Holocene vegetation, climate and human impact in steppes around Lake Sevan (Armenia) based on a multiproxy approach: Pollen, NPPs and brGDGTs

2021 ◽  
Author(s):  
Mary Robles ◽  
Odile Peyron ◽  
Elisabetta Brugiapaglia ◽  
Guillemette Ménot ◽  
Lucas Dugerdil ◽  
...  
Keyword(s):  
Human Impact ◽  
Weighted Averaging ◽  
Lake Sevan ◽  
The Holocene ◽  
Modern Pollen ◽  
Climate Reconstructions ◽  
Multi Method Approach ◽  
The Impact ◽  
Multiproxy Approach ◽  
Method Approach

<p>In the Caucasus Mountains, the role of human influences and climate changes on steppes expansion over the Holocene is still discussed because this region is poorly documented. This study investigates (1) modern pollen-vegetation relationships in Armenia and (2) changes in vegetation, human activity and climate in the Holocene record of Vanevan peat (south-eastern shore of Lake Sevan) located in Armenia. The last 9700 years are recorded in the Vanevan core. We used a multiproxy approach including XRF, Pollen, Non-Pollen Palynomorphs (NPPs) and branched glycerol dialkyl glycerol tetraethers (brGDGTs) to reconstruct changes in vegetation, human impact and climate. The combination of these proxies is innovative and aims to distinguish the impact of human activities and climate change on vegetation. Modern pollen assemblages from semi-desert/steppe regions of Armenia show an abundance of Chenopodiaceae while meadows steppes, subalpine and alpine meadows are dominated by Poaceae. The Holocene vegetation at Vanevan is characterized by steppes dominated by Poaceae, <em>Artemisia</em> and Chenopodiaceae. However, several arboreal taxa, such as <em>Quercus, Betula, Carpinus betulus</em> and <em>Ulmus</em>, are more developed on slopes between 8600 and 5100 cal BP. Regarding the human impact, the presence of agriculture is attested since 5200 cal BP, largely increases during the last 2000 years cal BP (high percentages of <em>Cerealia</em>-type pollen) and correlates with the occupation periods reported in archeological studies. Palaeoclimate changes at Vanevan are estimated from (1) water level changes (2) temperature reconstructions based on brGDGTs (3) climate reconstructions based on pollen (through a multi-method approach: Modern Analogue Technique, Weighted Averaging Partial Least Squares regression, Random Forest, and Boosted Regression Trees). Climate reconstructions based on pollen and brGDGTs are rare and the multi-method approach using pollen data is innovative in the region. The results of Vanevan give evidence of high temperatures from 7900 to 5100 cal BP and arid events at 6000, 5000-4500 and 4200 cal BP, in agreement with other regional records.</p>

Impact of climate change on steppe environments around Lake Sevan in Armenia during the Holocene

2020 ◽  
Author(s):  
Mary Robles ◽  
Odile Peyron ◽  
Guillemette Ménot ◽  
Elisabetta Brugiapaglia ◽  
Vincent Ollivier ◽  
...  
Keyword(s):  
Climate Change ◽  
Aquatic Vegetation ◽  
Climate Reconstruction ◽  
Neolithic Period ◽  
The Caucasus ◽  
Lake Sevan ◽  
The Holocene ◽  
Impact Of Climate Change ◽  
Climate Reconstructions ◽  
The Impact

<p>Armenia is located in the Caucasus Mountains and today, its vegetation is largely dominated by steppes closely linked with human practices. Armenian human history roots back to the Neolithic period, which questions long human influences on steppe and therefore climate reconstructions from vegetation data. Moreover, vegetation records from this region are often low resolution and do not cover the entire Holocene. Pollen-based climate reconstruction coupled to independent climate reconstructions appear necessary to fully understand climate forcing in the region during the Holocene. In this study, we introduce high-resolution pollen, geochemical analyses and temperature reconstruction based on pollen and branched glycerol dialkyl glycerol tetraethers (brGDGTs) from Vanevan peat in Armenia. The wetland studied show major ecological changes observed through aquatic vegetation and sediment composition (XRF data). At the beginning of the Holocene, the study site is expected to be integrated in a larger Lake Sevan, then it became an independent lake and finally a peatland at 5700 cal BP. A drying phase is also attested around 4.2 kyrs, probably corresponding to the 4.2 ka climate event. Along the sequence, the vegetation is characterized by steppes dominated by Poaceae, Artemisia and Chenopodiaceae. However, forests composed of Quercus, Betula, Carpinus betulus and Ulmus, are more developed on slopes between 7600 cal BP and 5500 cal BP. Agriculture is observed since 5700 cal BP and correlates with occupation periods reported in archeological studies. Over this 10000 yrs-long record, we suppose that differences in response of wetland and vegetation to climate might be linked to ecological processes and human influence. The comparison between pollen-based climate reconstruction and temperature obtained with brGDGT calibrations promisingly illustrate these differences. Finally, we contextualize these results with other regional records to understand the impact of climate change on steppe vegetation in the Caucasus at a larger scale.</p>

scholarly journals Reconstructing burnt area during the Holocene: an Iberian case study

