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Ecosystem health (EH) is important for ensuring sustainable development, and the main goal of environmental protection and governance, especially for ecological fragile areas. Scientific assessment of EH can improve decision-making ability and inform sustainable development. In this paper, the effects of natural and social environment were integrated to reflect the characteristics of EH based on a comprehensive assessment system including ecosystem vigor (EV), ecosystem organization (EO), ecosystem resilience (ER), and the ratio of supply to demand of ecosystem services (ESDR) from the perspectives of ecological integrity and human demand for ecosystem services (ES). The Entire-Array-Polygon (EAP) method was applied to calculate an ecosystem health index (EHI) and analyze spatio-temporal change from 2000 to 2020 in Hexi Corridor (HC), Northwest China. The results showed that: (1) The spatial distribution of EV, EO, ER, and ESDR was generally consistent, with a low spatial distribution in the northwest and high in the southeast, the values showed an overall increasing trend from 2000 to 2020. (2) The spatial distribution of EHI was high in the northwest and central regions, and low in the southwest, reflected a moderate health level. The proportion of area with well and relatively well health was increasing, which indicated that EH showed an improving trend. (3) The significantly decrease areas of EHI were mainly located in urban areas, and the increases areas were mainly located outside of urban areas. The distribution of the EH condition has obvious orientation characteristics. The results of the study provide theoretical and practical implications for regional ecological conservation and management.

The Suhai Lake Basin has held major ecological status as a crucial component of the Qinghai-Tibet Plateau’s ecological security barrier. The Suhai Lake Migratory Bird Nature Reserve’s safety and the livelihood of Kazakh citizens are now directly endangered by the frequent switching between land-use types and the decrease of ecosystem service functions caused by climate change and human activity. As a result, this work introduces the idea of land-use transfer flow. Through the application of interval level change and the land-use transfer chain, the process, affecting factors, and current issues of land-use change in the Suhai Lake Basin over the past 40 years are thoroughly investigated. The results showed that the intensity of land-use change was significant, at 0.055%, during the period 1990–2000, whereas the grassland area significantly increased, with a net increase of 23.07 km2, mainly from the conversion of saline-alkali land, swamp, and other unused land in the middle and lower reaches. The key factor influencing the growth of the grassland throughout this time has been the ecological management policy. As a result of the climate’s ongoing warming between 2000 and 2018, glacial meltwater and precipitation increased, the middle and lower ranges of the groundwater table rose, and the grassland degradation, swamp shrinkage, and soil salinization in the watershed all worsened. The degradation of grassland will result from both overgrazing and overprotection. Suhai Lake Wetland and Haizi Grassland Wetland are the most readily apparent examples of land-use changes in the Suhai Lake Basin from a spatial perspective. More consideration should be given to the ecological deterioration and land exposure in the glacier retreat zone of the upstream source region. The results can provide important information on the impact of regional development and the environmental governance policies of the changes in land use/cover in the Suhai Lake Basin.

We have established a stable water isotope monitoring network in the Shiyang River Basin in China’arid northwest. The basin is characterized by low precipitation, high evaporation and dense population. It is the basin with the most significant ecological pressure and the greatest water resources shortage in China. The monitoring station covers the upper, middle and lower reaches of the river basin, with six observation systems: river source area, oasis area, reservoir canal system area, oasis farmland area, ecological restoration area, and salinized area. All data in the data set are differentiated by water body types (precipitation, river water, lake water, groundwater, soil water, plant water). The data set is updated annually to gradually improve each observation system and increase data from observation points. So far, the data have been obtained for five consecutive years. The data set includes stable isotope data, meteorological data and hydrological data in the Shiyang River Basin. The data set can analyze the relationship between different water bodies and water circulation in the Shiyang River Basin. This observation network’s construction provides us with stable water isotopes data and hydrometeorological data, and we can use theae data for hydrological and meteorological related scientific research. It can also provide a scientific basis for water resources utilization, water conservancy project construction, and ecological environment restoration decision-making in China’s arid areas. The data that support the findings of this study are openly available in Zhu (2021) at “Data sets of Stable water isotope monitoring network of different water bodies in Shiyang River Basin, a typical arid river in China (Supplemental Edition)”, Mendeley Data, V1, doi: 10.17632/w5rpxwf99g.1.

