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1.
一万年来灵武水洞沟遗址古气候的新认识 总被引：1，自引：0，他引：1
李秉成 《干旱区资源与环境》2006,20(4):25-29
本文通过对宁夏水洞沟遗址剖面的进一步地质调查、密集采样和孢粉分析,笔者详细地讨论了该区植被的演替,论证了全新世古气候环境的特征,总结了早、中、晚全新世在该区发育的植被及其所代表的气候环境。结果表明:早全新世植被为疏林草原、干草原→草甸草原,气候偏干冷→温和半湿润;中全新世早期植被为阔叶乔灌丛草原→针叶乔灌丛草原→阔叶疏林草原,晚期植被为疏林草原,气候相对温暖、稍凉→较温暖;晚全新世植被为干草原,气候寒冷。 相似文献
2.
关中富平地区近一万年植被和气候的讨论 总被引：1，自引：0，他引：1
为了了解黄土高原中部近一万年以来古气候演化特征,通过对关中富平剖面的地质调查、密集采样和31个样品的孢粉分析,将孢粉图式划分为Ⅰ、Ⅱ、Ⅲ三个带分别代表早、中、晚三个时期的孢粉带:Ⅰ带为松-菊-香蒲组合带,以草本植物花粉占优势,针叶树植物花粉含量较高为特征;Ⅱ带为松-栎-蒿-环纹藻组合带,以乔木花粉增加,草本植物花粉减少为特征;Ⅲ带为栎-松-蒿组合带,以草本植物花粉增加,乔木花粉减少为特征。结果表明:早全新世植被为森林草原-干草原,气候干凉-干冷;中全新世植被为森林草原与针阔叶混交林草原,气候温暖半湿润;晚全新世植被为森林草原或疏林草原,气候干旱偏暖-温凉干旱。 相似文献
3.
随着孢粉研究分辨率不断提高,许多学者对黄土沉积物进行了高分辨率的孢粉分析。单个剖面的孢粉图谱可以反映研究地区的总体植被变化情况。在研究方法基本相同的情况下,同种花粉在不同剖面的百分含量图谱,可以大体上反映该种植被的分布情况。本文在前人研究的基础上,选取了两个地区六个剖面中八种有生态指示意义的科属进行合成,以此得出:早中全新世,黄土/沙漠过渡带沟谷区的环境条件优于黄土塬区;而在晚全新世,植被的地带性特征才表现得比较明显。对可能的原因进行了分析,但仍需要更多证据和更为深入的研究。 相似文献
4.
一万年以来西安鱼包头黄土剖面磁化率的古气候环境再讨论 总被引：1，自引：0，他引：1
对西安地区全新世以来的环境演变特征进行研究,从而为预测西安地区乃至中国和全球未来环境的发展趋势提供依据。通过对西安神禾塬鱼包头村典型剖面全新世黄土-古土壤地层的岩性描述、地层划分和对比,结合泾阳县新庄村AMS14C的年代测定和其他学者的测年数据,建立了该地区全新世以来黄土沉积年代序列。根据磁化率气候替代指标显示的曲线特征,阐述了这一替代指标在剖面上的变化规律,探讨了该黄土剖面所反映的东亚冬、夏季风强弱变化特点,论证和详细分析了西安地区全新世以来环境变化的特征和规律,进而对该剖面磁化率曲线特征与其他学者的孢粉谱建立的温度曲线对比。对西安地区全新世以来古气候的阶段性进行了详细分析和论证。将西安地区10000年以来的气候演变划分为7个气候阶段。 相似文献
5.
通过对塔里木盆地北部全新世地层中２７块样品的孢粉分析，根据其组合特征并结合表土花粉分析，本区全新世以来除了塔里木河中游隐域性植被成分随着河流改道变化频繁外，两侧显域性的早生、超旱生荒漠植被成分无明显变化，它们的生境反映了气候环境总的形势是持续干旱的。但全新世地层中孢粉种属和丰度的变化，蒿属、藜科和麻黄花粉相对数量的增减也说明了在干旱背景中本区气候有微弱的干湿波动，表现为全新世早期和晚期气候偏凉湿，中期气候干暖，但干暖期鼎盛阶段略湿。 相似文献
6.
