The role of cryptogams in runoff and erosion control on bariland in the Nepal Middle Hills of the Southern Himalaya     

Steve Gaskin  Rita Gardner 《地球表面变化过程与地形》2001,26(12):1303-1315

Cryptogams are communities of non-vascular plants that live on the soil surface. Numerous functions have been attributed to these crusts, including changes in soil fertility and nutrient status, soil hydrology and soil erosion. Most significant for this paper is the reported benefit of cryptogams in reducing soil erosion by water in semi-arid areas. However, to date there have been few attempts to understand the soil conservation value of cryptogams in subsistence agricultural systems or in humid mountain environments. This paper investigates the potential of cryptogams in soil erosion by water on agricultural hillslope terraces (bariland) in the Nepal Middle Hills of the southern monsoonal Himalaya. The research is significant because the loss of fertile topsoil is considered by some to be the biggest threat to the livelihoods of subsistence farmers in the area in the medium and long term. The current study was conducted in the field between two of the weeding events that take place under maize cover, grown in the traditional manner. Three groundcover types which represented (i) maize only (types A), (ii) maize and weed cover (types B), and (iii) maize and cryptogam cover (types C) were monitored utilizing multiple microerosion plots. Measurements of runoff and soil loss data were collected sequentially on a storm-by-storm basis throughout the monitored period from 24 July 1997 to 29 August 1997. Measurements of infiltration rates were also taken on each of the groundcover types at selected times. Results collected from the erosion plots demonstrate that runoff and soil losses over distances of <2 m can be significantly reduced by up to 50 per cent with cryptogam cover, compared to maize-only canopies. Mean runoff for all storm events sampled from plot types A, B and C were 3·4 l m⁻², 1·6 l m⁻² and 1·5 l m⁻² respectively. For soil loss, the results were 21·7 g m⁻², 11·3 g m⁻² and 10·2 g m⁻² respectively. Therefore, cryptogams would appear to offer a similar degree of protection to the soil surface from runoff and raindrop erosion, to that afforded by weed cover. Weed and cryptogam covers protect the soil surface from rainfall kinetic energies and work to preserve surface microtopographies, depressional storage and surface water detention. Terminal infiltration rates taken at the end of the monitored period showed that well developed maize- and cryptogam-covered soil surfaces (types C) have a mean terminal infiltration rate of 35·0 mm h⁻¹ compared to 44·5 mm h⁻¹ for comparable maize- and weed-covered soil surfaces (types B), and 15·5 mm h⁻¹ for maize-only soil surfaces (types A). These results show that cryptogams and weeds also have relatively higher infiltration rates than comparable maize-only covered plots, devoid of groundcover. The findings in this study may have implications for traditional weed management practices used by local hill farmers, which often destroy cryptogam soil coatings two to three times during the maize growing period. However, further work needs to be done to ascertain farmers' understandings of cryptogams. It is hoped that conservationists will benefit from incorporating cryptogams into the design of future soil erosion studies relating to development programmes. Copyright © 2001 John Wiley & Sons, Ltd.  相似文献   

Non-metamorphosed autochthonous Kuncha-Naudanda-Heklang Formations and their differences from those of the Kuncha nappe: A multichronological approach     

Wataru Kobayashi  Harutaka Sakai  Hideki Iwano  Tohru Danhara  Takafumi Hirata 《Island Arc》2021,30(1):e12396

Non-metamorphosed, autochthonous Lesser Himalayan sediments (LHS), which are correlated to the Kuncha and Naudanda Formations, were found in a narrow belt between the Main Boundary Thrust and the Lesser Himalayan Thrust at the base of the Kuncha nappe in southeastern Nepal. The autochthonous Naudanda Formation is comprised of cross-bedded and rippled orthoquartzite and yielded a maximum depositional age of 1795.1 Ma ±5.1 Ma using detrital zircons. Low-grade metamorphosed quartzite in the Kuncha nappe yielded a maximum depositional age of 1867.4 Ma ±3.4 Ma, although it is totally recrystallized. These ages and age distribution patterns of detrital zircon grains indicate that the meta-quartzite of the nappe is originally Naudanda Formation. A zircon fission-track age of the autochthonous Naudanda Formation shows partially annealed age of 864 Ma ±56 Ma, in contrast, that of the Kuncha nappe shows a totally annealed age of 11.9 Ma ±1.6 Ma. These results suggest that the autochthonous LHS have never undergone metamorphism during the Himalayan orogeny. We also discovered a non-metamorphosed Heklang Formation that rests on the Naudanda Formation, and designated it as a sub-type section on the basis of detailed lithostratigraphic study. It is characterized by black and light green slate with dolerite sills and ill-sorted quartzose sandstone, and correlated to the metamorphosed Dandagaon Phyllites in the Kathmandu area. Non-metamorphosed autochthonous formations distributed to the south of the nappe front suggest that they escaped from thermal metamorphism by hot nappe.  相似文献   