Monthly runoff data of six hydrological control stations in Shiyang River Basin from 1961 to 2016

Drought is the most widespread natural disaster in the world. How to monitor regional drought scientifically and accurately has become a hot topic for many scholars. In this paper, Geographically Integrated Dryness Index (GIDI) was integrated from an assortment source including Precipitation Condition Index (PCI), Temperature Condition Index (TCI), Soil Moisture Condition Index (SMCI), Vegetation Condition Index (VCI), and Standardized Precipitation Evapotranspiration Index (SPEI) (as the dependent variable) based on geographically weighted regression method. Besides, the comprehensive drought situation and changing trends in China from 2001 to 2019 were also examined. The results showed that (1) GIDI has excellent performance in monitoring medium- and long-term droughts and the monitoring results shows 2003, 2016, and 2019 were relatively wet years, while 2007, 2009, and 2011 were major drought years, and spring and March were the most frequent droughts season and month, respectively, and (2) except for the middle and upper reaches of the Yellow River and Northeastern China, which have a tendency to become wet, other places have a tendency to fluctuating dry. This study took advantage of simple and efficient methods to integrate existing indices to obtain a new index for monitoring a wider range of droughts, taking into account the physical mechanism of drought formation and the time scale of drought development, so it can scientifically evaluate the spatial and temporal distribution characteristics of drought and changes.

In northern China, precipitation fluctuates greatly and drought occurs frequently, which mark some of the important threats to agricultural and animal husbandry production. Understanding the meteorological dry-wet change and the evolution law of drought events in northern China has guiding significance for regional disaster prevention and mitigation. Based on the standardized precipitation index (SPI), this paper explored the spatio-temporal evolution of meteorological dry-wet in northern China. Our results showed that arid area (AA) and semi-arid area (SAA) in the west showed a trend of wetting at inter-annual and seasonal scales, while humid area (HA) and semi-humid area (SHA) in the east showed a different dry-wet changing trend at different seasons under the background of inter-annual drying. AA and HA showed obvious “reverse fluctuation” characteristics in summer. The drought frequency (DF) and drought intensity (DI) were high in the east and low in the west, and there was no significant difference in drought duration (DD) and drought severity (DS) between east and west. The DD, DS and DI of AA and SAA showed a decreasing trend, while the DD and DS of HA and SHA showed a slight increasing trend, and the DS decreased. In summer and autumn, the main influencing factors of drying in the east and wetting in the west were PNA, WP, PDO and TP1, and the fluctuations of NAO-SOI, NAO-AMO and PNA-NINO3.4 jointly determined the characteristics of SPI3 reverse fluctuations of HA and AA in summer.

In recent years, remote sensing drought monitoring indices have been gradually developed and have been widely used for global or regional drought monitoring due to their strong drought-monitoring capabilities and easy implementation advantages. However, some defects of remote sensing drought indices stand to be improved due to certain errors in the inversion of surface characteristics by remote sensing datasets. The temperature-vegetation-precipitation drought index (TVPDI) was taken as the research object, and the leaf area index (LAI), the difference between the land surface temperature (LST) and monthly average temperature, and Global Precipitation Measurement (GPM) precipitation data were selected instead of the normalized difference vegetation index (NDVI), LST and tropical rainfall measuring mission (TRMM) data to improve TVPDI. The improved remote sensing drought index was named the improved temperature-vegetation-precipitation drought index (iTVPDI). The drought-monitoring accuracy of iTVPDI was verified by the gross primary productivity (GPP), soil moisture, and crop yield per unit. The drought-monitoring ability of iTVPDI was verified with traditional drought indices, including the standardized precipitation index (SPI), standardized precipitation evapotranspiration index (SPEI), Palmer drought severity index (PDSI), temperature-vegetation drought index (TVDI), drought severity index (DSI) and crop water stress index (CWSI). The drought-monitoring accuracy of iTVPDI was verified by selecting sample areas. iTVPDI was applied to monitor drought in mainland China over the 2001-2020 period and obtained four main results. First, the correlation analyses of iTVPDI and TVPDI with GPP, crop yield per unit area, and soil moisture showed that iTVPDI had a stronger monitoring ability in Northeast, North, and Southwest China; the R

