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There is growing interest in using canopy temperature (Tc), including crop water Stress index (CWSI), for irrigation management. However, Tc varies greatly in one day, while soil water content (SWC) varies little, which may lead to different conclusions on whether irrigation is needed based on CWSI at different times. For this end, Tc of winter wheat was continuously monitored, and the data of such environmental factors as atmospheric temperature and soil water content (SWC) were simultaneously collected. CWSI was calculated based on empirical formulation and Tc and CWSI were generalized based on the normalization formulation. The correlation SWC between Tc and CWSI before and after generalization was compared and error analysis was based on SWC theoretical formula. The results showed: (1) the accuracy of SWC retrieval by Tc and CWSI increased firstly and then decreased with time during the day. The optimal time for Tc monitoring SWC was between 10:00 ~ 16:00 (R2 > 0.72) and the optimal time for CWSI monitoring SWC was between 9:00 ~ 18:00 (R2 > 0.69). (2) CWSI and Tc were mapped based on the relationship between crop water stress and soil water deficit and normalized canopy temperature expressions characterized the relationship between crop water stress and soil water deficit. (3) The accuracy of inversion of SWC by mapping Tc from 18:00 ~ 8:00 is increased from 0.5 ~ 0.6 to 0.7 ~ 0.8; the accuracy of soil water content inversion by mapping CWSI from 18:00 ~ 8:00 was improved from 0.2 ~ 0.4 to 0.4 ~ 0.6. (4) The theoretical expression of SWC deduced based on CWSI also proves that considering the relationship between crop water stress and soil water deficit change can effectively reduce the relative error from 30 to 5% in the morning and evening. This study contributes to the understanding of the reason why the correlation between Tc and SWC varies greatly during the day and solves the time-limited problem of thermal infrared remote sensing monitoring of crop water stress. [ABSTRACT FROM AUTHOR]

Increases in hydrological extremes, including drought, are expected for Amazon forests. A fundamental challenge for predicting forest responses lies in identifying ecological strategies which underlie such responses. Characterization of species-specific hydraulic strategies for regulating water-use, thought to be arrayed along an 'isohydric–anisohydric' spectrum, is a widely used approach. However, recent studies have questioned the usefulness of this classification scheme, because its metrics are strongly influenced by environments, and hence can lead to divergent classifications even within the same species. Here, we propose an alternative approach positing that individual hydraulic regulation strategies emerge from the interaction of environments with traits. Specifically, we hypothesize that the vertical forest profile represents a key gradient in drought-related environments (atmospheric vapor pressure deficit, soil water availability) that drives divergent tree water-use strategies for coordinated regulation of stomatal conductance (gs) and leaf water potentials (ΨL) with tree rooting depth, a proxy for water availability. Testing this hypothesis in a seasonal eastern Amazon forest in Brazil, we found that hydraulic strategies indeed depend on height-associated environments. Upper canopy trees, experiencing high vapor pressure deficit (VPD), but stable soil water access through deep rooting, exhibited isohydric strategies, defined by little seasonal change in the diurnal pattern of gs and steady seasonal minimum ΨL. In contrast, understory trees, exposed to less variable VPD but highly variable soil water availability, exhibited anisohydric strategies, with fluctuations in diurnal gs that increased in the dry season along with increasing variation in ΨL. Our finding that canopy height structures the coordination between drought-related environmental stressors and hydraulic traits provides a basis for preserving the applicability of the isohydric-to-anisohydric spectrum, which we show here may consistently emerge from environmental context. Our work highlights the importance of understanding how environmental heterogeneity structures forest responses to climate change, providing a mechanistic basis for improving models of tropical ecosystems. [ABSTRACT FROM AUTHOR]

Background: Soil water content is one of the critical indicators in agricultural systems. Visible/near-infrared hyperspectral remote sensing is an effective method for soil water estimation. However, noise removal from massive spectral datasets and effective feature extraction are challenges for achieving accurate soil water estimation using this technology. Methods: This study proposes a method for hyperspectral remote sensing soil water content estimation based on a combination of continuous wavelet transform (CWT) and competitive adaptive reweighted sampling (CARS). Hyperspectral data were collected from soil samples with different water contents prepared in the laboratory. CWT, with two wavelet basis functions (mexh and gaus2), was used to pre-process the hyperspectral reflectance to eliminate noise interference. The correlation analysis was conducted between soil water content and wavelet coefficients at ten scales. The feature variables were extracted from these wavelet coefficients using the CARS method and used as input variables to build linear and non-linear models, specifically partial least squares (PLSR) and extreme learning machine (ELM), to estimate soil water content. Results: The results showed that the correlation between wavelet coefficients and soil water content decreased as the decomposition scale increased. The corresponding bands of the extracted wavelet coefficients were mainly distributed in the near-infrared region. The non-linear model (ELM) was superior to the linear method (PLSR). ELM demonstrated satisfactory accuracy based on the feature wavelet coefficients of CWT with the mexh wavelet basis function at a decomposition scale of 1 (CWT(mexh_1)), with R2, RMSE, and RPD values of 0.946, 1.408%, and 3.759 in the validation dataset, respectively. Overall, the CWT(mexh_1)-CARS-ELM systematic modeling method was feasible and reliable for estimating the water content of sandy clay loam. [ABSTRACT FROM AUTHOR]

Purpose: Land use changes influence soil porosity, soil water, and heat transport, which may alter freeze–thaw characteristics within the soil profile. However, the response to freeze–thaw process after long-term land use change in Northeast China is still unclear. Thus, this study explored the characteristics and dynamics of soil hydrothermal during the freeze–thaw process in Northeast China. Materials and methods: The investigation focused on grassland and bare land that have undergone a long-term transformation from cropland. The soil temperature (ST) and soil water content (SWC) data during the freeze–thaw period were collected from 2016 to 2021. Characteristics of ST and SWC at 0–180 cm soil depth were carried out in two sites during the freeze–thaw period. Results: It was found that soil in the bare land started to freeze and thaw earlier than that in the grassland. The bare land exhibited a 10.3–186.2% higher amplitude in ST at different depths and greater thermal efficiency between air and soil. In both study sites, the SWC showed a downward–stable–upward trend at different soil layers during the monitoring period. The migrated SWC in most soil layers decreased in two sites. The maximum amount of migrated water reached 2.11 and 5.14 mm in grassland and bare land, respectively. The SWC correlated exponentially with absolute temperature in two sites but decreased faster at 0–30 cm depths in the same temperature interval in bare land. Conclusions: The soil in the grassland had more stable water and heat regulation ability than that in the bare land. Our results contribute to improving the comprehension of the relationship between water and heat in different land uses in seasonal frozen regions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Soil & Water Conservation (1009-2242) is the property of Institute of Soil & Water Conservation and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Precise soil water content (SWC) measurement is crucial for effective water resource management. This study utilizes the Cosmic-Ray Neutron Sensor (CRNS) for area-averaged SWC measurements, emphasizing the need to consider all hydrogen sources, including time-variable plant biomass and water content. Near Mead, Nebraska, three field sites (CSP1, CSP2, and CSP3) growing a maize–soybean rotation were monitored for 5 (CSP1 and CSP2) and 13 (CSP3) years. Data collection included destructive biomass water equivalent (BWE) biweekly sampling, epithermal neutron counts, atmospheric meteorological variables, and point-scale SWC from a sparse time domain reflectometry (TDR) network (four locations and five depths). In 2023, dense gravimetric SWC surveys were collected eight (CSP1 and CSP2) and nine (CSP3) times over the growing season (April to October). The N0 parameter exhibited a linear relationship with BWE, suggesting that a straightforward vegetation correction factor may be suitable (fb). Results from the 2023 gravimetric surveys and long-term TDR data indicated a neutron count rate reduction of about 1% for every 1 kg m−2 (or mm of water) increase in BWE. This reduction factor aligns with existing shorter-term row crop studies but nearly doubles the value previously reported for forests. This long-term study contributes insights into the vegetation correction factor for CRNS, helping resolve a long-standing issue within the CRNS community. [ABSTRACT FROM AUTHOR]

