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• 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]

• Soil water content (SWC) is determined as the outcomes of land use changes. • A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. • The shifts in organic matter sources over time and distinct mechanisms of degradation and preservation of SOM were underscore in wetlands following land use changes. Land use change in wetlands leads to significant losses of soil organic matter (SOM). Stable carbon (C) and nitrogen (N) isotopes offer insights into changes in C3/C4 vegetation, SOM sources, and decomposition processes. Yet, predicting the spatial–temporal dynamics of SOM contents and isotopes under land use changes remains challenging. This study delves into the effects of land use changes on soil organic carbon (SOC), total nitrogen (TN), δ13C and δ15N values, and soil physico-chemical properties and lignin phenols. Our results highlight the significance of soil water content (SWC) in determining the outcomes of land use changes. The conversion of wetland to cropland, forestland and construction land, led to notable reductions in SOC contents (8.71–56.33 %), and TN contents (7.87–37.12 %). Wetland conversion resulted in an enrichment of 13C and 15N abundance, with wetlands exhibiting the lowest δ13C (−25.57 to –22.89 ‰) and δ15N (2.66 to 6.67 ‰) values. A significant correlation occurred between δ13C and δ15N values in wetlands, but underwent considerable changes after wetland conversion. Key parameters, including bulk density (BD), C:N, the acid-to-aldehyde of vanillyl ((Ad/Al)v), lignin content (Λ 8), and total phosphorus (TP), were identified as influencing factors for both SOC and TN contents. When evaluating δ13C values, the most influential factors included silt, C:N, SOC, sand, and BD. These indicate the importance of soil chemical group (from 41 % to 21 %) in elucidating δ13C values declined, while lignin group's (from 9 % to 28 %) importance increased from topsoil to subsoil. The acid-to-aldehyde of syringyl ((Ad/Al)s), Λ 8 , C:N, BD and the cinnamyl-to-vanillyl ratio (C/V) were identified as the primary factors influencing δ15N values, with chemical group accounting for 36 % and lignin group for 48 % in topsoil, while physical group dominated 42 % in subsoil. Our findings underscore the shifts in SOM sources and distinct mechanisms of degradation/preservation of SOM following land use changes. [ABSTRACT FROM AUTHOR]

• A new method to estimate the C-factor for various LULCC scenarios. • Combined changes of climate and LULC leads to increased water erosion in the future. • Impoverished countries are increasingly vulnerable to erosion compared to wealthier nations. • Soil erosion rates are rising faster in lower-middle-income countries due to greater vulnerability. • Significant increase in global soil water erosion is projected after the 2050s. Soil water erosion presents a significant challenge to the sustainable productivity of agriculture, making the precise prediction of its future patterns essential for ensuring global food security. However, there is a notable scarcity of global-scale explorations of soil water erosion and its anticipated future changes. This study proposes a method for calculating the C-factor using the fraction of land use/land cover change (LULCC) scenario data. Subsequently, we conduct an extensive evaluation of global water erosion from the 2010 s to the 2090 s under various climate change and LULCC scenarios, providing a comprehensive analysis of historical and projected erosion patterns. Predictions indicate a rapid increase in total soil erosion, but the rate of increase may decelerate after the 2050 s, with projected average increases of 6.8 %, 9.3 % and 11.3 % per 20-year interval under the SSP1-RCP2.6, SSP2-RCP4.5 and SSP5-RCP8.5 scenarios, respectively. The most rapid increase in soil erosion rates is observed in lower-middle-income countries such as India and Tanzania, which are more sensitive to changes in climate and land use, whereas many high-income countries, predominantly in Europe, are likely to experience a reduction in erosion rates. We emphasize the roles of both climate change and LULCC in shaping future erosion dynamics. Specifically, while LULCC is the dominant factor under the SSP1-RCP2.6 and SSP2-RCP4.5 scenarios, climate change emerges as the chief influencer in the SSP5-RCP8.5 scenario, particularly after the 2050 s. This highlights the importance of devising regional and scenario-specific mitigation approaches, especially for more vulnerable nations. The findings highlight the need for enhanced international cooperation and increased support from low- to middle-income countries to address the challenges of water erosion and promote global sustainability. [ABSTRACT FROM AUTHOR]

• The effects of moisture, type, porosity of soil on thermal property were studied. • Soil and water temperature increases after sun exposure were important factors. • The ANN model was proposed to provide accurate soil moisture estimation. • A rapid, repeatable, and low-price method was proposed to estimate soil moisture. Data of soil water content measured at regular time intervals could be used to set an irrigation schedule for farmland. Changes in soil water content could also provide an early warning of potential slope slippage. An artificial neural network is proposed for detecting soil water content from five variables: soil and water temperature changes after sunlight exposure, plant coverage rates, fine-grained soil content, and effective soil particle size. Temperature changes were detected using thermal images taken using an unmanned aerial vehicle equipped with a thermal camera in the morning and at noon. Plant coverage was estimated using visible light photograph, and the fine-grained soil content, effective particle size, and soil water content were determined from laboratory tests of soil samples. An optimized neural network was established by analyzing the performance of various neural network parameters. The mean square error of the optimized neural network reached a minimum value of 0.10061 in the validation data set at the 12th epoch, the training was stopped to avoid overfitting. The correlation coefficients for the training, validation, testing, and overall data sets were 0.880, 0.772, 0.810, and 0.847 respectively. The target values and the predicted values of the neural network are highly correlated. Thus, the proposed neural network is effective for predicting soil water content. A relative importance analysis revealed that soil and water temperature changes after sunlight exposure had the greatest influence on the neural network's results. [ABSTRACT FROM AUTHOR]

• Recurrent fire leads to degraded rainforest (DRf) and herbaceous-shrubby (HS). • Ksat and 6 years of rainfall-soil suction interactions are analyzed. • HS provide shallow soil saturation even during long dry periods. • Fire decreases Ksat in topsoil and it increases soil suction in depth at HS. • Post-fire soil changes tend to favor rapid suction loss in the unsatured zone. The role of fire in vegetation-soil–water interactions and its implications for soil stability and slope failures is poorly documented in humid tropical regions. This paper focuses on the relationships between vegetation change through recurrent fire and its effects on hydraulic conductivity and soil suction. Two monitoring sites were chosen on steep slopes in the mountainous domain of the Atlantic rainforest: the first is representative of degraded secondary rainforest (DRf) 25–30 years after slash and burn agriculture; the other represents herbaceous-shrubby vegetation (HS) resulting from wildfires in short-time intervals (<5 years). Two fires had previously occurred on the HS slope, one in December 2014 and the other in September 2019. Continuous records of rainfall and soil suction at depths of 10, 20, 50, 100, 150, and 220 cm provided a 6-year data collection from January 2015 to December 2020. Hydraulic conductivity (Ksat) field tests were conducted around the two monitoring sites before and after the September 2019 fire. The main results include: a) soil suction in the topsoil of both vegetation covers follow the rainfall inputs with high values of Ksat (DRf = 195 mm/h; HS = 203 mm/h); b) while quick rainfall-suction responses prevail within the DRf soil profile, soil suction at HS maintains a mean suction value around -27 kPa below 100 cm deep; c) field observations attest to the occurrence of hydrophobicity after the 2019 fire; d) Ksat tests just after this fire indicated a decreasing mean value from 203 mm/h to 46 mm/h; and e) by the end of the dry season after fire, there is a delayed increase in soil suction reaching -143 kPa at a depth of 100 cm and in smaller proportions at 220 cm deep. These results indicate that post-fire soil changes tend to favor the sudden loss of soil stability and slope failure during extreme rainfall events. [ABSTRACT FROM AUTHOR]

