scholarly journals Late Quaternary Climate Reconstruction and Lead-Lag Relationships of Biotic and Sediment-Geochemical Indicators at Lake Bolshoe Toko, Siberia

2021 ◽  
Vol 9 ◽  
Author(s):  
Boris K. Biskaborn ◽  
Larisa Nazarova ◽  
Tim Kröger ◽  
Lyudmila A. Pestryakova ◽  
Liudmila Syrykh ◽  
...  
Keyword(s):  
Time Series ◽  
Species Richness ◽  
Organic Carbon ◽  
Alpha Diversity ◽  
Sediment Geochemistry ◽  
Geochemical Data ◽  
Scaling Analysis ◽  
Diatom Species ◽  
Quaternary Climate ◽  
Hill Numbers

Millennial-scale climate change history in eastern Siberia and relationships between diatom diversity, paleoclimate, and sediment-geochemical lake system trajectories are still poorly understood. This study investigates multi-proxy time series reaching back to the Late Pleistocene derived from radiocarbon dated Lake Bolshoe Toko sediment cores, southeastern Yakutia, Russia. We analyzed diatoms, elements (XRF), minerals (XRD), grain-size, organic carbon, and included chironomid analyses and published pollen-data for quantitative paleoclimate reconstruction. Changes in diatom species abundances reveal repeated episodes of thermal stratification indicated by shifts from euplanktonic Aulacoseira to Cyclotella species. Chironomid and pollen-inferred temperature reconstruction reveal that the main shift between these diatom species is related to the onset of Holocene Thermal Maximum (HTM) at 7.1 cal ka BP. Comparison to other paleoclimate records along a north-south transect through Yakutia shows that the HTM was delayed as far south as the Stanovoy mountains. Relationships between sediment-geochemistry, paleoclimate variability and diatom species richness (alpha diversity) was tested in a moving temporal offset approach to detect lead-lag relationships. Sediment-geochemical data, mainly uniform during the Holocene, revealed strongest positive or negative correlations ahead of species richness changes. Mean July air temperature (TJuly) reconstructions correlate with both Hill numbers and relative assemblage changes indicated by sample scores of multidimensional scaling analysis (MDS) over the entire time series. We found that sediment organic carbon revealed distinct positive correlations, i.e., centennial-scale delay to increases in diatom effective richness (Hill numbers N0 and N2). We conclude that a lag of deposited organic carbon concentrations behind changes in diatom alpha diversity reveals that species richness can augment the production and thus sequestration of organic matter in comparable lake systems.

Total organic carbon and the preservation of organic-walled microfossils in Precambrian shale

Geology ◽  
2020 ◽  
Author(s):  
C.R. Woltz ◽  
S.M. Porter ◽  
H. Agić ◽  
C.M. Dehler ◽  
C.K. Junium ◽  
...  
Keyword(s):  
Species Richness ◽  
Organic Carbon ◽  
Total Organic Carbon ◽  
Microbial Degradation ◽  
Sedimentation Rate ◽  
Surface Pattern ◽  
Causal Factors ◽  
Eukaryotic Diversity ◽  
High Concentrations ◽  
Fossil Preservation

Much of our understanding of early eukaryote diversity and paleoecology comes from the record of organic-walled microfossils in shale, yet the conditions controlling their preservation are not well understood. It has been suggested that high concentrations of total organic carbon (TOC) inhibit the preservation of organic fossils in shale, and although this idea is supported anecdotally, it has never been tested. Here we compared the presence, preservational quality, and assemblage diversity of organic-walled microfossils to TOC concentrations of 346 shale samples that span the late Paleoproterozoic to middle Neoproterozoic in age. We found that fossil-bearing samples have significantly lower median TOC values (0.32 wt%, n = 189) than those containing no fossils (0.72 wt%, n = 157). Preservational quality, measured by the loss of surface pattern, density of pitting, and deterioration of wall margin, decreases as TOC increases. Species richness negatively correlates with TOC within the ca. 750 Ma Chuar Group (Arizona, USA), but no relationship is observed in other units. These results support the hypothesis that high TOC content either decreases the preservational quality or inhibits the preservation of organic-walled microfossils altogether. However, it is also possible that other causal factors, including sedimentation rate and microbial degradation, account for the correlation between fossil preservation and TOC. We expect that as TOC varies in space and time, so too does the probability of finding well-preserved fossils. A compilation of 13,940 TOC values spanning Earth history suggests significantly higher median TOC levels in Mesoproterozoic versus Neoproterozoic shale, potentially biasing the interpreted pattern of increased eukaryotic diversity in the Tonian.

