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Aeolian desertification, a serious degradation of soil and vegetation, is one of the most important issues in arid and semi-arid regions in terms of society/economy and environment. However, there still remains problematic on the study of climate change and its impact on aeolian desertification in the such region. To reverse aeolian desertified land (ADL), it is necessary to identify the causes of ADL. The paper uses meteorological data to characterize climate change and its impact on ADL during 1970–2015 with the method of geostatistics, and the results showed that the climate tended to be warmer and drier. The linear trend rates of annual mean temperature for the whole year (WY), winter half year (WHY), and summer half year (SHY) were 0.24 °C (10 a)−1, 0.25 °C (10 a)−1, and 0.18 °C (10 a)−1, respectively. The linear trend rates of average precipitation were − 8.29 mm (10 a)−1, 2.69 mm (10 a)−1, and − 8.27 mm (10 a)−1, respectively. Rising temperatures in WY, WHY, and SHY lead to increase topsoil evaporation and may trigger ADL development. However, the decreasing precipitation in SHY weakened soil erosion, and the increasing precipitation with a rate of 0.26 mm a−1 in WHY improved the soil moisture content. Therefore, our results show that climatic change has a relatively high sensitivity, especially in WHY, to the expansion or reversal of ADL in semi-arid regions. [ABSTRACT FROM AUTHOR]

It is well known that soil erosion at the watershed scale is the result of interactions between various factors. Among these environmental factors, vegetation is the most important and plays a major role in the soil erosion process. The impact of fractional vegetation cover change (FVCC) on soil erosion in non-contributing areas is a heavily discussed topic. In this paper, the fractional vegetation cover (FVC) in 2002 and 2005 was calculated by using a backpropagation neural network based on remote sensing (RS) data. Then the impacts of FVCC on sediment loads at the outlets of two Miyun reservoir sub-basins were evaluated by integrating RS and geographic information system with statistical analysis. The Miyun reservoir basin (MRB) is characterized by hilly and mountainous topographies and seasonal rainy weather. The primary goal of this paper is to gain a better understanding of FVCC, its driving forces, and its impact on regional soil erosion. We discuss spatiotemporal variations in precipitation and soil erosion, identify which factors contribute to those variations, analyze the influences of FVCC on climate change and human activities and, finally, conclude that changes in FVC and climate regimes are primary factors for soil erosion in MRB. We also discuss how sediment loads may be used to quantitatively separate biophysical and anthropogenic influences and to identify critical thresholds that might have dramatic consequences for the watershed ecosystem. These findings should be quite helpful for sensible watershed development and management planning. [ABSTRACT FROM AUTHOR]

In recent years, climate and environment changes since the Little Ice Age have become a focus in modern research. The paper selected the sediment (77 cm) of Sihu Lake, which was located in Guilin, southern China, as the research object and analyzed the karst wetland environmental changes within nearly 450 years. According to the vertical profile of indicators and geochemical elements in sediment core, the regional environmental evolution was divided into four stages. The former two stages were mainly influenced by Little Ice Age (1562–1895). The third stage climate has changed slowly. The fourth stage was mainly affected by human activities and global warming. The factor analysis of geochemical elements indicated that karst wetland regional environmental change was affected by four major factors. In the 53–77 cm stage (1562–1703), F1 (erosion factor), F2 (watershed runoff and diagenesis factor) and F3 (regional background factor) were reduced, indicating that it was in cold and dry stage of Little Ice Age. In the 20–53 cm stage (1703–1895), F1 and F2 increased, indicating that it was in cold and wet stage of Little Ice Age. In the 4–20 cm stage (1895–1987), F1, F2 and F4 (human activity factor) increased slowly, indicating that the climate was affected by global warming and more precipitation. In the 0–4 cm stage (1987–2007), F1 and F2 reduced and F4 increased, indicating the reduced precipitation, rising temperature and more impact of human activities. In addition, it was proposed that the Little Ice Age in Guilin District in southern China started in the 1560s and lasted until the 1895s or so. [ABSTRACT FROM AUTHOR]

The Keriya River Basin was chosen as the study site in this paper in order to investigate the suitable scales of natural and artificial oases with a certain water resource quantity. A calculation model was constructed and the suitable scales of natural and artificial oases were analyzed using remote sensing images, water resources, weather and socioeconomic data. The results showed that (1) high- and low-flow variations were apparent for the Keriya River. The mean values for the high-flow period, normal flow period and low-flow period were 9.23 × 10 m, 7.177 × 10 m and 5.741 × 10 m, respectively. (2) The ecological water demand of natural oasis in the lower reaches of the Keriya River Basin was 2.561 × 10 m. (3) In the Tarim Basin, the proportion of natural and artificial oases was 6:4. (4) In the middle reaches, after guaranteeing the unchangeable scale of artificial oases, the most suitable size of a natural oasis was 798-1,157 km. Under the reasonable proportion (i.e. proportion of 6:4 for the natural and artificial oases), the respective suitable scales of natural and artificial oases in the middle reaches were 831-1,003 km and 554-669 km. This study constructed a model for calculating the suitable scale of an oasis, verified the suitable proportions of natural and artificial oases and discussed the reasonable scales of oases in order to provide a new theoretical basis for determining reasonable development planning in similar river basins located in extremely arid regions. [ABSTRACT FROM AUTHOR]

