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• Evergreen coniferous forestlands increased the complexity of fungal networks. • Topsoil organic carbon fractions shaped complex lipid metabolism pathways. • Specific keystone taxa were potential drivers for soil water repellency. Soil water repellency (WR) is an important hydrological function in the terrestrial water cycle as it prevents water from penetrating into the soil and exacerbating soil erosion. Vegetation restoration may greatly affect WR by increasing soil organic carbon (OC) storage and altering microbial community composition in response to environmental stressors in the loess hilly areas of China. Yet, the regulating mechanisms of WR by changes in microbial functional profiles across land use types in these regions are poorly characterized. In this work, solid-state13C nuclear magnetic resonance (NMR) spectroscopy and shotgun metagenomics sequencing were applied to systematically assess the effects of land use types on the OC fractions, soil bacterial and fungal community composition, as well as microbial functional profiles. We found that artificial evergreen coniferous forestland caused more severe WR and increased the complexity of fungal networks. Besides, the artificial evergreen coniferous forestland had larger impacts on labile OC fractions, microbial communities,and lipid metabolic pathways in topsoil compared to other land use types. What's more, keystone genera (e.g., Conexibacter , Streptomyces , and Sphaerobolus) and functional genes (ACAT , atoB , ACSL , fadD , ACADM , acd , paaF , echA , and FAS2) were driven by soil properties that contributed significantly to WR. Collectively, our results indicate that topsoil OC fractions interact with keystone taxa to influence WR by regulating functional genes in lipid metabolic pathways. These findings greatly boost our understanding of assessing the SWR risk against the backdrop of climate change and lay a theoretical foundation for formulating rational vegetation restoration management strategies based on variations in SWR of forest (grassland) ecosystems on the Chinese Loess Plateau. [ABSTRACT FROM AUTHOR]

• Wetlands topsoil can sequester more C than farmlands and forestlands. • Soil water content was important factor affecting microbial abundance and enzyme activity. • Higher soil water content can increase soil C storage by stimulating C fixing enzyme activity. • Soil C storage were negatively driven by soil bacterial abundance under different land-use. Soil carbon storage plays a crucial role in mitigating the climate warming and is significantly impacted by the land use pattern. To better understand soil carbon stability and the underlying microbial mechanism, based on qPCR, ELISA, and fluorescence techniques, the effects of land use changes on soil microbial abundance, enzyme activity, and soil carbon storage were investigated in the complex ecosystems of cropland, forestland, and wetland along three typical river (Wolvlan river, Bielahong river, Wusuli river) basin in Sanjiang Plain, China. We hypothesised that croplands soil carbon storage is lower than forestlands and wetlands, which is regulated by soil water content, microbe and enzyme activity. Results showed that topsoil TC in wetlands (85.54 mg·g−1) was higher than those in croplands (33.46 mg·g−1) and forestlands (46.13 mg·g−1). Topsoil water content increased 73.90 % and 71.64 % in wetlands than in farmland and forestlands, respectively. Additionally, reclamation diminished topsoil carbon storage. In croplands, soil dissolved organic carbon, microbial biomass carbon, microbial biomass nitrogen, available nitrogen, bacterial abundance, and soil enzymes (i.e., RubisCO, β-glucosidase, cellobiohydrolase, 1,4-N-acetylglucosaminidase and acid phosphatase) activities were substantially lower than those in wetlands. Structural equation modeling showed that soil carbon storage was positively related to soil water content and RubisCO activity but negatively related to soil bacterial abundance. Soil water content had the largest standardised total positive effect coefficient and indirectly influenced soil carbon storage by affecting RubisCO activity. Soil depth had a greater effect on SMC, hydrolase and site had a greater effect on bacteria and fungi abundance. The results highlight that the alteration of carbon fixing enzyme activity by soil water content is a crucial mechanism for soil carbon sequestration in response to land-use change. Management strategies that conserve natural wetlands, increase soil water content and minimize land disturbance would be effective in maintaining soil carbon stocks. [ABSTRACT FROM AUTHOR]

[Display omitted] • The mixed planting of shrubs and grasses improved soil properties and permeability within 10 years. • Mechanized agricultural reclamation faced challenges like high bulk density and low permeability. • Soil pore conditions mainly controlled soil permeability in mining areas. The impacts of various reclaimed mine land use patterns on the soil properties and infiltration capacity of mine areas remain incompletely understood. This study was conducted in the northern Loess Plateau to assess the effects of reclamation patterns, specifically vegetation (shrub grassland planted for 3, 6, and 10 years) and agricultural reclamation (mechanized and non-mechanized farmland, both cultivated for 10 years), on the soil properties and permeability of an open-pit coal mine. Original grassland (OG) and farmland (OF) were used as controls. The results show that after 6 years of vegetation reclamation, the soil bulk density (BD, 1.38 g·cm−3), total porosity (TP, 47.88 %), and infiltration rates approached levels similar to those of the OG. After 10 years, the organic matter content (SOM, 8.37 g·kg−1) and average weight diameter (MWD, 0.82 mm) were restored almost to those of the OG. In comparison, after 10 years of agricultural reclamation, SOM (9.22–9.38 g·kg−1) approached the level of the OF. However, compared with the OF, the BD and MWD of mechanized farmland increased significantly by 17.37 % and 154.96 % (P < 0.05), respectively, and the infiltration rates of mechanized and non-mechanized farmland decreased significantly (P < 0.05). Soil porosity was the most important factor affecting soil permeability, accounting for 65.9 % of change in permeability. In conclusion, vegetation reclamation, particularly mixed shrub and grass, led to more pronounced improvements in soil properties and permeability in mining areas compared with agricultural reclamation over a period of 10 years. However, heavy agricultural machinery has a detrimental effect on the soil properties and infiltration capacity of mining areas and should be carefully monitored. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vegetation restoration on the Loess Plateau increased the extend and depth of infiltration. • Vegetation restoration on the Loess Plateau has altered the pattern of uniform water infiltration, resulting in a distinct preferential flow in the infiltration processes. • Mixed-mode afforestation is better than single-dominant-species afforestation to promote precipitation infiltration. • The preferential flow phenomenon was more pronounced in the natural secondary forest than that in plantation forests. In order to improve the fragile ecological environment, the Loess Plateau region of China has implemented a large number of long-term forest vegetation restoration projects. Infiltration, as an important part of the hydrological cycle, is also changing with vegetation restoration, and a comprehensive study of these changes is an essential aspect of evaluating the effectiveness of vegetation restoration. In the study, three typical forest vegetation types in the Loess Plateau were selected to investigate and analyse infiltration characteristics and infiltration patterns by staining tracer experiments. The results showed that (1) vegetation restoration increased the extend and depth of infiltration. (2) The extent of infiltration in mixed plantation forest of Pinus tabulaeformis and Robinia pseudoacacia was better than that in pure Pinus tabulaeformis plantation forest. (3) Vegetation restoration resulted in more pronounced preferential flow phenomenon in the infiltration processes. (4) The preferential flow phenomenon was more pronounced in the natural secondary forest than in plantation forests, especially if the amount of infiltrated water was low. (5) The extent of infiltration was mainly influenced by the infiltration water volume, soil water content, and total soil porosity; and the degree of preferential flow development was mainly influenced by the infiltration water volume, soil organic matter, and root distribution. At present, vegetation restoration on the Loess Plateau can play a role in promoting precipitation infiltration, and mixed-mode afforestation is better than single-dominant-species afforestation to fulfil this function of forests. [ABSTRACT FROM AUTHOR]

• Natural grasslands improve soil infiltration capacity in both plant and bare patches. • Patchy mosaic patterns make infiltration heterogeneity and redistribute water on slope scale. • Plant with tap root systems produce more effective macropores as preferential flow paths. • Fine roots have a significantly negative effect on the soil infiltration capacity. Soil infiltration capacity is an important factor affecting soil moisture, and is of great significance to plant growth and groundwater recharge in arid and semiarid areas. Patchiness of grasslands widely exist and have a crucial effect on hydrological processes in water-limited regions. This study investigated soil infiltrability under natural grasslands with patchy mosaic patterns based on a series of in-situ tests. Two dominated natural restoration vegetation communities (Bothriochloa ischaemum (B. ischaemum) with fibrous root systems and Artemisia gmelinii (A. gmelinii) with tap root systems) and abandoned land (as control) were selected in the loess hilly and gully region of the Loess Plateau, China. The results showed that natural restoration grasslands significantly improved soil infiltrability in both plant and bare patches, and the emergence of patchy mosaic patterns can result in infiltration heterogeneity to redistribute water on a hillslope scale. Compared to B. ischaemum , A. gmelinii are more likely to facilitate the formation of preferential flow, contributing to the increased soil infiltration rates. The initial, steady and average infiltration rates (IIR , SIR , and AIR , respectively) and soil infiltration capacity index (SIC) were all negatively correlated with both root length density (RLD) and root surface area density (RSAD) of fine roots (diameter < 2 mm) but positively correlated with those of coarse roots (diameter ≥ 2 mm). The main factors influencing the infiltration capacity were the mean weight diameter in the 10−20 cm layer and the RSAD of the fine roots in the 0−20 cm layer, which can explain 98.6 %, 81.7 %, 63.9 %, and 91.3 % of the total variance of IIR , SIR , AIR , and SIC , respectively. This work highlights the important roles of patchy mosaic patterns in affecting soil water redistribution and the stabilization of ecological systems, providing a scientific basis for vegetation selection in the process of vegetation restoration in water-limited regions. [ABSTRACT FROM AUTHOR]

• NTSMFI enhanced soil moisture harvesting and boosted crop yields. • NTSMFI reduced soil N 2 O emissions and increased soil N 2 O emission efficiency. • NTSMFI reduced SNE because of enhanced soil moisture harvesting and improved soil nutrient status. • NTSMFI treatment is a promising environmental cleaner production strategy in irrigated areas. Intercropping can improve system productivity, but the effect of intercropping integrated with conservation tillage practices on soil N 2 O emissions remains unclear at the present stage. A 4-yr field experiment was performed in northwest China to examine soil moisture harvesting, soil nutrient status, and soil N 2 O emissions of wheat-maize intercropping with stubble residues and films management. We found that intercropping increased crop yields and reduced soil N 2 O emissions over monocultures. Across the intercropping treatments, NTSMFI (no-tillage with mulching stubbles and re-using residual films) and NTSSFI (no-tillage with standing stubbles and re-using residual films) boosted grain-yields by 13.8–17.1 % and 12.9–15.4 % over CTFI (conventional tillage without returning stubbles and mulching new films). NTSMFI and NTSSFI reduced soil N 2 O emissions by 18.4–28.7 % and 15.5–24.9 % compared to CTFI, respectively. So, NTSMFI and NTSSFI obtained a higher soil N 2 O emission efficiency than CTFI. The greater effect on soil N 2 O emissions reduction was detected in NTSMFI, and decreased by 5.1–5.4 % over NTSSFI. The main reason for NTSMFI to improve grain-yields and reduce soil N 2 O emissions was to enhance soil moisture harvesting and optimize the soil nutrient status. Compared to CTFI, NTSMFI increased the ratio of transpiration to evaporation by 14.4–32.0 %, improved soil organic carbon and total nitrogen concentrations, and soil C:N ratio of 0 to 60 cm soil depth by 14.1 %, 7.1 %, and 6.5 %, respectively. Adopting an environmentally clean strategy exemplified by NTSMFI was recommended as an effective technique for increasing-yields and reducing soil N 2 O emissions in arid irrigated regions. [ABSTRACT FROM AUTHOR]

