Spatiotemporal Variations Of Soil Moisture Research Articles

Effects of Rainfall and Plant Characteristics on the Spatiotemporal Variation of Soil Moisture in a Black Locust Plantation (Robinia pseudoacacia) on the Chinese Loess Plateau

Soil moisture is a key factor controlling vegetation construction and ecological restoration in arid and semiarid areas. Understanding its spatiotemporal patterns and influencing factors is essential for effective vegetation water management. In this study, we analyzed the spatiotemporal characteristics of black locust plants using field investigations and statistical analyses and determined the effects of the rainfall and plant characteristics on the soil moisture content (SMC) in a typical watershed in the Loess Plateau, China. The results show that the SMC increases with increasing distance from the tree trunk in the horizontal direction. The vertical profile of the SMC includes layers characterized by rapid decrease, decreased fluctuation, and slow increase. Temporal SMC changes exhibit higher variabilities in the surface layer than in deeper soil layers. Rainfall characteristics notably affect soil moisture. The influence of the rainfall amount is stronger than that of the rainfall duration and intensity. The diameter at breast height, tree height, and canopy width positively affects the soil moisture, whereas the leaf area index and canopy openness negatively affect it. The results of this study provide insights into soil moisture change mechanisms and theoretical references for sustainable plant water use management in arid and semiarid areas.

Spatiotemporal Characteristics of Soil Moisture and Land–Atmosphere Coupling over the Tibetan Plateau Derived from Three Gridded Datasets

Soil moisture is a crucial component of the water cycle and plays an important role in regional weather and climate. However, owing to the lack of In Situ observations, an accurate understanding of the spatiotemporal variations of soil moisture (SM) on the Tibetan Plateau (TP) is still lacking. In this study, we used three gridded SM products to characterize the spatiotemporal features of SM on the TP during the warm season (May to August). We analyzed the fifth-generation European Centre for Medium-Range Weather Forecasts atmospheric reanalysis (ERA5), Global Land Data Assimilation System (GLDAS), and Soil Moisture Active Passive (SMAP) datasets and used station observation data and triple collocation to quantify product accuracy and consistency. Results of the evaluation based on observation data show that both ERA5 and GLDAS overestimate SM, while the accuracy of SMAP is high. In terms of capturing the temporal variations of SM measured at stations, the performance of ERA5 and that of SMAP are superior to that of GLDAS. According to the evaluation based on triple collocation, SMAP exhibits the smallest random error over the TP and the highest temporal correlation with the unknown true SM in eastern TP. For SMAP, SM variability is the largest in the southern TP. For ERA5 and GLDAS, variability in the western TP is substantially larger than that for SMAP. Low-frequency (30–90 days) variations are the largest contributor to TP SM intraseasonal variability. Relative to SMAP, the contribution of high-frequency variations is low in ERA5 and GLDAS. Land-atmosphere coupling is stronger (weaker) in the western (southeastern) TP, which is relatively dry (wet). Our evaluation of SM product performance over the TP may facilitate the use of these products for disaster monitoring and climate and hydrological studies.

Spatiotemporal Variations of Soil Moisture and Groundwater Level in a South Sumatra Peatland, Indonesia During 2015–2018

The peat hydrological unit of the Air Sugihan River – Air Saleh River, South Sumatra, Indonesia, experienced extreme fires during the 2015 El Niño event. Restoration of 2.0 Mha degraded peatlands has been conducted since 2016. This study aims to analyze spatiotemporal variations of soil moisture content and groundwater level in this site from 2015 to 2018. The soil moisture was estimated using a multiple regression analysis method based on the Sentinel-1A and the European Center for Medium-Range Weather Forecast dataset. The groundwater level model was calculated by using linear regression between the estimated soil moisture and water level observed from field measurements. A minimum moisture content of ~0.78 m3m-3 and a minimum groundwater depth of ~0.50 m below the peat surface were estimated to cause smoldering combustion. A sharp decline in the water table depth (around 1.53 m) led to a decrease in moisture content in October 2015. This month, peat fires severely burned both cultivation and protected areas having dense drainage canals and near rivers. Although there was an increasing trend in the groundwater level and moisture content in 2016, between 2017 to 2018 the water table declined to a depth of ~0.7 m with a corresponding moisture content of ~0.25 m3m-3. Such decline may have led to a few peat fires which occurred in the dry season of both 2017 and 2018. We recommended that law enforcement efforts should be conducted to raise the mean annual water table to shallower depths than 0.40 m

