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

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

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

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

• Clarified the main controlling environmental factors of humus layer development and its influencing paths in the permafrost region. • Mapped the spatial distribution of humus layer thickness and provided the baseline information. • Revealed the change trend of humus layer thickness under warm climate. Humus has significant impacts on soil water dynamics, nutrient storage and plant growth. Studies have demonstrated that the humus layer is related to climate, soil properties, topography and other environmental factors. However, the thickness of the humus layer (HLT) and its spatial distributions are less investigated. Especially in boreal mountain forests underlain with permafrost, the environmental influences on HLT remain unclear. In a high-latitude watershed of boreal mountain forest in Northeast China, this study explores the effects of the environmental factors on HLT, and its relationships with permafrost types. The HLT distribution across the watershed is extracted using the geographically weighted regression kriging (GWRK) model. The elevation, slope, aspect, mean annual ground surface temperature and mean annual soil water content are determined to be statistically significant influencers factors of HLT. The elevation is the most important variable for HLT in this cold land, with an indirect effect on HLT through impacting ground surface temperature and soil water content. Topography casts more significant impact than ground surface temperature and soil water content. HLT ranges from 1.1 to 26.7 cm across three permafrost classes in the study area, decreasing with the discontinuity of permafrost types (continuous permafrost > sporadic permafrost > isolated patches). The findings suggest that the humus development is closely related to the permafrost type in northern high latitudes, and the permafrost degradation can lead to humus layer thinning under climate warming. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biocrust colonization increases air permeability by up to 77% • Biocrusts significantly increase saturated water content and water retention. • Air-filled porosity of biocrusts is a key factor governing air permeability. • Biocrust relative air permeability (K ra) is well captured by the standard K ra models. Soil aeration is an important factor influencing soil biological and biochemical processes because it directly affects soil microbial activity and respiration. As an important living skin of the soil, biocrusts strongly impact various soil properties and play a vital role in maintaining surface soil structure and multifunctionality. Although there are several studies concerning the effects of biocrusts on soil respiration processes, it is still not well understood how biocrusts affect air permeability (K a) and soil aeration in drylands. In a semiarid climate region of the northern Chinese Loess Plateau, the K a and air-filled porosity (ε a) of moss-dominated biocrusts established on aeolian sand and loess soil were measured as a function of soil water content under laboratory and in situ conditions and compared to measurements of bare soils. The relative air permeability (K ra) of biocrusts and bare soils was further analyzed and estimated with commonly applied K ra models that are based on the soil water retention curve (SWRC), and the performance of these models was specifically assessed for biocrusts. The in situ measurements yielded a 51.8% and 76.7% higher K a for the biocrust-colonized aeolian sand and loess soil, respectively, when compared to the bare soils. Correspondingly, in comparison to the bare soils, the ε a of the biocrusts also increased by 38.0% for the aeolian sand and by 52.4% for the loess soil. The laboratory measurements showed an 8.5%–9.3% increase of K a for the biocrust-colonized soils from wet to dry conditions when compared to their bare counterparts, which was mainly attributed to their higher fine particle and organic matter contents as well as to the moss rhizoids. Moreover, a positive linear relationship (R 2 > 0.43) was found between the log K a and log ε a for both biocrusts and bare soils. Additionally, the biocrusts exhibited higher water content at almost all matric potentials in comparison to the bare soils. The K ra of biocrusts was 22.0% higher for aeolian sand and 42.1% higher for loess soil when compared to the bare soils. The van Genuchten-Burdine and Brooks and Corey-Burdine models performed best with regard to the estimation of K ra (RMSE ≤ 0.100, bias ≤ 0.018). In general, biocrusts may greatly increase surface soil aeration due to their higher K a and ε a , and the soil aeration status of biocrusts can be indirectly assessed through their effective degree of soil water saturation. Our findings suggest that biocrusts should be carefully considered in further studies of soil aeration related to biological processes and gas and vapor transport in dryland ecosystems. [ABSTRACT FROM AUTHOR]

• High plant cover and biomass may indicate high available water content (AWC) • High AWC may stem from subsurface flow (SSF) • AWC and surface stability were examined in 5 habitats. • Plant performance (cover, number species, density and biomass) was also measured. • SSF was responsible for 2-fold higher AWC and up to 5-fold higher plant biomass. Plants in deserts exhibit heterogeneous distribution, which may stem from water redistribution following runoff. However, heterogeneous plant distribution is also common in dunefields regardless of runoff. In the Hallamish dune field in the hyper-arid Negev Desert, dense vegetation belts are noted in loci where an abrupt change in slope angles of uncrusted slopes (interface, IF) occurs, attributed to subsurface flow (SSF). While SSF was previously noted in dunefields, quantification of SSF is problematic, especially in arid regions where precipitation is low, evaporation is high, and the amount of SSF is not sufficiently large to facilitate direct measurement (in water volume). Here indirect measurements of SSF are reported based on near weekly measurements of available water content (AWC) during 2012/13, 2013/14 and 2015/16 at five slope positions along two dune catenas and the adjacent interdunes: flat semi-stable top (TOPs), flat crusted interdune (IDc), semi-stable (NFs) and crusted (NFc) north-facing slope, and IF. In addition, the hydrological rain and monthly surface stability were also measured, and additionally plant characteristics (cover, number of species, density, and biomass) were used as indicators for AWC. Higher AWC characterized the uncrusted slope positions (especially at IF) in comparison with crusted slope positions of similar slope angles. Although receiving the lowest amount of rain, AWC at IF was ∼ 2-fold higher than at most other slope positions, resulting in ∼ 3- to 5-fold higher cover and biomass, serving therefore as 'islands of fertility'. As verified by the Generalized Linear Regression Model, plant performance was mainly dictated by AWC and to a lesser degree by surface stability. Our findings may have broader implications for water redistribution in other dunefields, where a unique distribution of water has at times been attributed to factors such as the effect of biocrusts on infiltration rather than to SSF. [ABSTRACT FROM AUTHOR]

• Afforestation after long-time recovery can maintain ecosystem multifunctionality. • Positive association between species diversity and multifunctionality was exhibited. • High species richness might not maintain functions at their highest levels. Over decades, afforestation has been one of the major nature-based solutions to restore degraded ecosystems worldwide. However, a consensus on whether restoration-oriented afforestation is an effective means to maintain ecosystem multifunctionality has not yet been achieved. Here, soil and plant samples were collected among three different vegetation patterns including SH (shrub and herb species), AH (arbor and herb species), and ASH (arbor, shrub and herb species) in our study area after nearly 30 years of Robinia pseudoacacia plantation, to assess the effects of vegetation pattern on ecosystem multifunctionality evaluated comprehensively via the averaging approach and multiple threshold approach. The results showed that vegetation pattern such as ASH had a significant lower soil water content but higher total nitrogen and productivity than SH at the deep soil depth (500 cm soil profile) (P < 0.05), while they had no significant difference in soil organic carbon and total phosphorus. However, there were no significant differences among the above-mentioned five functions between AH and ASH. Additionally, the average multifunctionality index of SH was significantly lower than that of AH and ASH (P < 0.05). A strong positive association between species diversity and multifunctionality was exhibited at thresholds ranging from 22 % to 93 %, and the percentage to realize the maximum diversity effect on multifunctionality was 60 %. Moreover, the slope of the relationship between species diversity and multifunctionality decreased at higher threshold between 62 % and 93 %, indicating that high species richness might not maintain functions at their highest levels. Overall, afforestation after long-term recovery can maintain ecosystem multifunctionality quantified based on water conservation, carbon sequestration, nutrient cycling and productivity. The appropriate improvement of species diversity is conducive to sustainable forest management in a semiarid region. [ABSTRACT FROM AUTHOR]

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

• Soil δ15N and soil water content show an upward-concave relationship in the globe. • This is constituted by inconsistent relationships in different climate zone. • Positive relationship in Tropical zone due to hydrologically regulated N losses. • Negative relationship in Arid zone due to abiotic N loss and N input from bedrock. • Climate-limited low N loss lead to low soil δ15N in Temperate, Cold and Polar zones. Investigating the relationship between the natural abundance of soil nitrogen stable isotope (δ15N) and soil water content (SWC) in the globe can help to explain the different controls of soil δ15N in different regions, yet this was few concerned on. Based on the Craine et al. (2015) summarized soil δ15N data (https://doi.org/10.1038/srep08280), and the satellite retrieved SWC in 910 grids (size of 0.1° × 0.1°) of the globe, an upward-concave relationship between soil δ15N and SWC was observed. Higher soil δ15N existed at both the dry and wet ends (i.e., respectively below and above the intermediate range of SWC, which was about 0.20–0.30 m3/m−3(-|-)). Inconsistent relationships in five Köppen-Geiger climate zones constituted this upward-concave relationship. Positive relationship between soil δ15N and SWC in the Tropical zone determined the increasing trend of soil δ15N at the wet end in the globe. This can be explained by the increased hydrologically regulated soil N losses with the increase of SWC under the warm and moist condition. Negative relationship in the Arid zone determined the decreasing trend at the dry end in the globe. Increased abiotic N losses like ammonia volatilization and proportion of N supplement through bedrock weathering (higher δ15N) with the decrease of SWC under the dry, hot and infertile soil condition may be the main reasons. In addition, poor relationships between soil δ15N and SWC in the Temperate, Cold and Polar zones constituted the transition range of the upward-concave relationship in the globe. This reflected that not hydrologically but climatically determined low soil N losses was responsible for the low soil δ15N in these zones. These findings can help to deepen our understandings on the spatial pattern of soil δ15N and the indicated N cycle at the global scale. [ABSTRACT FROM AUTHOR]

