青海湖流域植被盖度时空变化研究     

高黎明  张乐乐 《地球信息科学学报》2019,21(9):1318-1329

高寒区植被变化一直是气候和生态学领域关注的热点问题。本研究基于MODIS NDVI数据计算的植被覆盖度数据和高分辨率气象数据,分析了青海湖流域2001-2017年植被覆盖度分布格局及动态变化,探讨了其对气候变化、人类活动和冻土退化的响应。结果表明：① 近十几年青海湖流域植被覆盖度整体表现为增加趋势,不同植被类型增幅存在差异性,草地增幅最大,达到6.1%/10a,其它植被类型增幅在2%~3%/10a之间;② 流域局部地区仍存在植被退化现象,研究期植被退化面积表现为先增加后减小的变化趋势。2006-2011年重度退化区集中在青海湖东岸,2011-2017年重度退化区集中在流域的西北部,这些区域是青海湖流域荒漠分布区,植被覆盖度较低,是今后生态恢复需重点关注的区域;③ 气候变化是流域植被覆盖度变化的主导因素,气候变化对青海湖流域主要植被类型覆盖度变化的贡献率为84.21%,对草原、草甸和灌丛植被覆盖度变化的贡献率分别为81.84%、87.47%和75.96%;④ 人类活动对流域主要植被类型覆盖度变化的贡献率为15.79%,对草原、草甸和灌丛植被覆盖度变化的贡献率分别为18.16%、12.53%和24.04%,环青海湖地区人类活动对植被恢复有促进效应,在青海湖流域北部部分地区人类活动的破坏力度仍大于建设力度;⑤ 冻土退化对青海湖流域草甸和灌丛植被覆盖度变化影响很小,主要影响草原植被覆盖度变化,冻土退化造成草原植被覆盖度增长速率减小了1.2%/10a。  相似文献   

Revisiting Sustainable Development of Dry Valleys in Hengduan Mountains Region   总被引：5，自引：1，他引：4  

TANGYa XIEJiasui SUNHui 《山地科学学报》2004,1(1):38-45

Dry valleys are a striking geographic landscape in Hengduan Mountains Region and are characterized by low rainfall, desert type of vegetation and fragile environment. Past efforts and resources have been concentrated mainly on rehabilitation of degraded ecosystem and fragile environment, particularly reforestation, while socio-economic development has been largely overlooked. Despite successes in pocket areas, the overall trend of unsustainability and environmental deterioration are continuing. It is important to understand that uplift of the Tibetan Plateau is the root cause of development of dry valleys, and development and formation of dry valleys is a natural process. Human intervention has played a secondary role in development of dry valleys and degradation of dry valleys though human intervention in many cases has speeded up environmental degradation of the dry valleys. It is important to understand that dry valleys are climatic enclaves and an integrated approach that combines rehabilitation of degraded ecosystems and socio-economic development should be adopted if the overall goal of sustainable development of dry valleys is to be achieved. Promotion of niche-based cash crops, rural energy including hydropower, solar energy, biogas and fuelwood plantation is recommended as the priority activities.  相似文献   

成都及附近地区旅游气候资源研究   总被引：9，自引：0，他引：9  

胡毅  朱克云  江毓忠 《成都信息工程学院学报》2001,16(4):237-242

通过对成都及附近等7个地区多年气候资源及人体舒适指数进行分级比较，得出了7个地区的人体舒适指数的时间分布特征及对当地旅游的影响。  相似文献   

A high‐resolution pollen and geochemical analysis of late Holocene human impact and vegetation history in southern Cumbria,England     

Paul M. V. Coombes  Richard C. Chiverrell  Keith E. Barber 《第四纪科学杂志》2009,24(3):224-236

