用隔绝法对极干旱区土壤水分来源的分析

 通常认为极干旱区土壤水分来源于降水、大气或凝结水,深埋区不存在潜水蒸发。然而通过使用拱棚法初步证明在极干旱深埋区存在潜水蒸发,而潜水是土壤水分的重要来源。为了进一步求证土壤水分来源,开挖200 cm×200 cm×200 cm的土坑,完全隔绝与下层土壤及四周的水分联系,回填后监测土壤10、30、50、100、150 cm的空气温湿度;同时设置与四周隔绝但底面联通的对照坑。27 d后都模拟25 mm降雨。监测发现模拟降雨前联通土壤的水分含量、空气相对湿度、绝对湿度都明显高于隔绝土壤。1 a后远离降雨时土壤水分的检测发现隔绝土壤水分含量低于联通对照,但因隔绝土壤处于潜水蒸发漫溢的相同气象环境,其湿度不会无限下降。隔绝对比实验反演证明深埋极干旱区存在潜水蒸发。     

陇东黄土高原土壤水分演变及其对气候变化的响应

以西峰为例,利用近45 a气象观测资料和近25 a的土壤水分观测资料,分析全球气候变暖背景下陇东主要气象要素及土壤水分的变化特征,探讨了气候变化对土壤水分的影响,以及影响土壤水分变化的主要气象因素。1993年以后,土壤水分以负距平为主,土壤干旱严重,0—50 cm和60—100 cm土层土壤水分含量在1997年和1995年降到最低值。春季是土壤水分减少最明显的季节,其中表层土壤水分对气候变化的响应更为明显,而夏秋季,较深层的水分变化更为明显。影响土壤水分的气象因子以降水、蒸发为主,气温通过影响蒸发间接产生影响。通过对土壤水分演变特征及其影响因子的分析,为进一步理解土壤水分条件的恶化原因,采取措施,合理利用气候资源,调整农业生态布局,恢复生态环境,积极应对气候变化提供决策方面的参考。     

黄土高原西部土壤蒸发实验研究

对兰州南北两山绿化区内的土壤蒸发状况,进行比较系统的试验研究。试验采用扰动土土柱内储存水分和人工模拟降雨的方法,对不覆盖/覆玉米秸秆/覆卵石三种处理的土壤蒸发情况进行了分析研究。结果表明,覆盖可有效地抑制土壤蒸发;不覆盖处理的土壤蒸发与土壤水分呈正相关,土壤水分越大,土壤表层保持湿润时间越长,蒸发量越大。在33 d的试验观测期内,三种处理的蒸发动态不同,覆盖处理的土壤蒸发过程没有集中的蒸发高峰期,而不覆盖处理的土壤蒸发过程主要集中在前10 d。土壤累计蒸发量与蒸发时间的回归分析说明,同一时间内各处理的累计蒸发量存在显著差异。     

苏打盐渍土土壤水分动态及其与浅层地下水的交换关系

以松嫩平原西部典型苏打盐渍土区为研究对象,以野外定位试验和室内模拟分析相结合,借助于分层土壤水分平衡模型,探讨苏打盐渍土壤水分运移的基本特征和规律,并分析其与浅层地下水之间的交换关系。研究结果表明,研究区内蒸降比较大,一般达到2:1以上,剖面土壤水分随蒸发、入渗过程呈现相应的转化;强烈地表蒸发作用下,地下水对上层土壤水分具有明显调控作用,土壤水分在50cm以下相对稳定,50cm以上受地表过程的影响变化较为显著。     

四川紫色雏形土的蒸发性及其与土壤结构性的关系

结合四川土壤基层分类 ,选取四川紫色雏形土的几个土系 ,对土壤的水分发性能及其与土壤结构性尤其是机械组成和微团聚体组成的相关关系分析发展 ,土壤水分蒸发具有明显的阶段性 ;土壤水分累积蒸发量与蒸发历时之间总体上符合乘幂方程 ;土壤蒸发速度与〈0 .0 0 1mm的颗粒含量呈明显相关关系 ,与 >0 .2 5mm的大团聚体含量呈明显负相关关系。     

