A 1.5 Ma sporopollen record of paleoecologic environment evolution in the central Chinese Loess Plateau

A 1.5 Ma sporopollen record was obtained from a continuous loess-paleosol sequence at Chaona in the central Chinese Loess Plateau. It shows that (1) arid herbs of largely Artemisia and Chenopodiaceae and arbors of mainly Pinus, Betula and Quercus dominate loess and paleosol, respectively, reflecting cycles of cold-dry and warm-humid conditions of glaciation and interglaciation; (2) that similar vegetation pattern and cold-dry condition were found in times of unusual thick and coarse loesses L9 and L15, which have been regarded as two extremely cold and dry times as indicated by inorganic climatic proxies; and (3) that shifts of vegetations from earlier forest-steppe to open-forest and steppe and then to steppe were found at 0.95 and 0.5 Ma,implying a stepwise of drying of the Loess Plateau in the Quaternary.     

陇中黄土高原全新世植被变化及干旱事件的孢粉记录

甘肃定西、秦安等地5个全新世黄土沉积剖面的孢粉记录,分别以每个样品分辨率为200—20 a,揭示了研究区1万多年以来古植被曾经历过草原、森林草原(或疏林草原)、针叶林或温带森林以及荒漠草原几种植被的多次演化过程.大部分时间内是以草原或森林草原(或疏林草原)植被为主.在全新世中期,约7.6—5.9 kaBP有近1700a时间发育有森林植被,在这个时期当地自然植被覆盖度较高,反映当时气候环境比较温湿.而草原或疏林草原发育时期植被往往较稀疏,反映气候相对的干冷.根据出现的不同类型植物的孢粉浓度及其生态环境特性,结合地层、有机质、粒度、蜗牛化石和炭屑等其他代用指标分析结果反映,早中全新世是比较温暖湿润的时期,大约在8.8—5.8 kaBP高湿润期最明显,呈现湿地/沼泽沉积地层;自3.8 kaBP以后孢粉成分、含量和浓度明显降低,植被开始向荒漠草原化演变,气候环境总的变化趋势是逐渐变冷干.以苏家湾和大地湾剖面为例,根据云杉含量和针叶树种总量以及花粉总浓度计算结果推测,全新世可能存在着7次较明显的气候干寒事件.     

黄土高原退耕还林(草)区的鼠害治理问题

综述了黄土高原退耕还林(草)过程中鼠害问题及防治现状.退耕(牧)还林(草)对黄土高原地区的生态建设与可持续发展意义重大,鼠害始终是困扰黄土高原植被建设的重要问题,截至2004年底,西部12个省(区)的鼠害实际发生面积已达264.3×104hm2,地处黄土高原的陕西、甘肃、宁夏、青海、山西、内蒙古为最严重的省(区);环境变化、人类活动的压力、鼠类的天敌减少以及退耕还林(草)中缺少科学观念,仓促实施是鼠害发生的主要原因;鼠害对植被建设、经济发展、生态环境以及公共卫生安全影响巨大,但在治理方法上尚没有取得突破性的进展;本文对黄土高原鼠害治理现状和存在问题进行了分析,提出建议:(1)退耕还林(草)在总体规划中应纳入包括鼠害防治在内的林、草管护措施;(2)加大防治资金投入;(3)加强科学研究;(4)健全预测预报体系.     

渭北黄土高原丘陵沟壑区酸枣灌丛生物量调查研究

酸枣灌丛适应性强、耐干旱、根系发达、生物积累大，是渭北黄土丘陵区水土保持主要灌木树种，应采取封育措施，保护和扩大酸枣灌丛植被。     

论淤地坝建设在我省黄土高原地区的地位和作用

淤地坝在拦泥保土,减少入黄泥沙,防洪减灾,淤地造田,提高粮食产量,解决人畜饮水,促进退耕,优化土地利用结构,促进群众脱贫致富奔小康等方面发挥着重要作用。因此,我省黄土高原地区应继续坚持以小流域为单元,以坝系建设为主体,统一规划,分步实施,稳步推进淤地坝建设。     

黄土高原DEM分辨率对提取坡度精度的影响

在黄土高原选取代表不同地貌类型的延川、绥德、富县3个研究样区,以及1∶1万地形图所建立的不同水平分辨率数字高程模型(DEM)为研究对象,分别分析每一大样区不同水平分辨率DEM所提取坡度的面积误差变化规律.提出面积百分比加权总体误差和面积百分比平均总体误差的指标,在每一大样区随机选取20个试验样区,得到两项误差指标与水平分辨率的线性函数关系.根据线性函数关系,由已知误差求得所需要的水平分辨率范围,并在每一大样区的16个随机检验样区通过检验.线性函数关系模型的建立,可望为实际工作选取适宜的水平分辨率提供依据,对于在保证精度的条件下节约成本,减小数据量具有一定意义.文中最后提出,所指出的两项指标不适用于风沙-黄土过渡区域.     