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

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

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

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

• Decadal changes in soil water-holding capacity were assessed using field surveys. • Soil erosion and climate change decreased soil water-holding capacity. • The decline in soil water-holding capacity could exacerbate vegetation degradation. Environmental changes on the Tibetan Plateau could affect not only the livelihoods of local people but also the food and environmental security of downstream people. Soil water-holding capacity (WHC) governs soil functioning in ecosystems, could be significantly altered by the accelerated climate change and vegetation degradation experienced by the Tibetan Plateau's alpine ecosystem. However, it remains unclear regarding the direction and magnitude of this feedback. Here, we assessed the responses of WHC to the combined impacts of climate change and vegetation degradation across the Tibetan Plateau over the past decades based on a regional resampling campaign, including 148 well-matched sampling sites, conducted in the 1980s and 2020. We observed an overall decrease in the WHC in the study area in response to a warmer climate and increased soil erosion. The decrease in the topsoil (notably 0–20 cm) was more significant than that in the subsoil (notably 20–50 cm). Average soil available water content (AWC) decreased from 0.13 to 0.10 cm3 cm−3 (p < 0.0001) for topsoil, and from 0.10 to 0.09 cm3 cm−3 (p < 0.01) for subsoil. The changes in AWC were primarily explained by soil erosion (11.3 %) and climate change (9.2 %). Furthermore, the decline in AWC results in a significant decrease in soil productivity, which may exacerbate vegetation degradation and increase the susceptibility of alpine ecosystems to disturbances. These findings suggest that soil erosion control is still an urgent task for environmental protection on the Tibetan Plateau and that increasing WHC is an important goal of adaptation measures. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Salinity varied with time, space, topography and land use activities. • Salinity decreased with increasing distance from the coastline of the Bay of Bengal. • Polder restricts direct salinization of coastal soils. • Landsat imagery based salinity indexes can reliably predict soil salinity. • A large coastal area turned into saline in the last few decades. Salinity in soils and water of coastal tracts in Bangladesh, one of the major challenges for agriculture, varies significantly due to multiple stressors, including the consequences of rapid changes in the climate pattern. However, their dynamics has not been studied in detail accentuating its importance for the management of agriculture. Here, we examined such changes along zones - defined by spatial proximity from the seafront towards inland in the south-central coast of Bangladesh. Samples of soil and water were collected at single-month intervals between November 2020 and June 2021. In April, a comprehensive soil sampling was conducted to examine spatial variability in relation to soil type and land use. Moreover, Landsat imagery-based salinity index was calculated. Our results showed that soil and water salinity gradually increased from January onwards and peaked during May. It decreased gradually from the seafront to inland, suggesting direct and indirect intrusion of salinity from the sea. A significant non-linear relationship was found between Landsat imagery-based salinity index and measures values (r2 = 0.79, p < 0.01), indicating the Landsat imagery- based estimate could potentially be used for agriculture. Our observation also showed that salinity to soil and water was significantly low in highlands, croplands, and interior of polders as compared respectively to that of low land, fallow land, and exterior of polders. Our estimation of salinity in soil and water of the south-central coast of Bangladesh was significantly higher than that of historical records. This study, thus, would contribute to contemporary policy issues on cropland management along coastal Bangladesh. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) is a critical variable in studies of hydrological processes and the soil–plant–atmosphere continuum, especially in arid and semi-arid regions such as the Loess Plateau. Knowledge of the effects of vegetation types on soil water dynamics would aid in understanding the mechanisms responsible for water shortages and addressing the problem of poor long-term vegetation recovery. To evaluate the response of soil water storage (SWS) to different land use types during long-term natural vegetation succession, we examined soil moisture under different land use types (grassland, shrubland and forestland) at different times (2005 and 2014) in the Ziwuling forest region, located in the central part of the Loess Plateau, China. Our results showed that vegetation type had a significant effect on SWS in the 0–500 cm soil layer. The SWS in grassland and shrubland was significantly higher in August 2014 than in August 2005, but the pattern was reversed for forestland. In the same year, the SWS was highest in grassland, intermediate in shrubland, and lowest in forestland. SWS and SWC showed a highly significant and positive relationship in the 0–60 cm soil layers ( P < 0.01), and both soil bulk density (BD) and soil total nitrogen (TN) showed a significant relationship with SWS. In addition, the SWC and soil total porosity (TP) showed a significant positive relationship in the 0–20 cm soil layer ( P < 0.05). These results are expected to provide insights into land water management and inform efforts to estimate the productivity and sustainability of semiarid ecosystems. [ABSTRACT FROM AUTHOR]

Rock outcrop ecosystems, such as limestone cedar glades (LCGs), are known for their rare and endemic plant species adapted to high levels of abiotic stress. Soils in LCGs are thin (< 25 cm), soil-moisture conditions fluctuate seasonally between xeric and saturated, and summer soil temperatures commonly exceed 48 °C. The effects of these stressors on soil microbial communities (SMC) remain largely unstudied, despite the importance of SMC-plant interactions in regulating the structure and function of terrestrial ecosystems. SMC profiles and functional diversity were characterized in LCGs using community level physiological profiling (CLPP) and plate-dilution frequency assays (PDFA). Most-probable number (MPN) estimates and microbial substrate-utilization diversity (H) were positively related to soil thickness, soil organic matter (OM), soil water content, and vegetation density, and were diminished in alkaline soil relative to circumneutral soil. Soil nitrate showed no relationship to SMCs, suggesting lack of N-limitation. Canonical correlation analysis indicated strong correlations between microbial CLPP patterns and several physical and chemical properties of soil, primarily temperature at the ground surface and at 4-cm depth, and secondarily soil-water content, enabling differentiation by season. Thus, it was demonstrated that several well-described abiotic determinants of plant community structure in this ecosystem are also reflected in SMC profiles. [ABSTRACT FROM AUTHOR]

Wetlands supported by groundwater in semiarid regions are extremely vulnerable to the impacts of droughts, particularly anthropized systems. During drying periods, soil water content arises as the controlling factor for environmental and ecological disturbances such as the spread of invasive plant species, the combustibility of organic soils, nutrient redistribution or soil physical disruption. The presented management tool for semiarid wetlands is supported by the Soil-Water-Atmosphere-Plant (SWAP) model for soil moisture modeling and simulation. Main input data are experimental values of soil physical and hydraulic characteristics, soil moisture measurements, vegetation growth parameters and climatic records. Decision-makers can use the calibrated datasets to predict the evolution of soil moisture under different drying scenarios in order to choose the most efficient management options for preventing soil moisture to reach critical values. The approach has been tested in the anthropized Mediterranean semiarid wetland area of Las Tablas de Daimiel National Park in central Spain. Ten vadose zone water models were successfully calibrated and validated for different soil units. Critical soil moisture conditions for invasive reed overgrowth and peat combustibility have been estimated. Simulations of a typical 2-year drought scenario indicated that critical soil moisture conditions for reed overgrowth are attained 9–10 months after flooding ceased and that peat areas colonized by reed plants become combustible (even 50% probability chance) by the end of the simulated period. [ABSTRACT FROM AUTHOR]

