首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到17条相似文献,搜索用时 109 毫秒
1.
青藏公路南段岛状冻土区内冻土环境变化   总被引:8,自引:4,他引:8  
王绍令  赵秀锋 《冰川冻土》1997,19(3):231-239
将90年代的勘探,钻孔测温和地面综合调查等实测资料与70年代对比,发现青藏公路南段状多年冻土区内的冻土退化和生态环境变化相当明显,表现为岛状多年冻土南界北移12km,多年冻土岛总面积减少7%,沼泽化湿地面积缩小约三分之一,沼泽化草罗向草原化草甸逐步转化,湖塘和洼地中的水生植物群落向湿。中生植物群落演替。草场退化亚,少数地段土地沙化,形成活动性砂丘,目前区内的生态环境正向劣势方面发展。  相似文献   

2.
高寒草甸是青藏高原面积最大的草地类型, 对全球生态环境的影响十分巨大。然而在外界干扰下, 使得本身就很脆弱的高寒草甸发生了不同程度的退化。为探究翻耕补播对土壤微生物的影响, 以疏勒河上游不同季节(4月、 6月、 9月)原生高寒草甸、 退化草甸和翻耕补播草甸土壤为对象, 研究了土壤可培养细菌数量的季节变化及其影响因素。结果表明: 研究区域可培养细菌数量介于4.3×106 ~ 4.5×107 CFU·g-1之间, 不同季节退化草甸与翻耕补播草甸土壤细菌数量均显著低于原生高寒草甸, 且不同类型高寒草甸生态系统下可培养细菌具有明显的季节差异: 原生高寒草甸生态系统下土壤细菌在6月生物量最高, 4月最低; 而退化草甸与翻耕补播草甸土壤细菌生物量并没有表现出明显的季节波动; 相关分析表明, 可培养细菌数量与土壤全氮、 植被盖度及土壤含水量存在极显著正相关关系。研究发现, 翻耕补播措施并没有恢复该区域微生物数量, 研究结果对于认识高寒草甸生态系统的退化成因, 判断恢复措施的有效性和合理性具有重要意义。  相似文献   

3.
为阐明青藏高原多年冻土区高寒草甸退化过程中土壤粒径分布(PSD)非均匀性和异质性的变化特征,在青藏高原长江源区,根据高寒草甸的退化梯度,选取了未退化区域、轻度退化区域、中度退化区域、重度退化区域和极重度退化区域,测定了高寒草甸退化过程中土壤的粒径分布、饱和导水率、孔隙度与有机质含量.运用多重分形理论,并结合土壤颗粒分布与土壤理化特性等参数的相关性进行分析,为高寒草甸退化对长江源高寒土壤性质变化的影响的定量研究提供一种精确的分析方法.结果表明:随着青藏高原多年冻土区高寒草甸退化程度的增加,土壤颗粒呈粗粒化趋势,多重分形参数中容量维数(D0)随之增大,表征PSD宽度随之增大;信息维数(D1)、信息维数/容量维数(D1/D0)、关联维数(D2)、奇异谱宽(Δα)可从不同角度反映的土壤PSD的非均匀性与局部异质性随着高寒草甸退化有先增大后减小的趋势,中度退化区域的土壤PSD不均匀性最大.研究发现,研究区土壤多重分形参数与细砂含量、土壤的孔隙度、有机质含量具有较明显的相关性.多重分形参数能准确描述高寒草甸退化过程中土壤粒径分布的细微差别,可作为反映土壤性质的潜在指标.  相似文献   

4.
黄河源区多年冻土退化及其环境反映   总被引:49,自引:17,他引:49  
基于黄河源区多年冻土退化引起的生态环境地质问题与效应的实际资料, 明确了多年冻土的生态环境功能和多年冻土退化引起的危害. 提出多年冻土退化使赋存于高寒草地和维系高寒草地生长发育的多年冻土表部的冻结层地下水水位持续下降或消失, 从而引发和加剧了高寒草地的"三化"(草地退化、沙漠化和盐渍化)和水环境变异, 是导致黄河源区占主导地位的高寒草甸失水向沙漠化草地和"黑土滩"型次生裸地退化的主要地质原因.  相似文献   