Do multiple cycles of aeolian deposit-pedogenesis exist in the reticulate red clay sections in southern China？

The Xiangyang reticulate red clay section was newly sampled in high-resolution. The viewpoints different from the previous studies^[1-7] are put forward after studying Munsell color values, weathering degrees, magnetic parameters and stable carbon isotopic compositions of the section.They are as follows: (1) The curves of hue, DCB extracted iron (Fed), DCB extracted iron/total iron ratio (Fed/Fet),weathering index (BA) of the section show that the redness is not significantly correlated with the weathering degree of the layers though the uppermost yellow-brown-colored layer is relatively weakly weathered. The variation in hues of the section is possibly attributed to the change of hematite and goethite contents. It is insufficient to determine the existence of the multiple deposit-pedogenesis cycles in the section, like the Ioess-paleosol sequence in Chinese Loess Plateau, only by the color variation. (2) Magnetic susceptibility (X) values in the non-reticulate and weakly reticulate layers are high; but are quite low in the reticulate red clay layer. The former are more than ten times higher than the latter because of the leaching and collapse of superparamagnetic (SP) and stable single domain (SSD) magnetic particles during the plinthitic processes. Hence, X values in the section are not controlled by weathering and pedogenic processes, and no longer have clear paleoclimatic implication. It is not correct to prove the existence of the multiple deposit-pedogenesis cycles in the section using X curves. (3) The organic δ^13C curve of the section illustrates the reduction of forests and increasing of C4 plants in the study area since the late stage of the Quaternary period. It could not prove the existence of the multiple deposit-pedogenesis cycles in the section either. (4) As a matter of fact, it is difficult to prove the existence of the multiple deposit-pedogenesis cycles in the Xiangyang section like the Ioess-paleosol sequence in Chinese Loess Plateau using the evidence available currently.     

黄土高原地下水资源与水质初步评价

通过黄土高原地质、地貌及水文钻孔资料的初步分析 ,认为 :该地域地下水的分布、赋存层位、水质、富水程度等主要受地貌、地质构造、岩性、气候及水文等条件控制 ;其中松散岩类等裂 (孔 )隙水以大气降水补给为主 ,多数以泉水形式排泄于沟谷中。结合降水量、排泄方式及矿化度的不同 ,对各种成因地下水进行了综合水质评价 ,得出该区域潜水地下水大部分为重碳酸型低矿化度淡水 ,矿化度大于 1 g/L的微咸水、咸水主要分布在宁夏银北、西海固地区和甘肃陇西及内蒙古河套地区 ,为高原水资源开发利用提供了水文地质资料     

黄土高原小流域综合整治主要矛盾的关系研究

经过多年在对黄土高原小流域进行攻关研究的基础上,认为在黄封上流域综合整治的过程中的存在着几个较为重要的矛盾,只有认识和处理好这些矛盾的相关关系,黄土高原小流域综合整治的理论与实践才可趋于完善,整治的成果才可得以巩固。     

黄土高原河流演化研究中的几个地学问题——与朱照宇、丁仲礼先生商榷

以河流阶地与堆积黄土、河流起源与冰期、河流演化与新构造运动等3个问题与《专著》商榷.其中风成黄土不应属河流冲积阶地组分,黄土层厚度尺寸不应计入河流阶地面高度中;河流起源应考虑冰期要素,离石黄土中第二砂质黄土层应属鄱阳冰期层位.冰期前为河流起源Ⅰ期,冰期后为河流起源Ⅱ期;河流演化是在新构造运动支配下发生,黄河、洛河、汾河等演化均属各自流域内多个盆地间贯通的首次演化;河流尚有跨两大已成河流域间的二次演化;给出了洛河演化模式阶地位相图.