The generality of the Christiansen model is verified using potential evaporation data as reference for the unit model developed in stella. The spatial model in SME is calibrated with data from six hydrological and meteorological stations around the study area. The results show that the observed and simulated data have a good fit, in which the revised Nash-Sutcliffe efficiency (NSE), balance error ( B), and explained variance (EV) are 0.56, −0.2, and 0.55, respectively. The best fit is seen in autumn and winter; for spring, the actual values are generally higher than in simulated observations. The spatial model can simulate the majority of summer peaks, but some are not simulated well. Running the model under different spatial resolutions shows a certain degree of stability, with the revised NSE ranging from 0.29 to 0.50. As spatial resolution increases, the simulation NSE values behave non-linearly. With the other parameters unchanged the impact of human activities, which is represented by climate change scenarios on the hydrological process, is analyzed. Assuming constant temperature, precipitation has a greater influence on runoff than on evaporation; while when precipitation is constant, evaporation is influenced more by temperature. Although the model can validate the effect of climate change on runoff and evapotranspiration, it is not enough to describe the complex relationship between runoff, evaporation, temperature, and precipitation accurately, because the description of the water cycle process is simplified compared with a highly specialized hydrological model. The water and heat coupling process is not included in the soil freezing and thawing process; the source code of SME needs to be deeply understood to improve the algorithms of interpolation and conflux. More importantly, the current work does not consider the impact of human activities endogenously. The main purpose of this paper is to build a better basis for developing a meaningful integrated ecological economic model in the Heihe River Basin to solve its ecological and economic problems. [ABSTRACT FROM AUTHOR]

Optical stimulated luminescence (OSL) study on sand and fossil soils from Hulun Buir Dunefield in Eastern China is reported in this paper. Aeolian dune sequences responded to the climate change by alternations of aeolian sand and dark sandy soils, which corresponded to arid and humid conditions, respectively. Optical dating using the single aliquot regeneration technique with quartz was applied to the deposits. The results indicate that the soils and underlying aeolian sand correspond to the Holocene optimum (HO) and the last late glacial, respectively. Combined with studies of OSL dating of 13 profiles and grain-size, magnetic susceptibility, total organic carbon, sediment color and scanning electron microscopy measurements for two representative sections, indicate the expansion in the last late glacial sand was 10 times that of today. The dune field was not totally stabilized by vegetation cover until HO (10-5 ka BP). [ABSTRACT FROM AUTHOR]

The changes in annual runoff of the three original rivers and the mainstream of Tarim River were analyzed by the non-parametric tests based on the hydrologic data during the period of 50 years. Using hydrologic data, meteorological data and the fitted equation, the impacts of climate change and human activities on annual runoff of the mainstream were assessed. Based on the analysis, the following conclusions can be drawn: (1) headstream runoff has increased in the past 50 years, and has sharply jumped after 1990; (2) mainstream runoff decreased progressively in the past 50 years, which indicated that interference from human activities was the main cause for the decreasing runoff. This had greater negative influence than positive influence, which caused the mainstream average runoff to decrease by 5.4 × 10m from 1990 to 2008 as compared to 1957-2008; (3) if human activities remained at pre-1990 levels, climate change alone would have caused the runoff of mainstream of Tarim River to increase by 5.4 × 10m annually in the past 20 years; (4) if the climate had remained at pre-1990 conditions, human activities alone would have caused the runoff of mainstream of Tarim River to increase by 5.4 × 10m annually over the past 20 years. However, mainstream average runoff was 42.6 × 10m from 1990 to 2008 with the negative effects of human activities masked by the larger, positive effect of climate changes. The results in this paper provide a scientific basis for conservation strategies, sustainable management, and ecological restoration of the Tarim River Basin. [ABSTRACT FROM AUTHOR]

Land use/cover change and its driving forces has been one of the most important fields in global environmental change research since the 1990s. Karst areas are distributed extensively on the Earth's surface and are usually characterized by a fragile eco-environment. In southwest China, karst landforms are fully developed and their eco-environment is highly fragile. Over the past decades, irrational land use practice has caused a series of alarming eco-environmental issues including forest clearing, soil erosion, and karst rocky desertification. Therefore, it is of great practical significance to study land use/cover change in this area and its driving forces in order to re-build the damaged eco-environment and achieve sustainable land use. In this paper, the authors conduct a case study on land use/cover change and its natural and human driving forces since the early 1970s in southwest China's Maotiaohe watershed. The results indicate that the land use/cover pattern in the study area has undergone a very complex change, which is a result of combined action of both natural and anthropological factors. In the 1970s and 1980s, climate change and fast population increase played dominating roles in the change of arable land, shrub land, grassland, and rocky desertification land. Since the early 1990s, economic development has gradually taken the place of population change to become the overwhelming human factor to go along with climate change in driving the land use/cover change, particularly the change in arable land, construction land, and rocky desertification land. [ABSTRACT FROM AUTHOR]

