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The natural environment of the Gansu-Qinghai region in northwest China exhibits spatial variation, resulting in distinct adaptive strategies among populations in different geographical areas. In this study, we analyzed the diachronic trend and regional variations in caries prevalence among 10 different middle and late-Holocene groups by examining dental caries data to explore the correlation between different adaptation strategies and caries frequency. Frequency data was used to compare dental caries between populations, and the Chi-square test was employed to detect statistical differences. A multidisciplinary approach was employed to investigate the relationship between these changes and the adaptive strategies adopted by the populations in this region. The result shows that there was a gradual increase in caries prevalence over time in eastern Gansu, which corresponded with development of millet farming and social hierarchy. In the Hexi Corridor, caries prevalence exhibited fluctuations attributable to climate variability, human migration, and regime change. The research proposes that changes in adaptive strategies due to various social and environmental factors are reflected in human teeth, while also presenting a novel endeavor of aggregating a large, multisite bioarchaeological dataset in order to investigate the interactions between Holocene populations and palaeoenvironments in northwest China.

The soil moisture (SM) balance is affected by afforestation. In this study, the CiteSpace software was used to review the literature on the impact of afforestation on SM, and we further present research findings on the Loess Plateau (LP) as follows: (1) the spatio-temporal heterogeneity of SM varies depending on the research scale; (2) the presence of a dried soil layer significantly hinders deep SM recharge; (3) the accumulation of net primary productivity (NPP) may be occurring at the expense of SM. The following research topics are discussed: (1) the recharge and consumption of deep SM in LP; (2) the green water footprint and its shortage of non-crop greenery for evaluating SM allocation and use; (3) the development of inclusive models encompassing different spatial scales to assess the limits of soil water carrying capacity for vegetation (SWCCV). [ABSTRACT FROM AUTHOR]

The cycle of carbon and water in ecosystems is likely to be significantly impacted by future climate change, especially in semiarid regions. While a considerable number of investigations have scrutinized the repercussions of impending climatic transformations on either the carbon or water cycles, there is a scarcity of studies delving into the effects of future climate change on the coupled water–carbon process and its interrelationships. Based on this, the Sanchuan River Basin, an ecologically fragile region of the Loess Plateau, was chosen as the research area. General circulation model-projected climate scenarios (SSP1-2.6, SSP2-4.5, SSP5-8.5) and an ecohydrological model were integrated to predict (2021–2100) changes in actual evapotranspiration (ET), surface runoff (Rs), net primary productivity (NPP), and soil organic carbon (SOC). The results indicated that under the impacts of future climatic warming and humidification, ET, Rs, and NPP will increase by 0.17–6.88%, 1.08–42.04%, and 2.18–10.14%, respectively, while SOC will decrease by 3.38–10.39% in the basin. A path analysis showed that precipitation and temperature had significant effects on ET and NPP, Rs was more sensitive to precipitation, and temperature had a significant impact on SOC. Furthermore, all climate scenarios had an average ET-NPP correlation coefficient greater than 0.6, showing that the basin's water–carbon cycle was tightly coupled. However, under SSP5-8.5, the correlation coefficient of Rs-NPP decreased from −0.35 in the near-future period to −0.44 in the far-future period, which may indicate that the positive effect of increased precipitation on Rs-NPP would barely offset the negative effect of large future temperature increases. As a foundation for achieving sustainable water resource management and ecosystem preservation policies, this study can be utilized to build adaptation methods to manage climate change. [ABSTRACT FROM AUTHOR]

[Objective] This study aims to comprehend the spatial distribution patterns of arable soil nutrients in various geomorphic conditions of the Loess Plateau, to unveil the driving factors behind these changes, and to provide the critical insights for precision management in the regional agriculture and the construction of agricultural projects. [Methods] Based on the 2020 soil nutrient data from the Loess Plateau in Shaanxi, the Kriging interpolation method was employed to analyze the spatial patterns of soil nutrients across four different geomorphic types. The driving factors behind these nutrient spatial variations was explored by using the geodetector model. [Results] (1) In the Loess Plateau, spanning from the Great Wall's sandy lands, through the hilly and gully regions of northern Shaanxi, the loess table lands in northern of Weihe River, to the Guanzhong Plain, the average contents of soil organic matter (SOM), total nitrogen (TN), available phosphorus (AP), and available potassium (AK) exhibited a gradual increasing trend. Specifically, the SOM content averaged 10.20, 10.08, 15.28, and 18.78 g/kg, respectively, across these regions. TN averaged 0.63, 0.66, 0.98, and 1.19 g/kg. AP level averaged 12.99, 13.10, 16.97, and 27.24 mg/kg, and AK averaged 117.72, 149.94, 217.27, and 252.83 mg/kg, respectively. This trend indicated a consistent increase from the sandy lands to the plains. (2) In the loess area of Shaanxi, the duration of sunshine had most significant factor influencing overall nutrient contents, followed by annual temperature and fertilizer use. The distribution of nutrients in the windy area was predominantly affected by soil bulk density, whereas in the hilly and gully areas, plateau areas, and plains, fertilizer use was the primary influencing factor. The interaction of various factors provided a more comprehensive explanatory of nutrient dynamics than individual factor alone. [Conclusion] To optimize soil health, it is advisable to increase nutrient input and enhance soil fertility retention in sandy areas and hilly and gully areas. In contrast, the focus should be on improving nutrient utilization efficiency for plateau and plain areas. Additionally, in the process of farmland, it is crucial to tailor human activities to suit the environmental characteristics and specific conditions of different geomorphic regions. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to explore the erosion characteristics of buckwheat fields on the Loess Plateau under heavy rain conditions, to try to analyze the potential influencing factors, and to provide a reference for the management of slope farmland on the Loess Plateau. [Methods] The rainstorm event of 10 th July 2022 in Dingbian, Shaanxi Province were taken as an example. The features of gully erosion on buckwheat land were analyzed based on a combination of remote sensing and field measurements, and the influences on gully erosion on buckwheat land were investigated. [Results] (1) The gully heads within buckwheat farmland affected by severe rainfall tended to form where they intersected with other land types. (2) The average width and depth of rill erosion varied between 5.2 to 29.5 cm and 2 to 19.6 cm, respectively. The ratio of width to depth and the gully density ranged from 0.88 to 3.782 and 0.028 to 1.56 m/m², respectively. The erosion intensity of rill erosion was at a maximum of 20 294.66 t/km². (3) The ephemeral gully had an average width and depth ranging from 37.3 to 173 cm and 8 to 30.7 cm, respectively. The ratio of width to depth and gully densities were 2.161~18.750, and 0.003~0.142 m/m², respectively. Additionally, the maximum intensity of ephemeral gully erosion was 31 629.83 t/km². (4) The gully erosion in buckwheat fields was affected by the slope, length of slope, upstream catchment area, and the measures taken by neighbouring plots. [Conclusion] Compared with other land types such as grasslands and mulched cornfields, gully erosion of the buckwheat slope cropland under heavy rainfall conditions is more severe, and reaches to the intensity of intense erosion. [ABSTRACT FROM AUTHOR]

Understanding plant‐water relations is essential for effective regional water management and promoting ecologically sustainable development on the Loess Plateau, especially in the context of the Grain for Green project initiated in 1999. This study evaluated the variations in vegetation variables (leaf area index, enhanced vegetation index, solar‐induced chlorophyll fluorescence and gross primary production) and hydroclimatic variables (precipitation, total water storage, aridity index and standardized precipitation evapotranspiration index) from 2003 to 2020, along with their interactions across the Loess Plateau. Our analysis revealed a general increase in vegetation variables, with the largest increase observed in the forest expansion areas. Precipitation and the aridity index exhibited significant upwards trends, while total water storage showed a significant decline, particularly in the forest expansion areas. Vegetation variables were more sensitive to changes in total water storage across the Loess Plateau. In the northwest region, where large‐scale croplands and grasslands expansion occurred, vegetation variables also showed sensitivity to precipitation. Lag effect analysis revealed short time lags (1–3 months) between vegetation and hydroclimatic variables, expect for total water storage (6 months). Overall, human activities and climate factors contributed 58.4% and 41.6% to the increase in leaf area index, and 52.2% and 47.8% to the increase in gross primary production, respectively. In relatively arid environments, precipitation contributed over 50% to the observed vegetation greening. This study underscores the increasingly significant role of human activities in driving vegetation greening on the Loess Plateau, particularly in large‐scale afforestation areas. [ABSTRACT FROM AUTHOR]