• With increasing water temperature, the stability of aggregates decreases. • Parent material affects the sensitivity of aggregate stability to water temperature. • The soil erosion resistance decreases with the increasing water temperature. Water temperature has an important effect on soil aggregate stability. In this study, six soils derived from different parent materials in the hilly region of southern China were selected, and the mean weight diameter (MWD), geometric mean diameter (GMD), and soil erodibility (K value) were measured under different water temperature conditions. The aim of this study was to investigate the influence of water temperature on soil aggregate stability and erodibility. As the water temperature increased from 5 °C to 40 °C, the average content of >5 mm water-stable aggregates decreased by 57.13 %, while the average content of <0.25 mm water-stable aggregates increased by 214.41 %. The MWD and GMD of the six different parent soil types exhibited a decreasing trend with increasing water temperature. The trend of the K value was opposite to that of these values. The influence of water temperature on soil aggregate stability is mainly attributed to the thermal effect on the viscosity of soil water and the expansion of clay minerals. As the water temperature increases, the water viscosity coefficient, water density and water surface tension gradually decrease. Moreover, the response of soil aggregate stability and erosion resistance to water temperature varies with soil depth and parent material type. The topsoil exhibits greater sensitivity to water temperature than does the subsoil. Shale (SH) soils and quartz sandstone (QS) soils exhibited higher sensitivities, and Quaternary red clay (QRC) soils exhibited the lowest sensitivity to water temperature among the six soils. This difference is mainly attributed to differences in the contents of expansive clay minerals and organic matter. These results indicate that soil aggregate stability and erosion resistance decrease with increasing water temperature, which may be one reason for severe soil erosion under extremely high temperature and rainfall conditions in the southern red soil hilly region during summer. [ABSTRACT FROM AUTHOR]

[Display omitted] • Vegetation restoration decreased deep soil water storage in the Loess Plateau. • Revegetation increased steady infiltration but reduced initial and mean rates. • Soil infiltration rates exhibited gradual decline trends along the slope. • The effect of vegetation type on infiltration was higher than slope position. • Soil water and clay content were key factors influencing infiltration rates. Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems. [ABSTRACT FROM AUTHOR]

[Display omitted] • A total of 680 samples of SOC in coastal China were collected and analyzed. • The SOC tended to decrease in first 10 years and then increase after reclamation. • The SOC in different land use types after reclamation was no significant variation. • Soil moisture and nitrogen are most important contributors affecting coastal SOC. As an important blue carbon pool, the content, dynamics, and related hydrological environment of coastal soil organic carbon (SOC) are extremely vulnerable to coastal reclamation; however, a full understanding of this is still lacking, mainly due to the heterogeneity in space. In this study, a dataset encompassing 680 samples gathered from 128 literatures related to SOC variation in China's coastal areas has been constructed. Moreover, meta -analysis combined with structural equation model have been adopted to quantitatively explore the characteristics and causal mechanism of SOC change following reclamation. The results show that: (1) After reclamation, reclamation history has become an overriding control variable dominating all environmental factors, including soil physical and biochemical factors, and directly alters the content and dynamics of SOC. The SOC has tended to decrease substantially within first 10 years after reclamation and then increase significantly over time. After reclamation, forest and paddy generally have a positive effect on SOC. (2) In natural saltmarshes (before reclamation), soil biochemical factors are the dominant forces driving SOC. However, after reclamation, soil physical factors have played an increasingly important role in SOC variation, of which soil moisture is a relatively important contributor. Total nitrogen is another driving force controlling the variation of SOC acting as a gate valve role. (3) For coastal carbon sequestration, cultivating terricolous salt-tolerant vegetation to establish integrated high salinity eco-system in reclaimed zones, wetland silting promotion projects should be encouraged in natural salt marshes. And, land uses of forest and paddy should be popularized for promoting SOC in reclaimed zones. [ABSTRACT FROM AUTHOR]

• Soil erosion rate was 3 times greater on the south-facing hillslope as compared to the north-facing hillslope. • Soil water content was the dominant factor causing the difference in erosion rates under a water-limited condition. • Greater soil erosion rates resulted in elevational distributions of soil physicochemical properties on the south-facing hillslope. Soil erosion causes serious grassland degradation in the Three-River Headwater Region (TRHR) of the Qinghai-Tibet Plateau. Identifying source areas of erosion is important, including understanding the influences of hillslope aspect on soil erosion. However, the effect of hillslope aspect on soil erosion is a much-debated process, wherein contrasting results were previously reported. We hypothesized that aspect-induced differences in environmental variables will be related to differences in erosion magnitude and spatial pattern, and that these differences will impact soil physiochemical characteristics as well. To test this hypothesis, soil samples were collected at conjoined south- and north-facing hillslopes along elevational profiles in a small watershed in Yushu County, with measurements of soil water content (SWC), soil organic carbon (SOC), soil organic matter (SOM), soil particle size distribution, soil total nitrogen (STN) and phosphorus (STP). Soil erosion rate was estimated using 137Cs technology. The results showed that soil erosion rates of the two hillslopes ranged from 0.073 to 10.83 t ha-1 yr-1, and were 3 times greater on the south-facing hillslope. Soil water content ranged from 7.6% to 76.8% on the two hillslopes with lower values on the south-facing hillslope due to the greater solar radiation. By Spearman correlation analysis and path analysis, we concluded that lower soil water content on the south-facing hillslope restricts vegetation growth, and hence resulting in greater soil erosion under the case where vegetation growth is dominantly controlled by water availability. Greater soil erosion on the south-facing hillslope caused greater surficial accumulation of coarser materials and greater loss of soil nutrients, which are expected to complicate the hydrological erosion process. Moreover, the downslope increased soil erosion rate should be fully considered in conservation practices. These results will improve our understanding of the interaction and feedback mechanisms between soil characteristics, vegetation function, and soil erosion in the TRHR. [ABSTRACT FROM AUTHOR]

• Surface and bedrock topography are closely coupled in shallow soil-covered plot. • Soil moisture in thick soil plot is notably affected by the surface topography. • Runoff in thinner soil plot is remarkably affected by the bedrock topography. • Soil thickness is a critical factor in distinguishing hydrological processes. Topography plays a crucial role in predicting rainfall-runoff processes under climate change, as it affects the spatial distribution of water flow pathways. However, understanding the potential impact of high micro-topography heterogeneity on runoff generation remains challenging. We conducted high-resolution monitoring of soil moisture, instantaneous water table, and subsurface runoff in two 3D plots with different soil thicknesses (66 cm vs. 35 cm) in the karst region of southwest China. The topographic features were characterized by the soil thickness, relative elevation, and topographic wetness index obtained from a 1 × 1 m grid. The topography of the shallow-soil plot (SSP) exhibited a higher level of complexity, with a greater variability (approximately 80.0 %) in soil thickness compared to that of the deep-soil plot (DSP; approximately 61.5 %). Additionally, the SSP was prone to forming a micro-topography characterized by a combination of exposed bedrock and soil cover. In DSP, the variation in soil moisture was strongly controlled by surface topography, with elevation contributing to 52 % and 81 % of the explanation for the soil moisture at 30 cm and soil–bedrock interface, respectively. In SSP, the contribution of topography to the variation in soil moisture did not exceed 31 %. The controlling effect of topography on runoff is highlighted in SSP, with the contribution rates of surface and bedrock relative elevation reaching 79% and 97%, respectively.The weaker water storage capacity of the SSP resulted in a higher volume of subsurface runoff (161 t vs. 116 t) and frequency of runoff events (2248 vs. 1994) compared to the DSP. Accordingly, this study emphasizes that the soil–bedrock spatial heterogeneity will control the relationship between soil moisture, subsurface runoff, and terrain, which will contribute to providing a basis for flood prediction and model simulation in regions with complex topography. [ABSTRACT FROM AUTHOR]

• Factors affecting spatial heterogeneity of WSA, MWD and K factor are clarified. • Soil property, terrain and land use contribute to 47%, 41% and 9% of total variation. • Influencing network and paths of factors driving WSA, MWD and K are confirmed. • Terrain signally affects WSA, MWD and K by altering soil nature and land use pattern. Soil aggregate stability and erodibility reflect soil resistance to erosion. Although the factors influencing soil aggregate stability and erodibility have been extensively studied, the driving effects of these factors and their interactions remain limited. 184 sampling sites were selected in topsoil (0–20 cm) of a small watershed (1.42 km2) in a Mollisol watershed to measure soil bulk density (BD), soil porosity (SP), soil moisture content (MC), soil organic carbon (SOC), total nitrogen (TN), >0.25 mm water stable aggregates content (WSA > 0.25), mean weight diameter (MWD) and K factor. Pearson correlation analysis, semi-variance function, redundancy analysis (RDA), and structural equation model (SEM) were used to quantify the impact of environmental variables (individual and interaction) on the spatial variations of WSA > 0.25 , MWD, and K factor. The findings indicated that higher values of WSA > 0.25 and MWD are observed in the central and western watershed, while the K values tend to be lower in areas with high WSA > 0.25 and MWD values within the watershed. The Exponential model optimally described WSA > 0.25 , MWD, and K factor with C 0 /(C + C 0) indicating moderate spatial dependence for MWD (39.79 %) and K factor (42.86 %), while strong spatial autocorrelation for WSA > 0.25 (7.23 %). Soil properties (moisture content, silt content, and bulk density), topography (elevation, SPI, and slope), and land use contributed 46.6 %, 41.4 %, and 9.1 % of the spatial variation in WSA > 0.25 , MWD, and K factor, respectively. SEM revealed that silt content, SOC, and water condition played a fundamental role in controlling the spatial variability of WSA > 0.25 , MWD, and K factor. Topography exerted both direct or indirect effects by coupling land use or soil properties spatially. Land use had direct or indirect effects on WSA > 0.25 and K factor through regulating MC, but it primarily influences MWD indirectly through impacting MC. These results could clarify the roles and influencing paths of factors controlling the spatial heterogeneity of WSA > 0.25 , MWD, and K factor, contributing to optimizing land management strategies. [ABSTRACT FROM AUTHOR]