Exploring social barriers to adaptation: Insights from Western Nepal   总被引：4，自引：0，他引：4  

Lindsey Jones  Emily Boyd 《Global Environmental Change》2011,21(4):1262-1274

As the challenges and opportunities posed by climate change become increasingly apparent, the need for facilitating successful adaptation and enhancing adaptive capacity within the context of sustainable development is clear. With adaptation high on the agenda, the notion of limits and barriers to adaptation has recently received much attention within both academic and policymaking spheres. While emerging literature has been quick to depict limits and barriers in terms of natural, financial, or technologic processes, there is a clear shortfall in acknowledging social barriers to adaptation. It is against such a backdrop that this paper sets out to expose and explore some of the underlying features of social barriers to adaptation, drawing on insights from two case studies in the Western Nepal. This paper exposes the significant role of cognitive, normative and institutional factors in both influencing and prescribing adaptation. It explores how restrictive social environments can limit adaptation actions and influence adaptive capacity at the local level, particularly for the marginalised and socially excluded. The findings suggest a need for greater recognition of the diversity and complexity of social barriers, strategic planning and incorporation at national and local levels, as well as an emphasis on tackling the underlying drivers of vulnerability and social exclusion.  相似文献   

2015年西藏定日M_W5.7地震震源参数估计和静态应力触发研究     

方金玲  赵斌  余建胜  陈威 《大地测量与地球动力学》2022,42(9):964-970

采用InSAR形变监测资料计算2015年西藏定日M_W5.7地震同震形变场,反演发震断层几何参数和滑动分布。在此基础上,研究尼泊尔M_W7.8主震对定日地震的静态库仑应力触发影响。综合分析地震滑动机制和构造特征,认为定日断层为西倾隐伏断层。反演结果表明,地震破裂相对集中,主要深度在6~9 km,破裂以正断滑动为主。发震断层走向约178°,倾角约 48°,破裂区长约5 km,宽约5 km,最大滑动量约0.2 m,释放的地震矩约3.7×10¹⁷ N·m,对应矩震级M_W5.6。尼泊尔主震同震库仑应力在定日地震震源处约为0.2 bar,造成藏南申扎-定结拉张地堑应变加载。  相似文献   

An assessment of conditions before and after the 1998 Tam Pokhari outburst in the Nepal Himalaya and an evaluation of the future outburst hazard          下载免费PDF全文

Damodar Lamsal  Takanobu Sawagaki  Teiji Watanabe  Alton C. Byers  Daene C. McKinney 《水文研究》2016,30(5):676-691

On 3 September 1998, a glacial lake outburst flood (GLOF) that originated from Tam Pokhari occurred in the Hinku valley of the eastern Nepal Himalaya. This study analyses the lake's geomorphic and hydrologic conditions prior to the outburst, and evaluates the conditions that could contribute to a future flood through photogrammetric techniques. We processed high‐resolution Corona KH‐4A (2.7 m) and ALOS PRISM (2.5 m) stereo‐images taken before and after the GLOF event, and produced detailed topographic maps (2‐m contour interval) and DEMs (5 m × 5 m). We (re‐) constructed lake water surfaces before (4410 ± 5 m) and after (4356 ± 5 m) the outburst, and reliably estimated the lake water surface lowering (54 ± 5 m) and the water volume released (19.5 ± 2.2 × 10⁶ m³) from the lake, showing good agreement with the results obtained from ground‐based measurements. The most relevant conditions that may have influenced the catastrophic drainage of Tam Pokhari in 1998 include the presence of: (i) a narrow (75 ± 6 m), steep (up to 50°) and high (120 ± 5 m) moraine dam; (ii) high lake level (8 ± 5 m of freeboard) and (iii) a steep overhanging glacier (>40°). The lake outburst substantially altered the immediate area, creating a low and wide (>500 m) outwash plain below the lake, a wide lake outlet channel (~50 m) and a gentle channel slope (~3–5°). Our new data suggest that the likelihood of a future lake outburst is low. Our results demonstrate that the datasets produced by photogrammetric techniques provide an excellent representation of micro‐landform features on moraine dams, lake water surfaces and the changes in both over time, thereby allowing highly accurate pre‐ and post‐GLOF (volumetric) change analysis of glacial lakes. Furthermore, it enables precise measurement of several predictive variables of GLOFs that can be useful for identifying potentially dangerous glacial lakes or prioritizing them for detailed field investigations. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