德州水量平衡试验站观测试验资料——〈中国地理基础数据〉野外定位试验站卷(第一集)即将出版

六十年代初中国科学院地理研究所,根据国家科委下达的西北、华北水量平衡研究课题,以及自然地理学、水文物理学理论研究的需要,在山东水利厅、德州行署和德州市的帮助下,利用德州灌溉试验站原有条件,建立了德州水量平衡试验站,进行农田蒸发、作物蒸腾、水面蒸发、潜水蒸发与土壤水分的观测仪器与观测方法的研究,以探求蒸发机制及土壤水分运动规律。自1961年4月至1965年12月,共积累了观测试验资料78种。     

云南省元谋干热河谷的土壤抗旱力评价

根据土壤基本水分物理常数，将土壤水分蒸发划分为三个阶段，土壤水分累积蒸发量Ｑ与蒸发历时Ｔ具有：Ｑ＝ａＴ￣ｂ关系。不同土壤的蒸发能力不同，主要与土壤质地、结构等因素有关，同时不同土壤的抗旱力也有很大差异，土壤抗旱力由强至弱依次为：普通薄层土、变性燥红土、普通燥红土、表蚀干热的半干润变性土、表蚀燥红土。     

内陆绿洲灌溉农田SPAC系统土壤水分动态模拟研究

基于土壤水动力学原理,建立了内陆河流域山前农田绿洲SPAC系统土壤水分运移的子模型。应用该模型对土壤剖面含水率、农田棵间蒸发和叶面蒸腾量进行了模拟研究,并以实测值进行了验证。对相同种植与田间管理条件下的春小麦生长季田间土壤水分、土壤蒸发和叶面蒸腾量进行了预报,得到了较满意的结果。对模型主要参数土壤饱和导水率Ks、土表排水系数Wmax、净辐射Rn、风速Uz、饱和差D、作物叶面指数LAI进行了敏感性分析,得出这些参数对土壤水分运移的影响显著。应用该模型对西北干旱区内陆河流域山前绿洲灌溉农田的土壤水分均衡和作物根系吸水规律以及SPAC系统中土壤水分运移规律进行了模拟研究。     

流动沙丘干沙层厚度对土壤水分蒸发的影响

利用Micro-lysimeter对流动沙丘不同干沙层厚度下的土壤水分蒸发作了测定与分析,结果表明:当干沙层厚度发育达到5 cm以上时,流动沙丘干沙层厚度成为土壤水分蒸发的决定因素。随着干沙层厚度的增加,土壤蒸发量逐渐降低;各观测日的蒸发抑制率随着干沙层厚度的增大而增大;5 cm的干沙层对蒸发的抑制作用最大可达70.6%,30 cm的干沙层则最大可达92.38%;干沙层厚度与土壤蒸发量之间存在显著的线性关系。各气象因子以及湿沙层不同深度土壤体积含水率对土壤蒸发量的影响作用很小,相关分析均没有达到显著水平。     

黄土丘陵风沙区柽柳(Tamarix chinensis)林土壤水储量动态

对甘肃景泰不同种植密度的10年龄人工柽柳(Tamarix chinensis)林地,监测根周及行间土壤水分含量,并对监测资料进行量化分析。结果表明:(1)在垂直剖面上,根周土壤水分含量层次可分为蒸发层0~40cm、活跃层40~180cm和相对稳定层180~200cm;行间土壤水分含量层次可分为蒸发层0~40cm、活跃层40~120cm、相对稳定层120~200cm。(2)林地土壤水分主要靠天然降水补充,土壤水分储量年际变化随种植密度由高到低呈亏空-富余-亏空的变化趋势;综合考虑行距-土壤水分储量回归方程及冠积-行距回归方程,得出景泰地区合理种植密度为1 923株·hm-2。结果可为干旱区生态恢复和退耕还林提供科学依据。     

