Thermokarst lakes, as prominent thermokarst landscapes in permafrost regions, significantly influence ecological vegetation, hydrological processes, and carbon cycling in the Arctic. However, the current understanding of the distribution characteristics and change mechanisms of Arctic thermokarst lakes remains limited. To address this gap, this study employs meta-analysis and mathematical statistical methods to investigate the distribution patterns and dynamics of thermokarst lakes. The results reveal a pronounced spatio-temporal heterogeneity in the distribution and changes of Arctic thermokarst lakes. These variations are closely associated with permafrost conditions, lithology, soil types, subterranean ice content, and soil temperatures. Most Arctic thermokarst lakes are located in continuous permafrost area, where subterranean ice content exceeds 10%, average soil temperatures are above -4°C, and there are specific vertical soil temperature gradients. The change trends of thermokarst lakes differ under various environmental conditions. Generally, the development of thermokarst lakes follows three stages: initial formation, mid-term expansion, and late-stage contraction, all influenced by hydrological and thermohydrological balances. As critical indicators of permafrost degradation and climatic environmental changes, thermokarst lakes profoundly impact carbon cycling, hydrological processes, and ecological environmental changes within the Arctic ecosystem.

Quantifying the contributions of climate change and human activities to changes in vegetation is important in terms of regional ecological protection and future research on the Loess Plateau. However, in the case of areas with naturally regenerated vegetation, where there are no clearly visible indications of human activities and ecological processes are not significantly disturbed, not all relevant forms of human activity can be remotely detected. Therefore, modelling the intensity of human modification of natural ecosystems could provide a pathway for a better understanding of the questions concerning where and how much vegetation change occurs in areas with evidence of human activities or land-use change. In this study, we utilized the Normalized Difference Vegetation Index (NDVI) between 2000 and 2022 and land-use datasets (a spatial resolution of 30 m) collected in 2000, 2010, and 2020 to distinguish areas with strong and weak anthropogenic interference on the Loess Plateau. In those areas with clearly visible human activity, we explored the relative contributions of climate change and human activity to vegetation dynamics. Taking the lagged duration variation between climate factors and vegetation growth into consideration, climatic factors influencing vegetation decadal dynamics were identified in the southern part of the Loess Plateau. The results are as follows: (1) With the implementation of the Three-North Shelter Forest Program, Grain-to-Green Program, and other ecological projects, the rate of vegetation restoration on the Loess Plateau slowed by 3.4%/10a during the period 2012-2022; however, the overall trend was an increase in vegetation. (2) In sensitive areas of vegetation restoration in the Loess Plateau, human activities with a relative contribution exceeding 65% were the dominant factors of vegetation variability in the areas with both intensive and weak human interference, which is approximately 2.0-fold higher than the contribution of climate change. (3) The interdecadal anomalies of precipitation in June were effective indicators of opposite west-east vegetation anomalies in the southern part of the Loess Plateau. Specifically, when precipitation increased by 10 mm in June, this southeastern part witnessed a decrease of 1.4% in NDVI in contrast with a 1.7% increase in the southwestern part. By coupling temporal and spatial information we have clarified the spatial distribution of trends and decadal variations in NDVI and its influencing factors. These observations from the Loess Plateau provide useful insights to help understand the relationship between vegetation change, climate change, and human activities on vegetation restoration globally or in other regions of China.