2021 ◽  
Author(s):  
Yicheng Shen ◽  
Luke Sweeney ◽  
Mengmeng Liu ◽  
Jose Antonio Lopez Saez ◽  
Sebastián Pérez-Díaz ◽  
...  
Keyword(s):  
Fire Regimes ◽  
Weighted Averaging ◽  
Pollen Data ◽  
Burnt Area ◽  
The Holocene ◽  
Quantitative Estimates ◽  
In Fire ◽  
The Impact ◽  
Pollen Records

Abstract. Charcoal accumulated in lake, bog or other anoxic sediments through time has been used to document the geographical patterns in changes in fire regimes. Such reconstructions are useful to explore the impact of climate and vegetation changes on fire during periods when the human influence was less prevalent than today. However, charcoal records only provide semi-quantitative estimates of change in biomass burning. Here we derive quantitative estimates of burnt area from vegetation data in two stages. First, we relate the modern charcoal abundance to burnt area using a conversion factor derived from a generalized linear model of burnt area probability based on eight environmental predictors. Then, we establish the relationship between fossil pollen assemblages and burnt area using Tolerance-weighted Weighted Averaging Partial Least-Squares with sampling frequency correction (fxTWA-PLS). We test this approach using the Iberian Peninsula as a case study because it is a fire-prone region with abundant pollen and charcoal records covering the Holocene. We derive the vegetation-burnt area relationship using the 29 records that have both modern and fossil charcoal and pollen data, and then reconstruct palaeo-burnt area for the 114 records with Holocene pollen records. The pollen data predict charcoal abundances through time relatively well (R2 = 0.47) and the changes in reconstructed burnt area are synchronous with known climate changes through the Holocene. This new method opens up the possibility of reconstructing changes in fire regimes quantitatively from pollen records, which are far more numerous than charcoal records.

scholarly journals Examining bias in pollen-based quantitative climate reconstructions induced by human impact on vegetation

2017 ◽  
Author(s):  
Wei Ding ◽  
Qinghai Xu ◽  
Pavel E. Tarasov
Keyword(s):  
Human Impact ◽  
Eastern China ◽  
General Pattern ◽  
Central China ◽  
Weighted Averaging ◽  
Mean Annual Precipitation ◽  
Past Climate ◽  
Climate Reconstructions ◽  
Calibration Sets ◽  
Human Impact On Vegetation

Abstract. Human impact is a well-known confounder in pollen-based quantitative climate reconstructions as most terrestrial ecosystems have been artificially affected to varying degrees. In this paper, we use a human-induced pollen dataset (H-set) and a corresponding natural pollen dataset (N-set) to establish pollen-climate calibration sets for temperate eastern China (TEC). The two calibration sets, taking a Weighted Averaging Partial Least Squares (WA-PLS) approach, are used to reconstruct past climate variables from a fossil record, which is located at the margin of the East Asian Summer Monsoon in north-central China and covers the late glacial–Holocene from 14.7 ka BP (thousand years before AD 1950). Ordination results suggest that mean annual precipitation (Pann) is the main explanatory variable of both pollen composition and percentage distributions in both datasets. The Pann reconstructions, based on the two calibration sets, demonstrate consistently similar patterns and general trends, suggesting a relatively strong climate impact on the regional vegetation and pollen spectra. However, our results also indicate that human impact may obscure climate signals derived from fossil pollen assemblages. In a test with modern climate and pollen data, the Pann influence on pollen distribution decreases in the H-set while the human influence index (HII) rises. Moreover, the relatively strong human impact reduces woody pollen taxa abundances, particularly in the sub-humid forested areas. Consequently, this shifts their model-inferred Pann optima to the arid-end of the gradient compared to Pann tolerances in the natural dataset, and further produces distinct deviations when the total tree pollen percentages are high in the fossil sequence (i.e. about 40 % for the Gonghai area). In summary, the calibration set with human impact used in our experiment can produce a reliable general pattern of past climate, but the human impact on vegetation affects the pollen-climate relationship and biases the pollen-based climate reconstruction.