Soil water repellency (SWR) has been reported under different soils, land uses and regions of the world, particularly in forest land and after wildfires, yet the understanding of this variable in agricultural lands is still rather limited. This study presents the characterization from field-based measurements of SWR in four contrasted olive groves ( Olea europaea L.) in Spain in terms of different environmental conditions and management: abandoned and commercial farms under permanent cover crop, conventional tillage and herbicide use. The main objectives were [1] to evaluate the potential occurrence, intensity and persistence of soil water repellency in different types of olive groves and [2] to explore its spatio-temporal features as well as the influence of soil properties such as organic matter (OM) and soil moisture. The Water Drop Penetration Time test (WDPT) was used in situ to assess SWR values. Measurements were carried out in two areas for each of the four groves: below and between the tree canopies. A high spatial and seasonal variability was observed. SWR was absent (WDPT = 0 s) for the olive groves under conventional tillage and with the lowest values of OM (OM-mean = 2.04%). The maximum WDPT values were found for cover crop under canopy in summer (WDPT-max = 610 s) and on the lanes in autumn (WDPT-max = 468 s). SWR was developed during the dry season, and to be reduced during the rainfall season as the organic compounds might be reoriented and turned amphiphilic. Strong water repellent values (> 60 s) were related with extremely high OM values (> 12%) for the cover crop orchard. [ABSTRACT FROM AUTHOR]

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

[Display omitted] • Fire is increasing in zone of patchy Xing'an permafrost protected by ecosystems. • Forest fire has evident influences on boreal ecosystem composition and nutrients. • Forest fire induced expansion of graminoids and tall shrubs in shrub wetlands. • Fires resulted in a massive loss of soil total carbon and nitrogen storages. • Changes in ground temperature and active layer thickness are evident after fires. In boreal regions, wildfires have a major impact on vegetation and permafrost. The ecosystem-protected Xing'an permafrost is sensitive to warming climate and wildfires, particularly on the southern margin of boreal coniferous forest and patchy permafrost zone. However, it remains unclear how fire disturbances are linked with changes in ecosystem composition and soil nutrients in the permafrost zones of Northeast China. Here, 13 years after the fire in the Yile'huli mountain knots, we investigated the parameters like vegetation cover, ground temperatures, active layer thickness, and soil carbon and nitrogen storage at burned and unburned sites of shrub wetlands. The fire resulted in ground warming of 0.1–5.0 °C at depths of 1.0–20.0 m and active layer deepening of 0.5 m, and gravimetric soil moisture content increasing of 26%-266%. Fire also increased the number of herbs and tall shrubs. After the fire, graminoids and tall shrubs increased significantly, and the species of herbs increased by five species. However, dwarf shrubs like Ledum palustre and Vaccinium uliginosum were missing from the burned site. A massive loss of total organic carbon (TOC) (248.40 t C/hm2) and nitrogen (TN) (11.87 t N/hm2) was observed by comparing their storage at burned and unburned sites. These results highlighted that the post-fire responses of vegetation cover and TOC and TN storage were dependent on the thermal regimes of near-surface permafrost and active layer, recovery of vegetation and organic layer, and soil moisture content. This study can provide an important reference for carbon storage and emission in boreal shrub wetlands under a warming climate and increasing fire disturbances. [ABSTRACT FROM AUTHOR]

[Display omitted] • Peeling soil in layers can simulate progressive thawing and detachment. • Outermost layers thawed first and were water saturated with the lowest EC. • Inner core thawed last and was driest with the greatest EC. • Progressively thawed layers differed in microbial properties and CO 2 emission rates. Freeze–thaw events can profoundly reorganise water, salts, and nutrients within the soil matrix, which consequently disturbs soil microbes and perturbs carbon metabolism. However, it remains unclear how soil microbial properties differentiate as they progressively thaw and detach from the still frozen layer as often occurs in a sloped field. In this study, a Mollisol (< 0.5 mm) was refilled into columns and frozen at −15 °C for 12 h. To simulate detachment while thawing, the frozen soil columns were progressively peeled off, from the outer to the inner core, into six layers (T1 ∼ T6). Our results show that: (1) The soil water content significantly declined from 95.3% in the outermost layer T1 to the inner core T6 of 24.7%, whilst the soil electrical conductivity evidently increased from 45.8 μS·cm−1 in the T1 to 73.7 μS·cm−1 in the T6. (2) The six frozen-thawed layers had more observed microbial species and distinct β diversity compared to the unfrozen CK, and the OTU-based co-occurrence network of the soil bacteria in the T1 was apparently better interconnected than that in the T6. However, the outer layers released significantly less CO 2 on average than the CK and inner layers over the seven days of incubation. Although cautions must be taken in extrapolating our results to field scale processes, our study was the first (to our knowledge) to distinguish the heterogeneity of soil inter-layer microbial properties during progressive thawing. Our findings collectively suggest progressive thawing may introduce a non-negligible but long-neglected heterogeneity in carbon biogeochemistry along slopes. [ABSTRACT FROM AUTHOR]

• The soil sensitivity to erosion differed depending on the erosive force applied. • Different soil properties affected the soil sensitivity for water and wind erosion. • The sensitivity of the soils to erosion was higher for wind than for water erosion. Erosion by water and wind can seriously deteriorate soil quality. Traditionally, these two types of erosion have been studied and modelled separately. The main goal of this study was to explore the sensitivity of two Mediterranean soils to both water and wind erosion, in terms of their properties and aggregation. Targeted laboratory experiments were performed using wind and rainfall simulators. Different soil properties and aggregation indices were analyzed for each soil sample. Comparing the rates of soil loss to water and wind erosion revealed an opposite trend in soil sensitivity to these erosional forces; the soil that was most sensitive to erosion by one force was least sensitive to erosion by the other force. This indicates that soil erosion is strongly dependent on the erosive force (water or wind). Therefore, soil erodibility cannot be an unequivocal definition for a certain type of soil, but rather depends on the erosional force applied. Our results also demonstrate that different soil properties affect the size and stability of soil aggregates, controlling the rate of soil loss to water erosion or wind erosion. Under rainfall simulations, the sodium adsorption ratio (SAR) was the main factor controlling soil sensitivity to water erosion (r 2 = 0.76), while loose erodible material (LEM) was the only factor controlling soil sensitivity to wind erosion (r 2 = 0.69). Since dynamic soil properties (e.g., LEM) tend to change over shorter periods of time than intrinsic soil properties (e.g., SAR), the potential for a general increase in the sensitivity of Mediterranean soils to wind erosion processes is expected to be greater than the potential for a general increase in the sensitivity of these soils to water erosion. The calculation of a sensitivity-normalized value for each soil sample revealed that the examined soils were more sensitive to wind erosion than to water erosion. [ABSTRACT FROM AUTHOR]

• Vegetation restoration enhances soil infiltrability and preferential flow. • Soil moisture and total porosity are the dominant factors affecting soil infiltrability. • Macroporosity plays a major role in influencing the degree of preferential flow. Soil infiltration plays a critical role in soil hydrological processes. Land use/cover changes are generally considered to influence soil infiltration. However, the effect of long-term vegetation restoration on the soil infiltration capacity and infiltration pattern is poorly understood. In the present study, we analyzed the infiltration capacity with a double ring infiltrometer and detected the degree of preferential flow using a dye tracer in a typical loess hilly gully catchment of China. Additionally, we identified the relationships between soil characteristics and infiltration capacity and preferential flow. The results showed that (1) converting cropland to forest, shrubland and grassland generally enhanced the soil infiltration capacity. Compared with cropland, the steady-state infiltration rate (SIR) and saturated hydraulic conductivity (K s) increased by 135 % and 155 % in shrubland, by 76 % and 91 % in forest, and by 22 % and 23 % in grassland. (2) Land use changes markedly increased the degree of preferential flow, following the order of shrubland > forest > grassland > cropland. (3) The decline in soil moisture (SM) and bulk density (BD) and the increase in total porosity (TP), macroporosity (MP) and soil organic matter (SOM) could cause higher infiltration capacity and preferential flow. SM and TP were the dominant factors affecting soil infiltrability, while MP was the greatest contributor to variations in preferential flow. Our findings demonstrated that vegetation restoration had a positive impact on soil infiltrability and preferential flow. This effect should be considered when assessing the influence of vegetation restoration on water resources in the Loess Plateau and other arid and semiarid regions. [ABSTRACT FROM AUTHOR]

• Soil infiltration and water flow paths were quantified in subtropical forest types; • Soil water infiltrability rate increased with forest succession; • The degree of soil preferential flow did not evolve along succession sequence; • Soil porosity, root systems and rocks jointly affect soil water flow patterns. Maintaining and improving the water conservation capacity of forest ecosystems is an important step in building regional ecological protection barrier. At present, there is a lack of knowledge about the patterns of soil water flow in different stages of forest succession. Therefore, this study quantified the change tendency of soil infiltration and water flow paths in subtropical different forest types, including pine forests (PF), mixed pine and broadleaf forests (MF) and monsoon evergreen broadleaf forests (BF), and analysed the effect of soil physical properties on hydraulic properties. Results showed that (1) both BF and MF were characterized by a smaller bulk density and the larger porosity than PF. (2) The saturated hydraulic conductivity of BF and MF was 2.1 times and 3.1 times higher than that of PF, respectively, showing that there were clear differences in the soil infiltrability resistance of the different forest types. The observed soil water exchange amount also showed that both BF and MF had higher water holding capacity than PF. (3) Macropore flow and lateral flow were the dominant preferential flow behaviors, but the degree of preferential flow did not evolve along succession sequence PF, MF and BF. The pattern of soil water flow was found to show obvious spatial variability, restricted by the joint influence of soil porosity, root systems and rocks. The above results suggest that soil infiltration improve with the sequence of forest succession, but that soil water flow patterns may be independent of forest succession due to the complex conditions of the soil. This study provided effective data information of forest soil hydrological antecedents. [ABSTRACT FROM AUTHOR]

