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Yellow River (yellow + river)
Selected AbstractsThe behavior of specific sediment yield in different grain size fractions in the tributaries of the middle Yellow River as influenced by eolian and fluvial processesEARTH SURFACE PROCESSES AND LANDFORMS, Issue 8 2008Jiongxin Xu Abstract Based on data from 35 stations on the tributaries of the Yellow River, annual specific sediment yield (Ys) in eight grain size fractions has been related to basin-averaged annual sand,dust storm days (Dss) and annual precipitation (Pm) to reveal the influence of eolian and fluvial processes on specific sediment yield in different grain size fractions. The results show that Ys in fine grain size fractions has the highest values in the areas dominated by the coupled wind,water process. From these areas to those dominated by the eolian process or to those dominated by the fluvial process, Ys tends to decrease. For relatively coarse grain size fractions, Ys has monotonic variation, i.e. with the increase in Dss or the decrease in Pm, Ys increases. This indicates that the sediment producing behavior for fine sediments is different from that for relatively coarse sediments. The results all show that Ys for relatively coarse sediments depends on the eolian process more than on the fluvial process, and the coarser the sediment fractions the stronger the dependence of the Ys on the eolian process. The Ys,Dss and Ys,Pm curves for fine grain size fractions show some peaks and the fitted straight lines for Ys,Dss and Ys,Pm relationships for relatively coarse grain size fractions show some breaks. Almost all these break points may be regarded as thresholds. These thresholds are all located in the areas dominated by the coupled wind,water process, indicating that these areas are sensitive for erosion and sediment production, to which more attention should be given for the purpose of erosion and sediment control. A number of regression equations were established, based which the effect of rainfall, sand,dust storms and surface material grain size on specific sediment yield can be assessed. Copyright © 2007 John Wiley & Sons, Ltd. [source] Growth of the Yellow River delta over the past 800 years, as influenced by human activitiesGEOGRAFISKA ANNALER SERIES A: PHYSICAL GEOGRAPHY, Issue 1 2003Xu Jiongxin Abstract Based on measurements made over the past 50 years and data extracted from historical documents, a study has been made of the effect of human activities on the growth of the Yellow River delta over a time scale of 102 -103 years. During the period studied, the Yellow River emptied into the Yellow Sea and Bohai Sea, successively, and the deltas it created are known as the Abandoned and Modern Yellow River deltas. The growth of the Abandoned Yellow River delta can be divided into two stages. The first extended from AD 1194 to 1578, during which the growth was rather slow. The second extended from AD 1579 to 1855, when the growth was greatly accelerated. The curve showing the temporal variation of the growth of the Modern Yellow River mouth can be fitted by three straight lines with different slopes. Accordingly, its growth from 1855 to present can be divided into three stages, and the inflection points associated with three straight lines may be regarded as threshold points, reflecting marked changes in the nature and extent of human activities. On this basis, a three-stage descriptive model has been proposed to describe the process of river mouth extension in response to changing human activities. [source] Simulation of groundwater dynamics in the North China Plain by coupled hydrology and agricultural modelsHYDROLOGICAL PROCESSES, Issue 16 2006Tadanobu Nakayama Abstract We simulated the effects of irrigation on groundwater flow dynamics in the North China Plain by coupling the NIES Integrated Catchment-based Ecohydrology (NICE) model with DSSAT-wheat and DSSAT-maize, two agricultural models. This combined model (NICE-AGR) was applied to the Hai River catchment and the lower reach of the Yellow River (530 km wide by 840 km long) at a resolution of 5 km. It reproduced excellently the soil moisture, evapotranspiration and crop production of summer maize and winter wheat, correctly estimating crop water use. So, the spatial distribution of crop water use was reasonably estimated at daily steps in the simulation area. In particular, NICE-AGR reproduced groundwater levels better than the use of statistical water use data. This indicates that NICE-AGR does not need detailed statistical data on water use, making it very powerful for evaluating and estimating the water dynamics of catchments with little statistical data on seasonal water use. Furthermore, the simulation reproduced the spatial distribution of groundwater level in 1987 and 1988 in the Hebei Plain, showing a major reduction of groundwater level due mainly to overpumping for irrigation. Copyright © 2006 John Wiley & Sons, Ltd. [source] Water problems and hydrological research in the Yellow River and the Huai and Hai River basins of ChinaHYDROLOGICAL PROCESSES, Issue 12 2004Changming Liu Abstract This paper