Study on the Soil Moisture Stress Level in Regulated Deficit Irrigation Experiment

On the basis of discussing the influencing mode of plant moisture stress on plant physiological process and the division of soil moisture availability range, the water suction values partitioning soil moisture were put forward, and then the corresponding water moistures under water stress were obtained by conversing together with characteristic curve of water moisture.

Enhancing Deep Learning Soil Moisture Forecasting Models by Integrating Physics-based Models

Accurate soil moisture(SM)prediction is critical for understanding hydrological processes.Physics-based(PB)models exhibit large uncertainties in SM predictions arising from uncertain parameterizations and insufficient representation of land-surface processes.In addition to PB models,deep learning(DL)models have been widely used in SM predictions recently.However,few pure DL models have notably high success rates due to lacking physical information.Thus,we developed hybrid models to effectively integrate the outputs of PB models into DL models to improve SM predictions.To this end,we first developed a hybrid model based on the attention mechanism to take advantage of PB models at each forecast time scale(attention model).We further built an ensemble model that combined the advantages of different hybrid schemes(ensemble model).We utilized SM forecasts from the Global Forecast System to enhance the convolutional long short-term memory(ConvLSTM)model for 1–16 days of SM predictions.The performances of the proposed hybrid models were investigated and compared with two existing hybrid models.The results showed that the attention model could leverage benefits of PB models and achieved the best predictability of drought events among the different hybrid models.Moreover,the ensemble model performed best among all hybrid models at all forecast time scales and different soil conditions.It is highlighted that the ensemble model outperformed the pure DL model over 79.5%of in situ stations for 16-day predictions.These findings suggest that our proposed hybrid models can adequately exploit the benefits of PB model outputs to aid DL models in making SM predictions.

Time-lagged Effects of the Spring Atmospheric Heat Source over the Tibetan Plateau on Summer Precipitation in Northeast China during 1961–2020:Role of Soil Moisture

The spring atmospheric heat source(AHS)over the Tibetan Plateau(TP)has been suggested to affect the Asian summer monsoon and summer precipitation over South China.However,its influence on the summer precipitation in Northeast China(NEC)remains unknown.The connection between spring TP AHS and subsequent summer precipitation over NEC from 1961 to 2020 is analyzed in this study.Results illustrate that stronger spring TP AHS can enhance subsequent summer NEC precipitation,and higher soil moisture in the Yellow River Valley-North China region(YRVNC)acts as a bridge.During spring,the strong TP AHS could strengthen the transportation of water vapor to East China and lead to excessive rainfall in the YRVNC.Thus,soil moisture increases,which regulates local thermal conditions by decreasing local surface skin temperature and sensible heat.Owing to the memory of soil moisture,the lower spring sensible heat over the YRVNC can last until mid-summer,decrease the land–sea thermal contrast,and weaken the southerly winds over the East Asia–western Pacific region and convective activities over the South China Sea and tropical western Pacific.This modulates the East Asia–Pacific teleconnection pattern,which leads to a cyclonic anomaly and excessive summer precipitation over NEC.

Synergistic Impacts of Indian Ocean SST and Indo-China Peninsula Soil Moisture on the 2020 Record-breaking Mei-yu

The Yangtze River basin(YRB)experienced a record-breaking mei-yu season in June‒July 2020.This unique long-lasting extreme event and its origin have attracted considerable attention.Previous studies have suggested that the Indian Ocean(IO)SST forcing and soil moisture anomaly over the Indochina Peninsula(ICP)were responsible for this unexpected event.However,the relative contributions of IO SST and ICP soil moisture to the 2020 mei-yu rainfall event,especially their linkage with atmospheric circulation changes,remain unclear.By using observations and numerical simulations,this study examines the synergistic impacts of IO SST and ICP soil moisture on the extreme mei-yu in 2020.Results show that the prolonged dry soil moisture led to a warmer surface over the ICP in May under strong IO SST backgrounds.The intensification of the warm condition further magnified the land thermal effects,which in turn facilitated the westward extension of the western North Pacific subtropical high(WNPSH)in June‒July.The intensified WNPSH amplified the water vapor convergence and ascending motion over the YRB,thereby contributing to the 2020 mei-yu.In contrast,the land thermal anomalies diminish during normal IO SST backgrounds due to the limited persistence of soil moisture.The roles of IO SST and ICP soil moisture are verified and quantified using the Community Earth System Model.Their synergistic impacts yield a notable 32%increase in YRB precipitation.Our findings provide evidence for the combined influences of IO SST forcing and ICP soil moisture variability on the occurrence of the 2020 super mei-yu.

