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

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

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

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

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

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

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

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

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

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

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

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

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

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

[Display omitted] • SBAS-InSAR is used to monitoring the wind erosion of lake basin. • Subsidence of up to 100 mm was observed during the period from 2015 to 2018. • Wind speed and soil moisture content are the primary factors driving the seasonal variations in wind erosion. • Water bodies and vegetation play a significant inhibitory role in wind erosion. In arid regions, terminal lakes play a crucial role in maintaining the local ecological environment. However, due to the impact of climate change and human activities, terminal lakes are prone to shrinkage and drying up. The exposed lakebeds became new sources of sand and dust, leading to severe land degradation. This study extracted the water surface area of the Chaiwopu Lake in Urumqi and calculated the fractional vegetation cover (FVC) in the surrounding areas based on Landsat images from 2000 to 2022. The changes in FVC and lake area before and after the implementation of the policies on fallow and groundwater extraction restriction in 2014 were analyzed. Using the SBAS-InSAR method, the surface deformation during the period of minimum lake area from 2014 to 2018 was estimated, and the process of wind erosion and accumulation in the dried lake basin was analyzed. The results showed that from 2011 to 2014, Chaiwopu Lake experienced rapid shrinkage, and the lake almost disappeared. After 2014, the lake rapidly recovered, reaching 70% of its original area by 2021. With the recovery of the lake, the vegetation coverage in the surrounding area has changed from decreasing to increasing. During the period of lake shrinkage, the dried lake basin experienced severe wind erosion, with the maximum erosion rate exceeding 40 mm/year. The sand and dust from the dried lake basin accumulated around the lake under the influence of wind, further accelerating land degradation in the surrounding areas. After 2021, the restored lake and wetland surface covered the once-dry lake basin again, and the largest dust source in the region nearly disappeared. The study results indicated that the restoration of the lake and surrounding vegetation can eliminate the sources of sand and dust and prevent their transportation, effectively preventing land desertification. [ABSTRACT FROM AUTHOR]

• Four model slopes were constructed to study the soil water distribution. • The vegetation considerably reduced the similarity of spatial distribution pattern of soil water. • The spatial distribution pattern of the soil water under grass cover tended to be more stable. • The proposed weight-based prediction method accurately estimated the soil water status. The temporal stability of soil water is a critical state variable affecting hydrological process and structural stability of slopes. In this study, the effect of vegetation on the spatiotemporal characteristics of soil water content (SWC) was assessed via temporal stability analysis. Three types of re-vegetated slopes (grass, shrub, and grass-shrub) were constructed to explore the spatiotemporal distribution of the SWC at depths of 0–100 cm. Then, the effects of different vegetation covers on the SWC were explored. The coefficient of variation, the Spearman rank correlation coefficient, the mean relative difference, and the index of temporal stability were utilized to demonstrate the temporal stability of the SWC. Finally, a method of estimating the soil water status of re-vegetated slopes based on representative locations was developed. The results revealed that soil water dynamics were considerably governed by vegetation and rainfall. The vegetation cover considerably reduced the similarity of the spatial distribution pattern of the soil water, which tended to be more stable under grass cover. The weight-based prediction method developed in this study can more accurately estimate the overall soil water state of re-vegetated slopes. It provides a theoretical basis for the reasonable layout of SWC monitoring points and guidance for the ecological restoration of engineering slopes. [ABSTRACT FROM AUTHOR]

• Land-use types, seasons, slope position significantly affected SOC and SWC. • Revegetation increased SWS consumption and SOC accumulation. • There was a positive linear relationship between SOC and SWC. • Planting grass and shrubs is recommended in the semi-arid hilly and gully regions. Understanding the response of soil organic carbon (SOC) and moisture to different land-use types, slope positions, seasonal variations, and their interactions has great significance for land use and management. However, the coupling effects of SOC and soil moisture in typical hilly and gully regions are still elusive. Therefore, in this study, five different land-use types, including cropland, abandoned land, grassland, shrubland, and forestland were selected in a typical Chinese loess hilly-gully region, and soil samples were collected from 0 to 200 cm profiles at the upper, middle, and lower slope positions in four seasons. The results demonstrated that the distributions of SOC and soil moisture were jointly significantly affected by land-use types, seasons, and slope positions (P < 0.01). Average SOC content was found to be highest in the shrubland, followed by grassland, abandoned land, forestland, and cropland. SOC storage at the lower slope position was 10.97% higher than that at the upper slope position. SOC storage in winter was 45.47% higher than that in summer. SOC storages of abandoned land, grassland, shrubland, and forestland were 17.38%, 33.08%, 52.52% and 1.26% more than that of cropland, respectively. Soil moisture fluctuated greatly in 0–100 cm layers and was stable beneath the 100 cm layers, which was highest in autumn, and lowest in summer. Whereas, under different land-use types, the soil moisture of cropland was the highest, especially significantly higher than all revegetated treatments in the 60–200 cm soil layers. Compared with cropland, soil water storage at other land-use types was averagely 36.45 % lower in the entire 200 cm soil profile. SOC was positively correlated with soil moisture under different factors. Thus, we recommend planting shrub and grass in watersheds with serious soil erosion in the semi-arid hilly and gully region, because they can sequestrate more SOC and retain more soil water. [ABSTRACT FROM AUTHOR]

• Shrub encroachment and severe degradation reduced Cyperaceae coverage and root biomass. • Shrub encroachment and severe degradation significantly increased soil non-capillary porosity. • Reduction of Cyperaceae spp. and increase of non-capillary porosity increased infiltration rate. • The two divergent successions both increased cumulative infiltration and evapotranspiration. • Short-term grazing exclusion presented little effect on soil infiltration rate. Alpine meadow ecosystem are undergoing the divergent successions under the influence of global climate warming and overgrazing by herbivores, which may profoundly impact the ecohydrology function of alpine meadow ecosystem. However, few studies reported the effects of the divergent successions on ecohydrological process of alpine meadow. Here, we report an in situ experiment to examine the effects of the divergent successions on soil pore structure, infiltration rate and evapotranspiration of the two types of divergent-succession meadows (the shrub-encroached meadow and the severely degraded meadow), compared to the normal alpine meadow. Results showed that both the shrub-encroached meadow and the severely degraded meadow significantly reduced the dominant Kobresia spp. (Cyperaceae family) coverage, soil compactness, and belowground biomass, but significantly increased soil non-capillary porosity (P < 0.05) compared to the normal alpine meadow. Soil infiltration rate was significantly negatively correlated with Kobresia spp. coverage, soil compactness and belowground biomass, while significantly positively correlated with soil non-capillary porosity (P < 0.05). Therefore, the shrub-encroached meadow and the severely degraded meadow increased soil infiltration rates not only by reducing the dominated Kobresia spp. (Cyperaceae family) coverage and belowground biomass, but also by increasing soil non-capillary porosity. Compared with the normal alpine meadow, the cumulative infiltration and evapotranspiration increased by 245.25% and 45.19% in the shrub-encroached meadows, and increased by 208.23% and 29.95% in the severely degraded meadow. However, short-term grazing exclusion presented little effect on soil infiltration rate in alpine meadows. Overall, the divergent successions of alpine meadows had a greater impact on soil water replenishment and evapotranspiration than the short-term grazing exclusion. These findings can help to better understand the impacts of the divergent community succession on the ecohydrological process in alpine grassland ecosystem. [ABSTRACT FROM AUTHOR]