Effects of Different Irrigation Regimes on Spatio-Temporal Variations of Soil Moisture and Cotton Growth in Non-Film Drip Irrigation Cotton Fields in Southern Xinjiang, China

Effects of Different Irrigation Regimes on Spatio-Temporal Variations of Soil Moisture and Cotton Growth in Non-Film Drip Irrigation Cotton Fields in Southern Xinjiang, China

Investigating the Spatio-Temporal Variation of Soil Moisture and Agricultural Drought towards Supporting Water Resources Management in the Red River Basin of Vietnam

The increasing serious droughts recently might have significant impacts on socioeconomic development in the Red River basin (RRB). This study applied the variable infiltration capacity (VIC) model to investigate spatio-temporal dynamics of soil moisture in the northeast, northwest, and Red River Delta (RRD) regions of the RRB part belongs to territory of Vietnam. The soil moisture dataset simulated for 10 years (2005–2014) was utilized to establish the soil moisture anomaly percentage index (SMAPI) for assessing intensity of agricultural drought. Soil moisture appeared to co-vary with precipitation, air temperature, evapotranspiration, and various features of land cover, topography, and soil type in three regions of the RRB. SMAPI analysis revealed that more areas in the northeast experienced severe droughts compared to those in other regions, especially in the dry season and transitional months. Meanwhile, the northwest mainly suffered from mild drought and a slightly wet condition during the dry season. Different from that, the RRD mainly had moderately to very wet conditions throughout the year. The areas of both agricultural and forested lands associated with severe drought in the dry season were larger than those in the wet season. Generally, VIC-based soil moisture approach offered a feasible solution for improving soil moisture and agricultural drought monitoring capabilities at the regional scale.

Spatiotemporal variation of soil moisture in Northern China based on climate change initiative data

AbstractIn view of the sparse, uneven distribution and poor data continuity of measured soil moisture sites in China and the lack of large‐scale research, the soil moisture data set of the European Space Agency (ESA) Climate Change Initiative (CCI) was applied to carry out spatial‐temporal variation analysis of soil moisture in five agricultural ecological zones in Northern China. The Pearson correlation coefficient and multiple‐component metric Kling–Gupta efficiency were used to verify the validity of remote sensing data and to analyze the temporal and spatial variation of soil moisture with the concept of temporal and spatial persistence. The ESA CCI remote sensing soil moisture data had good spatial and temporal adaptability for the whole year in the Huang‐Huai‐Hai region, in summer in Northeast China, in spring in Northwest China, in summer and autumn in the Loess Plateau, and in summer and autumn in the Inner Mongolian Plateau. The annual mean soil volume water content in Northern China from 1991 to 2016 was 0.06–0.39 m3 m−3. Spatially, soil moisture in Northern China has been gradually increasing from west to east. In this area, seasonally, soil moisture was the highest in summer, followed by autumn and then winter and spring. Northeast China, the Loess Plateau, and the Huang‐Huai‐Hai region are important grain‐producing areas in China. The soil moisture in these areas fluctuates widely with seasonal changes and shows an obvious drying trend.

基于VIC模型模拟的干旱区土壤水分及其时空变化特征

基于VIC模型模拟的干旱区土壤水分及其时空变化特征

Spatio-temporal variation of soil moisture in a fixed dune at the southern edge of the Gurbantunggut Desert in Xinjiang, China

