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

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

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

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

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

[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]

• 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]

Purple soil bunds are embankments constructed along the contour on purple soil sloping farmlands, and play a key role in controlling soil erosion. The soil shear strength makes a significant influence to the bund stability; however, few reports have documented how purple soil shear strength responds to the soil physical properties. The main goal of the present study was to determine how indicators of soil shear strength vary with the soil water content and dry density. In this study, we collected soil samples from 3 purple soil bunds in Zhong County, in the Three Gorges Reservoir Area in China, and performed an unconsolidated undrained triaxial compression test to study the soil shear strength in terms of the cohesion ( c ), internal friction angle ( φ ), and the principal stress difference ( σ 1 – σ 3 ). The test results show that when the dry density was constant and the soil water content increased, the soil cohesion increased and then decreased, and the results fitted to a quadratic curve. As the soil water content increased, the internal friction angle of the soil bunds decreased and displayed a first-order exponential decay. As the soil water content increased and the confining pressure remained constant, the principal stress difference decreased rapidly. When the soil water content was constant and the dry density increased, the soil cohesion, internal friction angle, and the total principal stress difference increased, although at different rates. In general, the water content had a greater effect on the cohesion, internal friction angle, and the principal stress difference than the dry density, but there were little or no interaction between water content and dry density. Furthermore, except when the water content was 6%, the stress–strain characteristics were similar across the range of water contents. For a low water content, fixed confining pressure, and an increasing dry density, the curves gradually changed from the hardening type to the weak hardening type and then to the softening type. In most cases the curves corresponded with the hardening type as the confining pressure increased. [ABSTRACT FROM AUTHOR]

The effects of soil water content (SWC) and erodibility on available nutrient losses, as well as the influence of freeze-thaw on available nitrogen (AN) and phosphorus (AP) losses from loess soils have rarely been considered. We report on a series of laboratory simulation experiments conducted to determine SWC and soil erodibility effects on AN and AP losses under freeze-thaw conditions. Effect of freeze/thaw compared to unfrozen, two treatments were set (LS: Loess that unfrozen; FTS: Freeze-thawed a loess), and we studied five SWCs, between 10% and 30%, and we divided SWCs into two groups: lower water content areas (10% and 15%), higher water content areas (20%, 25%, and 30%). Overall, significant differences in runoff/sediment associated AN and AP concentrations of different SWCs for two treatments (p < 0.05) were noted, while the relationship between SWC and AN and AP loss show a quadratic function change trend (R 2  > 0.8). Largest runoff-associated AN and AP losses were found when the SWC was 30% and the largest sediment-associated AN and AP losses were found when the SWC was 10% in the two treatments. The soil erodibility factor ( K ) of the LS was less than that of the FTS when the SWC was low, and greater in a high water content area. The influence of runoff on sediment was positively linear. The absolute slope of the regression line between runoff rate and sediment yield rate is shown to be suitable as a soil erodibility indicator, while runoff-associated AN losses are mainly controlled by runoff rate, and are weakly affected by soil erodibility (p > 0.05). However, soil erodibility significantly influenced sediment-associated AP losses (p < 0.01), best described by a positive logarithmic relationship. Since the sediment-associated AP losses dominated the total AP losses for the two treatments, soil erodibility also exhibited a significant influence on total AP losses (p < 0.01). The freeze-thaw effect increased the total AN loss when the SWC was 15%, 20%, and 30%, and increased the total AP loss when it was 10% and 15%. The results of this study provide a better understanding of soil and available nutrient loss mechanisms under freeze-thaw conditions. [ABSTRACT FROM AUTHOR]

Electromagnetic induction (EMI) is an established method for mapping field-scale soil water content (SWC). However, the correlation between the recorded apparent electrical conductivity (ECa) and SWC is affected by several factors that can vary across test sites and with environmental conditions. As agricultural practices affect both, ECa and SWC, it is likely that the mismatch in SWC predictions using ECa can be directly or indirectly attributed to agronomic treatment effects. Hence, EMI based SWC predictions are often limited to sites with one soil amendment and strong ECa – SWC correlations. However, non-invasive SWC mapping is particularly desirable for larger agricultural fields, covering different soil amendments. We hypothesized that different agronomic treatments altered the ECa – SWC correlations and consequently the EMI based SWC prediction accuracy. We further hypothesized that a model established on areas with high positive ECa – SWC correlation could be used to predict SWC for areas with unsuitable ECa – SWC correlations. A field-scale experiment was conducted to investigate the effects of six agronomic treatments (including biochar, BC) on SWC, ECa, and ECa – SWC correlation in a silage corn field. We tested the accuracy of three models to predict the SWC of independent data sets using data from i) all treatments (T all ), ii) plots with lowest and iii) plots with highest ECa – SWC correlations. We found statistically significant treatment effects on both, ECa and SWC, although overlapping data ranges were given. Furthermore, the correlations between ECa and SWC were affected by the treatments. Correlations were found to be lowest on nutrient-rich dairy manure plots (T2) and highest on the control plots (T6), likely due to differences in the ionic strength of pore water. BC mitigated the effect of ionic strength for T2 while it showed no measurable effects on ECa on plots receiving inorganic fertilizers. Most accurate SWC predictions were reached by employing T all data (RMSEP 1.40–3.13% vol.). However, models based on T6 data provided similar accuracies (RMSEP 1.46–3.96% vol.) using only 12.5% of the area. The T2 based model performance failed (RMSEP 3.02–7.21% vol.). Results suggest that ECa – SWC models established on non-manured areas could provide best possible SWC predictions and are recommended as training areas if soil texture and mineralogical composition can be expected to be relatively homogeneous. [ABSTRACT FROM AUTHOR]

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

The spatio-temporal dynamics of soil water are the key critical zone processes that control hydrological, biogeochemical and environmental processes at various spatial scales. Soil water content (SWC), which has been widely adopted in traditional studies, does not consider the energy state of soil water and thus cannot directly reflect the active status of subsurface fast flow (flux when SWC is above field capacity). By subtracting water content at field capacity (− 33 kPa) from SWC, free water content (FWC) were calculated and used to indicate status of subsurface fast flow. In this study, the spatio-temporal variations and controlling factors of SWC and FWC were compared on a typical bamboo forest hillslope in Taihu Lake Basin, China. An improved temporal stability (TS) analysis replacing the spatial means of SWC in the equation by the field capacity was also proposed to better identify the active locations of subsurface fast flow. Results showed that the SWC and FWC had similar temporal trends and spatial patterns. Thresholds of spatial mean SWCs were found at 10- and 30-cm depths (0.17- and 0.18-m 3 m − 3 , respectively). Above these thresholds, the spatial means and variances of FWC started to increase with the spatial mean SWCs. This indicated that the subsurface fast flow starts to occur. Below these thresholds, nearly no free water existed and the subsurface fast flow ceased. The active locations of subsurface fast flow determined from the improved TS analysis were not always consistent with the high SWC locations. This indicated that traditional TS analysis was not adequate to interpret the active status of subsurface fast flow. Controlling factors of SWC and FWC spatial variations were generally similar. However, the spatial distribution of FWC was less affected by soil properties and topography. In addition, the influences of controlling factors on FWC were more temporally varied. These findings will be beneficial for identifying the “hot spots” of soil water movement and biogeochemical processes. [ABSTRACT FROM AUTHOR]