scholarly journals Prediction of Soil Organic Carbon based on Landsat 8 Monthly NDVI Data for the Jianghan Plain in Hubei Province, China

2019 ◽  
Vol 11 (14) ◽  
pp. 1683 ◽  
Author(s):  
Yangchengsi Zhang ◽  
Long Guo ◽  
Yiyun Chen ◽  
Tiezhu Shi ◽  
Mei Luo ◽  
...  
Keyword(s):  
Time Series ◽  
Organic Carbon ◽  
Time Series Data ◽  
Soil Mapping ◽  
Digital Soil Mapping ◽  
Series Data ◽  
Landsat 8 ◽  
Auxiliary Variables ◽  
Jianghan Plain ◽  
Ndvi Time Series

High-precision maps of soil organic carbon (SOC) are beneficial for managing soil fertility and understanding the global carbon cycle. Digital soil mapping plays an important role in efficiently obtaining the spatial distribution of SOC, which contributes to precision agriculture. However, traditional soil-forming factors (i.e., terrain or climatic factors) have weak variability in low-relief areas, such as plains, and cannot reflect the spatial variation of soil attributes. Meanwhile, vegetation cover hinders the acquisition of the direct information of farmland soil. Thus, useful environmental variables should be utilized for SOC prediction and the digital mapping of such areas. SOC has an important effect on crop growth status, and remote sensing data can record the apparent spectral characteristics of crops. The normalized difference vegetation index (NDVI) is an important index reflecting crop growth and biomass. This study used NDVI time series data rather than traditional soil-forming factors to map SOC. Honghu City, located in the middle of the Jianghan Plain, was selected as the study region, and the NDVI time series data extracted from Landsat 8 were used as the auxiliary variables. SOC maps were estimated through stepwise linear regression (SLR), partial least squares regression (PLSR), support vector machine (SVM), and artificial neural network (ANN). Ordinary kriging (OK) was used as the reference model, while root mean square error of prediction (RMSEP) and coefficient of determination of prediction (R2P) were used to evaluate the model performance. Results showed that SOC had a significant positive correlation in July and August (0.17, 0.29) and a significant negative correlation in January, April, and December (−0.23, −0.27, and −0.23) with NDVI time series data. The best model for SOC prediction was generated by ANN, with the lowest RMSEP of 3.718 and highest R2P of 0.391, followed by SVM (RMSEP = 3.753, R2P = 0.361) and PLSR (RMSEP = 4.087, R2P = 0.283). The SLR model was the worst model, with the lowest R2P of 0.281 and highest RMSEP of 3.930. ANN and SVM were better than OK (RMSEP = 3.727, R2P = 0.372), whereas PLSR and SLR were worse than OK. Moreover, the prediction results using single-data NDVI or short time series NDVI showed low accuracy. The effect of the terrain factor on SOC prediction represented unsatisfactory results. All these results indicated that the NDVI time series data can be used for SOC mapping in plain areas and that the ANN model can maximally extract additional associated information between NDVI time series data and SOC. This study presented an effective method to overcome the selection of auxiliary variables for digital soil mapping in plain areas when the soil was covered with vegetation. This finding indicated that the time series characteristics of NDVI were conducive for predicting SOC in plains.

scholarly journals Breakdown coefficients and scaling properties of rain fields

1998 ◽  
Vol 5 (2) ◽  
pp. 93-104 ◽  
Author(s):  
D. Harris ◽  
M. Menabde ◽  
A. Seed ◽  
G. Austin
Keyword(s):  
Time Series ◽  
Parameter Estimation ◽  
Power Law ◽  
Scale Parameter ◽  
Probability Distributions ◽  
Scaling Analysis ◽  
Scaling Properties ◽  
Power Law Exponent ◽  
Scale Similarity ◽  
Parameter Estimation Techniques

Abstract. The theory of scale similarity and breakdown coefficients is applied here to intermittent rainfall data consisting of time series and spatial rain fields. The probability distributions (pdf) of the logarithm of the breakdown coefficients are the principal descriptor used. Rain fields are distinguished as being either multiscaling or multiaffine depending on whether the pdfs of breakdown coefficients are scale similar or scale dependent, respectively. Parameter  estimation techniques are developed which are applicable to both multiscaling and multiaffine fields. The scale parameter (width), σ, of the pdfs of the log-breakdown coefficients is a measure of the intermittency of a field. For multiaffine fields, this scale parameter is found to increase with scale in a power-law fashion consistent with a bounded-cascade picture of rainfall modelling. The resulting power-law exponent, H, is indicative of the smoothness of the field. Some details of breakdown coefficient analysis are addressed and a theoretical link between this analysis and moment scaling analysis is also presented. Breakdown coefficient properties of cascades are also investigated in the context of parameter estimation for modelling purposes.

