Extending the applicability of the REVEALS model for pollen-based vegetation reconstructions to coastal lagoons

The Holocene ◽  
2019 ◽  
Vol 29 (7) ◽  
pp. 1109-1112
Author(s):  
Julien Azuara ◽  
Florence Mazier ◽  
Vincent Lebreton ◽  
Shinya Sugita ◽  
Nicolas Viovy ◽  
...  
Keyword(s):  
Environmental Changes ◽  
Coastal Lagoons ◽  
Pollen Dispersal ◽  
Local Scale ◽  
Mechanistic Models ◽  
Pollen Data ◽  
Plant Abundance ◽  
Quantitative Reconstruction ◽  
Quantitative Estimates ◽  
Lake Deposits

Quantitative reconstruction of past plant abundance from fossil pollen data is still a challenging task for palynologists. During the last decades, mechanistic methods have been developed to convert pollen assemblages from peat and lake deposits into vegetation abundance at regional and local scale. Coastal areas are particularly sensitive to climate and environmental hazards. Thus, quantitative estimates of past vegetation are important to better understand their history and address potential effects of future environmental changes. However, assumptions of the mechanistic models of pollen dispersal and deposition originally designed for near-circular lakes and bogs located inland are violated when applied to coastal sites because of different basin shape and wind direction distribution. This study investigates how to adapt a model of pollen dispersal and deposition developed for lakes to coastal lagoons. A new geometry is defined, and it is demonstrated how some of the major formulas from previous models can be used without any modification in this singular context.

scholarly journals Pollen productivity estimates strongly depend on assumed pollen dispersal II: Extending the ERV model

The Holocene ◽  
2021 ◽  
pp. 095968362110417
Author(s):  
Martin Theuerkauf ◽  
John Couwenberg
Keyword(s):  
Model Selection ◽  
Pollen Dispersal ◽  
Local Scale ◽  
Pollen Deposition ◽  
Data Sets ◽  
Pollen Data ◽  
Modern Pollen ◽  
Dispersal Model ◽  
Pollen Productivity ◽  
Fall Speed

Pollen productivity estimates (PPEs) are a key parameter for quantitative land-cover reconstructions from pollen data. PPEs are commonly estimated using modern pollen-vegetation data sets and the extended R-value (ERV) model. Prominent discrepancies in the existing studies question the reliability of the approach. We here propose an implementation of the ERV model in the R environment for statistical computing, which allows for simplified application and testing. Using simulated pollen-vegetation data sets, we explore sensitivity of ERV application to (1) number of sites, (2) vegetation structure, (3) basin size, (4) noise in the data, and (5) dispersal model selection. The simulations show that noise in the (pollen) data and dispersal model selection are critical factors in ERV application. Pollen count errors imply prominent PPE errors mainly for taxa with low counts, usually low pollen producers. Applied with an unsuited dispersal model, ERV tends to produce wrong PPEs for additional taxa. In a comparison of the still widely applied Prentice model and a Lagrangian stochastic model (LSM), errors are highest for taxa with high and low fall speed of pollen. The errors reflect the too high influence of fall speed in the Prentice model. ERV studies often use local scale pollen data from for example, moss polsters. Describing pollen dispersal on his local scale is particularly complex due to a range of disturbing factors, including differential release height. Considering the importance of the dispersal model in the approach, and the very large uncertainties in dispersal on short distance, we advise to carry out ERV studies with pollen data from open areas or basins that lack local pollen deposition of the taxa of interest.

Environmental evolution and anthropogenic forcing in the Garigliano coastal plain (Italy) during the Holocene

The Holocene ◽  
2021 ◽  
pp. 095968362110032
Author(s):  
Halinka Di Lorenzo ◽  
Pietro Aucelli ◽  
Giuseppe Corrado ◽  
Mario De Iorio ◽  
Marcello Schiattarella ◽  
...  
Keyword(s):  
Human Activity ◽  
Coastal Plain ◽  
Forest Cover ◽  
Environmental Changes ◽  
Pollen Data ◽  
Human Environment ◽  
The Holocene ◽  
Natural Processes ◽  
History Of ◽  
The Rich

The Garigliano alluvial-coastal plain, at the Latium-Campania border (Italy), witnessed a long-lasting history of human-environment interactions, as demonstrated by the rich archaeological knowledge. With the aim of reconstructing the evolution of the landscape and its interaction with human activity during the last millennia, new pollen results from the coastal sector of the Garigliano Plain were compared with the available pollen data from other nearby sites. The use of pollen data from both the coastal and marine environment allowed integrating the local vegetation dynamics within a wider regional context spanning the last 8000 years. The new pollen data presented in this study derive from the analysis of a core, drilled in the coastal sector, which intercepted the lagoon-marshy environments that occurred in the plain as a response to the Holocene transgression and subsequent coastal progradation. Three radiocarbon ages indicate that the chronology of the analyzed core interval ranges from c. 7200 to c. 2000 cal yr BP. The whole data indicate that a dense forest cover characterized the landscape all along the Prehistoric period, when a few signs of human activity are recorded in the spectra, such as cereal crops, pasture activity and fires. The main environmental changes, forced by natural processes (coastal progradation) but probably enhanced by reclamation works, started from the Graeco-Roman period and led to the reduction of swampy areas that favoured the colonisation of the outer plain.