The occurrence and consequences of soil water repellency (SWR) have been reported in many parts of the world, but little is known on the reasons and mechanisms of SWR in grasslands. Although considerable advances have been made in the past 10 years in understanding the impact of hydrophobic organic compounds on water repellency, there is still a considerable amount to be learnt. Of particular importance is the interaction between soil chemical characteristics and SWR in soil. The research gaps and seeks to understand how soil water repellency in grasslands of Inner Mongolia is influenced by soil chemical properties. The SWR of soil samples ( n = 80) at the surface of the grassland (0–10 cm) collected in Xi Linhot was measured using the Water Drop Penetration Time Test (WDPT), and the relationship between soil chemical properties (e.g. soil organic matter, SOM) and SWR was studied in grassland soils. Results showed that SWR reached a peak value with an average of 80 s when the soil water content was 10.7%, the relationship between WDPT values and soil water contents showed a one-peak distribution. Soil water repellency increased exponentially with organic matter contents, total N, and available N and poorly correlated with carbonate, available P, available K and pH in grassland soils. Our results can provide the influencing factors of soil water repellency and promote soil amelioration. [ABSTRACT FROM AUTHOR]

Soil water content (SWC) plays a significant role in land surface hydrological processes (e.g., evapotranspiration, infiltration and runoff) and the spatial and temporal distribution of vegetation in arid and semi-arid regions. The aim of this study was to analyze the temporal stability of the SWC distribution pattern and to examine the primary factors that influence SWC temporal stability over a year and during the rainy season at different soil depths in terraces. The SWCs in eight soil depths at intervals of 0.2 m down to a depth of 1.6 m were measured at 21 locations in terraces containing jujube trees ( Ziziphus jujuba Mill. ) over two periods (over a year and during the rainy season). The results showed that the mean SWC over a year was larger than that for the rainy season in the corresponding layers. The mean SWC was highest in the lower slope. Soil depth significantly affected the SWC distribution over time and space. Water uptake mainly occurred between 1.0 and 1.2 m soil depth in both the rainy season and over the whole season. Moreover, the SWC demonstrated moderate spatial variability and was normally distributed at each depth. The temporal stabilities of SWC spatial patterns were strong for both the year period and the rainy season. The number of SWC representative locations varied depending on the soil depth. The SWCs measured at the best representative locations correctly represented the mean SWCs. Soil particles were the primary influencing factor affecting the mean relative difference, and root density was the primary influencing factor affecting the standard deviation of the relative differences. In conclusion, the SWC in the terraces showed stronger temporal stability during the rainy season compared to the year period. [ABSTRACT FROM AUTHOR]

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

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

In this work, we investigated how the reindeer grazing in subarctic boreal Scots pine forests and climate (air temperature and the amount of precipitation) affects soil temperature, soil water content, and ultimately the CO 2 efflux from forest soils. The study was carried out in years 2013 and 2014, where 2013 was an extremely dry year (especially the summer), while 2014 was a “normal” year. Our work showed that in subarctic mature pine forests, soil temperatures were higher, and soil water content was fluctuating more on grazed areas compared to non-grazed areas in both years. On both years, the soil water content on the grazed area was higher in June and the situation changed in the second half of July when the moisture content in the non-grazed area remained higher. There was a negative correlation between soil water content and soil temperature. The soil CO 2 effluxes were mostly affected by the year of measurement, time of measurement (different months through growing season), soil temperature and also by the management (grazed or non-grazed) resulting in higher CO 2 emissions on the grazed areas. Soil moisture content was not affecting the soil CO 2 efflux. The average soil CO 2 efflux values were significantly higher in the year 2014 compared to the year 2013 mainly due to differences in soil temperature at the beginning of season. [ABSTRACT FROM AUTHOR]

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

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

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

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

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

• Two low-cost FDR-TDR devices to measure soil water content are evaluated. • Devices were compared with TDR100 using 2- and 3-rod probes. • Comparations were made in air, distilled water, and in a wetted soil column. • The study was complemented with a field experiment. • Robust estimates of water content were obtained with the two VNA devices. Time Domain Reflectometry (TDR) is a non-destructive technique to determine the soil apparent dielectric constant, ε a , the volumetric water content, θ, and bulk electrical conductivity, σ. However, the high cost of TDR devices may limit its use. This study evaluates two different low-cost Vector Network Analyzers (VNA) commercially available (NanoVNA), with 1.5 (VNA1.5) and 3.0 (VNA3.0) GHz maximum operating frequency. NanoVNA can be used for measurements of Frequency Domain Reflectometry (FDR) or, after suitable post-processing, for θ and σ TDR measures. Although FDR and TDR are dual procedures, TDR is easier to interpret for soil experiments. The TDR waveforms and ε a measured with NanoVNA connected to 10 and 20 cm length three-rod probes immersed in air, distilled water, and a soil column with different θ were compared to those measured using a TDR100 (Campbell Sci.) instrument. The capacity of VNAs to measure σ was evaluated by immersing a 10 cm length three-rod probe in different NaCl-water solutions. Measurements obtained with the VNA and TDR100 were compared in a field test using two-rod 22 cm length TDR probes inserted in soil plots with increasing water content. A robust fit was observed between TDR waveforms registered with the two VNAs and the TDR100. Although VNA3.0 doubles the frequency range of VNA1.5, both devices allowed for good estimates of ε a (ε aVNA1.5, 3.0 = 1.001 ε aTDR100 – 0.2125; R2 = 0.999). These results indicate that the low-cost VNA devices can measure soil water content with similar accuracy and precision as the TDR100. A good agreement (σ VNA1.5, 3.0 = 0.999 σ CM + 0.0023; R2 = 0.999) was also observed between the σ measured using a conductivity meter (CM) and that estimated with the VNAs. Finally, a good correlation was also observed between θ measured in the field experiment with TDR100 and the VNA1.5 and VNA3.0 devices. [ABSTRACT FROM AUTHOR]