scholarly journals The impact of methodological decisions on climate reconstructions using WA-PLS

2020 ◽  
pp. 1-16 ◽  
Author(s):  
Mark G. Turner ◽  
Dongyang Wei ◽  
Iain Colin Prentice ◽  
Sandy P. Harrison
Keyword(s):  
Reference Data ◽  
Training Data ◽  
Weighted Averaging ◽  
Data Set ◽  
Last Glacial Period ◽  
Methodological Choices ◽  
Climate Reconstructions ◽  
Significant Difference ◽  
Climate Space ◽  
The Impact

Abstract Most techniques for pollen-based quantitative climate reconstruction use modern assemblages as a reference data set. We examine the implication of methodological choices in the selection and treatment of the reference data set for climate reconstructions using Weighted Averaging Partial Least Squares (WA-PLS) regression and records of the last glacial period from Europe. We show that the training data set used is important because it determines the climate space sampled. The range and continuity of sampling along the climate gradient is more important than sampling density. Reconstruction uncertainties are generally reduced when more taxa are included, but combining related taxa that are poorly sampled in the data set to a higher taxonomic level provides more stable reconstructions. Excluding taxa that are climatically insensitive, or systematically overrepresented in fossil pollen assemblages because of known biases in pollen production or transport, makes no significant difference to the reconstructions. However, the exclusion of taxa overrepresented because of preservation issues does produce an improvement. These findings are relevant not only for WA-PLS reconstructions but also for similar approaches using modern assemblage reference data. There is no universal solution to these issues, but we propose a number of checks to evaluate the robustness of pollen-based reconstructions.

scholarly journals A Multi-Method Approach to a Comprehensive Examination of the Psychiatric and Neurological Consequences of Intimate Partner Violence in Women: A Methodology Protocol

2021 ◽  
Vol 12 ◽  
Author(s):  
Tara E. Galovski ◽  
Kimberly B. Werner ◽  
Katherine M. Iverson ◽  
Stephanie Kaplan ◽  
Catherine B. Fortier ◽  
...  
Keyword(s):  
Intimate Partner Violence ◽  
Head Injury ◽  
Partner Violence ◽  
Trauma Exposure ◽  
The United States ◽  
Intimate Partner ◽  
Self Report ◽  
Multi Method Approach ◽  
The Impact ◽  
Method Approach

The number of women in the United States that experience blows to the head during assaults by intimate partners is substantial. The number of head blows that result in a traumatic brain injury (TBI) is virtually unknown, but estimates far exceed numbers of TBI in parallel populations (e.g., blast exposure, accidents, sports) combined. Research on the impact of TBI on post-traumatic stress disorder (PTSD) in survivors of intimate partner violence (IPV) is sparse. This methodology paper describes the comprehensive, multi-method approach used by a multi-disciplinary team of investigators from several different fields of expertise to assess the interaction of psychiatric, cognitive, psychological, and physical conditions that result from IPV. Using state-of-the-art instruments, a comprehensive assessment of lifetime trauma exposure, lifetime history of TBI, psychiatric history, and a full assessment of current cognitive, neuropsychological and biomedical function was conducted with 51 female survivors of IPV who screened positive for PTSD. This multi-method assessment included clinician-administered diagnostic interviews modified to specifically assess the sequelae of IPV, standardized self-report surveys, neuropsychological tests, structural, diffusion, and functional neuroimaging and blood-based biomarkers. The specific details and full report of the results of the full study are beyond the scope of this methodology paper. Descriptive characteristics of the complex clinical presentation observed in this unique sample are described. The sample reported high rates of trauma exposure across the lifespan and 80% met full criteria for current PTSD. Women also reported high rates of lifetime subconcussive head injury (88.2%) and TBI (52.9%) from various etiologies (35.3% secondary to IPV). Descriptive findings from the methodological protocol described here have begun to reveal information that will advance our understanding of the impact of subconcussive head injury and TBI on recovery from mental injury among IPV survivors.

scholarly journals Examining bias in pollen-based quantitative climate reconstructions induced by human impact on vegetation in China

2017 ◽  
Vol 13 (9) ◽  
pp. 1285-1300 ◽  
Author(s):  
Wei Ding ◽  
Qinghai Xu ◽  
Pavel E. Tarasov
Keyword(s):  
Human Impact ◽  
General Pattern ◽  
Late Glacial ◽  
Central China ◽  
Weighted Averaging ◽  
Mean Annual Precipitation ◽  
Past Climate ◽  
Climate Reconstructions ◽  
Calibration Sets ◽  
Human Impact On Vegetation

