Extension of drylands in northern China around 250 kaBP linked with the uplift of the southeast margin of Tibetan Plateau

Study on two loess sections, one located at Wuwei near the Tengger Desert in northwestern China, another located near Ganzi at the southeast margin of the Tibetan Plateau in southwest China, reveals a coeval drying step occurred at ~250 kaBP. It is expressed by the increase in eolian grain-size at Wuwei, and by a drastic extension of C4 plants and a decrease of loess chemical weathering intensity at Ganzi. Examination of the available eolian data indicates that the event has also been clearly documented in the loess sections near the deserts in northern China, and in the eolian records from the North Pacific. On the contrary, the signal is rather weak for the central and southern Loess Plateau regions as well as for Central Asia, where the climates are influenced by the southeast Asian monsoon and the westerlies, respectively. Since the climate at Ganzi is under strong control of the southwest Asian monsoon, we interpret this drying ste p as a result of decreased influence of the southwest summer monsoon. This decre ase in monsoon moisture is attributable to the uplift of the Hengduan Mountains, the southeast margin of the Tibetan Plateau at～250 ka ago.     

蒙古高原植物的特有属及其基本特征

首次系统地列出了蒙古高原的１０个特有属沙芥属、连蕊芥属、绵刺属、四合木属、脓疮草属、芯芭属、百花蒿属、紊蒿属、革苞菊属、沙鞭属．这些属全部是单种属或双种属，分类上属于孤立、进化的类群；生态上都是旱生植物，而且沙生植物占优势，绝大多数是荒漠种或半荒漠种，其生活型草本植物占绝对优势；地理分布上集中分布于蒙古高原的阿拉善－鄂尔多斯地区，东阿拉善－西鄂尔多斯是其分布中心；起源上多数是东亚和古地中海植物区系的后裔．     

A mid－Holocene drought interval as evidenced by lake desiccation in the Alashan Plateau,Inner Mongolia,China

The mid-Holocene in China is traditionally thought to be a warm and humid period with a strong sum-mer monsoon, and is often termed the Holocene Climatic Optimum or Megathermal Period. Here we present lakegeomorphologic and lithologicai evidence from the Alashan Plateau, part of the Mongolian Plateau, that indicates stronglake desiccation during the mid-Holocene. High resolution pollen data from Zhuyeze Lake, at the present summermonsoon margin, is also presented. These data show that present lakes and wetlands in the Juyanze Lake basin west of the Badain Jaran desert, in the Zhuyeze Lake basin between the Badain Jaran and Tengger deserts, and in lakes in the eastern Tengger desert, dried or experienced low lake levelsin the mid-Holocene around 5000-7000 cal yr BP. Pollen data further indicate that the vegetation cover declined in both the local areas and in the Qilian Mountains, suggesting the climate was drier than that associated with the presentAsian summer monsoon. This mid-Holocene drought interval was present throughout a quite large region of the south In-ner Mongolian Plateau. The period was also probably colder,at least in the high Asian plateaus and mountains.     

Evidence of a humid mid-Holocene in the western part of Chinese Loess Plateau

Field works show that the wetland/swamp layers were distributed ubiquitously in the western part of the Chinese Loess Plateau. Universality of the wetland/swampy layer and the consistency of the age reveal that the layer was developed under the humid climatic condition. Dated between 9 and 3.8 kaBP, the wetland/swampy layer is full of aquatic mollusks and has the highest tree and shrub pollen,indicating a humid mid-Holocene. Variations of grain size suggest that winter monsoon weakened during 9-3.8 kaBP while climate change to humid and vegetation cover increased from 9 kaBP onward. After 5.9 kaBP, the humidity declined gradually. In 3.8 kaBP, summer monsoon sharply retreated, and the climate changed to dry.     

