scholarly journals An Icelandic freshwater radiocarbon reservoir effect: Implications for lacustrine 14C chronologies

The Holocene ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1073-1080 ◽  
Author(s):  
P.L. Ascough ◽  
G.T. Cook ◽  
H. Hastie ◽  
E. Dunbar ◽  
M.J. Church ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Age Differences ◽  
Trophic Levels ◽  
Data Set ◽  
Reservoir Effect ◽  
Age Correction ◽  
Freshwater System ◽  
Lake Mývatn

A freshwater radiocarbon (14C) reservoir effect (FRE) is a 14C age offset between the atmospheric and freshwater carbon reservoirs. FREs can be on the order of 10 000 14C yr in extreme examples and are a crucial consideration for 14C dating of palaeoenvironmental and archaeological samples. Correction for a FRE may be possible, provided the FRE and the proportion of FRE-affected carbon within a sample can be accurately quantified. However, although such correction is desirable for affected samples, it is essential that such correction is accurate in order to produce useful chronological information. Accuracy of FRE correction can be limited by spatial variation in FRE within a freshwater system, but despite this there is currently a paucity of information to identify and quantify such variability within affected systems. Here we present results of a study that investigates the effects of spatial FRE variation upon dating accuracy within the freshwater system of Lake Mývatn, northern Iceland. A substantial FRE (>10 000 14C yr) has previously been identified in archaeological and modern samples from the region, which shows the potential for considerable spatial variability. The study also assesses the use of δ13C and δ15N in age correction of affected samples. The results show that benthic detritus and organisms at primary trophic levels from locations within the lake are affected by a FRE of at least 3500 14C yr, with clear spatial variation resulting in 14C age differences of up to 7670 14C yr between samples. There is a broad correlation between stable isotope values and FRE within the data set. However, large associated uncertainties currently preclude highly accurate and precise stable isotope-based quantification of the proportion of FRE-affected carbon within archaeological and palaeoenvironmental samples from Mývatn and the surrounding region.

scholarly journals Effect of snow microstructure variability on Ku-band radar snow water equivalent retrievals

2019 ◽  
Vol 13 (11) ◽  
pp. 3045-3059 ◽  
Author(s):  
Nick Rutter ◽  
Melody J. Sandells ◽  
Chris Derksen ◽  
Joshua King ◽  
Peter Toose ◽  
...  
Keyword(s):  
Spatial Variability ◽  
Layer Thickness ◽  
Snow Water Equivalent ◽  
Estimation Accuracy ◽  
Snow Layer ◽  
Data Set ◽  
Snow Water ◽  
Retrieval Errors ◽  
Snow Microstructure ◽  
The Impact

Abstract. Spatial variability in snowpack properties negatively impacts our capacity to make direct measurements of snow water equivalent (SWE) using satellites. A comprehensive data set of snow microstructure (94 profiles at 36 sites) and snow layer thickness (9000 vertical profiles across nine trenches) collected over two winters at Trail Valley Creek, NWT, Canada, was applied in synthetic radiative transfer experiments. This allowed for robust assessment of the impact of estimation accuracy of unknown snow microstructural characteristics on the viability of SWE retrievals. Depth hoar layer thickness varied over the shortest horizontal distances, controlled by subnivean vegetation and topography, while variability in total snowpack thickness approximated that of wind slab layers. Mean horizontal correlation lengths of layer thickness were less than a metre for all layers. Depth hoar was consistently ∼30 % of total depth, and with increasing total depth the proportion of wind slab increased at the expense of the decreasing surface snow layer. Distinct differences were evident between distributions of layer properties; a single median value represented density and specific surface area (SSA) of each layer well. Spatial variability in microstructure of depth hoar layers dominated SWE retrieval errors. A depth hoar SSA estimate of around 7 % under the median value was needed to accurately retrieve SWE. In shallow snowpacks <0.6 m, depth hoar SSA estimates of ±5 %–10 % around the optimal retrieval SSA allowed SWE retrievals within a tolerance of ±30 mm. Where snowpacks were deeper than ∼30 cm, accurate values of representative SSA for depth hoar became critical as retrieval errors were exceeded if the median depth hoar SSA was applied.

scholarly journals Temporal and spatial variation of Myriapoda (Diplopoda and Chilopoda) assemblages in a Neotropical floodplain

