Erosion response to anthropogenic activity and climatic changes during the Holocene: case studies in northwestern China and southern Norway

Soil erosion assessment and prediction play critical roles in addressing problems associated with erosion control or soil conservation. The past dynamics of soil erosion can provide valuable information for us to understand the relations of soil erosion to environmental change and anthropogenic activity. The present paper has compared Holocene climatic changes in northwestern China with those in southern Norway, and investigated the past dynamics of erosion activity during the Holocene. Modern soil erosion on the Loess Plateau is a combination of the intensive natural erosion and human-induced erosion, the latter being four times greater than the former. Because of global warming and increasing human activities, climate on the Loess Plateau is becoming dryer and more unstable, causing an enhanced erosion problem and water scarcity. In the arctic-alpine region of southern Norway, however, the global warming and regional wetting caused expansion of the largest European ice cap. This has accentuated the erosion in that region, with a higher frequency of avalanches and debris flows.     

An early Holocene erosion phase on the loess tablelands in the southern Loess Plateau of China

A Holocene loess profile to the west of Xi'an China was studied multi-disciplinarily to investigate the relationships between soil erosion and monsoonal climatic change. The proxy data obtained from this aeolian loess and palaeosol sequence indicate large-scale variations of climate in the southern Loess Plateau since the last glaciation. A rainwash bed, indicative of a wetter climate, excessive runoff and erosion on the loess tablelands, was identified relating to the early Holocene before the onset of the “climatic optimum”. This is synchronous with the early Holocene physiographic erosional stage identified in the valleys in North China. It means that severe erosion took place when the region was undergoing climatic amelioration during the early Holocene. The evidence presented in this paper shows that the erosion occurred as a regional response to a monsoonal climatic shift in the southern Loess Plateau. During the last glaciation, prior to the erosion phase, the land surface on the tablelands had been largely stable except for the rapid accumulation of aeolian dust and the resultant increase in its elevation. Relatively slow dust accumulation and intensive bio-pedogenesis responding to the Holocene “climatic optimum” followed the erosion phase. The loess tablelands were most vulnerable to erosion during the large-scale monsoonal climatic shift from dry-cold glacial to humid-warm post-glacial conditions in the southern Loess Plateau.     

泾河上游黄土高原全新世成壤环境演变与人类活动影响

通过对黄土高原腹地甘肃合水MJY-A全新世土壤剖面磁化率、粒度、全铁、TOC、TC、CaCO3等气候代用指标的测定分析。结果表明：在全新世早期,黄土高原中部地区气候虽比较温和干燥,风尘堆积速率降低,土壤发育表现为边沉积边成壤的自然过程;到了全新世中期,气候较为温暖湿润,地表植被发育,生物风化成壤作用强烈,土壤发育依旧表现为自然的成壤过程,形成深厚的古土壤-黑垆土(S0);到了全新世晚期,气候开始恶化,干旱少雨,植被急剧退化,沙尘暴频繁发生,形成的现代黄土层(L0)覆盖了土壤(S0)使之成为埋藏古土壤,土壤发育深受人类活动的影响。现代黄土高原土地资源的退化,并不全是由自然要素本身固有的规律所造成的,而是在自然要素本身变化的背景上叠加了人类活动影响的结果。     

Soil erosion and its response to the changes of precipitation and vegetation cover on the Loess Plateau

Soil erosion is a major threat to our terrestrial ecosystems and an important global environmental problem. The Loess Plateau in China is one of the regions that suffered more severe soil erosion and undergoing climate warming and drying in the past decades. The vegetation restoration named Grain-to-Green Program has now been operating for more than 10 years. It is necessary to assess the variation of soil erosion and the response of precipita- tion and vegetation restoration to soil erosion on the Loess Plateau. In the study, the Revised Universal Soil Loss Equation （RUSLE） was applied to evaluate annual soil loss caused by water erosion. The results showed as follows. The soil erosion on the Loess Plateau between 2000 and 2010 averaged for 15.2 t hm-2 a 1 and was characterized as light for the value less than 25 t hm-2 a-1. The severe soil erosion higher than 25 t hm-2 a-~ was mainly distributed in the gully and hilly regions in the central, southwestern, and some scattered areas of earth-rocky mountainous areas on the Loess Plateau. The soil erosion on the Loess Plateau showed a deceasing trend in recent decade and reduced more at rates more than 1 t hm 2 a 1 in the areas suffering severe soil loss. Benefited from the improved vegetation cover and ecological construction, the soil erosion on the Loess Plateau was significantly declined, es- pecially in the east of Yulin, most parts of Yah＇an prefectures in Shaanxi Province, and the west of Luliang and Linfen prefectures in Shanxi Province in the hilly and gully regions. The variation of vegetation cover responding to soil erosion in these areas showed the relatively higher contribution than the precipitation. However, most areas in Qingyang and Dingxi pre- fectures in Gansu Province and Guyuan in Ningxia Hui Autonomous Region were predomi- nantly related to precipitation.     