5.
青藏高原多年冻土区典型高寒草地生物量对气候变化的响应   总被引:12,自引:3,他引:12  
多年冻土区冻土生态系统对气候变化极其敏感,利用在长江黄河源区实测的高寒草甸和高寒草原植被生物量数据以及青藏高原降水、气温以及地温等的空间分布规律,建立了长江黄河源区高寒草甸与高寒草原等主要高寒生态系统地上与地下现存生物量对气候要素变化的多元回归模型.预测分析表明:如果未来10 a气温增加0.44℃.(10a)-1,在降水量不变的情况下,高寒草甸和高寒草原地上生物量分别递减2.7%和2.4%,如果同时降水量小幅度增加8 mm.(10a)-1,则地上生物量可基本保持现状水平略有减少;在气温增加2.2℃.(10a)-1,在降水量不变的情况下,高寒草甸和高寒草原地上生物量年分别平均减少达6.8%和4.6%,如果同期降水量增加12 mm.(10a)-1,高寒草甸地上生物量可基本维持现状水平略有增加,而高寒草原地上生物量则递增5.2%.高寒草原植被地上生物量对气候增暖的响应幅度显著小于高寒草甸,而对降水增加的响应程度大于高寒草甸.明确高寒草地植被生物量随气候变化的演变趋势,对于青藏高原生态环境保护和研究气候变化对青藏高原生态系统碳循环和河源区水循环的影响具有重要意义.  相似文献   

6.
多年冻土区冻土生态系统对气候变化极其敏感,利用在长江黄河源区实测的高寒草甸和高寒草原植被生物量数据以及青藏高原降水、气温以及地温等的空间分布规律,建立了长江黄河源区高寒草甸与高寒草原等主要高寒生态系统地上与地下现存生物量对气候要素变化的多元回归模型.预测分析表明:如果未来10 a气温增加0.44℃.(10a)^-1,在降水量不变的情况下,高寒草甸和高寒草原地上生物量分别递减2.7%和2.4%,如果同时降水量小幅度增加8 mm.(10a)^-1,则地上生物量可基本保持现状水平略有减少;在气温增加2.2℃.(10a)^-1,在降水量不变的情况下,高寒草甸和高寒草原地上生物量年分别平均减少达6.8%和4.6%,如果同期降水量增加12 mm.(10a)^-1,高寒草甸地上生物量可基本维持现状水平略有增加,而高寒草原地上生物量则递增5.2%.高寒草原植被地上生物量对气候增暖的响应幅度显著小于高寒草甸,而对降水增加的响应程度大于高寒草甸.明确高寒草地植被生物量随气候变化的演变趋势,对于青藏高原生态环境保护和研究气候变化对青藏高原生态系统碳循环和河源区水循环的影响具有重要意义.  相似文献   

7.
青藏高原典型寒冻土壤对高寒生态系统变化的响应   总被引:7,自引:5,他引:7  
高寒生态系统对全球变化非常敏感,以青藏高原腹地的长江黄河源区为研究区域,利用多期遥感TM数据和生态样带调查数据,提出生态综合指数方法.应用土壤结构、组成与水理特性等物理指标和土壤化学性质与养分含量指标,系统分析了青藏高原典型寒冻土壤如钙积寒性干旱土、简育寒性干旱土、草毡寒冻雏形土以及简育寒冻雏形土等对高寒生态系统变化的响应特征.结果表明:随着气候变化,主要高寒生态系统如高寒草甸、高寒草原以及高寒沼泽草甸等显著退化,寒冻土壤表层呈现明显粗粝化,草毡寒冻雏形土以及简育寒冻雏形土表层土壤细粒物质流失38.7%,土壤孔隙度和容重增加;高寒草甸土壤表层饱和导水率随综合生态指标值降低而急剧增大,当植被覆盖度<50%以后,土壤表层水分集聚现象不再存在,高寒草原土壤饱和导水率变化不明显;高寒草甸与高寒草原土壤的有机质和全氮含量均随生态指数减少而分别呈现抛物线和指数曲线形式减少.随着气候变暖和人类活动干扰的加剧,高寒草地生态系统变化将可能导致寒冻土壤环境持续退化并对高原草地碳循环产生重要的影响.  相似文献   