Soil moisture is critical for vegetation growth in deserts. However, detailed data regarding the soil moisture distribution in space and time in the Gurbantunggut Desert of China have not yet been reported. In this study, we conducted a series of in situ observation experiments in a fixed sand dune at the southern edge of the Gurbantunggut Desert from February 2014 to October 2016, to explore the spatio-temporal variation of soil moisture content, investigate the impact of Haloxylon ammodendron (C. A. Mey.) Bungeon soil moisture content in its root zone, and examine the factors influencing the soil moisture spatial pattern. One-way analysis of variance, least significant difference tests and correlation analysis were used to analyze the data. The results revealed that the soil moisture content exhibited annual periodicity and the temporal variation of soil moisture content throughout a year could be divided into three periods, namely, a moisture-gaining period, a moisture-losing period and a moisture-stable period. According to the temporal and spatial variability, the 0–400 cm soil profile could be divided into two layers: an active layer with moderate variability and a stable layer with weak variability. The temporal variability was larger than the spatial variability in the active layer, and the mean profile soil moisture content at different slope positions displayed the trend of decreasing with increasing relative height and mainly followed the order of interdune area>west and east slopes>slope top. The mean profile soil moisture content in the root zone of dead H. ammodendron individuals was significantly higher than that in the root zones of adult and young individuals, while the soil moisture content in the root zone of adult individuals was slightly higher than that in the root zone of young individuals with no significant difference. The spatial pattern of soil moisture was attributable to the combined effects of snowfall, vegetation and soil texture, whereas the effects of rainfall and evaporation were not significant. The findings may offer a foundation for the management of sandy soil moisture and vegetation restoration in arid areas.

How spatiotemporal variation of soil moisture can explain hydrological connectivity of infiltration-excess dominated hillslope: Observations from lesser Himalayan landscape

This study demonstrated the spatiotemporal variation in runoff generating areas in grassed and agro-forested hillslopes of Lesser Himalaya using soil moisture, soil hydraulic conductivity and rainfall datasets. Nine rainfall events of infiltration-excess dominated hillslopes were analysed and found that only high-intensity rainfall events were able to convert 1–5% of runoff at the outlet. The extremely low patch of soil hydraulic conductivity (<5 mm/h) was located at the outlet in agro-forested hillslope whereas similar low soil hydraulic conductivity patch is located at the end portion in a grassed hillslope. Therefore, the grassed hillslope generated less runoff than the agro-forested hillslope due to its surface resistance and heterogeneity in soil hydraulic conductivity. The runoff generated from the upper part of hillslope re-infiltrated into the middle part due to higher soil hydraulic conductivity. During low and medium intensity rainfall conditions, major runoff contribution was observed from low conductivity zones of the hillslope. Moreover, we analysed the correlation of spatial variation in soil moisture with topographic wetness index (TWI) and soil hydraulic conductivity in two different landuse conditions to examine the predictive potential of these attributes during the wet and dry season. The optimal formulation of TWI was obtained from 72 different combinations using linear mixed effects modelling. The correlation between optimal TWI formulation and soil moisture was found to be negative as the main streamline is located near low conductivity zones. Furthermore, the correlation between TWI and soil moisture is stronger in the dry season than the wet season. In comparison to grass cover hillslope, agro-forested landuse system shows better negative correlation between soil moisture and TWI during the wet season as the agro-forested hillslope produced more runoff than the grassed hillslope. The correlation strength of soil hydraulic conductivity and soil moisture was strongest after mid of the wet season which is directly correlated to the moisture content of hillslopes.

Towards water-saving irrigation methodology: Field test of soil moisture profiling using flat thin mm-sized soil moisture sensors (MSMSs)

This study examined flat thin mm-sized soil moisture sensors (MSMS) fabricated using thermal press technology on thin compact disc (CD) to solve the long-standing problems of soil moisture profiling. The 10-month field tests conducted at a farm site compared three groups of MSMS with commercial capacitance-type soil moisture sensors (SMS) in terms of accuracy, sensitivity to environmental variations (e.g. water shock, temperatures, dry/wet seasons) and long-term stability. MSMS sensors were mounted on the shallow, middle and deep locations of a hollow plastic rod (length: 1.1 m) and installed along the soil depth to profile the soil moisture variation. The resistance readings of MSMS sensors along soil depth were recorded in a real-time mode. Due to soil settlement over time after installation, the MSMS sensors in the shallow soil suffered from unstable readings, while the MSMS sensors in the middle and deep soil exhibited high stability and had the best correlation with water content values of commercial sensors (R2 value: 0.6264). The contact between MSMS surface and soil particles appeared to be a critical factor determining the stability of MSMS readings. In addition, MSMS sensors showed a prompt response to the sharp change of soil moisture in the water shock tests. The soil moisture profiles collected from MSMS sensors captured the spatiotemporal variation of soil moisture, which enabled the simultaneous profiling at multiple locations. This field study demonstrated the great potential of mass deployment of low-cost but accurate MSMS sensors to achieve high resolution profiling for water-saving irrigation.

