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The focus of this paper is on the reconstruction of the mid-Holocene climatic changes based on the pollen records contained in a 6.2 m thick section in the southern part of the Tengger Desert, northwestern China. To understand the modern analogues of the mid-Holocene changes, modern pollen spectra across different vegetation zones from the Qilian Mountains to the lowland Tengger Desert were studied first. Four pollen combinations were identified, corresponding to four different modern ecological environments: (1) a Picea-Artemisia combination in a spruce forest and its vicinity; (2) an Artemisia-Chenopodiaceae-Gramineae-Salix combination in a mixture belt of montane grassland and poplar woodland; (3) a Chenopodiaceae-Artemisia-Nitraria combination in a desert steppe belt; and (4) an Elaeagnus-Artemisia-Chenopodiaceae-Nitraria combination in a desert riparian forest. Our study also shows that a relatively low percentage of Picea pollen (30–10%) seems to be associated with water transportation (alluvial deposits) and a very low percentage of Picea pollen (10–5%) appears to be related to long-distance air transportation. With references to the modern relationships between pollen assemblages and associated bioclimates, the pollen sequence covering the period between 8500 and 3000 cal. BP was used to infer the climatic change history. The results show that a warmer and drier climate dominated between 8500 and 7950 cal. BP. Subsequent decreases in Artemisia and warm desert forbs/shrubs taxa and contemporaneous fluctuating increases in montane coniferous and aquatics elements from 7950 to 7400 cal. BP reflect a fluctuating increase in humidity and/or a fluctuating decrease in temperature. The following period from 7400 to 5650 cal. BP was generally warm with the Holocene Climate Optimum occurring between 7400 and 6500 cal. BP. A remarkably cool spell followed between 6500 and 6300 cal. BP that was then succeeded by a warmer and more humid period between 6300 and 5650 cal. BP. The period between 5650 and 4450 cal. BP was characterized by drastic oscillations in climatic conditions with three humid and probably cold spells intervened by three relatively dry and warm spells. The period between 4450 and 3500 cal. BP was cold and humid, followed by a wet spell as indicated by a very high percentage of Typha pollen. [ABSTRACT FROM AUTHOR]

Revisiting the classical Gradmann’s ‘steppe theory’ for central Europe, we examine whether the early Holocene steppe habitats survived the critical period of maximum Holocene afforestation: the mid-Holocene bottleneck. Despite the undisputable fact that afforestation was a dominant ecological factor in this period, our parallel analyses of pollen and molluscs from sedimentary sequences discovered in the dry lowland area of northern Bohemia, Czech Republic (Zahájí and Suchý potok sites, lower Ohře area) provide strong evidence for uninterrupted local occurrence of steppe grasslands throughout the Holocene. At the onset of the Neolithic agriculture, this area was covered by forest-steppe. Analogously to the present forest-steppe landscapes of eastern Europe and south-western Siberia, dry areas of northern Bohemia were dominated by open-canopy pine–birch forests that enabled continuous survival of many light-demanding plant species from the late Glacial and early Holocene to the Neolithic. Later on, anthropogenic deforestation and livestock grazing created a semi-natural steppe. Our data suggest that this secondary steppe can be viewed as a direct continuation of the late Pleistocene and early Holocene natural steppe rather than a purely cultural steppe developed only after deforestation of a continuously forested mid-Holocene landscape by humans. At the same time, we provide evidence supporting Gradmann’s ‘steppe theory’, assuming that in central Europe, Neolithic farming started in those areas that were not completely forested but contained remnants of natural steppes. This finding has important implications for the interpretation of present biodiversity patterns in central Europe. [ABSTRACT FROM PUBLISHER]

The relation between climate change and historical rhythms has long been discussed; however, this type of study still faces the lack of high-resolution data of long-term socio-economic processes. In this study, we collected 1101 items of direct and proffered evidence from 24 Chinese fiscal and economic history books written by leading contemporary scholars. By analysing the semantics of words, we reconstructed a 2130-year-long fiscal sequence with decadal resolution to express the phase transition of fiscal soundness for approximately 21 dynasties in China. Our reconstruction shows four relatively sufficient stages and three relatively deficient stages, with several secondary stages lasting 60 or 160 years on average within each large stage, from 220 bc to ad 1910. Then, the fiscal association with climate change was analysed. The results show that the fiscal crisis was more likely to occur in cold-dry climatic scenarios. Both temperature and precipitation displayed more significant effects on the fiscal fluctuation within the long term, particularly for temperature. In short, fiscal decline had a 10-year lag in response to decreasing precipitation, whereas influence of decreasing temperature on the fiscal balance might be through amplifying already deteriorating fiscal conditions. Regional differences existed in the influence of precipitation on the fiscal balance. The precipitation in the Northern China Plain and in the Jiang-Huai area had more significant effects on the fluctuation of the dynastic fiscal balance than on that in the Jiang-Nan area. In particular, the dynastic finance was more sensitive to the change in the precipitation in the Northern China Plain because of its special geographical, economic and social backgrounds. [ABSTRACT FROM AUTHOR]

