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Hebei Normal University (2017)

Modern Pollen and Their Relationships with Climate and Vegetation in Northern Shanxi

王俊婷;

Titre : Modern Pollen and Their Relationships with Climate and Vegetation in Northern Shanxi

Auteur : 王俊婷;

Grade : Master’s Theses 2017

Université : Hebei Normal University

Résumé
Modern pollen process research is an important part of analyzing climate,vegetation change,reconstructing paleoclimate,and ancient vegetation.The study of airborne pollen and surface soil pollen are significant parts of it.Hunyuan and Guancen Mountain in north of Shanxi Province are chosen as the objects for the study of airborne pollen and surface soil pollen.The study of airborne pollen in Hunyuan County in the eastern edge of the Loess Plateau tries to reveal the characteristics of airborne pollen assemblages and their relationships with climatic factors based on the pollen trap data collecting from 2007 to 2009 at the eastern Loess Plateau in Hunyuan county,Shanxi Province.The airborne pollen assemblages show that the herbaceoustaxa dominate the pollen assemblages with their percentages higher than 80.9%,which is consistent with the steppe vegetation in this study area.The pollen influx of trees and Artemisia and Chenopodiaceae in 2007 2008 are higher than that in the spring of 2008 2009,but lower than that in other seasons of 2008,especially for Artemisia.The peak time of pollen influx is similar for the two study years,while the herbaceous pollen influxes coming from fall and winter of 2008 2009 are obviously higher than that in 2007 2008.The RDA analysis between pollen influxes and climate factors show that the pollen assemblages at Hunyuan are mainly influenced by the average wind speed and maximum wind speed,then by the relative humidity,temperature and precipitation.In addition,the wind direction also has some effects,and the influxes of different pollen taxa are influenced by different climatic factors.The arboreal plant influxes are mainly influenced by the average wind speed,but the herbaceous pollen influxes have more significant correlation with the wind direction.Because the wind in the study area usually comes from north to northwest,which will bring more steppe pollen taxa,such as Artemisia,Chenopodiaceae,Asteraceae,Poaceae etc.The RDA analysis of pollen influxes and climatic factors in different seasons show that temperature is the major climate factor to the pollen influxes in spring,while the wind direction of maximum wind speed become more important in summer,and in turn,only wind speed show significant correlation with pollen influxes in winter and autumn.Modelling efforts to quantitatively reconstruct vegetation from pollen have never been attempted along the forest-steppe border in our country,however such studies are important in interpreting fossil pollen assemblages of vegetation change along this ecotone.In this paper,relative pollen productivity(RPP)and relevant source area of pollen(RSAP)as two important parameters in quantitative vegetation reconstruction using LRA(Landscape Reconstruction Algorithm approach)model,are estimated from the forest–steppe ecotone north of Shanxi,where pollen sampling and vegetation survey was performed at 18 random sample sites.The pollen analysis results show that Artemisia,Asteraceae,Poaceae,Pinus,Picea,Quercus,Betula and Hippophae dominate the pollen assemblages with more than 80% proportion.ERV(Extended R-value)analysis found that the RSAP is about 600 m and that around 50% of the pollen in each sample comes from beyond this distance.RPPPoaceae is estimated as more than 10 for Pinus and Hippophae and around 5 for Picea and Betula.Estimates for Artemisia(3-4)are substantially lower than those reported from other studies in the steppe biome,and for Quercus(0.5)are substantially lower than those from the forest biome in north-east of our country and Europe.Four additional samples were then used to test the effectiveness of two methods for reconstruction of vegetation proportion from pollen assemblages,the Landscape Reconstruction Algorithm(LRA).Ordination showed that that both methods can give generally reasonable results,but there is still some discrepancy between the two methods.

Mots clés : Airborne Pollen; Pollen Influxes; RDA; Relative Pollen Productivities; Relevant Source Area;

Présentation (CNKI)

Page publiée le 22 février 2018