晚更新世以来的季风变化对晋陕蒙接壤区现代侵蚀的影响

黄土高原晚更新世末次冰期时期,冬季风强盛,马兰黄土堆积;全新世以来的间冰期时期,夏季风强盛,降水较丰,侵蚀强烈。晚更新世以来的中国东部海岸线40°N 一带变化最大,同纬度晋陕蒙接壤区是黄土高原季风气候变化最剧烈的地区,致使该区成为黄土高原沙黄土区中现代降水最多的地区。沙黄土和较多降水的组合,使晋陕蒙接壤区成为黄土高原现代侵蚀最剧烈的地区。     

全球气候变暖对黄土高原侵蚀产沙的影响

本文讨论未来全球气候变暖引起黄土高原侵蚀产沙的变化趋势。在分析气候期与侵蚀期关系的基础上,提出堆积期与侵蚀期都发生在干旱期,未来全球气候变暖进入湿润期,黄土高原侵蚀产沙趋于减少。     

黄土高原典型地区土壤侵蚀共性与特点

通过对黄土高原典型地区土壤侵蚀以往的研究结论进行综合分析，在比较土壤侵蚀相似性和差异性的基础上，对这些典型地区土壤侵蚀的共性与特点进行了研究，结果表明：1、黄土高原典型地区土壤侵蚀影响因素有降雨、地形及土地利用；2、黄土高原各典型地区主要侵蚀类型为水蚀及重力侵蚀；主要侵蚀发生时间为汛期；主要侵蚀空间分布特征为具有垂直分带性；3、绥德地区侵蚀产沙强烈，天水地区侵蚀相对轻微，安塞地区各种侵蚀特征典型。西峰地区土壤侵蚀特殊。     

泾河中游地区全新世成壤环境演变研究

根据长武ETC全新世土壤剖面的测定分析,探讨了该地区全新世成壤环境演变过程,阐明了先周时代土壤特征及人类耕作对成壤过程的影响。研究结果表明,全新世早期气候温和干燥,沙尘暴明显减弱,风尘堆积速率降低,具有轻微生物风化成壤作用;对应于全新世最适宜期,该地气候温暖湿润,生物风化成壤作用大于风尘堆积作用,为典型的黑垆土成壤期。从3 100 a B.P.开始,季风气候格局发生转变,气候干旱化,沙尘暴加剧,风尘堆积速率大于生物风化成壤速率,土壤资源自然退化,形成弱成壤层和黄土层,两层均属于全新世黄土L₀。先周时期耕作层对应古土壤层的顶部,土壤具有典型的团粒结构。3 100 a B.P.时的季风转变导致的气候干旱化与土壤退化促使了游牧民族南迁和"古公迁岐"事件的发生。     

黄土高原侵蚀环境与侵蚀速率的初步研究

黄土高原的侵蚀是一个地质过程.晚更新世以前高原已经过三个大的侵蚀堆积旋迥,主要沟谷系统和黄土地貌的塬梁峁格局已经形成.全新世以来黄土的堆积逐渐减缓,而侵蚀则进入新的发展时期.在自然因素和人类活动的共同作用下,土壤侵蚀加剧.根据侵蚀一堆积相关原理,利用黄河下游不同时期发育的冲积扇沉积模式,估算了全新世以来自然侵蚀速牵为7.9%,由于人类活动而引起的加速侵蚀的速率逐渐递增,至今已达到25%.     