Investigation of Coulomb stress changes in south Tibet(central Himalayas) due to the 25th April 2015 M_W 7.8 Nepal earthquake using a Coulomb stress transfer model          下载免费PDF全文

Xu Cheng  Guojie Meng 《地震科学（英文版）》2016,29(5):271-279

After M_W 7.8 Nepal earthquake occurred, the rearrangement of stresses in the crust commonly leads to subsequent damaging earthquakes. We present the calculations of the coseismic stress changes that resulted from the 25 th April event using models of regional faults designed according to south Tibet-Nepal structure, and show that some indicative significant stress increases. We calculate static stress changes caused by the displacement of a fault on which dislocations happen and an earthquake occurs. A M_W 7.3 earthquake broke on 12 May at a distance of * 130 km SEE of the M_W 7.8 earthquake, whose focus roughly located on high Coulomb stress change(CSC) site. Aftershocks(first 15 days after the mainshock)are associated with stress increase zone caused by the main rupture. We set receiver faults with specified strikes, dips,and rakes, on which the stresses imparted by the source fault are resolved. Four group normal faults to the north of the Nepal earthquake seismogenic fault were set as receiver faults and variant results followed. We provide a discussion on Coulomb stress transfer for the seismogenic fault, which is useful to identify potential future rupture zones.  相似文献   

Distribution patterns of medicinal plants along an elevational gradient in central Himalaya, Nepal   总被引：1，自引：1，他引：0  

Maan B.ROKAYA  Zuzana MNZBERGOVá  Mani R.SHRESTHA  Binu TIMSINA 《山地科学学报》2012,9(2):201-213

This study aimed to compare the distribution patterns and trends of plant parts used among different groups of medicinal plants, geographical regions,and between medicinal plants and all vascular plants.We used the published sources for elevation records of 2,331 medicinal plant species to interpolate presence between minimum and maximum elevations and estimated medicinal plant richness for each 100-m elevational band. Monte Carlo simulations were used to test whether differences in elevational distribution between different groups of medicinal plants were significant. Total number of medicinal plants as well as different groups showed unimodal relationship with elevation. The elevational distributions of medicinal plants significantly differ between regions and between medicinal plant groups.When comparing the richness of all medicinal plants to all vascular plants,Monte Carlo simulations indicated that the numbers of medicinal plants are higher than expected at low elevations.The highest richness of medicinal plants at low elevation could be possibly due to favorable environmental factors such as high temperature, rainfall,sunlight or due to higher density of human population and thus higher pressure on use of any plants in lower elevations.  相似文献   

Improvement of glacial lakes detection under shadow environment using ASTER data in Himalayas, Nepal     

CHEN Wenbo  FUKUI Hiromichi  DOKO Tomoko  GU Xingfa 《中国地理科学(英文版)》2013,23(2):216-226