2018 ◽  
Vol 18 (2) ◽  
Author(s):  
Lorhaine Santos-Silva ◽  
Tamaris Gimenez Pinheiro ◽  
Amazonas Chagas-Jr ◽  
Marinêz Isaac Marques ◽  
Leandro Dênis Battirola
Keyword(s):  
Spatial Variation ◽  
Habitat Type ◽  
Temporal Distribution ◽  
High Water ◽  
Trophic Levels ◽  
Temporal And Spatial Variation ◽  
Ecosystem Integrity ◽  
Mato Grosso ◽  
Temporal And Spatial ◽  
Hydrological Cycles

Abstract: Myriapods constitute important edaphic macrofauna taxa which dwell in different trophic levels and influence the dynamics of these environments. This study evaluated the variation in composition, richness and abundance of edaphic myriapod assemblages as a function of the distribution and structure of flooded and non-flooded habitats (spatial variation) and hydrological seasonality (temporal variation) in a floodplain of the northern Pantanal region of Mato Grosso, Brazil. Sampling was carried out in three areas of the Poconé Pantanal, along an altitudinal and inundation gradient consisting of inundated and non-inundated habitats and different vegetation formations. Three quadrats (10 x 10 m) were delimited within each habitat type, where sampling was performed using pitfall traps and mini-Winkler extractors during the dry, rising water, high water and receding water periods of two hydrological cycles within the Pantanal (2010/2011 and 2011/2012). A total of 549 millipedes were collected, consisting of 407 Diplopoda and 142 Chilopoda distributed in six orders, 12 families and 20 species. The assemblages composition varied throughout the seasonal periods, indicating that the rising water and dry periods differed from the high water and receding water periods. In addition to the variation between seasonal periods, myriapod richness and abundance also varied in relation to areas consisting of different vegetation formations. Thus, it can be concluded that the hydrological seasonality associated with the inundation gradient and different vegetation types were determinant in the heterogeneous spatial and temporal distribution of myriapod assemblages, validating that the conservation of these invertebrates in the Pantanal is directly linked to the preservation of vegetation, and consequently, ecosystem integrity.

scholarly journals Inter-community variability in total particle number concentrations in the eastern Los Angeles air basin

2010 ◽  
Vol 10 (23) ◽  
pp. 11385-11399 ◽  
Author(s):  
N. Hudda ◽  
K. Cheung ◽  
K. F. Moore ◽  
C. Sioutas
Keyword(s):  
Los Angeles ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Urban Areas ◽  
Particle Number ◽  
Meteorological Conditions ◽  
Monitoring Station ◽  
Size Distributions ◽  
Central Monitoring ◽  
Seasonal And Diurnal Variations

Abstract. Ultrafine Particles (UFP) can display sharp gradients in their number concentrations in urban environment due to their transient nature and rapid atmospheric processing. The ability of using air pollution data generated at a central monitoring station to assess exposure relies on our understanding of the spatial variability of a specific pollutant associated with a region. High spatial variation in the concentrations of air pollutants has been reported at scales of 10s of km for areas affected by primary emissions. Spatial variability in particle number concentrations (PNC) and size distributions needs to be investigated, as the representativeness of a monitoring station in a region is premised on the assumption of homogeneity in both of these metrics. This study was conducted at six sites, one in downtown Los Angeles and five located about 40–115 km downwind in the receptor areas of Los Angeles air basin. PNC and size distribution were measured using Condensation Particle Counters (CPC) and Scanning Mobility Particle Sizer (SMPS). The seasonal and diurnal variations of PNC implied that PNC might vary significantly with meteorological conditions, even though the general patterns at the sites may remain generally similar across the year due to consistency of sources around them. Regionally transported particulate matter (PM) from upwind urban areas of Los Angeles lowered spatial variation by acting as a "homogenizing" factor during favorable meteorological conditions. Spatial variability also increased during hours of the day during which the effects of local sources predominate. The spatial variability associated with PNC (quantified using Coefficients of Divergence, CODs), averaged about 0.3, which was generally lower than that based on specific size ranges. Results showed an inverse relationship of COD with particles size, with fairly uniform values in the particle range which is associated with regional transport. Our results suggest that spatial variability, even in the receptor regions of Los Angeles Basin, should be assessed for both PNC and size distributions, and should be interpreted in context of seasonal and diurnal influences, and suitably factored if values for exposure are ascertained using a central monitoring station.