In recent decades, distributed temperature sensing (DTS) has emerged as a robust technology for environmental applications, enabling high‐resolution temperature measurements along fibre optic cables (FOCs). The actively heated fibre optic (AHFO) method is employed to monitor soil moisture (θ$$ \theta $$, m3 m−3), wherein the soil temperature subsequent to the application of a heat pulse is measured by a DTS (AHFO‐DTS approach). Despite significant improvements in the application of AHFO‐DTS under controlled and natural conditions, the thermal behaviour of soil during multiple saturation–natural drying cycles has been insufficiently evaluated. This study aimed to address this gap by constructing an experimental horizontal soil profile in the laboratory for the application of the AHFO‐DTS method during two successive saturation–drainage–evaporation (SDE) cycles. Three heating strategies were applied to a metallic alloy in contact with a FOC, and calibration models were used to correlate θ$$ \theta $$ with the thermal conductivity (λ$$ \lambda $$), cumulative temperature increase (Tcum$$ {T}_{\mathrm{cum}} $$), and maximum temperature increase (Tmax$$ {T}_{\mathrm{max}} $$). The results indicated that during the second SDE cycle, the highest errors in θ$$ \theta $$ estimates were observed with the low power‐short heat pulse, whereas the application of the low power‐long duration and high power‐short duration pulses improved the accuracy of calculations. Additionally, errors in θ$$ \theta $$ estimates escalated under wetter conditions, attributed to a shift in soil heat transfer capacity from the first to the second SDE cycle for θ$$ \theta $$ > 0.10 m3 m−3. This behaviour was ascribed to thermal hysteresis, arising from the contact resistance of the FOC and the alloy with the surrounding soil. Furthermore, the Tmax$$ {T}_{\mathrm{max}} $$ method exhibited the least sensitivity to this effect and yielded reliable θ$$ \theta $$ estimates, thus its adoption is recommended. Moreover, the use of the low power‐long duration heating strategy is suggested as it promotes a trade‐off between energy saving and accurate estimates. We concluded that assessing soil thermal response under multiple SDE cycles enhances the comprehension of the AHFO‐DTS method. Overall, our findings provide insights into enhancing the applicability of this approach under field conditions, particularly following irrigation schedules and natural rainfall events. [ABSTRACT FROM AUTHOR]

The relationship between plant aboveground biomass and diversity typically follows a unimodal pattern, showing a positive correlation in resource‐poor habitats and a negative correlation in resource‐rich environments. Precipitation is a crucial resource for both plant biomass and diversity in terrestrial ecosystems. However, the impact of precipitation changes on the relationship between plant biomass and diversity remains unclear. We conduct a water addition field experiment in a semiarid grassland and identify a unimodal relationship between plant biomass and species richness under ambient conditions. Water addition delays the declining phase of this unimodal curve and shift it upward compared to ambient conditions. Our meta‐analysis of water addition experiments conducted across major biomes worldwide (grassland, shrubland, desert, and forest) supports this finding, while water reduction does not alter the biomass–diversity relationship. Water addition increases biomass in all climate but only increases species richness in arid and semiarid climate. Similarly, water reduction decreases biomass in all climate but only reduces species richness in arid and semiarid climate. Species richness in dry subhumid and humid climate does not change significantly. Furthermore, our field experiment shows that water addition increases plant diversity while decreasing soil inorganic nitrogen levels. The increase in one resource, such as water, leads to the scarcity of another, such as nutrient, thus postponing the declining phase of the plant biomass–diversity relationship typically observed in resource‐rich habitats. Our research contributes to predicting the plant biomass–diversity relationship under changing precipitation conditions and highlights the complex interplay between water availability, nutrient level, and plant diversity. [ABSTRACT FROM AUTHOR]

Copyright of Arid Zone Research / Ganhanqu Yanjiu is the property of Arid Zone Research Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Our study area, Ejina, is located in the southern Gobi Desert, Inner Mongolia, China, where the annual precipitation is <50 mm and the annual potential evaporation is >3,600 mm. The Heihe River flows from the Qilian Range through the study area, and the desert landscape along the river includes oases formed by forests and grasslands. We established a survey area of approximately 1.5 ha in grassland facing a seasonal swamp, a branch of the Heihe River. We posed the following questions in this desert grassland: (1) how do soil water content (SWC) and salinity change with distance from the riverbank? (2) How do vegetation, aboveground biomass, and species richness change with distance from the riverbank? (3) How much can be supplied to grazing animals, and how many animals can be grazed? Our results indicated that (1) the SWC is high within 20 m of the riverbank and low beyond 20 m, the standing biomass is positively correlated with SWC, but there was no evidence of a correlation between salinity and distance to water; the electrical conductivity was high both inland and adjacent to the riparian swamp. (2) Vegetation could be classified to six classes, following a gradient from the riverbank (swamp margin) to the dry inland area beyond 20 m from the riverbank. Species richness and aboveground biomass were highly correlated. Classification result led us to recommend that generalist species tolerant of the distinct moisture gradient in the site be used in restoration efforts. (3) Per‐hectare aboveground biomass was 478.93 dry weight (dw) kg, 321.2 ha of equivalent grassland would be required to graze 100 goats annually. [ABSTRACT FROM AUTHOR]

Purpose: Subtropical lake riparian ecosystems experience seasonal water table fluctuations and increased nitrogen (N) deposition with changing N composition. However, the interplay of soil water content (SWC), N deposition chemical composition, and their interaction on plant growth through regulating N acquisition remains poorly understood. Methods: In this controlled experiment with a sedge species Carex thunbergii, we investigated two treatment factors: (1) SWC at 100%, 60%, and 30% of field capacity, combined with (2) N treatments with NH4+:NO3− ratios of 1:3, 2:2, and 3:1. Treatment verifications were conducted using 15N isotope tracer (15NH4NO3 and NH415NO3) technology. Results: Results showed a notable trend of reduced biomass of C. thunbergii with increasing NH4+: NO3− ratio, especially under high SWC conditions. This negative effect of a high NH4+: NO3− ratio on plant biomass accumulation also aligned with reduced N use efficiency (NUE). Conversely, C. thunbergii exhibited accelerated N uptake with increasing SWC, with the most pronounced response observed in the treatment of NH4+: NO3− ratio of 3:1. Principal component analyses provided evidence for SWC-dominated functional coordination between plant below- and aboveground parts in mediating plant N acquisition, while correlation analyses revealed that NUE mainly contributed to belowground productivity of C. thunbergii. Conclusions: Our findings suggest that manipulating water table (as a proxy of SWC) and managing soil NH4+: NO3− ratios could optimize the productivity of this sedge species in riparian ecosystem. The coordination of leaf-root trait highlights the necessity to integrate above- and belowground traits for a comprehensive understanding of plant N acquisition strategies. Understanding plant N acquisition and use efficiency may help us better predict the potential impacts of future climate change components on ecosystem functions. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of China Rural Water & Hydropower is the property of China Rural Water & Hydropower Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

