深化政治交接 切实担负起新时代民盟的责任和使命

政治交接在民主党派自身建设中居于核心地位,是我国多党合作事业根基永固的重要保障,也是加强中国特色社会主义参政党建设的必然要求。自“政治交接”这一历史课题诞生26年以来,民盟在继承和发展自身优良传统的基础上形成了以换届为契机、以主题教育活动为抓手的政治交接模式,不断深化和发展政治性、长期性、创新性、传承性、实践性等特色。展望未来,民盟将持续深入学习贯彻中共二十大精神,准确把握中国式现代化的中国特色和本质要求,努力建设高素质的中国特色社会主义参政党,用参政党建设实际成果展现政治交接的成效。

Seven million-year iron geochemistry record from a thick eolian red clay-loess sequence in Chinese Loess Plateau and the implications for paleomonsoon evolution

Recently, the Tertiary red clay sequence underlying Pleistocene loess has attracted much attention. The remarkable progress is the recognition that the Tertiary red clay sequence is also wind-blown in origin, thus providing a good opportunity to reconstruct long-term monsoon changes. In contrast to the loess deposits, the magnetic susceptibility and the pedogenic characteristics are almost independent of each other in the red clay, thus challenging the validity of the readily measurable magnetic susceptibility in describing the monsoon history recorded by the red clay. With the objective to address the long-term East Asia summer monsoon evolution, the free to total Fe2O3 ratios were calculated in a continuous eolian red clay-loess sequence at Lingtai, the Chinese Loess Plateau, which has a thickness of 305 m and a basal age of 7.0 Ma. The seven million-year Fe2O3 ratio record from the red clay-loess sequence indicates that (i) variations of the free to total Fe2O3 ratios of the loess can correlate

Stepwise advance of the Mu Us Desert since late Pliocene:Evidence from a red clay-loess record

Analyses of paleomagnetic polarity reversals, magnetic susceptibility and grain size on the red clay-loess sequence, about 280 m thick, at Jingbian show that this sequence contains most of the stratigraphic units recorded in the standard red clay-loess sections of the Loess Plateau over the past 3.5 Ma. Using sand particle percentage ( 】 63 μm%) of the eolian sequence as a proxy indicator of desert extent and aridity in the dust source regions, it is found that during the past 3.5 Ma, there are three important climatic events indicating the advance of the Mu Us Desert. The events occurred at about 2.6, 1.1 and 0.6 MaBP, respectively. The stepwise advance of the Mu Us Desert may be linked closely to increase in global ice volume and uplift of the Tibetan Plateau in the late Cenozoic.

Pedogenic carbonate isotope record of vegetational evolution since late Miocene in Loess Plateau

lsotopic analyses for paleovegetational evolution have been carried out on samples of the pedogenic carbonate nodules in the Red Clay-Loess sequence at Lingtai （35°N）, the Loess Plateau. Stable carbon isotopic composition indicates that （ ⅰ ） C4 plants might be present at least by7.0 Ma; （ ⅱ ） C4 plants expanded gradually between ～4.0 and ～3.2 Ma, and their biomass fraction was up to 50%; and （ ⅲ ） the biomass of C4 vegetation since ～2.0 Ma seems to have been decreased to the level （about 20%） before 4.0 Ma. C4 plant expansion at Lingtai cannot be fully understood with the 'global C4 expansion' model because it occurred much later up to 3.0 Ma than in Pakistan, which indicates that some changes in the regional climatic system may also contribute to C3/C4 shift except changes in atmospheric CO2 concentrations and temperature. The latitudinal zone for C3/C4 transition seems to move southwards slightly in East Asia, compared with the case in North America where 37°N is the ideal

The worm-shaped veins in the red earth of South China——Pedological evidence for root traces of past forest

Field observation of the macromorphology and analyses of micromorphology and geochemistry were conducted to the worm-shaped veins (WSVs) in the red earth of South China. The WSVs exhibit outward features of root traces and contain the traces of stele that can be used as the definite evidence of root traces. Surrounding the worm-shaped veins there are some micro-features pressed by past root growth. Geochemical analyses indicate that the white part in the WSV was depleted in Fe content. These lines of evidence suggest the WSVs in the red earth of South China are the root traces of past forest.

Changes in plant diversity on the Chinese Loess Plateau since the Last Glacial Maximum

Changes in biodiversity during periods of global warming are of broad public concern.To study the effect of the warming process on the ecosystem,we carried out pollen analyses on samples from seven selected sections at Qingyang,Ningxian,Yangling,Binxian,Baoji,Yanshi,and Lingbao on the Chinese Loess Plateau in order systematically to evaluate changes in plant diversity since the Last Glacial Maximum(LGM).The plant richness indices(Simpson’s diversity index and rarefaction analysis)indicated that the plant diversity of each section increased during the process of warming from the LGM to the Holocene Optimum,especially at Baoji and Lingbao.These results are consistent with many long-timescale geological records,which show that warming can increase biodiversity;therefore,the popular viewpoint that warming leads to biodiversity loss or species extinction needs to be re-examined.

Upper Jaramillo polarity transition and short geomagnetic event recorded in a loess section at Jingbian, northern China

Detailed rock-magnetic and paleomagnetic investigations have been carried out in a loess-paleosol sequence from the lower part ot unit S9 to the bottom of L11 at Jingbian (37.4° N, 108.8°E), which demonstrates that the Upper Jaramillo polarity reversal and a short geomagnetic event bounded within the Jaramillo normal subchron have been revealed. The duration of this short event was about 8.5 ka. The statistical analysis showed that the virtual geomagnet-

A climatic reversal at the last interglacial-last glacial transition recorded in the loess section at Zhaitang, Beijing

A weakly developed paleosol was identified at S1-L1 transition of the loess section of Zhaitang, Beijing. This paleosol may represent a climatic reversal which is associated with the strengthening in summer monsoon and correlated well with the climatic regression event documented in the paleoclimate records from Greenland ice, marine sediments and European pollen at the last interglacial-last glacial transition.

Chronology of environmental events over East Asia during the past 130 ka

In the transitional region between the Loess Plateau and deserts, 4 sections located respectively at Yuling, Hengshan, Dingbian and Huining of China are studied. The high-resolution paleoclimatic records obtained show that environmental events on varying time scales have happened over East Asia. These events are dated with the time scales established using the recently-developed approach of Automatic Orbital Tuning. This leads to the establishment of the chronology of the environmental events.

Forcing mechanisms for East-Asia monsoonal variations during the Late Pleistocene

Based on the climate records derived from loess deposits in north-central China, the characteristics of the East-Asia paleomonsoonal changes during the Late Pleistocene are summarized as follows: (ⅰ) The 0.1_Ma climate period is predominant in both summer and winter monsoonal changes over East Asia; (ⅱ) The East-Asia monsoonal variation is different from the Indian monsoon during the Late Pleistocene; (ⅲ) There is a ～5_ka time lag of the East-Asia monsoon changes relative to the theoretically calculated solar radiation changes; (ⅳ) There is a general trend toward increase in winter monsoon and decrease in summer monsoon in the last glaciation; (ⅴ) In the East-Asia monsoonal region, the amplitude of glacial-to-interglacial cycles shows a remarkable increase from south to north. To explain these characteristics, a conceptual model is developed and the forcing of global ice volume variations in the monsoonal history is emphasized.