The Baota District of Yan'an City, located in the Loess Plateau, is an important patriotic education base in China. The region's fragile geological environment and frequent geological disasters pose significant threats to the production and livelihood of residents. Establishing a landslide traces inventory can provide crucial assistance for studying regional land disaster distribution patterns and implementing disaster prevention and mitigation measures. However, the Baota District has not yet established a comprehensive and detailed landslide traces inventory, resulting in a lack of clear understanding and comprehensive knowledge regarding the threats and impacts of landslide disasters in the area. Therefore, this study employed high-resolution satellite images, applying a human–computer interactive visual interpretation method in conjunction with field survey verifications, to develop the most detailed and comprehensive landslide traces inventory for the Baota District to date. The results indicate that within the 3556 km2 area of the Baota District, there are 73,324 landslide traces, with an average landslide density of 20.62 km-2 and a total landslide area of 769.12 km2, accounting for 21.63% of the total land area. These landslides are relatively evenly distributed throughout the district, with a higher concentration in the east compared to the west. Most of the landslides are small in size. This study can support disaster prevention and mitigation efforts in the Baota District and serve as a reference for establishing landslide inventories in other regions of the Loess Plateau. [ABSTRACT FROM AUTHOR]

The extensive implementation of the 'Grain for Green' project over the Loess Plateau has improved environmental quality. However, it has resulted in a greater consumption of soil water, and its overall hydrological effects remain highly controversial. Our study utilized a coupled land-atmosphere model to evaluate the effects of vegetation changes resulting from revegetation or reclamation on the hydrology of the Loess Plateau. Revegetation was found to stimulate an increase in precipitation, evapotranspiration, and atmospheric water content. However, the increase in precipitation was insufficient to compensate for soil water loss driven by intensified evapotranspiration, resulting in a decrease in both runoff and soil water content. In contrast to revegetation, reclamation would reduce precipitation, although the reduction was less than the decrease in evapotranspiration. This could lead to an increase in both runoff and soil water content. The results provide an important scientific basis for the hydrological effects of vegetation changes on the Loess Plateau, which is particularly important for guiding current and future revegetation activities toward sustainable ecosystem development and water resources management. [ABSTRACT FROM AUTHOR]

Regional socioeconomic development is intricately tied to reasonable land-use resources. Although many studies have analyzed land-use carbon emissions, there is a lack of analysis of the concept of intensity. Studying the land-use carbon emission intensity (LUCEI) is crucial for shaping effective land management strategies that support the integrated sustainable development of society, the economy, and the environment. This study examines land-use changes on the Loess Plateau (LP) from 2000 to 2020. The coefficient method, spatial autocorrelation analysis, and optimal parameters-based geographical detector model are used to identify and analyze the spatial clustering patterns and influencing factors affecting LUCEI, which provides more in-depth insights for the study of LUCEI. The results indicate: (1) Urban and Grassland areas showed the most significant growth, with Urban areas expanding by 10,845.21 km2 and Grasslands by 7848.91 km2, respectively. This Urban expansion was mainly caused by the conversion of Grassland and Cropland, while Grassland expansion was primarily attributed to the decline in Barren. (2) The average LUCEI on the LP climbed from 0.38 in 2000 to 0.73 in 2020, indicating a 190.70% growth rate. (3) The spatial pattern of LUCEI remained stable but unevenly distributed, with extensive High-High and Low-Low clusters. (4) Socioeconomic factors had a greater explanatory power for LUCEI in the LP than natural factors. The LUCEI is not driven by a single factor, but by the combined influence of multiple factors. The interaction between nighttime light and population density explained the spatial distribution of LUCEI most strongly, with a q-value of 0.928. The findings underscore the critical role of socioeconomic development in shaping carbon emission dynamics on the LP. By linking LUCEI growth to land-use changes, this study offers concrete scientific guidance for policymakers seeking to balance socioeconomic growth with sustainable land-use practices. Based on these results, we recommend developing appropriate urban development plans that optimize land-use structures, enhance regional carbon sequestration capacities, and fully implement green transition requirements. [ABSTRACT FROM AUTHOR]

Soil loss is a common land degradation process worldwide, which is impacted by land use and climate change. In this study, random forests (RF) were first used to establish a soil loss model at the scale of a small watershed in the hilly‐gully region of the Loess Plateau based on the field observation data. Subsequently, the model was used to predict soil loss in the Chabagou watershed under the historical (1990–2020) and future emission scenarios, namely SSP1–2.6 (low‐emission), SSP2–4.5 (medium‐emission) and SSP5–8.5 (high‐emission) (2030–2,100) from the Coupled Model Intercomparison Project Phases 6 (CMIP6). In the RF model, the coefficient of determination (R2) and Nash‐Sutcliffe coefficient of efficiency (NS) were both greater than 0.86, and the RMSE‐observations standard deviation ratio (RSR) was less than 0.36. Additionally, the RF‐based model had higher simulation accuracy and robustness than those of the previous soil loss models, indicating its potential for wider applications in simulating soil loss. Compared with soil loss between 1990 and 1999, climate change led to a 35.36% increase in soil loss, while land use change resulted in an 11.13% reduction from 2000 to 2020 in the Chabagou watershed. This reveals that the current land use management could not effectively counterbalance the soil loss caused by rainstorms. Furthermore, compared with the historical period (1990–2020), under SSP1–2.6, SSP2–4.5 and SSP5–8.5 (2030–2,100), the soil loss rates without land use change would be increased by 6.01%, 19.11% and 35.35%, while the soil loss rates with land use change would be changed by −5.88%, +4.41% and +19.12%, respectively. These results help to provide a scientific basis for enhancing the capacity to respond to climate change and mitigation of soil and water loss on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Terracing is an important measure to conserve water and soil on the Loess Plateau. Previous studies have showed that due to extreme rainstorms and a lack of maintenance, loess terraces have experienced degradation predominantly as collapses and sinkholes. Investigating the hydrological processes associated with terrace degradation is vital to understand terrace degradation mechanisms and maintain terraced landscape sustainability. Using a high‐resolution digital elevation model (DEM) based on unmanned aerial vehicle (UAV)remote sensing, as well as SIMulated Water Erosion (SIMWE) model, we explored the runoff–sediment dynamics on the terraced slopes on the Loess Plateau under rainstorm conditions and the terrace degradation patterns. The results showed that the dominant longitudinal water flow between terrace steps and converging lateral water flow along terrace surfaces indicate terrace ridge collapses and terrace surface sinkholes, respectively. Damaged areas exhibit high sediment flux and erosion potential. The water dynamics and degradation pattern were influenced by the original slope topography and terrace morphology. Specifically, most damages are distributed on concave slopes with concentrated water flow. In narrow terraces, under scattered longitudinal water flow, the dominant damages are ordinary collapses and the overall terraced topography tends to degrade into natural slopes. In wide terraces, concentrated longitudinal and well‐developed transverse water flows form a basic degradation pattern dominated by sinkhole‐induced collapses. This study verified the feasibility of SIMWE‐based hydrological simulation in assessing the degradation pattern of terraces on the Loess Plateau and demonstrated its potential for spatial scales and complex scenarios through compared with the soil moisture content (SMC)‐based method. The study concluded that the dominant runoff paths under the constraints of slope microtopography control the terrace degradation patterns. Our findings can serve as a theoretical basis for predicting hydrological hazards on terraces on the Loess Plateau and conducting a scientific design of terraces. [ABSTRACT FROM AUTHOR]

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Acta Prataculturae Sinica is the property of Acta Prataculturae Sinica Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Medicago ruthenica is a promising leguminous forage crop due to its lack of saponins, which prevents bloat in livestock from excessive consumption. Legume/grass mixed cropping is an effective forage planting method widely used in agricultural and pastoral regions. However, there is a lack of research on using legume-grass mixed cropping to establish perennial, high-yield, and high-quality cultivated grasslands in the Longxi Loess Plateau. This study conducted a legume/grass intercropping experiment in the Longxi Loess Plateau region of northwestern China, using Medicago ruthenica and Bromus inermis. Experimental plots were established in 2021, with field sampling and laboratory analysis starting in 2022 and 2023, respectively. The research aimed to investigate the effects of intercropping Medicago ruthenica with Bromus inermis on forage yield and quality, and to determine the optimal intercropping ratios. The experiment tested various intercropping ratios of Medicago ruthenica and Bromus inermis in the fall (2:8, 3:7, 4:6, 5:5, 6:4, 7:3, 8:2), with sole crops of each species serving as controls. Results showed that, in the second and third years of mixed cropping, the forage yield under mixed cropping treatments was significantly higher than that of Medicago ruthenica and Bromus inermis monoculture, with increases of 40.89-70.88% and 13.97-38.22% in the second year, and 131.91-199.13% and 44.06-85.82% in the third year. When the legume proportion in the mixed cropping system was around 30%, competition between the two forages reached equilibrium, demonstrating the benefits of mixed cropping. The crude protein and ether extract content of mixed forage were significantly higher than those of monoculture, while the neutral detergent fiber and acid detergent fiber contents were significantly lower, indicating a higher feeding value for the mixed forage. The legume proportion was a key factor influencing the yield of mixed forage. In conclusion, a mixed planting ratio of Medicago ruthenica and Bromus inermis at 3:7 resulted in higher yield and nutritional quality, making it an optimal ratio for establishing cultivated forage fields in the Longxi Loess Plateau. [ABSTRACT FROM AUTHOR]