• Freeze-thaw cycles varied as a function of the extent of vegetation cover. • Migration of soil water was greatest with low vegetation cover. • Reallocation of soil water caused temperature in the soil complex to vary. • Freeze-thaw cycles promoted evaporation of soil water in the plant-rooting zone. Freeze-thaw events can lead to the upward migration of shallow groundwater in recharging the upper soil profile. However, their effects on soil water movement in areas of deep groundwater is not entirely known, especially in arid and semiarid regions of the world. This study analyzed the soil hydrothermal coupling at two desert sites in the Mu Us Sandy Land (northwest China), noted for their differences in surface scrub-vegetation cover, one with 80 % cover and another with 40 % (sites A and B, respectively). The work consisted of collecting soil temperature and moisture measurements at the two sites, both renowned for their deep watertable. The results showed that the freezing period at both sites was about 3–6 times longer than the thawing period, and that the duration of uniform freezing was inversely related to the degree in surface vegetation cover. During the two freezing periods of 2017–2019, as much as 3.87 (or 21.9 %) and 7.37 mm (42.2 %) of soil water was observed to have migrated upwards from the lower soil layers. Altogether, the total distance traveled by the soil water exceeded 180 cm. Also, about 33.2 (site A) and 22.9 mm of soil water (site B) were depleted because of evaporation in the first 185 cm of the soil complex during the two freeze–thaw events. Extent of vegetation cover, initial soil moisture profile, and soil texture influenced the quantity of water lost from individual soil layers due to evaporation and between soil-layer water exchanges. Soil water migration also affected changes in soil temperature in the range of −12.1 to 4.8 °C within the first 185 cm of the soil complex. Changes in soil temperature were responsible for decelerating freezing and thawing processes, prolonging soil water reallocation processes in the soil. Overall, freeze–thaw events increased the amount of shallow soil water losses due to evaporation, triggering a corresponding decline in soil water in the plant-rooting zone. This drop could conceivably lead to a reduction in sprouting and growth of spring vegetation, further degrading affected sand-dominated desertlands. This information may provide insight into the hydrological response of freeze–thaw events in arid regions, as well as provide useful information in guiding afforestation efforts in associated desertlands. [ABSTRACT FROM AUTHOR]

[Display omitted] • The size of the carbon sink across SWC has increased quadruply. • The contribution of CCR to the regional carbon sink was increasing. • Water and temperature controls on the karst carbon sink varied with the lithological background. South-West China (SWC) is a pivotal region for global greening, recognized as having great carbon sink potential. Multiple evidence underscores the expanding contribution of SWC's carbon sink to the global carbon sink enhancement. However, our understanding of carbon sink dynamics and the response to climate across bedrock remains limited. In this study, we investigated the divergence in trends in carbon sink across bedrocks, evaluating their respective contributions of bedrocks to the overall carbon sink in SWC. Additionally, we assessed the dominant climatic factors and examined how bedrocks shape the response of carbon sink to climate change. Our results revealed a notable increase in the regional carbon sink, with an average rate of 3.58 TgC/yr from 1981 to 2019. Continuous Carbonate Rocks (CCR) exhibited the highest increased rate of total carbon sequestration (1.57 TgC/yr), surpassing Discontinuous Carbonate Rocks (DCR) by threefold. Non-karst areas contributed the most to both the mean and interannual variations of the overall carbon sink, with CCR exerting the most contribution to the trends. Over time, the contribution of CCR to the overall carbon sink escalated, while the contributions of DCR and non-karst declined. All bedrocks displayed negative correlations between NEP and temperature, with DCR showing higher susceptibility. Non-karst areas experienced adverse impacts from vapor pressure deficit, while CCR benefited from positive soil moisture effects. Our findings implied that bedrock indeed played a critical role in the variations in NEP and the response of NEP to climate change. Bedrock regulated climatic controls on carbon sink through soil water availability as soil water availability is affected by the lithology of basement carbonate. This novel understanding emphasizes the necessity for tailored ecological restoration initiatives that consider the distinctive lithological features of the karst ecosystem, and holds significance for implementing ecologically sound projects in karst regions. [ABSTRACT FROM AUTHOR]

• Land use types determined deep soil water redistribution. • Soil moisture in abandoned land was strongly affected by rainfall. • Decreased rainfall and soil drying reduced the growth of forage and shrubs. • Farmland in terraces and abandoned land on slopes were the ideal use types. The land-use change affects soil hydrological processes in semi-arid areas. Investigating the impact of precipitation change on soil moisture in different land use types (LUTs) is conducive to water resource management and ecological restoration. The volumetric water content (VWC) at 0–300 cm soil profile, meteorology data, and vegetation aboveground biomass were continuously observed from 2018 to 2022 in five terraced and three sloped LUTs. The results showed that soil moisture was affected by precipitation, vegetation, antecedent soil water, soil properties, and artificial management measures. There were significant differences in soil moisture among these land use types (P < 0.05), with the priority order of multi-year profile average VWC at 0–300 cm depth was farmland in the slope (FAS) (0.22 ± 0.01 cm3 cm−3) > bare land in the terrace (BAT) and farmland in the terrace (FAT) (0.19 ± 0.01 cm3 cm−3) > abandoned land in the slope (ABS) (0.18 ± 0.02 cm3 cm−3) > abandoned land in the terrace (ABT) (0.13 ± 0.02 cm3 cm−3) > forage land in the slope (FOS) (0.12 ± 0.02 cm3 cm−3) > forage land in the terrace (FOT) and shrubland in the terrace (SHT) (0.10 ± 0.01 cm3 cm−3). Except for BAT, soil water storage (SWS) in other LUTs decreased in 0–300 cm soil profile from 2018 to 2022. There were no or slight soil desiccations in FAS, BAT, ABS, and FAT, moderate soil desiccation in ABT, and serious soil desiccation in FOS, FOT, and SHT. The VWC, SWS, and soil desiccation index (SDI) of all LUTs were positively correlated with precipitation, especially at 0–100 cm depth. Precipitation threshold response to soil desiccation alleviation was determined to be 98–116 mm month−1. Moreover, aboveground biomass of FOT, ABT, and SHT exhibited a significant correlation with both soil moisture and precipitation (P < 0.05). Therefore, forage lands and shrublands have adverse effects on the mitigation of deep soil desiccation with decreasing rainfall. This study recommended farmland in the terrace and abandoned land in the slope for soil and water conservation and sustainable ecological restoration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Amino sugars are chosen as biomarkers of microbial necromass in aggregate soils. • NW conversion to FL or CL increases the contribution of aggregate MNC to SOC. • FNC are the main contributor to microbial necromass in estuarine soils. • Enhanced perturbation induces the enrichment of BNC to smaller-size aggregates. • pH and SMC affect the aggregate-associated MNC accumulation by mediating the MBC. Microbial necromass carbon (MNC), as an important component of the soil organic carbon (SOC) pool in natural environments, has increasingly gained significant attention in recent years. However, the redistribution pattern of microbial necromass in aggregate fractions of estuarine soils induced by human activity still remain unclear. In this study, we assessed the effect of land use conversion on the redistribution and accumulation patterns of aggregate-associated MNC in estuarine wetland soils on the Pearl River estuary of China. Typical soil samples in 0–30 cm profiles under different land uses [Natural Wetland (NW), Farmland (FL), and Construction Land (CL)] were analyzed. The results showed that the NW conversion to FL and then CL contributed to the continuous losses of SOC, however, the aggregate-associated MNC content was higher in FL and lower in CL compared to NW. The MNC contribution to total SOC in aggregate fractions gradually increased from NW (16.41 % − 23.62 %) to CL (23.87 % − 30.98 %) and then FL (34.62 % − 38.83 %) in profiles. Fungal necromass C was the primary contributor to the total MNC in each aggregate fraction. In NW, the MNC was mainly present in large aggregate size, however, the MNC was gradually enriched into smaller size aggregates, especially for the bacterial necromass C, after the conversion from NW to FL or CL. Microbial biomass carbon had a direct and positive effect on the MNC in soil aggregates under different land uses, except for in silt + clay fraction from NW. Moreover, pH and soil moisture content were two key variables affecting the MNC content and accumulation by mediating the microbial biomass of different land uses, while the dominate factors controlling the MNC accumulation varied with size fractions in aggregates. Our results emphasize the influence of land use conversion on the soil aggregate-associated MNC accumulation in estuarine wetland. [ABSTRACT FROM AUTHOR]

• Soil physical properties were strongly related to land use, slope aspect, slope position and their interactions. • 19 year old locust was the most effective at improving the BD and Ks. • Better soil physical properties were obtained on the north slope and down slope. • Soil physical properties displayed different changes with locust restoration year. • Key factor affecting forest growth and soil quality improvement varied with forest ages. Soil particle size distribution (PSD), bulk density (BD), saturated hydraulic conductivity (Ks), soil water content (SWC) and generalized soil structure index (GSSI) are key physical properties for vegetation growth and are easily affected by natural and anthropogenic factors. However, how these soil physical properties respond to land use, slope aspect, slope position, and their interactions are less clearly understood. Here, an experiment with three land uses (cropland, grassland, and black locust [ Robinia pseudoacacia L.] forests after 4, 9, 15, and 19 years of restoration), two slope aspects (south and north slope) and two slope positions (up and down slope) were conducted in the hilly loess region of China. The results showed the following: (1) The variation in different physical properties were driven by different factors of land use, slope aspect, slope position and their interactions. (2) The 9, 15 and 19 year old locust forests significantly decreased the BD by 6.75 %–19.32 % and increased the Ks by 69.96 %–195.97 % compared with grassland, while the cropland had higher SWC and GSSI values than the grassland and locust forests. (3) Soil physical properties were higher on the north slope than on the south slope and were larger on the down slope than on the up slope. (4) The BD, Ks, SWC, and GSSI of locust forests displayed different changes with the restoration year. (5) The key factor affecting forest growth and soil quality improvement varied with forest ages. Overall, 19 year old locust was the most effective at improving the BD and Ks. Furthermore, slope aspect, slope position and restoration time should be considered when evaluating the response of physical properties to land uses. [ABSTRACT FROM AUTHOR]

• A subsurface storm flow-based hydrological model was created for mountainous regions. • A method determining rainfall threshold for extreme flood was proposed. • A relationship between forest cover and the rainfall threshold was established. • The rainfall threshold significantly increased when forest coverage exceeded 70%. Floods frequently occur in mountainous regions and threaten lives and property worldwide. Forest cover usually plays an important role in regulating and preventing floods. However, the rainfall thresholds for forest cover to effectively regulate extreme flood are still unclear. In this study, we developed the topography-based subsurface storm flow hydrological (Top-SSF) model, which generally exhibited precise simulation performances in five typical mountainous catchments in southwest China. Then, the Top-SSF model was combined with a frequency analysis method to set different forest cover scenarios, investigating the relationship between rainfall threshold and forest cover in mountainous catchments. The results showed that under the control of soil saturated hydraulic conductivity (Ks) and maximum soil water storage capacity (Szm), the rainfall threshold of an extreme flood (the 100-year return period) increased significantly, especially when forest cover was larger than 70% of a catchment. Under the same forest cover, high initial soil water content ( Sw i) weakened the mitigating effect of forest cover on the extreme flood. In addition, a non-linear regression relationship between forest cover and rainfall threshold of a catchment was developed considering the impacts of Ks , Sw i and annual mean precipitation ( P ¯ ) of the catchment. The significant impact of forest cover change on extreme floods was not only due to changing the amount of forest cover but also the soil properties. These results contribute to the understanding of the impact of forest cover changes on extreme floods and may provide valuable insights for flood defence in mountainous catchments. [ABSTRACT FROM AUTHOR]