The study area, the middle part of Inner Mongolia including Hohhot city, Baotou city, Wulanchabu city, Ordos city, Bayannaoer city and Wuhai city, is one of typical eco-geographical transition zones in China. Using monthly precipitation data (1961–2003) from 45 meteorological stations in the study area, this paper analyzes characteristics and tendencies of annual and seasonal rainfall variations, and reveals multi-time scales structures of these time series through wavelet analyses; also, the periods of annual and seasonal precipitation series are identified, and the periodical oscillations and points of abrupt change at the principal period scale are discovered. The results show that annual precipitation varies in a large range, and has an ascending tendency at an increasing rate of 1.482 mm/10a; the multi-time scales periodical oscillations are clear; differences in tendencies, ranges and decadal precipitation anomalies exist within each decade during 1961–2000. The seasonal allocation of overall annual precipitation is extremely uneven; in terms of tendencies of seasonal precipitation, winter and spring have upward trends while summer and autumn have downward tendencies; distinctions in tendencies, ranges and decadal precipitation anomalies among each seasons are in existence within each decade during 1961–2000. The periodical oscillations of each seasonal precipitation time series are also evident. The research results not only provide convincing evidence for global climate change research, but also facilitate the understanding of specific natural process and pattern to make steps to rehabilitate and reconstruct vegetation, and contribute to fulfill the sustainability of water management. [ABSTRACT FROM AUTHOR]

The source region of the Yangtze River (SRYR) is located in the hinterland of the Tibetan Plateau (TP). Due to the harsh climate environment, there are few meteorological stations in its territory, and the measured meteorological data are also less. To overcome the impact of lack of measured meteorological data, the China Meteorological Forcing Dataset (CMFD) was used to couple with the meteorological data, to make the meteorological data more representative of the average climate state of the SRYR. Furthermore, we used the Soil and Water Assessment Tool (SWAT) to verify interpolation effect of meteorological data. Then the six global climate models (GCMs) were integrated through deep learning (DL) algorithm to make it closer to the changes in weather data after correction. The future water resource changes of SRYR were obtained by coupling the SWAT model with the integrated meteorological data. The results show that the CMFD dataset has a high precision in the SRYR, and that the average relative error (RE), coefficient of determination (R2), Nash–Sutcliffe efficiency (Ens) with the measured temperature and precipitation are 10.66%, 0.99, and 0.93, respectively. The CMFD dataset can be used for meteorological data integration. After the meteorological data integration, the Ens between simulated runoff and observed runoff increased from 0.64 to 0.70, and the RE reduced from 13.4 to 10.3%. Under the future climate scenario, the runoff in the SRYR shows a decreasing trend, the average annual runoff decreased by 11.89%, and the distribution of runoff during the year changes is even more dramatic. This shows that the SRYR faces the risk of water resources reduction, which will bring challenges to water resources management in the SRYR. This study provides a new idea for meteorological data correction. [ABSTRACT FROM AUTHOR]

Soil organic carbon (SOC) sequestration is closely linked to global climate change and soil quality. Secondary succession of agricultural abandonment under the Grain for Green Project (GGP) program generally promotes SOC sequestration in the karst region of southwestern China. This study investigated the controlling mechanism of enhancing SOC sequestration during secondary succession of agricultural abandonment, based on soil aggregation, soil erosion, and soil Ca dynamic. In the study area, croplands, shrub-grass lands, and secondary forest lands were regarded as the three stages during the secondary succession of cropland abandonment by the space-for-time substitution method. The proportions of water-stable and different-sized aggregates, SOC contents associated with aggregates, soil Ca contents and Ca/Al ratios, and soil erodibility K factors were analyzed in the soils at the 0–10, 10–20, and 20–30 cm depths. The proportions of macro-aggregates at the 0–10 cm depth in the croplands (mean 61.3%) were significantly lower than those in the shrub-grass lands (mean 78.5%) and secondary forest lands (mean 81.6%). The SOC contents associated with macro-aggregates at the 0–20 cm depth in the croplands (mean 30.5 g kg–1) were significantly lower than those in the secondary forest lands (mean 52.2 g kg–1) but were slightly (not significantly) lower than those under the shrub-grass lands (mean 38.6 g kg–1). Soil Ca/Al ratios at the 0–20 cm depth in the croplands (mean 0.087) and shrub-grass lands (mean 0.105) were significantly lower than those under the secondary forest lands (mean 0.63). The proportions of water-stable aggregates increased and the K factor decreased after cropland abandonment. These results indicated that under the experiment conditions, soil aggregation increased, soil erosion reduced, and soil Ca accumulated during the secondary succession of agricultural abandonment. A conceptual model for enhancing SOC sequestration during the secondary succession of agricultural abandonment was proposed. This conceptual model suggests that the GGP program has a positive effect on SOC sequestration and soil quality in the karst region. [ABSTRACT FROM AUTHOR]

In this study, the temporal and spatial characteristics of extreme climate from 1961 to 2017 were analyzed using daily precipitation and temperature data from 24 meteorological stations in the Qilian Mountain area, northwestern China. The results showed that warming accelerated considerably after 1985, particularly during the 1990s. The warming trend then increased after 2000 and further increased after 2010. The Qilian Mountains and the Hexi and Qaidam Inland River Basins greatly affected the Atlantic Multidecadal Oscillation (AMO), Northern Tropical Atlantic Index (NTA), Caribbean sea-level surface temperature (SST) Index (CAR), South China Sea Summer Monsoon Index (SCSSMI), and South American Summer Monsoon Index (SAMSMI). The circulation index on the extreme temperature warm index was stronger than that of the extreme temperature cold index. There were greater increases in all extreme indexes in the central part of the Qilian Mountain area, and the region of increase decreased from inside to outside. The interannual change in the warming index of extreme temperature was similar to that of the cold index of extreme temperature. TX10, TN10, ice days (ID), and frost days (FD) showed significant negative correlations with altitude, whereas TXN and TNN showed significant positive correlations with altitude. Changes in TX10, TN10, TXN, TNN, ID, FD, and diurnal temperature range were most noticeable in high-altitude areas (> 2500 m), whereas changes in TN90, TX90, TXX, TNX, and growing season length were most noticeable in low altitude areas (< 2500 m). The Qilian Mountain area and the Hexi and Qaidam Inland River Basins were greatly affected by the AMO, NTA, CAR, SCSSMI, and SAMSMI; however, they were only slightly affected by the Nino4, Northern Atlantic Oscillation, North Pacific model, Southern Oscillation Index, Arctic Oscillation, and Multiple ENSO Index. The effect of the circulation index of Atlantic Multidecadal Oscillation, Tropical Northern Atlantic Index, Tropical Southern Atlantic Index, North Tropical Atlantic SST Index, and CAR on the extreme temperature warm index was stronger than that of the extreme temperature cold index. [ABSTRACT FROM AUTHOR]