Soil erosion and management on the Loess Plateau

1 Introduction The Loess Plateau situated in northern China covers the drainage basins in the middle reaches of the Yellow River. It starts from the western piedmont of Taihang Mountains in the east, reaches the eastern slope of the Wushao and Riyue mountains, connects the northern part of the Qinling Mountains in the south and borders the Great Wall in the north, covering an area of about 380,000 km2 (Figure 1). The region is overlain extensively by Quaternary loess in great thickness, …     

Soil erosion and management on the Loess Plateau

The Loess Plateau is well known to the world for its intense soil erosion. The root cause for river sedimentation of Yellow River (Huanghe) and its resultant "hanging river" in certain section is soil and water loss on the Loess Plateau. The Loess Plateau has a long cultivation history, hence population growth, vegetation degeneration and plugging constitute the chief reason for serious soil and water loss on Loess Plateau. This paper analyses several successful cases and failures in soil conservation, presents practical soil conservation technique and related benefit analysis, and discusses some effective methods adopted in China in soil erosion control, research directions and future perspectives on Loess Plateau.     

黄河中游土壤侵蚀与下游古河道三角洲演化的过程响应

根据黄土高原土壤侵蚀的周期特点，结合华北平原古河道，古三角洲的演化过程，应用泥沙输移的过程响应,分析了晚更新世以来黄河中游黄土高原土壤侵蚀与下游古河道，三角洲演化的关系，在人类历史之前，黄土高原土壤侵蚀基本上遵循自在生态环境演化规律，强裂侵蚀期发生在干冷向湿湿气候转化的过渡期，在强裂侵蚀的初期是古道形成期，强烈侵蚀期发生在干冷向温湿气候转化的过渡期，在强裂侵蚀的期是古河道形成期，强烈侵蚀的外营力迭加了人为作用，黄河下游河游泳以改道，三角洲横向扩展发生在强烈侵蚀的衰退期，人类历史时期，土壤侵蚀的外营力迭加了人为作用，破坏了地质历史时期的规律性，土壤侵蚀强度越来越强，基本上按照旱涝变化频率而演化，干冷期降雨不均匀系数增加，土训侵蚀加重，径流量较少，河床以淤积为主，是古河道形成期，正常年黄河泥少输移比接近于一，是三角洲进积期，温湿期降雨量增加，径流量加大，下游河流改道，三角洲横向发展。     

黄土高原侵蚀期研究

黄土高原在沉积的同时也存在着侵蚀,主要是流水、重力等因素造成的。这种侵蚀会受到气候、构造运动以及人类活动控制。资料显示,黄土高原存在3种基本的侵蚀期,一是气候侵蚀期,二是构造侵蚀期,三是人为因素侵蚀期。此外还有气候与构造共同作用产生的侵蚀期和构造与人类共同作用产生的侵蚀期。温湿期风尘堆积少,降水量增多,流水动力增强,是黄土高原理论上的侵蚀期。构造抬升引起侵蚀基准面下降,进而导致黄土高原加快侵蚀,出现构造侵蚀期。人类活动破坏了黄土高原的植被和土层结构,导致黄土高原侵蚀加剧,从而出现了人类因素引起的现代侵蚀加速期。在黄土发育的冷干期,由于植被稀疏,侵蚀量大于温湿期,但堆积量远大于侵蚀量。要改变现代侵蚀状况,就应当加强黄土高原生态环境治理。     

陕西关中全新世以来黄土塬区土壤侵蚀研究

通过对西安市蓝田县白鹿塬、长安区少陵塬以及宝鸡陵塬的土壤侵蚀调查，得出了关中平原全新世以来塬区土壤侵蚀的一些重要规律。研究表明，塬区土壤侵蚀较弱，侵蚀强弱以土层是否缺失或土层的厚度变化为主要依据。塬区普遍表现出塬边侵蚀强，愈向塬里，侵蚀愈弱，而且进人塬内部，侵蚀以低洼地为强，高平地为弱的规律。强烈的沟谷侵蚀实际是洼地侵蚀的一种演变形式。冷干和温湿气候均会产生土壤侵蚀，且全新世冷干期侵蚀的土层厚度比温湿期大约7倍，但这并不代表温湿气候比冷干气候更有利于黄土高原的发育。     