The differences in soil water content across the soil profiles produce changes in soil microbial and enzymatic properties, which play a major role in the transformation of soil organic matter. Permanent water saturation contributes to the formation of gleyic/stagnic horizons which have reducing conditions, this leads to a depletion in soil oxygen and changes in soil properties. To assess the effect of water content, we compared soil properties in the gleyic/stagnic horizons to the oxidative layers, which occurred at the same/similar depth in other profiles. The enzymatic activity and the number of microbial groups were assessed in eight soil profiles located in central Poland. The studied properties responded differently to the water content. As expected, nitrate-reductase activity and the nitrate content were significantly higher in gleyic/stagnic than in oxidative conditions, while the opposite trend was found for phenol oxidase, urease, N -acetyl-glucosaminidase activity and the fungi number. No clear response in the total bacteria and facultative anaerobic bacteria (Bfa) count toward oxidation-reduction conditions was found. The dehydrogenases did not have a higher activity in the gleyic/stagnic as compared to the oxidative horizons and did not correlate significantly with the Bfa count. Differences in enzyme activities may be caused by the fact that the variation in frequency and duration of the reducing conditions in the soils may be insufficient to affect the short-term dynamics of these enzymes. The higher activity of some hydrolases in the reducing horizons may also be associated with the greater carbon and nitrogen content in these horizons. [ABSTRACT FROM AUTHOR]

[Objective] To investigate the spatial variability of trail soils under the influence of anthropogenic trampling in the understory social activities in karst areas. [Methods] To investigate the spatial and temporal variability of soil properties in the 0—20 cm soil layer under drought and precipitation conditions, we took the karst forest trail area as the research object, regularly sampled the soil at a fixed piont on a monthly scale. Geostatistical analyses were performed to assess the spatial and temporal variability of soil properties and their distribution patterns under both drought and precipitation conditions. [Results] Anthropogenic trampling can alter the structure of the soil surface (0—15 cm) and subsurface by increasing soil consolidation and the aggregation capacity of soil particles. The spatial distribution of soil water content in karst forests trails showed moderate variability, with higher values observed in the center of the trails (32.68%) compared to the trail edges (28.46%) and the forest interior (26.99%). Soil compactness and shear strength followed a similar pattern, being highest at the center of the trail, followed by the trail edge, and lowest in the forest interior. Vegetation cover was weakened by anthropogenic trampling, resulting in an increased response time of soil water content to rainfall events. Stochastic factors had a relatively greater influence on soil surface water content but overall showed strong spatial autocorrelation (0.97). Kriging contour plots revealed patchy distribution patterns for soil moisture along forest trails, which exhibited better spatial continuity under precipitation conditions. [Conclusion] Substantial guidance for the implementation of woodland ecological restoration strategies and the development of more accurate soil sampling density programmers in karst areas.

The actively heated fiber-optic (AHFO) technology has become emerged as a research focus due to its advantages of distributed, real-time measurement and good durability. These attributes have led to the gradual application of AHFO technology to the water content measurement of in situ soil. However, all existing in situ applications of AHFO technology fail to consider the effect of soil–sensor contact quality on water content measurements, limiting potential for the wider application of AHFO technology. To address this issue, the authors propose a method for determining the soil–sensor thermal contact resistance based on the principle of an infinite cylindrical heat source. This is then used to establish an AHFO water content measurement technology that considers the thermal contact resistance. The reliability and validity of the new measurement technology are explored through a laboratory test and a field case study, and the spatial-temporal evolution of the soil water content in the case is revealed. The results demonstrate that method for determining the soil–sensor thermal contact resistance is highly effective and applicable to all types of soils. This method requires only the moisture content, dry density, and thermal response of the in situ soil to be obtained. In the field case, the measurement error of soil water content between the AHFO method, which takes into account the thermal contact resistance, and the neutron scattering method is only 0.011. The water content of in situ soil exhibits a seasonal variation, with an increase in spring and autumn and a decrease in summer and winter. Furthermore, the response of shallow soils to precipitation and evaporation is significant. These findings contribute to the enhancement of the accuracy of the AHFO technology in the measurement of the water content of in situ soils, thereby facilitating the dissemination and utilization of this technology.

• Marula transpiration is strongly driven by both climatic and soil water content variations. • Marula can buffer daily transpiration demands via large water storage capacity. • Kei Apple transpiration is predominantly driven by climatic factors. • Whole-tree transpiration can be accurately predicted using a simple Penman-Monteith model, albeit with different parameters for each species. Conventional crop production is expected to decline in the future in sub-Saharan Africa due to the rising costs of inputs, soil degradation, and increasing water scarcity related to climate variability and change. South Africa has more than 30 species of indigenous fruit trees that are adapted to grow under harsh conditions, yet these species are currently underutilized. Their cultivation is constrained by the lack of detailed ecophysiological information required to develop effective management strategies that optimize tree performance. In this study we investigated how two species with domestication potential namely Marula (Sclerocarya birrea) and Kei apple (Dovyalis caffra) responded to climate and soil factors over a period of two years (2019–2021). Photosynthesis, transpiration, and yield were quantified for mature trees growing in experimental orchards in the Mpumalanga Province of South Africa. Leaf gas exchange data were collected at selected intervals during the growing season using an infrared gas analyser while whole tree transpiration rates were quantified using the heat ratio method of monitoring sap flow. These data were used to parameterize a big leaf Penman-Monteith (PM) model to estimate the transpiration dynamics of individual trees at the daily time step. S. birrea's transpiration responded strongly to both climatic and soil water content variations while the water use of D. caffra was driven mostly by climatic factors. Transpiration rates averaged 0.30 L/m2 of leaf area for S. birrea while that of D. caffra was around 0.45 L/m2. Both species exhibited significant alternate bearing with yield of individual trees fluctuating by more than 50 % between successive years. For the 2019/20 season, water productivity (grams of fruit per litre of water transpired) varied between 6.2 and 17.4 g/L for S. birrea and between 24.3 and 41.7 g/L for D. caffra. Whole tree transpiration by both species were accurately predicted using the PM model albeit with different parameters for each species. This study demonstrates that a simple PM model can accurately estimate the water requirements of these species in other growing regions. [ABSTRACT FROM AUTHOR]