[Display omitted] • New pyrite mapping plays a crucial role for soil zonation management in swamp land. • Integrated management of pyrite, soil, water, and nutrients can support rice cultivation. • Swamp lands have low bearing capacity and are susceptible to subsidence. • Soils develop from alluvium with low pyrite overlying coastal sediment with high pyrite. • Significant Al and SO 4 increased while pH decreased from inlet to water canal networks. The idle swamp land of the former mega rice project in Indonesia has the potential for development of paddy field as a response to the global food crisis. Mapping of pyrite (FeS 2) in swamp land as the key driver of soil degradation and poor water quality has not been made to establish a strategy for sustainable paddy field practices. The objective of the study was to assess the spatial distribution of pyrite (FeS 2) through detailed mapping, and to evaluate soil and water properties associated with the adverse effects of pyrite. Detailed conventional pyrite mapping with a grid system at 1:10,000 scale, covering a large area of 26,588 ha, had been made. A comprehensive analysis of soil chemical, physical and mineralogical properties, pyrite content, and water properties was conducted. The detailed pyrite mapping showed that spatial distribution of pyrite was delineated into six depth classes, in the order of decreasing extent: P3-moderately deep (>50–75 cm) > P4-deep (>75–100 cm) ≫ P5-very deep (>100–150 cm) > P2-shallow (>25–50 cm) > P6-exceptionally deep (>150 cm) > P1-very shallow (0–25 cm). These pyrite classes allow zonation management strategy of soils and water table into different depths to avoid pyrite oxidation and its harmful effect. Soils have limited easily weathered minerals (<16 %), implying low inherited soil nutrients. In the topsoils, chemical properties exhibited extreme acidity (pH 3.8–4.2), imbalanced cations with excess Mg, low in K and P and Zn, Cu, and Mn micronutrients. The dynamic changes of water properties in network canals showed a drop in pH from 6.0 at the inlet and primary canal to 2.9 and 3.5 in the canal network (secondary > tertiary > quaternary > pyrite collector), as well as the increased Al and SO 4 ions suggests the decrease in quality throughout the canal network. We propose the management strategy for the sustainable establishment of paddy field in pyritic swamp areas including: (i) performing detailed mapping of pyrite classes to guide depth-based pyrite zonation to control water table, (ii) implementing controlled drainage water flow from inlet to various canal networks corresponds to pyrite depth zonation, (iii) applying lime with Ca-rich materials but not dolomite (containing Mg) to improve cation balance, reduce acidity, increase soil pH and suppress ion toxicity, (iv) utilizing adaptive/tolerant rice cultivars to acidity, and (v) application of NPK fertilizer to alleviate nutrient deficiencies. These strategies can be implemented to ensure the sustainability of paddy fields and avoid soil degradation in swamp land. [ABSTRACT FROM AUTHOR]

• Forest soil properties were measured along the geographical gradient of Carpathians. • Soil respiration spatial variability was driven by soil carbon and nitrogen content. • Soil water content drove differences in soil respiration between 2022 and 2023. • Canopy gaps did not affect soil respiration consistently. Carpathian Mountain beech-fir forests are exposed to severe pressures related to climate change. Alterations in soil respiration, the main source of CO 2 emissions from forest ecosystems into the atmosphere, could potentially impact the future carbon balance of these ecosystems. We performed soil CO 2 efflux measurements along the whole Carpathian arc on eight selected locations during two separate campaigns in 2022 and 2023. The correlations between soil CO 2 efflux and various climatic, micrometeorological, and soil conditions were evaluated as well as the impact of canopy gaps at each site. Soil CO 2 efflux varied between the two campaigns primarily due to fluctuations in soil water content, while differences among the sites were more influenced by soil carbon and nitrogen content. The presence of a canopy gap did not consistently affect soil CO 2 efflux; in some sites, it was lower in the gap than under a closed canopy, while in others, the opposite trend was observed. In conclusion, soil CO 2 efflux measured at eight sites was closely associated with soil properties rather than with climate or micrometeorological parameters. Therefore, the potential influence of climate on the input of new organic matter through forest productivity and species composition will play a significant role in the decomposition and storage of soil organic matter. [ABSTRACT FROM AUTHOR]

• Spatiotemporal DSL variation and associated forcings were explored at a semi-humid catchment. • Land use type was the dominant control on DSL variation at a catchment scale. • DSL response to meteorological factors differed between the semiarid and semi-humid catchments. • The mixed "forest/shrubland + grass" plantation type is recommended for the semi-humid catchment. The formation of dried soil layers (DSLs) is a broad consequence of climate change (i.e., through temperature increases and/or precipitation decreases) and poor land management practices, where these layers exist has severe negative effects (i.e., retardation of vegetation, negative water cycle balance) on the sustainability of restored ecosystems and health of agriculture. Because of the effort and time required, only sporadic in situ measurements on spatial and temporal DSL variation have been reported, particularly at a catchment scale. However, this information is essential for understanding mechanisms associated with evolutionary DSL processes as well as developing effective land management techniques. Accordingly, this study monitored soil water content to a 5 m depth over a 5-year period in a semi-humid catchment on the Loess Plateau while also investigating temporal DSL dynamics and dominant controls. In the semi-humid catchment, DSLs occurred at 90.7 % of all sampling sites. Spatially and temporally averaged DSL formation depth (DSLFD), DSL thickness (DSLT), and DSL soil water content (DSL-SWC) within the 0–5 m profile were 170 cm, 262 cm, and 9.52 %, respectively. Forest and shrubland DSL regimes were drier than those of grassland. These three DSL indices exhibited significant correlation with temperature variables, while only DSLFD variables significantly correlated to precipitation. Land use type was the predominant control of DSL variation at a catchment scale. A spatial DSLT variation comparison under different land use treatment positions determined the feasibility of planting grass at an upslope position and mixed forest/shrubland + grass at mid-slope and downslope positions in the semi-humid catchment, which provides a good case study for afforestation practices at a catchment scale. Findings from this study are intended to aid in catchment soil and water conservation, soil drought mitigation, and sustainable vegetation management practices on the Loess Plateau as well as other water-limited regions worldwide. [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]

