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Baishanzu area in Qingyuan, Zhejiang Province, which is famous for the discovery of Abies beshanzuensis, has the most typical mid-subtropical evergreen broad-leaved forest and complete vertical zones of mountain ecosystems in China, and this provides good natural conditions for paleoclimatic reconstruction using surface soil and airborne pollen data. Based on the pollen spectra of nine surface soil pollen samples collected at 300-1,700 m altitude, the relationship between vegetation and surface soil pollen in this area was preliminarily studied. The results show that surface soil pollen in this area can be divided into three assemblage zones from top to bottom according to altitude and ratios of coniferous pollen/broad-leaved pollen and arboreal pollen/non-arboreal pollen, which correspond to the evergreen deciduous broad-leaved mixed forest and temperate coniferous forest, evergreen broad-leaved forest and warm coniferous forest, secondary forest, and farmland (caused by human interference) zones. The surface pollen assemblages were dominated by the evergreen coniferous tree species Pinus, with an average pollen content of 67.5%. The pollen of Castanopsis (6.2%), Quercus (3.4%), Betula (1.4%), and Corylus (1.4%) is common. In contrast, Cyclobalanopsis, Liquidambar, Symplocos, Tsuga, Oleaceae, and Ericaceae had lower contents. Herbaceous plants are dominated by Poaceae (11.2%), including Artemisia, Chenopodiaceae, Apiaceae, Asteraceae, etc. The spore content of fern vegetation was high, mainly Hicriopteris (38.2%) and Polypodiaceae (7.4%). Pinus pollen appeared in all samples, with the highest average content. With increasing altitude, the mean percentage gradually increased from 54.8% to 77.3%, and it is an overly represented pollen with a low sedimentation rate that is easily preserved and transported to the area. Abies pollen is only observed in the samples under the A. beshanzuensis tree at an altitude of 1,700 m. Its percentage is lower than 1%, which may be related to low pollen yield and the relatively narrow distribution range of A. beshanzuensis in this area. In addition, the pollen diversity analysis results based on Simpson's index show that human interference factors prevent the surface soil pollen at lower altitudes in this area from reflecting the regional zonal vegetation. With decreasing altitude, the deciduous component of arboreal pollen in the pollen assemblage increased from 13.2% in Zone I to 40.9% in Zone III. Zone III shows a coniferous and broad-leaved mixed forest zone caused by human factors. The content of the evergreen component in zone I is high, which is related to the high humidity at higher altitudes. This study selects Baishanzu National Park to study the surface soil pollen and preliminarily discusses the characteristics of the surface soil pollen assemblage and its relationship with vegetation, which provide research materials and the basis for Quaternary paleovegetation and paleoclimate reconstructions in the Baishanzu area, Qingyuan County, China. However, due to a lack of surface soil samples and modern vegetation investigation data, the reliability of the research results is affected. In future research, sampling and density quadrat surveys of surface sampling sites will be increased to cover as many vegetation zones as possible.

ABSTRACT To quantitatively describe the Late Holocene palaeoclimatic history of the southern slopes of the Tianshan Mountains in Xinjiang, China, we collected 74 surface pollen samples (from −154 to 4285 m), together with 81 fossil samples from Swan Lake. Based on modern pollen assemblage and redundancy analysis ( RDA) of surface pollen data, five pollen zones were divided (alpine cushion vegetation, alpine meadow, subalpine meadow steppe, montane desert, and typical desert zones). Modern pollen-climate transfer functions were developed to quantitatively reconstruct palaeoclimate of the area using the weighted averaging partial least squares regression method. Reconstructed mean annual precipitation and mean annual temperature results suggest that a dry/warm or humid/cold climate pattern prevailed over the past 4200 aBP. Notably, three cold and humid stages were detected at 4200-4000 cal. aBP, 3700-2000 cal. aBP, and 1170-930 cal. aBP. Moreover, a humid 'Medieval Warm Period' ( MWP) occurred not only on the northern slopes but also on the southern slopes of the Tianshan Mountains. However, based on palaeo-environmental records and on archaeological documents, it would appear that a dry MWP occurred in southern parts of south Xinjiang, with this being different from the MWP on the Tianshan Mountains. Interactions between monsoon and the westerly airflows might account for this difference. The data will improve understanding of past atmospheric circulation systems in the different parts of Xinjiang and will help to predict the future climate in the world. [ABSTRACT FROM AUTHOR]

Climate change and human activities interact to affect the vegetation landscape. We examined the interaction of these drivers using multiproxy records, including data on pollen, charcoal, phytoliths, total nitrogen, total organic carbon, and loss-on-ignition, from a 268-cm sediment profile in Xinjiang, China. By combining these data with information gained from 214 samples of surface pollen assemblages in north Xinjiang, we were able to reconstruct the late Holocene climate using a weighted averaging partial least squares regression model. Our results suggested that the typical desert vegetation of the region changed to Artemisia desert at 2400 cal. a BP, and returned to desert after 900 cal. a BP. A warm–dry and cold–humid climate pattern existed during the past 4000 years. The climate was characterized by obvious fluctuation prior to 2400 cal. a BP, after which it became wetter and colder with little fluctuation. The temperature maximum in our reconstruction occurred around 700 cal. a BP. The macrocharcoal particles reached their highest levels at c. 3500 cal. a BP, and again at 700 cal. a BP, suggesting increases in human activities at these times. An increased amount of anthropogenic plant pollen also appeared in sediment over the past 50 years. Large numbers of Thelypteris spores and Phragmites phytoliths in the surface pollen samples from modern desert vegetation also reflect recent human activities. Therefore, our data provide evidence that both climate and human activities are important drivers of changes in regional vegetation. [ABSTRACT FROM PUBLISHER]

As a good indicator of Holocene climate, the fluctuation of alpine timberline is a synthetical result of impacts of many environmental factors during geological and historical periods and modern times. As the dominant tree species of mountainous conifer forests on the northern slope of Tianshan Mountains in Xinjiang, the distribution of Picea schrenkiana and its population size are sensitive to climatic change. The typical natural profile of Huashuwozi and the nearby Xiaoxigou archaeological profile, located in Quanzijie Township, Jimusaer County in Xinjiang, were chosen to analyze and compare the relative high-resolution pollen records, and to measure 14C dating and SEM (scanning electron microscope) microstructure for charcoal fragments contained in Xiaoxigou profile's cultural layers. The results show that in these two profiles, the high percentages of Picea (more than 20% and 35%, respectively) appeared in the stratum of the same period (2000-1300 a BP), which corresponds to the charcoal fragment's age of Picea schrenkiana contained in Xiaoxigou cultural layers. These results convincingly revealed that during the period of 2000-1300 a BP, the timberline for Picea schrenkiana on the northern slope of Tianshan Mountains in Xinjiang declined by about 330m compared with the present. [ABSTRACT FROM AUTHOR]