The Loess Plateau region features fragmented landforms, sparse vegetation, and short but intense summer rainstorms that can easily cause severe soil erosion. To evaluate its applicability to a typical Loess Plateau in northern China, an indoor laboratory experimental study was conducted for events with different slope lengths (3, 4, and 5 m) and rainfall intensities (50, 60, 70, 80, 90, 100, 110, and 120 mm/h). EUROSEM (European Soil Erosion Model) was used to simulate the soil erosion process and predict both total runoff and sediment yield. The EUROSEM modeling results were compared with the observed experimental values and analysed to determine the performance of EUROSEM. The results and analysis showed that EUROSEM could effectively simulate the runoff processes. It produced better predictions for the total runoff yield than for the sediment yield, with Nash–Sutcliffe efficiencies of 0.9003 and 0.1820, respectively. The qualified rates of the RE (relative error) between simulated and observed values of the total runoff and sediment yield were 87.5% and 37.5%, respectively. Compared to the sediment yield under rainfall intensities of 50–80 mm/h, those under 90–110 mm/h had lower RE and higher NSE, which increased from −3.9 to 0.5. However, the modeling results deviated more from the experimental data at a rainfall intensity of 120 mm/h. According to this study, EUROSEM is a good fit for simulating the runoff and partial sediment yield processes of the Loess Plateau region's slopes. However, the accurate prediction of sediment yield still requires more research to achieve complete effectiveness using EUROSEM for typical and wide scenarios in China. [ABSTRACT FROM AUTHOR]

Understanding the mechanisms and patterns of runoff generation in watersheds is fundamental to building hydrological and soil erosion models. It also provides important guidance for watershed water resources management and rational utilization. In order to reveal the in- fluence of vegetation restoration on the runoff production mechanism and model of the Loess Plateau, the Dongzhuanggou watershed, which is dominated by natural grassland restoration, and the Yangjiagou watershed, which is dominated by afforestation restorationin in the gullied loess plateaus were taken as research areas. The flood process lines and regression curves of two contrasting small catchments under different rainfall types were analyzed, and the change of runoff production pattern in the gullied region of loess plateau under vegetation restoration was studied. The results indicate that with the restoration of the watershed's vegetation and its eco-hydrological functions in these small water- sheds, annual runoff generation capacity decreases, while water retention capacity increases. Vegetation restoration effectively reduces peak flow and prolongs flood duration, especially the recession period of the flood, thereby achieving the effect of flood mitigation. Under the influence of vegetation restoration, the runoff generation pattern tends to shift from the traditional infiltration-excess runoff pattern to a shallow sub- surface saturation runoff pattern. This change demonstrates that vegetation restoration can effectively mitigate floods and thus play a significant role in flood control and disaster reduction. Additionally, it can efficiently transform generalized precipitation resources into soil water and interflow, regulate the seasonal distribution of streamflow, increase ecological water use, and promote the healthy and stable development of vegetation ecosystems in semi-arid areas. [ABSTRACT FROM AUTHOR]

Variable infiltration capacity model is used to quantitatively analyse the runoff reduction benefits of three basins on the Loess Plateau since the implementation of the 'Grain for Green' programme. The programme played an important role, contributing to >60% of the runoff variation in the different basins. Furthermore, for every 1000 km2 increase in cumulative forest area in basins, the rate of runoff coefficient reduction changed by −30%, −37.3% and 169% in the late stage of the programme compared to the early stage, respectively ('-' represents a decrease in reduction rate). This was closely related to the restoration of vegetation. [ABSTRACT FROM AUTHOR]

Copyright of Chinese Journal of Applied Ecology / Yingyong Shengtai Xuebao is the property of Chinese Journal of Applied Ecology and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Soil aggregation, an important indicator of soil restoration in degraded ecosystems, is a fundamental unit of soil structure. However, research on the influence of grass–shrub composites on the distribution of >0.25 mm soil water-stable aggregates (macroaggregates) is scarce. Therefore, this study focuses on the hill and gully region of the Loess Plateau, where vegetation has been well restored since the return of farmland to forests and grasslands. The study investigated the root and macroaggregate distribution characteristics and interrelationships of three widely distributed mixed vegetation types of Caragana korshinskii and Agropyron cristatum (C-AC), C. korshinskii and Bothriochloa ischaemum (C-BI), and C. korshinskii and Artemisia gmelinii (C-AG) in this area. The results indicate that soil macroaggregates decrease with increasing depth. Due to the spatial differences in the distribution of shrub root, the content of macroaggregates at 50 cm from the shrub base was higher than that at the shrub base, with an increase of 25.98%–34.27% in different vegetation associations. In this study, the root length density and root diameter better reflected the influence of roots on the distribution of macroaggregates, and the product of the two had a good power function relationship with the content of macroaggregates (R2 ≥ 0.82, p < 0.01). Grey correlation analysis showed that the influence of root length density on the distribution of large aggregates was greater than that of root diameter. The content of macroaggregates in the vegetation association of taproot herbaceous plants and shrubs was higher than that of fibrous root herbaceous plants. The average soil macroaggregate content in the C-AG was 15.79%–248.6% higher than that in the C-BI and C-AC. In this study, the spatial distribution differences in root caused by shrub growth were the main reason for the spatial heterogeneity of soil macroaggregate content distribution. The improvement ability of soil macroaggregates was higher in the combination of taproot herbaceous plants and shrubs than in the combination of fibrous root herbaceous plants and shrubs. The results of this study can, to some extent, reveal the influence and mechanisms of plant roots on soil aggregates in grass–shrub vegetation association. [ABSTRACT FROM AUTHOR]

Vegetation restoration is an effective measure to cope with global climate change and promote soil carbon sequestration. However, during vegetation restoration, the turnover and properties of carbon within various aggregates change. The effects of plant source carbon input on surface soil and subsurface soil may be different. Thus, the characteristics of carbon components in aggregates are affected. Therefore, the research object of this study is the Robinia pseudoacacia forest located in 16–47a of the Loess Plateau, and compared with farmland. The change characteristics of organic carbon functional groups in 0–20 cm, 20–40 cm, and 40–60 cm soil layers were analyzed by Fourier near infrared spectroscopy, and the relationship between the chemical structure of organic carbon and the content of organic carbon components in soil aggregates was clarified, and the mechanism affecting the distribution of organic carbon components in soil aggregates was revealed in the process of vegetation restoration. The results show the following: (1) The stability of surface aggregates is sensitive, while that of deep aggregates is weak. Vegetation restoration increased the surface soil organic carbon content by 1.97~3.78 g·kg−1. (2) After vegetation restoration, the relative contents of polysaccharide functional groups in >0.25 mm aggregates were significantly reduced, while the relative contents of aromatic and aliphatic functional groups of organic carbon were significantly increased. The opposite is true for aggregates smaller than 0.25 mm. (3) With the increase in soil depth, the effect of litter on organic carbon gradually decreased, while the effect of root input on the accumulation of inert carbon in deep soil was more lasting. [ABSTRACT FROM AUTHOR]

On February 17 2023, a landslide occurred on a highway slope along the Xiaolangdi Reservoir of the Yellow River, involving approximately 1,200 m3. This event directly resulted in road interruption and had profound social repercussions. This paper researches the landslide using a combination of field investigation, remote sensing imagery, laboratory tests, and numerical simulation. It traces the evolution of landslide occurrences influenced by human engineering activities and investigates the mechanisms by considering climatic factors, water levels fluctuations, and stress changes. The results indicate that: (1) fluctuations in water levels can reduce the stability coefficient of ancient landslides, albeit without directly triggering them. Moreover, alterations in soil stress induced by artificial excavation changes the distribution of the slope plastic zone, consequently altering potential sliding zones. (2) rainfall and temperature emerge as primary factors influencing the occurrence of accumulation landslides, it is particularly susceptible with the transition between winter and spring. (3) freeze-thaw action exerts significant pressure on sandstone bedding, which causes notable expansion deformation. Consequently, it is advisable to consider soil temperature and bedrock deformation when monitoring similar slopes. [ABSTRACT FROM AUTHOR]

Check dams are widely used throughout the world to tackle soil and water loss. However, the frequency of extreme rainfall events has increased owing to global climate change and the main structure of check dam is gradually aging, which lead to an increase in the failure risk of check dams. Thus, it is necessary to carry out the study on failure risk diagnosis and assessment of check dams. In the study, machine learning algorithms (ML), including random forests (RF), support vector machine (SVM), and logistic regression (LR), were used to integrate the environmental and engineering factors and then assess the risk of check dam failure due to the “7.26” rainstorm on July 26, 2017, in the Chabagou watershed, located in the hilly-gully region of the Loess Plateau, China. To verify the generalizability of the model in this study, these models were used for the Wangmaogou catchment north of the Loess Plateau. The accuracy assessment by the receiver operating characteristic (ROC) curve indicated that the RF model with an area under the ROC curve (AUC) greater than 0.89 was the most precise model and had a higher generalization ability. In addition, the model dataset was relatively small and easy to obtain, which make the risk modeling of check dam failure in the study has the potential for application in other regions. In the RF model, each factor selected was confirmed to be important, and the importance values for engineering factors were generally higher than those for the environmental factors. The risk map of check dam failure in the RF model indicated that 56.34% of check dams in the study area had very high and high risks of dam failure under high-intensity rainfall in 2017. Based on the importance of factors and the risk map of check dam failure, the prevention and control measures for reducing the risk of check dam failure and promoting the construction of check dam are proposed. These proposals provide a scientific basis for the reinforcement of check dams and the future layout of check dams in the Chinese Loess Plateau.

