Pollen Assemblage Of Farmlands In Central And Southern Hebei Province

There are cultivated vegetation, human disturbed vegetation and secondary vegetation in mountain areas, which may be similar to the initial status of plain areas in the early stage of human activities in history. The plain areas widely distributed with farmlands, are the areas with the greatest influence of human activities. Based on surface pollen analysis and vegetation investigations from mountain and plain areas, this study shows the pollen assemblages from artifical vegetations and human disturbed vegetations in central and southern Hebei Province, China, and tries to find the pollen types and pollen assemblages which can provide indications to the human activities, in order to give modern process evidences for studying the characteristics of regional vegetation and extracting human activity information in fossil pollen data.The study on 82 surface soil pollen samples from different types of cultivated vegetations in central and southern parts of Hebei Province indicates that the pollen assemblages from farmlands on the plain have not only their own plant types, but also the pollen components from the nearby mountains. Arboreal pollen percentages and concentrations (dominated by Pinus) of samples from the farmlands in the mountains are higher than those on the plains, and it reduces gradually with the increasing distance away from the mountains. Taking Pinus in Taihang Mountains for example, its content is 20%-30%, 10%-20%, 20%-30% and below 16% respectively for the samples from the area of 0-50, 50-100, 100-150 and more than 150 km away from the east of Taihang mountains. The increase of Pinus proportion in the central plains is probably related to the fohn effect. The spatial variation of AP from mountains to plains in Hebei Province may be similar to the historical change of forests clearance by human activities in early period. Shrubby pollen proportion is small both in mountains and in plains, but their major components are different. Elaeagnaceae, Corylus, Ostryopsis and Oleaceae are common in mountain farmlands, while there are relatively high contents of Rosaceae and Vitaceae in plains, Herb content in plains (about 60%) is 15% higher than that in mountains, among which the Cereals and Cruciferae pollen percentages are 5% and 2% higher respectively. Artemisia pollen percentage on the plains is lower than that in the mountains. Since the human activities are weaker in mountains compared with that on the plains, the general trend is that Chenopodiaceae pollen increases from mountains to plains gradually, reflecting the raising intensity of human activities. The fern spores of Selaginella sinensis in mountains are higher than that on the plains, which is about 7%. The fern spores of Selaginella sinensis are not prone to be spread by wind, indicating that those in the surface soil of the plains may be carried by currents from mountains during the deposition of the plains.The study on 48 Tauber trap pollen samples from different types of cultivated vegetations in central and southern parts of Hebei Province indicates that the tauber trap can better reflect the very local vegetation composition. The farmlands both in mountains and the plain show similar variation trend on pollen percentages in the same kind of agricultural units (corn fields, vegetable lands, orchards), that is the percentages of Arbors, Shrubs and Ferns in mountains are higher than those in the plain, herbs are lower than those in the plain, that rule is as same as the surface soil samples, but the Tauber traps can not reflect the diversity of region vegetation in mountains and the plain which is better summarized by the surface soil samples. The herbaceous pollen assemblages in different agricultural units are different to a certain degree in the same region: Cereal pollen contents in corn fields are much higher than that in vegetable lands and orchards; Cruciferae contents are higher in vegetable lands and orchards; the content of Rosaceae, Chenopodiaceae in orchards are higher than other agricultural units, that rule is as same as the surface soil samples. In addition, Leguminosae, Cucurbitaceae, Liliaceae, Solanaceae have relatively higher contents in the vegetable lands, while the average contents of these types are usually below 1% in surface soils, so the Tauber traps can better reflect the pollen assemblage in different kind of agricultural units. Pinus has over-representation in farmlands which are intensely influenced by human activity; the Pinus content in surface soil is higher than that in Tauber trap, indicating that the different kind of agricultural units have a smaller influence on the preservation of Pinus pollen. The contents of Cereals in the corn fields of Hebei Province are about 28% in the plain.