Snow is one of the most active elements on the earth, which is an important mass source of polar ice sheets and alpine glaciers, as well as a main supply for the runoff. Its distribution and evolution have a great impact on global hydrological cycle, ecosystem, climate evolution and other natural processes, and play a significant role in hydrological process in alpine mountain area. Melt water from mountain snow and glacier is the main form of water supply at the source of the Yellow River. Therefore, it is urgent to carry out a comprehensive scientific research on snow water resources in the source area of the Yellow River, and further to put forward scientific and reasonable strategies for protecting and developing the Yellow River water resources, based on the accurate assessment of the current status of water resources in the source area of the Yellow River and its variation trends. The research on snow distribution involves challenging and hot scientific frontiers issues like the interaction of atmospheric turbulence and particles, common scientific issues such as multi-field coupling and multi-scale, as well as crosscutting issues between mechanics and geography, atmospheric physics, climate change and other related disciplines. Current research methods for snow distribution include field observation, remote sensing inversion and model research based on dynamic processes. As for the limitations of the first two methods, it has become one of the important methods for snow water resources research to carry out the multi-physical process, multi-scale, multi-field coupling simulation of the spatio-temporal evolution of snow distribution. This paper focuses on introducing the research status and progress of snow distribution, and pointing out the challenges and future research trends.

The beach area of the lower Yellow River has always been threatened by floods, its economy is undeveloped and its ecological environment is fragile. Moreover, its governance has always been complex and difficult, which involves a variety of factors, departments and problems. Firstly, this paper reviews the development and management history of the beach area, and summarizes representative views and ideas about the governance based on the analysis of published literature and field research. On this basis the article argues that the governance of the beach area of the lower Yellow River is a complex issue, which should take flood prevention security, ecological environmental protection, industrial development and people's livelihood into consideration. Therefore, synergy governance by multiple departments, industries, levels, regions and disciplines is required. Then, the article constructs a synergy governance system for the beach area, including governance goals, guiding ideology, governing subjects and governing objects. The governing subjects feature multi-sector, multi-industry, multi-layer, multi-region and multi-discipline. The governing objects are multi-faced synergy governance including protection and development, engineering construction, financial investment, policy system, administration, cultural tourism, technical research and development, and so on. Finally, it puts forward some ideas and suggestions for the synergy governance of the beach area. This article provides new ideas for implementation of the strategy of ecological protection and high-quality development in the Yellow River basin, as well as flood prevention security, attaining shaking off poverty and achieving prosperity and ecological civilization construction.

Tibetan Plateau as a shelter plays an important role in ecological security in China, even in Asia, which is also the key source region of many rivers. Under the joint effects of global changes and anthropogenic activities, many serious ecological and environmental issues have occurred in Tibetan Plateau. Particularly, typical alpine wetland generally shows a trend of degradation. By analyzing the current studies of wetland area change and degradation in the structure and function of ecosystems and potential causes of wetland degradation, this study addresses dynamical changes and evolutional trend of alpine wetland in Tibetan Plateau. The ecological protection and restoration projects conducted by Chinese government have played a large role in recent twenty years, but the degradation of alpine wetland is still a great challenge. As a long-term work, it is needed to strengthen the active cooperation of technology research and development projects and engineering projects of ecological restoration in the future and to increase natural capacity of recovery of wetland through establishing a long-term management mechanism. At the same time, to construct complete evaluation models and indicator systems for protection of alpine wetland, and further to improve monitoring system and evaluating system for project implementation effect are necessary. By conducting a long-term ecological monitoring for alpine wetland ecosystem in the source regions of the Yellow River and Yangtse Rive, Shouqu wetland of Yellow river and Zoige wetland should be merged into the management scope of National Park as Sanjiangyuan, which can be planed as a whole to establish a platform of scientific service and mechanism of information sharing.

This paper analyzes the main progress and existing problems in the research of impacts of the global climate change on regional climate, water resources, ecological pattern, agricultural and animal husbandry production, geological disasters, cultural relic protection and its human responses in China. It also discusses the future trend of the impact of climate change on the Yellow River basin and puts forward suggestions for research on the following aspects:to establish a meteorological, hydrological, environmental and geological disaster observation, forecast and early warning system for the Yellow River basin; clarify the space-time process of basin water resources under the influence of multiple factors and improve the efficiency of basin water resources; adjust sloping farmland and ecological land to strengthen the capacity of water conservation in the river basin; strengthen the study of plant physiological and ecological adaptability and optimize the distribution of agriculture and grass industry in the river basin; revise the environmental zoning of cultural heritage and carry out the research and development of preventive protection technology; strengthen the research on new materials for loess landslide reinforcement and the cooperative technology of ecological restoration.