Abstract In the Loess Plateau, the impact of abandoned farmland on soil properties and enzyme activity, along with its temporal variations and potential driving factors, remains a mystery. This study was designed to systematically and comprehensively examine the variations in soil enzyme activities, particle size distribution, and stability of soil aggregates at different stages of ecological recovery in the Loess Plateau. Our findings reveal a nuanced temporal pattern: with the progression of cropland abandonment, there is a notable decrease in soil bulk density. Concurrently, a dynamic trend in enzyme activities is observed—initially exhibiting a decline, followed by an increase over extended periods of recovery. Notably, prolonged abandonment leads to marked enhancements in soil structure. Parameters such as the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates show an overall increasing trend. In terms of the Relative Dissipation Index (RSI), our data indicate a sequence of control > 2 years of abandonment > 4 years > 6 years > 14 years. From this, it can be seen that fallowing may be an effective natural restoration strategy for improving the physical structure of soils in the Loess Plateau and restoring soil nutrients. However, positive changes may take a long time to become evident.

Abstract In the area of “returning farmland to forest” on the Loess Plateau in China, it is difficult to cultivate artificially planted trees into forests. In the current study, abandoned cultivated land after 10 years of natural restoration served as controls (CK), while the treatments included afforestation periods of 2, 4, 6, 8, and 10 years. Soil samples were collected from various depths: 0–20, 20–40, 40–60, 60–80, to 80–100 cm. The findings revealed that with increasing years of artificial afforestation, soil pH gradually increased, and soil moisture content rose in the 0–20 cm layer while declining in deeper layers (20–100 cm) in the Maxian Mountain region of the Loess Plateau. Moreover, the total carbon, nitrogen, phosphorus, and potassium content initially increased and then decreased with the duration of artificial afforestation, reaching peak values after 8 years. Contents of organic matter, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium in the same soil layer increased with each year of afforestation. However, upon reaching 10 years of artificial afforestation, the effective nutrient content in the 60–80 and 80–100 cm soil layers exhibited a decrease. The values of Integrated Fertility Index (IFI) in different afforestation years were ranked as follows: 8 years > 6 years > 10 years > 4 years > 2 year, but all of them were significantly smaller than those of natural restoration plot CK (P

Clouds play an important role in the Earth-atmosphere system.To deeply analyze the cloud characteristics in the Loess Plateau region （LP）， the macro and micro physical characteristics of clouds were analyzed by using the CloudSat-CALIPSO data from 2007 to 2016 in four regions of the Loess Plateau， namely， semi-humid， semi-arid， arid， and cold arid.The findings indicate that： （1） In the LP， the annual average frequency of clouds exceeds 55%， with the highest frequency in spring and summer， and relatively lower in autumn and winter.The frequency of clouds in semi-humid region is higher than that in other regions.However， the months with the highest frequency of cloud occurrence in the other three regions are earlier than those in the semi-humid region.（2） The frequency of single-layer clouds is the highest in all regions， accounting for over 60% of the total cloud amount， with double-layer clouds being the main type among multi-layer clouds， accounting for about 25% of the total cloud amount.The seasonal variation of cloud height in each region shows that it is greater in spring and summer than in autumn and winter， and that it is greater in semi-humid region than in other regions in all seasons.The seasonal variation of cloud geometric thickness is not significant in all regions， which is between 1 km and 4 km， with mainly thin clouds， and 78.13% of the cloud geometric thickness is less than 2 km.（3） The annual average value of cloud liquid water content in all regions reaches more than 220.5 mg·m-3， about 6.5 times of the annual average ice water content.It is mainly distributed in the altitude below 8.5 km， and the liquid water content gradually increases as the altitude decreases， in which the cloud liquid water content in the semi-humid region is larger than that in other regions.The ice water content in each region is small throughout the year， mainly distributed in the altitude layer below 16.5 km.（4） The values of the effective radius of liquid droplets in each region are mainly concentrated in the range of 12~16 μm， with a maximum of about 24 μm in the spring in the semi-arid region； the maximum value of the effective radius of ice particles occurs in the summer in the semi-humid region.The values of droplet number concentration in all regions were concentrated at 60~80 cm3， which were smaller than the mean value of ice particle number concentration， with peaks occurring in the summer in all regions， and the peak of ice particle number concentration occurring in the spring in the semi-humid and semi-arid regions.The results of this study can help to understand the cloud characteristics of the Loess Plateau and provide a reference basis for the simulation of cloud characteristics in the Loess Plateau by regional climate models.

[Objective] To compare the applicability of terrain change monitoring algorithms in the pisha sandstone areas of the loess plateau. [Methods] A branch gully Telagouagou Huangfuchuan was taken as the research object, including digital elevation model of difference (DoD), cloud to cloud (C2C), cloud to mesh (C2M), and multiscale model to model cloud comparison (M3C2). Point cloud data employed to operate the four algorithms were produced using the SfM technique based on images acquired by UAV between July 2022 and March 2023. The impact of point density changes in the accuracy of the employed algorithms was also investigated. [Results] (1) All four algorithms were capable of effectively monitoring large surface changes. Among them, the M3C2 algorithm performed the best with the highest accuracy (R2=0.953, p

Soil erosion is mainly affected by the rainfall characteristics and land cover conditions, and soil erosion modelling is important for evaluating land degradation status. The revised Universal Soil Loss Equation (RUSLE) have been widely used to simulate soil loss rate. Previous studies usually considered the general rainfall characteristics and direct effect of runoff with the event rainfall erosivity factor (Re) to produce event soil loss (Ae), whereas the fluctuation of rainfall intensity within the natural rainfall profile has rarely been considered. In this study, the relative amplitude of rainfall intensity (Ram) was proposed to generalize the features of rainfall intensity fluctuation under natural rainfall, and it was incorporated in a new Re (Re=RamEI30) to develop the RUSLE model considering the fluctuation of rainfall intensity (RUSLE-F). The simulation performance of RUSLE-F model was compared with RUSLE-M1 model (Re=EI30) and RUSLE-M2 model (Re=QREI30) using observations in field plots of grassland, orchard and shrubland during 2011–2016 in a loess hilly catchment of China. The results indicated that the relationship between Ae and RamEI30 was well described by a power function with higher R2 values (0.82–0.96) compared to QREI30 (0.80–0.88) and EI30 (0.24–0.28). The RUSLE-F model much improved the accuracy in simulating Ae with higher NSE (0.55–0.79 vs −0.11∼0.54) and lower RMSE (0.82–1.67 vs 1.04–2.49) than RUSLE-M1 model. Furthermore, the RUSLE-F model had better simulation performance than RUSLE-M2 model under grassland and orchard, and more importantly the rainfall data in the RUSLE-F model can be easily obtained compared to the measurements or estimations of runoff data required by the RUSLE-M2 model. This study highlighted the paramount importance of rainfall intensity fluctuation in event soil loss prediction, and the RUSLE-F model contributed to the further development of USLE/RUSLE family of models.