Determinants of spatial variation in fire return period in a semiarid African savanna

2011 ◽  
Vol 20 (4) ◽  
pp. 540 ◽  
Author(s):  
T. G. O'Connor ◽  
C. M. Mulqueeny ◽  
P. S. Goodman
Keyword(s):  
Spatial Variation ◽  
Return Period ◽  
Vegetation Type ◽  
Fire Frequency ◽  
Fuel Load ◽  
Annual Rainfall ◽  
Vegetation Types ◽  
Terrestrial Vegetation ◽  
African Savanna ◽  
Data Set

Fire pattern is predicted to vary across an African savanna in accordance with spatial variation in rainfall through its effects on fuel production, vegetation type (on account of differences in fuel load and in flammability), and distribution of herbivores (because of their effects on fuel load). These predictions were examined for the 23 651-ha Mkuzi Game Reserve, KwaZulu-Natal, based on a 37-year data set. Fire return period varied from no occurrence to a fire every 1.76 years. Approximately 75% of the reserve experienced a fire approximately every 5 years, 25% every 4.1–2.2 years and less than 1% every 2 years on average. Fire return period decreased in relation to an increase in mean annual rainfall. For terrestrial vegetation types, median fire return periods decreased with increasing herbaceous biomass, from forest that did not burn to grasslands that burnt every 2.64 years. Fire was absent from some permanent wetlands but seasonal wetlands burnt every 5.29 years. Grazer biomass above 0.5 animal units ha–1 had a limiting influence on the maximum fire frequency of fire-prone vegetation types. The primary determinant of long-term spatial fire patterns is thus fuel load as determined by mean rainfall, vegetation type, and the effects of grazing herbivores.

Human and Dog Consumption of Fish on the Lower Ob River of Siberia: Evidence for a Major Freshwater Reservoir Effect at the Ust’-Polui Site

Radiocarbon ◽  
2017 ◽  
Vol 60 (1) ◽  
pp. 239-260 ◽  
Author(s):  
Robert J Losey ◽  
Lacey S Fleming ◽  
Tatiana Nomokonova ◽  
Andrei V Gusev ◽  
Natalia V Fedorova ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Age Differences ◽  
Dietary Patterns ◽  
Fish Bone ◽  
Archaeological Sites ◽  
Faunal Remains ◽  
Siberian Arctic ◽  
Freshwater Reservoir ◽  
Age Range ◽  
Stable Isotope Data

AbstractUst’-Polui is one of the most extensively studied archaeological sites in the western Siberian Arctic. New radiocarbon (14C) dates for charcoal, faunal remains, bark, hide, and human bone from this site are presented. When modeled, the charcoal dates span from ~260 BC to 140 AD, overlapping with the dendrochronology dates from the site. These dates also overlap with the expected age of the site based on artefact typology. 14C dates on reindeer bone have a slightly younger modeled age range, from ~110 BC to 350 AD. In contrast, dates on the site’s numerous dog remains, and on human and fish bone, all predate these modeled age ranges by over 500 years, despite being from the same deposits. Several sets of paired dates demonstrate significant age differences. Bone dates with lower δ13C values tend to be over 500 years older than those with higher δ13C values. Stable isotope data for the humans, dogs, and other faunal remains are also presented. These data suggest the dogs and the humans were regularly consuming freshwater fish. The dogs were probably fed fish by their human counterparts. Overall, the dog and human dietary patterns at Ust’-Polui created 14C dates biased with major freshwater reservoir effects.

Variability in organic matter lost by combustion in a boreal bog during the 2001 Chisholm fire

2003 ◽  
Vol 33 (12) ◽  
pp. 2509-2513 ◽  
Author(s):  
Brian W Benscoter ◽  
R Kelman Wieder
Keyword(s):  
Organic Matter ◽  
Species Composition ◽  
Spatial Variability ◽  
Spatial Variation ◽  
Fire Severity ◽  
Small Scale ◽  
Western Canada ◽  
Direct Combustion ◽  
Site Variation