为预测西安地区乃至中国和全球未来环境的发展趋势提供依据,通过对西安地区泾阳南塬寨头村典型剖面全新世黄土—古土壤地层的岩性描述、地层划分和对比,结合泾阳县新庄村AMS14C的年代测定和其他学者的测年数据,建立了该地区全新世以来黄土沉积年代序列。根据磁化率气候替代指标显示的曲线特征,阐述了这一替代指标在剖面上的变化规律,探讨了该黄土剖面所反映的东亚冬、夏季风强弱变化特点,论证和详细分析了西安地区全新世以来环境变化的特征和规律,进而对该剖面磁化率曲线特征与其他学者的孢粉谱建立的温度曲线对比,对西安地区全新世以来古气候的阶段性进行了详细分析和论证。将西安地区10000年以来的气候演变划分为7个气候阶段。 相似文献
7.
气候变暖对中亚干旱区植物带来了巨大的威胁。因观测时间受限，我们无法更好地理解长时间尺度干旱区植物多样性与气候变化之间的关系。但地质记录中的孢粉给我们提供了机会来理解过去植物存在、分布和多样性特征。以阿尔泰山为例，选择不同海拔的3个孢粉序列（高海拔-哈拉萨孜泥炭、中海拔-娜仁夏泥炭和低海拔-喀纳斯湖）来研究孢粉类型多样性变化特征及其对全新世气候变化的响应模式。结果显示：（1）阿尔泰山全新世孢粉类型多样性变化呈现出独特的格局。详细来说，全新世早期随着气候的变暖，森林上限开始向上迁移，使得高海拔孢粉类型多样性增加。（2）全新世中期气候暖湿，森林上限和下限的向上和向下迁移使得高低海拔孢粉类型多样性较高，但以泰加林主导的森林带孢粉类型多样性偏低，主要归咎于物种均匀度的下降。（3）全新世晚期气候变冷且更湿润，森林带上限向下移动，使得中海拔孢粉类型多样性显著提高。全新世阶段森林带内孢粉类型多样性变化幅度最大，该区域是气候响应最敏感区和最脆弱区。本研究有助于我们掌握山地植被带对全新世气候变化的响应模式，为探索山地植被迁移历史提供关键证据。 相似文献
8.
孢粉是恢复古气候、古植被重要的代用指标。根据已有的研究成果,猪野泽孢粉组合所指示的全新世气候环境变化存在较大分歧。湖泊碳酸盐沉积可以指示碱性沉积环境,而碱性环境对孢粉的腐蚀较大,影响花粉的保存。所以,研究湖泊沉积物中碳酸盐含量与孢粉保存的关系,可以探讨该区域花粉保存是否受到过盐湖沉积的影响,并可进一步探讨该区域花粉组合的差异是否与花粉保存有关。结果表明：在猪野泽全新世两个成湖期,高碳酸盐含量与高孢粉浓度相对应。虽然,高碳酸盐含量对应的强碱性环境对孢粉的腐蚀性大,但当时猪野泽成湖期内气候温暖湿润,孢粉输入量非常大,以至于碱性沉积环境不足以改变孢粉的浓度。因此,猪野泽不同位置沉积物碳酸盐含量与花粉保存情况无明显相关关系,以上分歧的出现不是由孢粉保存引起的。 相似文献
9.