• The diversity of microbial community increased as the distance from the MTL decreases. • The diversity of microbial community decreased as the distance from the DTL decreases. • Abundances of most genes related to C decomposition were low in the near lakeside areas. • The soil water content had nonlinear effects on the microbial α-diversity. Thermokarst lakes are widely distributed across the Qinghai-Tibet Plateau (QTP) and have been identified as an important source of greenhouse gases. However, previous studies on soil microbes have mainly focused on the aquatic area of thermokarst lakes, and the changes in microbial communities in the terrestrial area around thermokarst lakes are still unclear. We used high-throughput sequencing to analyse the soil microbial communities in the sediment and terrestrial area around three thermokarst lakes on the QTP. The results showed that the relative abundances of Bacteroidetes and Proteobacteria were high in the sediment areas, while the relative abundances of Actinobacteria and Acidobacteria were high in the terrestrial area around the thermokarst lakes. As the distance from the thermokarst lakes decreases, the α-diversity of the microbial communities increased in the mature thermokarst lake (MTL), whereas the α-diversity of the microbial communities decreased in the developing thermokarst lake (DTL). The β-diversity of the microbial communities also varied significantly as the distance from the thermokarst lakes decreases. As the distance from the thermokarst lakes decreases, the abundances of most genes responsible for C decomposition decreased in the MTL and were high in the middle lakeside areas and sediment of the DTL. Soil organic carbon (SOC), total nitrogen (TN), pH, soil water content (SWC) and the pore equivalent diameter were critical factors that affected the microbial community. The microbial richness increased in relatively arid areas (SWC < 60%) and decreased in relatively humid areas (SWC > 60%) as the distance from the thermokarst lakes decreases. These results suggest that the potential C decomposition was high in the far lakeside areas of the MTL and was high in the middle lakeside areas and sediment of the DTL. [ABSTRACT FROM AUTHOR]

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

• In-situ tests in five sands with different vegetation coverages and types. • Deep percolation (DP) directly measured by a DP recorder. • DP in mobile sand more sensitive to rainfalls of > 10 mm and high-intensity. • Increases in vegetation coverages and forest selection reduced DP and soil water. Deep percolation (DP) determines the sustainable utilization of regional groundwater resources and provides large hydrological benefits to ecosystems in semiarid sandy regions. However, studies involving DP variability have rarely conducted in-situ tests with different vegetation coverages (VC) and vegetation types using direct measurements. This study measured soil moisture and DP for four years in five plots, with DP measured using a deep percolation recorder: mobile sand (MS) as the control group; Artemisia ordosica semifixed (AOSF) with VC of 30%–35% and Artemisia ordosica fixed (AOF) with VC of 70%–75% (AOSF and AOF stand ages: 30–40 years), representing different vegetation coverages; and Salix psammophila fixed (SPF) and Pinus sylvestrix var. Mongolica fixed (PSMF) with the same VC of 45%–50% (SPF and PSMF stand ages: 30 years), representing different vegetation types. The effects of sand-fixing vegetation on DP and soil water were evaluated using the relative extractable soil water (RESW) and soil water storage deficit metrics. DP occurrence in MS was closely related to rainfall amounts of > 10 mm and high-intensity rainfall rather than the total annual rainfall. Increases in vegetation coverages and forest selection significantly reduced DP and RESW compared with MS. DP in the shrub plot (SPF) was significantly higher than that in the forest plot (PSMF). Plants utilized water from different sources among the sandy land types: the shallow (0–80 cm) and deep layers (80–200 cm) in PSMF and AOF, and only from the shallow layer in AOSF and SPF. However, compared with MS, soil water storage deficit occurred to varying degrees in each plot. This study can provide a scientific reference for the restoration of the ecology and water cycle in sandy regions. [ABSTRACT FROM AUTHOR]

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

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

[Display omitted] • Fe p concentration and Fe complexing index decreased after plant invasion. • Fe-OC concentration decreased by 35.9% in average after plant invasion. • FeRB abundance significantly increased by 78.6% after plant invasion. • Plant invasion increased soil water content and decreased bulk density. • Fe-OC was positively correlated with SOC, Fe p , and Fe(III). Wetland ecosystems have dual functions as both carbon (C) sources and C sinks, playing a vital role in the world's C budget. Wetlands are prone to suffer from plant invasions, and for example, Spartina alterniflora , a well-known invasive species, has rapidly expanded in coastal areas of Asia since 1979 and altered the C cycles in coastal wetland ecosystems. Fe(III) oxides are critical in the OC storage by formation of Fe-bound organic carbon (Fe-OC). But the impact of the invasion by S. alterniflora in coastal wetlands on the formation and stabilization of Fe-OC is poorly known. Herein, we assessed soil Fe species contents, Fe-OC pool, and the microbial communities associated with these processes in seven wetlands dominated by both native ( Kandelia obovate , Avicennia marina and Phragmites australis) and invasive (S. alterniflora) plants. Our results showed that organical complexed Fe (Fe p) concentration and Fe complexing index under S. alterniflora community were lower than that under native communities. Soil Fe-OC concentration and molar OC:Fe ratio decreased (35.9% and 29.3%, respectively) after S. alterniflora invasion in coastal wetlands, while the abundance of FeRB increased by 78.6%. The invasion of S. alterniflora increased soil water content while decreased bulk density, and these changes could have important effects on Fe species and FeRB abundance. Moreover, Fe-OC was positive correlated with soil organic carbon (SOC), Fe p , and Fe(III), indicating that SOC and Fe(III) concentrations directly affect the formation of Fe-OC. FeRB reacted on the combination of Fe (hydr-) oxides and SOC to indirectly affect Fe-OC through dissimilatory Fe reduction, which further determined the stabilization and mineralization of SOC. Taken together, the invasion of S. alterniflora hindered the generation and accumulation of soil Fe-OC pool weakening the stabilization of SOC in coastal wetlands. Therefore, the conservation and restoration of mangroves and other coastal wetlands provide a promising strategy for SOC sequestration and climate change mitigation. [ABSTRACT FROM AUTHOR]

• Catenary soils are still formed on karst hillslopes composed of pure dolomite rock. • The fundamental control on dolomite hillslope soil loss is the soil type. • The lack of large fissures in the dolomitic weathering crust results in no significant underground soil loss. Dolomite hillslopes are highly vulnerable to rocky desertification, but the linkages among soil type, runoff mechanisms, and soil erosion remain unclear. During four hydrological years (2018–2021), soil type, plot-scale hydrological and erosion behavior at the upper, middle, and lower slopes along the dolomite hillslope in karst regions of Southwest China were investigated. The results indicated that along the downward slope direction, the degree of soil development gradually increased, forming a typical soil catena pattern. The soil types along the downward direction on the dolomite hillslope gradually transitioned from Entisol to Inceptisol and to Semi-Alfisol. The Entisol was thin and gravelly, with the highest volume ratio of gravel of 75 %. In contrast, Semi-Alfisol was thick and clayey, with the highest volume ratio of fine soil of 97 %. The surface runoff coefficient of the upper slope was only 2.3 % because of the high water infiltration capacity of shallow and rocky soil, and the runoff generation mode was dominated by discontinuous infiltration–excess runoff occurring on rock outcrop patches. Due to the higher soil water content (mean value of 37 %) and frequently occurring lateral flow, the lower slope exhibited the highest surface runoff coefficient of 21 %, mainly as saturation-excess runoff. Catenary soils and their correspondingly divergent hydrological regimes led to average annual soil losses of 0.4, 0.8, and 2.8 t·ha−1·yr−1 at the upper, middle, and lower slopes, respectively. These results advance the understanding of the relationship between hydrology and erosion on karst hillslopes and provide theoretical support for further rocky desertification control. [ABSTRACT FROM AUTHOR]