Natural vegetation of geological and historical periods in Loess Plateau

The study of natural vegetation of geological and historical periods in the Loess Plateau is an important scientific and practical issue for the development of northwestern China.However,interpretation of the natural vegetation before human reclamation is still controversial.The paper aims to analyze the potentical factors that cause the difference in knowledge of Holocene natural vegetation developing in different topographies of the Loess Plateau.The distribution of paleovegetation in this region shows significant difference among rocky mountains,valleys,and Yuan lands(the plain area),i.e.it does not follow the natural vegetation zonation,as that in eastern China does.The Yuan lands with thick loess accumulation were never covered by a vast of dense forests during the Holocene.Forests (or open forests)developed preferably in valleys in the southern part of the Plateau and rocky mountains on the Plateau during the warm period of the Holocene.Some of local vegetation outside of the Loess Plateau are more subjected to the control of geomorphology and ground water.     

蒙古高原岩黄芪属（Hedysarum）植物的分类学研究

确认了蒙古高原岩黄芪属植物１９种、３变种；合并了《内蒙古植物志）第二版中的ＨｅｄｙｓａｒｕｍｆｒｕｔｉｃｏｓｕｍＰａｌｌ．和Ｈ．ｍｏｎｇｏｌｉｃｕｍＴｕｒｃｚ．、Ｈ．ｆｒｕｔｉｃｏｓｕｍＰａｌｌ．ｖａｒ．ｌｉｇｎｏｓｕｍ（Ｔｒａｕｔｖ．）Ｋｉｔａｇ．和Ｈ．ｌｅａｖｅＭａｘｉｍ；发现了一新变种Ｈ．ｆｒｕｔｉｃｏｓｕｍＰａｌｌ．ｖａｒ．ｇｏｂｉｃｕｍＹ．Ｚ．Ｚｈａｏｅｔａｌ，否定了变种Ｈ．ｓｃｏｐａｒｉｕｍＦｉｓｃｈ．ｅｔＭｅｙ．ｖａｒ．ａｒｂｕｓｃｕｌａ（Ｍａｘｉｍ．）Ｙａｋｏｖｌ．和Ｈ．ｇｍｅｌｉｎｉｉＬｅｄｅｂ．ｖａｒ．ｌｉｎｅｉｆｏｒｍｅＨ．Ｃ．Ｆｕ的存在；订正了《内蒙古植物志》第二版中的Ｈ．ｐｏｌｙｂｏｔｒｙｓＨａｎｄ．－Ｍａｚｚ．为Ｈ．ｖｉｃｉｏｉｄｅｓＴｕｒｃｚ，并重新组合其毛果变种为Ｈ．ｖｉｃｉｏｉｄｅｓＴｕｒｃｚ．ｖａｒ．ａｌａｓｃｈａｎｉｃｕｍ（Ｂ．Ｆｅｄｔｓｃｈ．）Ｙ．Ｚ．Ｚｈａｏｅｔａｌ；比《内蒙古植物志》第二版增加了Ｈ．ｄａｈｕｒｉｃｕｍＴｕｒｃｚ．ｅｘＢ．Ｆｅｄｔｓｃｈ．和Ｈ．ｓｅｔｉｇｅｒｕｍＴｕｒｂｚ．两个种；更正了《内蒙古植物志》第二版中一些种的不确切分布．     

蒙古高原及其邻近地区的维管束植物区系分析初报(续)——Ⅱ.属的区系分析

内蒙古高原及其邻近地区有792属,其中蒙古与内蒙古共同的属为452属,相异的属为205属(只分布在蒙古的属有92属,在内蒙古的属有113属)。含有10个以上不同属的科是:菊科(28属),禾本科(18属),十字花科(17属),伞形科(12属),玄参科(11属),紫草科(10属),本区有10个大属,它们是:苔属(131种),黄芪属(94),棘豆属(90),蒿属(90),柳属(61)。风毛菊属(56),蓼厮(51),委陵菜属(46),马先蒿属(36),葱属(30),本区有3个特有属:四合木属,绵刺属和革苞菊属。