[Objective] The aims of this study are to clarify the characteristics and influence of soil water content, soil porosity, soil nutrients and the flue-cured tobacco quality in the condition of different dosage of water retaining agent (Potassium polycalcium), to apply the important supply to relieve drought and enhance the quality of the tobacco. Methods] The random-groups design and the condition of different dosages of water retention agent were adopted to measure the indices of soil water content. soil nutrients and tobacco. quality. [Results] As the dosages of water retention agent increased the soil pH value changed from 7.4 το 7.7. total porosity, capillary porosity, soil saturated water content field capacity, capillary water content first increased then decreased. when the dosage of water retaining agent reached to 150 kg/hm, the value of soil bulk density reached to the lowest value. However, the values of total porosity, capillary porosity, soil saturated water content and capillary porosity reached to the highest values. The value of CEC showed fluctuated changes. With the increased of the dosages of water retention agent, the soil organic carbon, soil total potassium available potassium first increased then decreased. However, the total nitrogen, total phosphorus, alkali hydrolyzed nitrogen and available phosphorus showed the increasing trends. But the bulk density first decreased then increased. The chlorine and total nitrogen of the tobacco leaves showed the trends of the upper leaves < the middle leaves < the lower leaves, and as the concentrations of the water retention agent increased, the content of the chlorine of the tobacco leaves showed the fluctuating change. The potassium of middle and upper leaves of the tobacco leaves were higher than that of the lower leaves. And it increased as the concentrations of the water retention agent increased. The content of nicotine changed as the order: the upper leaves the middle leaves the lower leaves, and there existed the weak correlation between nicotine and the concentration of the water retention agents. The reducing sugar and total sugar showed the similar change trends. The ratio of potassium and chlorine changed as the order: the upper leaves > the middle leaves > the lower leaves, and showed the fluctuating change trends as the concentration of water retention agent increased. However, the ratio of nicotine and total nitrogen and the ratio of sugar and alkaline. showed the order: the upper leaves < the middle leaves < the lower leaves, and the two ratios increased as the concentration of water retention agents increased. Meanwhile, there existed the significant positive correlation between the soil total nitrogen and the chlorine contents, the potassium of the upper leaves, the reducing sugar (p<0.05). Also there existed the significant positive correlation between the soil organic carbon and the chlorine contents, the reducing sugar the potassium of the upper leaves, the nicotine of the lower leaves (p<0.05). [Conclusion Above all, the dosage of 150 kg/hm' is considered as the best dosage to soil amelioration in southwest China. Also this study can supply the basis and data supports to the anti- drought ability and enhance the flue-cured tobacco quality. [ABSTRACT FROM AUTHOR]

Evapotranspiration is a key hydrological process in Brazil's 1,000,000-km2 tropical semiarid Caatinga biome, where monitoring is crucial, but data are scarce. We propose a method to estimate daily actual evapotranspiration (LE) based on the canopy-radiation balance, measuring air and canopy temperatures, relative humidity, wind speed, and global radiation. The method was applied at a location with preserved Caatinga forest [Aiuaba Experimental Basin, daily average net radiation (Rn) of 12 MJ/m2 ] during one hydrological year (2020–2021). The results, which agree with independently performed field measurements, identify the predominance of distinct evaporative processes throughout the year. In the dry season, net radiation is high (16.7 MJ/m2/day), but actual evapotranspiration is negligible (LE/Rn<0.01) because stress due to extremely low soil water content causes leave deciduousness and root shrinkage. Contrastingly, in the rainy season, soil water content increases, leaves recover, and roots expand, enhancing actual evapotranspiration (LE=6 mm/day and LE/Rn=0.89). Thus, in the Caatinga forest, during the dry and transition periods, actual evapotranspiration is ultimately ruled by the soil water content (source-limited), whereas during the rainy season, it is sink-limited (i.e., controlled by atmospheric demand). Practical Applications: The authors developed a new method to assess actual evapotranspiration in forested areas. The actual evapotranspiration, which is fundamental to compute irrigation demand, is also essential to understand the impact of climate change on forests. This is particularly important for drylands, such as the 1,000,000-km2 Brazilian semiarid region, where water is scarce and actual evapotranspiration is high, consuming 70% of the precipitation. The method, which estimates the energy balance on the leaves of forest trees, demands the measurement of only a few variables, such as temperature, air relative humidity, wind speed, and radiation. The equipment to perform the measurement is much cheaper (less than 10%) than that of the reference methods for this kind of study. Therefore, with the same budget, the method can be applied at more locations, increasing the spatial representation of the measurements. The method hereafter presented is especially meant to help semiarid and arid regions, where evapotranspiration is high and monitoring is crucial, but data are often scarce. [ABSTRACT FROM AUTHOR]

The interchange of water vapor between the land and the atmosphere is influenced by actual evapotranspiration (AET). A nonlinear model (AET-SWC-PET-GPP, ASPG) was developed in this study to combine potential evapotranspiration (PET), soil water content (SWC), and gross primary productivity (GPP) in order to quantitatively estimate AET. The Fluxnet Network 2015 global flux station dataset was used to compare the AET models (AET-SWC, AS; AET-SWC-PET, ASP and AET-SWC-PET2, ASP2) with various combinations of influencing factors. The results show that the simulation accuracy of the ASPG model is higher than that of AS, ASP, and ASP2, with improvements in a coefficient of determination (R2) of 45.3, 8.1, and 5.7%, respectively.The ASPG performed well for various vegetation types, geographical regions, and time scales. It was also discovered that the fitting coefficients vary depending on the type of vegetation, each with its own range of values. The ASPG model put forth in this study can be used to more effectively estimate AET quantitatively on a global scale and can serve as a theoretical foundation for the accurate calculation of global evapotranspiration and the wise use of water resources. HIGHLIGHTS Introduction of a new model (ASPG) that integrates potential evapotranspiration (PET), soil water content (SWC), and gross primary productivity (GPP) to quantitatively estimate actual evapotranspiration (AET).; Additionally, the study emphasizes the variability of fitting coefficients based on vegetation type, suggesting the model's adaptability to different ecosystems.;

[Objective] To investigate the spatial distribution and cooperative utilization characteristics of soil water under the orchard-farmland mosaic pattern in the southern Loess Tableland. [Methods] The 10-year-old, 21-year-old, and 25-year-old apple orchards (AO10, AO21, and AO25) and their adjacent farmland were selected in Changwu tableland were selected to quantitatively calculate the contribution of soil water storage to water consumption of orchard. By measuring the soil water content at relevant sites in the orchard-farmland interface zone after the rainy season in 2021. [Results] The precipitation in 2021 is 756 mm, which was a typical wet year. The rainfall infiltration depth of farmland and AO21, AO25 orchards reached 8.4, 7.0, and 5.0 m at the end of November, respectively. AO10 orchard-farmland boundary zone is 4 m deep, the soil water content in the lower part is larger than that in the upper part, and the average soil water content was 25.5% in the 4—10 m soil layer. In AO21 orchard, the average soil water content of the 0—7 m soil layer was 22.1%, and that of the 7—10 m soil layer was 15.0%. the average soil water content of the 0—5 m soil layer of AO25 orchard was 20.9%, and that of 5—10 m was 13.6%. The soil dry layer of AO21 and AO25 orchard was below 7.0 and 5.0 m, respectively. In the horizontal direction, the distance of soil water used by AO21 and AO25 orchards from adjacent farmland reached 5 and 8 m, respectively, and the water supply from fields to orchards at the agro-fruit interface was 0.08 and 0.25 m3/m2 when the soil profile was divided by the upper boundary of the dry layer. Below is the actual water supply, which is 0.45 and 0.81 m3/m2, respectively. [Conclusion] The mosaic layout of apple orchards and farmland in the Loess tableland region is a reasonable utilization structure, and factors such as the age of apple trees and the width of adjacent farmland should be considered in land planning and management. The research results will contribute to promote the sustainable utilization and spatial optimization of regional soil water resources.