[Display omitted] • Soil properties and enzymatic activities varied across land use types and villages. • Agroforestry establishment accelerated soil enzymatic activities by 39.41–90.17%. • Cultivation caused massive decline in level and variability of enzymatic activities. • Climate, vegetation, and management practices determined the enzymatic activities. Soil microbial enzymatic activities, often used as indicators of soil health and fertility, are vulnerable to changes in climate and anthropogenic activities. This study analyses the responses of specific soil enzymatic activities– dehydrogenase (DHA), acid phosphatase (APH), β-glucosidase (BG) and urease (URE)– in Nitosols/Luvisols of the subtropical zone of the Central Himalaya, India. We investigated how these enzymatic activities vary with different land uses: arable land (AL), kitchen garden (KG) and peach orchard (PO), across four villages– Niglat, Kainchidham, Majhera and Syalikhet. Considering associated management practices, we quantified cumulative average soil enzymatic activities for the rabi season (2017–2018). In general, catalytic activity of the selected enzymes was highest in Syalikhet and lowest in Majhera. However, for land use types, enzymatic activities were lower in AL and KG (75.56–90.17% and 39.41–61.72%, respectively) compared to PO values. MANOVA analysis evaluated significant spatial differences (P < 0.001) in enzymatic activities. Soil enzymatic mean values were highest in the surface layer (0–10 cm) and decreased gradually with increasing depth. Parameters such as soil moisture content (SMC) and pH, along with vegetation, management practices, and nutrients such as SOC, TN, K, AP, and N forms (NH 4 +–N and NO 3 ––N) showed significant and strong correlations with all the soil enzyme activities (r = 0.40–0.97; P < 0.05). TN, SOC, K, SMC, pH, AP, NH 4 +- N, and clay content were key determining factors of soil enzymatic activities, explaining approximately 59% of the variation. These results suggest that using soil microbial enzymatic activities as soil quality indicators is a feasible approach to assess the impacts of vegetation, management practices, and soil profile depths in soils under different land use types/systems in selected impoverished villages of the fragile Central Himalaya, India. [ABSTRACT FROM AUTHOR]

• SWAT-Twn 2.0: Enhanced model with adaptable landslide triggers improves sediment simulation. • Dual triggers (PCP: rainfall and FSW: fraction of soil water content) in SWAT-Twn 2.0 show superior performance. • PCP trigger significantly affects landslide identification accuracy. • Lack of particle size leads to channel deposition overestimation. • Incorporate landslide characteristics into HRU (Hydrologic Response Unit) classification to address limitations. Landslides, caused by heavy rainfall, earthquakes, or human development, are likely occur in steeper slopes, while some occur in moderate slopes (15°– 35°). Although landslides can contribute a significant amount of sediment transport in a watershed, landslides are rarely considered in hydrological models. To conduct a thorough investigation into the influence of landslides on sediment transport within rivers, a detailed analysis of landslide characteristics was performed. Subsequently, a dedicated landslide module was integrated into a hydrological model, known as SWAT-Twn 2.0 – an enhanced version of SWAT-Twn, originally developed by Chiang et al. (2021). This integration allowed for the simulation of sediment transport at the hydrologic response units (HRUs) within the Xiuguluan River Basin, a mountainous watershed located in Taiwan. The study explores multiple threshold values for landslide-triggering factors (PCP: rainfall and FSW: fraction of soil water content), emphasizing the influence of the number and locations of rainfall stations on landslide identification. In comparative scenario simulations (S1: no trigger, S2: single trigger, S3: dual trigger), the integration of dual triggers (PCP + FSW) significantly improves sediment simulation results, particularly for peak total load (S3: R2 = 0.83, NSE = 0.74, PBIAS = 23.69 %). It also emphasizes the importance of specifying the particle size distribution of landslides for accurate sediment deposition calculations. In summary, it is necessary to consider landslide-triggering factors in hydrological models to enhance accuracy in sediment yield simulations. To further improve landslide identification and sediment transport modeling, the study recommends incorporating additional triggering factors into HRU classification (i.e., elevation and aspect). [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]

[Display omitted] • The effect of precipitation and topography on terrestrial water patterns was revealed. • The sensitivity of SHP branches to terrestrial hydrological variables was measured. • Soil porosity is the most significant SHP parameter in influencing terrestrial water. • The sensitivity of β and α increases in steep areas and during drier periods. Terrestrial water, which plays an essential role in ecosystems, is unbalanced in terms of storage and distribution patterns under natural conditions. The formation mechanism of this imbalance is relevant to soil hydraulic properties (SHP), surface terrain, and meteorological factors. In this study, the features of high-precision hydrological models and their specific soil hydraulic parameters were useful in providing some important insights and an effective approach towards a better understanding of the mechanisms that affect the representative terrestrial hydrological variables. First, the Penn State Integrated Hydrologic Model (PIHM), a physically based, coupled surface–subsurface hydrological model was used to investigate the relationship between terrestrial water distribution patterns and external driving factors of the study area within Yunnan Province, China. Subsequently, a variance-based sensitivity analysis method was used to measure the effects of SHP on terrestrial hydrological variables and their variability under different driving factors, including rainfall intensity and surface topography. It was found that (a) the areas with lower elevations and plain terrain tend to retain more soil moisture, (b) generally, the porosity of soil is the primary determiner of soil moisture storage and groundwater depth among other hydraulic properties, and (c) the importance ranking of the SHP parameters changes according to precipitation, surface elevation, and slope. [ABSTRACT FROM AUTHOR]

• Subsurface lateral flow often occurs at 10–40 cm depths along the hillslope. • Wet soil conditions are conducive to triggering hillslope lateral flow. • Variability of infiltration partitioning remains high in the deeper layers. • Dominant factors controlling PWSI are sand (0–10 cm), EL (10–40 cm), and n (40–80 cm). Infiltration is the process of water entering into, and routings through, the subsurface. It has a profound impact on hillslope and catchment runoff. However, because of the hidden and complex subsurface structures, our understanding of rainfall-related infiltration and how it partitions along a topographic gradient remains challenging. In this study, we used two years of field observations of volumetric soil moisture at 25 combinations of topographic positions and soil depths along a steep subtropical forested hillslope. The lateral partition patterns of infiltration and its control factors were investigated based on a new index, percentage of soil water storage increment at each site to all hillslope sites during a rainfall event (PWSI). Our results showed that the active soil layer involved in hillslope lateral flow was distributed within the depths of 10–40 cm. In deep soil depths (i.e., 40–80 cm), lateral flow was more evident under wet initial moisture conditions than under dry initial moisture conditions, whereas rainfall characteristics had a relatively weak effect on it. Unexpectedly, we found the variability of infiltration partitioning remained high in the deeper soil layers. Among the soil properties, sand, bulk density, n , K S , and SOM were conducive to infiltration, whereas clay had the opposite effect. The dominant factors controlling the lateral partition patterns of infiltration across soil depths were sand in the depths of 0–10 cm, topographic gradient in depths of 10–40 cm, and n (parameter of soil retention curve) in the depths of 40–80 cm. Findings of this study reveal the infiltration partitioning indices were useful to quantitatively describe the distribution patterns of infiltration after rainfall events at the hillslope, and provide new insights into the detection of hillslope lateral flow, which is valuable for understanding subsurface hydrological processes and improving water resource management in humid mountain ecosystems. [ABSTRACT FROM AUTHOR]

