An Attempt To Quantify The Relative Pollen Productivity Of Major Plant Types And Paleo-vegetation In The Late Holocene In North China

Pollen-based land cover reconstruction is of great significance for understanding the history of regional environmental responses to natural and human factors and for serving the future development of social ecosystems.The North China Plain,the second largest plain in China,is located in the temperate monsoon region of the middle latitude of the Northern Hemisphere.It belongs to the transitional zone of semi-humid and semiarid continental climate and oceanic climate,and is sensitive to global change.First of all,this study randomly selected in the typical vegetation zone in north China Taihang mountain 35 sample point,using ERV model of vegetation groups relevant source areas of pollen(RSAP)and pollen production estimates(RPPs)was calculated,and then combined with the other three temperate monsoon region pollen production data of mountain Landscape Reconstruction Algorithm using quantitative recovery in the region of north China plain Ningjinpo 3 ka BP-1 ka BP changes in vegetation.On this basis,the characteristics of vegetation succession in different historical periods and the influence of human activities and climate events on vegetation succession were analyzed and discussed.The main findings are as follows:(1)In the study area of Taihang Mountain,the vegetation types are mainly Pine,Betula and Quercus,shrub types of Hippophae and Rhododendron,and herb types of Artemisia,Asteraceae,Cyperaceae,Gramineae and Caryophyllaceae.The pollen assemblage also reflects the characteristics of vegetation in the study area.According to ERV model,the relevant source areas of pollen in Taihang Mountain is about 600 m.Taking Gramineae as reference species(RPP=1),the RPPS of dominant vegetation group in Taihang Mountain is Pinus(32.10±1.94)> Hippophae(18.38±1.27)>Caryophyllaceae(11.86±0.87)>Betula(4.97±0.08)>Quercus(2.69±0.08)>Rhododendron(2.48±0.27)>Artemisia(1.81±0.3)> Asteraceae(0.31±0.25)>Cyperaceae(0.04±0.03).(2)Based on the Landscape Reconstruction Algorithm,the vegetation cover of3 ka BP to 1ka BP in Late Holocene was reconstructed quantitatively:During 3.15 ka BP to 2.85 ka BP,the North China Plain was a forest-steppe landscape,and the steppe was widely distributed under the background of forest vegetation.From 2.85 ka BP to2.58 ka BP,there was a mixed coniferous and broad-leaved forest landscape dominated by coniferous trees.Although the agricultural level was somewhat developed compared with the original agriculture before,it did not reach the height of traditional agriculture,so the natural forest vegetation coverage was relatively high.From 2.58 ka BP to 2.15 ka BP,this period was warm and humid in the early stage,and cool in the late stage.It was a coniferous and broad-leaved mixed forest landscape,with the development of plain planting,wide distribution of farmland and increased number of companion plants.During 2.15 ka BP to 1.9ka BP,although there were several cold and warm fluctuations during the period,the climate conditions were generally warm and humid,the forest coverage decreased,and the plain area was cultivated,and the farmland landscape was dominated by grass.During 1.9ka BP to 1.3ka BP,the climate changed from warm and wet to cold and dry,and the cultivated land was abandoned,but the forest was restored to a certain extent,and it was a coniferous grassland landscape.(3)The effect of human activities on vegetation succession is mainly manifested in the reduction of forest area and the emergence of farmland(accompanied by the increase of human species).Since relatively stable agricultural activities appeared in the North China Plain 3,000 years ago,human activities may have had an impact on forest coverage.In the late Shang and early Zhou dynasties,the North China Plain was mostly covered with primitive natural vegetation.It was not until the Qin and Han Dynasties that natural forests fell sharply,and large areas of artificial vegetation replaced natural vegetation in the mountainous areas.The vegetation composition changed greatly,and the intensity of human farming activities and reclamation increased greatly.During the Wei,Jin and Southern and Northern Dynasties,due to years of war,farmland was abandoned and some shrubs and grasslands were restored,but there were still good forest vegetation in the hilly areas nearby.