Antecedent Precipitation Index to Estimate Soil Moisture and Correlate as a Triggering Process in the Occurrence of Landslides

Landslides are highly dangerous phenomena that occur in different parts of the world and pose significant threats to human populations. Intense rainfall events are the main triggering process for landslides in urbanized slope regions, especially those considered high-risk areas. Various other factors contribute to the process;thus, it is essential to analyze the causes of such incidents in all possible ways. Soil moisture plays a critical role in the Earth’s surface-atmosphere interaction systems;hence, measurements and their estimations are crucial for understanding all processes involved in the water balance, especially those related to landslides. Soil moisture can be estimated from in-situ measurements using different sensors and techniques, satellite remote sensing, hydrological modeling, and indicators to index moisture conditions. Antecedent soil moisture can significantly impact runoff for the same rainfall event in a watershed. The Antecedent Precipitation Index (API) or “retained rainfall,” along with the antecedent moisture condition from the Natural Resources Conservation Service, is generally applied to estimate runoff in watersheds where data is limited or unavailable. This work aims to explore API in estimating soil moisture and establish thresholds based on landslide occurrences. The estimated soil moisture will be compared and calibrated using measurements obtained through multisensor capacitance probes installed in a high-risk area located in the mountainous region of Campos do Jordão municipality, São Paulo, Brazil. The API used in the calculation has been modified, where the recession coefficient depends on air temperature variability as well as the climatological mean temperature, which can be considered as losses in the water balance due to evapotranspiration. Once the API is calibrated, it will be used to extrapolate to the entire watershed and consequently estimate soil moisture. By utilizing recorded mass movements and comparing them with API and soil moisture, it will be possible to determine thresholds, thus enabling anticipation of landslide occurrences.

Research Progress of Evaluation Index of Soil Moisture

In modern agriculture, accurate and effective measurements of soil water content lays foundation for promotion on precision irrigation technology and improvement on water use efficiency. The research reviewed soil moisture indices at home and abroad and classified the indices into two categories in order to make prediction on soil moisture and take measures. Specifically, single indices included precipitation index, soil moisture index, and crop drought index and overall indices included supply/demand water index of crops, overall water index, PDSI, crop water shortage index. Soil moisture index was analyzed in terms of advantages and disadvantages,as well as adaptability in agriculture, providing references for relieving and predicting adverse effects on agriculture and formulating scientific policies.

An evaluation of soil moisture from AMSR-E over source area of the Yellow River, China

In this study,in-situ soil moisture measurements are used to evaluate the accuracy of three AMSR-E soil moisture prod ucts from NASA(National Aeronautics and Space Administration),JAXA(Japanese Aerospace Exploration Agency)and VUA(Vrije University Amsterdam and NASA)over Maqu County,Source Area of the Yellow River(SAYR),China.Re sults show that the VUA soil moisture product performs the best among the three AMSR-E soil moisture products in the study area,with a minimum RMSE(root mean square error)of 0.08(0.10)m3/m3 and smallest absolute error of 0.07(0.08)m3/m3 at the grassland area with ascending(descending)data.Therefore,the VUA soil moisture product is used to describe the spatial variation of soil moisture during the 2010 growing season over SAYR.The VUA soil moisture product shows that soil moisture presents a declining trend from east south(0.42 m3/m3)to west north(0.23 m3/m3),with good agreement with a general precipitation distribution.The center of SAYR presents extreme wetness(0.60 m3/m3)dur ing the whole study period,especially in July,while the head of SAYR presents a high level soil moisture(0.23 m3/m3)in July,August and September.

