281 research outputs found
The construction of exact multipolar equilibria of the two-dimensional Euler equations
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Long and Short-Term Effects of Fire on Soil Charcoal of a Conifer Forest in Southwest Oregon
In 2002, the Biscuit Wildfire burned a portion of the previously established,
replicated conifer unthinned and thinned experimental units of the Siskiyou Long-Term
Ecosystem Productivity (LTEP) experiment, southwest Oregon. Charcoal C in pre and
post-fire O horizon and mineral soil was quantified by physical separation and a
peroxide-acid digestion method. The abrupt, short-term fire event caused O horizon
charcoal C to increase by a factor of ten to >200 kg C ha⁻¹. The thinned wildfire treatment
produced less charcoal C than unthinned wildfire and thinned prescribed fire treatments.
The charcoal formation rate was 1 to 8% of woody fuels consumed, and this percentage
was negatively related to woody fuels consumed, resulting in less charcoal formation with
greater fire severity. Charcoal C averaged 2000 kg ha⁻¹ in 0–3 cm mineral soil and may
have decreased as a result of fire, coincident with convective or erosive loss of mineral
soil. Charcoal C in 3–15 cm mineral soil was stable at 5500 kg C ha⁻¹. Long-term soil C
sequestration in the Siskiyou LTEP soils is greatly influenced by the contribution of
charcoal C, which makes up 20% of mineral soil organic C. This research reiterates the
importance of fire to soil C in a southwestern Oregon coniferous forest ecosystem.Keywords: Soil carbon,
Soil change,
Wildfire,
Pre- and post-fire measurement,
Black carbon,
Biscuit Wildfire,
Charcoal,
Peroxide-acid digestio
Comets, historical records and vedic literature
A verse in book I of Rigveda mentions a cosmic tree with rope-like aerial
roots held up in the sky. Such an imagery might have ensued from the appearance
of a comet having `tree stem' like tail, with branched out portions resembling
aerial roots. Interestingly enough, a comet referred to as `heavenly tree' was
seen in 162 BC, as reported by old Chinese records. Because of weak surface
gravity, cometary appendages may possibly assume strange shapes depending on
factors like rotation, structure and composition of the comet as well as solar
wind pattern. Varahamihira and Ballala Sena listed several comets having
strange forms as reported originally by ancient seers such as Parashara,
Vriddha Garga, Narada and Garga.
Mahabharata speaks of a mortal king Nahusha who ruled the heavens when Indra,
king of gods, went into hiding. Nahusha became luminous and egoistic after
absorbing radiance from gods and seers. When he kicked Agastya (southern star
Canopus), the latter cursed him to become a serpent and fall from the sky. We
posit arguments to surmise that this Mahabharata lore is a mythical recounting
of a cometary event wherein a comet crossed Ursa Major, moved southwards with
an elongated tail in the direction of Canopus and eventually went out of sight.
In order to check whether such a conjecture is feasible, a preliminary list of
comets (that could have or did come close to Canopus) drawn from various
historical records is presented and discussed.Comment: This work was presented in the International Conference on Oriental
Astronomy held at IISER, Pune (India) during November, 201
Predicting the exposure of diving grey seals to shipping noise.
There is high spatial overlap between grey seals and shipping traffic, and the functional hearing range of grey seals indicates sensitivity to underwater noise emitted by ships. However, there is still very little data regarding the exposure of grey seals to shipping noise, constraining effective policy decisions. Particularly, there are few predictions that consider the at-sea movement of seals. Consequently, this study aimed to predict the exposure of adult grey seals and pups to shipping noise along a three-dimensional movement track, and assess the influence of shipping characteristics on sound exposure levels. Using ship location data, a ship source model, and the acoustic propagation model, RAMSurf, this study estimated weighted 24-h sound exposure levels (10-1000 Hz) (SELw). Median predicted 24-h SELw was 128 and 142 dB re 1 μPa2s for the pups and adults, respectively. The predicted exposure of seals to shipping noise did not exceed best evidence thresholds for temporary threshold shift. Exposure was mediated by the number of ships, ship source level, the distance between seals and ships, and the at-sea behaviour of the seals. The results can inform regulatory planning related to anthropogenic pressures on seal populations
Seafloor character and sedimentary processes in eastern Long Island Sound and western Block Island Sound
Author Posting. © The Author(s), 2006. This is the author's version of the work. It is posted here by permission of Springer for personal use, not for redistribution. The definitive version was published in Geo-Marine Letters 26 (2006): 59-68, doi: 10.1007/s00367-006-0016-4.Multibeam bathymetric data and seismic-reflection profiles collected in eastern Long
Island and western Block Island Sounds reveal previously unrecognized glacial features and
modern bedforms. Glacial features include an ice-sculptured bedrock surface, a newly identified
recessional moraine, exposed glaciolacustrine sediments, and remnants of stagnant-ice-contact
deposits. Modern bedforms include fields of transverse sand waves, barchanoid waves, giant scour
depressions, and pockmarks. Bedform asymmetry and scour around obstructions indicate that net
sediment transport is westward across the northern par of the study area near Fishers Island and
eastward across the southern par near Great Gull Island.This work was supported by the Coastal and Marine Geology Program of the U.S. Geological Survey, the Connecticut Department of Environmental Protection, and the Atlantic Hydrographic Branch of the
National Oceanic and Atmospheric Administration
Seasonality and spatial heterogeneity of the surface ocean carbonate system in the northwest European continental shelf
In 2014–5 the UK NERC sponsored an 18 month long Shelf Sea Biogeochemistry research programme which collected over 1500 nutrient and carbonate system samples across the NW European Continental shelf, one of the largest continental shelves on the planet. This involved the cooperation of 10 different Institutes and Universities, using 6 different vessels. Additional carbon dioxide (CO2) data were obtained from the underway systems on three of the research vessels. Here, we present and discuss these data across 9 ecohydrodynamic regions, adapted from those used by the EU Marine Strategy Framework Directive (MSFD). We observed strong seasonal and regional variability in carbonate chemistry around the shelf in relation to nutrient biogeochemistry. Whilst salinity increased (and alkalinity decreased) out from the near-shore coastal waters offshore throughout the year nutrient concentrations varied with season. Spatial and seasonal variations in the ratio of DIC to nitrate concentration were seen that could impact carbon cycling. A decrease in nutrient concentrations and a pronounced under-saturation of surface pCO2 was evident in the spring in most regions, especially in the Celtic Sea. This decrease was less pronounced in Liverpool Bay and to the North of Scotland, where nutrient concentrations remained measurable throughout the year. The near-shore and relatively shallow ecosystems such as the eastern English Channel and southern North Sea were associated with a thermally driven increase in pCO2 to above atmospheric levels in summer and an associated decrease in pH. Non-thermal processes (such as mixing and the remineralisation of organic material) dominated in winter in most regions but especially in the northwest of Scotland and in Liverpool Bay. The large database collected will improve understanding of carbonate chemistry over the North-Western European Shelf in relation to nutrient biogeochemistry, particularly in the context of climate change and ocean acidification
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