In this study, the temporal and spatial characteristics of extreme climate from 1961 to 2017 were analyzed using daily precipitation and temperature data from 24 meteorological stations in the Qilian Mountain area, northwestern China. The results showed that warming accelerated considerably after 1985, particularly during the 1990s. The warming trend then increased after 2000 and further increased after 2010. The Qilian Mountains and the Hexi and Qaidam Inland River Basins greatly affected the Atlantic Multidecadal Oscillation (AMO), Northern Tropical Atlantic Index (NTA), Caribbean sea-level surface temperature (SST) Index (CAR), South China Sea Summer Monsoon Index (SCSSMI), and South American Summer Monsoon Index (SAMSMI). The circulation index on the extreme temperature warm index was stronger than that of the extreme temperature cold index. There were greater increases in all extreme indexes in the central part of the Qilian Mountain area, and the region of increase decreased from inside to outside. The interannual change in the warming index of extreme temperature was similar to that of the cold index of extreme temperature. TX10, TN10, ice days (ID), and frost days (FD) showed significant negative correlations with altitude, whereas TXN and TNN showed significant positive correlations with altitude. Changes in TX10, TN10, TXN, TNN, ID, FD, and diurnal temperature range were most noticeable in high-altitude areas (> 2500 m), whereas changes in TN90, TX90, TXX, TNX, and growing season length were most noticeable in low altitude areas (< 2500 m). The Qilian Mountain area and the Hexi and Qaidam Inland River Basins were greatly affected by the AMO, NTA, CAR, SCSSMI, and SAMSMI; however, they were only slightly affected by the Nino4, Northern Atlantic Oscillation, North Pacific model, Southern Oscillation Index, Arctic Oscillation, and Multiple ENSO Index. The effect of the circulation index of Atlantic Multidecadal Oscillation, Tropical Northern Atlantic Index, Tropical Southern Atlantic Index, North Tropical Atlantic SST Index, and CAR on the extreme temperature warm index was stronger than that of the extreme temperature cold index. [ABSTRACT FROM AUTHOR]

As an important indicator of vegetation coverage, the normalized difference vegetation index (NDVI) reflects the changing pattern and evolving trend of the environment. In the Loess Plateau, vegetation plays a critical role in soil and water conservation, which strongly affects the achievement of sustainable development goals. The study of the spatial distribution and temporal trends of NDVI is of great practical importance for the planning of soil and water conservation measures and the evaluation of the environmental situation. In this study, the NDVI, precipitation, land use and land cover data of the Jing River Basin were collected, the emerging hot spot patterns of the NDVI analyzed, the characteristics of spatial distribution and temporal variation of the NDVI in the basin obtained, and the impacts on NDVI from the climate changes and the land cover changes discussed. The results show that the NDVI in Jing River Basin represents a spatial trend of decreasing from northwest to southeast. The emerging hot spot analysis results show that diminishing cold spot, oscillating hot spot and intensifying hot spot are predominant patterns in the basin. The whole basin shows a statistically significant upward trend of high value aggregation of NDVI. The temporal trend of NDVI in the basin varies from − 0.0171 to 0.0185 per year. The increasing trend of vegetation coverage in the basin is statistically significant. The positive correlation between the NDVI and the precipitation mainly observed upstream of the basin reveals that the growth of vegetation in the Loess Plateau is more dependent on the water supply from the precipitation. Land cover transition patterns and the land use patterns also impact the spatial–temporal trends of the vegetation coverage in the basin. The study results may be helpful for the vegetation restoration, soil and water conservation and sustainable development of the Jing River Basin. [ABSTRACT FROM AUTHOR]

