Investigation Of Spore-pollen Assemblages In Chongqing

Surface pollen assemblages and the relationships with vegetation are the foundation of rebuilding palaeo-vegetation with vegetation evolution succession, as well as recovering palaeo-environment and palaeo-climate. But the production of the spores and pollen is diverably, and the hold capacity (acid or alkali resistance), diffusibility and its mode of transmission also considerably vary, the representation of the plant is different, because the representation is effected by geographical position, topography and other factors, so the pollen assemblages is not really equivalent the vegetation. It is the key for palynologist that how to better understand the pollen characteristic and their relationship with modern vegetation, the promising trends are to link pollen analysis more closely with the topics of ecology and numberical analysis.We analysis fifty-five surface pollen samples of seven ecological vegetation (coniferous forest, coniferous and broad-leaved forest, evergreen broad-leaved forest, sub-alpine meadow community, shrubs and the cultivated land) in Jinyun Mountain Nature Reserve, Simian Mountain Nature Reserve and Jinfo Mountain Nature Reserve of Chongqing. In this study, we summarized the characteristics of surface pollen assemblages in different communities, the relationship between typical pollens and vegetation, the relationship between pollen percentage and concentration.(1) The results show that surface pollen assemblages match the corresponding plants. For example, the taxa of Theaceae, Magnoliaceae, Symplocaceae, Fagaceae, Euphorbiaceae, Rubiaceae are the common features in subtropical evergreen broadleaved forest, and Ericaceae, Myrsinaceae, Elaeocarpaceae are also the common features.(2) The surface pollen assemblages have obvious distinctions in the different ecological regions. In the coniferous forest communities, the conifer pollen percentages are more than 42%, and pinus and Taxodiaceae are the dominant in the pollen assemblages; in the mixed coniferous and broad-leaved communities, the conifer pollen percentages are more than 28%, broadleaf are more than 20%, but herbs are less than 15%; in the broad-leaved communities and shrubs communities, the conifer pollen percentages are more than 20%, herbs are less than 20%, the broadleaf and shrubs are labile. In the sub-alpine meadow communities, herbs are more than 37%, Gramineae and Artemisia are the dominant in the pollen assemblages; the herbs pollen percentage has sharply risen to 86.22% in the cultivated land, and Cruciferae pollen accounted for 80%. The spores and pollens concentration is lower in cultivated land, shows that farmland environment go again the presevation of pollen, and the pollen concentration would be reduced by the effect of human activities; the surface pollen assemblages are extremely unstable in bamboo forests, and the average percentage of Gramineae pollen is just 4.13%.(3) Cluster Analysis shows close relationship between the surface pollen assemblages and vegetation communities in Jinyun Mountain and Simian Mountain. The results of Clustering Analysis divided the samples into 6 groups in Jinfo Mountain, such as sub-apline meadow and cultivated land showing close relationships between the surface pollen assemblages and vegetation communities. The other communities such as coniferous forest, mixed coniferous and broad-leaved forest, broad-leaved forest, shrubs and bamboo forest can not be divided clearly, the reason is that evergreen broad-leaved forest and Pinus massoiana forest almost distribute the whole Jinfo Mountain, and the geography, the human activity and other complex factors(such as pollen production, dispersal and deposition)will influence the pollen assemblage, so the results are not as good as the sample communities.(4) The study of pollen presentation and indication to vegetation shows that the taxa of Pinus, Betula, Alnus are over-representative; Taxodiaceae is very representative, and it can indicate plant community very well; Most of the subtropical species are under-representative; Ericaceae, Gramineae are under-representative; The production and kinds of fern spores are rich, which with typical subtropical characteristics, and show that the climate is good for fern plants growing in Chongqing.(5) The trend of pollen concentration and pollen percentage is similar in seven ecological vegetation, show that the surface pollen assemblages are relatively stable in Chongqing. The quantity of pollen concentration is volative in sample, the concentration of pollen changes marked of the dominant species.