[Objective] Precipitation is the main source of soil water in arid and semi-arid regions. By combining field observation and model simulation to study the regularity of rainfall infiltration, the soil water deficit can be mastered more systematically. [Methods] Through fixed point observation, the Hydrus-1d model was applied to simulate the dynamic change of soil water in Platycladus orientalis on the artificial of Nanshan Mountain in Lanzhou, evaluate the applicability of the model in arid region, and analyze the soil water response and infiltration mechanism under different rainfall conditions. [Results] The Hydrus-1d model had good applicability in the artificial side of Nanshan in Lanzhou, and the deep simulation effect was better. When the rainfall was less than 30 mm, the soil moisture content at 10 cm has the strongest response to rainfall, while the influence of rainfall at 30 and 50 cm was relatively small and had an obvious lag, and there was no response below 70 cm. There was a wetness peak when the rainfall was more than 8.2 mm. During the simulation period, the maximum infiltration depth was 70 cm and the maximum infiltration volume was 23.7 mm. The infiltration depth increased with time, while the infiltration volume and infiltration rate decreased with time. Rainfall was positively correlated with infiltration volume, infiltration depth and infiltration rate (p

The restoration of native vegetation like pines helps mitigate soil erosion, but the effects of pine needle litter on runoff, erosion, and hydrology in karst hillslopes are unclear. This study investigated these factors during the rainy season from June to August 2021 under six treatments (flat, gentle, and steep slopes with and without pine needle coverings). The results showed that pine needle litter significantly increased the soil water content, particularly on steeper slopes, by improving the water-holding capacity. It also substantially reduced runoff (by 23.8%) and soil erosion (by 92.5%). The critical rainfall threshold for generating runoff did not occur in the pine needle covering treatment, whereas it was 19.3 ± 8.8 mm in the bare soil treatment under wet conditions. These findings highlight the efficacy of pine needle cover in reducing runoff and erosion in karst areas, promoting it as a sustainable method for restoring degraded soil. [ABSTRACT FROM AUTHOR]

Aims: Soil microbial and enzymatic activity have important roles in soil health, nutrient cycle and plant growth. Biochar is an excellent biomass for increasing soil water content, but some biochar compounds, due to their high pH, are harmful to the soil. This study aimed to investigate the effect of biochar and sulfur-modified biochar on improving the soil water content and biochemical properties in a millet cropping system. Methods: The field experiment was performed in a completely random design with three replications. Experimental treatments included control, 15 t ha− 1 sunflower biochar (B), and 15 t ha− 1 sulfur-modified biochar (BS). Results: Biochar (B and BS) improved the soil water content by 47% and 35%, respectively, compared to the control. B and BS treatments improved soil biological properties, including microbial biomass carbon, basal respiration, and the activity of catalase, dehydrogenase, urease, and alkaline phosphatase enzymes compared to the control. The application of B and BS treatments decreased soil EC and sodium adsorption ratios compared to the control. The highest (8.26) and lowest (7.83) values of soil pH were related to the B and BS treatments, respectively. Treatment of soil with B and BS enhanced soil dissolved organic carbon (90% and 33%), available nitrogen (74% and 48%), and available phosphorus (60% and 96%) compared to the control. The application of B and BS treatments enhanced plant nutrients (nitrogen, phosphorus, and potassium) and the leaf relative water content by 40% and 14%, respectively. Biochar (B and BS) improved millet yield by 58% and 115%, respectively, compared to the control. Conclusion: Sulfur increased the efficiency of biochar in amending saline and calcareous soil and enhanced millet yield by improving the chemical properties (pH and CEC) of biochar. [ABSTRACT FROM AUTHOR]

SNOSWAB (Snow, Soil Water and Water Balance) is a unique online deterministic model built using tipping-bucket approaches that allows for the daily estimation of (i) snowpack processes; (ii) soil water content; and (iii) soil water budget. SNOSWAB is most suitable for modeling field-scale processes for vertically and horizontally homogeneous soils, and its applicability is not limited to specific climate zones or geographical areas. The model is freely available, and its streamlined online interface integrates powerful calibration, visualization and data export routines. In this study, SNOSWAB development and a conceptual model, as well as an example of its application using data collected during a 12-year (2008–2019) field study conducted at the Agriculture and Agri-Food Canada Harrington Experimental Farm (HEF) on Prince Edward Island (PEI), Canada, are presented. Input data consisting of daily air temperature, total precipitation, rainfall and evapotranspiration were used in conjunction with soil properties and daily soil water content, snowpack thickness, surface runoff and groundwater recharge to calibrate (2010–2014) and validate (2015–2019) the model. For both the calibration and validation simulations, the statistical indicators used for evaluating model performance indicated, in most cases, high model fitness (i.e., R2 > 0.5, NRMSE < 50% and −25% < PBIAS < 25%) for the various time intervals and parameters analyzed. SNOSWAB fills an existing gap in the online environment and, due to its ease of use, robustness and flexibility, shows promise to be adopted as an alternative for more complex, standalone models that might require extensive resources and expertise. [ABSTRACT FROM AUTHOR]

Understanding the dynamic relationships between soil organic carbon (SOC) and stand age are essential to quantify and predict the terrestrial carbon sequestration potential. However, the spatial patterns in the response of rubber plantation SOC to stand age and their driving factors remain unclear. Based on SOC and its components measurement at different soil depths (0–40 cm) in rubber plantations under five different age classes (0–5, 5–10, 10–20, 20–30, and >30 years) in three major rubber cultivation regions in China, distribution pattern and controlling factors of SOC were investigated. We found that SOC and its components showed significant spatial variability vertically with soil depth and laterally across sampling sites. SOC contents in three major rubber cultivation regions range from 4.48 to 20.13 g kg−1 at a depth of 0–40 cm. Among the sampling sites, Jinghong had the highest SOC content at a depth of 0–10 cm (20.13 g kg−1). On a large‐scale, the relationship between SOC and stand age in rubber plantations did not show a consistent pattern among different sampling sites. Additionally, annual rainfall, soil moisture content, and soil pH had a stronger impact on SOC in rubber plantations compared to stand age. The results indicated that the spatial variability of SOC in rubber plantations with stand age could be influenced by specific soil properties and climate‐related variables at each sampling site. This study emphasized the significance of conducting multi‐site, multi‐scale studies to enhance our understanding of SOC dynamics and its influencing factors, and help to more accurately predict the dynamic changes of soil carbon storage in rubber plantations. [ABSTRACT FROM AUTHOR]