Terracing is a widely adopted agricultural practice in mountainous regions around the world that aims to conserve soil and water resources. Soil nutrients play a crucial role in determining soil quality, particularly in landscapes prone to drought. They are influenced by factors such as land-use type, slope aspect, and altitude. In this study, we sought to examine the impact of terracing on soil nutrients (soil organic content (SOC), total nitrogen (TN), nitrate-nitrogen (NO3–-N), ammonium nitrogen (NH4+-N), total phosphorus (TP), available phosphorus (AP), total potassium (TK), and available potassium (AK)) and how they vary with environmental factors in the Chinese Loess Plateau. During the growing season, we collected 540 soil samples from the 0 to 100 cm soil layer across five major land-use types, different slope aspects, and varying altitudes. Additionally, a meta-analysis of literature data further corroborated the effective accumulation of soil nutrients through terracing in the Loess Plateau. Our findings are as follows: (1) Terraced fields, regardless of land-use type, showed a significant improvement in SOC and TN content. (2) Soil nutrient contents within terraced fields were predominantly higher on sunny slopes. (3) Terraces at lower altitudes are characterized by elevated SOC concentrations. (4) A meta-analysis of literature data pertaining to terracing and soil nutrients in this region confirmed the effective accumulation of soil nutrients through terracing. The elucidated outcomes of this study offer a profound theoretical underpinning for the accurate planning and management of terraces, the scientific utilization of land resources, and the enhancement of land productivity.

In the Loess Plateau, the impact of abandoned farmland on soil properties and enzyme activity, along with its temporal variations and potential driving factors, remains a mystery. This study was designed to systematically and comprehensively examine the variations in soil enzyme activities, particle size distribution, and stability of soil aggregates at different stages of ecological recovery in the Loess Plateau. Our findings reveal a nuanced temporal pattern: with the progression of cropland abandonment, there is a notable decrease in soil bulk density. Concurrently, a dynamic trend in enzyme activities is observed—initially exhibiting a decline, followed by an increase over extended periods of recovery. Notably, prolonged abandonment leads to marked enhancements in soil structure. Parameters such as the mean weight diameter (MWD) and geometric mean diameter (GMD) of soil aggregates show an overall increasing trend. In terms of the Relative Dissipation Index (RSI), our data indicate a sequence of control > 2 years of abandonment > 4 years > 6 years > 14 years. From this, it can be seen that fallowing may be an effective natural restoration strategy for improving the physical structure of soils in the Loess Plateau and restoring soil nutrients. However, positive changes may take a long time to become evident. [ABSTRACT FROM AUTHOR]

Background: In recent decades, the Loess Plateau is one of the regions in China that urgently needs ecological governance due to the severe situation of soil erosion and land desertification. Due to the impact of climate change and human activities, the threat to the ecological space security of the Loess Plateau has intensified. This paper reveals the time lag effect of ecological engineering construction on the changes in the ecosystem service capacity index of the Loess Plateau, providing a scientific basis and decision-making reference for the sustainable development of the study area and improving the quality and management of ecological engineering construction, which is of great significance for building a solid ecological security barrier on the Loess Plateau. Methods: Based on the hierarchical analysis method, quantitative indicator method, spatial correlation analysis method and two-way fixed effect model, this paper analyzes the temporal and spatial changes of the ecosystem service capacity index of the Loess Plateau under the background of ecological engineering implementation. Results: The results showed that: 1) the vegetation coverage of the Loess Plateau increased with the increase of the area of ecological engineering construction, and showed a fluctuating growth distribution characteristic from southeast to northwest in space; 2) the water conservation capacity index, wind and sand fixation capacity index, biodiversity capacity index and comprehensive service capacity index of the Loess Plateau from 2000 to 2020 all showed exponential growth, which were highly coupled with the growth and change of vegetation coverage area in time and space; 3) the cold spots and hot spots of the ecosystem service capacity index of the Loess Plateau showed a step-by-step decrease of "hot in the south and cold in the north" in spatial distribution; the hot spots and sub-hot spots showed a reciprocating cycle from aggregation to fragmentation in time and space; the cold spots and sub-cold spots were mainly distributed in the northwest region. 4) The changes in the ecosystem service capacity index of the Loess Plateau were mainly affected by factors such as the cumulative project implementation area, urbanization rate and precipitation. Conclusion: The construction of ecological engineering on the Loess Plateau has achieved remarkable results. The growth of vegetation coverage area and ecosystem service capacity index on the Loess Plateau from 2000 to 2020 has promoted the recovery of ecosystem functions. Therefore, we should actively promote the construction of ecological projects to provide scientific decisionmaking references for solving regional ecological security issues. [ABSTRACT FROM AUTHOR]

To investigate the relationship between photosynthetic capacity and soil factors of typical plants in the semi-arid zone of the Loess Plateau and to quantitatively study the response of plant photosynthetic characteristics to soil factors, in this study, we used Li-6400 portable photosynthesis meter to measure the photosynthetic capacity of leaves of different life types of plants and fit their CO2 response curves, and we obtained the maximum carboxylation rate (Vcmax), the maximum electron transfer rate (Jmax), mitochondrial respiration rate in light (Rd), triose phosphate use limitation (TPU) and Jmax/Vcmax ratio, etc. We also applied a GAM model to analyze the relationship between photosynthetic characteristics and soil factors. The results showed that: (1) With the increase of intercellular CO2 concentration (Ci), the net photosynthetic rate (Pn) of different life types of plants increased almost linearly, and Pn increased with the increase of Ci at Ci < 500 μmol/mol, and then the growth rate gradually slowed down; under the condition of the same CO2 concentration, the size of Pn was ranked as herbs > trees > shrubs, and the Pn values of different life types of plants all reached the maximum in May and the minimum in July. (2) The photosynthetic parameters such as Vcmax and Jmax of leaves of trees, shrubs, and herbs were significantly different (P < 0.05), and the Vcmax, Jmax, Rd, and TPU were herb > tree > shrub, and Jmax /Vcmax ratio was shrub > herb > tree. (3) Based on the GAM model, we found that the six environmental factors on Pn were in the following order: Ta > PAR > STP > STN > SWC > SOM, and except for SOM, Pn was significantly and non-linearly correlated with the other environmental factors. Conclusions: Herbaceous plants are very competitive in their habitat. The differences in photosynthetic capacity of different types of plants may be related to their leaf structure and composition. Ta, PAR, SWC, and STN are the main factors affecting the magnitude of Pnmax. Therefore, according to the different degrees of influence of the environmental factors on the photosynthetic capacity of the plants, we can provide reasonable measures of replenishment for plant growth in other months and offer a good solution for the cultivation of plants and vegetation growth of plants in semi-arid areas of the Loess Plateau. It can provide a theoretical basis and data support for the cultivation of plants and the improvement of vegetation survival rate in the semi-arid region of the Loess Plateau. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to reveal the temporal and spatial evolution characteristics of mountain torrent disaster risk and its influencing mechanism on the Loess Plateau over the past 30 years, and to provide a scientific basis for the development of comprehensive prevention and control strategies for mountain torrent disasters on the Loess Plateau. [Methods] Based on the data of rainfall, vegetation cover, population density and so on, the risk assessment system of mountain torrent disaster was established. By integrating GIS and analytic hierarchy process (AHP), the mountain torrent disaster risks on the Loess Plateau in 1990 and 2020 were comprehensively evaluated based on the risk distribution map of each driving factor. [Results (1) The high-risk areas were mainly distributed in the southwest, south and east of the Loess Plateau. These areas had the characteristics of high rainfall intensity, dense population, developed economy and large cultivated land area. (2) During the period from 1990 to 2020, the overall risks of mountain torrent disasters on the Loess Plateau increased, showing that the areas with high risk expanded to its surroundings on the original basis, among which the southeast of Shanxi Province, the northwest of Qinghai Province and the northeast of Inner Mongolia were the most obvious. [Conclusion] The increased rainfall intensity, population density and GDP are the main driving factors on the increase of mountain torrent disaster risks in the past 30 years. It is necessary to continuously strengthen the prevention and control of mountain torrent disasters caused by extreme rainfall. [ABSTRACT FROM AUTHOR]

[Objective] The aim of this study is to elucidate the accuracy and applicability of different algorithms for detecting slope erosion, which can provide a reference for the selection and development of detection methods for soil erosion processes. [Methods] Five plots established on a natural slope in the loess hilly and gully region to conduct runoff scouring experiments. Using TLS data, we calculated erosion and sediment yield by using various methods such as Digital Elevation Model (DEM) of difference (DoD), Cloud to Cloud (C2C), Cloud to Mesh/Model (C2M), and Multiscale Model to Model Cloud Comparison (M3C2), and compared their results. [Results] The results of the uncertainty analysis showed that M3C2 produced the smallest average uncertainty, followed by C2C and C2M, while DoD yielded the largest uncertainty. The sediment yield calculated by the detection algorithms demonstrated that under high flow rates (85, 70 and 55 L/min), there was a significant linear relationship between consecutive sediment yield and cumulative sediment yield derived by the four algorithms and the corresponding measured sediment yield (R²＞0.62, p＜0.05), and M3C2 performed best; under low flow rates (40 and 25 L/min), no significant linear relationships were found between consecutive sediment yield and measured sediment yield, but significant linear relationships were found between cumulative sediment yield and measured sediment yield (R²＞0.91, p＜0.05), and DoD performed best. The spatial distribution of erosion and deposition indicated that C2C, M3C2, and DoD could reflect two stages of erosion evolution on hillslopes and gully slopes (rapid development stage and stable stage), with M3C2 being able to detect subtle topographic changes. However, M3C2 results were subject to ‘voids’ in the blind area of TLS scanning due to not finding corresponding points in the normal direction. [Conclusion] The M3C2 algorithm is more suitable for detecting complex terrain, but it will still fail in the blind spot of scanning, and the algorithm should be improved in the future to help cope with more complex and drastic terrain changes. [ABSTRACT FROM AUTHOR]

