河西走廊榆木山前土壤发育特征及其随时间的演变关系          下载免费PDF全文

邢成起  梁晓鹏  张杰  董治平 《地震工程学报》1998,20(3):95-104

在河西走廊榆木山前开展了旨在用于活动构造测年工作的土壤发育年代学新方法的研究。通过在不同时代河流阶地上开挖土壤探槽,系统采集土壤样品并进行化学成分分析,以及对各级河流阶地形成年代的＾１４Ｃ和热释光年龄测定,详细研究了该区与断层新活动有关的土壤发育的主要物理和化学特性及其随时间（年代）的演变规律,初步建立起了土壤ＣａＣＯ３含量和ＣａＣＯ３累积指数数值与发育年代之间的定量计算关系式,经回检和对比分析认  相似文献   

气候变暖对河西走廊棉花生产影响的成因与对策研究   总被引：6，自引：1，他引：5  

邓振镛  王鹤龄  李国昌  辛吉武  张宇飞  徐金芳 《地球科学进展》2008,23(2):160-166

揭示了气候变化对河西走廊棉花生产有着显著影响,实际上使其生育期延长20天,霜前花减少30％;适生区域提高100 m左右,面积扩大7倍;衣分提高2个百分点,气候产量增加54.3％的基本事实。探明了现代气候变暖对高原地区喜热作物棉花产生非常有利影响的重要原因,是由于≥10℃积温升高131℃,裂铃至停止生长关键期增温30℃;最低气温升高0.9℃,春季增温加快,秋季降温减缓,使生长期热量资源得到较大补偿,气候生态适应性更适宜,与棉花生理需求指标更接近。预测未来10～15年内≥10℃积温可能增加100～300℃,适生区域升高100 m左右,建议稳步扩大面积20％～30％,并提出按不同种植区域采取相适应的农业生产技术等建议。  相似文献   

Drivers of variability in large wood loads along the fluvial continuum of a Mediterranean intermittent river     

Tomáš Galia  Tereza Macurová  Leonidas Vardakas  Václav Škarpich  Tereza Matušková  Eleni Kalogianni 《地球表面变化过程与地形》2020,45(9):2048-2062

Although in-channel and floodplain large wood (LW) has been recognized as an important component of lotic ecosystems, there is still limited knowledge on the recruitment, mobility and retention of LW in rivers with an intermittent hydrological regime. In this study, we analysed the LW characteristics and related reach-scale variables of 22 reaches in a Mediterranean intermittent river (Evrotas, Greece) in order to identify predictors of in-channel and floodplain LW distribution. Our results indicated high downstream variation in LW volumes in the fluvial corridor (0.05–25.51 m³/ha for in-channel LW and 0–30.88 m³/ha for floodplain LW). In-channel and floodplain LW retention was primarily driven by the hydrological regime of the studied reaches (i.e. perennial or non-perennial) with higher volumes of LW observed in perennial sections. The width of the riparian corridor was an important predictor of LW storage at the reach scale. Non-perennial reaches had a disproportionally larger number of relatively small-diameter living trees at the expense of mature trees with larger diameters typical for riparian stands functioning as LW recruitment areas in perennial reaches. The smaller dimensions of in-channel LW in non-perennial reaches, coupled with the dominance of loose LW pieces, implies frequent LW transport during ordinary flood events. Nevertheless, overall low LW retention in the fluvial corridor under non-perennial flow regime predicts low volumes of mobilized LW. In contrast, the recruitment of relatively long and large-diameter LW from mature riparian stands in perennial reaches, together with additional LW stabilization by banks, bed sediments, living trees or other LW pieces decreases the potential for further LW transport. © 2020 John Wiley & Sons, Ltd.  相似文献   

中巴农产品贸易的效率评价与潜力预测研究          下载免费PDF全文

舒芹  苏洋  李凤  汪晶晶  黄玉洁  刘蕾 《干旱区地理》2019,42(6):1454-1460

基于1992—2016年中国与南亚八国的相关贸易数据,从巴基斯坦的角度出发,选取南亚七国作为参考对象,利用随机前沿引力模型对其双边农产品贸易总额及出口农产品贸易总额的面板数据进行测算。研究结果表明：人均GDP、国家类型等因素对中巴双边农产品贸易发展产生正向影响;人口、距离因素则阻碍中巴农产品贸易发展;中巴双边农产品贸易效率（平均值约0.689）高于中国对巴基斯坦出口农产品贸易效率（平均值约0.615）;中国对巴基斯坦实际农产品出口总额未达到最佳的贸易前沿水平,因此农产品出口还存在较大的提升空间。  相似文献   

国土空间规划：基础设施与公共服务设施单幅总图的研制   总被引：1，自引：1，他引：0  

王姣娥  陈卓  景悦  黄洁  金凤君 《地理研究》2019,38(10):2496-2505

基础设施的建设与布局是在遵循自然系统格局的基础上,由人类活动所引致的物质环境再建构和空间秩序再安排,是构建和引领区域空间结构的重要支撑体系,因此一直是区域发展类规划的重要组成部分。结合省级空间规划试点工作,提出符合空间规划目标的基础设施与公共服务设施编制方案与技术流程,强调专项规划与“三区三线”、空间布局总图的关系,并以福建省为例,设计了基础设施与公共服务设施单幅总图的编制技术流程,以期为其他地区空间规划的编制提供借鉴意义。  相似文献   