• Root water uptake depth increased in "S" shape with tree age and stabilized at 20 m after 20 years in an apple orchard. • Soil water deficit increased in depth of 3–21 m at a rate of 5.8 mm m−1 yr−1 from 10 to 24 years of tree age. • Apple trees could draw water horizontally up to 7 m from deeper soil layers of adjacent cropland. • Orchard-cropland mosaic structure is able to optimize the use of soil water resources in the Loess Plateau. It is of great significance to explore soil water distribution and consumptions of the agroforestry systems in water-deficient areas. In recent decades, continuous development of apple orchards in the southern Chinese Loess Plateau has formed the orchard-cropland mosaic vegetation pattern. In this study, soil water content (SWC) in two series were measured, (1) 0–21 m soil profiles of five apple orchards with different stand ages (5, 10, 15, 20 and 24 years) and one cropland; (2) 0–6 m soil profiles at different sites within the orchard-cropland border zone (with apple orchard aged 10 and 24 years old, denoted as AC10 and AC24, respectively). Results showed that (1) the water consumption depth of apple orchards increased in an "S"-shaped pattern with stand age and reached 20 m after 20 years, while the average SWC within 3–21 m layer decreased and the soil water deficits increased at a rate of 5.8 mm m−1 yr−1; and (2) the average SWC in 3–10 m layer of 15, 20 and 24-year-old orchards accounted for 69.3%, 64.2% and 57.9% of the field capacity, respectively, these proportions came to 71.2%, 67.4% and 61.1% in the 3–21 m layer, respectively; and (3) AC24 had greater influence on SWC of adjacent cropland than AC10. The soil water storage of 2–6 m layer in AC24 ranged from 713 mm to 879 mm within 7 m away from the orchard, which were significantly lower than those of 7–15 m away from the orchard (933–1042 mm). Overall, the apple tree root system can absorb soil water from a depth of 20 m in the vertical direction and up to 7 m from the adjacent cropland in the horizontal direction. Therefore, a reasonable orchard-cropland mosaic pattern should be arranged in regional agricultural planning, so as to promote the optimized utilization of regional soil water resources, and to coordinate the development of fruit industry and food security, in which the width of a cropland can't be < 14 m. [ABSTRACT FROM AUTHOR]

[Display omitted] • Droughts and floods are increasing worldwide. • Changes in soil moisture affect the soil microbiome. • Climate change affects the soil environment. • Changes in the soil environment affect crop production. • Drought and floods have a negative impact on agriculture. Climate change is progressing and is already visible to the naked eye around the world. Hydrological events associated with climate change, i.e. floods and droughts, have reached extreme levels in recent years. Researchers warn that these phenomena will continue to intensify. According to recent reports, the number of extreme weather events, including hydrological phenomena, has increased by 60% in Europe over the last three decades. Both water shortages and water surpluses affect the soil environment and its functions. This in turn has a direct impact on crops and agriculture. For example, in the US alone, droughts and floods were responsible for more than 70% of the decline in cereal yields in 2011 alone. However, the soil environment is a complex ecosystem that is not yet fully understood, making it difficult to predict the impact of climate change on its quality and functioning. In this paper, we discuss the effects of floods and droughts on the soil microbiome and the implications of these changes for agriculture. We suggest that changes in soil moisture are an important factor affecting crop growth and yield, which is of great importance for global food security. [ABSTRACT FROM AUTHOR]

Identifying the soil water response processes to rainfall events can provide scientific guidance to sustain and enhance ecosystem services of the terrestrial ecosystem. This study presents the results of soil water content and isotopic compositions response to a typical rainfall in the subtropical zone in east China. The response of soil water (including soil water content, hydrogen and oxygen isotope ratios) to rainfall event at three soil layers (0–10, 10–20, 20–30 cm) in two croplands, two orchards (tea and peach), and two forests were analyzed. The results showed that soil water recharge processes were varied in different land uses. The variation in the isotopic composition of soil water showed a hysteresis pattern, and this pattern was affected by land use types. The extents of isotopes depletion in topsoil (0–10 cm) were along the sequence of forest (9.90%) < orchard (10.86%) < cropland (13.70%), in contrast to the reduction of soil water content (17.46% in cropland, 32.06% in forest, and 41.78% in orchard). Little depletion in isotopes indicated limited evaporation effect on soil water, and the corresponding large reduction in water content suggested large infiltration or water recharge into deep soil, these implying a good water buffer for forest soils compared with crop soils. Soil texture and antecedent soil water were the main factors influencing the variations of both soil water content and isotopic compositions. The identification of different soil water changing processes may be important for water management and plant-available water evaluation. [ABSTRACT FROM AUTHOR]

The maximum depth of rainfall in any 30-minute period - I 30 - has been used as an index of erosive rainfall events for more than half a century, and is a key component of the R factor in the Universal Soil Loss Equation (USLE) and its derivatives. Other indices are in common use, including I 5 , I 10 , and I 15. However, there has been little study of the ability of I 30 to capture the erosive nature of a rainfall event in regions beyond the foundation experimental work in the USA. This paper examines several apparently neglected issues: how reliance on fixed clock-periods might diminish the efficacy of the various indices of short-interval intensity; how well a single 30-minute period is able to reflect the intensity-duration properties of long enclosing rainfall events, and hence, whether the influence of event duration should be evaluated in applications of I 30 and related indices. Results from two Australian sites with high-resolution rainfall records show that within the enclosing rainfall events, actual intensities corresponding to the I 30 value (which is an equivalent intensity or 'rainfall rate', calculated from rainfall depth in 30 min) commonly occur for both less and >30 min. Often the I 30 interval within a rainfall event excludes the most intense periods of rain, and in long events the index reflects ≪1% of the event duration. The I 30 intensity can occur for total durations of 1–3 h in the events studied, or for just a few minutes. An alternative class of indices is proposed, in which fixed clock-periods are not used, and instead, the duration of rainfall within an event that exceeds a nominated intensity is recorded as an index of intensity. This has a number of advantages, including the ability to work with events shorter than 30 min, which are frequently intense but which cannot yield an I 30 index that is strictly comparable to those of longer events. Illustrative results for this new index are presented. • Rainfall events in two high-resolution rainfall records from two Australian sites are analysed for I30. • The I30 period sometimes includes intensity peaks but frequently does not. • Determining I30 for events shorter than 30 min in a consistent way is problematic. • A new intensity index, the duration of rain at and above the I30 intensity, is explored. [ABSTRACT FROM AUTHOR]