Aims: Afforestation is considered an effective strategy to improve soil carbon (C) and fertility in degraded drylands. However, how specific species identities (e.g., conifers or broadleaves) impact C and nutrient concentrations across deep soil layers remains uncertain. Methods: Three most important plantation forests, including plantations of native mono-species Pinus tabuliformis (coniferous species), exotic mono-species Robinia pseudoacacia (broadleaf and nitrogen-fixing species), and their mixed, were selected to explore their effects on soil organic C (SOC) and nutrient concentrations throughout soil profile (0–200 cm) in the Loess Plateau. Results: The results showed that soil C and nutrient concentrations were strongly affected by species identity. Specifically, R. pseudoacacia contained significantly higher SOC, total nitrogen (N), and ammonia N concentrations than other plantations at the top layer (0–60 cm), but R. pseudoacacia contained lower total phosphorus (P) concentrations than other plantations. In the deep layer (60–200 cm), R. pseudoacacia contained lower total N, nitrate N, and total P concentrations than other plantations. There was no significant difference in SOC concentration among plantation types in the deep layer. We found antagonistic effects of tree mixtures on soil P in the top and deep layers. Furthermore, microbial biomass C and N was the primary driver of SOC and N concentration in the top layer, respectively. Conversely, fine root biomass was the primary factor influencing N and P concentrations in the deep layer. This suggests that planting exotic R. pseudoacacia with higher root biomass has the potential to exacerbate soil N and P depletion in the deep layer. Conclusion: Our work emphasizes the key role of species identities in regulating soil nutrient concentrations, especially in the deep layer, and the importance of tree species selection in dryland afforestation. [ABSTRACT FROM AUTHOR]

During the large-scale vegetation restoration on the Loess Plateau, the introduction of exotic species with high water consumption, such as Robinia pseudoacacia L., led to widespread soil desiccation, and resulted in severe drought stress and increasing risk of forest degradation and mortality. Accurate assessment of drought-induced mortality risk in plantation forests is essential for evaluating and enhancing the sustainability of ecological restoration, yet quantitative research at the regional scale on the Loess Plateau is lacking. With a focus on Robinia pseudoacacia L. plantations, we utilized a coupled model of the Biome BioGeochemical Cycles model and plant supply–demand hydraulic model (BBGC-SPERRY model) to simulate the dynamics of the annual average percentage loss of whole-plant hydraulic conductance (APLK) at 124 meteorological stations over an extended period (1961–2020) to examine changes in plant hydraulic safety in Robinia pseudoacacia L. plantations. Based on the probability distribution of APLK at each site, the drought-induced mortality risk probability (DMRP) in Robinia pseudoacacia L. was determined. The results indicate the BBGC-SPERRY model could effectively simulate the spatiotemporal variations in transpiration and evapotranspiration in Robinia pseudoacacia L. stands on the Loess Plateau. The mean APLK and DMRP exhibited increasing trends from southeast to northwest along a precipitation gradient, with their spatial patterns on the Loess Plateau mainly driven by mean annual precipitation and also significantly influenced by other climatic and soil factors. The low-risk (DMRP < 2%), moderate-risk (2% ≤ DMRP ≤ 5%), and high-risk (DMRP > 5%) zones for drought-induced mortality in Robinia pseudoacacia L. accounted for 60.0%, 30.7%, and 9.3% of the study area, respectively. These quantitative findings can provide an important basis for rational forestation and sustainable vegetation management on the Loess Plateau. [ABSTRACT FROM AUTHOR]

The Loess Plateau is an important source of particulate matter pollution in North China. In order to establish and repair shelterbelts and improve their function of inhibiting wind erosion and dust, four typical shelterbelts (Populus simonii, Pinus tabulaeformis Carr., Pinus tabulaeformis Carr. × Populus simonii and Caragana korshinskii Kom.) were selected to investigate the inhibition rate of soil wind-erosion and the reduction rates of PM1, PM2.5 and PM10 by stand type, stand structure and soil properties. A sample plot survey and semi-fixed observation method were used to measure wind speed and particulate matter concentration and to calculate wind protection effect, sand transport rate, vertical flux of particulate matter, wind-erosion inhibition rate and particulate matter reduction rate. The results showed that the Pinus tabulaeformis Carr. forest and Caragana korshinskii Kom. forest had the best windproofing effect, at 2 m (82.9% ± 23.8%) and 0.5 m (54.4% ± 21.5%), respectively. The distribution curve of the sediment flux of shelterbelts is a logarithmic function. The wind-erosion inhibition rate and PM1 reduction rate of the Pinus tabulaeformis Carr. forest were significantly greater than those of other stand types (p < 0.05). The generalized linear mixed model (GLMM) shows that the DBH variation coefficient (CV) can effectively explain the reduction rate of PM1. It is suggested that policies be enacted to add or replace Pinus tabulaeformis Carr. forest in polluted areas to prevent wind erosion and dust. [ABSTRACT FROM AUTHOR]

Runoff and sediment (RAS) are important indicators of soil erosion in a watershed, playing a significant role in the migration of surface material and landform development. Previous studies have extensively documented the effects of trees, shrubs, herbs, and soil on runoff and sediment during erosive rainfall; however, the precise interactions among these factors and their influence on RAS yield within the vegetation hierarchy remain unclear. Using the random forest algorithm and the structural equation model, this research aimed to quantify the interaction of numerous variables within diverse vegetation hierarchies and how they affect RAS, as well as to identify critical indicators that influence RAS. The structural equation model results show that the grass properties have a direct effect on soil properties, and the grass properties and soil properties both affect the canopy properties directly; the soil properties and canopy properties are the main factors influencing runoff and sediment directly. In addition, the grass properties could affect RAS by influencing the soil properties indirectly, and the soil properties could also affect RAS indirectly by influencing the canopy properties. Height difference (HD) between two layers of vegetation had the highest weight of 1.043 among the canopy variables, showing that HD has a substantial effect on RAS. Among the soil properties, soil bulk density and maximum field capacity have a significant impact on RAS. We conclude that canopy properties have the greatest impact on RAS. In the future, more Caragana microphylla Lam and Robinia pseudoacacia Linn plants should be planted to prevent soil erosion. This study provides a scientific basis for vegetation planting management and soil erosion control on the Loess Plateau. [ABSTRACT FROM AUTHOR]

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Phenology is a critical mirror reflecting vegetation growth and has a major impact on terrestrial ecosystems. The Loess Plateau (LP) is a paramount ecological zone in China that has experienced considerable vegetation changes. However, understanding the dynamics of vegetation phenology is limited by ambiguous vegetation interpretation and anthropogenic-induced forces. This study combined the multi-climatic and anthropogenic datasets to characterize the interactions between phenology shifts and environmental variables. The principal findings were as follows: (1) Phenological shifts exhibit spatial heterogeneity and an interannually increasing trend in greenness (R2 > 0.6, p < 0.05). Notably, SOS (the start of the growing season) advances while EOS (the end of the growing season) delays in both the southeastern and northwestern regions. (2) SOS and EOS, primarily in the range of 100–150 and 285–320 days, respectively. Phenological changes vary depending on vegetation types. The forest has an early SOS, within 80–112 days, and a delayed EOS, within 288–320 days. The SOS of shrub is mainly within 80–144 days. (3) EOS shows a strong response to the preseason of each climate variable. Precipitation (R = 0.76), soil moisture (R = −0.64), and temperature (R = 0.89) are the governing determinants in shaping vegetation phenology. In addition, agriculture and urbanization play a significant role in shaping the spatial variations of SOS. These findings provide a basis for a systematic understanding of the processes that affect vegetation growth, which is crucial for maintaining the health and sustainability of arid and semiarid ecosystems. [ABSTRACT FROM AUTHOR]