Scientific understanding of regional wind speed variation characteristics and driving mechanisms is of great practical significance to the management and rational utilization of wind energy resources, ecological protection and governance, and sustainable development of agriculture. Taking the Shiyang River Basin in inland river basin of monsoon marginal zone as the study area, this paper analyzed wind speed changes and influencing factors at different time and space scales. The results showed that, first of all, the annual average wind speed showed a downward trend as a whole in Shiyang River Basin, and the change of spring wind speed and the decreasing frequency of daily max-wind speed above Grade 5 were the main contributors. The turning point of annual average wind speed was consistent with that in spring and autumn (1981) and earlier than that in winter and summer (1982). Secondly, as far as the wind speed change tendency rate is concerned, before the turning point, Yongchang area had the largest decline rate with obvious “2000 m effect”, while after the turning point, Wuwei Basin had the largest rise rate with obvious “basin effect”. Focusing on the downstream desert oasis region, the sand-driving wind speed showed a decreasing trend as a whole, and showed a “cliff-like” decline after 1988. The rising trend of sand-driving wind speed after 2014 will pose greater challenges to ecological governance. Finally, under the background of unbalanced global warming, the wind speed changes in different periods were driven by the circulation system changes. In 1970–1981, the decline of the wind speed was the result of the combined action of Arctic Oscillation and Asia Polar Vortex. However, after 1981, it was affected by North Atlantic Oscillation, Asian Meridional Circulation, Tibet Plateau Circulation, India-Burma Trough, Western Pacific Subtropical High and Northern Hemisphere Subtropical High.

Adjusting the agricultural planting structure is one of the important means to realize agricultural water-saving, especially in inland river basin with droughts and water shortages. In this paper, taking Shiyang River Basin in Northwest arid inland river basin as an example, on the basis of determining the crop water production function, a multi-objective optimization model was constructed, which comprehensively considered the maximization of economic benefits, the green water utilization rate and ecological benefits. The optimized planting structure was obtained by using GAMS (General Algebraic Modeling System) model solver. The results showed that: after optimization, the sown areas of wheat, tubers, vegetables and cotton all increased, of which the sown area of tubers increased the most by 8.81×104ha. The sown areas of corn, oil-bearing crops and fruits all decreased, of which the sown area of corn decreased the most by 8.03×104ha. The optimization results of planting structure were different in different counties and districts. The average contribution rate of planting structure adjustment to total water saving was 75.24%, indicating that planting structure adjustment was the key to water-saving. The water consumption of the same crop was different in different counties. Oil-bearing crops and vegetables were more suitable for planting in the lower reaches, while corn and tubers were more suitable for planting in the middle reaches.

The Sugan Lake Basin is located in the inland arid region of northwestern China, in which groundwater is of great significance to human and ecology. Therefore, it is necessary to understand the chemical characteristics and quality of groundwater in the basin. Based on samples collected from 35 groundwater wells in Sugan Lake Basin, the spatial distribution characteristics of groundwater chemistry, main hydrogeochemical processes and groundwater quality have been discussed in this paper by using the multivariate statistics and hydrochemistry analysis methods. The results showed that the groundwater is weakly alkaline, and its total dissolved solid (TDS) and total hardness (TH) are high, with the average values of 1244.03 mg/L and 492.10 mg/L, respectively. The types of groundwater are mainly HCO3−-SO42−-Ca2+ type in the runoff area and Cl−-SO42−-Na+ type in the catchment area. Rock weathering and ion exchange are the main controlling factors of regional groundwater chemistry, followed by evaporative crystallization, and human activities have less impact on groundwater. The spatial difference of groundwater quality is obvious, the water quality of the catchment area is not suitable for drinking, and the suitability for plant growth is also poor. The groundwater in the runoff area can be used for drinking, but the hardness is slightly higher, which is more suitable for ecological purpose.

The headwater region of inland China is immensely important for sustaining livelihoods and maintaining ecological balance, highlighting the need to characterize and assess water quality in this region. The aim of this study is to acquire a comprehensive understanding of the spatiotemporal variation characteristics of river water chemistry and to identify the sources of major ions in the Binggou River Basin, Northwest China. The results show that the water of the Binggou River is neutral freshwater. SO42− is the major anion, Ca2+ is the major cation and the river type is Ca–Na–SO4–HCO3. The concentrations of Na+, Mg2+, SO42−, NO3−, and total dissolved solid are slightly higher than the global average. The seasonal variations of major ion concentrations in the river are highest in winter but lowest in autumn, whereas the spatial variations are greater in the east branch than in the west branch and upstream compared with downstream. Source analysis of the ions indicates that rock weathering is the main source of ions, followed by human activities such as farmland fertilization and coal burning. Water quality analysis shows that the river water is suitable for drinking and irrigation, but the water quality is relatively poor in areas with more human activity, which indicates that human activity greatly influences water quality.