Soil erosion is influenced by various factors, such as land use and climate change. The Wangmaogou watershed, as a typical area for soil and water conservation in the hilly and gully regions of the Loess Plateau, has implemented a series of measures since the 20th century, including the Grain for Green Project. This study evaluated the spatial and temporal evolution characteristics of soil erosion intensity in the watershed in the years of 2010, 2015, and 2020 using the CSLE model. It also studied the situation of land use/cover change (LUCC) to analyze the spatial distribution patterns of land use and the responses of soil erosion in different time periods, thereby verifying the effectiveness of the soil and water conservation measures. The results revealed that from 2010 to 2020, the annual average soil erosion modulus in the study area decreased by 0.11 t hm^-2 a^-1, indicating a slight improvement in overall soil erosion conditions. However, the proportion of slight erosion decreased by 5.56%, while severe erosion increased by 4.02%, with the higher erosion zone mainly distributed in the northern, central, and northwestern parts of the watershed. Compared to the year 2010, soil erosion conditions in the watershed were greatly relieved in 2015 due to the decrease of rainfall and restoration of vegetation, but rebounded in 2020 resulting from the extreme rainfall events and declining vegetation cover quality. From 2010 to 2020, there were significant conversions between grassland and farmland in the northern and northeastern parts of the watershed. The decline in grassland quality resulted in a higher average soil erosion modulus compared to farmland, at 13.69 t hm^-2 a^-1 and 12.99 t hm^-2 a^-1, respectively. This study would contribute to figuring out the relationship between soil erosion in typical small watersheds of the Loess Plateau, extreme climatic events, and land use changes, providing scientific data support for future efforts to improve soil and water conservation benefits and mitigate soil erosion risks.

High-yield and superior-quality succulence is crucial to the development of national animal husbandry and food supply. However, the current understanding of the spatial and temporal variation pattern of succulence sown area needs to be improved, especially the stage characteristics, regional differences and driving factors are not yet clear. Based on the provincial panel data, we analyse the spatial and temporal dynamic patterns of succulence sown area from 2000 to 2020, and reveal its driving factors of forage supply and demand based on natural forage production, crop straw production, and forage demand estimated by MODIS- derived NPP datasets, crop production, and total livestock in each provincial-level region. The main results are that: (1) The sown area of succulence in China was 2199 thousand hectares, accounting for only 1.3% of the crop sown area in 2020. The succulence plantation in China is mainly distributed in pastoral areas, accounting for 59% of the country. (2) Since 2000, the interannual variation of succulence sown area in China has undergone three stages: a rapid growth stage (2000-2003, 464.2 thousand hm²/a), a rapid decline stage (2004-2009, -399 thousand hm²/a) and a slow growth stage (2010-2020, 64.3 thousand hm²/a). The pastoral provinces dominated the dynamics of the whole country. (3) Forage supply and demand factors can explain at most 92% of the dynamic of succulence sown area. Forage demand increases by 10000 tons, the sown area of succulence increases by 900 hectares at most. Straw forage and succulence complement each other, and straw forage production mainly has negative effects (the partial regression coefficients ranges from -1.2 to -0.5) on the sown area of succulence. The natural forage production has little effect on the change of succulence sown area. In addition, ecological engineering and agricultural policy play important roles in regulating the development of dairy, forage, and planting husbandry. Our study on spatial and temporal patterns of succulence sown area and its driving factors considering forage demand and supply can provide scientific support for the formulation of relevant policies and measures such as food security, ecological environment protection and crop structure adjustment.

Farmland abandonment is a common practical problem in rapid urbanization and rural transformation. Scientifically revealing the causes and differentiation mechanism of farmland abandonment at village scale in typical areas has direct and practical significance for village policies to control farmland abandonment, and has far-reaching strategic significance for ensuring food security and promoting rural revitalization. Based on the regional system theory of human-land relationship, this paper takes Nanchuan district of Chongqing, a typical county-level unit in the mountainous areas of Southwest China, as an example, uses multiple linear regression and natural breakpoint model, identifies the leading factors of farmland abandonment at village scale, summarizes the spatial distribution characteristics, explores the dynamic mechanism of different types of farmland abandonment, and puts forward concrete control countermeasures. The results show that: (1) Farmland abandonment is the imbalance of human-land relationship in rural regional system, and the new balance of such a relationship in rural regional system can be achieved by implementing scientific measures. (2) Typical county farmland abandonment can be divided into four types: facility abandonment > facility abandonment > disaster abandonment > circulation abandonment. (3) The total arable land abandoned showed a "river"-shaped corridor distribution with a clockwise rotation of 45°, and the middle-high values were observed in the high-altitude mountainous areas in the northwest and southeast parts of the county. The dominant factors were irrigation conditions, the proportion of cultivated land circulation, the distance to main roads, the proportion of emigrated population, the distance to rivers, the altitude, the amount of arable land per capita, the proportion of rural labor force, and the distance to the township. There are differences in the dominant factors and spatial distribution characteristics of farmland abandonment in different types. (4) Based on the causes, spatial characteristics, and actual situation of different types of cultivated land abandonment, four types are identified: facility shortage constraint type, disaster-prone damage type, farmer differentiation and relocation type, and policy guarantee imbalance type. Corresponding control strategies and 12 control models for cultivated land abandonment, including facility construction and upgrading, are proposed.