8.
面向未来的海面变化研究   总被引:3,自引:0,他引:3  
谢志仁  夏胜俊 《地学前缘》1997,4(2):235-246
长期以来以地质时期海面变化过程等理论性研究为主要方向的海面变化研究经过70年代在观念、方法和资料积累方面的突破,自80年代初期以来进入了以“面向未来”为基调的成熟发展的新阶段,出现了一大批关于未来海面变化幅度其影响和对策的研究成果,形成了较为完整的研究体系。90年代以来的几年间,民办海面研究的活跃领域是地质历史时期(LGM,5e等阶段)的海面实况、极地冰原对气候变化的反应、海面控制原理、海面模型以  相似文献   

9.
中国草地植被地上和地下生物量的关系分析   总被引:3,自引:0,他引:3  
草地生物量大部分集中在地下,地下生物量对于估算草地生态系统碳储量及其碳固持效应都至关重要。由于草地地下生物量数据缺乏,利用地下与地上的根冠比(R/S)或者地下与地上生物量的关系对草地地下生物量进行估算,是目前最常用的方法。本文在综述草地生物量研究进展的同时,利用2004~2010年已发表文献的草地生物量数据对中国不同类型草地的根冠比进行了探索,同时分析了不同类型草地的地上与地下生物量的相关关系(高寒草甸、高寒草原、山地草甸、温性草甸草原、温性草原和温性荒漠草原)。分析结果表明:不同类型草地的根冠比存在显著差异(F=3.524,p0.01);进一步分析发现,山地草甸的根冠比显著低于其他类型草地(p0.01),R/S较大的草地类型为温性草甸草原和温性荒漠草原,均值分别为7.0和6.8。对地上与地下生物量相关关系的分析表明,3种类型草地的地上与地下生物量存在幂函数相关关系,即高寒草原(R~2=0.67)温性荒漠草原(R~2=0.36)高寒草甸(R~2=0.13),其他3种类型草地几乎不存在地上与地下生物量的相关关系。这为以后估算地下生物量提供依据,即地下生物量估算应该综合考虑根冠比和地下与地上生物量关系。  相似文献   

10.
2000-2015年祁连山植被变化分析   总被引:2,自引:1,他引:1  
植被变化对区域生态系统稳定和生态环境变化有着重要的影响.基于MOD13A3数据,建立了2000-2015年祁连山地区植被覆盖时空数据集,结合DEM和土地覆盖分类数据,分析了祁连山地区植被时空分布格局及变化特征,并利用同期气象数据探讨其对气候变化的响应.结果表明:祁连山植被呈东多西少的分布格局,其空间分布与降水空间分布一致;2000年以来祁连山地区灌丛和高寒稀疏草甸先增后减,山地森林草原和高寒草甸增加;整体上祁连山植被覆盖有转好趋势,这与区域暖湿化有关.  相似文献   

11.
Based on three phases of satellite-image data and field investigation results collected between 1976 and 1996, climate changes and intensity of human activity were studied for the time period to investigate the causes responsible for the region's environmental changes. The results show that, compared with the data for the 1970s, the eco-environment in the source region of the Yellow River degraded markedly from the 1980s to the 1990s. Degradation was most prominent from the mid-1990s onward, with significant degradation of high-cold grassland and high-cold meadow vegetation, and also a rapid expansion of desertification. The area of degraded vegetation increased from 24.5% in the 1980s to 34.5% of total grassland and high-cold meadow in the 1990s. The rate of land desertification increased from 3.96% in the 1980s to 34.72% in the 1990s. The main reasons for these changes include the intensity of overgrazing (which was very high), and the climate in this region which is becoming drier and warmer, resulting in a gradual degradation of the permafrost.  相似文献   