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

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

Aims Antecedent soil water content (ASWC) is an important factor affecting soil water infiltration, runoff and soil erosion on slopes but it is difficult to measure or forecast accurately and is not often reported in soil erosion databases. Methods Runoff plots (12 m × 5 m) were used to collect runoff and sediment during the rainy seasons between April 2010 and October 2013 on the Loess Plateau, China. The HYDRUS-1D model was calibrated and tested using the data collected from the plots. The relationships of ASWC with runoff and sediment yield were investigated using the model output values for ASWC. Results The model performance was satisfactory, with a mean Nash–Sutcliffe model efficiency coefficient of 0.411 and a root mean square error of 0.031 during the four study years. Runoff was directly affected by rainfall amount and rain intensity. Furthermore, runoff typically increased with ASWC. Conclusions HYDRUS-1D can provide temporal ASWC data that could be used for runoff prediction. [ABSTRACT FROM AUTHOR]

Plants in many sand dune systems experience arid-like conditions due to low water capacity and high hydraulic conductivity of sand grain medium. Here, water availability was studied in coastal sand dunes in a Mediterranean climate on which the dominant species is a desert dwarf shrub, Artemisia monosperma . Special emphasis was put on landscape heterogeneity and contrasts between dune stabilisation states and microhabitats, conditions after rain events and in the dry season and catenary profiles. During the approximately 150 day-long dry season, as well as during multiple dry spells in the rainy season, soil water content at 50 cm depth was below permanent wilting point in both mobile and stabilised dunes. The open matrix between the A. monosperma dwarf shrubs was characterised by higher hydraulic conductivity and soil water content compared with soil under A. monosperma dwarf shrubs, and played an important role in supporting the dwarf shrubs. In the mobile dunes, in which there is greater open matrix area, this has resulted in higher soil water content in the dunes that increases into the adjacent interdunce, while the opposite was found in the stabilised dunes. The dominance of A. monosperma is thus related to its ability to utilise water from the open matrix, and its distribution is driven by source–sink relations between the open matrix and A. monosperma dwarf shrubs, respectively. In stabilised dunes, A. monosperma dwarf shrubs increase in size and total percentage cover, reducing water-contributing open matrix area and probably increasing competition over water. As a result, the spatial distribution pattern of A. monosperma dwarf shrubs is regular, maintaining a certain degree of open matrix to support the living dwarf shrubs, which theoretically cannot achieve a full coverage of the dune surface in this Mediterranean system. [ABSTRACT FROM AUTHOR]

Inappropriate soil management on the Chinese Loess plateau has induced significant soil erosion, and improvements were obtained with cover crops, whereas few studies were reported about orchard soil management. This study investigated effects of five soil management (SM) practices on surface runoff and soil water content, which were (i) full ground mulching with jujube branches (BM), (ii) strip tillage only (ST), (iii) jujube branch mulch + strip tillage (BMT), (iv) jujube branch mulch + strip white clover ( Trifolium repens L.) cover (BMWC), and (v) no cover (NC) as a control. Six microplots (with a length of 200 cm, width of 80 cm and depth of 80 cm) were subjected to artificial rain during the growing seasons from 2011 to 2013. The variables about runoff and sediment evolution as well as soil water content were studied. Results showed that: (i) the time to runoff initiation was significantly shorter under NC than in other treatments, and the runoff plateau, total runoff volume and sediment yield were highest under NC. Compared with NC, there was over 60% reduction in runoff and 80% reduction in sediment load under other treatments, (ii) runoff and sediment discharge increased linearly under NC before reaching the peak value, while it increased step-wise in the other treatments, (iii) soil water content ( θ ) and soil water storage increase ( SWI ) were significantly greater under BM than others; The 2-year (growing season of 2011 and 2012) mean θ and SWI were the lowest under NC, (iv) overall, BM increased soil water content, and decreased runoff and sediment yield, and thus could potentially solve water shortage and soil erosion problems in rainfed jujube orchards on Chinese Loess Plateau. [ABSTRACT FROM AUTHOR]

Information on soil moisture is important for various agricultural, environmental, and hydrological applications; thus, moisture must be determined with the greatest possible accuracy. In this study, based on the fact that soil changes colour as the moisture content changes, artificial neural networks (ANNs) were applied to estimate the moisture content of tropical soils from colour photographs taken with a digital camera. Three different soils were used to train and test the network, and data were collected from disturbed samples subjected to different water contents in the laboratory. MLP (multilayer perceptron) ANNs with one hidden neuron layer and three input variables (red, green, and blue) related to colour were used. To train the networks, various tests were performed by varying the number of hidden layer neurons and using input data of the three soils. The best performing ANN had a hidden layer with twelve neurons and used the tan-sigmoid transfer function. It was found that a single network could estimate the moisture content of all the soils studied from the photographs. The best ANN, which was trained with data of the three soils simultaneously, was also tested with individual soil data separately, and better results were obtained (RMSE ranging from 0.0321 to 0.0650 g/g and r 2 ranging from 0.6675 to 0.8231). Although the results are satisfactory, the simplicity of the experiment likely restricted a stronger characterisation of the pattern of soil colour variation due to the change in its moisture content, which thus reduced the performance of the method. However, the proposed method represents an advancement in the indirect estimation of soil moisture content because it has the advantages of being practical, rapid, and non-destructive; requiring relatively low cost; and automating the process in the field. [ABSTRACT FROM AUTHOR]

• Modified biochar decreased pH of salt-affected soils in an intercropping system. • Oversupply of biochar had negative impact on soil water and crop yield. • A 10 t ha−1 biochar application rate was recommended to improve soil and yields. Biochar application in agricultural salt-affected soils has shown strong potential to amend soil and promote production. The effect of biochar on soil properties and crop yield varies with crop, soil, biochar properties and climate. Thus, it is critical to select suitable biochar and their application amounts for ameliorating salt-affected soils while improving its conditions and crop yields. The objectives of this study were to investigate the effect of biochar application rates on soil properties, water and temperature conditions and crop yields in saline-alkali soils under cotton-sugarbeet intercropping. We used a three-year (2018–2020) field experiment with biochar application rates of 0, 10, 50 and 100 t ha−1 in 2018, 0, 10, 25, 50 and100 t ha−1 in 2019 and 0, 10, 25 and 30 t ha−1 in 2020. Soil bulk density decreased and thus porosity increased with application of biochar. Soil pH decreased with increasing biochar application amount and the rate of change ranged from −0.003 to −0.004 per ton of biochar. Biochar application at 10 t ha−1 increased soil water content (SWC) and weighted planar soil water storage (WPSWS) in all three experimental years, while oversupply of biochar decreased SWC. Application of biochar moderated soil temperature fluctuations. The yield of cotton and sugarbeet first increased and then decreased with increasing amount of biochar. Considering the effects of biochar on soil water, temperature, and crop yields, 10 t ha−1 biochar amount was proposed as an appropriate application rate for saline-alkali soils. The results provided valuable information on appropriate biochar rates to amend salt-affected soils and their properties while increase crop yields. [ABSTRACT FROM AUTHOR]