The historic era, which in Cumbria begins with the Roman invasion of AD 71, is a frequently neglected period in palaeoecological research, but its study can bring benefits in improving knowledge of landscape history and in understanding the significance and limitations of palaeoecological records. Pollen and geochemical data are presented for late Holocene records from Deer Dyke and Hulleter Mosses in southern Cumbria. The records show initially low levels of anthropogenic impact, followed by a phase of forest clearance and mixed agriculture from the 7th to 11th centuries AD. The timing of these clearances suggests that they were initially Anglo‐Saxon in origin, rather than Norse. Further clearances in the 16th century AD are interpreted as a response to monastic dissolution and late Tudor population pressures; the landscapes reached their contemporary form following extensive clearances in the 17th century AD. Silicon and titanium concentrations at Deer Dyke Moss were used to reconstruct past levels of atmospheric dust loading, which is broadly related to soil erosion. Geochemical influx was found to peak during periods of landscape transition rather than from established land use. This relationship with pollen data is thought to reflect the predominantly low levels of anthropogenic impact in the region, which changes as substantial woodland clearances during the 16th century AD and continuous land use pressure since then have greatly increased the supply of airborne dust. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Multiple bipolar structure of normal magnetic field at the magnetopause     

T Chen  Z.X LiuX.X Zhang 《Planetary and Space Science》2003,51(6):381-386

We describe how a local plasma structure can be changed by a transverse shear flow using numerical simulation to investigate the disturbance process near the magnetopause. The results show that magnetic field lines are bent by transverse shear flow disturbance near the current sheet region. There are multiple bipolar structures of the normal magnetic field in the numerical simulation. We term this new feature as K-point magnetic reconnection, realistic for discussing space observations.  相似文献   

Coupled and complex: Human-environment interaction in the Greater Yellowstone Ecosystem, USA     

David Bennett  David McGinnis 《Geoforum》2008,39(2):833-845

Complexity theory has received considerable attention over the past decade from a wide variety of disciplines. Some who write on this topic suggest that complexity theory will lead to a unifying understanding of complex phenomena; others dismiss it as a passing and disruptive fad. We suggest that for the analysis of coupled natural/human systems, the truth emerges from the middle ground. As an approach focused as much on the connections among system elements as the elements themselves, we argue that complexity theory provides a useful conceptual framework for the study of coupled natural/human systems. It is, if nothing else, a framework that leads us to ask interesting questions about, for example, sustainability, resilience, threshold events, and predictability.In this paper we attempt to demystify the ongoing discussions on complexity theory by linking its evocative and overloaded terminology to real-world processes. We illustrate how a shift in focus from system elements to connections among elements can lead to meaningful insight into human-environment interactions that might otherwise be overlooked. We ground our discussion in ongoing interdisciplinary research surrounding Yellowstone National Park’s northern elk winter range; a tightly coupled natural/human system that has been the center of debate, conflict, and compromise for more than 135 years.  相似文献   

Response of the barrier island coastal region of southwestern Nigeria to climate and non-climate forcing     

IB Danladi  M Gül  E Ateş 《African Journal of Marine Science》2020,42(1):43-51

Despite threats emanating from the influence of climate and non-climate forcing on the barrier island coastal region of southwestern Nigeria, the extent of the coastal erosion is poorly understood. We report evidence of coastal erosion and sediment accumulation in the region over a 34-year period (1973–2017), using Landsat imagery at intervals of approximately six years. Landsat image corrections and various water-extraction algorithms were used to systematically delineate coastal erosion and accumulation in the area. The region was subdivided into western and eastern subregions separated by Lagos Harbour. In the west, erosion took place during the periods 1973–1979, 1979–1984, 1990–1999 and 2005–2011, whereas in the east, erosion occurred during 1973–1979, 1990–1999 and 1999–2005. Coastal sediment accumulation occurred in the east during 1979–1984, 1984–1990, 2005–2011 and 2011–2017, whereas gains in the west occurred during 1984–1990, 1999–2005 and 2011–2017. The study revealed substantial net erosion of 1 228.1 ha in the region as a whole, over the full period. Sediment accumulation accompanying the coastal erosion appears to be linked to longshore drift. Erosion between 1973 and 2011 was probably attributable to climate change (storms and tidal conditions), longshore drift, the inflow and outflow of water at Lagos Harbour, coastal morphology and, possibly, human impacts. However, the coastal changes between 2011 and 2017 were more obviously associated with human activities, such as development of the Eko Atlantic construction project. Coastal surveillance, together with the use of environmentally sensitive protective measures, could possibly help to reduce coastal erosion in the region. Careful coastal management practices, including artificial nourishing and the installation of resilient structures (e.g. seawalls), should be undertaken to protect human settlements that are already at risk from sea-level rise.  相似文献   