西安临潼白庙剖面全新世黄土与环境变化 总被引：2，自引：0，他引：2
西安临潼白庙剖面全新世发育了两层黄土与两层古土壤 ,通过对该剖面各层黄土与古土壤中微量元素Zn ,Ni,Cr,Co ,Ba ,Rb ,Sr的含量测定 ,研究了当时土壤发育的强弱和气候环境的变化。结果表明 ,其微量元素具有指示冬夏季风等环境变化的重要作用 ,反映了全新世以来该区发生过 4次较大的生物、气候环境的变化 ;古土壤代表的温湿期气候比现今明显 ,当时夏季风活动加强 ,但冬夏季风活动强度与持续时间相近 ,并非是夏季风占优势 ,黄土发育时的气候与现今西安地区类似 相似文献
10.
汾渭盆地全新世成壤环境演变比较研究 总被引：3，自引：4，他引：3
通过对汾渭盆地全新世土壤的野外考察以及磁化率和高分辨率CaCO3 的分析 ,揭示了该区域土壤成壤过程与气候变化关系。研究表明 ,汾渭盆地全新世的S0 地层形成于全球性的全新世气候最适宜期 ,约从 85 0 0aBP土壤开始发育 ,形成较厚的S0 层。约从 310 0aBP起始 ,气候发生变化 ,干旱和沙尘堆积形成了黄土L0 层和现代表土层。土壤剖面磁化率与CaCO3 指标反映 ,由于地带性因素存在 ,全新世汾河盆地古土壤S0 的成壤强度远远低于渭河盆地。在全新世气候最适宜期 ,两地气候和环境的差异扩大 ,而晚更新世马兰黄土堆积期间和全新世其它主要阶段 ,两地气候和环境的差异相对减小。 相似文献
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12.
Influences of sand cover on erosion processes of loess slopes based on rainfall simulation experiments 总被引：1，自引：0，他引：1
Aeolian-fluvial interplay erosion regions are subject to intense soil erosion and are of particular concern in loess areas of northwestern China.Understanding the composition,distribution,and transport processes of eroded sediments in these regions is of considerable scientific significance for controlling soil erosion.In this study,based on laboratory rainfall simulation experiments,we analyzed rainfall-induced erosion processes on sand-covered loess slopes(SS)with different sand cover patterns(including length and thickness)and uncovered loess slopes(LS)to investigate the influences of sand cover on erosion processes of loess slopes in case regions of aeolian-fluvial erosion.The grain-size curves of eroded sediments were fitted using the Weibull function.Compositions of eroded sediments under different sand cover patterns and rainfall intensities were analyzed to explore sediment transport modes of SS.The influences of sand cover amount and pattern on erosion processes of loess slopes were also discussed.The results show that sand cover on loess slopes influences the proportion of loess erosion and that the compositions of eroded sediments vary between SS and LS.Sand cover on loess slopes transforms silt erosion into sand erosion by reducing splash erosion and changing the rainfall-induced erosion processes.The percentage of eroded sand from SS in the early stage of runoff and sediment generation is always higher than that in the late stage.Sand cover on loess slopes aggravates loess erosion,not only by adding sand as additional eroded sediments but also by increasing the amount of eroded loess,compared with the loess slopes without sand cover.The influence of sand cover pattern on runoff yield and the amount of eroded sediments is larger than that of sand cover amount.Furthermore,given the same sand cover pattern,a thicker sand cover could increase sand erosion while a thinner sand cover could aggravate loess erosion.This difference explains the existence of intense erosion on slopes that are thinly covered with sand in regions where aeolian erosion and fluvial erosion interact. 相似文献
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14.