Water quality is a critical aspect of environmental health, affecting ecosystems, human health, and economic activities. In recent years, increasing pollution from industrial, agricultural, and urban sources has raised concerns about the deterioration of water quality in surface water bodies. Therefore, this study investigated the spatio-temporal distribution of water elements, human health risks of surface water, and pollutant sources at the confluence of the Wei River and the Yellow River. Using 80 samples collected during both wet and dry seasons, the content of the 22 water chemistry indicators was tested. A statistical analysis, Piper diagram, and entropy water quality index were employed to analyze the chemistry indicator content, hydrochemical composition, and water environmental quality of the surface water in the area. Moreover, the health risk assessment model was utilized to evaluate the carcinogenic and non-carcinogenic health risks associated with heavy metal elements in surface water. Finally, correlation heatmaps and a principal component analysis were used to identify potential pollution sources in the study area. The results indicated that C r (VI) and N H 3 - N were the main pollutants during the wet season, while surface water quality during the dry season was mainly influenced by F − . The hydrochemical type in the study area was mainly S O 4 C l - C a M g . The health risk assessment revealed a high carcinogenic risk in the study area, with C r (VI) being the primary heavy metal element contributing to health risks. The correlation and principal component analysis results show that the surface water environment in the study area was influenced by soil characteristics (soils containing F − in the Dalí region, soils containing heavy metals in the Tongguan region), native geological environment (mineral resources and terrain conditions), and industrial activities (ore smelting). This study identified the key pollution indicators, the priority control areas, and the extent of the human health impact of the surface water at the confluence of the Wei River and the Yellow River, guiding targeted management of surface water environments. [ABSTRACT FROM AUTHOR]

In the area of "returning farmland to forest" on the Loess Plateau in China, it is difficult to cultivate artificially planted trees into forests. In the current study, abandoned cultivated land after 10 years of natural restoration served as controls (CK), while the treatments included afforestation periods of 2, 4, 6, 8, and 10 years. Soil samples were collected from various depths: 0–20, 20–40, 40–60, 60–80, to 80–100 cm. The findings revealed that with increasing years of artificial afforestation, soil pH gradually increased, and soil moisture content rose in the 0–20 cm layer while declining in deeper layers (20–100 cm) in the Maxian Mountain region of the Loess Plateau. Moreover, the total carbon, nitrogen, phosphorus, and potassium content initially increased and then decreased with the duration of artificial afforestation, reaching peak values after 8 years. Contents of organic matter, ammonium nitrogen, nitrate nitrogen, available phosphorus, and available potassium in the same soil layer increased with each year of afforestation. However, upon reaching 10 years of artificial afforestation, the effective nutrient content in the 60–80 and 80–100 cm soil layers exhibited a decrease. The values of Integrated Fertility Index (IFI) in different afforestation years were ranked as follows: 8 years > 6 years > 10 years > 4 years > 2 year, but all of them were significantly smaller than those of natural restoration plot CK (P < 0.05). Overall, soil fertility in the Maxian Mountain area of the Loess Plateau increases with each additional year of artificial afforestation. However, when the artificial afforestation period is 10 years, soil fertility decreases and marking a shift from enhancement to decline beyond this duration. [ABSTRACT FROM AUTHOR]

The carbon density of subalpine-alpine grasslands (SGs) is significantly vital to sustaining the carbon cycle in global terrestrial ecosystems. However, on the Loess Plateau of China, it remains unclear how the geographical environment and plant functional groups affect the spatial variation pattern of plant carbon density in these grasslands. Here, nine typical SGs distributed in the eastern Loess Plateau with elevations ranging from 1720 to 3045 m were investigated. The biomass indices from grassland plants of different functional groups were investigated using plot surveys. The Kriging interpolation method was used to explore the spatial variation pattern of plant carbon density along geographical gradients. We found that (1) the total plant carbon density of SGs was 2676.825 g C/m2 on the eastern plateau, with 37.07%, 37.50%, and 25.43% contributed by the northern, central, and southern areas, respectively. Above- (666.338 g C/m2) and belowground (2010.488 g C/m2) carbon density accounted for 24.9% and 75.11% of the total, respectively. (2) At the horizontal scale, the plant carbon density in the northern SGs was high in the northwest and low in the southeast; in the central SGs, it was low in the northwest and high in the southeast; and in the southern SGs, it was high in the southwest and low in the northeast. At the vertical scale, plant carbon density in all SGs decreased with increasing altitude. (3) The carbon density of grasses, forbs, and sedges was 247.419 g C/m2, 26.073 g C/m2, and 23.471 g C/m2, respectively. With increased latitude, the carbon density of all functional groups (grasses, forbs, and sedges) decreased; the carbon density of forbs and grasses increased with increased longitude, while that of sedges decreased; and with increased altitude, the carbon density of all functional groups increased. In conclusion, the spatial variation pattern of plant carbon density in the SGs was not only influenced by the geographical environment but also by the plant functional groups at the horizontal and vertical scales on the eastern Loess Plateau of China. [ABSTRACT FROM AUTHOR]

Evaluating the conservation effectiveness of multiple types of protected areas (PAs) on carbon sequestration services can enhance the role of PAs in mitigating global warming. Here, we evaluated the conservation status and effectiveness of national parks, nature reserves, forest parks, geo-parks, and scenic spots on carbon sequestration within the Loess Plateau throughout 2000–2020. The results show that all existing PA types have good representation and conservation effectiveness on carbon sequestration. Nature reserves are the most representative of carbon sequestration but are the least effective in protecting carbon sequestration and are the only ones that are weekly effective in protecting critical carbon sequestration. The main factors influencing these results are PA size, 2000 precipitation, slope, change rate of evapotranspiration, PA rank, and 2000 evapotranspiration. We suggest upgrading the critical carbon sequestration distribution areas in scenic spots, forest parks and geo-parks to national parks or nature reserves in the future and implementing appropriate protection and restoration measures in low carbon sequestration areas within grassland and wild plant nature reserves to help achieve the goal of carbon neutrality early. [ABSTRACT FROM AUTHOR]

Understanding the spatiotemporal characteristics of heat wave (HW) is vital for both natural systems and human populations. The Loess Plateau is located in a climate transition zone and is highly sensitive to climate change. Therefore, it is crucial to study HW in this region. Based on instrumental measurements, climate model data, atmospheric circulation data and HW metrics, this study comprehensively analyses past and future HW changes in the Loess Plateau and the influencing factors. From 1961 to 2019, the metrics for daytime heat wave(DHW) and nighttime heat wave(NHW) were as follows: duration (9.28/9.72 days), frequency (1.34/1.4 times, mean intensity (6.24/4.69 °C), maximum intensity (7.83/6.05 °C), and cumulative heat (44.45/32.63 °Cd). All metrics displayed an increasing trend (p < 0.05(NHW)). Geographically, the northern Loess Plateau exhibited the highest intensity and cumulative heat, whereas the southern region experienced longer HW. The solar flux index, western Pacific subtropical high area index, and western Pacific subtropical high intensity index were identified as the primary factors influencing HW in the Loess Plateau. By the end of the 21st century, both the duration and cumulative heat of HW are projected to rise significantly. NHW, in particular, will see extended durations and greater cumulative heat compared to DHW. [ABSTRACT FROM AUTHOR]

Machine learning models are widely used for landslide susceptibility prediction (LSP). To better develop a landslide susceptibility prediction model for the Loess Plateau, this study compared different machine-learning models (Logistic regression (LR), support vector machines (SVM), random forests (RF), Naïve Bayes (NB), and multilayer perceptron (MLP)). Using Xunyi County, China as the study area, 1096 landslides were collected and divided into a training set (70%) and a test set (30%). Significant influencing factors were selected from 20 landslide factors using GeoDetector. The relationships between these factors and landslides were determined by normalized frequency ratios. Five trained machine learning models calculated landslide susceptibility indices and generated landslide susceptibility maps. Additionally, the accuracy (ACC), precision (PRE), recall (REC), F1 score, AUC values, LSI distribution characteristics, and overlay analysis of historical landslides with LSM were used to evaluate the performance of the models. The results show that the LSP results of the five models are generally reasonable. The results further indicated that the use of GeoDetector was able to filter out the main factors of eolian landslides, improving the predictive performance of the model and obtaining better LSMs. The RF model had the best overall performance, followed by the SVM, and the MLP model created LSM high susceptibility zones that could contain the highest number of historical landslides. The q-values of factor contributions indicate that elevation, NDVI, rainfall, POI kernel density, and RDLS are the main factors controlling landslides, which need to be paid attention to for landslide control in the Loess Plateau region. The results of this study can provide a reference for the follow-up study of landslide prevention and control, especially landslide susceptibility modeling in the Loess Plateau. [ABSTRACT FROM AUTHOR]