deals with hydrological research in regard to the water resources crisis in the vulnerable areas found in the northern part of China. This area includes three main river basins, namely the basins of the Yellow (Huang) River, the Hai River and the Huai River. Several water problems are becoming very severe. Among them, two are the most critical: the Yellow River has been drained dry in the main course of its lower reaches and along its major tributaries, and the groundwater table has rapidly declined in the floodplains of the three rivers' downstream areas. To counter the problems, particularly the critical issues mentioned above, hydrological research, which serves as the basis of water development and management, has been carried out in the last two decades. This paper addresses three basic scientific problems in North China, namely: (a) water consumption and the capacity for saving water; (b) the changes in hydrological processes and water resources caused by natural change and human activities; and (c) the ability to supply water resources and water safety in terms of both quantity and quality within a changing environment. However, opportunities and challenges for ameliorating the problems exist, and new ideas and methodology to solve the problems have been proposed, such as the interface process study on the interactions in the soil,root interface, the plant,atmosphere interface, the soil,atmosphere interface, and the interface of soil water and groundwater. In order to manage water resources in a sustainable manner, the study of water resources' renewal ability as affected by natural change and human activity is addressed from the viewpoint of both water quantity and quality, and their integration. To reduce the vulnerability of water resources in regional water management, a paradigm of sustainable water resources utilization is also proposed, using water,heat balance, water,salt balance, water,sediment balance, and water supply,demand balance. This approach may help reveal the basic problems and point to possible approaches to solving the water problems in North China in the 21st century. Copyright © 2004 John Wiley & Sons, Ltd. [source] Simulating the hydraulic characteristics of the lower Yellow River by the finite-volume techniqueHYDROLOGICAL PROCESSES, Issue 14 2002Qing Wan Abstract The finite-volume technique is used to solve the two-dimensional shallow-water equations on unstructured mesh consisting of quadrilateral elements. In this paper the algorithm of the finite-volume method is discussed in detail and particular attention is paid to accurately representing the complex irregular computational domain. The lower Yellow River reach from Huayuankou to Jiahetan is a typical meandering river. The generation of the computational mesh, which is used to simulate the flood, is affected by the distribution of water works in the river channel. The spatial information about the two Yellow River levee, the protecting dykes, and those roads that are obviously higher than the ground, need to be used to generate the computational mesh. As a result these dykes and roads locate the element interfaces of the computational mesh. In the model the finite-volume method is used to solve the shallow-wave equations, and the Osher scheme of the empirical function is used to calculate the flux through the interface between the neighbouring elements. The finite-volume method has the advantage of using computational domain with complex geometry, and the Osher scheme is a method based on characteristic theory and is a monotone upwind numerical scheme with high resolution. The flood event with peak discharge of 15 300 m3/s, occurring in the period from 30 July to 10 August 1982, is simulated. The estimated result indicates that the simulation method is good for routing the flood in a region with complex geometry. Copyright © 2002 John Wiley & Sons, Ltd. [source] Changes in hot days and heat waves in China during 1961,2007INTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 10 2010Ting Ding Abstract Based on the daily maximum temperature (DMT) records at 512 stations during 1961,2007, the geographical patterns and temporal variations of hot days (HDs) and heat waves (HWs, including those persisting for 3,5 days and longer) over mainland China were studied. The HD (and hence HW) was defined in two ways, one by an absolute criterion, DMT > 35 °C, as applied in the nationwide meteorological agencies and another in a relative sense, DMT > the 90th percentile threshold of a local daily temperature distribution around the day. Two centers of high frequencies (over 5 days per year) of the absolute HDs during June,September were found in the regions of Xinjiang and the mid-lower reaches of the Yangtze River. The highest frequencies of the absolute HWs were about 1.5 times per year in the Xinjiang region and to the south of the mid-lower reaches of the Yangtze River. The frequencies of the relative HWs were about 1,1.5 times per year in most of China. The HDs and HWs increased significantly during the studied period in most of China, especially over the southeastern coast and northern China (by over 4 