The success of reforestation of degraded areas in semiarid environments is constrained by low soil water content and fertility. In order to overcome these limitations, several site preparation techniques previous to plantation have been developed. Organic amendments have been used to improve physical soil properties in order to increase water availability for plants. However, the role of improvement in nutrient availability produced by organic amendment could have been neglected in semiarid vegetation restoration. In this paper, we analyze the effect of two site preparation treatments on soil moisture dynamics of an experimental reforestation with Pinus halepensis Mill. in a semiarid Mediterranean ecosystem. In one treatment (S) only lineal subsoiling (60–80 cm deep) was applied, in the other (SFF) a fresh urban refuse was added at a dose of 10 kg m−1 into the subsoiled furrow. During the first 5 years the growth of pines was significantly higher in SFF. At this time, we studied soil moisture dynamics at 0–20 cm in transects (for 8 months) and in soil profiles at 5, 15, 25 and 45–55 cm depth (for 23 months). Measurements made in two adjacent off-lines unaffected by site preparation were used as covariates. We also measured soil physical properties, macronutrients (N,P,K) and total organic carbon (TOC) content. No significant differences in soil physical properties were found between the amended versus not amended treatment except for hydraulic conductivity and sand fraction content. SFF treatment showed higher hydraulic conductivity, especially in top soil layers (0–10 cm), and lower content of sand fraction. Phosphorus availability was significantly higher in soil amended with organic refuse while no effect was detected in the content of the rest of macronutrients measured. In the transects, a reduction of 30% of the mean soil water content was observed in planting lines (0.14 cm 3 cm−3) in contrast with adjacent off-lines (0.20 cm 3 cm−3); no statistically significant differences between site preparation techniques were found. Soil profiles observations revealed that soil water content was significantly higher in S than in SFF treatment. This suggests that improvement in soil moisture associated to improvement in the physical structure of the soil cannot explain differences in growth. We argue instead this is mostly attributable to improved nutrient availability and microbiological activity associated with the organic amendment. These results stress the importance of a better understanding of the role of nutrients in the restoration of water-stressed ecosystems. • Addition of organic amendment to subsoiled furrows increased growth of planted seedlings. • Soil water content was significantly higher in subsoiled than in subsoiled and amended furrows. • Difference in growth is attributable to fertilizing effects of organic amendment. • The role of nutrients in restoration of water-stressed ecosystems needs to be emphasized. [ABSTRACT FROM AUTHOR]

In this study, we evaluate the use of visible-near infrared (vis-NIR) and portable X-ray fluorescence (pXRF) for delineating soil horizons and how these are affected by soil moisture in a Mollisol (A, Ab, 2E, and 2Bt) profile of south-central Wisconsin. The soil profile was scanned in the field (moist) and soil samples were taken that were scanned in the laboratory (dry) using a vis-NIR spectrometer and a pXRF spectrometer. The CIE L*a*b* color was extracted from the vis-NIR spectra, and the elemental ratios and weathering indices were calculated from the pXRF data. The CIE L*a*b* color, elemental concentrations, elemental ratios, and weathering indices of the vertical transect were interpolated into 1-cm interval up to 100-cm soil depth for moist and dry measurements which were further used in the clustering analysis for identifying soil horizons. It was found that soil moisture decreased L* , a* , and b* color coordinates and the elemental concentrations. Soil moisture had little effect on the vertical distribution of the CIE L*a*b* color and pXRF measurements. Moisture effects can be partly reduced by taking elemental ratios and calculating weathering indices, or corrected by a linear function. The color variables (a* and b*), Ca, and Calcium/Titanium ratio (CTR) distinguished A horizons (Ap, A2, and Ab), whereas the Al, Fe, Ruxton index (R), and Sesquioxide ratio (Saf) distinguished 2E, 2Bt1, and 2Bt2 horizons. The CIE L*a*b* color and pXRF data were excellent variables for delineating soil horizons, and the measurements on moist soil samples performed better than those measured on dry soil samples. • vis-NIR spectra and pXRF data were used for soil horizon delineation. • vis-NIR spectra and pXRF horizonation were compared for moist and dry samples. • Soil moisture decreased L* , a* , and b* color and elemental concentrations. • Measurements on moist soil samples better represented field-delineated horizons. [ABSTRACT FROM AUTHOR]

Reliable estimation of actual evapotranspiration (AET) is essential for hydrological, ecological, and land-surface models. The water balance method is a useful tool for estimating AET. However, it usually neglects soil moisture (SM), which is a dominant factor in AET simulation. Based on field observations, an inverse hydrological modeling method was proposed for regional AET simulation. The method can be applied to estimate AET in other basins, where observations of SM are available. A nonlinear relationship between AET and potential evapotranspiration, a soil water constraint factor, was developed and calibrated for the studied basin. Results of the AET evaluation indicated this relationship was able to estimate AET accurately for both monthly and two-week series, as the Nash and Sutcliffe efficiency coefficient (NSE) was 0.903 and 0.613, respectively. The meteorologically based complementary relationship (CR) method was also able to estimate monthly AET accurately, in particular the revised CR method. But it showed poor performance when estimating AET at a shorter timescale. The performance of the revised CR method with a calibrated parameter was better than that of the initial CR method, as the NSE improved from 0.52 to 0.70. Overall, the performance of the nonlinear relationship with calibrated parameters was better than that of the CR method. In conclusion, monthly AET can be accurately estimated using the CR method based only on meteorological data. • An alternative method for regional actual evapotranspiration (AET) simulation • A calibrated nonlinear relationship can accurately estimate sub-monthly AET • Monthly AET can be accurately estimated by meteorological data [ABSTRACT FROM AUTHOR]

In order to study the characteristics of soil total carbon (TC) transport with slope runoff and interflow during rainstorms in the Zhejiang-Fujian hilly region, China. Slope gradients (5, 8, 15, 25°) and rainfall intensities (60, 90, 150 mm·h−1) were selected as the variable factors for artificially simulated rainfall experiments. Runoff samples were collected every 3 min to measure the volume and TC mass concentration, then we calculated the TC loss rates and loss gross amount. The results showed that the overall trend of TC mass concentration in slope runoff presented a high initial value that gradually decreased with the increase of rainfall duration and finally tended to be stable, and it mean mass concentration was relatively highest at all the 15° conditions. The TC loss rates presented a stability at a certain value after gradually increasing over time at gentle slopes while it led to an increasing trend when the slope was steeper, yet these trends weren't obvious at 150 mm·h−1 condition. The initial TC mass concentration was low at beginning in interflow which rose rapidly to the peak and finally continued to drop to a stable level. The shape of TC loss rate curves was similar to mass concentration curves. For both slope runoff and interflow, the slope gradient had little effect on TC mass concentration. The TC loss gross amount in the runoff (slope runoff + interflow) increased with the increase of slope gradients or rainfall intensities, which reached the maximum value at the 25°, 150 mm·h−1 condition, namely, 12.56 g, though the increase rates of TC transport decreased. The TC loss gross amount with slope runoff showed a trend of increasing first and then decreasing with increasing slope gradients, which all reached the maximum at 8° conditions, however it showed a continued rising trend as slope gradients increased in interflow. TC at 15° and 25° conditions mainly lost with the interflow, though at other slope gradients it mainly transported with the slope runoff. Similarly, the more gentle the slope gradients, the greater the proportion of the slope runoff volume in total runoff. The regression analysis showed at identical conditions, the influence of rainfall intensity on TC loss was larger than slope gradient in slope runoff while the slope gradient had a greater influence on TC loss in interflow. Correlation analysis showed that there was a significant correlation between the runoff volume and the TC loss gross amount in slope runoff and interflow (P < 0.01). There was a linear correlation between runoff volume and TC loss in slope runoff (R2 = 0.95), and power function fits the relationship between TC loss in interflow and runoff volume better (R2 = 0.66). The results provided a calculation method for estimating TC loss in runoff from bare land of weathered granite parent soil in the Zhejiang-Fujian hilly region of China. • The first study on process of total carbon transport on weathered granite parent soil. • Total carbon loss increases as the slope gradient or rainfall intensity increase. • Rainfall intensity has a greater influence on total carbon loss in slope runoff. • Slope gradient has a greater influence on total carbon loss in interflow. • Runoff volume is the most important factor in total carbon loss. [ABSTRACT FROM AUTHOR]