• There was no significant correlation between soil fungal and bacterial a-diversity and elevation. • Soil temperature (ST), soil water content (SWC), and total phosphorus (TP) were the driving factors affecting the elevation distribution pattern of soil fungal communities. • Soil fungi were more sensitive than bacteria in response to elevation changes. • The network complexity of soil bacteria is higher than that of fungi. The Qinghai-Tibet Plateau is one of the most sensitive regions in response to global climate change. Because soil bacteria have a considerable influence on ecosystem function, it is essential to understand their responses to different climates. We investigated the effects of elevation change on soil microbial diversity and community structure in the Abies georgei var. smithii forest of the Sygera Mountains in southeastern Tibet. We sampled soils from 0 to 10 cm depth at 3500 m, 3900 m and 4300 m asl, and examined changes in fungal and bacterial communities using Illumina MiSeq sequencing. The results showed that 1) fungal and bacterial diversity (Shannon index) did not change significantly (P > 0.05) with increasing elevation, and 2) elevation had no effect on the community structure of bacteria but had a significant effect on the community structure of fungi. Redundancy analysis showed that elevation, soil temperature (ST), soil water content (SWC), and total phosphorus (TP) were drivers of changes in fungal community structure. 3) Elevation had no significant effect (P > 0.05) on the relative abundance of the dominant bacterial phylum in the soil but had a significant effect (P < 0.05) on the relative abundance of the dominant fungal phylum. The dominant bacterial phyla were Proteobacteria, Actinobacteria, Acidobacteria, and Choroflexi, whereas the dominant fungal phyla were Basidiomycota, Ascomycota and Mortierllomycota. The relative abundance of Basidiomycota at 3900 m was significantly higher (P < 0.05) than that of Ascomycota at 3500 m and 4300 m, while the relative abundance of Ascomycota at 4300 m was significantly lower (P < 0.05) than that of Basidiomycota at 3500 m and 4300 m. and 4) the complexity of the bacterial network was the lowest at 3900 m elevation, while the most complex at 3500 m elevation. The fungal network complexity was lower than that of the bacteria. In conclusion, soil fungal communities are more sensitive to changes in elevation than are bacterial communities. [ABSTRACT FROM AUTHOR]

• N addition enhanced soil N immobilization over all seasons. • N addition impacts on soil C sequestration depended upon seasons. • Factors regulating the soil C min and N min rates in response to N addition were seasonally variable. • Soil C min and N min rates became decoupled with N addition for most seasons. Elevated atmospheric N deposition can profoundly alter soil carbon (C) mineralization (C min) and nitrogen (N) mineralization (N min), which could severely impact long-term productivity of grassland ecosystem. However, little is known about how N addition, season, and their interaction affect soil C min and N min rates and their relationships by regulating soil abiotic and biotic factors. Here we investigated the seasonal variations in soil C min and N min rates and their relationship in response to multi-level N additions in a semiarid grassland in 2014–2015, and further identified direct and indirect pathways by which soil abiotic and biotic factors regulated these variations using structural equation modeling. We documented the statistically significant impacts of N addition and its interaction with season on soil C min rates. In contrast, only a significant seasonal effect on the soil N min rate was observed. Random forest analysis revealed that across all seasons, dissolved organic carbon (DOC), soil water content (SWC), catalase, urease, sucrase, microbial biomass carbon (MBC), soil organic carbon (SOC) to total nitrogen (TN) ratio, and TN were the most pivotal predictors of the soil C min rate. Comparatively, catalase, MBC, DOC, NO 3 –-N, urease, TN, NH 4 +-N, SWC, and the MBC to microbial biomass nitrogen (MBN) ratio were the most dominant drivers of the soil N min rate. SEM results indicated that the identified potential drivers that regulated the soil C min and N min rates in response to N addition varied seasonally. Additionally, N addition decoupled the soil C min and N min rates, which was a consistent relationship among most seasons. In summary, our results show that, in this semiarid grassland, current N additions can enhance soil N immobilization across all seasons; however, its impacts on soil C sequestration were seasonally variable. These findings provide evidence that season and its interactions with elevated atmospheric N deposition have important implications for the grassland biogeochemical cycling. [ABSTRACT FROM AUTHOR]

[Display omitted] • A field experiment with rock fragment content (RFC, V/V) from 0% to 75%. • Increasing RFC declined soil nutrient status. • Plants promoted certain soil nutrients and exerted disparate impacts on soil nutrient stoichiometry. • Soil nutrient stoichiometry were mainly shaped by soil structure, soil moisture and plant growth in rocky soils. Soil nutrient contents and stoichiometric ratios are determinants for soil biogeochemical cycling and functions. Variable rock fragment contents (RFC) may shape the soil nutrient status and availability in mountain ecosystems. We need to better understand how and why soil nutrients and stoichiometry shift across the RFC gradients. To investigate patterns of soil nutrient stoichiometry and underlying mechanisms in rocky soils, we conducted a field experiment involving four RFCs gradients (0%, 25%, 50% and 75%, V/V) and five vegetation treatments (four indigenous species, Artemisia vestita , Bauhinia brachycarpa , Cotinus szechuanensis and Sophora davidii , plus a non-planted treatment). Soil total carbon (C), total nitrogen (N), total phosphorus (P) and their molar ratios were measured. The contents of soil C, N and P, and C:N, C:P and N:P decreased with increasing RFC in all treatments, despite their trends were inconsistent in certain soil layers. The averages of soil N content significantly increased by 13.8% and 14.8% in C. szechuanensis and S. davidii , respectively. A. vestita and B. brachycarpa had higher soil C:N than C. szechuanensis and S. davidii. Soil nutrients and stoichiometry were positively related to soil water content (SWC) and soil capillary porosity, and negatively to bulk density and soil non-capillary porosity in all vegetation treatments, but varying relationships with biomass of plant components. These results demonstrated negative effect of RFC and discrepant effects of the plants on soil nutrients and stoichiometry. Soil structure, SWC and vegetation were the main drivers of variations in soil nutrient stoichiometry. We further concluded that soil nutrient stoichiometry in rocky soils is shaped by two influencing paths; effects of RFC on soil physical properties (SWC and soil structure) and effects of different vegetations. Our findings advance knowledge and mechanisms of soil nutrient stoichiometry in rocky soils and provide theoretical support for improving and restoring nutrient status in stony regions. [ABSTRACT FROM AUTHOR]

[Display omitted] • The CAST model well simulated the effect of fertilization practices on carbon dynamics in a chronosequence; • Free microaggregates in the Fluvaquent were the primary C sequestration fraction under RCP2.6 scenarios; • MNPK treatment promotes C storage in the study soil under current and future climates. Quantifying soil structural dynamics and aggregate turnover is important in understanding soil organic carbon (SOC) stocks, particularly over decadal and larger time scales. Until now it has remained unclear clear how soil aggregate size and its associated carbon respond to both long-term soil fertility and climate change. Here, we explore changes in soil structure and aggregate organic C (OC) stocks under different fertilization practices by combining field chronosequence SOC measurements with dynamic and process modeling in a long-term wheat-maize field experiment on the North China Plain. The fertilization practices comprise no fertilization (CK), chemical fertilization (NPK), and combined manure and NPK treatments (MNPK). The experimental measurements included the mass of OC stocks in different soil aggregate size classes. We used this information to calibrate parameters of the Carbon, Aggregation, and Structure Turnover (CAST) model and to predict future changes in aggregate structure and the resulting OC stocks using the RCP2.6 scenarios that were defined by the outputs of five future climate models from IPCC projection. With trends towards a wetter climate and increasing soil moisture under the RCP2.6 scenarios for the region, soil OC stocks will increase in all three treatments, with the strongest increase under MNPK due to exogenous C inputs. The CAST model output further suggests that changes in microaggregate (250–53 μm) OC stocks in the NPK and MNPK treatments accounted for 78.6 % and 75.3 % of the calculated change in total SOC stocks between the early and late 21st century. In conclusion, our combined data and modeling approach describes changes in soil aggregate C, identifies the primary soil aggregate size class of microaggregates involved in C sequestration in an agricultural soil, and predicts the role of Fluvaquent soils on the North China Plain as a future C sink. [ABSTRACT FROM AUTHOR]