scholarly journals Archaeal Communities in a Heterogeneous Hypersaline-Alkaline Soil

Archaea ◽  
2015 ◽  
Vol 2015 ◽  
pp. 1-11 ◽  
Author(s):  
Yendi E. Navarro-Noya ◽  
César Valenzuela-Encinas ◽  
Alonso Sandoval-Yuriar ◽  
Norma G. Jiménez-Bueno ◽  
Rodolfo Marsch ◽  
...  
Keyword(s):  
Species Richness ◽  
Alpha Diversity ◽  
Methanogenic Archaea ◽  
Archaeal Community ◽  
Soil Samples ◽  
Alkaline Soil ◽  
Alkaline Soils ◽  
Phylogenetic Information ◽  
Archaeal Communities ◽  
Saline Alkaline Soils

In this study the archaeal communities in extreme saline-alkaline soils of the former lake Texcoco, Mexico, with electrolytic conductivities (EC) ranging from 0.7 to 157.2 dS/m and pH from 8.5 to 10.5 were explored. Archaeal communities in the 0.7 dS/m pH 8.5 soil had the lowest alpha diversity values and were dominated by a limited number of phylotypes belonging to the mesophilic CandidatusNitrososphaera. Diversity and species richness were higher in the soils with EC between 9.0 and 157.2 dS/m. The majority of OTUs detected in the hypersaline soil were members of the Halobacteriaceae family. Novel phylogenetic branches in the Halobacteriales class were detected in the soil, and more abundantly in soil with the higher pH (10.5), indicating that unknown and uncharacterized Archaea can be found in this soil. Thirteen different genera of the Halobacteriaceae family were identified and were distributed differently between the soils.Halobiforma,Halostagnicola,Haloterrigena, andNatronomonaswere found in all soil samples. Methanogenic archaea were found only in soil with pH between 10.0 and 10.3. Retrieved methanogenic archaea belonged to the Methanosarcinales and Methanomicrobiales orders. The comparison of the archaeal community structures considering phylogenetic information (UniFrac distances) clearly clustered the communities by pH.

scholarly journals Seasonal hydrology drives rapid shifts in the flux and composition of dissolved and particulate organic carbon and major and trace ions in the Fraser River, Canada

2015 ◽  
Vol 12 (19) ◽  
pp. 5597-5618 ◽  
Author(s):  
B. M. Voss ◽  
B. Peucker-Ehrenbrink ◽  
T. I. Eglinton ◽  
R. G. M. Spencer ◽  
E. Bulygina ◽  
...  
Keyword(s):  
Time Series ◽  
Organic Carbon ◽  
Particulate Organic Carbon ◽  
Fraser River ◽  
Data Set ◽  
Inorganic Species ◽  
Rapid Changes ◽  
Spring Freshet ◽  
Daily Sampling ◽  
Dom Composition

Abstract. Rapid changes in the volume and sources of discharge during the spring freshet lead to pronounced variations in biogeochemical properties in snowmelt-dominated river basins. We used daily sampling during the onset of the freshet in the Fraser River (southwestern Canada) in 2013 to identify rapid changes in the flux and composition of dissolved material, with a focus on dissolved organic matter (DOM). Previous time series sampling (at twice monthly frequency) of dissolved inorganic species in the Fraser River has revealed smooth seasonal transitions in concentrations of major ions and tracers of water and dissolved load sources between freshet and base flow periods. In contrast, daily sampling reveals a significant increase in dissolved organic carbon (DOC) concentration (200 to 550 μmol L−1) occurring over a matter of days, accompanied by a shift in DOM optical properties, indicating a transition towards higher molecular weight, more aromatic DOM composition. Comparable changes in DOM composition, but not concentration, occur at other times of year, underscoring the role of seasonal climatology in DOM cycling. A smaller data set of total and dissolved Hg concentrations also showed variability during the spring freshet period, although dissolved Hg dynamics appear to be driven by factors beyond DOM as characterized here. The time series records of DOC and particulate organic carbon (POC) concentrations indicate that the Fraser River exports 0.25–0.35 % of its annual basin net primary productivity. The snowmelt-dominated hydrology, forested land cover, and minimal reservoir impoundment of the Fraser River may influence the DOC yield of the basin, which is high relative to the nearby Columbia River and of similar magnitude to that of the Yukon River to the north. Anticipated warming and decreased snowfall due to climate changes in the region may cause an overall decrease in DOM flux from the Fraser River to the coastal ocean in coming decades

Distribution of moss-inhabiting diatoms along an altitudinal gradient at sub-Antarctic Îles Kerguelen