Ecological security pattern is an important spatial way to maintain ecological processes and ensure the stability of ecosystem functions. As the implementation of landscape planning and decision-making, it is critically needed to consider the consistency of differentiated methods and their spatial outputs in the construction of ecological security patterns and the matching and applicability of research objects. From the perspective of integration, we combined the regional topography and landscape characteristics, integrated the morphological spatial pattern analysis and the importance evaluation results of ecosystem services to identify the ecological source, and constructed the ecological security pattern of the Ansai District of Yan'an City, the main implementation area of the Grain-for-Green Project on the Loess Plateau. The results showed that the structural and functional construction methods had low consistency in the identification of spatial protection priority. The integration-oriented method could complement each other and achieve the dual goals of structural connectivity and functional improvement. There were 202 ecological sources in the study area, with a total area of 391.58 km², accounting for 13.3% of the total area of the study area. There were 110 ecological corridors in the study area, with a total length of 599 km, which were mainly distributed around the river channel, showing a distribution pattern of 'short and narrow dense in the north and south, long and wide in the middle'. The structure-function integration method provides new insights for ecological restoration planning of land space and promotes the research of landscape pattern, process and service. [ABSTRACT FROM AUTHOR]

Exploring nutrient limitation in forest soil holds significant implications for forest tending and management. However, current research on nutrient limitation status of microorganisms in Robinia pseudoacacia plantations within the Loess Plateau remains insufficient. To investigate soil microbial nutrient limitation of R. pseudoacacia plantations on the Loess Plateau, we selected R. pseudoacacia plantations with different afforestation time series (15, 25, 35, and 45 years) and a pile of barren slope cropland (control) in Yongshou County, Shaanxi Province as the research objects. We analyzed the contents of soil organic matter, total nitrogen, and total phosphorus, and the activities of β-1, 4-glucosidase (BG), cellobiose hydrolase (CBH), leucine aminopeptidase (LAP), β-1,4-N-acetylglucoside (NAG) and phosphatase (AP). We analyzed the soil nutrient limitation by stoichiometry and enzyme metrology. The results showed a shift in soil pH from alkaline to acidic during vegetation restoration process, and that total phosphorus exhibited a gradual decrease over the course of 0 to 25 years. Soil organic matter, total nitrogen and enzyme activities exhibited an increasing trend during the same time frame. However, between 25 and 45 years of age, soil total phosphorus, soil organic matter, total nitrogen, AP and LAP gradually declined while NAG, BG, and CBH initially increased and then decreased. Notably, the values of (BG+CBH)/(LAP+NAG), (BG+CBH)/AP and (LAP+NAG)/AP in R. pseudoacacia plantations were higher than the global average throughout the process of vegetation restoration. In the study area, the vector length was less than 1 and gradually increased, indicating that a progressive increase in microbial carbon limitation during the process of vegetation restoration. The vector angle exceeded 45° and exhibited an overall decreasing trend, suggesting that soil microorganisms were constrained by phosphorus (P) with a gradual deceleration of P limitation, without any nitrogen (N) limitation. The restoration of R. pseudoacacia plantation resulted in significant change in soil physical and chemical properties, while the time series of afforestation also influenced nutrient limitation of soil microorganisms. [ABSTRACT FROM AUTHOR]

Forests make an important contribution to the global carbon cycle and climate regulation. Caijiachuan watershed false acacia (Robinia pseudoacacia Linn.) plantation forests have been created for 30 years, but a series of problems have arisen due to the irrationality of the density involved at that time. To precisely assess the contribution of R. pseudoacacia plantations with different densities to this cycle, we measured the diameter at breast height (DBH), tree height (H), biomass, and carbon stocks in trees, shrubs, herbs, litter, and soil across different density ranges, denoted as D1 = 900–1400, D2 = 1401–1900, D3 = 1901–2400, D4 = 2401–2900, and D5 = 2901–3400 trees ha−1. In order to achieve the purpose of accurately estimating the biomass, carbon stocks and the contribution rate of each part in different densities of R. pseudoacacia plantations were measured. The results are as follows: (1) Both DBH and H decreased with increasing density, and field surveys were much more difficult and less accurate for H than DBH. Based on the two allometric growth models, it was found that the determination coefficient of the biomass model that incorporated both H and DBH (0.90) closely resembled that of the model using only DBH (0.89), with an error margin of only 0.04%. (2) At the sample scale, stand density significantly affected R. pseudoacacia stem biomass and total biomass. At the individual plant scale, stand density significantly affected R. pseudoacacia organ biomass. Increasing stand densities promoted the accumulation of vegetation biomass within the sample plot but did not improve the growth of individual R. pseudoacacia trees. The stem biomass constituted the majority of the total R. pseudoacacia biomass (58.25%–60.62%); the total R. pseudoacacia biomass represented a significant portion of the vegetation biomass (93.02%–97.37%). (3) The total carbon stock in the sample plots tended to increase with increasing stand density, indicating a positive correlation between density and the carbon stock of the whole plantation forest ecosystem. Hence, in future R. pseudoacacia plantations, appropriate densities should be selected based on specific objectives. For wood utilization, a planting density of 900–1400 trees ha−1 should be controlled. For carbon fixation, an initial planting density of 2900–3400 trees ha−1 should be selected for R. pseudoacacia. This study provides theoretical support for local forest management and how to better sequester carbon. [ABSTRACT FROM AUTHOR]

Although the theory of ecosystem services (ESs) is important for guiding land-use planning, knowledge of ESs trade-offs and supply–demand mechanisms is still lacking, and the characteristics of the correlation between the size of trade-offs and the balance between supply and demand along the precipitation gradient have not yet been clarified. In order to supplement this area of knowledge of ESs, we selected 30 small watersheds in high-, medium- and low-precipitation areas as study units. A biophysical model and socio-economic data were used to calculate supply and demand for carbon sequestration, soil conservation and water yield. Redundancy analysis and regression analysis were used to study the ESs trade-offs, the supply–demand dynamics, and the characteristics of their correlation. The results were as follows. (1) The supply and balance between supply and demand of the three ESs, the trade-off between carbon sequestration and water yield and the trade-off between soil conservation and water yield trended downwards from the high-precipitation area to the medium-precipitation area to the low-precipitation area. (2) The primary factors influencing balance between supply and demand with regard to carbon sequestration in high-, medium- and low-precipitation areas were population density and soil organic-matter content, and the size of the conditional effects were greater than 53%. The dominant factor affecting the balance between supply and demand with regard to soil conservation in the three precipitation areas was slope gradient, and the conditional effect was greater than 40%. The most significant determinants of balance between supply and demand with regard to water yield in the three precipitation areas were grassland area, forest area and precipitation, and the conditional effects were greater than 22%. (3) The most significant determinants of the trade-off between carbon sequestration and water yield in high-, medium- and low-precipitation areas were forest, soil organic-matter content and population density, and the conditional effects were all greater than 45%; the primary factors affecting the trade-off between soil conservation and water yield in high-, medium- and low-precipitation areas were grassland and slope gradient, and the conditional effects were all greater than 24%. (4) The relationship between the balance between supply and demand and trade-off size often followed a quadratic function; the next-most-common relationship was a monotonous nonlinear response, and a linear response relationship was relatively rare. This study revealed the factors influencing balance between supply and demand and trade-offs with regard to ESs and the characteristics of their correlations in areas with different degrees of precipitation, which provided a new idea for the synchronous regulation of ESs in the context of conflicts and supply–demand imbalance. [ABSTRACT FROM AUTHOR]

Changes in water resource storage are inevitable due to climate change and human activities, thus understanding alterations in water storage within a specific region is imperative for the planning and management of water resources. Data from the Gravity Recovery and Climate Experiment (GRACE) satellite mission are extensively employed to analyze large-scale total terrestrial water storage anomalies (TWSA). In this study, we derived a more reliable TWSA using different types of GRACE gravity models, which served as the basis for evaluating spatial and temporal variations in total terrestrial water storage and its hydrological components (soil moisture and groundwater) across the Loess Plateau. Additionally, we analyzed the impact of natural and anthropogenic influences on water storage in the Loess Plateau, categorizing them into primary and secondary influences, utilizing data on climate and human activities. The findings revealed a declining trend in the overall TWSA of the Loess Plateau, with a rate of decrease at - 0.65±0.05 cm/yr from 2003 to 2020 (P<0.01). As the direct factors affecting TWSA, soil moisture dominated the change of TWSA before 2009, and groundwater dominated the change of TWSA after 2009. Spatially, there was variability in the changes of TWSA in the Loess Plateau. More in-depth studies showed that soil moisture changes in the study area were primarily driven by evapotranspiration and temperature, with precipitation and vegetation cover status playing a secondary role. Human activities had a secondary effect on soil moisture in some sub-regions. Population change and agricultural development were major factors in altering groundwater storage in the study area. Other than that, groundwater was influenced by natural factors to a limited extent. These findings provided valuable insights for local governments to implement proactive water management policies. [ABSTRACT FROM AUTHOR]