• We addressed soil carbon fluxes in saline-alkaline grasslands. • Light grazing showed a negative effect on SR h. • Seasonal fluctuation of grazing effects resulted in unaltered seasonal mean SR. • Annual precipitation regulated the interannual variation of soil C emissions. • Soil environment explained SR more than plants and soil microorganisms. Grazing is a prevalent management strategy in grassland ecosystems that has profound effects on plants and soil microorganisms, consequently altering soil carbon (C) fluxes. However, the difference responses and regulatory mechanisms of soil autotrophic respiration (SR a) and heterotrophic respiration (SR h) to different grazing intensities remain unclear, especially in saline-alkaline grasslands. A six–year (2017–2022) field experiment involving four grazing intensities (no grazing, light grazing, moderate grazing, and heavy grazing) was conducted in a saline-alkaline grassland located in the agro-pastoral ecotone of northern China. Soil total respiration (SR tot) and its components (SR a and SR h), and the related biotic and abiotic factors (plants, soil microorganisms, and soil environment) were measured. The results showed that light grazing significantly decreased the mean SR h by 17.7% across six measuring years. The effects size of grazing on soil respiration fluctuated consistently with soil water content during the growing seasons (May–September), resulting in a neutral effect of grazing on the seasonal mean SR a. The cumulative soil C emissions of the current year varied with the seasonal precipitation in the previous year, whereas the changes in cumulative soil C emissions induced by grazing showed the same trends as annual precipitation. In addition, the key control factors for SR h and SR a differed and varied with grazing intensity and the soil environment played a critical role in regulating soil C fluxes. In conclusion, light grazing reduces soil microbial-driven C emissions and the soil environment and precipitation co-regulate the response of soil C fluxes to different grazing intensities in saline-alkaline grasslands. [ABSTRACT FROM AUTHOR]

• Soil moisture content varied with soil depth, upslope distance, vegetation type, and time. • Soil organic carbon and moisture were lowest in Robinia pseudoacacia plantations. • Grassland showed lower soil moisture loss and greater organic carbon sequestration. • On the Loess Plateau, afforestation within grassland may enhance ecosystem services. Large-scale afforestation is considered controversial as an ecosystem renewal strategy for the Loess Plateau of China, since it may increase soil organic carbon (SOC) but may also exacerbate water shortages. In our study, we aimed to clarify how afforestation and slope affect soil moisture content (SMC) and SOC and their interaction particularly for deep hillslope profiles on long hillslopes, in terms of the trade-off between soil moisture and organic carbon. This study investigated SMC and SOC density (SOCD) from 0 to 400 cm hillslope depth profiles at 20 m intervals uphill to 100 m in the May and October (the beginning and end of the growing period, respectively) from 2015 to 2017. The three sampling sites were located in Robinia pseudoacacia plantation, natural forest, and natural grassland as the control. Soil moisture deficit and SOC sequestration of plantation were compared to those of grassland, and the trade-off between SMC and SOCD was evaluated. The results showed that SMC and SOCD were the lowest in the Robinia pseudoacacia plantation, indicating that the plantation exhibited a greater soil moisture deficit and SOC loss than the grassland. In the plantation and natural forestland, the subsoil (100–400 cm) exhibited greater soil moisture deficit and SOC loss than the soil (0–100 cm). SOCD increased while SMC decreased with upslope distance for all hillslope layers in both plantation and natural forestland. The downslope sites exhibited more severe soil moisture deficit, and greater SOC loss than the upslope sites. Natural grassland exhibited low water depletion and high SOC sequestration. Further, the downslope plantation sites exhibited the lowest root mean square deviation for the relationship between SMC and SOCD. Based on these findings, a vegetation restoration strategy involving afforestation of downslope patches within a contiguous grassland matrix may achieve high-level maintenance of ecosystem services. These findings provide a theoretical basis for vegetation restoration on the Loess Plateau. [ABSTRACT FROM AUTHOR]

[Display omitted] • Afforestation has desiccated the soil in arid areas. • Soil moisture was significantly affected by plantation age. • A conceptual synthesis is proposed based on soil dry layer of Vegetation carrying capacity. In recent years, China has achieved remarkable results in curbing desertification through afforestation. However, the dry soil layer resulting from the long-term water consumption of overloaded perennial plants seriously threatens the sustainability of afforestation, and quantifying the maximum vegetation carrying capacity under certain soil moisture conditions is crucial to the sustainability of afforestation in arid areas. Therefore, we aimed to simulate soil water in Haloxylon ammodendron plantations at different growth stages using the simultaneous heat and water transfer (SHAW) model to determine the vegetation carrying capacity threshold. Field-measured soil and vegetation data for 2021 were used to calibrate the SHAW model. Good consistency in soil water content (SWC) was observed between measurements and simulations in the calibration and validation phases of the model, with considerable linear correlation and low prediction error values. Therefore, the soil water dynamics of H. ammodendron plantations in the study area could be accurately predicted using the SHAW model. The simulation results show that, with increasing forest age, the SWC at 0–400 cm gradually decreases and a dry soil layer starts to form when the forest age reaches 11 years. The dry layer thickness reaches 120 cm by 22 years, thus the optimal growth age of artificial H. ammodendron plantations in the study area should not exceed 22 years, and the maximum biomass soil water carrying capacity of vegetation is 1,650 kg/hm2. A vegetation carrying capacity threshold can be determined in this study for the sustainable management of future afforestation activities. [ABSTRACT FROM AUTHOR]

• Freezing (25 d) took longer than thawing (19 d) from 0 to 100 cm profile. • High moisture prewinter raised the saturated water layer throughout thawing. • High moisture prewinter prolonged the freeze–thaw period and reduced the freeze–thaw cycles. • The depth of zero temperature amplitude was deeper under low moisture prewinter. • Initial water affects freeze–thaw by governing profile water vertical migration. The freeze–thaw characteristics are of great hydrological significance in seasonally frozen agricultural soil and may vary for different initial moisture conditions because of variability in land use, topography, tillage and climate change. However, the initial soil moisture regimes before winter freezing that control the dynamics of profile freeze–thaw cycles remain unclear. This study explored the soil profile freeze–thaw dynamics under different prewinter moisture regimes located in a seasonally frozen Mollisol in China. The high, medium and low soil moisture regimes were simulated by infiltrating different water into the soil profiles before winter freezing. We investigated the soil temperature and water content at five depths from October 2017 to May 2018. Our results revealed that the variation in soil water storage occurred after infiltration before winter freezing and lasted throughout the thawing period. The highest soil water occurred above a depth of 20 cm in the early days of the thawing period under all treatments. During the thawing period, the soil water content was highest above depths of 0–20 cm, 20–40 cm and 40–60 cm under high, medium and low infiltration, respectively. Freezing took longer than thawing from 0 cm to 100 cm soil depths. Freezing started later and thawing ended later under higher soil moisture conditions prewinter. The top 10 cm of soil experienced intense soil temperature rise and fall cycles with an average of 20 cycles during the thawing, and higher moisture conditions reduced the freeze–thaw cycles. The depth of zero amplitude in soil temperature under high, medium and low soil water was estimated as approximately 140, 134 and 160 cm, respectively. Our findings suggest that more attention should be given to the top layers and sidewall layers under the lower prewinter soil moisture conditions. This study provides a very detailed understanding of soil temperature and moisture dynamics over a full winter freeze–thaw cycle and would makes a worthy contribution in seasonally frozen areas where few such comprehensive datasets exist. [ABSTRACT FROM AUTHOR]

• Establishment of plantation forest reduced the surface soil infiltrability but enhanced the water retention capacity (20–30 cm). • Low initial water content was conducive to increase soil water content after infiltration. • Visualization of gravels and roots spatial distribution at the soil plot scale. • Gravels with better connectivity were more conducive to water infiltration. • Preferential flow was the main infiltration type in reforested areas. Plantation forests (PF) and natural secondary forests (NSF) are the primary reforestation approaches. The establishment of PF can affect forest hydrological processes by changing soil structure. To date, few studies have focused on these changes and the effects on hydrological processes for the paleo-periglacial landform. To reveal reforestation approaches effects on water infiltration, including soil water infiltration capacity, retention capacity, and waterflow path pattern, we conducted field dye-tracer investigations with rainfall and laboratory infiltration experiments for the paleo-periglacial landform of eastern Liaoning mountains, China. The results showed that (1) Soil physical properties (including total porosity (TP), capillary porosity (CP), non-capillary porosity (NCP), initial soil water content (IWC), field water capacity (FWC)) and root abundance (RA) decreased with soil depth in both PF and NSF, while the soil bulk density (BD) and distribution of gravel content showed opposite changes. (2) Establishment of PF reduced the infiltration capacity and water retention capacity in the 0–20 cm layer, but enhanced the water retention capacity in 20–30 cm layer. Low IWC was conducive to increase soil water content (SWC) after infiltration. (3) Infiltration capacity parameters (including saturated hydraulic conductivity (Ks), SWC , difference between SWC and IWC (SWC–IWC), dye coverage ratio (DC)) were significantly correlated with BD , TP , CP , NCP , FWC , and fine roots RA (P < 0.05). Better connectivity gravels were more conducive to water infiltration. (4) Preferential flow was the main infiltration type, but with different waterflow paths pattern, with the 'funnel', 'finger' shape for PF, NSF, respectively. Increasing infiltration could increase flow path connectivity. Our findings show that soil physical properties, roots, and gravel occurrence affected soil infiltration, and different reforestation approaches had varying impacts on soil infiltration, water redistribution, transportation, and storage of surface and groundwater, improving the understanding of ecohydrological processes and effects of water resources management in forest ecosystems of paleo-periglacial landform. [ABSTRACT FROM AUTHOR]

• Soil water movement was predominantly via piston flow based on the soil tritium profile. • Line-conditioned excess (lc-excess) in deep soils were consistently negative. • Large soil water deficit under orchards could be related with huge water consumption via evapotranspiration. Exploring the groundwater recharge mechanisms in regions with thick unsaturated zones can enhance our understanding of intricate groundwater processes, especially in intensive agricultural regions such as the North China Plain (NCP). For example, to better answer the question of how deep soil water can be recharged, it is of utmost importance to illustrate the recharge mechanisms of groundwater under different land use types in the NCP. This study collected soil samples from four boreholes up to 18 m deep covering farmland and orchards with different stand ages and measured soil water content (SWC), stable and radioactive isotopes (δ18O, δ2H and 3H) of both soil water and groundwater. Results indicated that the movement of water through the deep vadose zone of soils was primarily piston flow based on a soil tritium profile. The infiltration rate was estimated to be 32.2 mm yr−1 based on the tritium peak method. The variations of soil water δ18O and line control excess (lc-excess) indicated that the orchards had lower evaporation effects and a higher precipitation offset than those in farmland soils. Furthermore, the deep soil water was replenished by intensive precipitation events (from July to September). The great soil water deficit and decreased deep drainage under pear orchards is usually closely related to huge water consumption by evapotranspiration (ET) via root uptake, which explains the increase of ET in pear orchards with increasing stand age. These findings have provided substantial insights into groundwater resource management in similar regions with limited water resources and recharge modeling for regions covered with thick unsaturated zones. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil bacterial richness and communities differed with altitude and vegetation type. • Soil bacterial richness was mainly controlled by MAAT and MAP. • Soil C/P and MAP were the most important regulators of soil bacterial community. • Soil pH significantly affected bacterial diversity and community but to a less extent. • Soil SMC and C-limitation of microbial metabolism are important regulators of soil SOC. Peatlands are crucial carbon (C) sinks, and the combined activities of soil bacteria and soil abiotic properties play an essential role in regulating the C cycle. However, mountain peatlands are particularly vulnerable to global change, which could lead to a change from C sink to source. Understanding how variations in soil bacterial communities and diversity along an altitude gradient affect C storage through changes in enzyme stoichiometry ratios is essential. To address this issue, this study collected soil samples from six peatlands at different altitudes in the Changbai Mountains, China, which were dominated by either sedge or shrub/ Sphagnum species. The study examined a range of soil physical and chemical properties, quantified bacterial community diversity and structure, and assessed enzyme stoichiometry. The results indicated that bacterial communities varied with altitude and vegetation, with bacterial α-diversity (richness) being higher at lower altitudes and in sedge-dominated peatlands. Mean annual air temperature (MAAT) and mean annual precipitation (MAP) were the primary drivers of bacterial diversity, and soil bacterial community composition was significantly influenced by soil carbon/phosphorus (C/P) ratio and MAP. On the other hand, soil pH had only minor effected in mountain peatlands. Path analysis emphasized the greater importance of soil moisture and microbial C limitations than bacterial richness and community on soil organic carbon (SOC) in mountain peatlands. The study also suggested that increasing bacterial richness and relative abundances of rare phyla could increase soil C concentration in peatlands. Overall, this study provided valuable insights into the regulation of C cycling in mountain peatlands and could help mitigate global climate change. [ABSTRACT FROM AUTHOR]