days per decade for relative HDs and 0.4 times per decade for relative HWs), but decreased significantly at some stations in the lower reaches of the Yellow River. Over most of China except northwestern China, the frequency of HDs was high during the 1960s,1970s, low in the 1980s, and high afterwards, with strong interannual variations. A remarkable increasing trend of HDs occurred after the 1990s in all regions. The changes in HDs and HWs were closely related to those in rain days and atmospheric circulation patterns at the interannual and interdecadal scales. Copyright © 2009 Royal Meteorological Society [source] Features of cross-Pacific climate shown in the variability of China and US precipitationINTERNATIONAL JOURNAL OF CLIMATOLOGY, Issue 13 2005Q. Li Abstract In this study, we have analyzed the climate features of China and the United States with a focus on the differences, similarities, connectivity, and predictability of precipitation and the relationships between precipitation and large-scale patterns of natural variability. China precipitation is characterized by large seasonality, with a maximum in summer and a minimum in winter. The seasonality of precipitation shows an increasing linear tendency in northwest China, with a change of about 20% from 1901 to 1998. A relatively weaker increasing tendency also appears in the Big Bend of Yellow River (BBYR) and the Tibetan Plateau, while southwest China experiences a decreasing tendency. Furthermore, the seasonality in the BBYR shows particularly significant interdecadal variability, while that of southern and eastern China has decreased slightly in the recent decades. Compared to China, the United States as a whole has less precipitation in summer but more precipitation in other seasons. Here, the seasonality of precipitation is only about 24% of that in China. The annual mean precipitation is 64.1 mm per month in the United States, compared to 54.6 mm per month in China. The seasonality of precipitation exhibits a decreasing tendency in the southeast, Pacific Northwest, and Gulf Coast and an increasing tendency in the Great Lakes. The seasonality in the Great Plains exhibits large interdecadal variability. The long-term variations of precipitation are highly seasonally dependent. In summer, a decreasing trend is observed in north China and an increasing trend is found in eastern-central China. However, these trends are almost opposite in spring. In addition, the fall precipitation decreases with time nearly everywhere in China except for the middle and lower reaches of the Yangtze River Valley. Results also indicate that the El Niño/Southern Oscillation (ENSO), the Arctic Oscillation (AO), the North Atlantic Oscillation (NAO), the Pacific Decadal Oscillation (PDO), and the North Pacific (NP) fluctuation affect strongly the variations of China and US precipitation. Although these influences vary with regions and seasons, we in particular emphasize the importance of AO and NAO for China precipitation and NP and PDO for US precipitation. In fall, ENSO and PDO are the two phenomena that influence predominantly precipitation variability in both China and the United States We also identify the common phenomena that influence China and US regional precipitation and provide a better understanding of the physical mechanism for precipitation variability through the associated changes in atmospheric and oceanic conditions. Furthermore, we develop a linear regression model, based on multiple regression method by combining the regionally and seasonally varying impacts, to increase the skill of precipitation prediction. Copyright © 2005 Royal Meteorological Society [source] Drainage and salinity assessment in the Huinong Canal Irrigation District, Ningxia, China,IRRIGATION AND DRAINAGE, Issue 2 2005Peter Hollanders irrigation; drainage; salinisation; développement durable Abstract In the Huinong Canal Irrigation District, Ningxia, China, annually almost half of the amount of irrigation water, which is supplied from the Yellow River, is drained back to the river through an open drainage system. Waterlogging and salinization occur in parts of the irrigated area and part of the water drains to the surrounding desert. While 85,90% of inflow to the area is irrigation water there are good possibilities for water saving. To analyse water movement at field level and resulting drainage needs, from autumn 1998 until spring 2001 observations were made in two experimental areas: Pingluo and Huinong. The data were used for the calibration and validation of three computer models: SWAP, MODFLOW and DUFLOW. Different scenarios of water and salt behaviour in the unsaturated and saturated zone were simulated, as well as the flow through one of the main drains. The effects of various irrigation amounts and groundwater tables on crop growth, percolation and drainage needs were analysed. The present average irrigation water application during the growing season is 630,mm. On average 15% of the supplied water (665 million m3,yr,1) remains in the area. This is mainly irrigation water that was not used by the crops and did not reach the drainage system. It was