Coal is the most important primary energy in China. Although the proportion of coal in China's total energy consumption continues to decline it will still be the main energy in China for a long time in the future. As the largest contributor to China's greenhouse gas emissions, the energy conservation and emission reduction of coal industry will be the most critical step for China to cope with global climate change and solve environmental problems at present and in the future for a long time. The object of this study was coal mining in China. Life cycle assessment (LCA) was used to quantify carbon emissions in whole process of coal mining, including mining, ventilation, drainage, power consumption, transportation, and post-mining activities. The analysis result shows that the carbon emissions of producing tons of coal are 164.403 kg of carbon dioxide equivalent per ton. The analysis further emphasizes that the methane contributes the most, accounting for 62.21% of the total emissions, and plays an important role in the full life cycle of coal mining. Therefore, it presents a potential to mitigate the environmental impact of coal mining, and its main task is to recover and recycle methane. Based on the technical level, this study puts forward the low-carbon development countermeasures for coal enterprises. Then the technical system of methane emission control and utilization is constructed from three aspects: coal-bed methane development, gas extraction, and utilization and gas utilization. Finally, a trinity resource utilization system of coal mine gas is constructed. This study hopes to help practitioners to realize the importance of coal mine methane to the coal mining process. If the efficient resource utilization of methane be realized, it could not only save energy and reduce emissions in coal enterprises, but also promote the safety production of coal mines and improve the economic benefits of coal mines. It is also of great significance for optimizing China's energy structure, realizing low-carbon transformation, and safeguarding China's strategic energy security. [ABSTRACT FROM AUTHOR]

The aim of our study is to quantify the relationship between ecosystem and climate variables in southwest China. We further examined spatiotemporal distribution patterns of daily reference evapotranspiration (ET0) and ecosystem types through integrated approaches, including spatiotemporal interpolation, Penman–Monteith, Mann–Kendall test, statistical correlation analysis and transition matrix based on those datasets including observation climate data, satellite remote sensing images (MODIS and Landsat) and observed ecosystem data. The following results are achieved. First, changes of ET0 were greatly influenced by the combined effects of precipitation (with a decrease rate of −13 mm/10 years) and temperature (with a decrease rate of + 0.17 ℃/10 years). The annual average ET0 increased by + 2.1 mm/10 years, and the increased ET0 are more than 25% of the total area. Second, evapotranspiration was regarded as a sensitive indicator of climate and ecosystem feedbacks, and these ecosystem types have a great transformation, including forest, agriculture, and grass. Forest and grass were distributed primarily in the southern and eastern mountain areas, grass was in high mountains area while agriculture was prevalent in basin areas respond to climate changes. The area of forest converted to grass was 3670 km2, which was greater than transition from grass to forest (1720 km2). Correlation coefficients of evapotranspiration and NDVI were positive in forest and negative in agriculture. Third, the effects of these changes on climate vegetation and ecosystem process feedbacks on the quickly warming southwest China are potentially significant. Although the variation in ecosystem types was combined effects caused by climate variation and human activities, an effective ecological restoration program "Grain for Green" has improved the environmental conditions in southwest China. [ABSTRACT FROM AUTHOR]

Lakes play a vital role in keeping the balance of regional ecosystems and biodiversity. In regions such as the Qinghai–Tibet Plateau with the fragile natural environment, lakes appear to be highly sensitive to climate changing. In the Golmud Basin, which is situated on the north edge of the Qinghai–Tibet Plateau, the interactions among lakes area variations, climate change and anthropogenic interference have not been thoroughly investigated. In this study, we analyzed lakes area variations in the Golmud Basin using Landsat-TM/ETM image data from 1980 to 2015. Within the study period, the lakes in the area have undergone two cycles with four stages: expansion in 1980–1990, shrinkage in 1990–2005, expansion in 2005–2010, and shrinkage in 2010–2015 again. In 2009, the Qarhan Salt Lake was basically enlarged and connected to the neighboring small lakes, while Dabuxun Lake had its maximum area in 2010. From 2011 to 2015, East Taijinaier Lake was shrinking and nearly dried up due to excessive water, mineral exploitation, and human blocking the connection among rivers and lakes. Climatic data were analyzed via the Mann–Kendall trend test, and both annual temperature and precipitation in the Golmud City increased considerably. The Landsat-TM/ETM images showed that the mountain glaciers around the basin retreated from 1980 to 2015, resulting in the expansion of the lake area. The land use transfer matrix was used to obtain the changes in land use types; increasing water consumption and population growth are the main factors associated with decreased lakes area and vegetation cover. As an essential part of the ecological environment, lakes have a direct impact on the change of the ecological environment. This study provides a scientific basis for the evaluation of the ecological environment quality of the Golmud Basin. [ABSTRACT FROM AUTHOR]

Accurate estimation of groundwater recharge is critical for evaluating the available freshwater resources in the Heihe River basin. Based on the statistical downscaling method coupled with the soil and water assessment tool, this study predicted the variations in precipitation, surface runoff, lateral flow, evapotranspiration, and groundwater recharge in the Heihe River basin under the A1B scenarios in the future 45 years (2019–2063). It was found that relative errors (Re), coefficient of determination (R2), and coefficient of Nash–Sutcliffe efficiency (Ens) at calibration and validation period were 19%, 0.90, 0.82 and 12%, 0.83, 0.75, respectively. These results indicated that the new SWAT models can be properly applied for predictions in the Heihe River basin. The next 45 years were divided into four stages, and precipitation change will follow the order stage III > stage I > stage IV > stage II. In addition, temperatures will gradually increase with time. Precipitation and evapotranspiration will be the major input and output of water resources, respectively. The surface runoff value with large precipitation stage will be nearly six times that of lateral flow. The daily highest temperature affects evapotranspiration, and the temporal variation rate of evapotranspiration is low because of extensive distribution of forests and grasslands. The groundwater recharge will reach a maximum in 2037–2046, which will be nearly two times that in 2019–2029. Groundwater recharge will be small in both 2047–2063 and 2030–2036. Precipitation is a major influence factor on groundwater recharge, but temperature slightly affects groundwater recharge. Underlying surface conditions such as land use, soil type, and properties also affect groundwater recharge. The precipitation after 2047 will not be very large, and temperatures will be high, and large evapotranspiration will lead to a rapid decrease in groundwater recharge. [ABSTRACT FROM AUTHOR]

