Relationships Between Surface Pollen And Modern Vegetation At Quadrat Scale

Establishing a robust relationship between modern vegetation and surface pollen is the basis and key to quantitatively reconstruct paleovegetation and paleoclimate based on pollen records.So far,the record of plant community plots has less been involved in the statistical analysis of modern vegetation and surface pollen,which limits the quantitative expression of their real relationship.Therefore,this study collected 57 surface pollen samples from the Northeast China Transect(NECT)and the Beishan Mountain of Jinhua.Based on detailed plant community survey records and surface pollen data from the plots,modern ecological and traditional pollen quantitative analyses were applied to compare and explore the quantitative relationship between modern vegetation and surface pollen in different vegetation types,Results are as follows.1.The characteristics of surface pollen assemblages in the NECT show that the surface pollen assemblages of different vegetation types are significantly different.The average pollen content of tree and shrub in the NECT forest is 77.8%.The woody plants are mainly Pinus,Picea,Abies and Betula.In meadow steppe,typical steppe and desert steppe,the surface pollen assemblages is dominated by herb pollen with an average percentage content of 84.6%.The terrestrial herb pollen is mainly Artemisia and Chenopodiaceae.The Bray-Curtis dissimilarities show that there are differences in compositions and quantities between surface pollen and modern vegetation in the transect.All families and genera,dominant and common families and genera,and lesscommon and rare families and genera of forests,meadow steppe,typical steppe,and desert steppe are primarily manifested as pollen types that appear in surface samples but do not exist in modern vegetation.In terms of quantities,most of the vegetation in the study area shows that the dominant and common families and genera are low in surface pollen assemblages.It also shows relative high pollen content of less common and rare families and genera at the western end of the forest and typical steppe,and in the desert steppe and meadow steppe,but relative low in the middle and eastern part of the typical steppe.The deviation of Bray-Curtis dissimilarities in this region are mainly attributed to the differences in pollen production and pollen dispersal2.The surface pollen in the Beishan Mountain of Jinhua basically reflects the local vegetation status.The average percentage of pollen content in trees and shrubs is95.7%.The pollen of woody plants are mainly Pinus,Quercus(deciduous),Taxodiaceae,Cryptoperia,Castanea,Lithocarpus/Castanopsis,Platycarya,and Schima.The herbs pollen mainly consist of Artemisia and Asteraceae,and their average percentage is 4.3%.Fern spores are dominated by Hicriopteris/Dicranopteris and Polypodiaceae.They are higher in the surface pollen from the mountain and the average percentage reaches to 21.9%.The Bray-Curtis dissimilarities show that there is a difference in compositions and quantities between the surface pollen and modern vegetation in this region,where six different vegetation types appear as coniferous forest,evergreen deciduous coniferous and broad-leaved mixed forest,evergreen deciduous broad-leaved mixed forest,evergreen deciduous broad-leaved mixed forest,evergreen broad-leaved forest and shrubs.For less common and rare families,the results indicate that the pollen types appearing in surface samples do not exist in modern vegetation.While,the dissimilarity are all positive or zero for the dominant and common families,especially in mixed evergreen coniferous and broad leaves forests,evergreen coniferous and broad-leaved mixed forests.But all the important families and genera in evergreen broad-leaved forests also exist in the surface pollen spectra.Quantitatively,all the dominant and common families and genera corresponding the high-value in modern vegetation generally have low percentages insurface pollen spectra,whiles less common and rare families and genera are with variable results.Pollen production,pollen dispersal,and disturbance of human activities are the main causes of deviations in composition and quantity disparity coefficients.The main pollen concentration and percentage content in the study area show similar trends to a certain extent,and the pollen concentration is significantly different among different vegetation types.3.The principal component analysis(PCA)results of surface pollen manifest that the vegetation in the NECT is mainly impacted by precipitation,followed by human activities.In Beishan Mountain of Jinhua,the change of altitude contributes most to the variations of vegetation.But the altitude has less impact on the distribution of pollen in soils.In addition,the vegetation is subject to human activities.4.Pollen composition are quantitatively consistent with modern vegetation in the NECT,according to the two indicators of R value and Bray-Curtis dissimilarity.However,Bray-Curtis dissimilarities lead to an inconformity in both composition and quantitative relationship between surface pollen and modern vegetation in the Beishan Mountain of Jinhua.And there is a big difference between Bray-Curtis dissimilarities and the R-values.The Bray-Curtis dissimilarity cannot establish the relationship for different families and genera in this region,where human activities have been impacting modern vegetation for a long time.The Bray-Curtis dissimilarity,however,can describe the quantitative relationship between modern vegetation and pollen in terms of species compositions,from multi levels and perspectives.Although with certain calculation deviations,it can be one of quantitative description of vegetation-pollen relationship,which worth to be further studied in different regions and different vegetation types in the future.