It is the basis of isotope technology application to clarify which factors are related to precipitation isotopes in different regions. China has a vast territory, and there is still no comprehensive and systematic understanding of the spatial distribution pattern and influencing factors of precipitation stable isotopes in China. Based on the known Bowen and Wilkinson model, the latitude and altitude of 117 sites in China were used to simulate δ18O value of each site and to generate the high precision spatial distribution map of the precipitation oxygen stable isotope over China. According to the spatial distribution of precipitation δ18O, the basic effects of isotope variation in different climatic regions were analyzed: latitude effect, elevation effect, temperature effect, precipitation effect, and water vapor source and transportation process. In the eastern monsoon region, the latitude effect of isotope variation is shown, but the difference between the southern region and the northern region is large. The southern region is affected by the water vapor of the subtropical Pacific Ocean and precipitation amount effect to form a high value area of δ18O, and the northern region is more susceptible to the temperature effect. In the same latitude area, due to the influence of local recycled water vapor and local evaporation, a high-value area of δ18O is formed in the inland basin of the northwestern arid region. In the Qinghai–Tibet Plateau, the isotope values affected by the high terrain are generally low. The change of δ18O value reflects the extent to which the south and north areas of the Qinghai–Tibet Plateau are affected by the southwest monsoon and local water vapor.

Drought is a complex natural disaster affected by multiple climate factors and underlying surface. In recent years, drought monitoring indices of remote sensing have been widely applied to monitor drought in a certain region or global. However, some remote sensing drought monitoring indices do not consider the drought-causing factors enough to reflect the comprehensive drought situation of a region fully. In this paper, a new remote sensing drought monitoring index, called Remote Sensing Drought Evaluation Index (RSDEI), was constructed by combining Vegetation Condition Index (VCI), Temperature Condition Index (TCI), Precipitation Condition Index (PCI), and Soil Moisture Condition Index (SMCI) using the spatial principal component analysis (SPCA) method. The reasonableness of RSDEI was test and verified using Net Primary Productivity (NPP), Standardized Precipitation Evapotranspiration Index (SPEI), and unit area crop yield. The RSDEI was also applied to the drought condition monitoring of the northwest arid and semi-arid region from 2001 to 2019.The result demonstrated that the results showed that the RSDEI had a high correlation coefficient with SPEI-12 (R=0.85, p

Many indices are used to monitor drought events. However, different indices have different data requirements and applications. Hence, evaluating their applicability will help to characterize drought events and refine the development of effective drought indices. We constructed different drought indices based on multisource remote sensing data and comprehensively evaluated and compared their applicability for drought monitoring throughout China. The characteristics of drought events in 2009 and 2011 were compared using various drought indices. The different time scales of the Palmer Drought Severity Index (PDSI) and the Standardized Precipitation Index (SPI) were used to evaluate remote sensing drought indices in different regions. Single drought indices, including the Vegetation Condition Index (VCI), the Temperature Condition Index (TCI) derived from Moderate Resolution Imaging Spectroradiometer (MODIS) data, the Precipitation Condition Index (PCI) derived from Tropical Rainfall Measurement Mission (TRMM) data, and the TCI and Soil Moisture Condition Index (SMCI) derived from Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) data, as well as combined drought indices, including the Microwave Integrated Drought Index (MIDI), Optimized Vegetation Drought Index (OVDI), Optimized Meteorological Drought Index (OMDI), Scale Drought Conditions Index (SDCI), and Synthesized Drought Index (SDI), were analyzed and compared to evaluate their applicability. The results showed that different drought indices have specific characteristics under different land use types in China. The VCI and TCI can better monitor long-term drought conditions, but they have a weak correlation with the in situ drought index in forestland and grassland areas. The correlation of SPI-1 with the PCI is higher than that with other single indices, which indicates that the PCI is a good short-term drought index. The SMCI has a better correlation with the short-term in situ drought index, but it is not conducive to drought monitoring in areas such as densely forested land and grassland. The correlations of the in situ drought index with the combined drought indices (the MIDI, OVDI, OMDI, SDCI, and SDI) are better than those with the single drought indices.