2007 ◽  
Vol 19 (1) ◽  
pp. 17-24 ◽  
Author(s):  
Niek J.M. Gremmen ◽  
Bart van de Vijver ◽  
Yves Frenot ◽  
Marc Lebouvier
Keyword(s):  
Species Richness ◽  
Species Composition ◽  
Altitudinal Gradient ◽  
Cross Validation ◽  
Strong Relationship ◽  
Distribution Patterns ◽  
Common Species ◽  
Important Variable ◽  
Diatom Species ◽  
Expected Species Richness

Altitudinal gradients provide excellent opportunities to study relationships between species distribution and climatic variables. We studied the species composition of 39 samples of moss-inhabiting diatoms, collected at 50 m intervals from 100–650 m above sea level. The samples contained a total of 130 diatom species, of which 51 occurred in 10 or more samples. Altitude appeared to be the most important variable explaining variation in species composition. Of the 51 common species, 33 showed a significant relationship with altitude. Although the majority of the latter declined with increasing altitude, for nine species the probability of occurrence first increased with increasing elevation, but decreased again at higher altitudes, and four species increased systematically with elevation. As a result, expected species richness per sample decreased from an estimated 43 at 100 m to 25 species per sample at 650 m. Diatom distribution patterns proved to be suitable predictors of the altitudinal position of sample sites. Cross-validation yielded a strong relationship between predicted and observed altitudes.

scholarly journals Late quaternary temperature variability described as abrupt transitions on a 1/<i>f</i> noise background

2015 ◽  
Vol 6 (2) ◽  
pp. 2323-2337
Author(s):  
M. Rypdal ◽  
K. Rypdal
Keyword(s):  
Time Scales ◽  
Late Quaternary ◽  
Scaling Law ◽  
Temperature Variability ◽  
Climate System ◽  
Scaling Analysis ◽  
Noise Background ◽  
Quaternary Climate ◽  
Last Glaciation ◽  
Climate Noise

Abstract. We show that in order to have a scaling description of the climate system that is not inherently non-stationary, the rapid shifts between stadial and interstadial conditions during the last glaciation cannot be included in the scaling law. The same is true for the shifts between the glacial and interglacial states in the quaternary climate. When these events are omitted from a scaling analysis we find that the climate noise is consistent with a 1/f law on time scales from months to 105 years.

scholarly journals Palaeoenvironmental significance of Toarcian black shales and event deposits from southern Beaujolais, France

2013 ◽  
Vol 150 (4) ◽  
pp. 728-742 ◽  
Author(s):  
GUILLAUME SUAN ◽  
LOUIS RULLEAU ◽  
EMANUELA MATTIOLI ◽  
BAPTISTE SUCHÉRAS-MARX ◽  
BRUNO ROUSSELLE ◽  
...  
Keyword(s):  
Organic Carbon ◽  
Benthic Fauna ◽  
Black Shales ◽  
Geochemical Data ◽  
Storm Activity ◽  
Oceanic Anoxic Event ◽  
Carbon Isotope Excursion ◽  
Tropical Areas ◽  
Mass Flow Deposits ◽  
Induced Changes

AbstractNew sedimentological, biostratigraphical and geochemical data recording the Toarcian Oceanic Anoxic Event (T-OAE) are reported from a marginal marine succession in southern Beaujolais, France. The serpentinum and bifrons ammonite zones record black shales with high (1–10 wt%) total organic carbon contents (TOC) and dysoxia-tolerant benthic fauna typical of the ‘Schistes Carton’ facies well documented in contemporaneous nearby basins. The base of the serpentinum ammonite zone, however, differs from coeval strata of most adjacent basinal series in that it presents several massive storm beds particularly enriched in juvenile ammonites and the dysoxia-tolerant, miniaturized gastropod Coelodiscus. This storm-dominated interval records a marked negative 5‰ carbonate and organic carbon isotope excursion being time-equivalent with that recording storm- and mass flow-deposits in sections of the Lusitanian Basin, Portugal, pointing to the existence of a major tempestite/turbidite event over tropical areas during the T-OAE. Although several explanations remain possible at present, we favour climatically induced changes in platform morphology and storm activity as the main drivers of these sedimentological features. In addition, we show that recent weathering, most probably due to infiltration of O2-rich meteoric water, resulted in the preferential removal of 12C-enriched organic carbon, dramatic TOC loss and total destruction of the lamination of the black shale sequence over most of the studied exposure. These latter observations imply that extreme caution should be applied when interpreting the palaeoenvironmental significance of sediments lacking TOC enrichment and lamination from outcrops with limited surface exposures.

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