12.
In the source regions of the Yangtze and Yellow Rivers of China, glaciers, frozen ground, the hydrological system, and alpine vegetation have changed over the past decades years. Climatic causes of these variations have been analyzed using mean monthly air temperature and monthly precipitation between 1956 and 2000, and monthly evaporation from φ20 evaporation pans between 1961 and 1996. In the source region of the Yangtze River, lower temperature and plentiful precipitation during the 1960s and continuing into the early 1980s triggered a glacier advance that culminated in the early 1990s, while a robust temperature increase and precipitation decrease since 1986 has forced glaciers to retreat rapidly since 1995. Permafrost degradation is another consequence of the climatic warming. The variations in the hydrological system and alpine vegetation are controlled mainly by the climate during the warm season. Warmer and drier summer climate is the major cause of a degradation of the vegetation, desiccation of the high-cold marshland, a decrease in the areas and numbers of lakes and rivers in the middle and north source regions of the Yangtze and Yellow Rivers, and a reduction in surface runoff in the source region of the Yangtze River for the last 20 years. The causes of eco-environmental change in Dari area, near the outlet from the source area of the Yellow River, are different from those elsewhere in the study area. A noticeable reduction in runoff in the source region of the Yellow River and degradation of alpine vegetation in Dari area are closely related to the permafrost degradation resulting from climate warming.  相似文献   

13.
青藏高原高寒区草地生态环境系统退化研究   总被引:32,自引:6,他引:32  
青藏高原高寒地区的草地生态环境是高原生态环境的重要组成部分.近几十年来,在人类活动的强烈干扰和自然环境变化的影响下,高寒草地生态环境严重退化.在退化草地选取典型样地,调查研究了草地退化后土壤水文过程、土壤结构、植被状况等的变化.结果表明:高原高寒地区草场退化以后,土壤水文过程都发生改变,植被退化越严重土壤含水量变化越强烈、土壤入渗过程越快.退化草地的植被群落演替变化明显,优势种群退化严重,植物个体出现了小型化现象.水土流失日趋严重,土壤贫瘠化、沙化、荒漠化增强,鼠虫害等自然灾害频繁.  相似文献   

14.
长江源区高寒生态与气候变化对河流径流过程的影响分析   总被引:19,自引:5,他引:19  
近40 a来长江源区气候变化剧烈,是青藏高原增温最为显著的地区之一,高寒生态系统与冻土环境不断退化.采用多因素逐次甄别方法与半经验理论方法相结合,基于多年冻土的不同植被覆盖降水-径流观测场观测试验结果,分析了长江源区气候-植被-冻土耦合系统中各要素变化对河川径流的不同影响.结果表明:近40 a来长江源区河川径流呈持续递减趋势,年均径流量减少了15.2%,频率>20%的径流量均显著减少,而>550 m3.s-1的稀遇洪水流量发生频率增加;气候变化与高寒草甸覆盖变化对源区径流变化的影响较大,分别占5.8%和5.5%;气候与植被覆盖变化对径流的显著影响是与冻土耦合作用的结果,但冻土环境与冰川变化对径流的贡献尚不能准确评价.高寒沼泽湿地和高寒草甸生态系统对于源区河川径流的形成与稳定起到关键作用,这两类生态系统的显著退化是驱动河川径流过程中变差增大、降水-径流系数减少以及洪水频率增加的主要原因.保护源区高寒草甸与独特的高寒湿地生态,对于维护源区水涵养功能和流域水安全意义重大.  相似文献   

15.
An analysis, over historical times, of the influence of natural factors such as climate, geological activity, existing landforms, and the activity of aeolian sands on the desertification of oases and other lands in the Heihe River basin of northwestern China revealed that desertification occurred more or less quickly according to whether the prevailing climate was cold or warm, respectively. In the 1990s, the area of desertified lands in the lower reaches of the Heihe River (Ejin region) was 29.1% greater than in the mid 1980s. However, the rate of desertification in the middle reaches of the Heihe River basin was relatively slower, only 9.4% from 1949 to 1990 (or 0.27% per year). Since 1990, the rate of desertification has been stable. By 2000, the total area of land desertification in the mid to lower reaches of the Heihe River basin was 13,508.4 km2, or 11.8% of the region monitored. Of the total land desertification area, the regions of Linze, Gaotai, Sunan, Jiuquan, Jia Yuguan, and Jinta accounted for 1.70, 1.71, 1.43, 0.85, 0.28, and 9.39%, respectively, whereas the Ejin region’s 11,434.64 km2 accounted for 84.65%, indicating that land desertification in the lower Heihe River basin was particularly severe. The causes responsible for the occurrence and development of land desertification in the Heihe River basin were analyzed.  相似文献   