We reconstructed a multiproxy record of the Holocene climate changes from a 9.53 m core from Bosten Lake in the southern Xinjiang of northwestern China based on a chronology supported by nine AMS 14C dates in the hope that the previous reconstructions can be improved. Our data exhibited three timescales of variation in the water salinity of the lake. First, the upward-increasing parallel trends of major salinity proxies suggest that the salinity has been gradually increasing in the past ∼8000 years. This constant increase in the salinity is most likely to have resulted from the shrinking of glacial cover in the central Tianshan Mountains where the inflowing river (i.e. Kaidu River) originated. Second, the C/S ratio and carbonate-based salinity proxies suggest that the lake was formed around ∼8060 cal. yr BP and reached its maximum depth around ∼7250 cal yr BP. The lake level then declined to the mid- and late-Holocene average level around ∼6370 cal. yr BP and has varied drastically around a relatively constant mean during the past ∼6370 years. Third, the past ∼8060 yr history of the Bosten Lake can be divided into five salinity stages. That is, three high salinity intervals are separated by two low salinity intervals. The two low salinity stages occurred between ∼6370 and ∼5170 cal. yr BP and between ∼3000 and ∼2170 cal. yr BP. Each one of the three high salinity stages can be further divided into less saline and more saline substages. Specifically, less saline time intervals are: substage 2-1 (∼8060-∼7250 cal. yr BP), substage 4-2 (∼4370-∼3830 cal. yr BP) and substage 6-2 (∼1250-∼0 cal. yr BP). Also, saltier time intervals are: substage 2-2 (∼7250-∼6370 cal. yr BP), substage 4-1 (∼5170-∼4370 cal. yr BP), substage 4-3 (∼3830-∼3000 cal. yr BP) and substage 6-1 (∼2170-∼1250 cal. yr BP). It should be stressed that the phase relationships between the carbonate-based salinity proxy and diatom-based temperature proxy suggest that the salinity was mainly controlled by temperature. Finally, the comparison between the Bosten Lake salinity record and the high northern latitudinal climate pattern suggests that the lower salinity and cooler periods in Bosten Lake area correspond with abrupt climatic events (i.e. cooling events) in the high northern latitudes. [ABSTRACT FROM AUTHOR]

Information on changes in land-surface features on the Tibetan Plateau (TP) during the Holocene may help our understanding of the forcing of monsoonal circulation. We analyse vegetation changes during the last 9000 years from pollen records of four lakes (Hurleg Lake in the Qaidam Basin; Qinghai Lake on the northeastern TP; Zigetang Lake on the central TP and Koucha Lake on the eastern TP) which represent different regions and vegetation types on the Plateau today. A set of modern pollen assemblages from 111 lake sediment samples originating from different vegetation types is used for the interpretation of the Holocene pollen records. Four types of numerical analyses are used to infer different aspects of pollen-stratigraphical and inferred vegetation changes: biome reconstruction; ordination (to infer palynological compositional turnover); rate-ofassemblage- change analysis, and a pollen-LAI (leaf area index) transfer function. Our results show strong regional differences in inferred vegetation change in terms of timing, strength and the nature of change. The greatest changes in compositional turnover and LAI are found in the Qinghai Lake record, indicating that forests were replaced by steppe vegetation in a step-wise fashion since the mid Holocene. Alpine steppe vegetation on the central and eastern TP was relatively stable throughout the Holocene, only showing a gradual replacement of temperate steppe by high-alpine meadows. The Qaidam Basin was dominated by temperate desert throughout the Holocene. The documented palynological and inferred vegetation changes can be most parsimoniously explained by climate change, although human impacts cannot be excluded as a contributing factor. Comparison of our findings with sensitivity analyses of numerical climate simulations suggests that longterm vegetation change may have had only a weak influence on regional climate change on the Tibetan Plateau. [ABSTRACT FROM AUTHOR]

Optical dating was used to obtain a chronology for a loess-palaeosol sequence in the Guanzhong Basin on the Loess Plateau in China. The sedimentary sequence recorded two dry episodes (3.7~2.4 ka and 1.2~0.8 ka ago) in the Holocene as shown by the presence of two layers of loess within the Holocene deposits. These two arid events are consistent with records of global climate change in the Holocene and also coincident with major historic events in China. This finding suggests that loess-paleosol sequences in China can record global climate changes and implies that rapid climate change affected the progress of human civilization. In addition, changes in the sedimentation rate through the section suggest that agricultural expansion may have accelerated the rate of dust accumulation. [ABSTRACT FROM AUTHOR]

Middle- to late-Holocene palaeoclimate change has been reconstructed at high resolution by the analysis of the carbon and oxygen isotopes from a thermal ionization mass spectrometric (TIMS) U / Th dated stalagmite from Xiangshui Cave, near Guilin, Guangxi Province, China. The carbon and oxygen isotopic records from the stalagmite suggest that changes in the Asian monsoon since the middle Holocene (6000 BP) can be divided into two periods: (1) an interval from 6000 to 3800 BP when a strong East Asian summer monsoon gradually weakened and climate was relatively warm and humid; (2) a cool period from 3800 to 373 BP when the East Asian summer monsoon was relatively weak and the winter monsoon was probably relatively strong. This cooler interval was interspersed with a number of short warm periods. This interpretation is largely based upon the general increase in δ18O values of the stalagmite between 6000 and 3800 BP and shifts in δ18O about a relatively heavy mean value between 3800 and 373 BP. The 6000 to 3800 BP trend is probably associated with decrease in precipitation and temperature subsequent to the mid-Holocene climatic optimum. [ABSTRACT FROM AUTHOR]