• Warming and precipitation reduction significantly affect Rs in sandy grasslands. • ST plays a dominant role in Rs during the early and whole growing seasons. • SM plays a dominant role in Rs during the middle and late growing seasons. • Rs is co-regulated by hydrothermal factors, soil properties and vegetation characteristics. • ST and SM remain the main factors determining Rs in sandy grassland. Soil respiration (Rs) is one of the largest carbon fluxes from terrestrial ecosystems to the atmosphere, and there are still a great deal of uncertainties in the estimation of soil carbon emissions from terrestrial ecosystems. Grassland ecosystems are fragile and sensitive to climate change, so it is crucial to reveal the effects of temperature and precipitation changes on Rs in sandy grasslands. Here, we examined the effects of experimental warming and precipitation reduction on Rs in the sandy grassland of Horqin and the relationships between different environmental factors and Rs. It was found that: (1) Soil temperature (ST) and soil moisture (SM) showed consistent seasonal variations with Rs during the growing season; (2) Warming increased Rs significantly in the middle of the growing season and throughout the growing season, and had no significant effect on Rs at the beginning and late of the growing season. Precipitation reduction reduced Rs significantly in the early and middle of the growing season and throughout the growing season, but had no significant effect on Rs at the late of the growing season. The interaction of warming and precipitation reduction only significantly reduced Rs in the middle and late of the growing season; (3) ST played a dominant role in Rs in the early growing season and throughout the growing season, and SM played a dominant role in Rs in the middle and late of the growing season; (4) Rs was significantly and positively correlated with ST and SM in the growing season; (5) Rs was regulated by the combination of hydrothermal factors, soil properties, and vegetation characteristics, of which hydrothermal factors are the main influencing factors in the growing season. Our results provide direct evidence to elucidate the effects of climate change on Rs in sandy grasslands. [ABSTRACT FROM AUTHOR]

• Agroforestry stand age affects soil water patterns significantly. • Over 20 years, stand age reduces soil water movement. • New and existing soil water interplay adds complexity in agroforestry. Understanding the relationship between agroforest age and soil water dynamics is crucial for effective land and water resources management. However, the complexities of these dynamics, such as soil water recharge and depletion, hamper in-depth understanding, particularly in water-scarce regions. In this study, we examined soil water recharge and depletion in relation to the stand age of apple trees, a widely planted and representative deep-rooted agroforest, over four years in a semi-arid region on China's Loess Plateau (CLP). We collected soil cores to >20 m depth from four apple orchards (referred to as 'agroforests') with variable stand ages (established in 2008, 2005, 1998, and 1994). For comparison, we selected adjacent cropland as land use prior to agroforestry practices ('control'). We measured soil water content and tritium distributions to model soil water dynamics and estimate water ages across different soil profiles. Our results show that recharge amounts (and depths) in shallow soils were 298.4 mm (7 m), 303.4 mm (6.6 m), 300.6 mm (5.4 m), and 483.1 mm (7.6 m), whereas deep soils had net depletions of 111.1 mm, 391.9 mm, 192.8 mm, and 108.9 mm for AP2008, AP2005, AP1998, and AP1994, respectively. The tritium peak depths, which indicate the 1963 bomb peak depth, significantly differed between agroforested and non-agroforested plots. In particular, agroforestation reduced the seepage velocity of soil water over 20 years. Furthermore, our tritium tracer water age model suggests that the age of transpired deep soil water exceeded 200 years in the oldest orchard. These findings highlight a complex interaction between newly infiltrated water and existing water, possibly due to variations in soil pore size distributions. The results of this study offer valuable insights into the ecohydrological impacts of agroforestation on the CLP and in similar climatic regions. [ABSTRACT FROM AUTHOR]

• SWCMs reduced the flood magnitudes and sensitivities to rainstorm events. • Control effects of SWCMs on flood decrease with rainstorm intensity. • Small watersheds are more likely to cause large flood peaks in Loess Plateau. • Bare soil of agricultural terraces must be protected in earth-rocky mountainous areas. Flash floods resulting from extreme rainstorms seriously threaten regional socioeconomic development. However, few studies have explored the general impacts of soil and water conservation measures (SWCMs) on flood peaks during extreme rainstorms through multiple field investigations. On the basis of field surveys of three rainstorm events in Shaanxi, Shandong, and Henan provinces, the effects of vegetation and agricultural terraces on flood peaks were investigated in 75 small watersheds in northern China. Compared with watersheds dominated by sloping cropland, the flood peak modulus of watersheds dominated by forest land, grass land, and agricultural terraces decreased by 54.75%, 47.80%, and 53.65%, respectively; the peak shaving effects (PSEs) of SWCMs were stronger during minor floods. Soil and water conservation measures reduced the flood magnitudes of small watersheds and their sensitivities to rainstorm events; the PSEs were positively correlated with the area of SWCMs. In earth-rocky mountainous areas, the PSEs of forest land were stronger than those of grassland and agricultural terraces, while in the loess hilly-gully areas, the PSEs of agricultural terraces were stronger than those of other SWCMs. In loess hilly-gully areas, the flash floods demonstrated a phenomenon of small rainfall amounts but substantial flood peaks. Besides the reasonable installation of SWCMs on slopes, appropriate channel measures (e.g., check dams) are warranted to cope with extreme rainstorm events. In northern earth-rocky mountainous areas, intercropping management should be promoted to cover bare soil on orchard agricultural terraces. Our results provide a theoretical basis for combating extreme rainstorm disasters. [ABSTRACT FROM AUTHOR]

Abstract Characterizing soil moisture variation has critical implications for various ecosystem processes and the hydrological cycle. In this study, we identified the hot moments (times with high temporal variation rates) and hot spots (areas with high temporal variation rates) of the soil moisture variation and investigated their controlling factors on a tea garden hillslope in Taihu Lake Basin, China. Daily soil moisture data were calculated for 39 sites, and then, daily soil moisture maps were generated from March 1, 2014 to February 28, 2015. The soil moisture temporal variation rates (VR) at different locations and during different time periods were calculated based on these maps. We found that because soil water content at the subsurface was more spatially varied than that at the surface on this hillslope, spatial heterogeneity of VR was also greater at 0.3-m depth than that at 0.1-m depth. Elevation, sand content and rock fragment content were positively correlated (p < 0.05) with this spatial heterogeneity, while slope and clay content were negatively correlated (p < 0.05) with it. June and July 2014 were the hot moments with high VR at both depths of 0.1- and 0.3-m, while December 2014 was the cold moment with the lowest VR at both depths on this study hillslope. Meteorological factors (precipitation and temperature) explained 59.9% and 56.9% of the total variance in the time series of spatial mean VR at the depths of 0.1- and 0.3-m, respectively. Stronger variations in spatial mean VR were found during representative medium and large rainfall events than during representative small rainfall events. In addition, the response of spatial mean VR to rainfall at 0.3-m depth was delayed compared to that at 0.1-m depth. The findings and methodologies of this study can be useful in determining the hot spots and hot moments of soil moisture variations, which could be potentially useful for investigating various hydrological, ecological, environmental, and agronomic processes. Highlights • The hot moments and hot spots of the soil moisture variation are identified. • Soil moisture temporal variation rates at 0.3-m depth were greater than those at 0.1-m depth. • June and July were the hot months with high soil moisture temporal variation rates. • December was the cold month with the lowest soil moisture temporal variation rates. • The elevation, slope, soil texture and rock fragments jointly controlled the soil moisture temporal variation rates. [ABSTRACT FROM AUTHOR]

Abstract Soil water storage (SWS) is a critical water resource for vegetation growth in the Loess Plateau. Changes in SWS during the growing season can reflect soil water depletion or recharge conditions in different hydrological years. This study investigated the soil water in three hillslopes covered with artificial forest, natural forest and natural grass in May and October of 2015–2017. Both path analysis and stepwise multiple linear regression were used to determine the direct and indirect effects of most important variables and develop a model for predicting changes in SWS. The results showed that compared with natural forestland and grassland, artificial forestland had low soil water, but deep SWS maintained a balance of inputs and outputs. In all soil layers, during the growing season, total precipitation (X 4) was the most important variable affecting changes in SWS. The changes in SWS in surface soil layers were affected by more environmental factors than in deeper soil layers. The natural grassland (X 3) and slope position (X 12) have different degree of direct and indirect effects by means of antecedent soil water content (X 5) , even though their correlations were not significant. In addition, changes in SWS at the 0–100 cm, 100–200 cm and 0–400 cm soil layers were adequately predicted using the multiple regression equation, in which R2 reached values from 73.4–93.0%. The model simulating the changes in SWS during the growing season can improve understanding on whether rainfall infiltration can replenish soil water depletion. Highlights • Deep soil water storage (SWS) in artificial forestland can maintain a balance. • Changes in SWS in upper soil layers were affected by more major factors. • The indirect effects of some controlling factors on changes in SWS were not ignored. • Changes in SWS in upper layers were adequately estimated using the prediction model. [ABSTRACT FROM AUTHOR]

Abstract Grassland recovery from degradation is increasingly occurring worldwide. Diverse managements have been considered as effective ways to restore degraded grassland, but it remains unclear how semi-arid grasslands respond to long-term grazing exclusion and fenced mowing. Here, a study was conducted under open grazing, grazing exclusion and fenced mowing in a semi-arid grassland on the Loess Plateau. We measured plant species composition and diversity, plant production, surface litter and soil water and carbon content. Shifts in grassland management led to significant divergence in plant community composition. Long-term grazing exclusion (35 years) significantly increased plant biomass, surface litter, soil water and carbon storage, but suppressed plant diversity compared to open grazing. Conversely, fenced mowing significantly increased plant diversity accompanying with a weak effect on soil carbon. Moreover, mowing significantly reduced surface litter and soil moisture, which have strong implications for nutrient depletion and soil drying. Our results suggest that introducing disturbances are necessary to safeguard biodiversity, and continuous mowing (5 years) belongs to over exploitation of the long-term protected grassland. Therefore, it is essential to optimize management with dual objectives of biodiversity and soil carbon sequestration in the future. Highlights • Three representative management-related steppe conditions were evaluated. • Long-term grazing exclusion replenished SOC but decreased plant diversity. • Fenced mowing safeguarded plant diversity but induced soil drying. [ABSTRACT FROM AUTHOR]

