Ibex diggings in the Negev Desert highlands of Israel as microhabitats for annual plants. Soil salinity, location and digging depth affecting variety and density of plant species   总被引：1，自引：0，他引：1  

Yitzchak Gutterman 《Journal of Arid Environments》1997,37(4):665-681

About 400 Nubian ibex (Capra ibex nubiana) dig many hundreds of temporary night beds, approximately 80 cm × 110 cm and 15 cm deep, on slopes near the edges of the cliffs bordering the Zin valley. The beds are used according to the wind direction and the size of the ibex group, which depends on the ibex social behaviour during the year.The diggings are gradually abandoned and become important microhabitats for seed accumulation and germination, seedling development and annual plant establishment. These are influenced by soil salinity, slope direction and angle, digging depth, and the time since the diggings were abandoned. A greater variety of plant species and plant density were found in these diggings than upslope from the diggings.  相似文献   

Runoff Scaling in Large Rivers of the World     

Hugo A. Loiciga 《The Professional geographer》1997,49(3):356-364

Runoff and precipitation scaling with respect to drainage area is analyzed for large river basins of the world, those with mean annual runoff in excess of 10 k³/yr. The usefulness of the specific runoff (runoff per unit drainage area, m/yr) to categorize runoff scaling laws across the complete spectrum of climatic and hydrologic conditions is evaluated. It is found that (1) runoff scales with drainage are in those river basins with specific runoff in excess of 0.15 m/yr (r² = 0.88); (2) runoff scaling with drainage area shows remarkably high statistical correlation (r²= 0.97) in river basins with specific runoff equal to or larger than 1.0 m/yr; (3) runoff does not Inc.rease with Inc.reasing drainage area in river basins with specific runoff below 0.15 m/yr, where no discernible statistical association was found between runoff and drainage area; and (4) precipitation depth (m/yr) is inversely proportional to drainage area raised to a fractional exponent in river basins with specific runoff in excess of 0.15 m/yr.  相似文献   

天山北坡降水对河流水沙情势影响     

陈亚宁  李卫红 《山地学报》1997,(1)

以天山北坡头屯河流域为例，在对山区不同海拔的降水特征、侵蚀产沙情势以及河流水沙运移特点分析的基础上，详尽就山区降水对河流水沙情势的年际变化、年内变化以及月变化的影响进行了分析研究，并就降水对不同海拔的河流水沙情势的影响强度及相互关系作了探讨．  相似文献   

北极巴罗Elson湖过去450年气候与环境变化记录     

张青松  李元芳  杨惟理  王国  李栓科  侯书贵 《第四纪研究》1996,(3)

北极阿拉斯加巴罗地区Ｅｌｓｏｎ湖长６０ｃｍＡＢ—６７钻孔岩芯提供了过去４５０年连续的高分辨环境变化记录。综合分析２１０Ｐｂ测年、沉积物粒度、有机质、化学元素和微体古生物化石等资料，一致反映出巴罗地区过去４５０年的气候、环境变化过程存在如下３个阶段：１）大约１５４０～１７４０年，为低海面寒冷时期；２）１７４０～１８２７年，为气候转暖－海侵过渡时期；３）１８２７年至今，为继续海侵－气候波动变暖时期。其中１８００年前后和１９４０年前后，气温较高。１９２１～１９９３年巴罗的气温记录说明，北极地区气温不仅有明显的１０ａ和６０ａ周期变化，而且年平均温度变幅极大，达４．５℃。显示极地气候变化特别强烈并不反映大幅度升温。近２０年来的变暖趋势是１８２７年以来自然的气候波动变暖的继续。  相似文献   

乌鲁木齐河山区流域360年径流量的重建   总被引：15，自引：0，他引：15       下载免费PDF全文

李江风  袁玉江  由希尧 《第四纪研究》1997,17(2):36-43

本文利用在乌鲁木齐河山区流域所建立的树轮年表，重建了乌鲁木齐河山区流域３６０年上年７月～当年３月的平均径流量。校准方程的相关系数为０．６７０，交叉检验的误差缩减值达０．３６６。在重建的３６０年径流量的变化中，有４个偏丰期和３个偏枯期，第２，３两个偏丰期与乌鲁木齐河河源１号冰川的两次冰进期相对应。对重建径流量的丰枯频率分析发现，平水年份出现最多，偏枯水年份多于偏丰水年份约５．８％，特枯水年没有出现，特丰水年出现６次，约占１．７％。这表明３６０年来径流量变化基本上稳定。  相似文献   