Timely and accurate assessments of the spatiotemporal variations and impact factors of CO2 emissions are crucial for developing effective and rational CO2 reduction policies. However, studies are still lacking that consider spatiotemporal variations in CO2 emissions at the grid scale and their impact factors in cities with different types of such emissions. This study proposes an improved estimation model to map the CO2 emissions of mainland China in 2000, 2005, 2010, 2015 and 2018 based on nighttime light data, land use data, and population data. The resulting maps of estimated CO2 emissions in different regions are examined and compared with Landsat data and with the results of linear regression, quadratic polynomial carbon emission models, carbon emission models based on land use and carbon emission models based on population. This comparison shows that the model proposed in this study is more accurate than ordinary models, such as the linear regression and quadratic polynomial models. Using the results of this model, 356 mainland cities in China are divided into service-oriented, industrial, agricultural and comprehensive cities, and the impact factors of each city are analyzed. The results show that China's CO2 emissions are still concentrated in its smaller regions, but the intensity of this concentration is gradually decreasing. The spatial distribution characteristics of the carbon emissions of cities have an obvious circle-layer effect; however, the CO2 emissions of large cities present a “W”-shaped distribution, while the CO2 emissions of small cities present a power function curve. Although GDP is the main factor affecting the CO2 emissions in various cities, the factors affecting different types of cities based on their CO2 emissions vary greatly. These results could improve the current understanding of the patterns of variation and influencing factors of CO2 emissions in different cities and provide a scientific basis for formulating CO2 emission reduction policies in accordance with local conditions.

Carbon storage in the soils on the Qinghai–Tibetan Plateau plays a very important role in the global carbon budget. In the 1990s, a policy of contracting collective grasslands to smaller units was implemented, resulting in a change from the traditional collective grassland management to two new management patterns: a multi-household management pattern (MMP: grassland shared by several households without enclosures) and a single-household management pattern (SMP: grassland enclosed and used by only one household). In 2016, 50 MMP and 54 SMP winter pastures on the Qinghai–Tibetan Plateau were sampled to assess the differences in soil organic carbon (SOC) between the two management patterns. Results showed that average SOC was significantly greater under MMP than under SMP, with an estimated 0.41 Mg C/ha/yr lost due to SMP following the new grassland contract. Based on the government’s grassland policy, four grassland utilization scenarios were developed for both summer and winter pastures. We found that if the grassland were managed under SMP, likely C losses ranged between 0.31 9 107 and 6.15 9 107 Mg C/yr across the Qinghai–Tibetan Plateau relative to MMP, which more closely resembles pre-1990s grassland management. Previous estimates of C losses have only considered land use change (with cover change) and ignored the impacts driven by land management pattern changes (without cover change). The new data suggest that C losses from the Qinghai–Tibetan Plateau are greater than previously estimated, and therefore that the grassland contract policy should be reviewed and SMP households should be encouraged to reunite into the MMP. These findings have potential implications for landm anagement strategies not only on the Qinghai–Tibetan Plateau but also other grazing regions globally where such practices may exist.

The rapid development of society and the expansion of human activities have resulted in interference with the natural environment. Assessing the environmental interference (EI) caused by human activities is highly important for socio-economic sustainable development. In this study, the spatial distance model (SDM) and resource endowment index (REI)-human activity index (HAI) ratio model were developed to calculate the environmental interference index (EII) in northern China (NC). The current spatial distribution and patterns of EII in NC were analyzed based on geographic information system (GIS) technology. In addition, the factors that influence the level of EI were examined through a geographical detector method. The results showed that the EII value in the eastern region was significantly higher than that in the western region and that differences in EI were spatial heterogeneity. The spatial distribution of EI was analyzed at the provincial, municipal and county scales, respectively. It was found that its distribution was closely related to urban development. The spatial distribution of EI displayed longitudinal zonality. East of 104.987°E, there were many large cities, such as Beijing, Tianjin, Qingdao and Zhengzhou, with high population densities and developed economies. Thus, these areas had high EI values. To the west of 104.987°E, such as in the Qinghai, Gansu, Xinjiang and Inner Mongolia regions, the EI values were generally low, with low environmental quality and fewer human activities. The level of EI in the Huang-Huai-Hai Plain region was higher than that in other areas, displaying obvious spatial dependence. Moreover, the distribution of EI exhibited high-high and low-low aggregation patterns, which accounted for 24.06% and 27.35% of the total study area, respectively. Specifically, in NC, the EI caused by human activities displayed obvious regional characteristics. In addition, the factors that influence EI were determined through a geographical detector model. The land use intensity was the direct factor related to changes in and the levels of EI, and the cover and growth of vegetation were the most important factors associated with mitigating human interference. The assessment results can provide a reference for the formulation of environmental governance and related policies.