• Soil water in 0–1 m soil layer was unevenly distributed and varied by habitat. • Soil water content was lower on habitats with biocrusts than on bare areas. • Soil water content was higher on habitats with subshrub than on bare areas. • Biocrusts had little effect on plant biomass in well-watered habitats. • Soil water in 0–1 m soil layer affected by position of slope-gully system. The landscape position (LP) of slope-gully system (SGS) greatly influences the variations in soil water content, and development of biocrusts and vegetation. It is unclear the relationships between biocrusts, natural successional vegetation, and soil water content in the SGS with different LPs and habitats in semiarid regions. Therefore, this study aimed to clarify the relationships between moss-dominated biocrusts and natural successional A. sacrorum in the utilization of soil water; and investigate their spatial variation characteristics in a typical SGS. Soil water content in the 0–1 m soil layer, and biocrust and vegetation characteristics were measured at the summit, ridge slope, gully slope, and gully floor of an SGS in five habitats (i.e., bare areas (BA), moss-dominated biocrusts (BC), A. sacrorum (AS), A. sacrorum with biocrusts (ASB), and dead A. sacrorum with biocrusts (DASB)). The results showed that plant aboveground biomass and soil water content in the 0–1 m soil layer followed the pattern of DASB < ASB < AS and BC < DASBC≈ASB < BA ≤ AS for the summit, and ridge and gully slopes, respectively. While, those followed the pattern of DASB < ASB≈AS and BC < DASBC≈ASB≈BA≈AS for the gully floor, respectively. Compared to bare lands, soil water content and aboveground biomass were lower in habitats covered by biocrusts, which was likely related to reduced infiltration of biocrusts. This phenomenon was insignificant at the gully floor, which was attributed to the decreasing effect of biocrusts on soil water content with the improvement of water conditions. Soil water content of subshrub covered habitats were slightly higher than those of bare lands, which probably related to the reduced soil evaporation under shading conditions. This study showed that the relationships between biocrusts, subshrubs, and soil water were complex under natural succession conditions, and further observations are needed in the future in semiarid regions. [ABSTRACT FROM AUTHOR]

This study considered the cropland-treebelt-desert system in the arid inland river basin as an entire continuum to investigate the soil water content variation and hydrological relation. For this objective, the volumetric soil water content and plant root distribution was measured to 300 cm depth along a cropland-treebelt-desert site at the oasis-desert ecotone in the Heihe River Basin, China. The results showed that the mean soil water content in the 0–200 cm layer was greater in the cropland (8.88%) than that in the treebelt (5.78%) and desert (4.37%) as a result of frequent irrigation events. However, the cropland had noticeably lower mean soil water content below 200 cm depth (14.27%), compared to treebelt (18.07%) and desert (17.30%) with deeper roots to suck up groundwater. The decline process in soil water content pulse of the cropland and treebelt after irrigation event could be well described by an exponential decay function, and the soil water loss rate was greater in the cropland (0.45–0.70%/day) than that in the treebelt (0.32–0.47%/day). The hydrological relation between treebelt and cropland in the upper soil layer was mainly occurred by treebelt root water uptake from cropland. The biomass of fine treebelt root extended into the cropland decreased logarithmically with the distance from the cropland-treebelt interface, which resulted in the smaller soil water content in the cropland with more proximity to the treebelt. The hydrological relation in the lower soil layer among cropland-treebelt-desert was caused by groundwater recharge, as cropland irrigation raised up the groundwater level to replenish the deep soil layer. The results indicated that the percolation in the cropland was an important water source for the growth of treebelt and desert plants. This study could provide scientific basis for land use pattern design and water resources management in the arid inland river basin. [ABSTRACT FROM AUTHOR]

• SOC higher in the permafrost region than in the non-permafrost region. • Regression-kriging method was the best upscaling approach for the prediction of SOC. • 317 Tg SOC was stored in the entire soil profile of Qinghai Lake watershed. Soil organic carbon (SOC) on the Qinghai-Tibet plateau is of global significance, due to the high carbon density and potential positive feedbacks to climate warming. Qinghai Lake watershed is an important soil pool in Qinghai-Tibet plateau, but the magnitude and characteristics of SOC stock in the high-altitude basin were not clear. To understand better how much SOC was stored and its spatial patterns in the watershed, this study analyzed the vertical variation of SOC content, quantified its influence by varied environmental factors, and further predict its storage in the entire basin. Results showed that, the SOC content decreased with the increasing depth, and was the highest in the alpine meadow in all depths, following by the alpine steppe and temperate steppe, respectively. It was generally higher in the permafrost region than that in the non-permafrost region at all depths. Soil profile depth, soil water content and NDVI could together explain about 72.6% of total variation in SOC density. The regression-kriging method was the best upscaling approach for the prediction of SOC in the study area. Approximately 317 Tg organic carbon was stored in the entire soil profile of Qinghai Lake watershed, in which 136, 140, and 41 Tg were at 0–30 cm, 30–100 cm, and below 100 cm, respectively. The higher SOC density mainly appeared on the northeast and southern region of Qinghai Lake, while the high-altitude area in the northwest of the watershed had the lower values. Moreover, it increased firstly and then decreased with the increase of altitude, with the maximum values at 3350–3400 m, which was dominated by the elevational variation of soil profile depth and NDVI. Overall, the comprehensive assessment of SOC demonstrated high storage and strong heterogenicity of soil carbon in the Qinghai Lake watershed, and it is critical for the sustainability of regional terrestrial ecosystem with future climate change. [ABSTRACT FROM AUTHOR]