长沙城市土地扩张特征及影响因素

This research systematically analyses land-use map of Changsha city in different periods of time. The spatial form and structural evolution was analysed by studying indices such as city land-use structure proportion, expansion intensity, economic flexibility, population flexibility, changing compactness index and so on. The dynamic mechanism of urban land expansion has been discussed by integrating the regional social economy development situation and many aspects such as the physiographical surrounding, population and economic development, traffic infrastructure, planning and regional development tactic and system innovation. The research indicates that the urban land expansion speed and intensity have steadily increased in Changsha from 1949 to 2004. The expansion form has been from a single external expansion to a combination form of external and internal expansion, from a circular or linear continuous form to a blocky or agglomeration shape. Overall, the urban land expansion of Changsha city is a phasic, diversified and complex process. And no matter what the stage is, it is an organic system containing multiple speed, pattern and shape, which are driven by multiple impetuses. The dominant feature at different stages was highlighted be- cause of the balance and fluctuation between different forces, and the existing urban land border and shape have resulted from the joint efforts of these phasic forces.     

The influencing factors of urban land expansion in Changsha

This research systematically analyses land-use map of Changsha city in different periods of time. The spatial form and structural evolution was analysed by studying indices such as city land-use structure proportion, expansion intensity, economic flexibility, population flexibility, changing compactness index and so on. The dynamic mechanism of urban land expansion has been discussed by integrating the regional social economy development situation and many aspects such as the physiographical surrounding, population and eco-nomic development, traffic infrastructure, planning and regional development tactic and system innovation. The research indicates that the urban land expansion speed and intensity have steadily increased in Changsha from 1949 to 2004. The expansion form has been from a single external expansion to a combination form of external and internal expansion, from a circular or linear continuous form to a blocky or agglomeration shape. Overall, the urban land expansion of Changsha city is a phasic, diversified and complex process. And no matter what the stage is, it is an organic system containing multiple speed, pattern and shape, which are driven by multiple impetuses. The dominant feature at different stages was highlighted be-cause of the balance and fluctuation between different forces, and the existing urban land border and shape have resulted from the joint efforts of these phasic forces.     

Decadal variability in climate and glacier fluctuations on Mt Baker, Washington, USA

Climate variability in the Pacific basin has been attributed to large‐scale oceanic‐atmospheric modulations (e.g. the El Niño‐Southern Oscillation (ENSO)) that dominate the weather of adjacent land areas. The Pacific Decadal Oscillation (PDO) and north Pacific index are thought to be indicators of modulations and events in the northeast Pacific. In this study we find that variations in the PDO are reflected in the terminus position of glaciers on Mt Baker, in the northern Cascade Range, Washington. The initiation of retreat and advance phases of six glaciers persisted for 20–30 years, which relate to PDO regime shifts. The result of this study agrees with previous studies that link glacier mass balance changes to local precipitation anomalies and processes in the Pacific. However, the use of mass balance changes and glacier terminus variation for identification of regime shifts in climate indices is complicated by the lack of standardized measuring techniques, differing response times of individual glaciers to changes in climate, geographic and morphometric factors, and the use of assorted climate indices with different domains and time‐scales in the Pacific for comparison.     

Exploring Metropolitan Accessibility and Urban Structure

Location-based assessments of accessibility gauge the attraction of a place relative to other places. These approaches have been used extensively in models of commuting and urban structure. Even though locational accessibility measures are integral to such efforts, they may also be used to explore aspects of urban spatial structure. As such, this paper presents a GIS-based analysis of locational accessibility for a sample of U.S. metropolitan areas. Indices of accessibility based on spatial interaction models are developed for intraurban residential and employment locations. Results show that residential accessibility patterns are similar across cities, taking a concentric pattern where the central urban area is most attractive. However, employment accessibility varies more from city to city; moreover, the areas of highest employment accessibility tend to be decentralized within their respective regions. Overall, location-based accessibility indices are useful for exploring urban form, particularly with respect to issues of urban sprawl. Directions for future research are identified, including linking comparative urban accessibility measures to ongoing work on commuting, the jobs-housing balance, and urban structure.     

ANALYSIS OF POPULATION AGE BALANCE

Single-value indices of population age balance have proved useful. Coulson's index, although an improvement over other measures, is deficient when applied to middle-aged dominant populations and violates normality assumptions required by the technique for deriving the index. An alternative index of age balance was developed to provide more information and flexibility than other measures without losing their primary advantages.     