Influence of Vegetation Coverage on Surface Runoff and Soil Moisture in Rainy Season in Dry-hot Valley

[Objective]The research aimed to study the effects of vegetation coverage on the changes of soil moisture in rainy season in dry-hot valley.[Method]The surface runoff and soil moisture of slope with vegetation coverage and bare land in rainy reason in Jinsha River at Yuanmou County of Yunnan Province were observed continuously.Moreover,the statistical analysis was made based on the observation data.[Result]The vegetation coverage could decrease surface runoff and the surface runoff on bare land（CK） was 22 times as the plot with vegetation coverage.The soil water content in 0-180 cm layer with vegetation coverage increased by 37.8% than bare land.The stability of soil moisture content in deep layer was enhanced and the physical properties stability of soil was maintained.The soil moisture content in different depth of soil had significant difference and the changes of soil moisture content were obviously different.[Conclusion]The vegetation coverage of slope could change the soil hydrology obviously and keep soil moisture at the higher level,especially at soil layer below 20 cm.

Spatial and temporal variations of soil moisture in three types of agroforestry boundaries in the Loess Plateau, China

Agroforestry is a ubiquitous landscape on the slopes in Loess Plateau, where soil moisture is a limiting factor for plant growth and development. The spatial and temporal characteristics of soil moisture were studied in three types of agroforestry boundaries： forest-grassland, forest-cropland and shelterbelt-cropland. The result shows that soil moisture content decreased with soil depth increasing from the surface to 110 cm. Soil moisture content differed significantly among the three boundaries all in the rainy season （July-September）, dry season （May-June） and spring （March-April）. The horizontal distribution of soil moisture in different soil layers in the three types of boundaries showed different patterns with line form, wave form, scoop form or ＂W＂ form. The distance of edge influence （DEI） of soil moisture in different types of landscape boundaries was estimated by variance analysis and multiple comparisons. In dry season the DEI in 0-10 cm soil layer was 0.4 H （H, average height of trees）, which ranged from 0.2 H in grassland or in cropland to 0.2 H in forest field for both forest-grassland and forest-cropland boundaries, and 0.7 H （ranged from 0.2 H in cropland to 0.5 H in forest field） for shelterbelt-cropland boundary. In rainy season the DEI at soil depth of 0-110 cm was 0.7 H for the three boundaries. The results indicated that agroforestry type should be carefully selected to maintain soil moisture in land management, especially in restoring degraded land in Loess Plateau.

Architectural Plasticity in Response to Soil Moisture in the Stoloniferous Herb, Duchesnea indica

Architectural plasticity of clonal plants may enhance exploitation of soil moisture heterogeneity by the plants. The plasticity of clonal architecture in response to soil moisture in the stoloniferous herb, Duchesnea indica Focke, was investigated in an experiment with different soil moisture contents as treatments, i.e. 40%, 60%, 80%, 100% of the maximum moisture content of soil (MMCS). As soil moisture content increased, the spacer length, ramet density, branching intensity and branching angle of D. indica plants changed by quadratic curve. And the optimum habitat for the plants was at 80% of the MMCS. This architectural plasticity in D. indica was simulated through the Dynamic Logistic Model. The imitative effect was statistically satisfactory. Its architectural plasticity observed here may allow the species to show foraging behavior in its habitat where soil moisture is patchily distributed.