Fire directly releases carbon (C) to the atmosphere through combustion of biomass. An estimated 1470 ± 59 km2 of peatland burns annually in boreal, western Canada, releasing 4.7 ± 0.6 Tg C to the atmosphere via direct combustion. We quantified within-site variation in organic matter lost via combustion in a bog peatland in association with the 116 000-ha Chisholm, Alberta, fire in 2001. We hypothesized that for peatlands with considerable small-scale microtopography (bogs and treed fens), hummocks will burn less than hollows. We found that hollows exhibit more combustion than hummocks, releasing nearly twice as much C to the atmosphere. Our results suggest that spatial variability in species composition and site hydrology within a landform and across a landscape could contribute to considerable spatial variation in the amounts of C released via combustion during peatland fire, although the magnitude of this variation may be dependent on fire severity.

scholarly journals Freshwater Reservoir Effect Variability in Northern Germany

Radiocarbon ◽  
2013 ◽  
Vol 55 (3) ◽  
pp. 1085-1101 ◽  
Author(s):  
Bente Philippsen ◽  
Jan Heinemeier
Keyword(s):  
Radiocarbon Dating ◽  
Potential Problem ◽  
Northern Germany ◽  
Reservoir Effect ◽  
The Past ◽  
Human Bones ◽  
Age Correction ◽  
Order Of Magnitude ◽  
Freshwater Reservoir ◽  
Reservoir Age

The freshwater reservoir effect is a potential problem when radiocarbon dating fish bones, shells, human bones, or food crusts on pottery from sites near rivers or lakes. The reservoir age in hardwater rivers can be up to several thousand years and may be highly variable. Accurate 14C dating of freshwater-based samples requires knowing the order of magnitude of the reservoir effect and its degree of variability. Measurements on modern riverine materials may not give a single reservoir age correction that can be applied to archaeological samples, but they show the order of magnitude and variability that can also be expected for the past. This knowledge will be applied to the dating of food crusts on pottery from the Mesolithic sites Kayhude at the Alster River and Schlamersdorf at the Trave River, both in Schleswig-Holstein, northern Germany.

Onset of Oceanic Anoxic Event 2 in the Lower Saxony Basin – Insights fromhigh-resolution stable isotope stratigraphy and geochemical modelling

2021 ◽  
Author(s):  
Pia Müller ◽  
Ulrich Heimhofer ◽  
Christian Ostertag-Henning
Keyword(s):  
Organic Matter ◽  
High Resolution ◽  
Stable Isotope ◽  
Carbon Cycle ◽  
Geochemical Modelling ◽  
Positive Anomaly ◽  
Lower Saxony ◽  
Data Set ◽  
Oceanic Anoxic Event ◽  
Anoxic Event