Abstract. Human impact is a well-known confounder in pollen-based quantitative climate reconstructions as most terrestrial ecosystems have been artificially affected to varying degrees. In this paper, we use a human-induced pollen dataset (H-set) and a corresponding natural pollen dataset (N-set) to establish pollen–climate calibration sets for temperate eastern China (TEC). The two calibration sets, taking a weighted averaging partial least squares (WA-PLS) approach, are used to reconstruct past climate variables from a fossil record, which is located at the margin of the East Asian summer monsoon in north-central China and covers the late glacial Holocene from 14.7 ka BP (thousands of years before AD 1950). Ordination results suggest that mean annual precipitation (Pann) is the main explanatory variable of both pollen composition and percentage distributions in both datasets. The Pann reconstructions, based on the two calibration sets, demonstrate consistently similar patterns and general trends, suggesting a relatively strong climate impact on the regional vegetation and pollen spectra. However, our results also indicate that the human impact may obscure climate signals derived from fossil pollen assemblages. In a test with modern climate and pollen data, the Pann influence on pollen distribution decreases in the H-set, while the human influence index (HII) rises. Moreover, the relatively strong human impact reduces woody pollen taxa abundances, particularly in the subhumid forested areas. Consequently, this shifts their model-inferred Pann optima to the arid end of the gradient compared to Pann tolerances in the natural dataset and further produces distinct deviations when the total tree pollen percentages are high (i.e. about 40 % for the Gonghai area) in the fossil sequence. In summary, the calibration set with human impact used in our experiment can produce a reliable general pattern of past climate, but the human impact on vegetation affects the pollen–climate relationship and biases the pollen-based climate reconstruction. The extent of human-induced bias may be rather small for the entire late glacial and early Holocene interval when we use a reference set called natural. Nevertheless, this potential bias should be kept in mind when conducting quantitative reconstructions, especially for the recent 2 or 3 millennia.

A modern pollen–temperature calibration data set from Korea and quantitative temperature reconstructions for the Holocene

The Holocene ◽  
2011 ◽  
Vol 21 (7) ◽  
pp. 1125-1135 ◽  
Author(s):  
Jungjae Park
Keyword(s):  
Transfer Function ◽  
Correspondence Analysis ◽  
East Coast ◽  
Ice Age ◽  
Weighted Averaging ◽  
Calibration Data ◽  
Data Set ◽  
The Holocene ◽  
Modern Pollen ◽  
The Relationship

Modern surface pollen samples from the mountains along the east coast of Korea were used to derive pollen–temperature transfer functions. Detrended correspondence analysis (DCA) and detrended canonical correspondence analysis (DCCA) were performed to test the robustness of the relationship between the modern pollen assemblages and temperatures. The relationship exhibited a high correlation (DCA, r = −0.887; DCCA, r = −0.908). The performance of the best weighted averaging partial least squares (WA-PLS) transfer function was statistically good ([Formula: see text] = 0.74; RMSEP = 1.79°C). In order to quantitatively reconstruct the Holocene temperature changes, the best model was applied to five fossil pollen records produced from four coastal lagoons of the east coast and one high-altitude peat bog. Anomalies calculated from reconstructed paleotemperature data were combined to generate a synthesis temperature reconstruction for the east coast of Korea, in which the ‘Medieval Warm Period’, ‘Little Ice Age’, and ‘Migration Period’ were clearly shown. This study demonstrated the validity of the quantitative reconstruction of paleotemperature using the pollen–climate transfer function, even in heavily human-impacted areas such as the Korean Peninsula.

Understanding the Impact of Information Literacy Instruction: A Multi-Method Approach

2013 ◽  
Author(s):  
Melissa Gross ◽  
Don Latham
Keyword(s):  
Information Literacy ◽  
Literacy Instruction ◽  
Complex Problem ◽  
Formal Evaluation ◽  
Information Literacy Instruction ◽  
Multi Method Approach ◽  
The Impact ◽  
Method Approach ◽  
Multiple Interventions