16.
The regional hydrology and ecosystems of the Hexi Corridor region of northwestern China have changed over the last half century under the driving force of intense human activity and regional climate changes. Streamflow issuing from mountains in the eastern section of the Corridor by way of the Shiyang River has decreased significantly. Annual mountain outflow from the Heihe and Shule Rivers in the central and western portions of the Corridor, respectively, have tended to increase; however, their downstream discharge has decreased sharply. These lower reaches clearly display anthropogenic hydrological features. Water salinization and pollution have worsened. Presently, up to 208 km of river courses exhibit the poorest water pollution grades of IV and V. Overall, the forested area in the south Qilian Mountain region has decreased by 16.5% in the last 50 years, but has recently begun to show a gradual increase. However, natural desert forests in the northern portion of the Hexi Corridor have continued in a trend of degradation and rapid disappearance, with 3431 km2 lost in Minqin and Ejin counties alone. Grasslands have been progressively degraded and their area decreased such that grasslands in the Hexi Corridor region only cover 46.86% of their former area. Desertification has been exacerbated and the grasslands' stock capacity reduced. In the Hexi Corridor region desertification has proceeded swiftly over the last 50 years, reaching, in the early 1980s, a maximum annual rate of 2.15% of total initial grassland area. However, from the late 1980s through the 1990s their desertification rate has dropped significantly. A unified watershed-scale plan for water use and management in different regions of the Hexi Corridor, considering water demands for economic development as well as ecosystem maintenance and remediation, must be implemented. The improved and ultimate sustainability of regional development for the Hexi Corridor is linked to following ecological criteria in exploiting land resources, and to systematically protect ecosystem function, allowing for sound ecosystem development.  相似文献   

17.
长江黄河源区覆被变化下降水的产流产沙效应研究   总被引:4,自引:2,他引:4       下载免费PDF全文
在长江和黄河源区的左冒西孔曲和纳通河、垮热洼尔玛河流域的不同植被覆盖下建立了天然径流观测场,利用观测天然降水和人工模拟降水,初步研究了江河源区不同植被覆盖下降水的产流产沙效应。结果表明,长江黄河源区的3个小流域内,在典型高寒草甸草地30°坡面上,退化较为严重的30%覆盖度以下的场地内,地表径流产出量明显大于覆盖度较好的95%、92%和68%场地,同时产沙量显著高于这3个场地,其平均单次降水形成的泥沙量是这三种盖度的2~4倍,由此造成地表侵蚀量平均为这3种盖度的3~10倍。通过对几次典型的降水形态的分析,在长江黄河源区高寒草甸草地的坡面上,不但降水量影响着产流产沙量,降水形态也影响着产流产沙量,降雨仍是引起水土流失的主要降水形态,在降水量相同的条件下,降雪可比降雨和雨加雪增加产流量2.1~3.5倍,可比降雨减少泥沙侵蚀45.4%~80.3%。人工模拟结果表明:对于覆盖度为5%和30%的强度退化草地,次降水量在3.5 mm时,就形成了较为明显的径流和产沙效应,当次降雨量达到7 mm,降雨持续时间15 min,5 m2场地内就会形成1 400 mL以上的径流量;在地表土壤含水量(FDR测0~5 cm平均含水量为36.7%)较高的情况下,次降雨量达4mm,降雨强度超过0.4 mm/min,在5 m2场地内历时5 min就能形成1 060 mL的地表径流,每100 mL径流中含泥沙高达1.6 g。这一试验结果在长江黄河源区3个不同的河源小流域是一致的。  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号