Effect of soil moisture gradient on structure of broad-leaved/Korean pine forest in Changbai Mountain

A 112 m×8 m sample pot which includes 14 sub-plots was set up along the slope in Hongshi Forestry Farm of Baihe Forestry Bureau (127°55′E, 42°30′ N), Jilin Province in August 2002. Community structure, soil moisture contents at 0–10 cm and 10–20 cm in depth, water content of litter as well as the contents of C, N and P of litter, living leaves and branches in the broad-leaved/Korean pine (Pinus korraiensis) forest were measured in each sub-plot on different slope positions. The analytical results showed that there existed an obvious soil moisture gradient along the slope: upper slope <middle slope< lower slope. The difference in soil moisture contents on different positions of slope led to a change of the stand structure of the braod-leaved/Korean pine forest. The proportion ofQuercus mongolica gradually increased with the decrease of soil moisture content and that of other major tree species in the broad-leaved/Korean pine forest gradually decreased or disappeared. The dynamic of soil moisture contents in the litter layer was as same as that in mineral soils. The decomposition rates of the litter on different slope positions were different and the dry weights of existent litter varied significantly. The soil nutrients in the litter on the lower slope was richer than that on the upper slope due to the different stand structure on the different slope positions. The moisture content and nutrient contents of soil had effects on the composition, decomposition, and the nutrient release of litter, thus affecting stands growth and stand structure and finally leading to the change of ecosystem. Key words Soil moisture gradient - nutrient - Stand structure - Broad-leaved/Korean pine forest CLC number S718.5 Document code A Foundation item: This study was supported by the NKBRSF (G1999043407-1), Tackle Key Problem of Science and technology of China (2001BA510B-07), Knowledge Innovation Program of the Chinese Academy of Sciences (KZCX2-406, SCXZD0101), NKTRDP (2001BA510B-07. 2002BA516A20).Biography: WANG Yan (1970-), female, Ph. D, associate professorResponsible editor: Song Funan

Soil Moisture Variation under Different Irrigation Quota

[Objective] The aim was to study variation of soil moisture under different irrigation quota.[Method] By using Trime-TDR apparatus,soil moisture with different irrigation quota infiltration was measured;combining the characteristics of soil texture,curve characteristics of soil moisture variation with soil depth under different irrigation quota were analyzed.[Result] Different irrigation quota has resulted in variation of soil moisture in different layer depth.Soil moisture is 9.88%,17%,25% and 24.45% in so...

The runoff characteristics and harmonic analysis of the soil moisture dynamics in Robinia pseudoacacia stand

Robinia pseudoacacia stands act as a typical ecological protection forest in hilly semi-arid area of China. Two fields of surface runoff were separately set up in R. pseudoacacia stand and its clearcut area in the western Liaoning Province (1850-12225 E, 4024-4234 N) for measuring the characteristics of runoff and sediment as well as soil moisture dynamics. Contractive analysis of the two land types showed that there existed a significant difference in volumes of runoff and sediment between the sites of R. pseudoacacia stand and its clearcut area. The runoff volume and sediment volume in clearcut area were much bigger than those in R. pseudoacacia stand, with an increase amount of 40%-177% for runoff and 180%-400% for sediment. Hydrograph of surface runoff of typical rainfall showed that the peak value of runoff in R. pseudoacacia stand was decreased by 1.0-2.5?0-3m3s-1 compared with that in its clearcut area, and the occurring time of peak value of runoff in R. pseudoacacia stand was 10-20 min later than that in its clearcut area. Harmonic analysis of soil moisture dynamics indicated that the soil moisture in R. pseudoacacia stand was 2.3 % higher than that in clearcut area, and the soil moisture both in R. pseudoacacia stand and its clearcut area could be divided into dry season and humid season and varied periodically with annual rainfall precipitation. It was concluded that R. pseudoacacia stand plays a very important role in storing water, increasing soil moisture, and reducing surface runoff and soil erosion.