This presentation summarizes the formal evaluation of an intervention developed for students who test as below proficient in information literacy. Findings demonstrate that the intervention can improve skills, but that the recalibration of self-views of ability and the attainment of competence is a complex problem that may require multiple interventions to be fully achieved.Cette communication résume l’évaluation formelle d’une intervention conçue pour les étudiants qui font preuve d’un manque de compétence informationnelle. Les résultats démontrent que l’intervention peut améliorer les compétences, mais que la recalibration de l’autoperception de la capacité et l’atteinte des compétences est un problème complexe qui nécessite de multiples interventions pour être pleinement corrigé.

scholarly journals Pollen-based temperature and precipitation inferences for the montane forest of Mt. Kilimanjaro during the last Glacial and the Holocene

2014 ◽  
Vol 10 (1) ◽  
pp. 195-234 ◽  
Author(s):  
L. Schüler ◽  
A. Hemp ◽  
H. Behling
Keyword(s):  
East Africa ◽  
Transfer Functions ◽  
Montane Forest ◽  
Weighted Averaging ◽  
Pollen Record ◽  
Climate Variables ◽  
The Holocene ◽  
Modern Pollen ◽  
Temperature And Precipitation ◽  
Pollen Rain

Abstract. The relationship between modern pollen-rain taxa and measured climate variables was explored along the elevational gradient of the southern slope of Mt. Kilimanjaro, Tanzania. Pollen assemblages in 28 pollen traps positioned on 14 montane forest vegetation plots were identified and their relationship with climate variables was examined using multivariate statistical methods. Canonical correspondence analysis revealed that the mean annual temperature, mean annual precipitation and minimum temperature each account for significant fractions of the variation in pollen taxa. A training set of 107 modern pollen taxa was used to derive temperature and precipitation transfer functions based on pollen subsets using weighted-averaging-partial-least-squares (WA-PLS) techniques. The transfer functions were then applied to a fossil pollen record from the montane forest of Mt. Kilimanjaro and the climate parameter estimates for the Late Glacial and the Holocene on Mt. Kilimanjaro were inferred. Our results present the first quantitatively reconstructed temperature and precipitation estimates for Mt Kilimanjaro and give highly interesting insights into the past 45 000 yr of climate dynamics in tropical East Africa. The climate reconstructions are consistent with the interpretation of pollen data in terms of vegetation and climate history of afro-montane forest in East Africa. Minimum temperatures above the frostline as well as increased precipitation turn out to be crucial for the development and expansion of montane forest during the Holocene. In contrast, consistently low minimum temperatures as well as about 25% drier climate conditions prevailed during the pre LGM, which kept the montane vegetation composition in a stable state. In prospective studies, the quantitative climate reconstruction will be improved by additional modern pollen rain data, especially from lower elevations with submontane dry forests and colline savanna vegetation in order to extend the reference climate gradient.

scholarly journals Paint It Red - A Multimethod Study of the Nudging Effect of Coloured Cycle Lanes

2021 ◽  
Vol 12 ◽  
Author(s):  
Aslak Fyhri ◽  
Katrine Karlsen ◽  
Hanne B. Sundfør
Keyword(s):  
Survey Data ◽  
Route Choice ◽  
Video Data ◽  
Gps Data ◽  
Field Surveys ◽  
Perceived Safety ◽  
Before And After ◽  
Multi Method Approach ◽  
The Impact ◽  
Method Approach

Many countries colour their cycle lanes, but there is still a lack of research into the impact of this policy. Rather than constraining or regulating movement, coloured asphalt conveys information, and can serve as a good example of a “nudge”. In transport, there are few good examples of effective nudges for improved safety or sustainability. We used a multi-method approach to study the behaviour and experiences of cyclists before and after cycle lanes were coloured using red asphalt. Video data were collected and analysed to measure the extent to which motorists stopped in the cycle lane; motorist distance from the cycle lane on passing; and bicycle placement in the cycle lane. Cyclists (n = 1583) were asked how they experienced the cycle lane in field surveys. GPS data from cyclists (n = 2448) was used to measure whether colouring the cycle lanes resulted in a change of cyclists’ route choice. Video data showed no significant decrease in the share of passing motorists who stopped in the cycle lane. However, there was a significant decrease in the share of motorists stopping in the cycle lane rather than in the car lane or on the pavement. After recoating, motorists also kept a greater distance from the cycle lane; a greater share of cyclists chose to cycle in the cycle lane and a lower share cycled on the pavement. Analysis of survey data showed that visibility, perceived safety and ease of visualisation improved more in the recoated streets than in control streets. Analysis of the GPS data revealed a significant increase in cycling in the first streets to get red asphalt, with mixed results for the later streets. We discuss possible mechanisms behind the effects observed, and whether coloured cycle lanes can be considered as a form of nudging.

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