Abstract Estimation of soil sorptivity (S) and hydraulic conductivity (K) is fundamental to model the water infiltration into the soil. This process can be affected by soil water repellency, which is defined as a reduction in soil wettability due to coating of soil particles by hydrophobic substances. Unlike to wettable soils, this phenomenon can generate infiltration curves with double-slope shape: a transient infiltration curve followed by a steady-state section. Because the topsoil final volumetric water content (θ 1) of the transient phase of the double-slope curve is not a measurable data, in principle, the standard model based on the Haverkamp et al. (1994) model cannot be used to estimate S and K. This work presents two different approaches based on the Haverkamp et al. (1994) equation, which allow estimating S and K from the first phase of a double-slope infiltration curve, when θ 1 data are not available. The methods, which are based on the analysis of both short-medium time transient infiltration curve (Tr) and the combination of both short-medium transient and steady-state infiltration steps (Mx), were applied on 20 soils affected by different degrees of water repellency. The Haverkamp et al. (1994) model was also valid for infiltration curves measured on hydrophobic soils, and the final volumetric water content was not an essential data to estimate K and S. Although the steady-state infiltration rate (q 1) calculated with Mx was about 26% larger than that estimated with Tr , comparable K and S values were obtained with both methods. Overall, a large dispersion on the estimate of θ 1 was observed with both methods. The gravimetric time, t grav , estimated in the studied soils was low, <500 s. While the Mx method required simpler numerical calculus, Tr looked like to be more robust and less subjective. Highlights • This work analyzes the first part of a bi-slope infiltration curve affected by SWR. • A first method (Tr) estimates K and S from the transient infiltration curve. • The second one (Mx) combines short-transient and steady-state infiltration analysis. • The methods were applied on 20 soils affected by SWR. • Mx requires less numerical calculus, but Tr was more robust and less subjective. [ABSTRACT FROM AUTHOR]

Abstract The soil hydrological process plays an important role in transporting and distributing water in soils. However, the correlation between water flow behaviors, soil physical properties, infiltration patterns of soil exhibiting different soil layers, and the variation patterns in water flow behavior in rubber-based agroforestry systems remain poorly understood. Here, we mainly used dye-tracer infiltration to classify water flow behavior and HYDRUS-3D to interpret variation patterns of water flow behaviors in a rubber-based agroforestry system in southwest China. The results showed that (1) the soil of forestry patches under Hevea brasiliensis (HB) and Citrus reticulata (CR) exhibited better soil physical properties than those with no vegetation (NV). Compared with these in the NV, the saturated soil water content and field capacity increased by 15% and 21% in CR, and by 2% and 12% in HB, respectively; while the saturated hydraulic conductivity enhanced by 584% (p < 0.001) in the CR plot and by 226% (p < 0.001) in the HB plot. Correlation analysis shows that the soil bulk density, noncapillary porosity and capillary porosity significantly affected the field capacity, saturated water-holding capacity, and saturated hydraulic conductivity. (2) the general infiltration capacity of the whole soil profile, its order of continuity and the degree of connectivity of preferential flow path networks followed the order of CR > HB > NV. Finally, (3) the infiltration flow in soil under HB and CR exhibited a faster downward wetting front and an obvious lateral flow. These infiltration patterns compensated for the insufficiency of soil water in NV and finally caused water redistribution to be more homogenized across the whole soil profile. Therefore, our findings indicated that the rubber-based agroforestry system is a successful approach for conserving water and reducing runoff in tropical regions. Highlights • Dye-tracer experiments and Hydrus-3D were adopted to interpret water flow behavior. • Plots included Hevea brasiliensis (HB), Citrus reticulata (CR), and no vegetation (NV). • The CR plots had the best connectivity of preferential flow path networks. • The CR plots exhibited a faster downward wetting front and an obvious lateral flow. • Water flow inducing by root of HB and CR compensate for the insufficient flow of NV. [ABSTRACT FROM AUTHOR]

Abstract Alpine meadow degradation is a major environmental problem in the Qinghai-Tibetan Plateau of China. While it is expanding at a rapid pace, quantitative information on the effect of grassland degradation on soil properties remains largely unavailable. This study aimed to evaluate the effect of vegetation cover reduction on soil organic carbon (SOC) and nutrient stocks. A degraded alpine meadow with vegetation cover gradients of 90% ± 6.6% to 70% ± 8.3% and 45% ± 8.7% was selected, and soil samples were collected at two soil depths (0–20 and 20–40 cm depths). The reduction in vegetation cover decreased soil sand, SOC, total nitrogen (N), available phosphorus (P), inorganic N, microbial biomass carbon and N, soil moisture, and the ratio of SOC to available P, but increased soil pH, bulk density, the ratio of SOC to total N, and clay and silt contents. The decline in vegetation cover from 90% to 45% significantly affected SOC, total N, total P, and available P stocks at 0–40 cm soil depths (p < 0.05, respectively), with losses as high as 3.89 kg m−2 for SOC, 0.47 kg m−2 for total N, and 1.05 g m−2 for available P. These values corresponded to depletion rates at 28.7%, 39%, and 21%. The increases were as high as 39 g m−2 for total P and corresponded to an increase rate of 15%. The structural stability index had a linear decrease trend with decreasing vegetation cover. The index was >9% at the COV90 site and was close to 5% at the COV45 site for 0–20 cm soil depth. These results confirmed that vegetation cover reduction is a key factor that influences the soil nutrient stocks and structural stability of the alpine meadow. The losses in SOC and nutrients by vegetation cover reduction on the alpine meadow can have a remarkable influence on a large scale. Meanwhile, the alpine meadow may have huge carbon and N sequestration potentials duo to the potential increase of vegetation productivity in this area. Highlights • Effects of alpine meadow degradation were evaluated in homogeneous soils. • The clay and silt contents increased with decreasing vegetation cover. • Vegetation cover reduction from 90% to 45% loss 28.7% and 39% for SOC and total N. • Soil structural stability index decreased with decreasing vegetation cover. • The losses in SOC and nutrients can have a remarkable influence on a larger scale. [ABSTRACT FROM AUTHOR]