[Display omitted] • Biocrusts increase evaporation rate by 10% on average in laboratory experiments. • All types of biocrusts increase evaporation rate by >42% in field experiments. • Biocrusts increase soil moisture (θ) by 9–44% compared with bare soil at 0–10 cm. • Biocrusts decrease soil temperature by 4.7–4.9 °C at 0–10 cm depth after rainfalls. • Reshaped soil properties and increased θ of biocrusts are key factors of increasing E. Soil evaporation is a three-stage process and plays a vital role in soil physical, chemical, and biological processes, as well as global climate change. As an important living skin, biocrusts strongly influence most soil properties and support fundamental ecosystem functions. Although there are many studies concerning biocrust effects on surface soil hydrological processes, it still remains unclear how biocrusts impact soil evaporation and their potential effects on the water budget in drylands. In this study, we selected aeolian sandy soil (bare soil) and three types of biocrusts, specifically cyanobacteria (cyano), cyanobacteria and moss mixed crusts (cyano-moss), and moss crusts (moss), on the northern Chinese Loess Plateau. By utilizing weighing micro-lysimeters in simulated and ∼4 months in-situ field evaporation experiments, we investigated all evaporation stages containing stages I–II and III, as well as the soil evaporation rate (E) of all treatments. The soil moisture (θ) and temperature (T) at 2 cm and 10 cm depths were also measured in field. Our results showed that biocrust types strongly influenced E in the ranked order of moss > cyano-moss > cyano > bare soil. The cumulative evaporation amount (E c) of all types of biocrusts was significantly higher than that of bare soil in simulated experiments. Particularly, moss increased E c by 15.7% compared with bare soil. The results of in-situ field measurements illustrated that the E of cyano, cyano-moss, and moss was increased by 42.4%, 55.5%, and 46.9%, respectively, compared with the bare soil, and these increasing effects became more pronounced after rainfall events. Additionally, all types of biocrusts markedly increased θ and decreased T at 0–10 cm depth of soil, but cyano and cyano-moss increased T (by up to 5.7 °C) at 2 cm depth during the non-rainfall periods. The increasing effects of biocrusts on E were reasonably attributed to their higher contents of fine particles and organic matter, as well as their higher field capacity in contrast to bare soil. All these regulations of biocrusts on soil properties further reshaped soil water and temperature regimes and finally changed soil evaporation. In conclusion, biocrusts may greatly intensify surface soil water loss due to their higher E. However, their greater θ and lower T in comparison to bare soil may partially offset these negative effects in return, and they may have feedback impacts on surface soil water and heat balances in drylands. [ABSTRACT FROM AUTHOR]

• We selected Tibetan Plateau to examine net primary production during 2000–2018. • The NPP in permafrost region had a steadier and faster increasing rate. • Soil water and temperature were the main reasons for NPP changes. • The NPP values will show greater interannual changes in the future. Permafrost affects soil water and soil temperature regimes; however, its effects on net primary production (NPP) remain unknown. Here, we examined temporal-spatial changes in grassland NPP during 2000–2018 in permafrost and permafrost-free areas on the Qinghai–Tibetan Plateau using the random forest (RF) and radial basis function artificial neural network (RBF-ANN). Our results indicated that the areas that showed increasing, decreasing, and non-significant trends for NPP accounted for 13.88%, 1.90%, and 84.22% of the permafrost area, respectively. For the permafrost-free areas, these NPP trends accounted for 22.25%, 2.68%, and 75.07% of the permafrost-free area, respectively. The mean NPP in the permafrost regions showed a faster and steadier (1.520 g C/m2/yr, p < 0.05) increase than in non-permafrost regions (1.224 g C/m2/yr, p < 0.05). The Biome-BGC model confirmed that these spatial NPP patterns could be attributed to differences in soil water and soil temperature between permafrost and permafrost-free areas. Both the soil temperature and soil water content in permafrost sites exhibited relatively lower variance than in permafrost-free sites. Although many factors may be attributed to these patterns, our results suggest that there is a possibility that the relatively stable change in permafrost NPP can be explained by the fact that permafrost can regulate soil water and temperature regimes. Therefore, climate warming can increase NPP in cold regions, and permafrost degradation may destabilize the grassland ecosystem, which may cause NPP values to exhibit greater interannual changes in the future. [ABSTRACT FROM AUTHOR]

Abstract: Soil moisture is one of the most important parameters controlling various critical zone processes including energy balance and nutrient cycling. However, hillslope soil moisture variation and its response to rainfall are not fully understood yet. Through real-time monitoring systems, mechanisms of soil moisture response to rainfall were investigated at top, upper, middle, lower and toe slope positions along a typical mixed land-use hillslope in Taihu Lake Basin, China. The corresponding land use types for these five hillslope position are woodland, tea (Camellia sinensis), tea, meadow and woodland, respectively. This hillslope has annual precipitation around 1100mm. Soil moisture varied from <0.05m3 m−3 at the top slope during the dry period to >0.40m3 m−3 at the toe slope during wet period. Despite different land-use types, similar characteristics of soil moisture response to rainfall were observed at the top (woodland), upper (tea) and middle (tea) slope positions. At these three sites, degrees of soil moisture change (difference between maximum soil moisture during the rainfall and antecedent soil moisture) were significantly (P <0.05) influenced by precipitation amount and intensity, as well as antecedent soil moisture in some cases. However, at the lower slope position (meadow), soil moisture variation during the rainfall was mainly influenced by lateral subsurface flow; the cumulative precipitation was less than the increased soil water storage, indicating that water must come from the upslope areas to recharge this site. At the toe slope position (woodland), precipitation interception by tree canopy and surface organic matter reduced the degree of soil moisture change during rainfall events. Lateral subsurface flow can recharge deep soils at the toe slope position in rainfalls >35mm with relatively wet initial condition (e.g., soil moisture at 0.1-m depth of this site >0.30m3 m−3). Results suggest that lower and toe slope positions are hot spots receiving lateral surface and subsurface recharge. Perennial vegetation at toe slope position can remove nitrogen in lateral subsurface flow by promoting denitrification. Therefore, maintaining toe slope area in perennial vegetation may help to mitigate dissolved nitrogen losses from upslope fertilized tea plantations. [Copyright &y& Elsevier]

Abstract: Spatial patterns of soil water storage (SWS), the total amount of water stored in soil at a given depth interval, tend to be similar if we measure at different times. This is characterized as time stability and can be used to optimize sampling design. The objective of this study was to examine the scale- and season-specific time stability of SWS spatial patterns at seven depth intervals (at every 20cm down to 140cm) in a hummocky landscape. Soil water content was measured 20 times using time domain reflectometry and a neutron probe along a transect of 128 points over a four-year period and converted to SWS by multiplying by the depth intervals. Multivariate empirical mode decomposition (MEMD) was used to decompose the spatial series of SWS into six or seven (depending on depth) components known as intrinsic mode functions (IMFs). Each IMF represents a specific scale of SWS. Spearman's rank correlation coefficients between IMFs from different measurement dates were used to characterize the time stability of SWS at different scales. The variance of each IMF and its ratio to the variance of the original SWS series was calculated. The dominant scale, which has the maximum ratio of variance to the original variances, was 104–128m (IMF5) for the depth intervals of 0–20cm to 60–80cm and 315–412m (IMF7) for the depth intervals of 80–100cm to 120–140cm. Time stability gradually increased with spatial scales and was the strongest at the dominant scale. At any scale, time stability was the strongest within the same season and the weakest between different seasons. This study indicates that MEMD combined with Spearman's rank correlation analysis has great potential for revealing the scale specific time stability of SWS. [Copyright &y& Elsevier]