• Soil infiltrability was differentially regulated by soil texture and plant roots. • The variations in regional soil infiltrability were more explained by soil texture. • Various root-soil combinations differentially affected regional soil infiltrability. • Soil texture had the strongest total effect on soil infiltrability on a reginal scale. Soil infiltrability controls precipitation input to soil and plays a crucial role in regulating soil eco-hydrological processes and ecosystem production in water-limited areas worldwide. The effects of root traits on soil infiltrability have been widely investigated at individual sites, but root-soil interactions and their effects on soil water infiltration over large spatial scales remain poorly understood. This study aimed to identify the unique characteristics of soil infiltration processes and different contributions of soil texture and root morphological traits to soil infiltrability. For this purpose, 153 plots of natural revegetated land with two contrasting plant species (Artemisia gmelinii Web. with tap root systems and Stipa bungeana Trin. with fibrous root systems) and bare land were selected in three regions along a texture gradient in the Loess Plateau of China. The results showed a distinct spatial variability of soil infiltration rates across the three regions with soil texture explaining the variability more strongly than plant species at several infiltration stages. Rooted soils had higher infiltration rates than bare soils, with nonsignificant inter-species difference under three soil texture types. Furthermore, soil texture and root morphological traits explained 92.03% and 74.75% of the total variance of soil properties (soil organic matter, aggregate stability, and soil porosity), and their interaction effects (73.09%), accounted for a considerable proportion. These findings suggest that soil texture and root morphological traits indirectly affect soil infiltrability by modulating soil properties, with soil texture having a higher contribution. In addition, the effects of root morphological traits on soil infiltrability were found to be dependent of soil texture on the regional scale. Therefore, the effects of soil texture and root-soil interaction deserves further attention in assessing soil hydrological processes on large spatial scales in the future. [ABSTRACT FROM AUTHOR]

• The freeze–thaw cycle affected the soil hydrological process in active layer; • There were significant differences in soil hydrothermal processes at the slope scales and profile scales; • The redistribution of soil water during the freezing and thawing periods is affected by vegetation." The Qinghai-Tibet Plateau (QTP) is a region with an extensive area of permafrost that is very sensitive to climate change. In this study, soil water and thermal dynamic processes in the active layer of the QTP permafrost area at the profile and slope scales were investigated. The results showed that the hydrothermal process in the active layer soil was strongly affected by freezing and thawing processes and external weather conditions. The temperature of the active layer fluctuated in tandem with air temperature. The soil water content was more stable during the freezing period and showed a "double-hump" trend during the thawing period. The correlation coefficient between soil and air temperature decreased with depth, from 0.896 in the surface soil layer to 0.082 in the deep soil layer; and the correlation coefficient between unfrozen water content and soil temperature during the freezing period showed an overall increasing trend with depth. The soil layers at different depths at the top and bottom of slope profiles differed in their hydrothermal processes due to the physicochemical properties and texture of the soil and vegetation types. The water-heat exchange of the surface soil is more frequent than that of the deep soil, and the frequency is more at the bottom than at the top of the slope. The soil water content at a depth of 0.25 m was the highest in the profile in association with a higher organic matter content and the blocking effect of dense roots. The changes of soil hydrothermal process in the active layer accelerated the hydrological cycle and the spatial–temporal variability in water resources in the frozen soil area. These effects might lead to a series of ecological and environmental problems, such as permafrost degradation and desertification in the QTP alpine meadow ecosystem. [ABSTRACT FROM AUTHOR]

• Soil carbon release was evaluated in a Caragana korshinskii plantation after extreme rainfall events. • Extreme rainfall changes significantly affected the soil carbon release. • Soil carbon release increases with soil depth over the period of extreme rainfall events. • Temperature sensitivity only increased at 10 cm soil depth after extreme rainfall due to the pulsed soil carbon release. • Unstable soil carbon release after extreme rainfall events can affect the soil carbon cycle. Projected increases in the frequency and magnitude of extreme rainfall events can profoundly impact terrestrial ecosystems. However, the response of soil carbon release (RS) at various depths to these events and associated regulatory processes has not been well-documented in small watersheds. We measured the mean CO 2 concentration, soil moisture (SM), and soil temperature (ST) at depths of 10, 50, and 100 cm in situ before and after extreme rainfall events between June and September 2019, in a typical small watershed of the Loess Hilly Region, China. RS, calculated using Fick's first law in one dimension, revealed the relationships between RS and extreme rainfall events. During the study period, we screened four extreme rainfall events, of which three were used. The mean RS at 10, 50, and 100 cm soil depths after extreme rainfall (post-RS) were significantly higher than those before (pro-RS) (P < 0.05). Simultaneously, decreased ST at a depth of 10 cm and increased SM at a depth of 10 cm during periods of extreme rainfall contributed to decreased RS at a depth of 10 cm. By contrast, the RS at depths of 50 and 100 cm were enhanced during periods of extreme rainfall and peaked between days two and four after the extreme rainfall events due to the significant stimulating increase in SM (P < 0.05); the relative change in RS at 50 cm soil depth was the largest. Moreover, the RS values at three soil depths were changed by extreme rainfall events (with higher SM to RS), yet the R 2 of the ST was lower after extreme rainfall. In addition, after extreme rainfall, the temperature sensitivity (Q 10) increased at a depth of 10 cm, while it decreased at depths of 50 and 100 cm. These findings imply that more CO 2 is released from deep soil in semi-arid shrubs under extreme rainfall events with sustained increase for 2–4 days. The results will help predict the impact of future climate change on regional carbon emissions and improve the accuracy of predictive model. [ABSTRACT FROM AUTHOR]

• Forestland had significantly lower soil water contents than grassland. • Different vegetation restoration types altered the soil texture. • Afforestation promoted the formation of deep roots. • Forestland did not increase SOC content in the soil profile. • Apple orchard had significantly lower MWD than the others. Vegetation restoration on the Loess Plateau has decreased soil erosion. However, the comprehensive effects of different vegetation restoration types on soil properties are not clear. Evaluating the soil properties of the main economic and ecological tree species on the Loess Plateau can provide crucial guidance for regional ecological environment restoration. Therefore, we compared soil water content (SWC), soil particle composition, root distribution, soil organic carbon (SOC) content, soil bulk density (BD), total porosity (TP), saturated hydraulic conductivity (Ks), soil water retention curves (SWRCs), and soil aggregate stability of peach (Prunus persica), walnut (Juglans regia L.), and apple (Malus pumila) orchards, black locust (Robinia pseudoacacia), and grassland of similar age on the semi-arid Loess Plateau. Forestland, especially black locust, had significantly lower SWC than grassland. The different vegetation restoration types altered the soil texture; grassland had the highest clay content, while black locust had the lowest. Afforestation promoted deep root formation, reaching>10 m, with>50 % of the roots below 2 m. Compared with grassland, forestland did not increase SOC content in the soil profile. Soil BD increased with increasing soil depth from 0 to 80 cm for the five vegetation types but was relatively stable below 80 cm; grassland had the greatest BD, while black locust had the lowest. The walnut orchard had the lowest Ks in the 0–80 cm soil layer. The apple orchard had the highest residual soil water content and field capacity. The apple orchard had significantly lower mean weight diameter (MWD) than the others, indicating low surface soil stability due to tillage management, increasing the risk of soil erosion. Overall, these results suggested that black locust had greater negative effects on soil properties than economic trees. Therefore, black locust establishment or planting density should be reduced in future vegetation restoration processes. [ABSTRACT FROM AUTHOR]

• High-frequency extreme rainfall promotes the carbon sink function of wet meadows. • Increase in extreme rainfall frequency affects soil properties and promotes CO 2 absorption. • The increase in extreme rainfall frequency increases aboveground net primary productivity. • The increase in extreme rainfall frequency decreases soil bulk density. • The CO 2 flux was affected by soil carbon components under different extreme rainfall frequency. Extreme rainfall amount and frequency can alter carbon dioxide (CO 2) exchange between the soil and vegetation in wetlands. Seasonal redistribution of extreme rainfall events is one component of a hydrological regime that affects soil water content (SWC), but its impacts on ecosystem CO 2 exchange in the Qinghai-Tibet Plateau (QTP) wetlands remain unclear. Here, we conducted field simulation experiments to understand the effects of extreme rainfall with high to low frequency once every-one, two, three, and four weeks on CO 2 exchange of wet meadow ecosystem in QTP. The ecosystem absorbed more CO 2 with high-frequency extreme rainfall (−1468.52 mg C m-2h−1) than with current natural amounts and frequency of rainfall (−1162.51 mg C m-2h−1) throughout local vegetation growing seasons. However, under low-frequency extreme rainfall (−916.72 mg C m-2h−1) the wetland absorbed less CO 2 than under natural rainfall frequency. This difference comes from the changes in net ecosystem productivity (NEP) and ecosystem respiration (ER) in wet meadows due to soil temperature (ST) and soil nutrient content. In the rapid growth stage of plants, ER and NEP exhibited single-peak curves due to increases in ST and SWC, and they reached their maximum values in August. Our results indicate that the distribution pattern of extreme rainfall events plays a critical role in regulating ecosystem CO 2 exchange in the wet meadows of the QTP. More research on the related changes between contents of soil nutrient contents and extreme rainfall events could improve the accuracy of C budget estimation in wet meadows. The predicted regional impacts of future climate extremes of rainfall will rely on changes in their frequency and timing. [ABSTRACT FROM AUTHOR]