Remote-sensing data reveals the response of soil erosion intensity to land use change in Loess Plateau,China

Developing an effective approach to rapidly assess the effects of restoration projects on soil erosion intensity and their extensive spatial and temporal dynamics is important for regional ecosystem management and the development of soil conservation strategies in the future. This study applied a model that was developed at the pixel scale using water soil erosion indicators (land use, vegetation coverage and slope) to assess the soil erosion intensity in the Loess Plateau, China. Landsat TM/ETM+ images in 2000, 2005 and 2010 were used to produce land use maps based on the object-oriented classification method. The MODIS product MOD13Q1 was adopted to derive the vegetation coverage maps. The slope gradient maps were calculated based on data from the digital elevation model. The area of water soil-eroded land was classified into six grades by integrating slope gradients, land use and vegetation coverage. Results show that the Grain-To-Green Project in the Loess Plateau worked based on the land use changes from 2000 to 2010 and enhanced vegetation restoration and ecological conservation. These projects effectively prevented soil erosion. During this period, lands with moderate, severe, more severe and extremely severe soil erosion intensities significantly decreased and changed into less severe levels, respectively. Lands with slight and light soil erosion intensities increased. However, the total soil-eroded area in the Loess Plateau was reduced. The contributions of the seven provinces to the total soil-eroded area in the Loess Plateau and the composition of the soil erosion intensity level in each province are different. Lands with severe, more severe and extremely severe soil erosion intensities are mainly distributed in Qinghai, Ningxia, Gansu and Inner Mongolia. These areas, although relatively small, must be prioritised and preferentially treated.     

近30年来青海省风蚀气候侵蚀力时空差异及驱动力分析

青藏高原气候寒冷、多大风,冻融、风化和风蚀作用强烈,易发生土壤风蚀。气候对土壤风蚀的影响可用风蚀气候因子指数（C）度量。基于联合国粮农组织（FAO）提出的C计算方法,根据1984-2013年间连续完整的青海省气象站地面观测数据,应用地理加权回归模型（GWR）、重心及其转移模型,并结合本文定义的有效敏感性指数、有效影响面积等指标,得到全省风蚀气候侵蚀力及其影响因子的时空分布及其演化规律,并对其驱动力和机理进行了初步分析。结果表明：30年来,全省风蚀气候侵蚀力总体特征是西北高东南低并呈下降趋势,风蚀气候侵蚀力强的区域明显向西南扩展,20世纪80年代是柴达木盆地,90年代扩展到青南高原西北部边缘,21世纪基本涵盖了青南高原的西部;风速是影响风蚀气候侵蚀力的主导因子,其有效敏感区重心从柴达木盆地西南部边缘,移动到海拔较高的青南高原西部地区,这与高原近地面气旋系统中心总体移动趋势相反;其次是气温,其有效敏感区重心从海拔较低的青海省中部地区向海拔较高的青南高原移动,这与青南高原地区的海拔梯度式增温规律有关,即从高原边缘向高原腹地升温,且海拔越高,增温越快;降水主要影响柴达木盆地的侵蚀力,其有效敏感区重心向东南扩展,这可能与高原夏季风进退有关。研究结果可为青藏高原土壤风蚀灾害的预防、评估以及预测提供区域性差异化的技术支持与理论指导,也可为青藏高原乃至全球生源要素（C、N、P、S等）循环的大尺度驱动力研究提供新的研究视角。     