Floodwater resource utilization, a new term or concept was proposed in the early 21st century in China, and has been practiced over the past 20 years in order to adapt to the uncertain effects of climate change on regional droughts and water scarcity. The applications shown that the effect was good and necessary to alleviate the regional water shortage. This special thematic issue collected 14 articles covering three continents—Asia, America and Europe in term of research area, which come down to basic concepts, evaluation methods, utilization models and usable patterns and so on. Through this thematic issue, the lessons, experiences, and achievements on floodwater resources utilization achieved mainly in China can be shared with world audiences, especially to regions affected by the monsoon climate, with similar hydrologic characteristics and water resource needs as in China. [ABSTRACT FROM AUTHOR]

The Tibetan Plateau (TP) is particularly sensitive to the influences of climate change. As indicators of climate change, lakes on the TP play a key role in the Earth's climatic system. Lake Yazi (LY), Lake Tuohepingco (LT) and Lake Changtiao (LC) in the Tuohepingco Basin are three inland lakes on the plateau. The extents of LY, LT and LC were obtained using object-based image analysis for remote sensing and 22 images from Landsat satellites (from September to December between 1972 and 2015). Inter-annual changes in the extent of LY, LT and LC were then analyzed. The results show that the total area of the three lakes underwent a change from shrinkage to expansion between 1972 and 2015. In general, there was a trend toward shrinkage during 1972-1999, distinct expansion during 2000-2007 and slight expansion during 2008-2015. Moreover, we found that 14 other lakes have also expanded dramatically since 2000. Lakes at 30°N and 35°N (LY, LT and LC are also located in this region) exhibited the same dramatic period of expansion between 2000 and 2005. In other words, 2000 appears to be a critical transition point for changes in lake size on the TP. Lakes at the same latitudes in the Tibetan Plateau interior may have a similar period of dramatic expansion after 2000. The warming-triggered deglaciation or permafrost degradation, increased precipitation and decreased evapotranspiration may be the influencing factors of lake expansion in the Tuohepingco Basin. Temperature showed relatively higher correlation with lake extent, while precipitation and evaporation were slightly correlated with lake area. Given the importance of wetlands to human society, these are no trivial issues, and we now need accelerated research based on long-term and continuous remote sensing. [ABSTRACT FROM AUTHOR]

Climate change as a result of the increased greenhouse gas emissions may influence the availability of water resources in many regions on the globe. In the past decades, China has been facing severe shortage of water resources. This study focuses on the assessment of the impact of climate change on both blue and green water resources in ten large river basins in China. The blue and green water resources for these river basins were derived from the terrestrial hydrological fluxes in period 1960-2100, which were simulated with the Max Planck Institute Hydrological Model-MPI-HM. The forcing data for the hydrological model, the precipitation and temperature were obtained from three coupled Atmosphere-Ocean General Circulation Models (GCMs)-ECHAM5, IPSL and CNRM, under A2 and B1 greenhouse gas emission scenarios. The statistical bias correction method was applied on the output from the three GCMs. By using this climate model-hydrology model modeling chain, the impact of climate change on the blue and green water resources was analyzed over the ten Chinese river basins. Here, the projected changes in 2071-2100 are considered relative to 1971-2000. The projected change of monthly mean and annual mean of green water resources show the general increase for all ten river basins; among them, Inland river, Zhemin river and Zhujiang river have larger change signal than other basins. For blue water resources, increases of the annual mean are projected from November to March for Heilongjiang river, Liaohe river and Yellow river, Inland river in Northern China; and decreases are projected for Huaihe river, Zhemin river, Haihe river, Yangzi river, Southwest river, and Zhujiang river basins in Southern China. It is found that climate change has impact on both blue and green water resources over large river basins in China. The sustainable blue water resources management should take into account the different changes in both Northern and Southern China. The results show that a better management of green water resources is of importance for food and ecological securities in the context of global change. [ABSTRACT FROM AUTHOR]

Since the late 1970s, the Chinese government has implemented massive afforestation projects to address grievous environmental disasters, protect human health and provide long-term environmental security. Having a better understanding of the total carbon sink from the afforestation projects is fundamental to assess its global carbon benefit. Here, the sequestered carbon stock based on Chinese national forest inventory data is calculated by using three comparable volume-derived biomass models. Results show that the carbon sink contribution from these Chinese afforestation projects was 1.02 Pg C by the end of 2008 and 0.79 Pg C on average from 1981 to 2008 with a cumulative rate of 0.028 Pg C/a, which corresponds to 2 % of the total industrial carbon emissions from China during the same period. The financial value of carbon sequestration from these projects can be estimated by its value in carbon taxes of Finland and is potentially 190 billion RMB from 1981 to 2008, which is 43.4 % of the original investment. Hence although China's afforestation projects make only modest contributions to offsetting industrial growth in carbon, the carbon sequestered, if valued according to some markets, is a significant fraction of the total project costs. [ABSTRACT FROM AUTHOR]