Loess deposits with varying thickness are widely distributed on the intermontane valleys and piedmont zones on the northern side of the central Shandong mountainous regions. However, the basal ages and material resources of the loess deposits are not clear. The paper studied the Qingzhou loess profile in Shandong with magnetostratigraphic and optical stimulated luminescence (OSL) methods and further investigated its main provenances with the mineralogical methods. The magnetostratigraphic results showed that the Brunhes/Matuyama (B/M) reversal boundary was not recognized, suggesting a basal age younger than 0.78 Ma. Extrapolations by sedimentation rates, based on the upper part depositional rate from the OSL age, the basal age of the Qingzhou loess is about 0.5 Ma. Until now, older loess deposits have not been reported on the northern side of the central Shandong mountainous regions. The results of the paper indicate that the loess deposits in this area might have strated from the Middle Pleistocene. The basal age of Qingzhou loess is approximately synchronous with the Xiashu loess in the middle-lower reaches of Yangtze River. Major components of clay minerals in the Qingzhou profile are dominated by illite. Other clay mineral compositions are mainly smectite, chlorite and kaolinite, which are similar with the Xifeng loess in the Loess Plateau. However, the contents of smectite and the ratios of illite and kaolinte in the Qingzhou loess samples are higher than those in the Xifeng loess samples of the Loess Plateau, indicating that the loess in the northern side of the central Shandong mountainous regions has different sources from that of the loess deposits in the Loess Plateau. The clay mineral analysis further reinforces the earlier conclu- sion that the marine strata exposed in the Laizhou Bay and the fluvial plain of the lower reaches of Yellow River during the glacier periods are the main material sources for the Qingzhou loess deposits, which is an indicator to the local aridification of the lower reaches of the Yellow River. Loess deposition in the central Shandong mountainous regions started at around 0.5 Ma. The age of Qingzhou loess is approximately synchronous with the ongoing high-latitude cold since the Middle Pleistocene, which indicates that strengthened East Asian winter monsoon was sufficiently energetic to bring substantial quantities of material from the marine strata exposed in the Laizhou Bay and the fluvial plain of the lower reaches of the Yellow River to the central Shandong mountainous regions. The results therefore suggest that both regional geological process and global changes were responsible for the formation of Qingzhou loess since Middle Pleistocene. 相似文献
15.
甘肃黄土高原土壤农业水分常数分布特征 总被引：4，自引：0，他引：4
通过对黄土高原23个农业气象观测站及3个农业气象试验站作物观测地段的土壤农业水分常数分析,以揭示该地域农业水分特性的分布特征。结果显示:在甘肃黄土高原,土壤容重从北到南、从浅层到深层呈减少趋势;凋萎湿度地域及垂直分布变化不大;田间持水量地域分布特征明显,陇西黄土高原大于陇东黄土高原;干旱的临界土壤含水量基本上为北部小于南部,最大值出现在陇西黄土高原的中部。 相似文献
16.
通过对长安双竹村夏、秋季不同性质土层CO2释放量的测定,本文研究了不同性质土层CO2释放规律及其差异。资料表明,从当日早晨到次日早晨,不同性质土层土壤CO2释放量均呈现由低到高再到低的变化规律;土壤CO2释放量与土层性质有密切关系,马兰黄土土层CO2释放量最高,其次是黏性土,释放量最低的是含砾石中细砂土;土层CO2释放量变化与气温的变化呈现负相关。 相似文献
17.
《干旱区科学》2017,(4)
Dew is an important water source for plants in arid and semi-arid regions. However, information on dew is scarce in such regions. In this study, we explored dew formation, amount, and duration of rain-fed jujube(Zizyphus jujube Mill) trees in a semi-arid loess hilly region of China(i.e., Mizhi County). The data included dew intensity and duration, relative humidity, temperature, and wind speed measured from 26 July to 23 October, 2012 and from 24 June to 17 October, 2013 using a micro-climate system(including dielectric leaf wetness sensors, VP-3 Relative Humidity/Temperature Sensor, High Resolution Rain Gauge, and Davis Cup Anemometer). The results show that atmospheric conditions of relative humidity of 78% and dew point temperature of 1°C–3°C are significantly favorable to dew formation. Compared with the rainfall, dew was characterized by high frequency, strong stability, and long duration. Furthermore, heavy dew accounted for a large proportion of the total amount. The empirical models(i.e., relative humidity model(RH model) and dew point depression model(DPD model)) for daily dew duration estimation performed well at 15-min intervals, with low errors ranging between 1.29 and 1.60 h, respectively. But it should be noted that the models should be calibrated firstly by determining the optimal thresholds of relatively humidity for RH model and dew point depression for DPD model. For rain-fed jujube trees in the semi-arid loess hilly regions of China, the optimal threshold of relative humidity was 78%, and the optimal upper and lower thresholds of dew point depression were 1°C and 5°C, respectively. The study further demonstrates that dew is an important water resource that cannot be ignored for rain-fed jujube trees and may affect water balance at regional scales. 相似文献
18.