&lt;p&gt;The Oceanic Anoxic Event (OAE) 2 spanning the Cenomanian-Turonian boundary (93.5 Ma)&lt;br&gt;represents a major perturbation of the global carbon cycle and is marked by organic-rich&lt;br&gt;sediments deposited under oxygen-depleted conditions. In many studies the eruption of the&lt;br&gt;Caribbean LIP is considered to be the cause for rapidly increasing CO2 concentrations and&lt;br&gt;resulting global warming accompanied by widespread oceanic anoxia. In the Lower Saxony&lt;br&gt;Basin of northern Germany, the deposits of the OAE 2 are exposed in several industry drill&lt;br&gt;cores. In this study, the lower part of the OAE 2 has been studied in the HOLCIM 2011-3 drill&lt;br&gt;core. Sedimentary rocks are composed of limestones, marly limestones, marls and black&lt;br&gt;shales and have been analysed with a high-resolution stable isotope approach&lt;br&gt;(approximately one sample every 2 cm) combined with geochemical modelling. Using stable&lt;br&gt;carbon isotopes, bulk rock parameters and petrographic analysis, the onset of OAE 2 has&lt;br&gt;been investigated in detail. The high-resolution &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C curve exhibits overall stable values&lt;br&gt;around 3 &amp;#8240; before the onset of the Plenus event. This background level is interrupted by&lt;br&gt;three short-lived and small but significant negative carbon isotope excursions (CIEs) down to&lt;br&gt;&amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values of 2.5 &amp;#8240;, 2.7 &amp;#8240; and 1.9 &amp;#8240;. Immediately before the main rise in the Plenus bed,&lt;br&gt;a longer-lasting negative CIE down to 2.8 &amp;#8240; is observed, preceding the large positive CIE of&lt;br&gt;the OAE 2 to values of 5.2 &amp;#8240; over 33 ka. Thereafter, the &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C values decrease to 3.5 &amp;#8240; over&lt;br&gt;a period of approximately 130 ka. The results can be correlated with the lower-resolution&lt;br&gt;data set of Voigt et al. (2008) but enable a more accurate characterization of the subtle&lt;br&gt;features of the CIE and hence events before and during this time interval. Carbon cycle&lt;br&gt;modelling with the modelling software SIMILE using a model based on Kump &amp; Arthur (1999)&lt;br&gt;reveals that the negative excursion before the Plenus bed can be explained by a massive&lt;br&gt;volcanic pulse releasing of 0.95*10&lt;sup&gt;18&lt;/sup&gt; mol CO2 within 14 ka. This amount corresponds to only&lt;br&gt;81 % of the calculated volume of CO&lt;sub&gt;2&lt;/sub&gt; release during emplacement of the Caribbean LIP by&lt;br&gt;Joo et al. (2020). In the model the volcanic exhalation increases atmospheric CO&lt;sub&gt;2&lt;/sub&gt;&lt;br&gt;concentrations. This will increase global temperatures, intensify the hydrological cycle and&lt;br&gt;thus increase nutrient input into the ocean, resulting in an expansion of the oxygen minimum&lt;br&gt;zone, the development of anoxic conditions and an increase in the preservation potential for&lt;br&gt;organic material. In the model enhanced primary productivity and organic matter preservation&lt;br&gt;can be controlled by the implemented riverine phosphate input and the preservation factor for&lt;br&gt;organic matter. For the positive anomaly, the riverine phosphate input must be nearly&lt;br&gt;doubled (from 0.01 &amp;#956;mol/kg PO&lt;sub&gt;4 &lt;/sub&gt;to 0.019 &amp;#956;mol/kg) for the period of the increasing &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;br&gt;values (app. 33 ka), with a concomitant rise of the preservation factor from 1 % to 2 %. This&lt;br&gt;model scenario accurately reproduces the major features of the new high-resolution &amp;#948;&lt;sup&gt;13&lt;/sup&gt;C&lt;br&gt;record over the onset of the OAE 2 CIE.&lt;/p&gt;

scholarly journals Morphology and stable isotope analysis demonstrate different structuring of bat communities in rainforest and savannah habitats

2018 ◽  
Vol 5 (12) ◽  
pp. 180849 ◽  
Author(s):  
Ara Monadjem ◽  
Adam Kane ◽  
Peter Taylor ◽  
Leigh R. Richards ◽  
Grant Hall ◽  
...  
Keyword(s):  
Stable Isotope ◽  
Stable Isotope Analysis ◽  
Niche Breadth ◽  
Isotope Analysis ◽  
Morphological Characters ◽  
Trophic Levels ◽  
Species Packing ◽  
Dietary Niche ◽  
The One ◽  
Ellipse Area

Bats play important ecological roles in tropical systems, yet how these communities are structured is still poorly understood. Our study explores the structure of African bat communities using morphological characters to define the morphospace occupied by these bats and stable isotope analysis to define their dietary niche breadth. We compared two communities, one in rainforest (Liberia) and one in savannah (South Africa), and asked whether the greater richness in the rainforest was due to more species ‘packing’ into the same morphospace and trophic space than bats from the savannah, or some other arrangement. In the rainforest, bats occupied a larger area in morphospace and species packing was higher than in the savannah; although this difference disappeared when comparing insectivorous bats only. There were also differences in morphospace occupied by different foraging groups (aerial, edge, clutter and fruitbat). Stable isotope analysis revealed that the range of δ 13 C values was almost double in rainforest than in savannah indicating a greater range of utilization of basal C 3 and C 4 resources in the former site, covering primary productivity from both these sources. The ranges in δ 15 N, however, were similar between the two habitats suggesting a similar number of trophic levels. Niche breadth, as defined by either standard ellipse area or convex hull, was greater for the bat community in rainforest than in savannah, with all four foraging groups having larger niche breadths in the former than the latter. The higher inter-species morphospace and niche breadth in forest bats suggest that species packing is not necessarily competitive. By employing morphometrics and stable isotope analysis, we have shown that the rainforest bat community packs more species in morphospace and uses a larger niche breadth than the one in savannah.

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