Variability of Soil Moisture and Its Relationship with Surface Albedo and Soil Thermal Parameters over the Loess Plateau

Data from July 2006 to June 2008 observed at SACOL （Semi-Arid Climate and Environment Observatory of Lanzhou University, 35.946°N, 104.137°E, elev. 1961 m）, a semi-arid site in Northwest China, are used to study seasonal variability of soil moisture, along with surface albedo and other soil thermal parameters, such as heat capacity, thermal conductivity and thermal diffusivity, and their relationships to soil moisture content. The results indicate that surface albedo decreases with increases in soil moisture content, showing a typical exponential relation between the surface albedo and the soil moisture. The heat capacity, the soil thermal diffusivity, and soil thermal conductivity show large variations between Julian day 90-212 and 450-578. The soil thermal conductivity is found to increase as a power function of soil moisture. Soil heat capacity and soil thermal diffusivity increase with increases in soil moisture. The SACOL observed soil moisture are also used to validate the AMSR-E/AQUA retrieved soil moisture and there is good agreement between them. The analysis of the relationship between satellite retrieved soil moisture and precipitation suggests that the variability of soil moisture depends on the variation of precipitation over the Loess Plateau.

Diagnostic Analysis of Soil Moisture in Northeast China

The horizontal distribution and vertical distribution characteristics of monthly average soil moisture(10-100 cm)of northeastern region of China in 22 years(1981-2002)were analyzed.The spatial and temporal variations also were analyzed.The results showed that from 1981 to 2002,the northeast region surface(10-60 cm)of soil moisture show a downward trend,while the deep(60 cm)following an upward trend.The vertical structure of soil moisture of different years was different.Rainfall was one possible reason for ...

The Response of Transpiration Rate of Malus pumila cv.Goldspur to Illumination and Soil Moisture

We tested the transpiration rate ( Tr ) of seven\|year\|old field and two\|year\|old potted Malus pumila cv.Goldspur under different conditions of illumination and soil water. The results showed that the interrelationship between Tr of Malus pumila cv.Goldspur and illumination and soil water content ( SWC ) was quite remarkable. Tr increased with the increase of light intensity and SWC . However, when one of the environmental stresses of illumination and water existed, the improvement of the other condition couldn't make Tr rise greatly. Only when SWC was higher than 11%, which arrived at over 55% of the field content ( FC ), or the photosynthetic active radiation ( PAR ) higher than 400?μmol·s -1 m -2 , Tr could rise greatly with the increase of PAR or SWC . But when SWC was higher than 15%, which reached over 75% of FC or PAR higher than 1?000?μmol·s -1 ·m -2 , Tr would not change a lot with the change of PAR or SWC . That PAR and SWC influenced the magnitude of stomatic resistance( RS ) and leaf water potential ( Ψ l) was the basic reason for the Tr responded to them. Light stress reduced the open degree of stomas, so when severe light stress existed ( PAR <100?μmol·s -1 ·m -2 ), RS was larger ( RS >2 0?s·cm -1 ), which led to the decrease of Tr(Tr <5?μgH 2O·s -1 ·cm -2 ). When severe water stress existed( SWC <11% and<55% of FC and soil water potential Ψ ws <-1 15?MPa), RS was higher than 4 00?s·cm -1 and Ψ l lower than -2 10?MPa, which led to Tr lower than 11?μgH 2O·s -1 ·cm -2 . When soil water was adequate( SWC >15% amd over 75% of FC , and Ψ ws >-0 50?MPa), RS was lower than 2 00?s·cm -1 , Ψ l higher than -1 65?MPa and Tr would be higher than 15?μgH 2O·s -1 ·m -2 . The range of SWC , 11%～15%, which accounted for 55% to 75% of FC , and correspond RS (2 00～4 00?s·cm -1 ) were the turning area, where the variable curve of Tr transited from a variable trend to another variable one. It could be considered as the range to control soil water.