• Soil clay and moisture mediate the decoupling of C, N and P cycling along an elevational gradient. • Total organic C pools were highest where the clay content was highest. • Soil organic N pools were controlled by clay and soil moisture effects on microbial stabilisation. • Soil P pools were not related to clay and soil moisture. • Soil organic P was decoupled from soil organic C and N pools along the hillslope. Grasslands extend across a variety of topographies including non-flat hilly areas with varied soil texture and moisture that can mediate soil biogeochemical cycling of carbon (C), nitrogen (N) and phosphorus (P). In this study we examined soil organic C, total N and P pools (both inorganic and organic), as well as gross N mineralisation (GNM, as a measure of microbial activity and N dynamics) and microbial C, N and P in winter and spring along a grassland hillslope. Our results showed that variation in soil clay and associated soil moisture were the most important mediators affecting C and N dynamics along the grassland elevational gradient. Total organic C pools were highest where the clay content was highest, likely because of the sorption capacity of clay stabilising organic matter against microbial decomposition. Likewise, the variation in soil organic N pools along the hillslope was mostly controlled by clay and soil moisture effects on microbial stabilisation of organic N. Furthermore, microbial C, N and GNM increased with increased soil moisture, suggesting that microbial activity was limited by soil moisture. In contrast, soil P pools were not related to clay and soil moisture, while soil organic P was decoupled from soil organic C and N pools along the hillslope. Possibly, differences in microbial stabilisation and mineralisation pathways (oxidation for C and N, hydrolysis for P), microbial homeostatic regulation of C, N and P, and P fixation resulted in a decoupling of P from C and N cycling in this grassland. We conclude that variation in clay and associated soil moisture along grassland hillslopes can have important but non-unidirectional effects on soil C, N and P cycling. [ABSTRACT FROM AUTHOR]

• Shrub encroachment in alpine meadows on soil pH were examined. • Shrub encroachment changed soil porosity structure of in alpine meadow. • Shrub encroachment increased soil water and salt upward transport. • Shrub encroachment increased the potential risk of salinization. Alpine meadows are undergoing shrub encroachment due to climate change and human activities, which affects the health of alpine meadow ecosystems. Previous studies mostly focused on the impact of shrub encroachment on vegetation communities, but few studies were focused on the impact of shrub encroachment on soil pH. This study shed light on this topic by measuring soil moisture and water holding capacity under different levels of shrub encroachment (shrub coverage ranging from 8% to 90%) in alpine meadows located on the Qinghai-Tibet Plateau. Results showed that the intensification of shrub encroachment increased soil saturated water content, soil capillary moisture capacity and soil field capacity, but decreased soil moisture at the uppermost soil layer (0–10 cm). The increase of soil saturated water content and soil capillary moisture capacity increased soil pH. The intensification of shrub encroachment increased soil pH at soil depth of 0–10 cm, but decreased soil pH at soil depth of 20–30 cm. Overall, shrub encroachment could increase soil water and salt upward transport by reducing soil moisture and enhancing soil capillary moisture capacity, resulting in an increase of soil pH. These findings are conducive to better understand the impact of shrub encroachment on the redistribution of soil salinity in alpine meadows, and can provide a theoretical basis for predicting the changes of alpine meadow community facing future climatic change and human activities. [ABSTRACT FROM AUTHOR]

• Trade-offs between SMC and species diversity are lowest for natural grasslands. • Species diversity of afforested land in the steppe zone is at the expense of SMC. • The SMC of afforestation lands in the forest zone can maintain existing species diversity. • The trade-offs between SMC and species diversity are balanced for the forest steppe zone. Soil moisture and plant species diversity are key factors determining the structure, function and stability of terrestrial ecosystems in arid and semiarid environments. However, the relationship between species diversity and soil moisture of different vegetation restoration measures over a precipitation gradient has not been thoroughly explored, inhibiting decision-makers' ability to formulate vegetation restoration policies. In this study, we examined the relationship between the soil moisture content (SMC) and species diversity of two vegetation restoration measures (afforested lands and natural restoration grassland) in different vegetation zones (steppe, forest-steppe and forest) on the Loess Plateau. The results showed that the species diversity of afforested lands was ranked as forest zone < forest-steppe zone < steppe zone, which contrasts with natural grasslands. The average SMC of afforested lands was ranked as steppe zone < forest-steppe zone < forest zone, and the results further indicated afforestation decreased SMC compared with the natural grassland. The relative benefit of the species diversity index in afforested land was more extensive than that of soil moisture in the steppe zone but smaller in the forest zone, and the trade-offs between soil moisture and species diversity were smallest in the forest-steppe zone but approached no trade-offs in natural grasslands. Our study suggests that although natural grassland is the ideal ecosystem across all the vegetation zones examined, the forest and forest-steppe zones are most suitable for afforestation, accounting for the human need for timber harvesting. However, afforestation plantations need to be thinned appropriately to maintain high soil moisture and species diversity and low trade-offs between soil moisture and species diversity. [ABSTRACT FROM AUTHOR]

• Root reinforcement first increases then decreases with increasing soil water content. • Root reinforcement slightly differs between wetting and drying conditions. • Roots' effectiveness for reinforcement becomes weak when soil moisture increases. • Soil moisture affects root reinforcement by altering the percentage of slipped roots. • Besides tensile strength, root failure mode is key for reinforcement estimation. Plant roots can protect soil against shallow landslides. The mechanics of rooted soil failure under varying soil water content remain poorly understood. The aim of our study was to characterize the impact of soil water content on root mechanical traits and reinforcement to soil. One-year-old Symplocos setchuensis trees were replanted in shear boxes (0.4 × 0.4 × 0.5 m3), which were placed in a canopy gap on Jinyun Mountain, Chongqing, China. After three years of vegetation growth, root mechanical measurements and soil direct shear tests were performed at five levels of volumetric soil water content varying from 14.9 to 44.4 %, by either wetting or drying the soil. For each shear box, we measured soil shear strength, root area ratio, root tensile force, root water content, and root failure mode (slippage versus breakage) during or after the shearing process. Root area ratio and root failure modes were examined for different root diameter classes. With increasing volumetric soil water content, we found a persistent decrease in root tensile strength (ca. 15 %) and an increase in root water content (ca. 11 %), although the dependence on volumetric soil water content was not statistically significant for certain soil water content levels. We found that both additional shear strength of rooted soil and proportion of root failure in breakage increased first and then decreased, with peak values occurring at a soil water content of ca. 22 %. Altered root tensile force (68.0 % contribution to root reinforcement variation) and the change in proportion of root failure modes (breakage or slippage; 8.4 % contribution to root reinforcement variation) jointly contribute to the negative impact of soil water on observed root reinforcement. Soil shear strength was positively correlated with root area ratio and their relationship was linear. At high soil water content (>28 %), the slope of the linear relationship decreased rapidly with increasing soil water content, suggesting that increasing root biomass is not effective for enhancing root reinforcement in very wet soil conditions. Regarding hysteresis, root reinforcement magnitude and efficiency were higher in the drying process than in the wetting process when soil moisture was low. Our results highlight the vital role of soil water features in affecting soil-root mechanical interactions and such effects should be taken into account in future root reinforcement modelling and assessment [ABSTRACT FROM AUTHOR]