Evaporation from a riparian system in a semi-arid environment     

Helene E. Unland  Altaf M. Arain  Chawn Harlow  Paul R. Houser  Jaime Garatuza-Payan  Paul Scott  Omer L. Sen  W. James Shuttleworth 《水文研究》1998,12(4):527-542

Measurements of micrometeorological variables were made for a complete annual cycle using an automatic weather station and two energy budget–Bowen ratio systems at a field site adjacent to the Santa Cruz River in southern Arizona. These data were used to provide the basis of an estimate of the evaporation from a one-mile long losing reach of a riparian corridor in this semi-arid environment. A remotely sensed map of vegetation cover was used to stratify the corridor into five categories of surface cover. The total evaporation was calculated as the area-weighted average of the measured evaporation for sampled areas of the two most common covers, and appropriate estimates of evaporation for the less common covers. Measurements showed a substantial, seasonally dependent evaporation from the taller, deep-rooted riparian cover in the study reach, while the short, sparse vegetation provided little evaporation. In terms of the volume of water evaporated from the study reach, the evaporation from irrigated agriculture accounts for almost half of the total loss, while the majority of the remaining evaporation is from the taller riparian vegetation covers, with about one-quarter of the total loss estimated as coming from obligatory phreatophytes, primarily cottonwood. © 1998 John Wiley & Sons, Ltd.  相似文献   

基于MCR模型的南方稀土矿区生态安全格局分析   总被引：6，自引：2，他引：4  

李恒凯  刘玉婷  李芹  王秀丽 《地理科学》2020,40(6):989-998

南方稀土矿区是世界上主要的离子型稀土矿生产基地,对当地乃至中国都带来了不可估量的经济价值,但是在追求稀土开采的经济效益的同时,由于采矿工艺的不足,产生了一系列环境问题,威胁矿区的生态安全。以赣州岭北稀土矿区为例,基于景观生态安全格局理论及最小累积阻力模型（Minimum Cumulative Resistance Model,MCR）方法,对矿区的生态源地、生态廊道、生态节点等进行判别与分析,构建了矿区2009、2013和2018年3个年份的景观生态安全格局。结果表明：① 稀土矿区的生态源地的斑块面积较小,主要集中于矿区的东西两侧。② 在选取年份期间,稀土矿区的生态源地面积、生态廊道、辐射通道及生态节点数量都在不断增加,表明在这9 a间,稀土矿区景观生态安全状况得到了一定的改善,但相关部门仍需对稀土矿区的生态安全格局进行进一步的规划和优化。  相似文献   

多塔楼高层建筑连廊结构的柔性连接设计及试验研究     

黄襄云  刁云云  谭平  沈朝勇 《地震工程与工程振动》2007,27(6):112-118

本文提出了高层建筑多塔楼连廊结构采用柔性连接方式,并进行了结构抗震分析和模拟地震振动台试验研究。计算和试验结果表明连廊采取柔性连接后,结构在连廊连接处的受力状况得到改善,结构的基底剪力明显减小,柔性连接有一定的耗能能力,提高了建筑物的抗震性能。  相似文献   

黄土丘陵区廊道研究初探     

王峰  石辉 《云南地理环境研究》2005,17(5):10-14,72

以景观生态系统理论为指导,对黄土丘陵区进行了地貌景观结构分析,确定了其“廊道、斑块、基质”的景观模式,认为黄土堆积物可被看作为黄土丘陵区的基质;墚、塬、峁、台地和残塬等为被侵蚀的一种残存斑块;沟谷、河谷和道路是主要的廊道。提出了沟谷廊道的概念,初步分析了沟谷廊道在黄土丘陵区的特点:三道合一、分布自相似性、延伸速度快、水土流失的通道以及道路廊道狭窄。从景观生态理论与沟谷廊道治理目标相结合的观点出发,提出了优化整治的原则与治理措施,认为黄土丘陵区沟谷廊道的研究在生态环境治理和社会经济发展方面具有重要的研究价值。  相似文献   

PRESENT LANDFORMS, ACTIVE TECTONIC ZONES, DEEP STRUCTURES AND UPLIFT MECHANISMS OF THE LONGSHOUSHAN BLOCK ON THE NORTHERN MARGIN OF THE QINGHAI—TIBET PLATEAU     

Dong Zhiping  Zhang Jie 《地学前缘》2000,(Z1)

PRESENT LANDFORMS, ACTIVE TECTONIC ZONES, DEEP STRUCTURES AND UPLIFT MECHANISMS OF THE LONGSHOUSHAN BLOCK ON THE NORTHERN MARGIN OF THE QINGHAI—TIBET PLATEAU  相似文献