• Drying-rewetting had no effect on soil respiration when straw was absent. • Drying-rewetting had a strong legacy effect on SOM mineralization when straw was added. • Drying-rewetting cycles reduced cumulative straw decomposition. • Drying-rewetting effect on PE diminished with the increase in the number of drying-rewetting cycles. Soil moisture serves as a pivotal environmental variable that governs the cycling of soil carbon (C). Although numerous studies have been conducted to evaluate the impact of drying-rewetting cycles on soil organic matter (SOM) mineralization, the dynamic changes in SOM priming effect (PE, i.e. the change in SOM mineralization after the addition of an exogenous substrate) under frequent drying-rewetting cycles remain unknown. Here, we conducted a 209-day incubation experiment utilizing 13C-labeled maize (Zea mays L.) straw to investigate how repeated drying-rewetting events influence straw decomposition, SOM mineralization, PE, and soil net sequestration of straw-C. The experimental design involved two contrasting soil moisture conditions (constant vs. varying water content) with or without maize straw amendment. Results showed that, in the absence of maize straws, drying-rewetting cycling did not significantly alter the cumulative SOM mineralization throughout the incubation period. Conversely, in the presence of maize straws, the cumulative decomposition of straws under drying-rewetting cycles was diminished by 9.8% compared to the constant water conditions. Moreover, a notable increase of the cumulative PE by 19.3% under recurrent drying-rewetting events resulted in a substantial reduction of soil net C sequestration of straw-C (straw-derived C incorporated into the soil minus the C loss primed by straw) by 22.3% compared to the constant water conditions after 209-day incubation, suggesting that frequent drying-rewetting might diminish the function of soil as a C sink. Overall, drying-rewetting cycles generally decelerated straw decomposition and reduced the recovery of straw-C in microbial biomass C and soil matrix, indicating that enhanced frequency and intensity of drying-rewetting cycles in future climate scenarios may have detrimental effects on soil C sequestration. [ABSTRACT FROM AUTHOR]

• The probability of large-scale extreme drought was higher in forest ecosystems. • Compared to natural ecosystems, soil drought was more likely to occur in farmland ecosystems during winter. • The interaction between environmental factors in farmland ecosystems was stronger than that in natural ecosystems. • The dominant factor of soil drought in farmland ecosystems was temperature, and that in forest and grassland ecosystems was vegetation. Soil drought exhibits diverse characteristics across ecosystems due to intricate interactions within the soil–plant-atmosphere continuum. However, the dynamic variability and dominant factors of soil drought in different ecosystems remain unclear. To address this knowledge gap, this study characterized soil drought according to the standardized soil moisture index (SSMI) constructed using root-soil moisture data of the Global Land Data Assimilation System. Environmental factors were classified into three categories, namely climate factors (precipitation, temperature, and potential evapotranspiration), vegetation factors (NDVI and LAI), and topographic and soil factors (elevation, slope, aspect, groundwater storage, and soil texture). On this basis, the impact of terrestrial and meteorological multi-factors and their interactive effects on soil drought variation were examined through correlation analysis. Moreover, redundancy analysis (RDA) was employed to quantify the contribution of multiple drivers to soil drought in ecosystems, as well as identify the dominant factor. The results indicated that: (i) large-scale extreme drought events are more likely to occur in forest ecosystems than in farmland and grassland ecosystems; (ii) the duration of soil drought was longer in winter, especially in forest ecosystems; (iii) in winter, soil drought is more likely to occur in farmland ecosystems than in natural ecosystems; (iv) in farmland, grassland, and forest ecosystems, environmental factors explained 71.9%, 74.0%, and 77.8% of the changes in soil drought, respectively; (v) the dominant factor controlling soil drought was temperature for farmland ecosystems (F =321.20, p <0.01), and vegetation for forest (F =212.36, p <0.01) and grassland ecosystems (F =168.00, p <0.01). [ABSTRACT FROM AUTHOR]

• Slope aspect had a significant effect on the distribution of humus on cut slopes. • The contents of humus carbon were higher in north-facing slope significantly. • Macro-aggregates and micro-aggregates stored more humus carbon for bulk soil. • Slope aspect tended to affect humus carbon indirectly by adjusting SWC, SOM, TN, and AP. Large-scale road construction has resulted in bare cut slopes in alpine areas, leading to soil erosion and reduced fertility. Soil humus is the basis of soil fertility and an important carbon pool; it is affected by many factors. However, the effects of slope aspect on soil humus on cut slopes are still largely unclear. We studied the differences in the humus content in bulk soil and soil aggregates under four slope aspects (south-facing slope (SFS), west-facing slope (WFS), east-facing slope (EFS), and north-facing slope (NFS)) in alpine areas and analyzed the driving effects of soil physicochemical factors on humus distribution. The contents of fulvic acid carbon (FA-C), humic acid carbon (HA-C), humin carbon (HU-C), humus extractable carbon (HE-C) and total humus carbon (TH-C) differed among four slope aspects. Humus carbon did not differ among large macro-aggregates (LMA), small macro-aggregates (SMA) and micro-aggregates (MIA). Only the contents of humus carbon in silt + clay fraction (SCA) were significantly lower than those in the other soil aggregates for the NFS and EFS. Soil water content (SWC), soil organic matter (SOM), total nitrogen (TN), and available phosphorus (AP) were important soil physicochemical factors affecting the distribution of humus. Our results suggest a significant effect of slope aspect on the contents of humus carbon, and the silt + clay fraction had a weak ability to retain humus carbon. The study provides a theorical basis for future humus research and soil fertility management of cut slopes in alpine areas. [ABSTRACT FROM AUTHOR]

• O Understory vegetation recovery generally occurs faster than soil recovery in coastal forest. • O Soil microbes form spatially separated groups induced by reforestation. • O No consistent pattern exists for plant or soil traits responded to afforestation. • O Recovery of understory plant and soil traits strongly depends on soil conditions. The low-cost, ecologically friendly afforestation in coastal regions has been used to mitigate the natural degraded ecosystem. However, ecological consequences of this land use change are poorly known. We investigated the a short-term (2.5 years) effect of afforestation of a pioneer tree species, Casuarina equisetifolia , on understory vascular plants and surface soil traits (0–10 cm) at two closely-located sites (Heipaijiao and Haigui) in a subtropical coastal region, south China. Generally, plant abundance, vegetation coverage, and soil fertility in the natural degraded land were higher in Heipaijiao than in Haigui. After afforestation, the understory vascular plant abundance (increased by 46.1 %) and coverage (increased by 86.1 %) in Heipaijiao were recovered remarkably faster than those in Haigui; but there was slow recover in plant species composition, especially in Haigui. Owing to afforestation, soil water content and organic C (especially particulate organic C), electricity conductivity, Na+ and available K, and soil microbial biomass C increased but pH value decreased; the contents of total N, P and K, available N and P contents, and mineral-associated organic C had no great difference. Afforestation enhanced the richness, rather than alpha diversity, of soil bacteria and fungi. Soil microbes formed four spatially separated groups exhibiting overlapping and distinct microbial communities across different land-use types. Afforestation had a significant effect on the putative two-dominant functions of soil bacteria, i.e., soil C and N cycling. Thus, afforestation can maintain ecosystem multifunction quantified based on C sequestration, nutrient cycling and plant productivity. Understory plant recovery occurred faster than soil recovery; but no consistent restoration pattern existed for soil traits responded to afforestation. Recovery of understory plant and soil traits strongly depends on local soil conditions. This afforestation success story of selecting a well-adapted pioneer tree (C. equisetifolia) as foundation species provides insights into the restoration practice under harsh environmental conditions. [ABSTRACT FROM AUTHOR]