• SWS variability persisted for at least 3 months in each land type. • Freeze-thawing and transpiration were the main factors affecting SWS in winter. • A quantitative index of water conservation capacity was proposed for each land type. • Shrubland had a greater potential of water conservation capacity than grassland. • Areas of bare land in arid regions require appropriate conservation. Time-series analysis of soil water storage (SWS) can provide important information on critical hydrological variability related to soil water recharge, retention, and vegetation water consumption, all of which are highly non-linear and non-stationary, making mining and analysis extremely challenging. In this study, Multivariate Empirical Mode Decomposition (MEMD) was used to separate and analyze time-series data on soil moisture, soil temperature, and meteorological factors in three different land types (bare land [BL], grassland [GL], and shrubland [SL]) in the Mu Us Desert, Shaanxi Province, China. Path analysis was then used to reveal the driving force of periodic variability in SWS after decomposition. Using daily SWS data, two new indicators, evapotranspiration capacity (K e) and rainfall interception capacity (K p), were also proposed in order to improve the accuracy of soil water conservation capacity calculation. The results revealed strong time-persistent memory of SWS in all land types, with hydrological periodic variability mainly reflected on a monthly scale (34–45 d). The greatest memory period was observed in SL followed by BL and GL. Subsequent path analysis suggested that dry-wet alternation (R2=0.32–0.48) driven by interactions between precipitation, solar radiation, and saturated vapor pressure were the main causes of SWS variability in the summer. While, freeze–thaw cycles (R2=0.73–0.86) driven by the soil temperature and meteorological factors were the main causes of SWS variability in winter. In the root zone (0–150 cm), the water conservation capacity of BL, GL, and SL was 139.24, 38.24, and 24.76 mm/y, respectively. In addition, the K e /K p values and MEMD residual component revealed that SL has greater potential for water conservation than GL. Overall, these findings suggest that in order to conserve local groundwater aquifers, areas of BL require appropriate protection in arid regions. The results of this study provide a basis for future analyses of soil moisture variability and water conservation in arid regions. [ABSTRACT FROM AUTHOR]

• Combined measures were used to regulate rainwater in Pisha Sandstone areas. • Infiltration holes promoted deep rainfall infiltration into the weathered bedrock. • Infiltration holes with mulching improved the weathered bedrock soil water storage. • Fish-scale pits with grass mulching and infiltration holes was the most effective. Effectively regulating slope runoff and infiltrating maximum rainwater are essential to reduce soil and water loss, and promote vegetation restoration in the Pisha Sandstone areas of China, which are semiarid areas with shallow buried bedrock. However, the effects of individual or combined rainwater regulation measures, such as infiltration holes, mulch, and fish-scale pits (a semicircle-shaped pit), on soil water infiltration and restoration in such regions have not yet been fully explored. In this study, the responses of soil water to rainfall in the 0–1.6 m soil layer was investigated through in situ monitoring during the two main rainy seasons under four rainwater regulation treatments in the Pisha Sandstone area of China covered in thin soil layer (0–0.3 m): fish-scale pits with grass mulching and infiltration holes (PGH), fish-scale pits with grass mulching (PG), fish-scale pits without mulching (P), and slope land (control, CK). The results have shown that because of the relatively low permeability (0.08–0.17 m d−1) of Pisha Sandstone, individual torrential rainfall events (63.2 mm) increased the soil water only in the 0–0.3 m layer after 3 days under the CK, P, and PG treatments. However, the PGH treatment simultaneously and significantly increased the soil water in the 0–0.3 m and 0.7–0.8 m layers. Compared with the CK treatment, rainwater replenishment depths under the P, PG, and PGH treatments increased from approximately 0.4 m to 0.9 m, 1.0 m, and 1.1 m, respectively, and the average soil water storage increased by 27 mm, 34 mm, and 50 mm, respectively, in the 0–1.6 m soil layer. Moreover, the PGH treatment enhanced rainwater storage in deep soil (0.6–0.9 m), which decreased the potential for water loss by evaporation. We concluded that the PGH treatment was effective in increasing soil water storage and reducing soil erosion in areas with shallow buried bedrock. [ABSTRACT FROM AUTHOR]

Intensive cropland soil erosion can be caused by disturbance activities. However, conservation measures have been reported to increase soil resistance and decrease erosion. Hydraulic flume experiments were conducted to measure the detachment rate of disturbed soil samples from a peanut field with five tillage practices. Hydraulic variables were adopted to estimate the soil detachment rate and to quantify the rill erodibility parameter. The disturbed soil detachment rates are substantially greater than those for comparable undisturbed soil experiments. The average disturbed soil detachment rates for the 5 different tillage treatments, from lowest to highest, are as follows: straw mulch (PC) < manure (PM) < peanut and orange intercropping (PO) < peanut and radish crop rotation (PR) < conventional downslope furrows (PF). The conservation measures (PC, PM and PO) have a limited effect on increasing the disturbed soil resistance under low flow energy conditions. Thus, the average rill erodibility is lower, and the critical shear stress is higher for the PC, PM and PO treatments than those of the PR and PF treatments. With a slope gradient steeper than 17.6%, there is no significant difference among the detachment rates of all treatments. A linear function of both flow rate and slope gradient can be used to estimate the disturbed soil detachment rate. Both stream power and flow shear stress are more effective than the unit stream power in predicting soil detachment rates. The stream power is the most effective predictor among the three hydraulic parameters studied. Instead of the power functions, the linear functions of the hydraulic parameters are suggested to quantify the disturbed soil detachment rates. [ABSTRACT FROM AUTHOR]

Soil respiration ( R s ), conventionally considered as net soil CO 2 flux, is an important link in the terrestrial carbon cycle. However, existing estimates of R s in drylands may be erroneous, because of the abiotic soil CO 2 flux. This may seriously hamper our understanding of the carbon cycle of desert ecosystems. In this study, we monitored CO 2 flux of natural and sterilized soils, and obtained the net and abiotic soil CO 2 flux in a desert ecosystem in Ningxia, China, and then computed R s by using these data. Daily R s was much larger than the net soil CO 2 flux both in the growing and non-growing season. Further analysis indicated that R s was controlled by soil temperature ( T s ) over the annual cycle, and an exponential model could provide a good prediction of R s . During the growing season, R s increased significantly with rising soil water content ( VWC ) ( P < 0.05). A bivariate ( T s and VWC ) exponential–power model had a better performance for predicting R s in the growing season than a T s -only model. However, during the non-growing season, this model failed to simulate R s . Our results suggest that R s is greatly underestimated, and the exponential model is more applicable for annual R s prediction. [ABSTRACT FROM AUTHOR]

Soil water plays a critical role in vegetation growth and restoration in semiarid regions, and has highly spatiotemporal variability. Gaining a comprehensive understanding of the soil water input and output processes is critical to the study of the hydrological cycle. To further unveil and quantify soil water dynamics, we embarked on a research program to quantify hydrological processes under three sites (i.e., shifting dune, shrub-dominated community, and herb-dominated community) with continuously monitored soil water content at 10-min intervals in the Mu Us Sandy Land between April and October 2012. The results indicated that soil water input and output processes were strongly affected by rainfall infiltration and surface characteristics. Rainfall affects the fluctuation of soil water content in deeper layers (60–80 cm) by altering rainfall amount and soil texture; vegetation affects the soil water input process by altering the canopy rainfall interception, hydraulic lift, and soil organic matter content and so on. The effects of rainfall on the soil water output process mainly contributed to direct leakage and evaporation. Plant root distribution was a vital factor affecting the soil water output process. In addition, a state of dynamic equilibrium existed between the absorption of soil water and non-rainfall replenishment of soil water content during the output process over a long period of time. With limited soil water input and relatively larger soil water uptake by deeper roots, the soil water varied up to ~ 80% under the herb-dominated community. Our results imply that the increment of the deeper layer (60–80 cm) would enhance shrub expansion in the Mu Us Sandy Land of China. [ABSTRACT FROM AUTHOR]

Composition and stability of soil organic matter (SOM) affect the sustenance and productivity of soil over the long-term. This issue is particularly important for karst regions in China where the water supply and fertilizer use are limiting factors. Here, we used four indicators to evaluate changes in the composition and stability of SOM quantitatively in five main land-use types in karst area, including primary forest [PF], 15-year secondary forest [SF], grazing secondary forest [GF], abandoned farmland [AF] and farmland [FL]. We collected soil samples at a depth of 0–20 cm to conduct the analyses. Four indicators were used: soil physical and chemical properties, active organic carbon (C), humus C composition, and SOM functional groups. Our results showed that the content of SOM, total nitrogen, and easily oxidized organic C at 0–20 cm soil depth differed among the five land-use types ( P < 0.05). For humic acid C concentration, the land-use types were ordered as: SF > PF > GF > FL > AF. Solid-state 13 C NMR spectra showed that the highest ratio of Alkyl C/O-alkyl C was in AF, while the lowest was in SF. Overall, the comprehensive quality of SOM in different land-use types was PF (setting 100%) > SF (83.1%) > GF (58%) > AF (30.9%) > FL (29.9%). For karst areas, we suggest that farmlands in sloping area should be converted back to forests, with only moderate grazing being permitted, whereas farmlands in the plains should implement grain-forage rotation and grain-soybean rotation to meet the needs of the growing population and economic development. In conclusion, our findings provide a scientific basis from which to delineate rational land-use types for different land (geographical and geological) formations. [ABSTRACT FROM AUTHOR]

• Enzymic latch and iron gate were compared to reveal regulators of C in Zoige soils. • Phenol oxidase and Fe2+ were not crucial regulators of C in soils of Zoige Plateau. • The effect of moisture on SOC was remarkably higher than phenol oxidase and Fe2+. • Moisture indirectly affected SOC via adjusting enzymes, phenolics, and Fe oxides. • Fe oxides significantly affected SOC in non-waterlogged but not in waterlogged soils. Due to the enormous amount of carbon (C) stored in peatlands, understanding the regulator of soil organic carbon (SOC) in peatlands is critical for global C cycling. Currently, "enzymic latch" and "iron gate" are the frequently debated mechanisms that propose phenol oxidase (PHO) and Fe2+ as important regulators driving SOC cycling in peatland. Therefore, this study compared "enzymic latch" and "iron gate" in the same peatland (Zoige Plateau, the largest peatland in China) to figure out the crucial regulator of SOC content via investigating the interrelationships among soil properties, C-related enzymes, phenolics, and iron (Fe) oxides. Moreover, waterlogged and non-waterlogged soils were chosen to take samples in both dry and wet season to understand the potential role of moisture in regulating SOC content. It was found that the contents of dissolved organic C, phenolics, SOC, Fe oxides, and β-glucosidase (BG) activities in waterlogged soils were higher than those in non-waterlogged soils. Compared to the dry season, soils in the wet season had higher phenolics, SOC, and Fe oxides contents. Also, this study observed an insignificant relationship between PHO and SOC (p > 0.05) and the small amounts of Fe2+ to total Fe (<2‰) in soils. Meanwhile, the highest effect of moisture (0.89) and negligible effect of PHO (0.04) and Fe2+ (-0.08) on SOC based on pathway analysis suggested that moisture might be the crucial regulator of SOC. Furthermore, pathway analysis implied that moisture could indirectly affect SOC by adjusting BG (p < 0.05) and soluble phenolics (p < 0.05). This study provided valuable information for understanding the importance of moisture in driving C cycling and helping against soil C loss by moisture management in Zoige Plateau. [ABSTRACT FROM AUTHOR]