黄河三角洲造陆速率对夏季风强度变化和人类活动的响应     

许炯心 《海洋学报》2007,29(5):88-94

以夏季风强度指数和年均气温作为反映气候变化的指数,以人类净引水量和流域水土保持面积作为反映人类活动变化的指标,并以黄河流域为例,研究了三角洲造陆对气候变化和人类活动的响应.研究表明,夏季风强度指数的变化可分为三个阶段:(1)在1951~1963年夏季风强度指数呈持续增强的变化趋势;(2)在1963~1965年夏季风强度指数呈突变式减弱;(3)在1966~2000年夏季风强度指数保持在较低的水平上,且呈缓慢减弱的趋势.年降水量变化与夏季风强度指数有同步关系.从1950到1970年的年均温度在波动中略呈降低趋势,然而从1970年开始年均温度在波动中具有持续上升的趋势.气候变化会导致入海泥沙通量的变化,并可能进一步导致三角洲造陆速率的变化.黄河三角洲造陆速率、入海泥沙通量在1952~1964年均呈增大的趋势,1964年后则呈减小的趋势,在总体上与夏季风强度指数的变化趋势相同.除了气候变化以外,流域水土保持和引水对三角洲造陆也有影响.多元回归分析表明,三角洲造陆速率随夏季风强度指数的减弱而减小,随年气温的升高而减小,随梯田林草面积的增加而减小,随年净引水量的增加而减小,同时还表明,夏季风强度指数、年均气温、水土保持措施面积和人类净引水量对三角洲造陆速率变化的贡献率分别为34.94%,3.80%,53.82%和7.44%.表示气候变化的两个变量的贡献率之和为38.7%,说明气候变化对黄河三角洲造陆过程的影响是不容忽视的.  相似文献   

中国海岸湿地退化压力因素的综合分析   总被引：39，自引：1，他引：39       下载免费PDF全文

谷东起  赵晓涛  夏东兴 《海洋学报》2003,25(1):78-85

对我国海岸湿地类型、特点和分布进行了论述.通过分析指出围垦、城市与港口开发、污染、海岸侵蚀、油气资源开发、生物资源过度利用和海平面上升等环境压力因素是造成湿地退化的主要原因.综合矩阵因子分析表明,不同的海岸湿地类型所承受的环境压力和所遭受的环境退化程度是不同的,其中三角洲、海岸潟湖、砂质海岸、珊瑚礁、淤泥质海岸、滨岸沼泽和红树林等湿地类型遭受的环境压力最大,环境退化也最严重;指出了人为因素是造成海岸湿地环境退化的主要原因.  相似文献   

中尺度地形扰动的非线性问题半解析解     

陈显尧  巢纪平 《海洋科学进展》2003,21(4):369-376

将大气和海洋中f-平面上中尺度地形的扰动问题统一起来作为一个地球物理流体力学问题，应用涡度、能量和经圈动量守恒条件，将原来高度非线性方程变成一个二阶椭园型非线性方程，用数值模拟方法分析了大气中的过山运动和海洋中的沿岸上升流，给出了与观测接近的模拟结果以及运动过程对内部物理参数和外界条件的敏感性分析。所提方法可供进一步的动力学分析和数值研究参考。  相似文献