The detection of glacial lake change in the Himalayas, Nepal is extremely significant since the glacial lake change is one of the crucial indicators of global climate change in this area, where is the most sensitive area of the global climate changes. In the Himalayas, some of glacial lakes are covered by the dark mountains′ shadow because of their location. Therefore, these lakes can not be detected by conventional method such as Normalized Difference Water Index (NDWI), because the reflectance feature of shadowed glacial lake is different comparing to the ones which are located in the open flat area. The shadow causes two major problems: 1) glacial lakes which are covered by shadow completely result in underestimation of the number of glacial lakes; 2) glacial lakes which are partly identified are considered to undervalue the area of glacial lakes. The aim of this study is to develop a new model, named Detection of Shadowed Glacial Lakes (DSGL) model, to identify glacial lakes under the shadow environment by using Advanced Space-borne Thermal Emission and Reflection Radiometer (ASTER) data in the Himalayas, Nepal. The DSGL model is based on integration of two different modifications of NDWI, namely NDWIs model and NDWI she model. NDWIs is defined as integration of the NDWI and slope analysis and used for detecting non-shadowed lake in the mountain area. The NDWIshe is proposed as a new methodology to overcome the weakness of NDWIs on identifying shadowed lakes in highly elevated mountainous area such as the Himalayas. The first step of the NDWIshe is to enhance the data from ASTER 1B using the histogram equalization (HE) method, and its outcome product is named ASTER he . We used the ASTER he for calculating the NDWI he and the NDWIshe . Integrated with terrain analysis using Digital Elevation Model (DEM) data, the NDWI she can be used to identify the shadowed glacial lakes in the Himalayas. NDWIs value of 0.41 is used to identify the glacier lake (NDWIs≥0.41), and 0.3 of NDWIshe is used to identify the shadowed glacier lake (NDWIshe≤0.3). The DSGL model was proved to be able to classify the glacial lakes more accurately, while the NDWI model had tendency to underestimate the presence of actual glacial lakes. Correct classification rate regarding the products from NDWI model and DSGL model were 57% and 99%, respectively. The results of this paper demonstrated that the DSGL model is promising to detect glacial lakes in the shadowed environment at high mountains.  相似文献   

尼泊尔土地覆被遥感制图及其空间格局分析     

曹小敏  李爱农  雷光斌  谭剑波  张正健  严冬  谢瀚  张帅旗  杨勇帅  孙明江 《地球信息科学学报》2016,18(10):1384-1398

尼泊尔作为兴都库什-喜马拉雅区域的重要组成部分,是一个从平原到山地再到高原的典型过渡地带,具有多样且复杂的土地覆被类型。开展尼泊尔国家尺度的土地覆被研究,对该国的国土资源管理、生态环境保护具有重要的科学和实践意义,同时也能为中国倡导的“一带一路”国际区域经济合作战略提供基础数据保障。本文选用Landsat TM影像为数据源,基于面向对象与决策树相结合的土地覆被遥感制图方法,生产了尼泊尔全境2010年土地覆被产品（NepalCover-2010）,该产品包括8个一级类和32个二级类。同时,本文基于Google Earth高分辨率影像获取验证样本开展了NepalCover-2010产品的精度验证工作,并进一步分析了该国土地覆被类型的数量结构特征和空间格局特征与地形、气象要素间的关系。研究结果表明：① NepalCover-2010产品一级类总体分类精度达94.83%,Kappa系数为0.94;二级类的总体分类精度达87.17%,Kappa系数为0.85,能够准确地反映尼泊尔土地覆被类型的空间分布格局,是同类土地覆被产品中精度最好的。② 林地是尼泊尔最主要的土地覆被类型,其面积约占尼泊尔国土面积的41%。耕地次之,其面积占比约为25%,其中水田和旱地的面积分布比例约为2:3。③ 地形和气象要素对尼泊尔的土地覆被类型空间分布格局具有显著影响,自南向北随着地势的抬升,各土地覆被类型出现顺序表现出水田、常绿阔叶林、旱地、常绿阔叶灌木林、常绿针叶林、草原、稀疏植被和冰川/永久积雪的垂直地带性特征。  相似文献   

丹江口井网流体动态与尼泊尔M8.1地震同震响应分析     

李俊超  康波  陈星星  王秋良 《大地测量与地球动力学》2016,36(11):1025-1030

分析丹江口井网3口井水位、水温2013～2015年的观测数据,建立各个测项的正常动态,总结井网对2015-04-25尼泊尔M8.1地震的响应特征,探讨同震响应差异的可能原因,初步得到水位同震响应幅度与震级、井震距的关系。结果表明,井网水位年动态受降雨影响有一定规律,月正常动态普遍显示出固体潮效应与气压效应;水温年动态平稳,年变幅度在0.1 ℃左右。对于尼泊尔地震同震效应,唐扒井水位阶升-阶降式脉冲变化和水温陡降-缓升式脉冲变化是由水位和水温的变化机理不同导致的;雷庄井与唐扒井水位表现出不同的同震响应特征,判断与它们所处断裂的不同走向有关;盛湾井水温阶降型同震响应幅度较唐扒井小得多,可能是观测层岩性及地下水类型等差异导致的。  相似文献