淮河上游全新世黄土及沉积成因

The dust source and transporting system are two indispensable aspects in the process of loess-palaeosol accumulation. It has been proved that the dust of the Loess Plateau mainly comes from the northwestern inland gobi and desert, transported by the East Asia monsoon systems and westerlies. However, there are little researches with respect to the dust source and deposition dynamics of the upper reaches of the Huaihe River. In the present study, we investigated and collected the YPC section with high resolution in the upper reaches of the Huaihe River. The chronological frame was reconstructed by optically stimulated luminescence (OSL) dating and correlated with the published loess time series. By comparison of the magnetic susceptibility (MS) and grain size (GS) of loess-soil profile among YPC profile, XJN profile (western Loess Plateau) and the JYC profile (southern Loess Plateau), we find similar climate change and pedogenic process between the upper reaches of the Huaihe River and the Loess Plateau, both experienced an extreme dry and the weakest pedogenesis during the last glacial, followed by a transitional episodes from the cold-dry last glacial to the warm-humid mid-Holocene and increased pedogenesis in the early Holocene, then a most humid-warm and strong pedogenesis in the mid-Holocene, and climate deterioration and decreased pedogenesis occurred during the late Holocene. But the MS of loess-soil profile sequences in the upper reaches of the Huaihe River was much lower than those in the Loess Plateau, and the GS was much coarser than those in the Loess Plateau. Comparison of GS for these three profiles revealed that there were different dust sources, which belonged to different aeolian transporting systems. The loess in the upper reaches of the Huaihe River was a wind blown deposition of near source, while the coarser dust mainly came from loose alluvial deposits of alluvial and proluvial fans of the Yellow River. The yielding and carrying dynamics of the dust in the Huaihe River is the northeast wind prevails in the winter half year.     

硬化地面与黄土高原水土流失

在界定硬化地面概念的基础上,进一步将硬化地面分为道路、城镇街区、农家场院三大类。并利用黄土高原400~600mm集流能力试验公式,对甘肃省陇东黄土高原沟壑区不同硬化地面的集流能力、侵蚀量进行分类实例分析研究,发现硬化地面集流能力远大于自然地面,因此城镇、道路、村庄附近的土壤侵蚀尤其严重。在黄土高原地区,不仅与之相关的沟壑的形成和发育,而且相关沟谷和河流的溯源侵蚀之力度大小也要受其影响。随着人口的增加,硬化地面面积越来越大,受其影响水土流失更加严重,这是历史时期黄土高原水土流失日益加剧的重要原因之一。今后黄土高原的水土保持工作,须将防治水土流失与解决水资源紧缺有机结合起来。其最佳解决途径,就是用硬化地面所集中的雨水,作为工农业生产和生活用水,以解决黄土高原水资源之不足。     

晚更新世以来黄土高原地区古季风的时空演化

通过对黄土高原不同地区黄土-古土壤序列、磁化率、粒度、同位素等的对比,认为黄土高原在末次间冰期有3次东亚季风环境效应突出的时期,分别距今130~116ka、116~94ka和84~74ka。季风锋面深入到榆林以北的地区。末次冰期有3次西北季风环境效应突出的时期,分别距今75~60ka,45~30ka和20~10ka,季风锋面推到长江流域,沙漠边界南移到定边与榆林之间。期间西北季风效应减弱,东亚季风锋面推进到吴堡与定边-米脂之间。全新世以来,东亚季风环境效应不断增强,在全新世中期达到最强,季风锋面推进到榆林以北地区。     

Capacity of soil loss control in the Loess Plateau based on soil erosion control degree

The capacity of soil and water conservation measures, defined as the maximum quantity of suitable soil and water conservation measures contained in a region, were determined for the Loess Plateau based on zones suitable for establishing terraced fields, forestland and grassland with the support of geographic information system (GIS) software. The minimum possible soil erosion modulus and actual soil erosion modulus in 2010 were calculated using the revised universal soil loss equation (RUSLE), and the ratio of the minimum possible soil erosion modulus under the capacity of soil and water conservation measures to the actual soil erosion modulus was defined as the soil erosion control degree. The control potential of soil erosion and water loss in the Loess Plateau was studied using this concept. Results showed that the actual soil erosion modulus was 3355 t?km^-2?a^-1, the minimum possible soil erosion modulus was 1921 t?km^-2?a^-1, and the soil erosion control degree was 0.57 (medium level) in the Loess Plateau in 2010. In terms of zoning, the control degree was relatively high in the river valley-plain area, soil-rocky mountainous area, and windy-sandy area, but relatively low in the soil-rocky hilly-forested area, hilly-gully area and plateau-gully area. The rate of erosion areas with a soil erosion modulus of less than 1000 t?km^-2?a^-1 increased from 50.48% to 57.71%, forest and grass coverage rose from 56.74% to 69.15%, rate of terraced fields increased from 4.36% to 19.03%, and per capita grain available rose from 418 kg?a^-1 to 459 kg?a^-1 under the capacity of soil and water conservation measures compared with actual conditions. These research results are of some guiding significance for soil and water loss control in the Loess Plateau.