The mass elevation effect (MEE) is a thermal phenomenon associated with uplifted landmasses, leading to spatial differentiation in water-heat assemblies that profoundly affect the geo-ecological pattern and environmental evolution of mountains and regions. This study developed a ground-air temperature regression model to simulate the temperature distribution on the Qinghai-Tibet Plateau using MOD11C3 data and meteorological observations, analyzing the spatiotemporal diversity and dynamic evolution of the MEE across the entire plateau and internal landform regions were estimated and analyzed from 2000 to 2019. Employing the Geodetector method, the research uncovered the genesis patterns of the MEE at different scales, revealing an average MEE of 4.13 ℃ with a pronounced centripetal pattern from northeast to southwest and decreasing elevation-dependent characteristics that were significantly negatively correlated with longitude and latitude. The average MEE of the landform regionalization was 5.06 ℃, indicating a stronger internal spatial differentiation within landform regionalization. Seasonally, the MEE was slightly stronger in the dry season, with distinct patterns of weakness in the northwest and strength in the southeast during the dry season, and the opposite in the wet season. The MEE showed an asymmetric linear enhancement pattern under global climate change, with an inclination rate of 0.26 ℃/10 a, presenting a "ring-like" characteristic of strong in the east and weak in the west and decreased from the hinterland core to the edge. The weak areas were significantly enhanced, whereas the strong areas showed small variations. The MEE fluctuation magnitude and change rate were both stronger in the dry season than in the wet season, with the dry season primarily contributing to MEE changes. The spatial and temporal patterns of the MEE were influenced by scale effects, with latitudinal zonation at the macroscale and microtopographic features at the regional level. Moreover, NDVI and barometric pressure were found to enhance the seasonal spatial variations of the MEE. This comprehensive analysis provides deep insights into the mountain science and responses to climate change.

This research aims to decipher the patterns and mechanisms of surface water recharge during the rainy season in plateau mountain-lake region. Based on the stable hydrogen and oxygen isotope data of multiple water bodies collected in the Erhai Lake Basin from July to August 2022, and using Bayesian mixing models and remote sensing technology, the study quantifies the sources and proportions of surface water recharge and explores water body transformation mechanisms. The results indicate that: (1) Precipitation in the Erhai Lake Basin during the rainy season is influenced by evaporation and monsoon climate, resulting in hydrogen and oxygen isotope values that are more negative compared to groundwater and surface water. Groundwater δD and δ¹⁸O indicate that in areas of high altitude and high water richness, the hydrogen and oxygen isotope values of groundwater are more negative, while d-excess values reveal evaporation differences among different aquifer groups. The hydrogen and oxygen isotope values of surface water gradually become more positive as the water flows from inflowing rivers through Erhai Lake to outflowing rivers, with the isotope values on the eastern slope and southern region of Cangshan Mountain being more positive compared to the northern region. For the eastern slope of Cangshan Mountain, the midstream area shows the most significant evaporation. (2) The spatial pattern of surface water recharge sources between Cangshan Mountain and Erhai Lake shows that surface water contributes the most to its downstream mixed water bodies. The contribution rate of precipitation and surface water in each river section between Cangshan Mountain and Erhai Lake is shown as follows: the contribution rate of precipitation and surface water in the river section above the mountain outlets is smaller than that in the river section below the mountain outlets; while the contribution rate of groundwater is vice versa. (3) Along the river flow direction, the spatial pattern of surface water recharge sources is jointly influenced by topography, geological conditions, surface cover, and water vapor characteristics. Areas with good vegetation cover, high surface temperatures, and high actual evapotranspiration receive more precipitation recharge; areas with relatively poor vegetation cover receive more surface water recharge and the contribution rate of groundwater to surface water depends on the type of aquifer groups.