Abstract The conversion of extreme xeromorphic vegetation (natural desert forest) to agricultural lands is one of the largest land-use changes in the arid desert region of China over the past 30 years, which may substantially influence soil respiration, and hence may largely determine local climate change. However, few studies have considered the change in soil respiration across natural desert forest and agricultural lands in the arid desert region. In this study, soil respiration and its influencing factors, i.e., soil moisture content, soil salinity, microbial quantity, soil temperature, fine-root biomass, soil organic matter (SOM), air temperature, p H and relative air humidity, were determined across natural desert forest and three chronosequential fields where forests have been converted to agricultural lands having varying length of cultivation period (i.e., 5, 10 and 30 years of cultivation) in an arid desert region. We used two-way repeated measure ANOVA for evaluating significant differences in soil respiration and its influencing factors between natural desert forest and agricultural lands, and then employed structural equation model (SEM) with the support of stepwise regressions analyses to test for the direct and indirect effects of influencing factors on soil respiration. The results showed that soil respiration significantly increased along the years of cultivation in agricultural lands (P < 0.05). Soil respiration was higher in all agricultural lands than that in natural desert forest (P < 0.05). Stepwise regressions and SEM showed that soil moisture content and soil salinity had explained 75% of the variation in soil respiration through direct and indirect effects via abiotic and biotic factors. Soil respiration was significantly affected by the sum of the direct and indirect effects of soil salinity (β = −0.46) and soil moisture content (β = 0.49) via microbial quantity, soil temperature, fine-root biomass and SOM. This study suggests that deforestation and subsequent agricultural activities might alter the soil moisture and salinity contents, and as a consequence influence soil respiration across natural desert forest and agricultural lands in an arid desert region. Graphical abstract Unlabelled Image Highlights • Soil respiration increases along the years of cultivation. • Soil respiration was higher in agricultural lands than that in natural desert forest. • Deforestation and agricultural activities alter the soil moisture and salinity. • Soil moisture content and salinity drive the variation in soil respiration. [ABSTRACT FROM AUTHOR]

Abstract Soil moisture forecasts are vital for environmental monitoring, the health of ecological systems, hydrology, agriculture and understanding the soil characteristics. In this study, we design a new multivariate sequential predictive model that utilizes the ensemble empirical mode decomposition (EEMD) algorithm hybridized with extreme learning machines (ELM) to forecast soil moisture (SM) over weekly horizons. The EEMD data pre-processing utility is a self-adaptive tool, which does not require a predefined basis function and avoids frequency-mode mixing issues. The proposed multivariate sequential EEMD model is designed to sequentially demarcate model predictor variables and the target (SM) into analogous intrinsic mode functions (IMFs) and a residue component using the EEMD process, to address the complexities and associated non-linearities in hydrologic-based inputs. To validate the new approach, four diversely characterized sites in Australia's Murray-Darling Basin are purposely selected where 13 weekly hind-casted predictors are collated from the Australian Water Availability Project WaterDyn physical model. After the sequential EEMD transformation process, a two-stage feature selection employing cross-correlation and random forest based Boruta wrapper algorithm is adopted to extract pertinent features from the hydro-meteorological predictor series to construct a hybridized multivariate sequential EEMD-Boruta-ELM model. Comprehensive model evaluation using statistical metrics and diagnostic plots against alternative methods: hybrid multivariate adaptive regression splines (MARS) (EEMD-Boruta-MARS) and classical MARS and ELM, establish the superiority of hybrid EEMD-Boruta-ELM model, yielding relatively low errors and high performance. The study ascertains that the EEMD-Boruta-ELM hybrid model can be explored as a pertinent data-driven tool for relatively short-term soil moisture forecasts, thus advocating its practical use in near real-time hydrological and pedological applications. Graphical abstract Unlabelled Image Highlights • Designing multivariate sequential EEMD-Boruta-ELM for soil moisture forecasts • Hybrid EEMD-Boruta-ELM is evaluated against EEMD-Boruta-MARS, ELM and MARS models. • Weekly soil moisture forecasting performed in Murray-Darling Basin, Australia • New hybrid EEMD-Boruta-ELM model outperformed the benchmark models. • EEMD-Boruta-ELM model has potential for real-time hydrological forecasting. [ABSTRACT FROM AUTHOR]

Abstract The Water Drop Penetration Time (WDPT) technique was applied in two subsequent years (2016 and 2017) to check surface soil water repellency (SWR) in a Sicilian mountain area affected by a wildfire on June 2016. A total of 93 sites were sampled and from 3 to 100 droplets were used to characterize a site. The detected SWR varied with the severity of the wildfire, being practically absent in the unburnt control area and slight to extreme in the burnt areas. The percentage of extremely repellent sites increased with wildfire severity. SWR vanished one year after the passage of the fire in sites where fire severity was moderate but it persisted in the case of a severe wildfire. In general, the number of applied droplets at a site (from 3 to 100) and the SWR classification methodology (modal class, mean of the measured WDPTs) did not have a strong impact on SWR assessment. However, the data collected with the first few droplets (i.e. three or four) could help to make choices about the number of droplets to be used to reliably characterize a site. If all the initially used droplets give clear signals of wettable conditions, it is plausible to believe that a small number of droplets will be enough to characterize the site. If signs of water repellency are detected, then it could be advisable to use larger samples sizes. Complementing a detailed information on the spatial distribution of wildfire severity with a WDPT experiment appears appropriate to establish where fire mitigation techniques should promptly be implemented after the fire. Experimental developments with larger databases are advisable to improve our ability to capture spatial and temporal variability of SWR. Highlights • A Sicilian mountain area was affected by a wildfire on June 2016. • Soil water repellency (SWR) was tested by the Water Drop Penetration Time test. • The higher the wildfire severity, the higher the number of extremely repellent sites. • SWR persisted one year after the fire in sites where fire severity was severe. • SWR assessment was not strongly affected by the number of applied droplets. [ABSTRACT FROM AUTHOR]

Abstract Rainfall erosivity is one of the key parameters in Universal Soil Loss Equation (USLE), which has been used to predict the amount of soil loss by water for 50 years. Investigating spatial and temporal trends in rainfall erosivity is important for soil and water conservation planning. Rainfall erosivity (the R factors) in many regions is expected to be altered due to changes in rainfall patterns related to rainfall intensity and the frequency and spatial distribution of storm events that may occur with climate change. In South Korea, some researchers have studied temporal variation in meteorological and hydrologic phenomena with climate change, particularly temperature and precipitation trends. The purpose of this study is to investigate spatial and temporal variations in rainfall erosivity and erosivity density and to improve our understanding of the evolution of rainfall erosivity in South Korea. First, we calculated rainfall erosivity at 46 stations for 1961–2015 using 5-min precipitation data. Second, we examined spatial and temporal variability in the rainfall erosivity; trends and change points of R factor time series and analyzed the relationships between rainfall erosivity and climate indices (such as the precipitation amount, number of effective events, and duration). Four trend tests such as the t -test, MK test, modified version of the MK test, and BBS-MK test, were used to detect trends in the annual R factor, total duration, number of effective events, total depth, mean maximum 30-min intensity, and total kinetic energy time series for all employed stations. The results provide insights into the evolution of rainfall erosivity and the effects of large-scale climatic circulation on rainfall erosivity. Highlights • Annual R factors based on 5-min data in South Korea for 1961–2015 were presented. • New annual and monthly iso-erodent maps were presented and analyzed. • Spatial variation of the R factor is larger than those of erosivity density. • The annual R factor at 41 stations in South Korea does not have a significant trend. • Total kinetic energy & rainfall depth are strongly correlated with the R factor. [ABSTRACT FROM AUTHOR]