黄土高原侵蚀性降雨特征分析 总被引：13，自引：1，他引：12
侵蚀性降雨是黄土高原地区剧烈土壤水蚀的原动力。利用黄土高原6个水土保持试验站20年以上的断点雨强资料和30年的气象站逐日降水观测资料,分析了侵蚀性降雨的发生频率、次降雨量、次降雨历时、次降雨侵蚀力以及降雨时程分布的统计特征:(1)黄土高原6个站侵蚀性降雨平均发生频率分别为7.0~13.4天/年,各站侵蚀性降雨的场雨量均值介于19.17~25.38mm,但变异性很大。各站次降水量、降雨历时和次降雨侵蚀力的频率分布都近似为指数分布。(2)根据本文设定的雨峰标准,黄土高原单峰降水占总降水次数的65%,双峰降水占30%,三峰降水占5%。峰值雨强的频率分布函数大致为Gamma分布中的一种,或者是偏正态分布,侵蚀性降水多为前锋型。上述结果可作为降水过程的随机模拟理论依据,也可以为全面深入研究土壤水蚀机理提供参考。 相似文献
19.
Youjun WANG 《干旱区科学》2019,11(2):217-227
The Alagxa Plateau, in the margin of the northeastern Tibetan Plateau, is one of the most important dust source areas in East Asia, and the widespread sandy desert in the area is important both as a reservoir and a source of eolian silty. The northeastern margin of the Tibetan Plateau is one of the most actively-growing mountain belt on earth, and has large amounts of debris, with masses of fine grained material, which were continuously mobilized and deposited in the Alagxa Plateau by rivers, forming broad alluvial fans. It is possible that the role of fluvial sediments as a source of silty dust in the Alagxa Plateau has been underestimated. In this study, we test this hypothesis by investigating the iron mineralogical and geochemical characteristics of the fluvial sediments and the surface material of the sandy desert in the Alagxa Plateau, and comparing them with paleo-eolian dust deposits(loess) in the adjacent Chinese Loess Plateau(CLP) to investigate the possible linkages among the fluvial sediments, sandy desert and the last glacial loess of the CLP. The results show that sandy desert typically have high contents of goethite, and high ratios of goethite to hematite, similar to the fluvial sediments in the Alagxa Plateau. Based on the major element characteristics, field investigations and the results of previous studies, we found a genetic link between the silt component of the fluvial sediments and the sandy desert in the Alagxa Plateau with high value of Gt(goethite) and similarity of the Gt/(Hm(hematite)+Gt) ratio. But the silt component of the sandy desert main come from the adjacent fluvial sediments. The iron mineralogical characteristics(χ(magnetic susceptibility), χARM(anhysteretic susceptibility), SIRM(saturation isothermal remanent magnetization) and SIRM_(AF100 mT)(SIRM demagnetized at 100 mT)) of the CLP samples overlap with those of the fluvial sediments in the Alagxa Plateau, but there is a mismatch with the sandy desert samples. This suggests that the fluvial sediments are the source of a large amount of silty material which could be transported to the CLP. Therefore, we conclude that the fluvial sediment in the Alagxa Plateau is an important source of eolian silt, which is deposited in downwind region, and that this source has been previously underestimated. 相似文献