• Evaluating the effect of afforestation on deep soil environment within level ditch. • Shrubs of different planting years caused the difference in deep soil water storage. • Positive effect of slope on soil carbon/nitrogen storage reduced with soil depth. Vegetation restoration can sequester more carbon to address global climate change and conserve biodiversity to maintain soil ecological functions. The combination of engineering measures and afforestation is a prominent strategy to restore degraded slope ecosystems. Engineering measure alters slope topography and reconstructs the microtopography which is differed completely from other positions; however, the studies about the effects of afforestation on the deep soil environment within microtopography are still unclear. In this study, the changes of the soil water in the different layers of 0–4 m and the soil carbon and total nitrogen in that of 0–1.2 m in the level ditch combined with C. korshinskii planted for 17 years (17y), 28 years (28y), and 36 years (36y) were analyzed, and naturally restored slope was used as the control (CK). The results showed that compared with CK, the soil water storage (0–4 m) under 17y, 28y, and 36y was significantly decreased by 22.9 %, 26.8 %, and 36.5 %, respectively. The soil water storage (2–3 m) under 28y and 36y was evidently decreased by 29.0 % and 41.7 % compared with 17y, and the one (3–4 m) under 36y was significantly decreased by 13.8 % and 21.5 % compared with 17y and 28y, respectively. The soil carbon/nitrogen storage (0–1.2 m) was decreased by 40.5 %/41.7 % under 17y and was increased by 20.6 %/22.4 % under 28y compared with CK, the one under 28y and 36y was significantly higher 103 %/110 % and 81.5 %/82.8 % than that under 17y. Based on stepwise regression analysis, shrub volume and slope significantly impacted water storage and carbon/nitrogen storage, respectively. The significant differences in the effects of C. korshinskii of different planting years on soil water storage were mainly found in deeper layers. Our findings provide insight into the alterations of the deep soil environment within the microtopography reconstructed by engineering measures in the context of vegetation restoration. [ABSTRACT FROM AUTHOR]

• Insolation differences among the aspects amplify the variability in soil moisture. • Soil moisture and vegetation variability are sensitive to geomorphic factors. • Aspect-related vegetation differences are more pronounced in smaller contributing area. • Landscapes generated under low uplift rates display less spatial variability. Landscapes evolve through nonlinear interactions between soil, vegetation, and climate. In semi-arid ecosystems, soil moisture variability (SMV) and vegetation variability (VV) can be strongly related to landscape organisation induced by differences in insolation on opposing north-facing slopes (NFS) and south-facing slopes (SFS). Due to its complex interactions with various processes and factors, soil moisture and vegetation exhibit significant variability in both space and time. In this study, the Channel-Hillslope Integrated Landscape Development (CHILD) landscape evolution model (LEM), coupled to a dynamic vegetation model (BGM) and equipped with a spatially distributed solar radiation component is used. The model is used to investigate the implications of various soil, climatic, and geomorphic factors on SMV and VV over landscapes with different characteristics. The analysis of model results indicates that SMV and VV are more sensitive to changes in geomorphic (hillslope diffusion and uplift rate) and climate (solar radiation, precipitation) factors than to soil hydrologic factors (anisotropy, porosity, infiltration capacity, root depth, and pore size distribution) considered in this study. Spatial variability increases with decreases in hillslope diffusion, and with increases in uplift rates and latitude, while temporal variability has the same response to those factors, and also increases with precipitation. All of these factors contribute to larger difference in condition on NFS and SFS, which ultimately is reflected in SMV and VV. Slope-area, soil moisture-area, and vegetation-area relationships revealed that the difference in SMV and VV between NFS and SFS is more pronounced for smaller contributing areas, where NFS are steeper than SFS. They also show that the temporal variability of soil moisture and vegetation is less in SFS than in NFS. [ABSTRACT FROM AUTHOR]

• Quantified the effect of discharge on erosion and morphology characteristics. • The impact of rill depth on cumulative sediment yield was greater than that of rill width. • Unit stream power can be used to describe dynamic mechanisms of eroding rill. • Rill erodibility parameters for eroded rill were 0.574 × 10−3 s m−1. Field experimental studies on the erosion characteristics and dynamic mechanisms of rills that have already eroded (eroded rills) when rainfall occurs are limited, especially compared to the dynamics of those rills that have experienced erosion for the first time (eroding rills). The field runoff scouring experiments included two intermittent sub-experiments: flow discharge of 9, 13, 17, 21, 25, and 29 L min−1 (E1) with a scour duration of 60 min and flow discharge of 6, 9, 12, 15, 18, and 21 L min−1 (E2) with a scour duration of 10 min. Two antecedent soil moistures (15 % and 25 %) were used for the runoff plot (18 × 1 m) before starting E1. The results from E1 indicated that flow discharge and antecedent soil moisture increased the average runoff rate (19.46 % with discharge, 4.63 % with soil moisture), soil loss rate (63.94 % with discharge, 58.80 % with soil moisture), rill width (16.49 % with discharge, 4.66 % with soil moisture) and rill depth (13.40 % with discharge, 6.60 % with soil moisture). The average flow velocity varied from 0.231 to 0.344 m s−1, and the flow regimes were basically subcritical turbulent flows. The impact of rill depth on cumulative sediment yield was greater than that of rill width. Moreover, the critical values of flow velocity, shear stress, stream power, unit stream power, and unit energy under eroded rills were 0.183 m s−1, 7.532 Pa, 1.278 W m−2, 0.032 m s−1 and 0.007 m from E2, respectively, and the rill erodibility parameters for E1 and E2 were 0.252 × 10−2 and 0.574 × 10−3 s m−1, respectively. The flow unit stream power and stream power could be effectively used to simulate the dynamic mechanism under conditions E1 and E2, respectively. The study aids in understanding the dynamic mechanism of rill erosion under intermittent rainfall conditions in the field. [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]

• Soil compaction induces changes in the water retention curve. • Air entry pressure, water content levels and void size distribution are impacted. • Fast imaging analysis techniques are good approaches for retention curve estimation. Soil hydrological and agricultural properties are highly affected by the soil water retention characteristics, which are closely related to the void size distribution and structure of the soil. Agricultural lands are often faced with the challenge of soil compaction, which alters the size, shape, connectivity, and morphology of soil voids. To determine the water retention curve and other hydrological and agricultural functions of un-compacted and compacted sandy soils, we used micro-CT techniques and image analysis procedures in both two and three dimensions. We found that these techniques were reliable, as they were validated against physical measurements and empirical physically-based models, and provided a relatively simple and fast way to characterize the key features of soil hydrological and agricultural properties. The findings highlight the impact of compaction on the soil void size distribution, resulting in increased water holding capacity, greater water availability for root uptake, and reduced hydraulic conductivity. We also discussed the differences between the two and three-dimensional analyses, highlighting the better ability to characterize soil hydrological and agricultural functions and soil water retention curve using the three-dimensional image analysis approach. [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]