A sediment core from Lake Barkol located in the eastern Xinjiang autonomous region, northwest China, provided a high-resolution record of environmental change covering the last ~8.6 cal ka BP. Three major climate stages, 8.6-7.1, 7.1-2.0 and from 2.0 cal ka BP to the present, were divided by grain size and the authigenic carbonate stable isotope of the lake sediment. Climatic drought during the period 7.1-4.5 cal ka BP, deduced from Lake Barkol, prevailed in the mid-Holocene climate in northern Xinjiang and northwest Mongolia. In contrast, it was wet in central Xinjiang, northwest India and the Middle East during the same period. The climatic difference between northern and southern arid central Asia demonstrates the southward shifting of the Westerlies, which indicates the potential contribution of the Siberian high in the mid-Holocene. [ABSTRACT FROM AUTHOR]

Glaciers on the Tibetan Plateau are undergoing an accelerating retreat under climatic warming, with the immediate result of glacial lake outburst floods (GLOFs) becoming increasingly frequent. Glacial lakes in the southeast of the Tibetan Plateau are densely distributed. Due to the difficulties associated with field investigations of glacial lakes, including remote locations and harsh weather conditions, methods which combine remote sensing, geographic information systems and hydrodynamic modeling (HEC-RAS) with field investigation were developed to assess regional glacial lake variation and hazard. The methods can be divided into three levels. At the first level, multi-temporal satellite images were used to (1) study the variation of glacial lakes for the whole region during recent decades, as well as (2) qualitatively identify potentially dangerous glacial lakes (PDGLs). The second level is an in-depth evaluation of the degree of danger for selected PDGLs by ground-based surveys, and then verification of the first-level results. At the third level, the one-dimensional (1D) hydrodynamic model HEC-RAS was used to simulate the inundation characteristics of hypothetical outburst of PDGLs. The three levels downscale from the whole study area to individual PDGLs, and thus assess the hazard of glacial lakes progressively. The methods were then applied to a region of southeastern Tibet-the Boshula mountain range-to analyze the variation of glacial lakes and assess potential hazards posed by GLOFs. Since these methods employ easily accessible data and instruments, the application in other regions is promising. [ABSTRACT FROM AUTHOR]

Plant diversity-productivity relationship is a debated issue in ecology. However, different relationships between plant diversity and productivity have been observed in response to changes of environmental factors. In this study, vegetation cover, species richness, above-ground net primary productivity (ANPP), soil organic carbon (C) and total nitrogen (N) were measured at three stages of dune stabilization (mobile dune, semi-fixed dune and fixed dune) in Horqin Sand Land, Northern China. Relationships between species richness and ANPP were also examined at different stages of dune stabilization. Results showed that vegetation cover, species richness, ANPP, soil organic C and total N increased with dune stabilization. Half U-shaped, positive and no relationship between species richness and ANPP were found in mobile dune, semi-fixed dune and fixed dune, respectively. Species richness was significantly positively correlated to soil organic C and total N in mobile dune and semi-fixed dune, and ANPP was positively correlated to soil organic C and total N in fixed dune. A positive relationship between species richness and ANPP was also found along the habitat gradient of dune stabilization. These results suggest that dune stabilization following restoration succession of degraded vegetation greatly influences relationships between species richness and ANPP in sand dune ecosystems. Soil organic C and total N determining changes of vegetation cover, species richness and ANPP drive the positive relationship between species richness and ANPP along the dune stabilization gradient. Thus, the degree of dune stabilization and vegetation composition, influenced by important soil properties, are important factors to determine relationships between plant diversity and productivity in sand dune ecosystems. [ABSTRACT FROM AUTHOR]

The Chinese loess-paleosol succession, deep-sea sedimentary sequences and ice cores are the three types of paleoclimatic records. Measurements were made of the ancient climatic proxies of magnetic susceptibility, median diameter of grain size and content >40 μm, and the CaCO content of samples collected at 1 cm depth intervals in the fourth paleosol layer of the Luochuan loess-paleosol section on the Chinese Loess Plateau. Wavelet analysis of the data identified cycles of climate change, which were compared to the marine δO record of SPECMAP. The results showed that: (1) when the fourth paleosol layer was forming, the paleoclimate was relatively stable but five extreme climatic events were identifiable as occurring around 408, 381, 376, 368 and 361 kaBP; (2) two of these regional events differed from the global trend; (3) during marine isotope stage (MIS)11, the fourth paleosol layer of the Luochuan loess section recorded a regional quasi-19 ka climatic sub-cycle and (4) this sub-cycle was also reflected globally in the SPECMAP data indicating that, during MIS11, this sub-cycle was regionally and globally synchronized. [ABSTRACT FROM AUTHOR]

Climate model has become an irreplaceable tool for the study and prediction of climate changes. The land surface process, as one of the important parts of all climate models, must be considered so that the simulative ability of climate models could be improved. Using the common land model (CoLM) that is driven by the LOPEX experiment data, the characteristics of land surface processes of the Loess Plateau are simulated. Furthermore, based on the comparison of the field observation data with the simulated results, the simulative performance of CoLM in the Loess Plateau region is also examined. The results show that, CoLM can be used in the Loess Plateau, and it perfectly simulates net radiations and net short-wave radiations. However, the simulated land-surface temperature is slightly higher than actual measured value, while the simulated soil temperature values in lower layers (5, 10, 20, 40 cm) are relatively less and the variety phase of these also lag. Moreover, the simulated sensible heat flux is a little larger, while the simulated soil thermal conductivity value is obviously lower. By modifying the calculation plan of soil thermal conductivity, the simulated result has been greatly improved. As a whole, if CoLM is applied in the Loess Plateau of Northwestern China, the parameterization of soil thermal conductivity should be ameliorated, which can improve its simulative capacity in the Loess Plateau regions. [ABSTRACT FROM AUTHOR]