• Data on retention and hydraulic conductivity for 583 samples from 14 to 115 cm depth. • Corresponding texture and other soil data for 279 samples. • Weekly water content time series at 20, 40, 60, 80 and 100 cm depth from 1282-day study. • Reliable prediction of water content with ANNs that use soil parameters as input. • Accurate prediction of water content with ANNs that use limited water content as input. Quantifying the spatial and temporal dynamics of soil moisture is an important subject in vadose zone hydrology. A 1282-day field study was conducted to provide a hierarchy of data to assess neural network simulations of field soil water content time series θ (t). Volumetric water content was determined, typically once a week, by neutron thermalization at 20-, 40-, 60-, 80- and 100-cm depths. Soil samples were taken at 60 locations between 14- and 114-cm depths to determine soil properties, water retention, and saturated hydraulic conductivity. Prediction of hydraulic parameters from basic and extended soil properties yielded low correlation coefficients. Water content could be predicted reasonably with neural networks from soil properties or hydraulic parameters (0.880 < R < 0.942). Prediction of θ (t) based solely on rainfall data was not accurate. Independent networks could accurately simulate water content from one observed θ (t) based on the Nash-Sutcliffe Model Efficiency and Percent Bias. Once a network is trained for a particular depth, accurate predictions can be made beyond the training period using observations at just one location. [ABSTRACT FROM AUTHOR]

• SWC and NPP increased in most of the study area during summers from 2001 to 2015. • There is a strong correlation between SWC and NPP. • SWC had a significant time lag effect on changes in NPP. • With an increase of 1 °C temperature and 2% precipitation, the positive influence of SWC on vegetation growth weakens. • With future climate change, timely supplementation of SWC can promote growth of NPP. Soil water content (SWC) is the basic condition for the survival of terrestrial vegetation. Net primary productivity (NPP) directly reflects the status of vegetation growth. Therefore, studying the coupling relationship between NPP and SWC in the arid region of Northwest China is of great significance for vegetation restoration and the protection of fragile ecosystems. Based on remote sensing and SWC measured data, the CASA model and statistical downscaling methods were used to calculate the NPP and SWC, analyze the spatial and temporal evolution of them, and to explore their coupling relationship in the Shule River Basin (SRB) in China. Our results indicate that (1) an upward trend in NPP and SWC during the summers of 2001–2015. (2)The NPP and SWC were mainly positively correlated. There was a lag effect in the response of vegetation NPP to SWC in most areas of the basin. However, NPP had a greater impact on SWC in desert areas than in other regions. (3) Based on changes to SWC, two scenarios analyses of NPP were conducted to reveal how NPP responded to SWC. In scenario 1 (the SWC change only), as SWC increases, NPP gradually increases. Scenario 2 (increase of 1 °C temperature and 2% precipitation), compared with scenario 1, as SWC increases, the increase in NPP decreases. Based on the results, in scenario 2, the beneficial effect of SWC on vegetation growth was weakened. Thus, under future climate change, only by timely supplementing SWC can we better promote the growth of NPP, improve vegetation productivity, and effectively restore and protect the ecological environment of SRB. This study deepens our understanding of the coupling relationship between the ecological environment and water resources of the SRB and provides a scientific basis for formulating rational allocation of water resources and ecological environment restoration and protection measures in the arid regions of China. [ABSTRACT FROM AUTHOR]

Rock fragments (RFs, material particles with diameter > 2 mm) are widely distributed in soils over globe. However, spatial pattern of RF content (RFC) and its roles on hydrological and ecological patterns have remained unclear at the global scale. In this study, based on the collected global datasets, we investigated the relationships between mean annual temperature (MAT), mean annual precipitation (MAP), elevation and RFC at 0–5 cm soil depth. In addition, we also examined the links of RFC to representative hydrological and ecological indicators (soil water content or SWC, and normalized difference vegetation index or NDVI, respectively). Results showed that through affecting the pedogenic and morphogenic processes, temperature, precipitation and elevation presented significant relationships with RFC over the globe. When MAT < 20 ℃, RFC decreased with MAT increasing, due to that high temperature could promote RF weathering and thus soil production; while when MAT > 20 ℃, RFC slightly increased with MAT increasing, due to that extreme high temperature induced arid condition would surpass soil production. RFC decreased with MAP increasing, because precipitation increased SWC and hydrologic flow and thus enhanced soil production. In addition, higher elevation zones usually had colder condition and greater loss of fine-textured soils due to erosion, and thus RFC increased with elevation increasing. Furthermore, a RFC threshold of about 0.2 m3 m−3 was identified. When RFC < 0.2 m3 m−3, existence of RFs may improve the soil pore structure and thus water and nutrient retention capacity. Therefore, higher SWC and NDVI were observed. However, when RFC > 0.2 m3 m−3, due to poor soil water and nutrient retention capacity, as well as lower MAT with higher elevation, or lower MAP, lower SWC and NDVI were observed. These findings can supplement the lack of knowledge on RFs and its effects from the global perspective. [ABSTRACT FROM AUTHOR]

Abstract: Changes in vegetation and soil hydrological resources occur in southern Spain because of the presence of a pluviometric gradient from west (1100mmyear−1) to east (240mmyear−1). Five hillslopes under different rainfall regimes were selected along this gradient and studied over a 4-year period. The objectives of the work were to analyze variation in soil moisture, water availability for plants, and drying processes on the hillslopes, and relationships between these factors and the annual variability of vegetation cover. The results show that clay content is a key factor defining the limit of water availability in the soil (the wilting point). Significant differences between soil moisture/available water and vegetation cover were observed, defining a positive feedback process that varied in nature along the pluviometric gradient. The more arid the climatic conditions the weaker the feedback between water content and vegetation cover. These observations can be explained by the greater water requirements of plant species growing on the more humid hillslopes, resulting in a rapid uptake of available water and higher water stress. However, at the driest sites the vegetation species were better adapted to the lack of water and more independent of rainfall. Available water at these sites did not decrease, because the lower number of days with a water deficit resulted in water availability for plants over a longer period of time. [ABSTRACT FROM AUTHOR]

Abstract: Soil water content (SWC) has a vital role in a variety of hydrological processes such as infiltration, runoff and erosion. Mapping the spatial pattern of SWC is then essential for appropriate addressing of these processes. Geostatistics is often used to characterize the spatial variability of SWC. This information may be used for estimating SWC e.g., by ordinary kriging (OK) or modeling location-specific uncertainty (local uncertainty) of the estimates by indicator kriging (IK). Kriging-based algorithms however smooth out the details and are incapable of detecting multi-location uncertainty (spatial uncertainty) of SWC estimates. Sequential Gaussian simulation (sGs) can model the spatial uncertainty through generation of several equally probable stochastic realizations. In this study sGs is used to map SWC spatial distribution and to provide a quantitative measure of its spatial uncertainty in particular. The SWC measurements were performed on 157 soil samples taken from an 18 ha erosion experiment field in Lower Austria. The results show that the spatial pattern of SWC is well recognized using the sGs as the simulated models reproduce the sample statistics including histogram and semivariogram model reasonably well. The difference among realizations is used to provide a quantitative measure of spatial uncertainty of SWC estimates. Knowledge of spatial uncertainty is helpful to evaluate the delineation of vulnerable areas to erosion. [Copyright &y& Elsevier]