found that an irrigation level of 75% of the present practice with a groundwater table of 1.0,m below the surface during the growing season gave the best results. Under such a practice the soil salinity will fluctuate around 3,3.5,dS,m,1, resulting in a good growth of wheat and a yield reduction for maize of about 20%. When adequate amounts of irrigation water are supplied in combination with local drainage improvements, the areas with middle and low-yielding crops can be reduced, as well as the area of wasteland. Copyright © 2005 John Wiley & Sons, Ltd. Annuellement presque la moitié de la quantité d'eau d'irrigation dans le district d'irrigation du canal Huinong, Ningxia, Chine, alimenté par la Rivière Jaune, est retournée à la rivière par un système de drainage à ciel ouvert. Des cas de saturation d'eau et de salinisation surgissent dans certaines parties de la zone irriguée et une partie de l'eau suinte vers le désert environnant. Comme 85,90% de l'entrée de l'eau dans la zone est de l'eau d'irrigation il y a de bonnes possibilités pour économiser de l'eau. Pour analyser la circulation de l'eau au niveau du champ et la nécessité de drainage des observations ont été effectuées pendant la période d'automne 1998 jusqu'au printemps 2001 dans deux zones expérimentales, Pingluo et Huinong. Les données rassemblées ont servi pour le calibrage et la validation de trois modèles informatiques: SWAP, MODFLOW et DUFLOW. Ces modèles ont été employés pour simuler plusieurs scénarios de comportement de l'eau et du sel dans la zone non saturée et dans la zone saturée tout comme l'écoulement par un des tuyaux d'écoulement principaux: le cinquième tuyau d'écoulement. L'effet de l'apport de différentes quantités d'eau d'irrigation, de différents niveaux de la nappe phréatique sur la croissance des cultures, la percolation et la nécessité de drainage a été analysé. L'actuel apport d'eau d'irrigation est de 630,mm en moyenne pendant la saison de croissance. Quinze pour cent en moyenne de l'eau fournie (665 millions m3/année) reste dans la zone, principalement de l'eau d'irrigation qui n'a pas servi aux cultures et qui n'a pas atteint le système de drainage. Un niveau d'irrigation représentant 75% des valeurs actuelles et une surface de la nappe phréatique de 1.0,m sous la surface donnent les meilleurs résultats pendant la saison de croissance. De tels apports entretiennent une salinisation du sol qui fluctuera entre environ 3 et 3.5,dS,m,1, donnant un bon résultat de la croissance du blé et une diminution du rendement pour le maïs d'environ 20%. Lorsque l'alimentation par des quantités adéquates d'eau d'irrigation sera assurée en combinaison avec des améliorations du drainage local, la zone donnant des récoltes moyennes et basses peut être réduite ainsi que les zones incultes. Copyright © 2005 John Wiley & Sons, Ltd. [source] RUNOFF AND SEDIMENT RESPONSES TO CONSERVATION PRACTICES: LOESS PLATEAU OF CHINA,JOURNAL OF THE AMERICAN WATER RESOURCES ASSOCIATION, Issue 5 2003Mingbin Huang ABSTRACT: Soil erosion is the most significant threat to land productivity and environmental quality on the Loess Plateau of China. The annual total sediment load of the Yellow River is 1.6 billion tons, with about 90 percent coming from soil erosion from the Loess Plateau. To reduce soil erosion from the Loess Plateau, conservation practices, including tree planting, ridge construction between fields and around gullies, terrace and ditch construction perpendicular to the main slope, and dam construction are being implemented. An evaluation of these conservation practices is required before they are implemented at the large scale. The objective of this study is to evaluate the effectiveness of conservation practices to control runoff and sediment yield from paired watersheds in the hilly gully region of the Loess Plateau. The advantage of the paired watershed approach is its sensibility in detecting differences in runoff and sediment transport by monitoring both watersheds during two periods, an initial period with no conservation practices and a treatment period with only one watershed subjected to conservation practices. Implementation of the conservation practices resulted in (1) cumulative runoff and sediment yield that were, respectively, 25 and 38 percent less from the treatment watershed than from the control, (2) a decrease in the number of rainfall events producing runoff and sediment transport (94 in the control versus 63 in treatment), and (3) a reduction in the maximum discharge and maximum suspended sediment concentration. [source] Genetic diversity and population structure of indigenous yellow cattle breeds of China using 30 microsatellite markersANIMAL GENETICS, Issue 6 2007G. X. Zhang Summary Twenty-seven domesticated yellow cattle breeds of China and three introduced cattle breeds were analysed by means of 30 microsatellite markers to determine the level of genetic variation within and among populations as well as the population structure. In all, 480 microsatellite alleles were observed across the 30 breeds with the mean number of alleles per locus of 9.093 for native breeds and 6.885 for the three introduced