• Droughts increased CH 4 uptake in a wet year in the semiarid grassland. • Magnitude and pathways of drought effects on CH 4 uptake depend on seasonal timing. • Positive effects of early drought on CH 4 uptake were the least. • Plant composition regulated CH 4 uptake in response to droughts. Increasingly frequent and severe droughts are occurring in multiple seasons of a year in many dryland ecosystems, with unknown impacts on the role of drylands in cycling of methane (CH 4), a potent greenhouse gas. In particular, there is limited understanding of how drought occurring at different times within the growing season regulates biological CH 4 uptake, and how these responses are mediated by plant community composition. Here, we quantify how drought timing and plant community composition regulate CH 4 uptake in a semiarid grassland. We employ a field experiment in which droughts were imposed in early, middle, or late growing season in three different communities (two graminoids, two shrubs and their mixture), respectively. All three droughts increased CH 4 uptake, but the effect size and pathway varied with seasonal timing. Early and middle drought increased CH 4 uptake through increasing both soil pomA abundance and diffusivity resulting from reduced soil water content (SWC), while late drought increased CH 4 uptake only by reducing SWC. Overall, early drought had the least positive effects on CH 4 uptake because it excluded the least precipitation and therefore had smaller impacts on SWC. Besides, plant composition did not affect CH 4 uptake under normal environment but regulated CH 4 uptake in response to droughts due to different response of plant composition to droughts. Early and middle drought had larger positive effects on CH 4 uptake in shrub communities than the other two communities, consistent with larger reductions in SWC and larger increases in pomA abundance, respectively. In contrast, late drought had consistent effects on CH 4 uptake across three communities. Our results suggest that the magnitude and pathways of extreme drought effects on CH 4 uptake are strongly co-regulated by seasonal timing and plant composition. [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]

• Deep soil and adjacent farmland were both important water sources for apple trees. • SWD increased at a rate of 5.94 mm m−1 yr−1 in apple orchard before 30 years of age. • The migration and accumulation of NO 3 –-N confirmed the soil water exchange. • The orchard-farmland pattern can promote efficient water and nutrient use in the CLP. With the vigorous promotion of apple tree planting on the Chinese Loess Plateau (CLP), a mosaic pattern of apple orchards and traditional farmland has emerged in the region. However, the interaction between adjacent farmland and apple orchards in terms of soil water and nutrient migration remains unclear. This study aimed to investigate the spatial distribution of the soil water content (SWC) and soil nutrients, as well as their interactions, in 0–10 m soil layers of apple orchards of different stand ages and adjacent farmland under the orchard-farmland land use pattern. The results revealed a significant decrease in average-depth SWC in the orchards in the 0–10 m soil profile (R2 = 0.90) with increasing orchard age, accompanied by a significant increase in soil water deficit (SWD, R2 = 0.94). The annual growth rate of SWD was found to be as high as 5.94 mm·m−1·y−1. Deep soil and surrounding farmland were identified as important sources of soil water for apple tree growth, particularly in older orchards; a 25-year-old orchard absorbed approximately 10.8 % of soil water towards farmland with a horizontal distance of 7 m. The distribution of soil organic carbon (SOC) and total nitrogen (TN) in the 0–10 m soil profile exhibited a similar pattern, decreasing and then stabilizing with increasing depth. However, the peak depth and accumulation of soil nitrate (NO 3 –-N) significantly increased with orchard age. The migration and accumulation of NO 3 –-N in the soil provided a scientific basis for the transport of soil water, with NO 3 –-N accumulation (405.32 mg kg−1) observed in the deep soil (3–6 m) of farmland located 5 m away from a 30-year-old orchard, confirming the exchange of soil water and nutrients between the orchard and the farmland. The stand age of the orchards was identified as the main environmental factor influencing soil water transport under the orchard-farmland land use pattern. Overall, our findings provide valuable insights into the interaction between apple orchards and farmland under the mosaic pattern, which can contribute to a more rational layout of apple orchards and farmland in the future, promoting the efficient utilization of soil water and nutrients on the CLP. [ABSTRACT FROM AUTHOR]

• The warming trend of climate is more than twice in the RS region than in the entire DP. • TWS decreased significantly due to the reduced rate of climate moistening after 2009. • GWSA has the longest response time to rainfall among all constituent components of TWS. • SMSA and GWSA were two major contributors to the TWSA in both the DP and RS regions. • SWSA played a vital role in TWS variability, particularly in the RS region. Inter-state river water disputes are frequent over the rain shadow (RS) region of the Western Ghats (WG), where the annual rainfall is much lower (75.2 cm) than that of overall India (118 cm). This study investigated the TWS (Terrestrial Water Storage) dynamics of the entire Deccan plateau (DP) and RS regions, located at the leeward side of the WG mountain range, with the help of Gravity Recovery and Climate Experiment (GRACE) based TWS anomalies (TWSA) data. Here, the latest TRMM (Tropical Rainfall Measuring Mission) rainfall product was evaluated at different time scales against gauge-based measurements to check its applicability as an alternative to gauge-based observed data. Trends in climate variables and TWSA were estimated to understand their variations during 2003–2016 in both regions. The response of GRACE-based TWSA and its constituent components to rainfall was determined using time-lagged correlation analysis. The contribution of constituent variables to TWSA was estimated using the component contribution ratio (CCR) method. It was observed that the TRMM-3B43 data captured the rainfall pattern over the entire DP with great accuracy. Results showed that the increasing trend of TWS in 2003–2009 had reversed in 2010–2016 due to the reduction of climate moistening in both regions. The warming trend of climate is more than twice in the RS region than that found in the DP, leading to a higher decreasing rate of TWS in this region than in DP. For both DP and RS regions, the time lags of groundwater storage anomalies (GWSA), total runoff anomalies (RA), canopy water storage anomalies (CWSA), and soil moisture storage anomalies (SMSA) to rainfall can be arranged as CWSA ≤ RA ≤ SMSA ≤ GWSA. SMSA and GWSA are the main contributors to the TWSA in both areas. However, SWSA also played a vital role in TWS variability, particularly in the RS region. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fire and grazing significantly compact soil and reduce soil water retention. • Fire + grazing increase average root diameter and decrease specific root length. • Litter directly alters soil pore volume fractions and indirectly influence root traits through soil bulk density. • Annual fire and grazing lead to the degradation of tallgrass prairie. The native Konza tallgrass prairie is maintained by two key natural processes, periodic fire and ungulate grazing. As a potential crucial feedback mechanism, how fire and grazing influence plant root traits and soil properties in the tallgrass prairie ecosystem remains less known. Here, we investigated the effects of long-term fire and grazing regimes on soil physical properties and root traits at the Konza Prairie Biological Station, near Manhattan, KS, USA. Soil cores were collected under control (unburned and ungrazed), fire (annually burned), grazing (annually grazed), and fire + grazing (annually burned and grazed) treatments. Soil water retention, total root volume, specific root length, specific root area, and root biomass were measured. We found that both fire and grazing significantly reduced soil water retention, increased soil bulk density and soil microporosity (<50 μm), and reduced macroporosity (>50 μm) compared to the unburned and ungrazed treatment. Fire and grazing also significantly reduced litter accumulation by 79 % (burned), 57 % (grazed), and 77 % (burned and grazed). Fire increased specific root area by 15 %. Grazing and fire + grazing significantly decreased specific root length by 40 % and 29 %, and specific root area by 33 % and 24 %, respectively. Litter production was positively related to soil volumetric water content and soil pore volume of 300–50 μm, but negatively related to soil bulk density and soil pore volume of less 50 μm. Soil volumetric water content was positively correlated to specific root lengths, and soil bulk density was negatively related to specific root length and specific root area. There was a significant negative relationship between root diameter and soil volumetric water content under burned and grazed treatment. The SEM model showed that fire, grazing, and fire + grazing regimes were associated with dead root biomass (R2 = 0.38) and root length density (R2 = 0.40) indirectly through soil bulk density and litter accumulation. Our findings suggested that the annual fire + grazing regime seriously leads to the degradation of tallgrass prairie by influencing soil physical properties, reducing root trait functions and root biomass, and altering the relationship between root diameter and soil volumetric water content. [ABSTRACT FROM AUTHOR]

