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Based on compilation of a large number of archaeological and palaeosol 14C-ages, the Summed Probability Method is used to reconstruct population history and climatic patterns on the Chinese Loess Plateau during the period 8.5–3.5 cal. ka BP. During this period, the population experienced two major expansion periods and several climatic fluctuations. The first population expansion began at around 7.8 cal. ka BP, and the second at around 5.8 cal. ka BP. During the first period, although already in combination with cultivation of broomcorn millet the population growth was supported mainly by hunting and gathering. With the switch from broomcorn millet to foxtail millet, plant cultivation became the major factor promoting a second population increase. In this paper, we demonstrate that, initially, suitable climate and agriculture both can facilitate population growth and climate events had a significant influence on demographic fluctuations. However, when reaching the threshold of land capacity, population became increasingly more sensitive towards climate fluctuations. [ABSTRACT FROM AUTHOR]

Land use is one of the key factors affecting soil erosion in the Loess Plateau of China. This paper examines soil erosion under different land uses and land-use combinations using 137Cs tracing in the Yangjuangou Catchment, a tributary of the Yan River in the Loess Plateau of Northern Shaanxi Province. The results show that the order of 137Cs activity in different land uses decreases sequentially from mature forest to grass to young forest to orchard to terrace crop, indicating that the mature forests had the lowest erosion rates while the terraced cropland produced the highest erosion amount. The majority of 137Cs is distributed in the top 0-10 cm of the soil layer. The 137Cs activity in mature forest and grass soil is significantly higher than in other land uses. Three land-use combinations on the hillslope were selected to study the relationship between land-use combination and soil erosion. The mixtures of 'grass (6 years old) + mature forest (25 years old) + grass (25 years old)' and 'grass (6 years old) + young forest (6 years old) + mature forest (25 years old) + grass (25 years old)' are better for soil erosion control, lowering soil erosion amount by 42% compared with a land-use combination of 'grass (6 years old) and shrub (6 years old)'. The results provide an important basis for optimizing land-use combinations to control soil erosion on slopes and may also result in important ecological benefits. [ABSTRACT FROM AUTHOR]

The Loess Plateau, China, has long been suffering from serious soil erosion. About 2000 years ago, larger areas were used for grain production and soil erosion was thus becoming severe with increase in human activity. Severe soil and water loss led to widespread land degradation. During the past decades, great efforts were made in vegetation restoration to reduce soil erosion. However, the efficiency of vegetation restoration was not as satisfactory as expected due to water shortage. China initiated another state-funded scheme, the ‘Grain-for-Green’ project in 1999, on the Loess Plateau to reduce soil erosion and improve land quality. However, the control of soil erosion effectively by land-use modification raised problems. In this paper, the lessons and experiences regarding soil and water conservation in the Loess Plateau in the past decades are analysed first. Urgent problems are then elaborated, such as the contradiction between land resource and human population, shortage of water both in amount and tempospatial distribution for vegetation growth, weak awareness of the problems of soil conservation by local officials, and poor public participation in soil and water conservation. Finally, suggestions regarding soil and water conservation in the Loess Plateau are given. In order to control soil erosion and improve vegetation, a scientific and detailed land-use plan for the Loess Plateau has to be made, in the first instance, and then planning for wise use of water resources should be undertaken to control mass movement effectively and to improve land productivity. Methods of improving public awareness of environmental conservation and public involvement in vegetation rehabilitation are also important. [ABSTRACT FROM AUTHOR]

This paper reviews recently published literature, most of which was published in Chinese, and searches for regional patterns of Holocene changes useful in depicting global patterns. The Holocene in the Xinjiang region can be divided into three stages: a warming and dry early stage (from 11 ∼ 10 to 8 ∼ 7 ka BP), a warm and wet middle stage (from 8 ∼ 7 to 4.5 ∼ 3 ka BP) and a fluctuating cool and dry late stage (since 4.5 ∼ 3 ka BP). The Holocene in the northern Tibetan Plateau can also be divided into three stages: a warming and wet stage (from 10.5 ∼ 10 to 5 ∼ 4 ka BP), followed by a variable drying and probably warm stage (5 ∼ 4 to 3 ka BP) and ending with a cool and dry stage (since 3 ka BP). In the Inner Mongolian Plateau, the early Holocene (from 10.5 ∼ 9.5 to 8 ∼ 7.5 ka BP) was warming and dry, and a warm and wet climate occurred from 7.5 to 3.5, during which the best time was 6.3–3.8 ka BP; the climate has been variably drying and probably cooling since 3.5 ka BP. In the northwestern part of the Loess Plateau, several Holocene palaeosols have been identified (10–9, 7.5–5, 4–3 and 2.7–2 ka BP) with the 7.5–5 ka BP palaeosol being most strongly expressed. The best-developed palaeosol-equivalent in major valleys is a swamp-wetland facies deposited between 8885 and 3805 14C yr BP under an extremely wet regime. The climate has fluctuated significantly at least three times around a dry and probably cool regime after the swamp-wetland facies-depositional period. Our summary shows that the Holocene Climatic Optimum occurred nearly contemporaneously (8–5 ka BP) at all sites in the Xinjiang region, in the Inner Mongolian Plateau and in the northwestern part of the Loess Plateau. A warming and wet early Holocene (10–8 ka BP) in the northern Tibetan Plateau is most likely related to high effective soil moisture resulting from snow and ice melting. We propose here that the middle Holocene Climatic Optimum (8–5 ka BP) in arid to semi-arid China was primarily a delayed response of the low latitude oceans to high latitude peak insolation (9–8 ka BP). [ABSTRACT FROM AUTHOR]