A series of experiments to determine the direct emission of dust-sized particles from Gobi surfaces by clean wind (wind without sand), and the potential for aeolian abrasion of Gobi surfaces and beds of gravel and mobile sand to produce fine (<100 μm) and dust-sized (<10 μm, PM) particles under sand-laden winds were conducted. Parent material was obtained from Gobi areas of the Ala Shan Plateau, the region with high dust emissions in arid China. The fine particles produced by aeolian processes were collected using sand traps and sieved the captured materials to exclude particles >100 μm in diameter and then PM by sedimentation was acquired. The Gobi surface provided most of the emitted fine particles during the initial dust emission processes, but subsequently, release of the clay coatings of particles by abrasion becomes the dominant source of fine materials. Under sand-laden winds, PM production rates produced by aeolian abrasion of Gobi surfaces ranged between 0.002 and 0.244% of blown materials. After removal of sand, silt, or clay with low resistance to erosion from the Gobi surfaces by the wind, the PM production rates caused by aeolian abrasion were similar to those from gravel and sand beds. The results also indicated that after the dust-sized particles with low resistance to erosion were removed, the production of dust-sized particles was unrelated to wind velocity. Under aeolian processes, Gobi deserts in this region therefore play a major role in dust emissions from arid and semiarid China. [ABSTRACT FROM AUTHOR]

The Songhua River plays a key role in the national development of China, owing to its unique natural condition and resources. Recent changes in the streamflow in the Songhua River are important with regard to local sustainable development and management under the background of global warming and aggravating soil erosion. In order to detect changes in the streamflow, two streamflow series from 1955 to 2004 (observed at the Harbin and Jiamusi stations) in the mainstream of Songhua River basin were obtained, and methods of statistical analysis, wavelet transform, and double mass analysis were employed to analyze the data. Reasons for the changes to the streamflow are discussed with respect to natural and man-made drivers. The results show the following: (1) From 1955 to 2004, the streamflow series present obvious declining trends. (2) The streamflow series followed the pattern of a wet-dry-wet-dry cycle pattern over the past 50 years. In the mainstream of Songhua River, wet years mainly occurred during the periods of 1955-1966 and 1984-1993, while dry years mainly occurred in the 1970s and after 2000. (3) Within the 50-year scale, the streamflow series appeared in the main periods of circa 33-, 13- and 4-year, in which the 33-year periodicity is the strongest. (4) Precipitation and temperature directly influenced the streamflow in the mainstream of the basin. The discharge was positively correlated with the precipitation and negatively correlated with the temperature. In addition, human activity was another important driving factor for streamflow change. (5) In the mainstream of Songhua River basin, the influences on streamflow can be divided into three periods: 1955-1976, 1977-1997, and 1998-2004. In the first period climate change played a dominant role, and during the latter two periods human influences were enhanced significantly. [ABSTRACT FROM AUTHOR]

n intensive investigation of the spatial and temporal variations of δD and δO in precipitation was conducted during 2002–2004 in six sites in the Heihe River Basin, Northwestern China. The δD and δO values for 301 precipitation samples ranged from +59 to −254 and +6.5 to −33.4‰, respectively. The relationship between δD and δO defines a well-constrained line given by $$ \delta D = 7.82\delta {}^{18}{\text{O}} + 7.63 $$, which is nearly identical to the meteoric water line in the Northern China. This wide range indicates that stable isotopes in precipitation were primarily controlled by different condensation mechanisms as a function of air temperature and varying sources of moisture. The results of backward trajectory of each precipitation day at Xishui show that the moisture of the precipitation in cold season (October–March) mainly originated from the west while the moisture source was more complicated in warm season (April–September). The simulation of seasonal δO variation shows that the stable isotope composition of precipitation tended to a clear sine-wave seasonal variation. The spatial variation of δO shows that the weighted average δO values decreases with the increasing altitude of sampling sites. The great difference of air temperature which led to the differences of condensation mechanisms and local recycled continental moisture may have influence upon the isotopic composition of rain events in different sites. [ABSTRACT FROM AUTHOR]

The Loess Plateau, the transitional zone between humid and arid regions of China, is an important region to examine the regional hydrological cycle and variation in humid and arid regions under global climate change. Aridity index (AI), the ratio of precipitation (P) to potential evapotranspiration (ET0), is an important indicator of regional climate conditions and is also used to classify drylands. In this study, data from 51 national meteorological stations during the period of 1961-2014 were collected to estimate the AI in the Loess Plateau. Results show that a downward trend in annual AI was detected and the boundary of the drylands region based on the AI was expanded across the Loess Plateau over the period of 1961-2014. The spatiotemporal variability of P was the main cause in the AI variations. Furthermore, data analysis suggested the occurrences of the extreme minimum AI values were mostly affected by fluctuations of the two factors (ET0 and P) rather than its corresponding trend during the period. Thus, this study indicated the major driving factor of AI and the relationship between extreme AI values and the global climate anomalies in the Loess Plateau region, and meanwhile, provided an understanding of the impacts of climate change on hydrological cycle in the Loess Plateau of China. [ABSTRACT FROM AUTHOR]