Plant litter can be incorporated into topsoil under natural circumstances by soil splash, sediment deposition, and soil-dwelling animal activities. The incorporated litter can change the mechanical properties of soil and the decomposition of the incorporated litter can improve soil structural stability. Those changes likely influence soil detachment process by overland flow. This study was undertaken to quantify the effects of incorporated plant litters into topsoil on the temporal variation in soil resistance to detachment by overland flow using natural soil samples collected from four different plots (one control and three litter incorporation treatments) and then scoured under six different flow shear stresses in a hydraulic flume. The experiment started from April 19 to October 5, 2015 for 10 times at approximately 20 days sampling intervals. Soil properties and environmental parameters were also measured at each sampling time to explain the temporal variations in rill erodibility and critical shear stress. The results showed that the incorporated plant litter was effective to enhance soil resistance to flowing water erosion. Compared to bare soil, rill erodibilities of litter incorporated soils of black locust, sea buckthorn, and green bristle grass decreased by 24.3%, 33.5%, and 34.8%. The temporal variations in rill erodibility of bare and litter incorporated soils were similar. Rill erodibility decreased significantly over time as an exponential function for both bare and litter incorporated soils. The relative rill erodibility of three litter incorporated soils increased over time as a power function. The fitted critical shear stress increased exponentially over time. The temporal variations in rill erodibility could be explained by the temporal variations in soil consolidation, water stable aggregate, and litter decomposition. Rill erodibility could be well estimated by soil bulk density, water stable aggregate, and litter mass density ( r 2 = 0.92). [ABSTRACT FROM AUTHOR]

Drylands are important ecosystems that are facing severe challenges under a changing climate. The relationships between soil moisture and vegetation have garnered international interest because of their significant impact on ecosystem restoration in semi-arid and arid regions. Grasslands are among the largest ecosystems in the world and are very important to dryland ecosystems. The Loess Plateau in China is an important example of drylands, and grasslands occupy more than 1/3 of its area. Water is the primary limiting factor of vegetation restoration, so understanding the relationship between grasslands and soil moisture on the Loess Plateau is imperative. The processes of precipitation, soil surface infiltration and evaporation, root water uptake and leaf transpiration are important for the relationship between grasslands and soil moisture. This paper found the following research topics that were related to the Loess Plateau based on 283 references of local studies from CNKI, ScienceDirect and Springer: (1) the effects of grasslands on soil moisture, including the influence of precipitation, geography, grassland type, grass age and growth stage on soil moisture and soil moisture determination methods; (2) the influence of soil moisture on grasslands, including the influence of soil moisture stress on grass growth and the methods for determining the physiological and ecological characteristics of grass; and (3) models of the relationships between grasslands and soil moisture. International references were used to explain certain processes and were compared with studies on Loess Plateau. Existing studies on the Loess Plateau paid more attention to these phenomena compared to water transport processes. Additional process-based studies with greater accuracy, longer time series, and larger spatial scales are needed to achieve ecosystem sustainability on the Loess Plateau. This summary of studies on the Loess Plateau may provide examples for research on arid and semi-arid areas in other countries. [ABSTRACT FROM AUTHOR]

Water erosion is the main cause of soil degradation on cultivated lands under Mediterranean climate. In these conditions, ephemeral gully erosion (EGE) is a major contributor to loss of soil productivity due to the big amounts of soil removed from the most productive top-layer. However, only a few studies on the effects of EGE and artificial controlling measures on soil degradation are available. The objective of this study was to assess the impact of EGE combined with soil infilling by tillage on several physicochemical soil properties related to soil fertility and productivity through the calculation of a soil quality index (SQI) by means of a statistical approach. It was hypothesized that the sites affected by this process of erosion and infilling of ephemeral gullies (EGs) exhibit considerable changes in the soil properties compared with locations that do not undergo this process. The study site consisted of 5 fields with contrasting soil properties which have been continuously cultivated with winter wheat. The site, located in the internal area of Sicily (Italy), represented a typical Mediterranean arable land and was severely affected by EGE. A set of soil samples were collected to investigate the spatial variation of the SQI across each location: 12 sample points in the EGE area; 4 samples in the deposition zone; 4 reference points in the area unaffected by EGE. The SQI was estimated by closely monitoring a set of main chemical and physical soil variables which influence soil fertility status: particle size (sand, silt and clay content), bulk density, gravimetric moisture, pH, electrical conductivity, carbon content (inorganic, organic and total), nitrogen content (ammonium, nitrate and total) and available phosphorus. The results showed that channelized erosion posed a threat to soil quality status even at a single cultivated field's level; therefore, the soil's ability to sustain crop production is expected to be compromised in the long run. Reductions of the SQI were observed at the EGs system area and at the deposition area in every EGs. Besides that, the lowest values of SQI were obtained inside the EGs channel and in the nearby soil areas, which were generally used to fill those channels. Soil degradation occurred in the areas which were subjected to EGE and infilling process, with key soil properties being clay (CC), sand (SaC), silt (SiC), and total organic carbon (TOC) contents. This approach helps to understand the impacts of EGE and its controlling measures on soil degradation in Mediterranean agricultural fields. [ABSTRACT FROM AUTHOR]

The shrub patch pattern has important influence on the ecosystems in the arid water-wind erosion crisscross regions. The objective of this study was to examine the effects of vegetation pattern of shrub spot patch on species diversity and soil water content at the sand in slopes in water-wind erosion crisscross region on the Loess Plateau. In this study, the shrub patch size was classified to four size classes, contrasting with bare land patch, and herbaceous plants, and soil water content of the shrub patch were measured in each patch. The Shannon–Wiener indices were 0.364 and 1.074 respectively in small and large patches, which were higher than 0.231 in the bare land patch. The Richness index was 1.41 in bare land patch, which was lower than 1.704 in small shrub patch and 4.370 in large shrub patch. The above- and below-ground biomass and surface soil water content were also significantly ( p < 0.05) higher in the shrub patch than that in the bare land patch. These results suggest that the shrub patch could significantly increased species diversity, the above- and below-ground biomass, and surface soil water content. Based on these results, the soil was aggregated in shrub patch and the vegetation pattern was successive and each cycle of vegetation pattern was benefited by its previous stage in the water-wind erosion crisscross region on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Decreases in the water retention function of various artificial disturbed landform units (DLUs) caused by urbanization activities, compared to original landform units (OLUs), are the main factor that causes urban water and soil loss and the aggravation of urban floods under certain rainfall conditions and specially designed drainage network capabilities. Field investigations, laboratorial analyses of soil physical properties and analytic hierarchy process (AHP) composite methods were performed to comprehensively analyse the effects of various DLUs on the water retention function of OLUs. The results indicated as the following: (і) The > 5 mm particle content (> 54%) for various DLUs was higher than that for OLUs (lower than 3%); the natural repose angles of soil-rock mixtures (32–37°) and soil bulk density (1.41–1.74 g/cm 3 ) in the DLUs were all higher than those in the OLUs (30–31°, 1.18–1.14 g/cm 3 ); and the uniformity coefficients and curvature coefficients were 10.00–80.00 and 3.24–5.70 in the DLUs and 6.00–75.00 and 0.17–2.50 in the OLUs, respectively. (ii) The soil steady state infiltration rate in the DLUs decreased from disturbed soil accumulation with 2 months (DSA 2m , 15.00 mm/min) to disturbed soil accumulation with 2 years (DSA 2a , 5.63 mm/min), disturbed soil accumulation with 4 years (DSA 4a , 3.82 mm/min), the slope greening belt (SGB, 1.24 mm/min), and construction roads (CR, 0.51 mm/min). The conversion from forests to DSA 2m had the greatest impact on the soil infiltration capacity and soil storage capacity, while the conversion to CR had the lowest impact. (iii) The total reservoir storage in the DLUs' soil was ordered as follows: DSA 4a > SGB > DSA 2a > DSA 2m > CR. The conversion process from grass to CR exerted the greatest impact on storing water and regulating the overland flow. (iv) The water retention functions in the DLUs were all weaker than those in the OLUs: DSA 2m was the weakest (0.287), while paddy fields were the strongest (0.668). Thus, the occupied areas of urban water surfaces (e.g., lakes, rivers and ponds), forests and grassland and their spatial distribution during urbanization must be carefully considered. These results could help to understand the ecological service functions of urban soil and water conservation, provide relevant knowledge to landscape rehabilitation, alleviate urban floods during urban development and recover the functions of soil and water conservation ecological services in project areas during the urbanization construction process. [ABSTRACT FROM AUTHOR]