• LSF came directly from SPG in an alpine-permafrost hillslope. • The indirect-sources of LSF were precipitation and ground ice. • Ground ice dominated LSF in initial thaw phase, yet precipitation in later phases. • SPG dominates hydrological processes as increasing thaw depths. • Ground ice signals due to permafrost degradation exist in long-term runoff records. Climate change has resulted in significant changes to subsurface hydrological processes in permafrost regions. Lateral subsurface flow (LSF) represents the dominant flow path in hillslope runoff generation. However, the contributions of runoff components to LSF, such as precipitation, soil water, and ground ice, remain unclear. This study aimed to characterize LSF generation processes in an alpine permafrost hillslope of Northeastern Tibetan Plateau, using stable isotopes and total dissolved solids (TDS) as tracers. Samples of precipitation and soil water [including mobile soil water and supra-permafrost groundwater (SPG)], LSF, and ground ice samples were collected from different thaw depths of the active layer in 2021. The results showed that LSF came directly from SPG in the active layer. Two-source partitioning using δ2H or TDS suggested that the dominant source of LSF gradually shifted from ground ice during the initial thaw period to precipitation with increasing thaw depths. The contributions of ground ice to LSF were 70 % and 30 % at thaw depths of 0–30 cm and >30 cm, respectively. The results of three-source partitioning indicated ground ice, precipitation, and SPG to be the dominant sources of LSF at thaw depths of 0–30 cm, 30–150 cm, and >150 cm, respectively. SPG largely regulates hillslope hydrologic processes at thaw depths ≥250 cm. Therefore, with continuing climate warming, SPG will play an increasing role in hydrological processes of alpine meadow permafrost hillslopes. [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]

• 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]

• The relationship between gross N turnover and temperature and moisture varies on annual and seasonal scales. • The gross N turnover under the influence of temperature and water is different between field and laboratory conditions. • Soil temperature has more influence on soil gross nitrogen turnover than moisture. Understanding how soil nitrogen (N) turnover responds to temperature and soil moisture alterations is important for accurately predicting responses of soil N availability and plant productivity to global climate change. However, few studies had explored such questions under natural conditions. We investigated effects of temperature and moisture on soil gross N turnover with an annual scale field experiment in an Inner Mongolian grassland and a laboratory incubation experiment. In the field experiment, on the annual scale both gross ammonification and nitrification rates showed a hump-shaped response to temperature, with maximum rates occurring around 10 °C and 5 °C, respectively. Gross ammonification rates did not respond to soil moisture, and gross nitrification rates decreased first and then increasing with soil moisture, which the threshold was 35% water holding capacity (WHC). Totally, soil temperature explained more variation than moisture in gross ammonification (0.30 VS 0.04) and nitrification (0.24 VS 0.14) rates. On the seasonal scale, both soil temperature and moisture showed generally significant effects on gross N turnover. Grazing had no effects on soil temperature and moisture sensitivity of gross N turnover on the annual scale, but increased the sensitivity of gross ammonification to soil moisture during the spring freeze–thaw period. In the laboratory incubation experiment, gross ammonification and nitrification rates increased with the increase of temperature, although there was no difference between 20 °C and 30 °C. Gross ammonification rates reached a maximum at 50% WHC, while gross nitrification rates did not respond to soil moisture until 100% WHC. Soil temperature explained more variation than moisture in gross ammonification (0.71 VS 0.01) and nitrification (0.37 VS 0.25) rates. Our results imply that climate warming may have greater impact on gross nitrogen turnover compared to changes in rainfall, however it remains great uncertainty due to the low explanation of soil temperature and moisture. [ABSTRACT FROM AUTHOR]

• Artificial restored shrub and grass aggravated soil deficit but they got replenished better under large rainfall. • The effects of revegetation and topography on SWS varied greatly with rainfall. • Water-intensive vegetation species should be used cautiously for revegetation. The Chinese Loess Plateau (CLP) rose to prominence for its fragmented terrain and fragile ecosystems. Large-scale revegetation was applied to control soil and water loss there. However, revegetation resulted in unexpected water shortages. In this study, we investigated the temporal-spatial distribution of soil water in the northern CLP based on 13-year soil water content (SWC) data of four different revegetation types on a loessial slope and 4-year data of a gully system to study the response of soil water to long-term revegetation, topography, and precipitation. Results showed that in the 0–400 cm soil depth under shrub, grass, natural fallow, and millet, soil water storage (SWS) was –102.8, –129.3, 54.9, and 39.3 mm higher after 13-year of restoration, respectively. Although soil water under shrubs- and grasslands became more replenished under high precipitation, planting these water-intensive vegetation types aggravated soil desiccation. The gully intensified soil water spatial heterogeneity, with mean SWS within 0–480 cm soil depth of 902, 712, and 746 mm at the gully bottom, edge, and bank, respectively. The deviation index among the four revegetation types and among gully bottom, edge, and bank were 0.43 and 0.26, respectively, which indicated that revegetation types had a more obvious effect on SWS. Given that more concentrated rainfall under global climate change, both revegetation type and topography should be considered during ecological restoration in semi-arid areas. These findings can deepen our comprehension of the hydrological processes on the CLP and provide a reference for the development of ecological restoration policies under future climate change. [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]

• 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]