Featured Application: Landowners, regional and national governments, and researchers can use predictions of the soil hydrological properties created in this work, such as wilting point, field capacity, macroporosity, and total available water content, to characterize soils for soil management decisions in New Zealand, e.g., in terms of irrigation requirements, or for policy, e.g., nutrient budgets and regulations. This paper describes a new pedotransfer function (PTF) for the soil water content of New Zealand soils at seven specific tensions (0, −5, −10, −20, −40, −100, −1500 kPa) using explanatory variables derived from the S-map soil mapping system. The model produces unbiased and physically plausible estimates of the response at each tension, as well as unbiased and physically plausible estimates of the response differences that define derived properties (e.g., macroporosity and total available water content). The PTF is a development of an earlier model using approximately double the number of sites compared with the earlier study, a change in fitting methodology to a semi-parametric GAM Beta response, and the inclusion of sample depth. The results show that the new model has resulted in significant improvements for the soil water content estimates and derived quantities using standard goodness-of-fit measures, based on validation data. A comparison with an international PTF using explanatory variables compatible with variables available from S-map (EUPTF2) suggests that the model is better for prediction of soil water content using the limited information available from the S-map system. [ABSTRACT FROM AUTHOR]

Soil water content (θ), matric potential (h) and hydraulic conductivity (K) are key parameters for hydrological and environmental processes. Several sensors have been developed for measuring soil θ–h–K relationships. The cost of such commercially available sensors may vary over several orders of magnitude. In recent years, some sensors have been designed in the framework of Internet of Things (i.e., IoT) systems to make remote real-time soil data acquisition more straightforward, enabling low-cost field-scale monitoring at high spatio-temporal scales. In this paper, we introduce a new multi-parameter sensor designed for the simultaneous estimation of θ and h at different soil depths and, due to the sensor's specific layout, the soil hydraulic conductivity function via the instantaneous profile method (IPM). Our findings indicate that a second-order polynomial function is the most suitable model (R2 = 0.99) for capturing the behavior of the capacitive-based sensor in estimating θ in the examined soil, which has a silty-loam texture. The effectiveness of low-cost capacitive sensors, coupled with the IPM method, was confirmed as a viable alternative to time domain reflectometry (TDR) probes. Notably, the layout of the sensor makes the IPM method less labor-intensive to implement. The proposed monitoring system consistently demonstrated robust performance throughout extended periods of data acquisition and is highly suitable for ongoing monitoring of soil water status. [ABSTRACT FROM AUTHOR]

Soil moisture is among the most essential variables in hydrology and earth science. Many satellite missions, such as AMSR-E/2, have been launched to observe it in broader spatial coverage to overcome the shortage of in situ observations. However, the satellite soil moisture products have been reported to comprise errors caused by the so-called "temperature effects" widely observed in dielectrically measured in situ volumetric soil water content (SWC). In this work, we confirmed the existence of these errors in AMSR2 soil moisture products. A new algorithm was developed to remove these errors using satellite data at ascending and descending overpasses. The application of this algorithm to both satellite and in situ data of SWC and soil temperature at the Mongolia site shows that the difference between SWC values at ascending and descending overpasses caused by temperature effects is effectively removed. We assess the impact of this removal method on satellite data by comparing it with in situ data, utilizing metrics such as the correlation coefficient and other widely adopted evaluation methods. It is shown that the difference between the original and corrected in situ SWC is much smaller than that between AMSR2 and in situ SWC, either corrected or not. The results indicate that the metric values between the corrected AMSR2 and in situ SWC, after removing apparent differences caused by temperature effects, slightly improved compared to those between the original AMSR2 and in situ SWC. Though these findings imply that the removed errors may not be the most dominant, considering the current significant difference between AMSR2 and in situ SWC, the removal makes the ascending and descending data have close characteristics. It may allow using data at both ascending and descending overpasses and double the temporal resolution of AMSR2 SWC data. [ABSTRACT FROM AUTHOR]

Reducing the nitrogen (N) application rate and improving water-use efficiency (WUE) are extremely important for sustainable agricultural development in wheat–maize rotation systems in the North China Plain (NCP). We conducted a three-year experiment to investigate the effects of the N application rate on the water-use characteristics of wheat–maize rotation systems in the NCP. The experiment consisted of four N application rates: 250, 167, 84, and 0 kg hm−2, denoted by N3, N2, N1, and N0, respectively. The results showed the following: For the 0–60 cm soil layer, N deficiency could lead to reduced soil water use (SWU) in wheat seasons, but in maize seasons, N deficiency showed no significant effects on SWU in the 0–60 cm layer. For the 60–140 cm soil layer, N deficiency could lead to reduced SWU in wheat seasons, but in maize seasons, the effects of N deficiency on SWU in the 60–140 cm layer varied with the SWC in the 0–60 cm layer. Throughout the three-year experiment, the evapotranspiration (ET), leaf area index (LAI), yield, and WUE of plants receiving low N treatments decreased with the growing season due to the negative effects of low N treatment (N1 and N0) on the soil. The LAI, total ET, grain yield, and WUE were all positively correlated with each other for both wheat and maize. Considering grain yield and WUE, a single-season N application rate of 167 kg hm−2 (N2 treatment) in the NCP could meet the growth needs of the wheat–maize rotation system. [ABSTRACT FROM AUTHOR]

Although advanced production systems have been developed in the last 20 years, water scarcity is still a growing problem in agriculture. This study aims to evaluate the effect of different strategies that combine the application of seaweed and microbial biostimulants with regulated deficit irrigation (RDI) strategies on the irrigation water productivity (WPI), fruit quality parameters and soil enzymatic activity in pepper plants (Capsicum annum sp.) under two commercial greenhouse conditions. In each trial, two treatments were applied: (i) irrigation according to Farmer criteria without biostimulant applications and (ii) a combined treatment of RDI and the same biostimulation program, composed of Bacillus paralicheniformis and Ascophillum nodosum extracts. RDI was applied in different phenological stages in each greenhouse after the establishment until the 1st harvest in trial 1 or during the ripening and harvest period in trial 2. On average, the irrigation was reduced by 600 m3 ha−1 compared to the Farmer irrigation schedule. In both trials, biostimulation promoted an increase in fruit numbers, punctually in trial 1, leading to yield precocity, or generally in trial 2, obtaining a higher yield. Globally, WPI was increased when RDI was combined with biostimulation. This combined treatment also enhanced the root water absorption and improved the soil enzymatic activity in both greenhouses, suggesting that nutrients in the soil would become more available to plants. Thus, the combined action of biostimulation under different RDI strategies has been proved to be a useful strategy to improve agricultural sustainability. [ABSTRACT FROM AUTHOR]

Aims: Coffee silverskin (CS) is the most abundant waste from coffee roasting. In this research, the potential of CS as soil fertilizer for barley (Hordeum vulgare L.) cultivation was evaluated. Methods: Barley plants were grown, for 10 days from the start of germination, in soils mixed with different CS percentages (0, 2, 6 or 10%). The effects of CS addition on soil capacity to retain water and on the mold/yeast community were evaluated. Physio-morphological and biochemical responses of leaves and roots of barley plants growing in CS-enriched soil were evaluated. Results: Root and shoot length decreased in plants grown with CS, but biomass was less affected and even increased at 2% CS. Photosynthesis was higher in barley seedlings grown on CS-enriched soil than in control plants. However, Chl b was reduced in leaves of plants grown with CS. The total leaf protein content did not change with moderate CS additions in soil. However, when grown in soil with 10% CS, a significant reduction of total protein and Rubisco was observed. Extracts of barley shoots from plants grown in soil with 10% CS showed a greater antioxidant capacity with respect to all other experimental conditions. Conclusions: We conclude that CS addition to soil may improve soil property to retain water and, at low concentrations (2% w/w) positively affects barley physiology and growth. [ABSTRACT FROM AUTHOR]