Quantifying the influence of human activities on hydrological drought is of great significance to sustainable water resource management, but it remains difficult. The key to solving this problem is determining how to scientifically select the natural reference tributary. On the basis of existing research, this paper puts forward a tributary-comparison method that combines the Drought Propagation Intensity Index (DPI) with the human activity index to preliminarily and quantitatively determine the natural reference tributary from among all tributaries and then quantify the influence of human activities on hydrological drought in other tributaries. The empirical research was carried out in the upper reaches of the Shiyang River in the eastern area of Qilian Mountain. The results showed that, firstly, at the annual and seasonal scales, the tributaries in the upper reaches of the Shiyang River changed from hydrological humidification to hydrological aridification, from west to east, from 1961 to 2016. On the whole, the hydrological aridification of Huangyang River in the central part was the most serious, but its hydrological drought duration and drought Intensity showed a downward trend at a monthly scale. Secondly, using the tributary-comparison method, Xiying River was quantitatively selected as the natural reference tributary, and the influence of human activities on hydrological drought in other tributaries was quantified. On the whole, human activities will reduce hydrological drought duration and enhance hydrological drought intensity. The empirical study further proved that the tributary-comparison method has strong applicability in multi-tributary areas with obvious differences in human activities and provides a useful supplement to existing research methods. According to this method, tributaries that are weakly affected by human activity (or not affected at all) can be selected, and the tributaries least affected by human activity can also be identified. On this basis, the influence degree and direction of human activities in other tributaries on hydrological drought can be quantified.

As an important means to cope with global climate change, ecological restoration projects have a huge impact on ecosystem carbon storage functions. Scientifically evaluating the response process and mechanism of basin ecosystem carbon storage functions in ecological restoration projects is beneficial to the improvement of regional ecosystems. Taking Shiyang River Basin (SRB) as an example, and based on the perspective of “carbon sink–carbon source” mutual transformation, the current study utilized the InVEST (Integrated Valuation of Ecosystem Services and Tradeoffs) model to analyze the spatio-temporal dynamics of carbon storage in SRB, quantified the effect of ecological restoration projects on the ecosystem carbon fixation capacity, and identified sensitive and vulnerable areas of carbon loss against the background of climate and land use/cover change (LUCC). The results show that the ecosystem carbon storage in SRB changed significantly before and after the ecological project implementation, with a decrease of 5.71 Tg in 1986–2000 and an increase of 14.11 Tg in 2000–2016. The proportion of carbon sink enhancement areas was only 7.46% in 1986–2000, which increased to 15.04% in 2000–2016, indicating that the ecological restoration effect of the watershed was obvious as a result of the ecological management. The contribution of LUCC brought about by the ecological restoration project to the increase in ecosystem carbon storage was as high as 103.71%, for which the increase in woodland and grassland was the key. However, in 2000–2016, low carbon optimization areas accounted for 4.17% and carbon emission control areas for 6.16% of the total area of SRB. The carbon fixation capacity of these areas declined, and carbon emissions were elevated, especially in carbon emission control areas. These were mainly distributed in the oasis–desert transition zone in the mid-lower reaches, which are sensitive and vulnerable areas for carbon loss. Therefore, in future ecological restoration and protection processes, these areas should be given more attention and protection.