The Loess Plateau is characterized by low mountain and hilly terrain with loose soil, high erodible, broken terrain, and fragile ecological environment. The productivity of dryland farming is low and unstable historically. With the increase of population pressure, long-term over-reclamation, and over-grazing its ecosystem has been long degraded. Since the founding of PR China, terraced fields have been being constructed on a large scale to effectively reduce soil erosion. Thanks to the continuously updating construction standard of terraced fields it is more and more convenient to produce large areas of mechanized farmland. Since the beginning of the new century, the crop farming system with film mulching furrow-ridge as the vital progress has been widely promoted. In particular, corn and potato mulched by plastic film mulching furrow-ridge system yield much higher than other crops. These have created favorable conditions for coordinated development of grain, complete feed, livestock cash crops, and effectively promoted eradication of poverty and the realization of the goal of overall well-off society. High-quality development in the new era requires innovation in the ecological-friendy technologies and development model of dryland farming. These will help promote the development of natural dryland farming, exploring the transformation from passive to an active mode of ecological restoration and realizing the development goal of regional eco-sustainability.

Water pollutants in Lanzhou section of Yellow River can enter the agricultural ecosystem along with irrigation, migrate among water-soil-bio systems and be accumulated in organisms including human body. These pollutants can not only cause serious influences on the ecological environments of both sides of the Yellow River but also cause various damages to animals and plants and even to human health. In the present paper, we review the progress of studies on environmental pollution monitoring, ecological risk assessment and ecological remediation in the agricultural ecosystem in Lanzhou section of the Yellow River. We also summarize the existing problems and provide some countermeasures.

Various types of restoration approaches are currently adopted to restore the degraded grasslands of the QinghaiTibetan Plateau, including fencing off grasslands, establishing artificial grasslands, adding nutrients and no-tillage sowing. Although they have played an important role in the process of alpine grassland restoration, a systematic analysis of the key factors and techniques (i.e., physical, chemical and biological factors related to plant and soil) that constrain the restoration of degraded alpine grasslands is still lacking. Here, we review the key factors constraining restoration of degraded alpine grasslands, including seed provenance, soil microorganisms, soil nutrients and local culture. Furthermore, we propose a heuristic framework to combine a suit of approaches to deal with these key factors in the alpine grassland restoration practices. Specifically, the heuristic framework will 1) develop techniques for seed collection and multiplication of native grasses, seed coating, optimal combination of a range of native species, and no-tillage sowing; 2) screen compound microbial species suitable for degraded grassland restoration and develop microbial agents to reduce the constraints of soil microorganism; 3) develop vegetation restoration techniques tailored to soil nutrient regulation in order to deal with the constraint on soil; 4) develop adaptive management based on application of new techniques tailored to Tibetan herders. Therefore, we propose "close-to-ature" recovery restoration, a novel restoration measure that rests on of native grass species, soil microorganisms and regulation of nutrient, as a potential approach to effectively and efficiently restore the degraded grasslands on Tibetan Plateau.

Since the Grain for Green Project was launched in the Loess Plateau in 1999, the vegetation restoration effect has been significant. However, a high degree uncertainty in changes and predictions of regional water and carbon cycles caused by vegetation changes hinders the development of vegetation restoration assessment and prediction. Water use efficiency (WUE) is an important indicator for assessing the water-carbon cycle in ecosystems. Based on the simulation results of regional scale actual evapotranspiration (ET) by the PT-JPL model, combined with the GPP of the Loess Plateau, this paper analyzes the temporal and spatial trends of WUE on the Loess Plateau after the Grain for Green Project, and further uses CMIP6 to predict the WUE's of Loess Plateau under three scenarios. The results show that vegetation in the Loess Plateau increased significantly from 2001 to 2015, and that GPP and ET increased at rates of 3.59 g C·m^-2 and 4.39 mm per year, respectively. WUE increased in 72.68% of the regions with an average annual 0.003 g C·mm^-1·m^-2 increase. In the three scenarios from 2015 to 2100, ET showed an increasing trend while GPP and WUE didnot change much in SSP126 and increased significantly in SSP245 and 370 scenarios. WUE increased with the increase of GPP. WUE combines "consumption" and "use" of water resources to illustrate the effectiveness of the Project. Although the revegetation increases regional water consumption, it has significantly improved the vegetation cover, effectively enhanced the carbon sequestration capacity and water use efficiency of the vegetation, and increased the drought tolerance of the entire Loess Plateau vegetation. The WUE's of different tree species need to be further analyzed to screen out the tree species with higher drought resistance for vegetation restoration. The ecological construction and water conservation of the whole region is an eternal topic, and the healthy development of water-carbon cycle should be improved in current climate context in order to provide a better theoretical guarantee for the synergistic development of economic construction and ecological civilization of the Loess Plateau.