breeds. Mean F -statistics (0.08) for Chinese native cattle breeds implied that 92% of the total genetic variation was from genetic differentiation within each breed and 8% of the genetic variation existed among breeds. A phylogenetic tree was constructed based on Nei's genetic distances, and three clusters were obtained. According to the tree, the three introduced breeds were distinct from the 27 native breeds. The indigenous cattle breeds were divided into two clusters, one cluster including five humpless breeds and the other cluster containing 22 humped breeds. This study identifies multiple origins of yellow cattle of China from Bos taurus and Bos indicus. Furthermore, population structure analysis implies that there are possibly five independent original domestications for yellow cattle in China. Four of five origins were four different Bos indicus types, mainly in areas of the Chang Jiang, the Zhu Jiang River basin, the Yellow River and the Huai River basin. The other origin was for Bos taurus type of Mongolian descent, mainly located in Northwestern China, the Mongolian plateau and Northeastern China or north of the Great Wall. [source] Preliminary Provenance Research on Chinese Neolithic Pottery: Huating (Xinyi County) and Three Yellow River Valley SitesARCHAEOMETRY, Issue 1 2001Anwu Xu Instrumental neutron activation analysis (INAA) was applied to sherds from the important site of Huating and, for comparison, several Neolithic sites in the valley of the Yellow River. We hoped to compare the compositions of two stylistically different ceramics found at Huating, and to evaluate the degree of compositional clustering and inter-site resolution that could be expected in an area that is noted for its extensive, and possibly very homogeneous, loess deposits. In addition, pottery sherds from Huating have been examined by microscopic petrography. All of these results will provide needed input in the planning of research towards the formation of a Neolithic/Shang Dynasty ceramic database for future use in archaeological research in China. [source] Distribution and Forming Model of Fluvial Terrace in the Huangshui Catchment and its Tectonic IndicationACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2010Xianyan WANG Abstract: The Huang Shui River, a main tributary of the Yellow River, crosses a series of tectonically subsided and uplifted areas that show different patterns of terrace formation. The distribution of fluvial terrace of the Huang Shui River is studied through topographic and sedimentologic terrace mapping. Three terraces in the Haiyan Basin, four terraces in the Huangyuan Basin, 19 terraces in the Xi'ning Basin (the four high terraces may belong to another river), nine terraces in the Ping'an Basin, five terraces in the Ledu Basin and 12 terraces in the Minhe Basin are recognized. Sedimentology research shows that the geomorphologic and sedimentological pattern of the Huang Shui River, which is located at the margin of Tibet, are different from that of the rivers at other regions. The formation process of the terrace is more complicated at the Huang Shui catchment: both accumulation terrace and erosion terrace were formed in each basin and accumulation terraces were developed in some basins when erosion terraces were formed in other basins, indicating fluvial aggradation may occur in some basins simultaneously with river incision in other basins. A conceptual model of the formation process of these two kinds of fluvial terraces at Huang Shui catchment is brought forward in this paper. First, the equilibrium state of the river is broken because of climatic change and/or tectonic movement, and the river incises in all basins in the whole catchment until reaching a new equilibrium state. Then, the downstream basin subsides quickly and the equilibrium state is broken again, and the river incises at upstream basins while the river accumulates at the subsidence basin quickly until approaching a new equilibrium state again. Finally, the river incises in the whole catchment because of climatic change and/or tectonic movement and the accumulation terrace is formed at the subsidence basin while the erosion terrace is formed at other basins. The existence of the accumulation terrace implied the tectonic subsidence in the sub-basins in Huang Shui catchment. These tectonic subsidence movements gradually developed from the downstream Minhe Basin to the upstream Huangyuan Basin. Dating the terrace sequence has potential to uncover the relationship between the subsidence in the catchment and the regional tectonic at the northeastern Tibetan Plateau. [source] Migration of Depocenters and Accumulation Centers and its Indication of Subsidence Centers in the Mesozoic Ordos BasinACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 2 2009Junfeng ZHAO Abstract: Based on the integrated study of structure attributions and characteristics of the original basin in combination with lithology and lithofacies, sedimentary provenance analysis and thickness distribution of the Mesozoic Ordos Basin, it is demonstrated that the depocenters migrated counterclockwise from southeast to the north and