Mediterranean water-stressed areas face significant challenges from higher temperatures and increasingly severe droughts. We assess the effect of climate change on rainfed barley production in the aridity-prone province of Almería, Spain, using the FAO AquaCrop model. We focus on rainfed barley growth by the mid-century (2041–2070) and end-century (2071–2100) time periods, using three Shared Socio-economic Pathway (SSP)-based scenarios: SSP1-2.6, SSP2-4.5, and SSP5-8.5. Using the paired t-test, Spearman and Pearson correlation coefficient, Root Mean Squared Error, and relative Root Mean Squared Error, we verified AquaCrop's ability to capture local multi-year trends (9 or more years) using standard barley crop parameters, without local recalibration. Starting with a reference Initial Soil Water Content (ISWC), different soil water contents within barley rooting depth were modelled to account for decreases in soil water availability. We then evaluated the efficiency of different climate adaptation strategies: irrigation, mulching, and changing sowing dates. We show average yield changes of +14% to −44.8% (mid-century) and +12% to −55.1% (end-century), with ISWC being the main factor determining yields. Irrigation increases yields by 21.1%, utilizing just 3% of Almería's superficial water resources. Mulches improve irrigated yield performances by 6.9% while reducing irrigation needs by 40%. Changing sowing dates does not consistently improve yields. We demonstrate that regardless of the scenario used, climate adaptation of field barley production in Almería should prioritize limiting soil water loss by combining irrigation with mulching. This would enable farmers in Almería's northern communities to maintain their livelihoods, reducing the province's reliance on horticulture while continuing to contribute to food security goals. [ABSTRACT FROM AUTHOR]

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Copyright of Journal of Irrigation & Drainage is the property of Journal of Irrigation & Drainage Editorial Office and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Accurate estimation of soil water content (SWC) is crucial for effective irrigation management and maximizing crop yields. Although dielectric property-based SWC measurements are widely used, their accuracy is still affected by soil variability, soil–sensor contact, and other factors, making the development of convenient and accurate soil-specific calibration methods a major challenge. This study aims to propose a plate compression filling technique for soil-specific calibrations and to monitor the extent of soil biomass degradation using dielectric properties. Before and after biodegradation, dielectric measurements of quartz sand and silt loam were made at seven different water contents with three different filling techniques. A third-order polynomial fitting equation explaining the dependence of the dielectric constant on the volumetric water content was obtained using the least-squares method. The suggested plate compression filling method has a maximum mean bias error (MBE) of less than 0.5%, according to experimental results. Depending on the water content, silt loam's dielectric characteristics change significantly before and after biodegradation. The best water content, measured in gravimetric units, to encourage the decomposition of biomass was discovered to be 24%. It has been demonstrated that the plate compression filling method serves as a simple, convenient, and accurate alternative to the uniform compaction method, while the dielectric method is a reliable indicator for evaluating biomass degradation. This exploration provides valuable insights into the complex relationship between SWC, biomass degradation, and soil dielectric properties. [ABSTRACT FROM AUTHOR]

Gamma-ray spectroscopy (GRS) enables continuous estimation of soil water content (SWC) at the subfield scale with a noninvasive sensor. Hydrological applications, including hyper-resolution land surface models and precision agricultural decision making, could benefit greatly from such SWC information, but a gap exists between established theory and accurate estimation of SWC from GRS in the field. In response, we conducted a robust three-year field validation study at a well-instrumented agricultural site in Nebraska, United States. The study involved 27 gravimetric water content sampling campaigns in maize and soybean and 40K specific activity (Bq kg−1) measurements from a stationary GRS sensor. Our analysis showed that the current method for biomass water content correction is appropriate for our maize and soybean field but that the ratio of soil mass attenuation to water mass attenuation used in the theoretical equation must be adjusted to satisfactorily describe the field data. We propose a calibration equation with two free parameters: the theoretical 40K intensity in dry soil and a, which creates an "effective" mass attenuation ratio. Based on statistical analyses of our data set, we recommend calibrating the GRS sensor for SWC estimation using 10 profiles within the footprint and 5 calibration sampling campaigns to achieve a cross-validation root mean square error below 0.035 g g−1. [ABSTRACT FROM AUTHOR]

The subject of this study was to understand how grazing and precipitation affect the carbon cycle of grassland ecosystem. The experiment was carried out in a desert steppe of Siziwang Banner, Inner Mongolia, China, and measured CO2 flux and abiotic factors twice a month during the growing season (July to October in 2016, May to October in 2017). The experiment used a completely randomized block design, involving four different stocking rate treatments [CK, no grazing, (0 sheep unit hm –2 half year–1), light stocking rate (LG, 0.93 sheep unit hm–2 half year–1), moderate stocking rate (MG, 1.82 sheep unit hm–2 half year–1) and heavy stocking rate (HG, 2.71 sheep unit hm–2 half year–1)] with three replicates, and four precipitation treatments [50% reduced precipitation (P1), natural precipitation (P2), 50% increased precipitation (P3) and 100% increased precipitation (P4)] were set up in each stocking rate treatment plot. Results indicated that increased precipitation treatments significantly increased soil water content (SWC) and soil respiration (Rs), and significantly reduced soil temperature (Ts), grazing treatments significantly reduced Ts, the interaction between precipitation and stocking rate had no significant impact on the above indicators; Rs increased with increasing precipitation in the order: P4 > P3 > P2 > P1, Rs exhibited the following order under different stocking rates: CK > LG > MG > HG. There was a strong positive correlation between Rs and SWC, and a negative relationship between Rs and Ts. Our results demonstrate that SWC is the dominant factor affecting Rs, as SWC explained 87.12% of the variation in Rs. [ABSTRACT FROM AUTHOR]

Many studies have investigated how soil water availability in shallow soil affects forest transpiration, but how deep soil water status (below 1 m depth) alters tree water use remains poorly understood. To improve our understanding of how deep soil water changes tree transpiration dynamics, we measured soil water content (SWC) in more than 20 m depths, the radial sap flow profile and the leaf area index (LAI) in the 2017 growing season in 9-, 12-, 16-, 19- and 23-year-old afforested apple (Rosaceae) trees on the Chinese Loess Plateau. SWC was also measured in long-term cultivated farmland to derive SWC before afforestation. The results showed that there was no statistical difference in SWC in shallow soil among orchards (p > 0.05), while SWC in deep soil reduced rapidly with increasing tree age. The average SWC at 1–20 m decreased from 0.27 ± 0.02 cm3 cm−3 in farmland to 0.21 ± 0.03 cm3 cm−3 in the 23-year-old orchard. Moreover, water storage in deep soil decreased by 139 mm yr−1 between the 9- and 12-year-old stands, 105 mm yr−1 between the 12- and 16-year-old stands, 44 mm yr−1 between the 16- and 19-year-old stands, and 9 mm yr−1 from the 19- to 23-year-old stands, indicating that gradually decreased SWC in deep soil has restricted tree water use. Due to the changes in SWC, growing-season transpiration and the LAI peaked in the 16-year-old orchard and then decreased with increasing stand age. Growing-season transpiration in the 23-year-old orchard was only 77% of that in the 16-year stands, despite the older trees having larger diameters at the breast height. Our results suggest that soil water availability in deep soil plays an important role in regulating trees' transpiration. [ABSTRACT FROM AUTHOR]