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 Key parameters for landscape evolution and anthropogenisation estimation in the Kamchia River downstream region (Eastern Bulgaria)

2021 ◽  
Vol 5 (1) ◽  
pp. 86-93
Author(s):  
Stoyan Ivanov Vergiev ◽  
Mariana Filipova-Marinova ◽  
Daniela Toneva ◽  
Todorka Stankova ◽  
Diyana Dimova ◽  
...  
Keyword(s):  
Source Area ◽  
Critical Parameters ◽  
Vegetation Composition ◽  
Pollen Data ◽  
Plant Abundance ◽  
Pollen Type ◽  
Modern Pollen ◽  
Downstream Region ◽  
Pollen Productivity ◽  
Gis Environment

Pollen productivity еstimate (PPE) and relevant source area of pollen (RSAP) are critical parameters for quantitative interpretations of pollen data in palaeolandscape and palaeoecological reconstructions, and for analyses of the landscapes evolution and anthropogenisation as well. In light of this, the present paper endeavours to calculate PPE of key plant taxa and to define the RSAP in the Kamchia River Downstream Region (Eastern Bulgaria) in order to use them in landscape simulations and estimations. For the purposes of this research, a dataset of pollen counts from 10 modern pollen samples together with corresponding vegetation data, measured around each sample point in concentric rings, were collected in 2020. Three submodels of the Extended R-Value (ERV) model were used to relate pollen percentages to vegetation composition. Therewith, in order to create a calibrated model, the plant abundance of each pollen type was weighed by distance in GIS environment. The findings led to the conclusion that most of the tree taxa have PPE higher than 1 (ERV3 submodel). Cichoriceae, Fabaceae and Asteraceae have lower PPE.

scholarly journals Dynamics of the Methanogenic Archaea in Tropical Estuarine Sediments

Archaea ◽  
2013 ◽  
Vol 2013 ◽  
pp. 1-13 ◽  
Author(s):  
María del Rocío Torres-Alvarado ◽  
Francisco José Fernández ◽  
Florina Ramírez Vives ◽  
Francisco Varona-Cordero
Keyword(s):  
Organic Carbon ◽  
Environmental Variables ◽  
Environmental Changes ◽  
Coastal Lagoons ◽  
Spatial Dynamics ◽  
Methanogenic Archaea ◽  
Estuarine Sediments ◽  
Microbiological Analysis ◽  
Methanogenic Community ◽  
Solids Content

Methanogenesis may represent a key process in the terminal phases of anaerobic organic matter mineralization in sediments of coastal lagoons. The aim of the present work was to study the temporal and spatial dynamics of methanogenic archaea in sediments of tropical coastal lagoons and their relationship with environmental changes in order to determine how these influence methanogenic community. Sediment samples were collected during the dry (February, May, and early June) and rainy seasons (July, October, and November). Microbiological analysis included the quantification of viable methanogenic archaea (MA) with three substrates and the evaluation of kinetic activity from acetate in the presence and absence of sulfate. The environmental variables assessed were temperature, pH, Eh, salinity, sulfate, solids content, organic carbon, and carbohydrates. MA abundance was significantly higher in the rainy season (106–107 cells/g) compared with the dry season (104–106 cells/g), with methanol as an important substrate. At spatial level, MA were detected in the two layers analyzed, and no important variations were observed either in MA abundance or activity. Salinity, sulfate, solids, organic carbon, and Eh were the environmental variables related to methanogenic community. A conceptual model is proposed to explain the dynamics of the MA.

Lateglacial and Holocene environmental changes in Portuguese coastal lagoons 1: the sedimentological and geochemical records of the Santo André coastal area

The Holocene ◽  
2003 ◽  
Vol 13 (3) ◽  
pp. 433-446 ◽  
Author(s):  
Maria da Conceição Freitas ◽  
César Andrade ◽  
Fernando Rocha ◽  
Colombo Tassinari ◽  
José Manuel Munhá ◽  
...  
Keyword(s):  
Coastal Area ◽  
Environmental Changes ◽  
Coastal Lagoons

High resolution climate and environmental changes of the northern Japan (East) Sea for the last 40kyr inferred from sedimentary geochemical and pollen data

2014 ◽  
Vol 414 ◽  
pp. 260-272 ◽  
Author(s):  
Sergey A. Gorbarenko ◽  
Seung-Il Nam ◽  
Yulia V. Rybiakova ◽  
Xuefa Shi ◽  
Yanguang Liu ◽  
...  
Keyword(s):  
High Resolution ◽  
Environmental Changes ◽  
East Sea ◽  
Pollen Data ◽  
Northern Japan

The REVEALS model, a new tool to estimate past regional plant abundance from pollen data in large lakes: validation in southern Sweden

2007 ◽  
Vol 23 (1) ◽  
pp. 21-42 ◽  
Author(s):  
Sofie Hellman ◽  
Marie-José Gaillard ◽  
Anna Broström ◽  
Shinya Sugita
Keyword(s):  
Southern Sweden ◽  
Pollen Data ◽  
Plant Abundance ◽  
Large Lakes ◽  
Reveals Model
Sign in / Sign up

Export Citation Format

Share Document