Soil Moisture Characteristics in Karst Area with Different Land Use Types

Ecological efficiency changes of soil moisture were researched in karst areas with different land type uses, including farmland, abandoned farmland （1 y） and shrub land （1 y）, sparse wood land （15 y）, secondary forest （25 y） and the re- sults showed that physical property of soil was not a simple ＂improvement＂ process during land type evolution. Specifically, from farmland to secondary forest, the con- tent of topsoils changed from being washed away to accumulation and soil bulk density changed from increasing to decreasing. For example, soil bulk densities of abandoned farmland and shrub land increased by 6.6% and 11.57% compared with farmland, and of sparse wood land and forest land decreased by 5.0% and 10.0%. The change trend of soil bulk density was just in contrary to total porosity. Available water capacity was the lowest of shrub land, but increased in rest land types. The increase tended to be volatile in 5.1%-12.5% of different land types and water-sta- ble aggregate content （〉0.25 mm） reached the highest of sparse wood land. The destruction rate, however, was declining in the process of land type evolution and the increase was in the range of 34.0%-64.7% compared with farmland. The de- struction rate of aggregate was of negative correlation with organic matter. Water- holding capacity was the best of forest land and abandoned farmland and the poor- est of shrub land, close to sparse wood land. Water-supplying capacity from high to low was as follows： farmland〉sparse wood land〉secondary forest〉shrub land〉a- bandoned farmland. It is obvious that water-holding capacity and water-supplying capacity are not consistent, but both are closely related to the content of soil clays, porosity, and aggregate stability.

Effects of Different Illumination Intensity and Soil Moisture on Seed Germination of Parashorea chinensis

Objective] This study almed to soIve technical probIems in artificial breed-ing of Parashorea chinensis. [Method] The effects of different iI umination intensity and soiI moisture on seed germination rate and emergence of P. chinensis were in-vestigated. [Result] Under conditions of ill umination intensity of 40% and soiI mois-ture of 60%, the seeds of P. chinensis showed the highest germination rate. [Con-clusion] This study wiI provide some basic information for the ex-situ conservation, repopuIation and deveIopment and utiIization of P. chinensis.

Validation and application of soil moisture active passive sea surface salinity observation over the Changjiang River Estuary

Using sea surface salinity(SSS)observation from the soil moisture active passive(SMAP)mission,we analyzed the spatial distribution and seasonal variation of SSS around Changjiang River(Yangtze River)Estuary for the period of September 2015 to August 2018.First,we found that the SSS from SMAP is more accurate than soil moisture and ocean salinity(SMOS)mission observation when comparing with the in situ observations.Then,the SSS signature of the Changjiang River freshwater was analyzed using SMAP data and the river discharge data from the Datong hydrological station.The results show that the SSS around the Changjiang River Estuary is significantly lower than that of the open ocean,and shows significant seasonal variation.The minimum value of SSS appears in July and maximum SSS in December.The root mean square difference of daily SSS between SMAP observation and in situ observation is around 3 in both summer and winter,which is much lower than the annual range of SSS variation.In summer,the diffusion direction of the Changjiang River freshwater depicted by SSS from SMAP is consistent with the path of freshwater from in situ observation,suggesting that SMAP observation may be used in coastal seas in monitoring the diffusion and advection of freshwater discharge.

Research on the effect of straw mulching on the soil moisture by field experiment in the piedmont plain of the Taihang Mountains

To reveal the influencing effect of the long-term straw mulching on the soil moisture, this paper employed the field experiment data in 2010 of a typical area of Taihang Mountains plain, observed the soil moisture dynamic regularities under different mulching patterns by virtue of depressimeter and neutron probe, analyzed the characteristics of soil water content and storage in different depths and seasons under the long-term straw mulching. The results showed that the long-term straw mulching can keep the soil moisture conservation of the deep, while decreased the shallow.(1) The long-term straw mulching can changed the type of soil water movement. If no straw mulching, the type is mainly evaporation-infiltration. And with straw mantle the type would change into infiltration. The number of zero flux plane would be reduced or absent.(2) The long-term straw mulching can increase the soil water reserves of the whole soil profile with the depth between 0 cm and 220 cm. But the soil water content of the layer from 30 cm to 80 cm decreased and the soil water content of the layer from 80 cm to 220 cm increased instead., The effect of soil moisture conservation on winter wheat is not obvious;(3) With no straw mulching, the depth of infiltration recharge by rainfall or irrigation is shallower than 80 cm. In a straw mulching, the influence depth is can extend to 120 cm;(4) With no straw mulching, there is a deep layer on the depth of 220 cm between March and June, while this layer will disappear with a long-term straw mulching.