United States Census County Divisions As A Geographical Data Base

Single-value indices of population age balance have proved useful. Coulson's index, although an improvement over other measures, is deficient when applied to middle-aged dominant populations and violates normality assumptions required by the technique for deriving the index. An alternative index of age balance was developed to provide more information and flexibility than other measures without losing their primary advantages.     

一种基于面积紧凑度的二维空间形状指数及其应用

空间形状指数是重要的空间形态分析指标,目前应用较为广泛的基于边界紧凑度的一维空间形状指数在参照形状选择及一维测度应用等方面都存在局限性。针对一维空间形状指数的缺陷,定义一种基于面积紧凑度的二维空间形状指数,并以矩形为参照形状,讨论其计算方法。结合浙江省桐庐县标准农田立地条件评价的实例,比较分析两种维度空间形状指数的应用效果。结果表明,二维空间形状指数能够更精确地描述地物图斑相对于非紧凑参照形状的偏离程度,且在标准农田规划、建设等应用中更具实用价值。     

碳酸盐研究与其记录的环境变化

国际性的全球变化研究开展数十年来，针对不同的研究栽体建立了大量有效而实用的古气候环境代用指标，作者对应用较广，指示意义相对明确的各类栽体碳酸盐最近几年的研究工作进行了综述。综合国内外的研究成果表明，湖泊、黄土、洞穴、海洋沉积碳酸盐矿物及其微量元素、同住素分布特征普遍记录了全球或区域古气候环境演变历史，可以从中提取大量定量化的古气候参数。但以前的工作侧重过程研究，涉及机理的探索较少，特别是碳酸盐矿物及其元素、同位素分布特征变化的化学机理，不同影响因素的重要程度等方面的基础理论尚未完全理解清楚，是今后需要继续探索的工作。     

Effect of Uncertainties in Measured Variables on the Calculated Mass Balance of storglaciären

Detailed mass balance measurements have been carried out on Storglaciären since 1945, adhering to a fixed system of measurements since the 1960s. Using a geographical information system approach, the effect of parameters such as density conversion model, systematic snow probing error and ablation gradient calculation on the mass balance of the glacier can be investigated. It is evident that the measure of total mass balance of Storglaciären is not sensitive to variations in these parameters. This means that reasonable estimates of the mass balance of a glacier can be made with very little information, given that measurements are distributed over the glacier surface. However, the uncertainty that may result from varying the parameters is c . 0.1 m water equivalent. Hence, reporting mass balance to centimetre or even millimetre resolution is questionable. When considering mass balance measurements as input for flow models, for example, i.e. requiring a distributed balance, the detail necessary in the measurements becomes significantly greater. At this level careful attention must be made to all parameters entering the mass balance calculation. From this it seems evident that any measurements at intermediate complexity do not increase the accuracy of the mass balance in relation to the extra work required and that the choice of method determines the scientific problems to which the data is applicable.     

Testing the sensitivity of geomorphic indices in areas of low-rate active folding (eastern Betic Cordillera, Spain)

Active deformation structures have an incidence in topography that can be quantified by using geomorphic indices. Most of these indices have been checked in faulted regions with high-deformation rates. The application of several geomorphic indices (hypsometric curve analysis, normalized stream-length gradient, and valley width-to-valley height ratio) to the drainage network of the southern limb of the Sierra de Las Estancias antiform (Internal Zones, eastern Betic Cordillera), where low-rate active folding has been recognized, allows us to investigate the suitability of these indices to identify active structures in such a scenario. Hypsometric curves clearly identify regions with recent uplift and young topography, but they do not provide any constraint on the location of active folds. Local valley width-to-valley height index variations have been detected just coinciding whit the position of ENE–WSW active folds. Normalized stream-length gradient index serves to locate active folds in areas of hard rock substratum, but not in those areas with soft sediments (Neogene-Quaternary sedimentary basins). This is most likely due to the fact that in the basins erosion is much more intense than in the hard rock sectors. In view of these results, we consider that geomorphic indices constitute a valuable tool for identifying sectors affected by low-rate uplift related to active folding, with the best results obtained in hard rock areas.