenomenon, but the debate on the alpine treeline formation remains controversial due to opposite results from different studies. The present study explored the carbon-physiology of an alpine shrub species (Quercus aquifolioides) grown at its upper elevational limit compared to lower elevations, to test whether the elevational limit of alpine shrubs (<3 m in height) are determined by carbon limitation or growth limitation. We studied the seasonal variations in non-structural carbohydrate (NSC) and its pool size in Q. aquifolioides grown at 3000 m, 3500 m, and at its elevational limit of 3950 m above sea level (a.s.l.) on Zheduo Mt., SW China. The tissue NSC concentrations along the elevational gradient varied significantly with season, reflecting the season-dependent carbon balance. The NSC levels in tissues were lowest at the beginning of the growing season, indicating that plants used the winter reserve storage for re-growth in the early spring. During the growing season, plants grown at the elevational limit did not show lower NSC concentrations compared to plants at lower elevations, but during the winter season, storage tissues, especially roots, had significantly lower NSC concentrations in plants at the elevational limit compared to lower elevations. The present results suggest the significance of winter reserve in storage tissues, which may determine the winter survival and early-spring re-growth of Q. aquifolioides shrubs at high elevation, leading to the formation of the uppermost distribution limit. This result is consistent with a recent hypothesis for the alpine treeline formation

Effects of elevated soil CO2 concentration on growth and competition in a grass-clover mix

To investigate potential environmental affects in the context of carbon dioxide (CO2) leakage from Carbon Capture and Storage (CCS) schemes. The ASGARD (Artificial Soil Gassing and Response Detection) facility was established, where CO2 can be injected into the soil in replicated open-air field plots. Eight plots were sown with a grass-clover mix, with four selected for CO2 treatment while four were left as controls. Observations of sward productivity throughout the study allowed three effects to be distinguished: a direct stress response to soil gassing, limiting productivity in both species but with a greater effect on the clover; competition between the grass and clover affected by their differential stress responses; and an overall temporal trend from dominance by clover to dominance by grass in CO2 treatments. The direct effect of soil CO2 (or associated oxygen (O2) deprivation due to the high levels of CO2 in the soil) gave estimated reductions in productivity of 42% and 41% in grass, compared to 66% and 32% for clover in the high and low CO2 gassed zones respectively. Canopy CO2 increased by 70 parts per million (ppm) for every 1% increase in soil CO2 and a significant positive response of stomatal conductance in clover was observed; although carbon acquisition by the plants should not therefore be impeded, the reduction in productivity of the gassed plants is indicative of carbon-based metabolic costs probably related to soil CO2 affecting root physiology. Biomass measurements made after gassing has ceased indicated that recovery of vegetation was close to complete after 12 months

Photosynthetic performance and nutrient status of Norway spruce (Picea abies [L.] Karst. at forest sites of the Ore mountains (Erzgebirge)

Pfanz H, Beyschlag W. Photosynthetic performance and nutrient status of Norway spruce (Picea abies [L.] Karst. at forest sites of the Ore mountains (Erzgebirge). Trees, Struct. Funct. 1993;7:115-122