then to the southwest from the Middle-Late Triassic to the Early Cretaceous. There were no unified and larger-scale accumulation centers except several small isolated accumulation centers before the Early Cretaceous. The reasons why belts of relatively thick strata were well developed in the western basin in several stages are that this area is near the west boundary of the original Ordos Basin, there was abundant sediment supply and the hydrodynamic effect was strong. Therefore, they stand for local accumulation centers. Until the Early Cretaceous, depocenters, accumulation centers and subsidence centers were superposed as an entity in the southwest part of the Ordos Basin. Up to the end of the Middle Jurassic, there still appeared a paleogeographic and paleostructural higher-in-west and lower-in-east framework in the residual basin to the west of the Yellow River. The depocenters of the Ordos Basin from the Middle,Late Triassic to the Middle Jurassic were superposed consistently. The relatively high thermal maturation of Mesozoic and Paleozoic strata in the depocenters and their neighborhood suggest active deep effects in these areas. Generally, superposition of depocenters in several periods and their consistency with high thermal evolution areas reveal the control of subsidence processes. Therefore, depocenters may represent the positions of the subsidence centers. The subsidence centers (or depocenters) are located in the south of the large-scale cratonic Ordos Basin. This is associated with flexural subsidence of the foreland, resulting from the strong convergence and orogenic activity contemporaneous with the Qinling orogeny. [source] Mangshan Loess in Central China and the Paleomonsoon Variations since the Last InterglaciationACTA GEOLOGICA SINICA (ENGLISH EDITION), Issue 3 2004JIANG Fuchu Abstract, The Mangshan Yuan is a loess platform on the southern bank of the Yellow River, which is located in northwestern Zhengzhou of Henan Province, China. The typical Zhaoxiayu section of the Mangshan Yuan preserves stratigraphical loess units above S10 with a total thickness of 172.1 m, which includes 15.7 m of the last interglacial paleosol S1, 77.3 m of the last glacial loess L1 that consist of 41.6 m of the late stade L1LL1, 13.2 m of the interstade L1SS1 and 22.5 m of the early stade L1LL2. Based on the age marking points by correlating magnetic susceptibility of the section with the SPECMAP curve, the timescale of the section was constructed, and the average accumulation rate and the resolution of each loess strata over the S2 were subsequently calculated using the susceptibility age model. The results indicate that strata units developed in the glacial, interglacial stages, stadial and interstadial show substantial differences in grain size, average accumulation rate and time resolution ub the Zhaoxiayu section. Specifically, the average accumulation rate of the loess L1LL1 is 3.45 mm/a, whereas that of paleosol S1 is only 0.28 mm/a. Based on the high-resolution records of magnetic susceptibility and >45 ,m fraction percentage of the loess-paleosol, the summer and winter monsoon variations as well as their interrelations since the last interglaciation have been discussed, which were correlated with the SPECMAP and the GRIP climate records. [source] Alpine grassland degradation and its control in the source region of the Yangtze and Yellow Rivers, ChinaGRASSLAND SCIENCE, Issue 3 2005Huakun Zhou Abstract Serious grassland degradation is endangering the environment of the source regions of the Yangtze and Yellow Rivers (SRYYR). There is an urgent need to analyze and review the grassland resources, status of grassland degradation, factors causing grassland degradation, and measures for grassland protection and restoration so as to ensure sustainable development in the SRYYR. This review shows that: (1) The alpine meadow, one of the most important grassland types in the SRYYR, can be divided into four subtypes: typical alpine meadow, alpine swamp meadow, alpine steppe meadow and alpine shrub meadow. (2) There is approximately 357.13 × 104 ha degraded grassland in this area, which is 34.34% of the area of all the investigated grasslands in the SRYYR, and heavily degraded grasslands cover an area of 74.34 × 104 ha, approximately 20.82% of the degraded grasslands. (3) Alpine grassland degradation in the SRYYR follows the following sequence: non-degraded grassland , lightly degraded grassland , moderately degraded grassland , heavily degraded grassland. (4) Grassland degradation in the SRYYR is caused by the integrated effect of anthropogenic and natural factors. The principal factors causing grassland degradation are thought to be long-term overgrazing and the destruction by rodents that follows, and climate warming, which accelerates the grassland degradation process. (5) Some effective management practices (e.g. rodent and ruderal weed control, establishment of artificial grassland, rational management of grassland, and optimizing livestock structure) and integrated countermeasures for the restoration of degraded grasslands have been developed in the SRYYR. [source] | ||||||||||||||||