[Display omitted] • Significant differences in freeze–thaw processes between farmland and shelterbelt. • The migration and increment of soil water content in farmland were greater than in shelterbelt. • Land use patterns and initial soil water content had a greater impact on the occurrence of freeze–thaw processes than soil texture. • Soil texture was closely related to the amount of water migration during freeze–thaw. Seasonal freeze-thawing can affect the movement and distribution of soil moisture and thus impact the management of agroforestry. In this study, we analyzed the differences in the freeze-thawing of farmland and its shelterbelt by monitoring the dynamics of soil temperature (ST) and soil water content (All soil water content involved in this study is volumetric water content, SWC) at a depth of 0–100 cm in arid and semi-arid regions of northern China. The results showed significant differences in the freeze–thaw process between farmland and shelterbelt. Freeze-thawing in the upper soil layer (0–60 cm) of farmland and shelterbelt was significantly affected by air temperature (AT). Still, the shelterbelt was more resistant to freezing than farmland and maintained a higher soil temperature at all depths. The fluctuations of soil temperature and soil water content were also lower in shelterbelt than in farmland. In addition, farmland was frozen first but thawed later than the shelterbelt, with more freeze–thaw cycles. The migration and increment of soil water content were more significant in farmland than in shelterbelt at each soil depth during freeze–thaw. Land use patterns and initial soil water content had a greater impact on the timing of freeze–thaw onset than soil texture, but the latter was associated with soil water content migration. Our results improved the understanding of seasonal freeze–thaw processes and their effects on agroforestry. They can be used to develop appropriate management strategies for agriculture and forestry. [ABSTRACT FROM AUTHOR]

• Farmland shelterbelt systems (FSSs) can improve ecosystem functions over controls. • Environmental factors exhibit spatiotemporal heterogeneities in different FSSs. • Different patterns of FSSs had beneficial water retention and nutrient supply functions. • There were close relationships between environmental factors and ecosystem functions in FSSs. • Results provide a theoretical basis for ecological restoration in ecofragile regions. The farmland shelterbelt system is considered an effective form of land management to improve the eco-environment and soil quality in fragile agricultural areas. Clarifying the effects of farmland shelterbelt patterns on ecosystem functions can guide ecological restoration in fragile ecosystems. Four typical farmland shelterbelt patterns (i.e., two-line pattern, four-line pattern, five-line pattern, and eight-line pattern) in desert oasis ecotones of Hetao irrigated area, northern China, were selected in this study. In these treatments, measurements of soil properties at a depth of 0–100 cm; vegetation attributes; microclimate; and soil water, carbon, nitrogen, and phosphorus storage were performed during three growing seasons in 2019–2021. The results demonstrated that the four-line pattern had higher soil organic content (0.339 g·kg−1), total nitrogen content (0.517 g·kg−1), and total phosphorus content (0.577 g·kg−1) than the other treatments, as well as the highest soil water (237.44 mm), carbon (544.93 g·m−2), nitrogen (953.72 g·m−2), and phosphorus storage (859.04 g·m−2) at the 0–100-cm soil layer. Moreover, dynamic variations in soil water and salt contents showed opposite trends during the growing season, i.e., they showed a gradual decrease and increase, respectively. Furthermore, principal component analysis, correlation matrix analyses, and network association analyses indicated close relationships among environmental factors, nutrient storage, and related ecosystem functions under different farmland shelterbelt patterns. The results of this investigation provide a useful theoretical basis for agricultural management and ecological restoration in ecofragile regions. [ABSTRACT FROM AUTHOR]

• The response of soil water content (θg) to vegetation restoration mode varied highly. • θg increased with soil depth and the distance from the ephemeral gully (EG) head. • θg was less on EG top with artificial plant than on EG top with natural plant. • Natural succession is recommended to control soil erosion and maintain soil water. Vegetation restoration in an ephemeral gully (EG) can alter the traits of soil, vegetation, and microtopography, and therefore likely influences soil water. Nevertheless, few results have been reported regarding the response of soil water regime to vegetation restoration modes in EGs in semiarid region. This research was designed to clarify the spatial variation in soil water in an EG with different restoration modes on the Loess Plateau of China. For the selected EG, the two banks of ephemeral gully were well restored by natural succession and artificial planting. Soil water content (θg) was quantified on the ephemeral gully floor (F), natural successional restored ephemeral gully top (NT), and artificial planted restored ephemeral gully top (AT) in both the vertical and longitudinal directions. A sloping farmland was selected as the control. The results revealed that θg increased significantly with soil depth (i.e., 0–1 m) and the distance from the ephemeral gully head (i.e., 0–60 m). In the vertical direction, the mean θg of the six test points of the ephemeral gully floor was 1.1 to 1.2 times greater than that of the control in each soil layer, while the mean θg of the six test points of NT and AT decreased by 12.3 % to 15.6 % and 29.2 % to 29.9 % compared to the control in each soil layer. Along the longitudinal direction, the θg (i.e., 0–1 m soil layer) abided by the pattern of F > NT > AT. The difference in θg between the three ephemeral gully units and their variations in the vertical and longitudinal directions were mainly driven by the variations in soil clay content, bulk density, organic matter content, plant root density, plant litter density, and the distance from the ephemeral gully head. The findings are useful to clarify the spatial variation in soil water and to select a reasonable vegetation restoration mode on hillslopes in semiarid regions. [ABSTRACT FROM AUTHOR]

• Shrub growth is limited by N but increase leaf C to resist harsh conditions. • Stoichiometric ratios of plants were not related to those of soils, but controlled by soil properties. • Soil water, bulk density and porosity drive the ecological stoichiometry. Studying the ecological stoichiometry of ecosystem would promote understanding about how plant adapt to environment changes. As a typical alpine region, the Qilian Mountain of northwest China is a good platform for this purpose, but the ecological stoichiometric of plants is largely unknown. This study selected five dominant shrub species to collect shrub leaves and soils to explored the carbon (C): nitrogen (N): and phosphorus (P) characteristics and controls of them. The mean content of C (549.39 g kg−1) in leaves of shrub plants was higher than that of global flora. N:P ratio of five shrubs leaves (7–10) were all lower than 14. The shrubs in the alpine regions resist harsh conditions by increasing leaf C content, and their growth is restricted by N. Compared with altitude and soil, shrub species have greater effects on soil stoichiometric characteristics. The Caragana tangutica shrub may be the best specie for ecological restoration. The stoichiometric ratios of shrub leaves are not related to those of soils, but controlled by soil properties, mainly including soil water content (34.2%), bulk density (32.5%) and total porosity (12.8%). This study interpreted the mechanism how shrub adapt to changing environment, and provide information for how effectively restore the ecological environment in the alpine regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • Urban soil pH of urban forests increased with an increasing level of urbanization (p < 0.001). • The impervious surface coverage (TISC) is the main influencing factor that has both direct (TISC-pH) and indirect effects (TISC-BD-SWC-EC-pH chain) on urban forest soil alkalization. • Urbanization possibly leads to soil alkalization which is contrary to natural ecosystems. Soil pH in natural ecosystems is experiencing outstanding changes because of acid deposition, especially in the background of global climate change, which significantly alters the ecological material cycle and affects ecosystem function. However, in urban ecosystems, the direction and pattern of forest soil pH variation affected by urbanization are still unclear. In this study, we obtained the level of urbanization by remote sensing and combined it with urban forest soil properties obtained from field sampling to ascertain the effects of urbanization on the soil in Changchun city, Northeast China. Our results showed that the urban soil pH of urban forests was significantly higher than that in suburban (+3%) and outside-city forests (+33 %, p < 0.001) and that it increased with an increasing level of urbanization (p < 0.001). The other soil physical–chemical properties of urban forests in urban areas, such as soil electrical conductivity and EC (+41 %, p < 0.001; +172 %, p < 0.001) and soil water content and SWC (-9%; p > 0.05; −27 %, p < 0.001), were also significantly different from those in suburban and outside-city forests, but there were no evident changes in soil bulk density. Urbanization has caused topsoil soil water deficits and serious soil alkalization. The expansion of total impervious surface coverage (TISC) is the main influencing factor that has both direct (TISC-pH) and indirect effects (TISC-BD-SWC-EC-pH chain) on urban forest soil alkalization. Our findings highlight that urbanization possibly reverses the urban forest soil acidification risk and that its significance should be considered in global biogeochemical cycling. [ABSTRACT FROM AUTHOR]

• The shear strength of soil-root system was measured by in-situ shear tests. • Shear strength of soil-root system changed significantly with land use type. • Shear strength was significantly affected by soil properties and root traits. • RSAD was the best parameter quantifying the effect of root trait on shear strength. Shear strength of soil-root system (SRSS) is one of the most useful dynamic properties for evaluating soil erodibility and structural stability. The adjustment of land use may strongly affect SRSS by altering soil properties and plant root system. Few studies have been conducted to investigate the effect of land use on SRSS in semi-arid region. This study was performed to quantify the variation in SRSS with five typical land use types (cropland, orchard, grassland, shrub land and woodland) and identify the related dominant contributing factors on the Loess Plateau where land use has changed greatly in the past several decades. In-situ shear tests with large shear box (25 × 25 × 10 cm) were conducted to measure shear stress-displacement curves. The strain energy calibrated to 15 % soil water content (SE c), peak shear stress (PSS) and the displacement of peak shear stress (DPS) calculated from the curves were used to reflect SRSS. The results showed that woodland had the maximum SE c (124.4 J m−2) and PSS (1048.6 kPa), whereas cropland had the minimum SE c (65.6 J m−2) and DPS (7.2 mm). Woodland, especially coniferous species and its mixed forest, might be the most suitable land use type for vegetation restoration on the Loess Plateau to enhance soil erodibility or structural stability. The variation in SRSS with land use was closely related to the changes in soil properties and root traits. PSS increased with penetration resistance, while it decreased with soil water content. DPS was positive correlated to root biomass and morphological traits. SE c was mainly affected by the direct and indirect effects of root surface area density, penetration resistance, soil organic matter content and aggregate stability. The results are helpful for understanding the mechanical mechanism of vegetation restored soils to mitigate erosion and optimizing land use type in semi-arid region. [ABSTRACT FROM AUTHOR]

