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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. [ABSTRACT FROM AUTHOR]

Based on the total carbon emission data of 30 provinces and cities in China from 2000 to 2020, this paper used non-parametric kernel density estimation and traditional and spatial Markov probability transfer matrix methods to explore the temporal and spatial dynamic evolution characteristics of carbon dioxide emissions in China and then used a super-SBM model to calculate the carbon emission reduction potential of each province. The results showed that: (1) from 2000 to 2020, the total carbon emissions in China showed an upward trend of fluctuation, from 1.35 Gt to 4.90 Gt year by year, with an annual growth rate of 13.10%. (2) The core density curve showed a double peak form of "main peak + right peak," indicating that a polarization phenomenon occurred in the region. (3) The overall trend of carbon dioxide emissions shifting to superheavy carbon emissions was significant, and the probability of transition was as high as 74.69%, indicating that it was challenging to achieve leapfrog transition in the short term. (4) Based on the principle of fairness and efficiency of provincial carbon emission reduction, mainland China's 30 provincial administrative regions can be divided into four types. Finally, the carbon emission reduction path is designed for each province. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

• The rainy season was the key period when land use landscape pattern affected the river water chemistry. • The sub-watershed scale was the core scale that affects river water chemistry as a whole. • The "source-sink" functions of the same land use type changes with the change of scale. • Forestland and grassland have obvious interception effect on soil erosion at riparian scale. The impact of the land use landscape pattern on river hydrochemistry has significant scale effects. It is the premise and foundation of landscape optimization and the conservation of water resources to accurately identify the core scale of the landscape pattern impacting on river hydrochemistry. Taking Binggou River Basin in the source region of Shiyang River Basin as the study area, this paper selected the three spatial scales of catchment area, buffer zone, and riparian zone, and the relationships between land use types and landscape indices and river hydrochemical characteristics were analyzed at different spatio-temporal scales using redundancy analysis. The results showed that the hydrochemistry characteristics of Binggou River Basin had strong temporal variability, and the rainy season was the key period when the land use landscape pattern affected the river hydrochemistry. The sub-watershed and riparian scales were the core scales of influence of the landscape pattern on river hydrochemistry in Binggou River Basin. In particular, the landscape pattern index contributed the most to the river hydrochemistry at the sub-watershed scale on the whole, which was the core scale affecting river hydrochemistry. The "source" or "sink" functions of the same land use type also changed as the scale changed. Forest land showed weak "source" effect at the sub-watered scale, but a strong interception effect on the soil erosion process at the riparian scale, which is a typical "sink" landscape. [ABSTRACT FROM AUTHOR]