Abstract Review studies indicate that conservation tillage effectively reduces runoff generation measured on large plots, but less so on smaller plots. These tillage and scale effects have never been measured in a single study for temperate mechanized agriculture. With the objective to study how runoff production changes with scale as influenced by tillage we set up rainfall-runoff plots of 5 m2, 30 m2 and 180 m2 size, on a field split into a reduced tillage (RT) and a conventionally ploughed field (CT) during two crop seasons (maize and wheat). In addition, we conducted rainfall simulations on small plots (0.7 m2) and measured soil surface properties. Average scale effects, defined as reduction of runoff coefficients with increasing plot size, were 57% (RT) and 37% (CT) between 5 m2 and 30 m2, and − 24% (reversed) (RT) and 27% (CT) between 30 m2 and 180 m2. Tillage effects, defined as the reduction in runoff coefficients of RT compared to CT were 65% at 5 m2, 86% at 30 m2 and 31% at 180 m2. On average, scale effects were 15% stronger on RT compared to CT. The overall level of runoff coefficient was most clearly affected by crop type, with winter wheat having 1.7–30 times lower runoff coefficients than maize. Crop development and soil moisture negatively affected runoff coefficients on Wheat, while rainfall intensity affected runoff coefficients positively on Maize. No evidence for interactions of these variables with either scale or tillage were found. Runoff coefficients of CT and RT diverged with scale (i.e. runoff accumulation) between 5 m2 and 30 m2, which was expected and can be explained with higher residue cover and macropore density on reduced tillage than conventional tillage slowing down runoff and increasing infiltration opportunities. Unexpectedly, between 30 m2 and 180 m2, on Maize, runoff coefficients converged strongly, which was interpreted with erosion of sealing on conventional tillage. In summary, this study confirms previous findings on the effects of tillage on runoff coefficients, but finds indications that important process transitions take place at the field scale that are affected differently by tillage, and that are not yet sufficiently studied or accounted for in models. Highlights • Unique runoff data at 5, 30 and 180 m2 plot scales and 2 tillage treatments • Scale effects were stronger on reduced than conventional tillage. • Infiltration increased unexpectedly towards 180 m2 on conventional treatment. • Effect of tillage on seal formation and erosion could explain this observation. [ABSTRACT FROM AUTHOR]

Abstract The long-term performance of green infrastructures (e.g., vegetated slopes, green roof, bio-retention systems, etc.) can be affected by the wilting of vegetation (i.e., tendency of evapotranspiration (ET) to be nil) attributed to the decrease in volumetric soil water content. Therefore, it is important to explore an approach to investigate the wilting time of vegetation so that mitigation measures can be taken to ensure the serviceability of green infrastructure. The technical note aims to 1) conduct probabilistic analysis of volumetric soil water content in slopes vegetated with non-crop tree and grass species; and 2) further explore this analysis method for estimating probability of wilting (tendency of transpiration becoming nil) of the selected vegetation species under natural climate conditions. For this investigation, two non-crop species namely, Ivy tree (Schefflera heptaphylla) and Bermuda grass (Cynodon dactylon), commonly grown in subtropical regions in world were selected. A normal distribution was found as the best fit to the measured volumetric water content under the impact of both species. The estimated mean value was found significantly higher in Cynodon dactylon slope compared with that of Schefflera heptaphylla slope, while the coefficient of variation among the species is similar. The probability of wilting of C. dactylon is found lower than that of Schefflera heptaphylla. In the present study, the significance of using probabilistic approach for characterizing the distribution of volumetric soil water content to assess the reliability of vegetated infrastructure was highlighted. The study is useful for estimating the behaviour of vegetation for better planning of restoration and rehabilitation measures. This differs from those in agricultural fields with the usually shorter period for monitoring of vegetation growth (mostly within 3 months), and they are usually subjected to controlled manual irrigation. Highlights • Water content variations in slopes with tree and grass cover were compared. • Probability distribution functions of soil matric suction varies with climate. • Simplified probabilistic analysis of soil water content in vegetated slopes • Probability of wilting of Cynodon dactylon and Schefflera heptaphylla is determined. [ABSTRACT FROM AUTHOR]

Abstract Spatial distribution of soil moisture (SM) is a prerequisite for research and management of agriculture and ecology. However, it is still a challenge to retrieve SM data in highly heterogeneous landscapes. By investigating environmental factors (soil, vegetation and topography) and comparing different remote sensing sources (Landsat-8, Radarsat-2, ASTER Global Digital Elevation Model (DEM) V002 (ASTGTM2), unmanned aerial vehicle (UAV)) for karst mountainous catchments of southwest China, this study identified key controlling factors on the spatial distribution of SM and built a remote sensing model for SM estimation in highly heterogeneous landscapes. Results showed that vegetation type (35.7%), aspect (7.7%), height index (4.2%), soil bulk density (3.3%), soil total nitrogen (3.1%), aspect interact with vegetation type (3.4%) and soil total phosphorous (1.3%) totally explained 58.8% of the SM variability. The correlations between SM and topographic derivatives varied with DEM resolutions (1–50 m), and generally reached their highest values at 7 m for height index, slope gradient, and aspect, 16 m for flow accumulation and topographic wetness index, and 43 m for curvature. Partial least-squares regression analysis showed that optical and infrared bands from Landsat-8 and topographic derivatives from UAV photogrammetry DEM were more strongly correlated with SM than other datasets. An empirical model (SM = 9.27 ∗ 10−2 HI − 1.82 ∗ 10−5 B 5 + 0.519) with only height index and B5 band from Landsat-8 as inputs is proposed, as it shows acceptable performance (R2 = 0.36; RMSE = 0.076). The results of this study provide useful information for SM remote sensing in karst mountainous area and similar heterogeneous landscapes. Highlights • Vegetation is the major controlling factor for SM in karst region. • Correlation between topographic derivatives and SM varied with resolutions of DEMs. • UAV photogrammetry showed great potential for hydrological research. [ABSTRACT FROM AUTHOR]