试论温室效应对我国西部河川径流的影响   总被引：2，自引：1，他引：2  

赖祖铭 《冰川冻土》1997,19(1):10-16

大气中日益增多的温室气体使我国西部地区的气候近三四十年来出现了干暖化趋势，导致河川径流量明显减少。据统计，从５０年代后半期到８０年代，新疆地区的河种径流量减少了６．４％，西藏东南部的３条大河从６０年代到８０年代则平均减少了１３．２％，其减少量大于新疆，这主要是因为气温升高使冰雪融水增加，新疆的河流受到冰雪融水的补偿，虽然西藏东南部的河注也有冰川存在，甚至冰种覆盖面积远大于新疆一些内陆河流域，但那里  相似文献   

RILL EROSION PROCESS ON STEEP SLOPE LAND OF THE LOESS PLATEAU     

ZHENG Fenli  TANG Keli 《国际泥沙研究》1997,(1)

IntheLoessPlateau,alongtheslopelengthfromthetoptothebottom,soilerosionischaracterizedbyobviousverticalzonaldivision,thatis,sheeterosionzone,sheeterosionandrillerosionzone,rillerosionandshallowgullyerosionzoneandgullyerosionzone.Inthesheetandrillero..sionzone,rillerosionamounttakesup70%ofthetotalsoilloss[TANGKenetal.,1983,ZHENGFenlietal.,19871;intherillandshallowgullyerosionzone,rillerosionamountaccountsfor30--40%ofthetotalsoilloss.Sorillerosionisamajorerosionpatternonsteepslopeland.Riller…  相似文献   

树轮──流域径流变化的记录     

刘广深  戚长谋  林学钰 《吉林大学学报(地球科学版)》1997,(3)

根据树轮稳定碳同位素组成（δ１３Ｃｔ）序列可较灵敏地记录降水变化的事实，利用长白山红松树轮δ１３Ｃｔ序列与松花江年径流量之间的平行变化关系，重建了近２００年来松花江年径流量的变化：年径流量变化有明显的准２２年周期；１９００年之前，径流量在周期波动中呈上升趋势，１９００年之后，波动中呈下降趋势  相似文献   

Hydrological connectivity of soil pipes determined by ground‐penetrating radar tracer detection     

Joseph Holden 《地球表面变化过程与地形》2004,29(4):437-442

Soil pipes are common and important features of many catchments, particularly in semi‐arid and humid areas, and can contribute a large proportion of runoff to river systems. They may also signi?cantly in?uence catchment sediment and solute yield. However, there are often problems in ?nding and de?ning soil pipe networks which are located deep below the surface. Ground‐penetrating radar (GPR) has been used for non‐destructive identi?cation and mapping of soil pipes in blanket peat catchments. While GPR can identify subsurface cavities, it cannot alone determine hydrological connectivity between one cavity and another. This paper presents results from an experiment to test the ability of GPR to establish hydrological connectivity between pipes through use of a tracer solution. Sodium chloride was injected into pipe cavities previously detected by the radar. The GPR was placed downslope of the injection points and positioned on the ground directly above detected soil pipes. The resultant radargrams showed signi?cant changes in re?ectance from some cavities and no change from others. Pipe waters were sampled in order to check the radar results. Changes in electrical conductivity of the pipe water could be detected by the GPR, without data post‐processing, when background levels were increased by more than approximately twofold. It was thus possible to rapidly determine hydrological connectivity of soil pipes within dense pipe networks across hillslopes without ground disturbance. It was also possible to remotely measure travel times through pipe systems; the passing of the salt wave below the GPR produced an easily detectable signal on the radargram which required no post‐processing. The technique should allow remote sensing of water sources and sinks for soil pipes below the surface. The improved understanding of ?owpath connectivity will be important for understanding water delivery, solutional and particulate denudation, and hydrological and geomorphological model development. Copyright © 2004 John Wiley & Sons, Ltd.  相似文献   

近50 年海河流域径流的变化趋势研究   总被引：49，自引：0，他引：49       下载免费PDF全文

刘春蓁刘志雨  谢正辉 《应用气象学报》2004,15(4):385-393

该文用Mann-Kendall方法对近50年海河流域山区20个子流域的径流及降水的变化趋势进行了显著性检验, 结合降水, 径流及气温的年代距平值的同步分析以及径流对气候变化的敏感性研究结果, 对近50年海河流域径流的变化趋势, 提出了一个半定量分析的研究思路和方法。提出影响径流变化的三种类型:以气候暖干化为主, 人类活动为辅的径流显著衰减型;以人类活动为主, 气候暖干化为辅的径流显著衰减型;人类活动与气候变异都不明显, 径流无显著变化的类型。分析结果展示了气候、人类活动与水之间的相互作用。这种相互作用, 给径流的变化趋势分析和成因分析带来了复杂性与困难, 也给气候变化对水资源的影响研究提出了挑战。  相似文献