• Biocrusts existence affected soil aggregate stability, particle composition and water repellency. • Freeze-thaw cycles affect K s by water repellency and stability of aggregate. • Freeze-thaw cycles reduced hydraulic conductivity of biocrusts in sandy land. Moss-biocrusts (BCs) play an essential role in soil stabilization, but it reduces soil hydraulic conductivity, hindering precipitation convert to soil water. Freeze-thaw cycles (FTCs) is a natural phenomenon, which can alter soil properties, causing widespread concern. However, few studies have focused on the effects of FTCs on hydraulic conductivity in BCs, which may alter the negative effects of BCs on hydraulic conductivity. We conducted an in-situ FTCs simulated experiment in BCs and bare sand (BS), to analyze the response of particle-size composition, water-stable aggregates and water repellency (WR) to FTCs, and their effects on saturated hydraulic conductivity (K s). The results showed that the existence of BCs had affected water-stable aggregates, particle-size composition, WR and K s. Compared with BS, the percentage of clay-size particle content increased by 44% and 60% in BCs layer and its underlying soil, respectively. The stability of water-stable aggregates was 19% higher in BCs than the measured stability in BS. K s of BS was 2.4 times higher than that of BCs, and the increasing percentage of water-stable aggregates larger than 5 mm would reduce K s in sandy land. FTCs had the significant effects on water-stable aggregates, WR and K s. WR and K s of BCs were decreased 57% and 25% after FTCs, respectively. Moreover, after FTCs, the percentage of soil water-stable aggregates > 5 mm reduced 19%, while 1–5 mm increased 18%. WR and sand content were significantly and negatively correlated with K s , while clay content and the percentage of soil water-stable aggregates > 5 mm were significantly and positively correlated with K s in BCs. Our results indicated that BCs and FTCs had a significant and negative effects on K s. FTCs further decreased the hydraulic conductivity, which was not conductive to the supply of meltwater to soil water reservoir in the period of winter and early spring. [ABSTRACT FROM AUTHOR]

• Spatio-temporal variation of soil water content (SWC) was investigated for typical hillslopes. • Representative locations of mean SWC were identified by the methods of relative differences. • Temporal stability of SWC differed notably with slope aspect, position, and soil depth. • Identified representative locations performed well in predicting the mean SWC. • Soil particle and SOC contents greatly affect the spatio-temporal distribution of SWC. Spatio-temporal variability in soil water content (SWC) increases the difficulty in soil water resource management and vegetation construction in arid and semi-arid regions. Our objectives were to investigate the spatial variability and temporal stability of SWC and identify representative locations for reliably predicting the profile mean SWC (MSWC) of a 33-year-old Caragana korshinskii plantation on typical sunny and shady hillslopes on the Loess Plateau, China. The profile SWC (0–180 cm) in three sampling belts and five hillslope positions (upper position, UP; upper-middle position, UMP; middle position, MP; lower-middle position, LMP; lower position, LP) were measured 27 times for both the hillslopes in 2018 and 2019. The mean relative difference (MRD), the standard deviation of the MRD (SDRD), and an index of temporal stability (ITS) were used to identify representative locations of the MSWC. The results indicated that the SWC presented different horizontal but similar vertical change trends in the five hillslope positions. The profile MSWC on the sunny hillslope (8.89%) was lower than that on the shady hillslope (9.44%). The mean Spearman correlation coefficients of the temporal patterns ranged from 0.6 to 0.8 for the five soil layers on both hillslopes. The characteristics of temporal stability differed in both temporal persistence and the representative locations for the five soil layers on the sunny and shady hillslopes. The mean ITS values generally decreased with increasing soil depth. Ultimately, the representative locations for estimating the profile MSWC were determined to be the MP-2 location on the sunny hillslope and the MP-3 location on the shady hillslope based on the MRD, SDRD, and ITS values. The representative locations have the lowest ITS values and represent the MSWC accurately, with root mean square error (RMSE) and mean error (ME) values of less than 1%. In addition, the soil organic carbon, clay, silt, and sand contents greatly affect the spatial and temporal distributions of the soil water at the hillslope scale. Our study provides a rapid and accurate method for determining profile MSWC in C. korshinskii plantations on typical sunny and shady hillslopes and could also support valuable guidance for the rational management of hillslope-scale SWC resources for similar dry regions. [ABSTRACT FROM AUTHOR]

Abstract: This paper investigates the influence of rainfall intensity and initial soil water content on changes in the near-surface soil hydraulic conductivity. While numerous papers have examined surface sealing, this paper outlines two important innovations: the design and application of time-domain reflectometry probes with the ability to measure and record soil water content at very short time and length scales; the design and application of stainless steel tensiometers to measure soil water potential at the same, very short, time and length scales. These permit the Richards Equation to be applied and the near-surface hydraulic conductivity computed. An exponential curve was fitted to the temporal changes in hydraulic conductivity, as both a function of water potential or soil water content, with a high degree of fit. As rainfall intensity increased, the degree of scatter about the best-fit line increased, probably due to the ability of high intensity rainfall to disrupt the near-surface soil structure. While utilising deterministic models, such as the Richards Equation, may be appropriate at the column scale there are practical difficulties due to the very small length scale variability in each of the input variables. The experimental results detailed here indicate that even with data at very short time and length scales it is still not possible to utilize the Richards Equation, or at least, it may be difficult to transfer the laboratory results to the field due to the effect of the specific laboratory experimental conditions on the results. [Copyright &y& Elsevier]

• The activities of earthworms (Pheretima aspergillum) affect the soil water content. • Earthworm increased the water stable aggregates and organic matter contents. • Earthworm cast mulch reduced the soil evaporation. • The evaporation was inhibited depend on the cast mulch thickness and proportion. Earthworms are typical ecosystem engineers because they greatly affect the physical properties of soil in various ways. In this study, simulation experiments were performed to assess the effects of earthworms (Amynthas aspergillum) on the soil evaporation process in a subtropical region of China. Five population sizes CK (0), A1 (0), A2 (10), A3 (20), and A4 (30), four cast mulch thicknesses (0, 1, 2, and 4 cm), and four cast mulch area coverage percentages (0, 30%, 60%, and 90%) were tested with four replicates each for the different treatments. Water was applied again to the treatments until the soil water content reached 20% on day 14. The results showed that earthworms significantly increased the content of water-stable aggregates (WSA), where the WSA contents under different treatments were 35–40.6 g (P < 0.05). The soil water content decreased in the first 13 days after earthworm inoculation, before increasing gradually after adding water again. Compared with CK, the average water contents increased by 45.9–151.2 g in the earthworm treatments. When the number of added earthworms was 30, the water contents were 126.5 g in A3 and 151.2 g in A4 (P < 0.05). Different earthworm cast mulch thickness and area coverage percentages significantly reduced the cumulative evaporation (P < 0.05), where they reduced the cumulative evaporation by 31.2–63.5% and 14.5–29.8%, respectively, compared with CK. When the soil moisture was at a low level, minimal differences were observed in the evaporation rates among the treatments. Thus, the activities of earthworms can improve the soil water-holding ability and inhibit evaporation from lateritic red soil. [ABSTRACT FROM AUTHOR]