Understanding shallow soil moisture variation in the data-scarce area and its relationship with climate change by GLDAS data.

Quantitatively evaluating the spatiotemporal variation of soil moisture (SM) and its causes can help us to understand regional eco-hydrological processes. However, the complicated geographical environment and the scarce observation data make it difficult to evaluate SM in Northwest China. Selecting the Tarim River Basin (TRB) as a typical representative of the data-scarce area in Northwest China, we conducted an integrated approach to quantitatively assess the spatiotemporal variation of shallow soil moisture (SSM) and its responses to climate change by gathering the earth system data product. Results show that the low-value of SSM distributes in Taklamakan Desert while the high-value basically distributes in the Pamirs and the southern foothill of Tianshan Mountains, where the land types are mostly forest, grassland, and farmland. Annual average SSM of these three land types present a significant increasing trend during the study period. SM at 0–10 cm of all land types are positively correlated to precipitation in spring and autumn, and SM at 0–10 cm in the forest, grassland, and farmland are positively correlated with temperature in winter. SSM presents in-phase relation with precipitation whereas it presents anti-phase relation with temperature, with the significant resonance periods about 6–8 years and 2–3 years which mainly distribute from 1970s to early 1990s and 1960s respectively. The time lags of SSM relative to temperature change are longer than its lags relative to precipitation change, and the lags vary from different land types.

Investigating Spatial and Temporal Variation of Hydrological Processes in Western China Driven by CMADS

The performance of hydrological models in western China has been restricted due to the scarcity of meteorological observation stations in the region. In addition to improving the quality of atmospheric input data, the use hydrological models to analyze Hydrological Processes on a large scale in western China could prove to be of key importance. The Jing and Bortala River Basin (JBR) was selected as the study area in this research. The China Meteorological Assimilation Driving Datasets for the SWAT model (CMADS) is used to drive SWAT model, in order to greatly improve the accuracy of SWAT model input data. The SUFI-2 algorithm is also used to optimize 26 sensitive parameters within the SWAT-CUP. After the verification of two runoff observation and control stations (located at Jing and Hot Spring) in the study area, the temporal and spatial distribution of soil moisture, snowmelt, evaporation and precipitation were analyzed in detail. The results show that the CMADS can greatly improve the performance of SWAT model in western China, and minimize the uncertainty of the model. The NSE efficiency coefficients of calibration and validation are controlled between 0.659–0.942 on a monthly scale and between 0.526–0.815 on a daily scale. Soil moisture will reach its first peak level in March and April of each year in the JBR due to the snow melting process in spring in the basin. With the end of the snowmelt process, precipitation and air temperature increased sharply in the later period, which causes the soil moisture content to fluctuate up and down. In October, there was a large amount of precipitation in the basin due to the transit of cold air (mainly snowfall), causing soil moisture to remain constant and increase again until snowmelt in early spring the following year. This study effectively verifies the applicability of CMADS in western China and provides important scientific and technological support for the spatio-temporal variation of soil moisture and its driving factor analysis in western China.