• Prediction of deep soil water content (SWC, 0–5 m) based on remote sensing and in-situ data. • The introduction of in situ factors significantly improved the accuracy of SWC PTFs. • The artificial neural network developed PTF reached the best accuracy of SWC prediction. Accurate and timely evaluation of soil water content (SWC) in water-limited arid and semiarid regions will provide an essential reference for scientifically based water management strategies and vegetation restoration practices. Theoretical and empirical models based on remote sensing data have been successfully applied to predict large-scale SWC. However, most existing models are limited to the surface soil layer, while the prediction of SWC in the deep soil layer (1–5 m) has been overlooked because of the shortage of long-term and large-scale filed-observed data. In this study, a south-north transect (ca. 860 km) was selected across the Chinese Loess Plateau (CLP). Based on both long-term remote sensing and in-situ data (2013–2016), pedo-transfer functions (PTFs) for the SWC in the 0–5 m profile were developed using multiple regression, random forest, and artificial neural network. The results showed that evapotranspiration, potential evapotranspiration, soil surface temperature, total shortwave broadband albedo, and normalized difference vegetation index were important remote sensing parameters, whereas soil texture and bulk density were important in-situ parameters for SWC PTFs development. Among the three PTF development methods, machine learning (i.e. random forest and artificial neural network) obtained a higher accuracy than multiple regression. For different combinations of input parameters, the introduction of in-situ factors significantly improved the accuracy of PTFs compared with PTFs based on remote sensing data only. The artificial neural network developed a PTF with only five input variables that predicted SWC with reasonable accuracy (root mean square error = 0.039, R2 = 0.697, mean absolute percentage = 24.8) and is thus useful for many applications on the Loess Plateau of China. In the future, more attention should be given to the role of in-situ parameters when developing PTFs for deep SWC prediction. [ABSTRACT FROM AUTHOR]

[Display omitted] • The denitrification rate was higher in the abandoned land than shrubland. • Denitrification were lower in summer compared to winter in all land use types. • Soil environmental factors controlled over denitrification under different land use types. • The denitrifying genes was correlated with denitrification in each season separately. Despite the importance of nitrogen (N) cycling in terrestrial ecosystems, the underlying mechanisms of changes in the soil denitrification rate and microbial function under land use change remain unclear. Here we conducted a field experiment to explore soil denitrification rate, abundance and diversity of denitrifying genes (nirS , nirK , and nosZ) across summer and winter for three land use types (abandoned land, shrubland, and woodland) in subtropical China. The highest denitrification rate was observed in abandoned land (0.31 ± 0.03 mg m-2h−1) while the lowest was in woodland (0.24 ± 0.01 mg m-2h−1); however, denitrification enzyme activity was higher in both abandoned land (6.68 ± 0.18 ng g-1h−1) and woodland (6.35 ± 0.46 ng g-1h−1) than in shrubland (5.45 ± 0.24 ng g-1h−1). Both the denitrification rate and denitrification enzyme activity in all land use types were lower in summer than in winter. Notably, the alpha diversities of the denitrifying genes did not change significantly among the land use types. But the beta diversity of nirS significantly differed among the land use types, that of nirK did not significantly vary with seasons, and that of nosZ changed significantly with both different land use types and seasons. Overall, our findings reveal that soil moisture, soil organic carbon, and NO 3 –-N concentration predominantly regulate denitrification under different land use types, whereas soil moisture and denitrifying genes primarily control variations in denitrification between seasons, thereby providing novel insights into predicting the effects of land use change on N cycling and belowground microbial function. [ABSTRACT FROM AUTHOR]

• Differences in splash erosion between 50 and 100 mm h−1 were attributed to surface seals. • Quantified the key factors affecting splash erosion before and after runoff occurrence. • Rainfall intensity and its energy exhibit higher contributions on splash erosion whether runoff occurs. • Identified the critical ratio of flow depth and raindrop diameter (h/D) at 100 mm h−1. Splash erosion has been acknowledged as a key process of water erosion, depending on multiple factors including rainfall and soil properties, antecedent soil moisture, and surface runoff. Previous studies mostly focused on the effect of simple factors on splash erosion, but the interactive effects of multiple factors on splash erosion are still obscure. Therefore, we investigated the characteristics of splash erosion under simulated rainfall and quantified the interactive effects of multiple factors on splash erosion using a modified splash pan for measuring directional splash erosion. The results showed that total splash erosion (summation of four directional splash erosion) and net splash erosion (downslope minus upslope splash erosion) ranged from 14.4 to 804.8 g m−2 and 2.0 to 186.5 g m−2, respectively, and both increased with rainfall intensity and rainfall kinetic energy. The splash erosion rates in the dry run were greater than those in the wet run at the earlier stage, whereas after runoff occurred, the splash erosion rates in the dry run were lower than those in the wet run. Furthermore, the calculated variance contributions indicated that before runoff occurrence, rainfall kinetic energy (KE) and antecedent soil moisture (θ a) were the dominant factors affecting splash erosion, accounting for 25.3 % and 15.0 % of variance contributions, respectively. After runoff occurrence, the main factors affecting splash erosion were rainfall intensity (RI), rainfall kinetic energy (KE) and their interactions, explaining 98.2 % of the total splash and 95.7 % of the net splash for all variance contributions. In addition, the effect of shallow flow on splash erosion was dependent on the ratio of flow depth and raindrop diameter (h/D). The thresholds of h/D seemingly ranged from 0.63 to 0.86 and 0.77 to 1.02 for the dry and wet runs under 100 mm h−1 rainfall intensity. This study provides a basis for understanding splash erosion mechanisms and improving process-based erosion models. [ABSTRACT FROM AUTHOR]

[Display omitted] • The development of planted vegetation significantly drives SOC mineralization of BSCs. • The percentage of mineralized C loss from BSCs decreased with increasing site age. • Temperature sensitivity of SOC mineralization increased with BSCs development. Revegetation is an effective measure to combat desertification worldwide, which parallelly facilitates the colonization and development of biological soil crusts (BSCs), and thereby affecting C cycles of BSCs in desert regions. However, knowledge about soil organic carbon (SOC) mineralization of BSCs and the involved mechanisms during long-term revegetation process in desert is rather limited. In this study, SOC mineralization rates of the mobile sand dune (MSD) and the BSCs in revegetated sites along chronosequence in the Tengger Desert were investigated, and the relationships between the SOC mineralization and the characteristics of vegetation and BSCs, soil properties and incubation temperature (T) and soil water content (SWC) were analyzed. The results showed that SOC mineralization rate of the BSCs and the corresponding subsoils was significantly greater than those of the MSD, and it increased considerably with increasing site age, regardless of the T, SWC, soil layer and sampling time (p < 0.001). The maximum instantaneous mineralization rates (MIR), cumulative CO 2 -C release (CCR) and the potentially mineralizable SOC (C 0) of BSCs and subsoils were 1.29–12.63, 3.67–23.16 and 3.78–23.41 times, and 0.16–2.26, 0.12–1.84 and 0.17–1.26 times greater than those of the MSD, respectively; while the proportion of C 0 to total SOC (C 0 /SOC) decreased by 31–88 % and 24–72 % in comparison with MSD, respectively. The mineralization rate increased with T and SWC, and the temperature sensitivity of BSCs increased with site age, indicating that the loss of SOC would be accelerated with the succession of BSCs upon the future global change. The variation magnitude of SOC mineralization was largely dependent on revegetation-induced changes in the properties of BSCs and the incubation T and SWC, and their interactions. The C:N, pH, and the activities of POD and PPO and DOC, and the coverage of moss-dominated crusts, SOC, C:N, the content of clay and silt and AYL activity were the main factors affecting SOC mineralization of BSCs and the subsoils, respectively. These results indicated that multiple factors that co-varied with the succession of BSCs led to variable SOC mineralization. Our findings suggested that planting xerophytic shrubs in desert drives the development and the SOC mineralization of BSCs, but decreased SOC loss due to mineralization, leading to SOC sequestration. [ABSTRACT FROM AUTHOR]

[Display omitted] • Soil inorganic N pools are higher in fixed dune than in dune grassland. • Soil NO 3 −-N concentration increase with decrease in precipitation. • Altered precipitation patterns do not change soil N transformation. • Soil N transformation increases with EC, NO 3 −-N and NH 4 +-N concentrations. The soil nitrogen (N) cycle and transformation rate are susceptible to precipitation regime changes in semiarid sandy ecosystems, and they play important roles in both the soil fertility and in plant interactions. However, the response mechanisms of soil N transformation to changing precipitation regimes in semiarid ecosystems are still unclear. Thus, we conducted a three-year rainfall manipulation experiment along a landscape evolution gradient from fixed dunes to dune grasslands in a semiarid sandy region of northern China during the growing season (from May to September) between 2017 and 2019. The study included a contrast (P0: natural precipitation) and four treatments in which precipitation was decreased and increased by 60 % [P(− S) and P(+ S)] between May and September and decreased and increased by 100 % [(P(− J) and P(+ J)] between May and June. The soil nitrate nitrogen (NO 3 −-N) and inorganic N concentrations significantly increased under P(− S) and P(− J) (P < 0.05) in both fixed dunes and dune grasslands during the growing season. P(− S) and P(− J) significantly increased the soil net nitrification rate (R n) and net N mineralization rate (R m) only in July, with R m significantly increasing with sampling months and years (P < 0.001). The structural equation model showed that R n and R m did not change with water availability variation, and an increase in R m caused by the direct effects of increased precipitation was offset by its indirect effects mediated by reducing electrical conductivity and soil NO 3 −-N concentration while increasing soil water content and vegetation cover. Soil properties and vegetation characteristics were the main factors affecting soil N transformation during the growing season. Our findings are vital for understanding the seasonal patterns, cumulative N transformation, and possible climate change feedback of semiarid sandy land. [ABSTRACT FROM AUTHOR]

• Leaf and soil ecological stoichiometry vary with environmental conditions. • Depressions soil exhibited the highest C, N, and P contents and C:P and N:P ratios. • Leaf stoichiometric characteristics were positively correlated with soil moisture. • Plant community differences resulted from soil hydrological condition variations. • Soil water content was the main factor affecting leaf C, N, and P stoichiometry. Ecological stoichiometry, a novel method for predicting nutrient cycling rates in different habitats, represents the demands of an organism for natural resources and links different levels of biogeochemical cycling. In this study, plant and soil carbon (C), nitrogen (N), and phosphorus (P) concentrations, their stoichiometric characteristics (C:N, C:P, and N:P ratios), and other physicochemical properties of soil were characterized using 243 soil and 81 plant samples collected from three habitats—hummocks, depressions, and meadows—in the marshy wetlands of West China. The results showed that leaf N and P concentrations, soil C, N, and P storage and concentrations, and C:N, C:P, and N:P ratios differed significantly among the three habitats (p < 0.05). Kobresia humilis leaves had the highest N and P content, followed by the leaves of Kobresia tibetica , while Carex mullis leaves had the lowest N and P content. The surface soil of depressions exhibited the highest C, N, C:P, and N:P ratios, hummocks exhibited the highest C:N ratio, whereas meadows exhibited the lowest C and N contents and C:N, and C:P ratios. A structural equation model (SEM) verified that leaf C, N, and P contents and C:P and N:P ratios were positively correlated with soil moisture (SM) and soil organic C contents, whereas the leaf C:N ratio was significantly and negatively correlated with SM content and bulk density. Our findings highlight the ability of alpine marshy wetlands to maintain and even increase the current C, N, and P storage capacities of the ecosystem under increased flooding in the study area. [ABSTRACT FROM AUTHOR]