In this study eight temperate grassland sites were monitored for soil CO 2 efflux (R s ) and the spatial covariate soil water content (SWC) and soil temperature (T s ) at fine scale in over 77 measurement campaigns. The goals of this multisite study were to explore the correlations between environmental gradients and spatial patterns of R s , SWC and T s , which are not site-specific and to quantify the relevance of biotic and abiotic controls over spatial patterns along increasing vegetation structural complexity. These patterns in water-limited ecosystems in East-Central Europe are likely to be influenced by summer droughts caused by the changing climate. A consistent experimental setup was applied at the study sites including 75 sampling locations along 15 m circular transects. Spatial data processing was mainly based on variography. Two proxy variables were introduced to relate the site characteristics in terms of soils, water status and vegetation. Normalised SWC (SWCn) reconciled site-specific soil water regimes while normalised day of year integrated temperature and vegetation phenology. A principal component analysis revealed that the progressing closure of vegetation in combination with large R s and SWCn values, as well as low T s and R s variability support the detectability of spatial patterns found in both the abiotic and biotic variables. Our results showed that apart from SWC the pattern of soil temperature also had an effect on spatial structures. We detected that when the spatially structured variability of T s was low, a strong negative correlation existed between SWCn and the spatial autocorrelation length of R s with r = 0.66 (p < 0.001). However, for high spatially structured variability of T s , occurring presumably at low T s in spring and autumn, the correlation did not exist and it was difficult to quantify the spatial autocorrelation of R s . Our results are indicative of a potential shift from homogeneity and dominance of biotic processes to an increased heterogeneity and abiotic regulation in drought prone ecosystems under conditions of decreasing soil moisture. [ABSTRACT FROM AUTHOR]

Soil microbial communities play an important role in regulating land–atmosphere CO 2 exchange in terrestrial ecosystems. However, their responses to climate change are unclear. We explored the effects of water and nitrogen addition and their interaction on soil microbes and the resulting impacts on soil carbon emissions in the Gurbantunggut Desert, northwestern China. A manipulative 30% increase in precipitation and 5 gN m − 2 year − 1 deposition alone and in combination was applied across three years from 2011 to 2013. Water addition significantly increased microbial biomass and respiration, metabolic quotient, and the utilization of carbohydrates, carboxylic acids and amino acids. Water addition did not change the microbial community composition. Nitrogen addition only significantly increased soil bacterial PLFAs, while exerting no significant impacts on soil fungal PLFAs, microbial respiration and soil respiration. Moreover, nitrogen addition had no significant impacts on microbial community composition. Water and nitrogen addition in combination did not generate synergistic effects on microbial communities and soil respiration. Across treatments in three years, soil respiration and microbial respiration were positively correlated with microbial total PLFAs, microbial carbon utilization profiles, while being independent of microbial community structure. This study suggests water addition can increase soil carbon emission through increasing microbial utilization of labile carbon, and water plus nitrogen addition had no synergistic effects on soil microbial communities and soil respiration, demonstrating nitrogen is not a limiting factor for soil microbial communities in the scenario of increasing precipitation in this desert ecosystem. [ABSTRACT FROM AUTHOR]

The objective of this study was to explore the correlations between Tamarix and soil water salinity parameters and groundwater depth under saline mineralization conditions and to reveal the transport rules and exchange effects of salinity in soil- Tamarix systems with different groundwater depths. Soil columns planted with Tamarix chinensis ( T. -soil column) grown in the Yellow River Delta were chosen for modeling. Six different groundwater depths were simulated in the models. We measured and analyzed the water and salinity contents of different soil profiles with different groundwater levels and Na + contents in new T. chinensis branches and leaves. The results showed the following: (1) under shallow and medium groundwater levels, with increasing soil depth, the differences in the water contents between the T.- soil column and the control soil layer gradually decreased. Under deep groundwater levels, the differences increased and then decreased. Planting T. chinensis decreased the soil water content, and higher groundwater levels corresponded with a greater decrease in the soil water content of the T.- soil column. With increasing groundwater depth, the depth at which the water content of the T.- soil column suddenly changed increased. When the groundwater levels were 0.6 m, 0.9 m, 1.2 m, 1.5 m, and 1.8 m, the critical depths at which the water contents suddenly changed in the T.- soil columns and control were 0.3 m, 0.5 m, 0.7 m, 1.0 m, and 1.3 m, respectively. (2) Although planting T. chinensis clearly decreased soil salinity, the amplitude of the decrease increased and then decreased with increasing groundwater depth. The maximum decrease was reached at a groundwater level of 1.2 m. Importantly, the groundwater level of 1.2 m was the critical level for increasing the capillary water in the T.- soil column and was the depth at which the water and salinity significantly changed (the water and salinity turning depths). When the groundwater depths were 0.6, 0.9, 1.2, 1.5 and 1.8 m, the water turning depths in the T.- soil columns and control were 0.3, 0.5, 0.7, 0.7 and 0.7 m, respectively. Under medium (0.9 m and 1.2 m) and deep (1.5 m and 1.8 m) groundwater depths, the minimum soil salinities in the T.- soil column occurred at depths of 0.5 m, 0.7 m, 0.7 m, and 1.0 m, respectively. (3) With increasing groundwater depth, the water contents of the T.- soil column, T. chinensis leaves, and new branches gradually decreased. The salinity of the T. chinensis leaves decreased and then increased, and the salinities of the T.- soil column and new branches increased and then decreased. Under different groundwater depths, the water contents of the T. chinensis leaves were significantly higher than the water contents of the branches, and the salinity contents of the leaves were significantly lower than the salinity contents of the branches. With increasing groundwater depth, the water transported from the branches to leaves of T. chinensis significantly increased, and the ratio of Na + that migrated decreased and then increased. [ABSTRACT FROM AUTHOR]

Soil water erosion on cultivated lands represents a severe threat to soil resources in the world, and especially in Mediterranean areas, due to their topographic, edaphic and climatic conditions. Among the cultivated lands, vineyards deserve a particular attention because, aside representing one of the most important crops in terms of income and employment, they also have proven to be the form of agricultural use that causes one of the highest soil losses. Although the topic of soil water erosion on vineyards has been studied, it still raises uncertainties, due to the high variability of procedures for data acquisition, which consists into different scales of analysis and measurement methods. There is still a great gap in knowledge about the effect of triggering factors on soil water erosion and, so far, an effort to quantify this effect on the Mediterranean viticulture has not been made yet. Therefore, this paper review aims to (i) develop a documented database on splash, sheet and rill erosion rates in Mediterranean vineyards, (ii) identify and, if possible, quantify the effect of triggering factors such as topography, soil properties, rainfall characteristics and soil conservation techniques on soil water erosion, and (iii) provide suggestions for a more sustainable viticulture. Although the large variability of data, some general trends between erosion rates and triggering factors could be found, as long as data were categorized according to the same measurement method. However, no general rule upon which to consider one triggering factor always predominant over the others came out. This paper review supports the importance of monitoring soil water erosion by field measurements to better understand the relationship between the factors. However, protocols should be established for standardizing the procedure of collecting data and reporting results to enable data comparison among different study areas. [ABSTRACT FROM AUTHOR]

Surface and groundwaters of El Divisorio brook (Argentina) have excessive As (WHO, USEPA, CAA: > 10 μg L − 1 ). The rural population is at risk of arsenicism because groundwater is the only source of water for human consumption. We analyse geoavailability of As and other associated elements (Ba, Br, Co, Cr, Fe and Na) in the solid phase (INAA-Actlabs), determine the association between As and other elements in the mineral suite and in waters, quantify Fe oxides (Fe ox ; Mehra and Jackson) and interpret their relationship with As, total Fe (Fe total ) and Na in the solid phase applying Principal Components (PC) to understand factors and processes that rule their incorporation into groundwaters and to identify areas at risk of elevated As in waters. Intrabasin variability of total As content (range 5.80–20.70 mg kg − 1 ) with the highest amounts towards the discharge areas and a more irregular vertical distribution, particularly in the alluvial plain, reflects differences in As-bearer frequencies. Arsenic is slightly lower in the Bw horizons compared with the A and C horizons and it increases in the Bt horizon through clay illuviation. More than 90% of sodium-bicarbonated surface and groundwaters showed As > 10 μg L − 1 (range: 10 to 114 μg L − 1 ) with the highest levels in the middle–lower basin. The highest contributions to PC1 were Br (0.673), Co (0.868) and Na (− 0.769); As (0.814) and Cr (0.686) were relevant to PC2 and Ba (0.501) and Fe (0.783) were relevant to PC3. In the upper basin, a greater amount of Na withheld in the solids promotes a less aggressive geochemical environment and prevents As from entering waters, thus yielding lower As levels in the aquifer compared with the middle–lower basin. Here, alkalinity (pH: 7 up to > 9) promotes weathering and liberation of As from volcanic glass and other carriers, formation of As oxyanion species together with As desorption from charged clays and Al–Fe–Mn sesquioxides and concentration up to unacceptable levels in solution. Landform configuration, climate and pedoclimate, the residence time of water and the local hydrogeochemical variables (pH, competition with other ions, adsorption–desorption) control mobility and concentration of As in a dynamic equilibrium with the local chemistry. Evaporation (subhumid to semiarid climate) and oxyion competition reinforce As accumulation in the shallow aquifers. [ABSTRACT FROM AUTHOR]