Abstract In the context of the circular economy, the use of animal excrements as fertilizers is encouraged, but the addition of such organic materials can develop soil water repellency (SWR) or hydrophobicity. There is a lack of consensus about how to assess SWR in agricultural soils. This work evaluated SWR when pig slurries were applied onto soil using the two most common testing methods: the water drop penetration time (WDPT) and the molarity of ethanol droplet (MED) tests. The experiment consisted of five different slurry treatments plus a control (no slurry added). At sowing, slurry from fattening pigs (SF) or no slurry application was combined with a second application at the cereal tillering stage, in which SF, slurry from sows (SS) or no-slurry were the treatments. Soil water repellency was tested at cereal tillering before slurry application and then during the following 47 days. At each sampling date, hydrophobicity was tested in undisturbed samples at field-moist and after 25 °C, 65 °C, and 105 °C oven drying. Disturbed samples were tested after 40 °C oven drying. Soil disturbance removed SWR. Under field conditions, undisturbed samples attained the maximum SWR expression 7d from pig slurry application; moderate and very severe scores using WDPT and MED were respectively attained. From 14d to the end of the experiment, the highest SWR was observed after 105 °C oven drying and when SF applications at sowing (900 kg TOC ha−1) had been combined with SS applications at cereal tillering (1894 kg TOC ha−1). Slurry hydrophobic compounds rather than slurry dry matter influenced SWR expression which is enhanced as the soil dries. The persistence of repellency (WDPT test) was more sensitive to detecting changes in SWR between treatments than the changes in its severity (MED test). The importance of the SWR described hereafter slurry application will depend on plant cover over the soil and the effects in slaking prevention in order to avoid superficial water runoff. Highlights • Pig slurry develops transitory soil water repellency (SWR) lasting for 47 days. • The strongest SWR is recorded seven days after pig slurry addition. • Hydrophobic compounds in solid and liquid slurry fractions explain SWR persistence. • Soil sample management and moisture content influenced SWR expression. [ABSTRACT FROM AUTHOR]

Abstract In the Alberta oil sands, many soils available for reclamation contain portions of oil sand referred to as aggregated oil sand material (AOSM). The objective of this study was to determine the infiltration rates of soils and AOSM from various salvage depths and with various concentrations of interstitial petroleum hydrocarbons (PHCs). The water infiltration rates of AOSM and surrounding soil were determined using a miniaturized infiltrometer, revealing that the soil allows significantly (P < 0.05) greater infiltration than the AOSM. Furthermore, highly-weathered AOSM which originate from the near-surface, exhibit significantly lower PHC contents and greater infiltration rates than medium- and low-weathered AOSM, which are found at depth. The infiltration of 95% ethanol indicates water repellency (WR) is present in both the AOSM and surrounding soil; however, the ethanol results also suggest that the reduced water infiltration rates of AOSM in comparison to the soil, are primarily due to structural differences such as reductions in total porosity and pore connectivity resulting from interstitial PHCs. The diminished infiltration of water into AOSM indicates the ability to slow the downward flow of water and increase the residence time of water in overlying coarse-textured soils, potentially altering the soil water regime and associated ecosite. Highlights • Infiltration rates of coarse-textured materials reduced by interstitial hydrocarbons. • Infiltration rates of coarse-textured materials decrease with increasing hydrocarbons. • Infiltration rates of oil sand increase with increasing extent of weathering. • Infiltration rates of oil sand decrease with increasing depth into the soil profile. [ABSTRACT FROM AUTHOR]

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

Abstract Inorganic carbon, as allogenic and pedogenic carbonates mixtures, can be a significant component of arid and semi-arid zone soils. It has been claimed, that the formation of pedogenic carbonates does not sequester atmospheric carbon dioxide, when formed from the preexisting limestone: Ca+2 + 2HCO 3 − → CaCO 3 ↓ + CO 2 ↑ + H 2 O. But if the cation is derived from a non‑carbonate source sequestration can occur. Among the unconsidered sources in nature are the contribution of Ca+2, released from adsorption sites on the clay surfaces. Analysis of DIC, δ13C and Δ14C data show in the present study that sequestration does occur within the unsaturated zones (USZ) in a semiarid region: 1) the DIC is depleted as carbonate precipitates into the USZ, 2) the released CO 2 , does not immediately return to the atmosphere (except for the samples nearest to the surface) but recycles to the soil-gas of high CO 2 partial pressure, and 3) that radiocarbon, which is generated only in the overlying atmosphere, and exhaled into the USZ by roots and the decay of soil organic matter, is incorporated within the calcite mineral. Thus, a net sequestration of atmospheric CO 2 does occur. Highlights • Inputs of δ13C, Δ14C and δ18O in DIC of the soil moisture in USZ were traced. • Δ14C showed precipitation and exchange between DIC and soil. • H+ releases Ca2+ from clays surface sites to form stable calcite • Pedogenic calcite thus formed is a net sequestration of atmospheric - CO 2. • Planting of trees in semi-arid regions can facilitate removal of atmospheric - CO 2. [ABSTRACT FROM AUTHOR]

Abstract Brazilian Atlantic Forest is recognized by the UNESCO as one of the most important biosphere reserves on the planet but is threatened by extinction. The objective of this study was to analyze the main components of the water balance in an Atlantic Forest (Neotropical Forest) catchment in the Mantiqueira Range, Brazil, which is a Tropical Montane Cloud Forest. The main focuses was to analyze baseflow, evapotranspiration, soil moisture, and canopy rainfall interception to understand the hydrologic dynamics in this specially important montane forest. On average from the two studied hydrological years (2009/2010 and 2010/2011), evapotranspiration (ET), streamflow (SF), and water storage in the catchment at the end of hydrological year corresponded, respectively, to 50%, 34.8% and 15.2% of total gross precipitation (P). On average, baseflow corresponded to 73.5% of SF. The estimated potential groundwater recharge during the wet seasons was 403.8 mm (21.7% of P observed in the wet season) and 710.5 mm (28.5% of P observed in the wet season), respectively, for 2009/2010 and 2010/2011 hydrological years, showing that the catchment is able to store groundwater to provide the maintenance of the streamflow during early recessions and drought periods. Therefore, the baseflow is important in mountainous catchments in the tropical regions to provide important ecological functions, mainly as freshwater reserve. Highlights • Mountainous Neotropical Forest has fundamental hydrologic role in tropical regions • Baseflow has been sustained by groundwater recharge in forested mountainous sites • Interaction forest canopy/transpiration and soil moisture define water balance • Catchment was capable of close water year with surplus for sustaining main outputs [ABSTRACT FROM AUTHOR]

Abstract The present study evaluates the performance of five existing and three proposed antecedent moisture condition (AMC)-based runoff curve number (CN) conversion formulae utilizing the data of a large number of naturally observed rainfall (P)–runoff (Q) for an agricultural field located at Roorkee, Uttarakhand, India and available published data around the globe. For developing the proposed formulae, CNs were derived for P–Q datasets from 39 watersheds using standard initial abstraction ratio (λ) values as 0.20 and 0.030. The existing formulae outperformed the proposed formulae when tested numerically using the available National Engineering Handbook chapter–4 (NEH–4) tabular AMC-dependent CNs as target values. It might be because the existing formulae were derived from the same datasets used as targeted values (i.e. NEH–4 AMC defining tables). Therefore, when tested on large set of field data, the three proposed formulae performed better than the existing ones, the formula with λ = 0.030 the best of all. Highlights • Existing formulae performed best when tested using Tabular AMC CNs as target value. • Tabular CN 3 and CN 1 are better described as 88th and 12th percentiles, respectively. • The optimized λ-values vary from 0 to 0.331 with 0.0312 as a mean value. • The proposed formulae incorporating λ = 0.03 performed best in the field application. [ABSTRACT FROM AUTHOR]

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