Identifying environmentally sensitivity regions and levels is an important aspect of resource management, especially in large arid ecosystems that exhibit sensitivity to climate change. This paper selected northwest China with complex and diverse environmental problems as the study area, and constructed the environmental sensitivity index (ESI) system including human intervention, disaster risk, land environment, biological and climate indicators, which were composed of thirteen factors. Then the environmental sensitivity was analyzed through using geographic information system (GIS) technology and spatial distance index (SDI) method. The temporal and spatial evolution characteristics of environmental sensitivity in Northwest China in the past 16 years were discussed. The results showed that: (1) the environmental sensitivity in the study area was in the medium level and its spatial heterogeneity was significant. The high and extremely sensitivity were mainly concentrated in the western and central areas, while the normal and low sensitivity were mainly distributed in the southeast of northwest China. (2) The ESI value decreased from 0.477 in 1987 to 0.429 in 2016, which reflected that the environmental conditions in northwest China have improved in the past 17 years, but not obviously. The regional sensitivity was still unstable, and the fluctuation change area was 232,136.28 km2, accounts for7.71% of the total area. This showed that local government had made some progress in environmental protection, but it still has a long way to go because of the deterioration of the regional environment in northwest China. (3) The SDI method can simply and directly inflect the environmental sensitivity distribution and change patterns, which provided management partitions with well-founded and more viable for planning and implementing effective environmental management.

Conducting evaluations of socio-economic activities in a large area is a difficult and complex process that is affected by many factors. EI represents the actual environmental interference caused by socio-economic development, and it is a quantitative expression in this paper. Understanding EI is of great significance for promoting the scientific management and sustainable development of social economies. This study selected 11 indexes that included the following eight aspects: terrain, climate, hydrology, soil, vegetation, land, population and economy. The SDM and RM were used to calculate the EII, and the EI of mainland China from 1980 to 2015 was comprehensively evaluated from a spatiotemporal perspective. The results indicated that the NOI, NEI and LII categories of EI accounted for more than 70% of the total area, while regions with HII, STI and HEI presented a gradually increasing trend over 35 years. The distribution of EI had obvious scale effects at different administrative units. In general, eastern China and central China had the highest EI, which presented high-high clusters. Western China had the lowest EI, and the low-low clusters were generally distributed in unoccupied areas. In addition, the areas did not change significantly. The change of EI in mainland China was the most drastic from 2000 to 2010 but stable after 2010, especially in 2015. The evaluation results provide a reference for the formulation of related policies for the coordination between the natural environment and socio-economic development.

On China's Loess Plateau, where the distribution of soil organic carbon (soil − Corg) is mainly influenced by topography, afforestation is an important strategy to sequester carbon and reduce soil erosion. To explore the effects of topography on soil − Corg, soil samples were obtained at six depths (0–0.1 m, 0.1–0.2 m, 0.2–0.4 m, 0.4–0.6 m, 0.6–0.8 m, and 0.8–1.0 m) from locations on the Loess Plateau which had supported apricot (Prunus armeniaca L.) growth for 16 years and differed in slope aspect (sunny or semi-sunny vs. shady or semi-shady) and gradient (14° ≤ S

97735 artificial reservoirs have been built in China since 1950s, which could guarantee the supply of urban water and agricultural irrigation. In arid oasis area, only the water of reservoir is available as water resource. The study of hydrochemical characteristics is the prerequisite for evaluating the water quality of domestic water and irrigation water. In the Hongyashan Reservoir, the middle of the Shiyang River Basin and the Tengger desert and Badain Jaran desert, water samples were taken at different points of the lake for about 3 years. The chemical characteristics of the lake water and their influencing factors were studied. The results of the samples for the test have shown that water of the Hongyashan Reservoir is weakly alkaline. And the main compositions of ions in the water are Ca2+ and $$\text{HCO}_{3}^{ - }$$ , hydrochemical type is Ca–HCO3. In terms of the seasonal variation of Hongyashan Reservoir, except for $$\text{NO}_{3}^{ - }$$ , the ions in the rest of the water showed roughly the same changeable characteristics in that the composition of ion is higher in summer and autumn, but lower in winter and spring. This is consistent with the seasonal variation in runoff ions throughout the Shiyang River Basin. Ionic characteristics are consistent with the ionic values of dry lakes in the world, which are suitable for urban water and water for irrigation, but are slightly higher than the global lake background standard. Carbonate weathering products are the main source of water ions in Hongyashan Reservoir, and evaporation also affects the ion characteristics of water.