• MNC accounted for 15.81% − 36.62% of SOC in drawdown areas. • MNC content in vegetated areas was higher than in mudflat areas. • C and N availability dominated and directly regulated MNC accumulation. • Drawdown areas in lakes have lower MNC in SOC compared to terrestrial ecosystems. Lake drawdown areas - where sediment is exposed to the atmosphere due to water level fluctuations - have a nonnegligible impact on the carbon cycle. However, our knowledge of microbial necromass carbon (MNC) in the drawdown area remains to be seen, which has been considered an essential precursor to soil organic carbon (SOC). Here, we examined the content of MNC and its contribution to SOC in three typical habitats (mudflat, grass, and reed area) from the water edge to the uplands in the seasonal drawdown area of Dongting Lake. MNC content in the drawdown area ranged from 1.31 to 3.73 g kg−1, accounting for 27.39 %, 24.51 %, and 27.91 % of SOC in mudflat, grass, and reed areas, respectively. Compared to mudflat areas (1.83 ± 0.11 g kg−1), vegetated areas (grass: 2.15± 0.18 g kg−1; reed: 2.51 ± 0.18 g kg−1) showed a higher MNC content. MNC variation was mainly related to carbon and nitrogen availability, plant biomass, clay content, and soil moisture. Our results showed that microbial properties were not essential in regulating MNC accumulation. Instead, external factors such as plant and soil properties played a more critical role in the long-term iterative process of MNC accumulation. Carbon and nitrogen availability, as regulated by plant biomass, clay content, and soil moisture, was dominant in MNC accumulation in drawdown areas. In conclusion, these findings highlight the critical role of external factors in MNC accumulation, which would enhance our understanding of MNC stability in drawdown areas. [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]

• NTDI (nonlinear trivariate drought index) performs better than single type drought indices for drought monitoring. • NTDI can effectively monitor the drought onset and duration. • NTDI shows good potential in the agricultural drought assessment. Due to the complexity of meteorological and hydrological conditions in a changing environment, previous drought indices for monitoring a specific drought type do not reflect the overall regional situation of water scarcity. Therefore, in order to obtain accurate and reliable drought monitoring, a more integrated drought index should be developed to identify drought events comprehensively. In this paper, a non-linear trivariate drought index (NTDI) was constructed based on the joint probability distribution of parametric copulas, combining precipitation (P), potential evapotranspiration (PET), and root zone soil moisture (SM) variables. Subsequently, it was respectively compared with four drought indices, SPEI, SSMI, SC-PDSI and TVDI, and cross-validated with actual recorded drought events and annual crop yield to evaluate its applicability in arid Central Asia (ACA). The results indicated that: (1) Frank copula (1-,3-month scale) and Gumbel copula (6-,12-month scale) were considered to be the best-fitted copula functions for constructing joint probability distributions in the ACA. (2) The NTDI integrated the P-PET and SM drought signals to sensitively capture drought onset and duration, reflecting the combined characteristics of meteorological and agricultural drought. (3) The drought information expressed by NTDI was generally consistent with recorded drought events, and the monitoring results are accurate. (4)The NTDI performed better in agricultural drought monitoring than other drought indices. This study provides a reliable multivariate composite indicator which is significant for drought monitoring, prevention and risk assessment in ACA. [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]

[Display omitted] • Aggregate sensitivity to slaking decreased with increasing moisture content. • Macroaggregates were harder to be disintegrated by raindrops when moisture content was 3–10 % after rainfall. • Slaking contributed more than physico-chemical dispersion to reduce splash erosion rate with increasing moisture content. • Increasing splash erosion rate with increasing moisture content were due to enhanced physico-chemical dispersion. Soil aggregate breakdown is the initial stage of splash erosion. Preventing aggregate disintegration can effectively control the material source for sediment transport. The impact factors of aggregate disintegration have been partially studied, but the effect of soil moisture content on slaking and physico-chemical dispersion remains unclear. In this study, simulation tests of splash erosion were carried out on three sandy clay loam soils with different years of vegetation restoration (S1, S2 and S3 were 55, 80 and 100 years of reforestation and land restoration, respectively). Three rainfall heights (1.5 m, 2 m and 2.5 m) were used to simulate aggregate disintegration caused by different rainfall kinetic energies. Soil aggregates with five antecedent moisture contents (air drying, 5 %, 10 %, 15 %, and 20 %) were subjected to three different pretreatments: fast wetting (FW), slow wetting (SW) and shaking after prewetting (WS). It was found that the mean weight diameter in the fast wetting (MWD FW) treatment increased and then decreased with increasing moisture content. Aggregate sensitivity to slaking decreased with increasing moisture content. After rainfall, the macroaggregates content (>0.25 mm) increased and then decreased with increasing moisture content. In the S1 sample, the contribution of physico-chemical dispersion to splash erosion was dominant for increasing splash erosion rate at the moisture content of 15–20 %. The slaking contributed more to decreasing splash erosion rate with increasing moisture content in the S2 and S3 samples. This study clarifies the response of slaking and physico-chemical dispersion to moisture content, which is helpful for thoroughly understanding the disintegration mechanisms of soil aggregates. [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]

• 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]

[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]

[Display omitted] • Slope had the most significant negative effect on soil infiltration rates. • The effect of different vegetation on soil infiltration rates was significantly different. • Soil organic carbon content increases in average infiltration rates reached 47.70 %. • Non-capillary porosity increases in average infiltration rates reached 31.00 %. High Mountain Asia (HMA) surrounding the Tibetan Plateau (TP) is a critical gathering place for water resources. Investigating soil water infiltration properties in HMA is a vital component of comprehending the hydrological cycle processes in this region. Despite some experimental studies having analyzed the soil water infiltration properties under specific conditions in HMA, a systematic quantitative anlysis of this region's soil water infiltration properties remains lacking. To investigate the effect of soil water infiltration properties under different factors in HMA, we conducted a literature review and meta-analysis based on experimental data from the literature. Our study employed the initial infiltration rate (IIR), steady infiltration rate (SIR), and average infiltration rate (AIR) as response variables to quantify the variations in soil water infiltration properties under diverse conditions. Results revealed that (1) the most significant negative effect on soil water infiltration rates was due to slope (IIR: −48.31 %, SIR: −36.87 %, AIR: −51.81 %). The subgroup analysis indicated that the negative effect of slope on the three infiltration rates was more pronounced as the slope gradient increased. (2) The positive and negative effects of different vegetation types on soil water infiltration rates were significantly different. Among them, the trees + shrub group exhibited the most prominent positive effect on IIR and SIR (IIR: +206.49 %, SIR: +153.45 %). Conversely, the widely distributed alpine meadow in HMA had a significant negative effect on IIR (−39.35 %). (3) Contrary to conventional soil infiltration experiments, the increase of initial soil moisture (SM) in HMA had a positive effect on IIR and AIR (IIR: +13.88 %, AIR: +23.37 %). Considering the study of macropore flow, this may be related to soil texture and vegetation growth. (4) As the values of each soil physicochemical property increased, there was a significant positive effect of increasing non-capillary porosity (NCP) and soil organic carbon content (SOC) on AIR (NCP: +31.00 %, SOC: +47.70 %). At the same time, we found that soil water infiltration studies in HMA are subject to spatial and quantitative limitations. Considering the importance of soil water infiltration in HMA, we recommend more comprehensive studies of soil water infiltration in HMA. Such studies would provide a vital theoretical foundation for enhancing the HMA soil infiltration model and improving the terrestrial hydrological cycle process in the region. [ABSTRACT FROM AUTHOR]