Impact of Different Yearly Rainfall Patterns on Dynamic Changes of Soil Moisture of Fixed Sand Dune in the Horqin Sandy Land

The in-situ monitoring method was used for studying the spatio-temporal variation of soil moisture in the growing season of different precipitation years in fixed dunes of Horqin Sandy Land. The results showed that different precipitation years have a certain influence on both seasonal variation and vertical variation of soil moisture in the fixed dunes of the study area. (1) During the normal year, the seasonal variation of soil moisture was relatively flat. During the dry year, the soil moisture gradually decreased before the rainy season and increased significantly after the rainy season. During both normal and dry years, heavy rainfall can significantly recharge the soil moisture content in all soil layers. During the wet year, the rapid recharge effect of soil moisture from heavy rainfall in the shallow layer was better than that in the deep layer. (2) During the normal and wet years, the soil moisture was at a relatively low level in May and changed little with the soil depth. In different months of other precipitation years, the soil moisture changes with soil depth all showed the trend of “first increase, then decrease, and finally slow increase”. Higher soil moisture were generally in the soil layer of 30∼70 cm, the soil moisture below 70 cm changed little with the soil depth and tended to be stable below 110 cm. (3) Under the influence of heavy rainfall, the vertical variation of soil moisture tended to be active in the wet year, showing three variation layers, i.e. quickly changing layer, active variable layer and sub-active variable layer. During the normal and dry years, the soil moisture showed small vertical changes, and it was divided into only two layers. For the dry year, only the surface layer showed active variation of soil moisture; for the normal year, the soil layer above 70cm showed active variation of soil moisture.

The Spatiotemporal Response of Soil Moisture to Precipitation and Temperature Changes in an Arid Region, China

Soil moisture plays a crucial role in the hydrological cycle and climate system. The reliable estimation of soil moisture in space and time is important to monitor and even predict hydrological and meteorological disasters. Here we studied the spatiotemporal variations of soil moisture and explored the effects of precipitation and temperature on soil moisture in different land cover types within the Tarim River Basin from 2001 to 2015, based on high-spatial-resolution soil moisture data downscaled from the European Space Agency’s (ESA) Climate Change Initiative (CCI) soil moisture data. The results show that the spatial average soil moisture increased slightly from 2001 to 2015, and the soil moisture variation in summer contributed most to regional soil moisture change. For the land cover, the highest soil moisture occurred in the forest and the lowest value was found in bare land, and soil moisture showed significant increasing trends in grassland and bare land during 2001~2015. Both partial correlation analysis and multiple linear regression analysis demonstrate that in the study area precipitation had positive effects on soil moisture, while temperature had negative effects, and precipitation made greater contributions to soil moisture variations than temperature. The results of this study can be used for decision making for water management and allocation.

Spatial Pattern and Temporal Stability of Root-Zone Soil Moisture during Growing Season on a Larch Plantation Hillslope in Northwest China

Soil moisture plays a decisive role for tree growth and forest ecosystems services supply in dryland regions. Hence, it is necessary to clarify the spatio-temporal variation of soil moisture under field conditions. This study selected a hillslope in the Liupan Mountains covered by the plantation of Larix principis-rupprechtii Mayr (larch), a main afforestation tree species in north and northwest China. The volumetric soil moisture (VSM) in root zone layers was monitored with a time interval of about 15 days during the growing season (from May to October) in 2016 at 48 points on this hillslope. The aim was to evaluate the spatial pattern and temporal stability of soil moisture at slope scale. The results showed a moderate spatial variability of VSM in each soil layer, with the variation coefficients range of 17.12–22.63%. The spatial variability of VSM showed a dependence on the soil wetness and a threshold effect, it increased with rising VSM until the VSM reached a threshold of about 15%, but thereafter decreased. The mean relative difference (MRD) among the 48 points ranged from −30.56% to 27.20%, −29.89% to 39.58%, and −28.13% to 33.71% for the soil layers of 0–20, 20–40, and 40–60 cm, respectively. The associated standard deviation (SDRD) (and range) was 11.38% (5.20–26.06%), 8.28% (4.64–15.63%), and 6.51% (2.00–14.16%) for the soil layers of 0–20, 20–40, and 40–60 cm, respectively. The high Spearman’s rank coefficients (p &lt; 0.05) among the measuring dates at each soil layer indicated that the spatial distribution of VSM in the root zone had strong temporal stability. The decrease of Spearman’ rank correlation coefficient and mean SDRD with rising soil depth indicated an increasing temporal stability of VSM with rising soil depth. The mean VSM of the three soil layers on the entire hillslope can be estimated by the direct method (using representative points determined by the index of temporal stability (ITS)) successfully, and these representative points determined by ITS were mainly located at the points with a ratio of field capacity to leaf area index (LAI) close to the slope mean. Moreover, the mean VSM of the three soil layers on the entire hillslope can also be estimated by indirect method (using the time-stable points determined by mean absolute bias error (MABE) and considering the offset between slope mean VSM and observed VSM at time-stable points), and the prediction accuracy of the indirect method was better than the direct method. Significant correlation between MRD and soil bulk density, field capacity, capillary porosity, and LAI were observed for all soil layers, indicating that both the water-retention ability in root zone soil (expressed mainly by field capacity) and water-consumption ability of trees (expressed mainly by canopy LAI) are the main factors controlling the spatial pattern of root-zone VSM on the larch plantation hillslope studied.