• Soil conservation depends on physical, chemical and biological components. • Spatial cross-correlation reveals spatial causalities between two variables. • Environmental radionuclides are spatially related to soil microbiological parameters. • Soil water content connect biodiversity and physicochemical variables. • Dehydrogenase as indicator reveals spatial influence on water retention in soil. Best soil management practices can be achieved by evaluating the spatial cross-correlation variability of soil microbiological and physicochemical indicators, in order to comprehend the underlying relations between these mutually dependent properties, being valuable indicators for prospective evaluation of soil resources. The purposes of this study were to measure microbiological and physicochemical variables in superficial soil, spatially cross-correlate and determine spatial causalities between these two families of variables. The spatial variability of pH, gravimetric soil water content, 238U, 232Th, 40K, 137Cs, acid phosphatase, dehydrogenase activity, microbial biomass carbon, mesophilic aerobic bacteria and filamentous fungi was studied at a 13 ha field located in Uruguay. 238U and 232Th were both negatively lineally correlated with gravimetric soil water content (−0.42), 137Cs (-0.45 and −0.48 respectively) and dehydrogenase activity (-0.44 and −0.48 respectively). A semivariogram analysis revealed that the best fit model for soil variables was spherical, with moderate to strong spatial dependence. Cross-correlation results suggest that there is an influence factor from spatial interaction. In this sense, gravimetric soil water content connects physicochemical variables with soil biodiversity. Spatially, soil water content is inversely influenced by 232Th and 238U (as indicators of sub-superficial soil), and directly influenced by dehydrogenase activity (indicator of soil microbial activity), revealing soil microbial activity as a possible indicator of water retention in drying soils. The combination of spatial patterns of environmental radionuclides with microbiological indicators of soil quality could represent a valuable integrated approach to assess soil conservation status and further explain the impact of anthropogenic disturbance. [ABSTRACT FROM AUTHOR]

• There was low CO 2 efflux and moisture heterogeneity in the oak forest (22 and 13%). • Harvest increased heterogeneity of CO 2 efflux, but had no effect on that of moisture. • Inter-plot heterogeneity of CO 2 efflux was lower than that within plots. • Heterogeneity of CO 2 efflux after harvest was affected by understorey vegetation. Soil respiration is the second largest flux of carbon between terrestrial ecosystems and the atmosphere and it is substantially sensitive to climate change. Monitoring CO 2 efflux and its upscaling from field measurements to the ecosystem level is a complex task, due to the high spatial and temporal variability of the fluxes. Human intervention, e.g. through forest harvest, may change both CO 2 efflux and its spatial heterogeneity. The objective of our study was to quantify spatial heterogeneity of soil CO 2 efflux within and among plots distributed within a topographically variable sessile oak forest stand before and after harvesting. Forest floor CO 2 efflux, soil temperature and soil water content were measured monthly in a sessile oak forest during two growing seasons: one before and one after harvesting. Stand structure characteristics (gap fraction, leaf area index, tree number and size) and the amount of understory also were determined. Relationships between individual variables and spatial heterogeneity were analyzed. The small-scale spatial heterogeneity (expresses as the coefficient of variation) of forest floor CO 2 efflux and soil water content (SWC) in the undisturbed forest was low, at maximum 0.22 and 0.13, respectively. Studied variables had no effect on spatial heterogeneity of forest floor CO 2 efflux except for the amount of understorey vegetation which positively correlated with forest floor CO 2 efflux. Although the studied forest was situated in topographically variable terrain, we observed that inter-plot heterogeneity of forest floor CO 2 efflux was lower than that within plots. Stand harvest increased the intra-plot heterogeneity of forest floor CO 2 efflux but did not affect the inter-plot heterogeneity. This leads to the conclusion that the number of positions within an individual plot should increase after harvest but the number of plots may remain unchanged to determine adequately ecosystem forest floor CO 2 efflux. [ABSTRACT FROM AUTHOR]

• Dynamics of temporal instability was studied using daily temporal stability analysis. • Frequency and degree of temporal instability were depth-dependent. • Temporal instability contributed to a high prediction error under some conditions. • Low-frequency temporal instability did not affect the overall temporal stability. Temporal instability, a condition of soil moisture with unstable spatiotemporal patterns, may occur when the relative roles of the controlling factors change. It impacts the applicability of the temporal stability in the prediction of soil moisture. However, the occurring frequency, degree and underlying hydrological conditions of the temporal instability are far from clear. This study aimed to examine the presence of temporal instability at the hillslope scale and to characterize and quantify the frequency, degree and underlying hydrological conditions contributing to the phenomenon. Sloping crop lands under subtropical hydrological conditions are known for their frequent transition between dry and wet periods and were chosen for this study. Soil moisture was monitored at 5 locations and at seven soil depths down to 2.2 m along a 160 m hillslope over a period of a year. Relative difference analysis was employed to evaluate the temporal stability of soil moisture. Representative locations (RLs) mainly appeared at locations with a mild slope and relatively high sand content. Daily RLs were not consistent among the study period, which has the highest proportion to be the same to those full dataset based. These proportions were depth dependent, the lowest (40%) at moderate soil layers (i.e. 50 and 80 cm) and the highest (95%) at deep soil layers (i.e. 180 and 220 cm). An obvious temporal instability was observed by the extensive ranges in the daily mean relative difference (MRD) values. If the whole dataset was used to calculate the mean soil moisture of the hillslope, it would be overestimated by 16.1% or underestimated by 18.2%. The frequency of temporal instability was low and varied over time and soil depths. For example, 17% of the time for this period was temporally unstable at 20 cm and 2% time of the study period was unstable at 220 cm. These low proportions confirm that the temporal stability remains a valid and robust tool in mean soil moisture prediction. The rainfall after a long drought period or a storm after successive rainfall probably caused the temporal instability. Therefore, caution should be exercised during the strong dry-wet transition period. [ABSTRACT FROM AUTHOR]