Changes of Soil Moisture from Multiple Sources during 1988–2010 in the Yellow River Basin, China

Soil moisture is a key variable in terrestrial water cycle, playing a key role in the exchange of water and energy in the land-atmosphere interface. The spatiotemporal variations of soil moisture from multiple sources during 1988–2010 are evaluated against in situ observations in the Yellow River basin, China, including the Essential Climate Variable satellite’s passive microwave product (SMECV), ERA-Interim reanalysis (SMERA), the National Centers for Environmental Prediction/Department of Energy’s Reanalysis-2 (SMNCEP), and the Variable Infiltration Capacity model products (SMVIC). The seasonal soil moisture dynamics ofSMECVandSMVICappear to be consistent withSMin situ, with significant soil drying in spring and wetting in summer.SMERAandSMNCEP, however, fail to capture the soil drying before rainy seasons. Remarkably,SMECVshows large agreement withSMin situin terms of the interannual variations and the long-term drying trends.SMVICcaptures the interannual variations but fails to have the long-term trends inSMin situ. As forSMERAandSMNCEP, they fail to capture both the interannual variations and the long-term soil drying trends inSMin situ.

不同龄阶梭梭根区土壤水分时空变化特征

不同龄阶梭梭根区土壤水分时空变化特征

Present status of soil moisture estimation by microwave remote sensing

AbstractThe spatiotemporal distribution of soil moisture is a key variable for hydrological and meteorological applications that influences the exchange of water and energy fluxes at the land surface/atmosphere interface. Accurate estimate of the spatiotemporal variations of soil moisture is critical for numerous large-scale environmental studies. Recent technological advances in satellite remote sensing have shown that soil moisture can be measured by a variety of remote sensing techniques, each with its own strengths and weaknesses which minimizes the ill-posed conventional problems. Technical and methodological advances such as multi-configuration radar and forthcoming SAR constellations are increasingly mitigating the shortcomings of SAR with respect to soil moisture estimation at the field and catchment scale. This paper presents a comprehensive review of few selected inversion methods of soil moisture, with focus on technique in passive microwave and active microwave measurements, in addition to the...

Spatiotemporal variations of soil moisture in the Tarim River basin, China

Based on in situ soil moisture and river runoff records in the Tarim River basin, usability of the long term Essential Climate Variable (ECV) soil moisture dataset is validated in the arid climatic region of China. The spatio-temporal variation of soil moisture and its possible influencing factors in the 1988–2013 is also preliminary analyzed in the current paper. Results reveal that the ECV soil moisture can capture the large scale dynamics of regional water cycle quite satisfactorily, showing good agreement with in situ observations in their seasonal and interannual variability. In the period of 1988–2013, the ECV soil moisture shows obvious increasing trends in the northwest and the southwest parts of the Tarim River basin, particularly in spring (March–May) and autumn (September–November). Statistical analysis further suggests that the variations of soil moisture in the Tarim River basin are more controlled by precipitation, and temperature is less effective in controlling of soil moisture variations.

喀斯特峰丛洼地区坡地不同土地利用方式下土壤水分的时空变异特征

喀斯特峰丛洼地区坡地不同土地利用方式下土壤水分的时空变异特征