Understanding the distribution of water and nitrate nitrogen in the soil profile is crucial for the reasonable operation of fertigation, and it is also fundamental for controlling and regulating nitrate nitrogen in the root zone, thereby meeting a crop's requirements. The application rates of fertilizer and water directly influence this distribution of water and nitrate nitrogen. However, the effects in Aeolian sandy soil, a type of developing soil bordering deserts, remain ambiguous. In this study, field experiments for different drip fertigation treatments in Aeolian sandy soil were conducted to investigate the soil water distribution, as well as that of nitrate nitrogen. A completely randomized experimental design was implemented, encompassing three levels of irrigation amount: low (W1), medium (W2), and high (W3), and three levels of nitrogen application rate: low (F1), medium (F2), high (F3). After the completion of each irrigation treatment, soil samples were extracted at 10–20 cm intervals. The soil water and nitrate nitrogen contents in the profiles of these samples were measured. The experimental results revealed that increasing the nitrogen application rate facilitated the retention of greater amounts of water and nitrate nitrogen in the soil profile. However, with an increase in the nitrogen application rate, both soil water and nitrate nitrogen exhibited a radial tendency to move away from the drip emitter. Some moved upward and accumulated in surface soil near a ridge furrow, while some moved downward and remained in a deeper area approximately 30 cm horizontally from the emitter at depths of 40–60 cm. The uniformity of the water distribution decreased with increasing nitrogen application under low water conditions, with a reversal of this trend observed in medium and high water treatments. The effect of nitrogen application level on the uniformity of the nitrate nitrogen distribution was not significant. There was no significant correlation between the average soil water content and nitrate nitrogen content along the horizontal direction, however, a positive correlation existed in the vertical direction. In the whole profile, increasing the nitrogen application enhanced the correlation under low water conditions, but under medium and high water conditions, this trend was the opposite. This implies that, to avoid nitrate nitrogen leaching or limiting in a specific area, a moderate nitrogen application level is advisable. Under low water conditions, nitrogen application showed a positive effect on the nitrate nitrogen content, and a higher application is recommended. In cases of substantial water irrigation or rainy years, the nitrogen application rate should be decreased. [ABSTRACT FROM AUTHOR]

Introduction: The components of nighttime sap flux (En), which include transpiration (Qn) and stem water recharge (Rn), play important roles in water balance and drought adaptation in plant communities in water-limited regions. However, the quantitative and controlling factors of En components are unclear. Methods: This study used the heat balance method to measure sap flow density in Vitex negundo on the Loess Plateau for a normal precipitation year (2021) and a wetter year (2022). Results: The results showed that the mean values were 1.04 and 2.34 g h-1 cm-2 for Qn, 0.19 and 0.45 g h-1 cm-2 for Rn in 2021 and 2022, respectively, and both variables were greater in the wetter year. The mean contributions of Qn to En were 79.76% and 83.91% in 2021 and 2022, respectively, indicating that the En was mostly used for Qn. Although the vapor pressure deficit (VPD), air temperature (Ta) and soil water content (SWC) were significantly correlated with Qn and Rn on an hourly time scale, they explained a small fraction of the variance in Qn on a daily time scale. The main driving factor was SWC between 40-200 cm on a monthly time scale for the Qn and Rn variations. Rn was little affected by meteorological and SWC factors on a daily scale. During the diurnal course, Qn and Rn initially both declined after sundown because of decreasing VPD and Ta, and Qn was significantly greater than Rn, whereas the two variables increased when VPD was nearly zero and Ta decreased, and Rn was greater than Qn. Discussion: These results provided a new understanding of ecophysiological responses and adaptation of V. negundo plantations to increasing drought severity and duration under climate changes. [ABSTRACT FROM AUTHOR]

A clean environment is an essential component of sustainable development, which is based on a comprehensive understanding of the behavior of water, soil, and air. The soil water retention (SWR) curve is a crucial function that describes how soil retains water, playing a fundamental role in irrigation and drainage, soil conservation, as well as water and contaminant transport in the vadose zone. This study evaluates the accuracy, performance, and prediction capabilities of 15 SWR models. A total of 140 soil samples were collected from different sites, covering all textural classes. Standard suction tests, using both hanging column and ceramic pressure plate extractors, were conducted to compile the SWR databank. 15 SWR models were selected and fitted to the SWR data points. Soil texture, bulk density, and organic matter were used to determine their effect on the performance of the SWR models. The results indicate that the Tani and Russo models exhibit the lowest levels of accuracy and performance among the selected models. Based on the Akaike and Bayesian information criteria analysis, the van Genuchten model exhibits the lowest values among the selected models, with poor prediction capabilities in estimating the SWR curve. The significance test at the 0.05 level (95% confidence interval) shows that according to the calculated p-values for the Pearson correlation coefficient between RMSE and texture, the Brooks-Corey and van Genuchten models are poorly influenced by soil properties. The performance of the models is not significantly affected by the soil organic matter. Similarly, bulk density does not significantly affect model performance except for the Brooks–Corey, van Genuchten, Tani, and Russo models. Among the SWR models considered, the double exponential, Groenevelt and Grant, and Khlosi et al. models demonstrate superior accuracy and performance in predicting the SWR curve. This is supported by lower values for RMSE, Akaike, and Bayesian information criteria. [ABSTRACT FROM AUTHOR]

Cotton holds a significant position among cash crops in China, with Xinjiang serving as the primary cotton‐growing region within the country. Agricultural practices involving plastic mulching have gained importance. However, the presence of residual plastic film affects the growth of cotton seedlings as well as the soil environment. Our study aimed to explore the impact of residual plastic film accumulation on the growth of cotton seedlings and the associated soil water‐salt environment. This was done through a barrel planting experiment, utilizing soil from cotton fields with varying durations of mulching. The study showed that when the mulching period exceeded 12 years (residual plastic film content of 260.77 kg hm−2), residual plastic film had a significant impact on cotton seedling growth and the soil environment. Residual plastic film reduces the seedling germination rate of cotton by up to 11.11% (7 days after irrigation, 15 years of film mulching, residual plastic film content of 309.88 kg hm−2). It also impedes the growth of cotton seedlings; plant height, stem thickness, and leaf area were reduced by 34.52%, 10.73%, and 37.18%, respectively (19 days after irrigation, 15 years of film mulching, residual plastic film content of 309.88 kg·hm−2). Compared with the treatment without residual plastic film, the shallow soil water content in the T5 treatment decreased by 1.19% (10 days after irrigation, 15 years of film mulching, residual plastic film content of 309.88 kg·hm−2). Residual plastic film in cotton fields subjected to long‐term mulching obstructs the normal growth and development of cotton seedlings while also impacting the transport of soil water and salt. Therefore, we recommend adopting biodegradable mulch or regularly recycling residual plastic film within mulched areas to prevent its accumulation and subsequent negative impacts. [ABSTRACT FROM AUTHOR]

Water vapor adsorption on soil, a crucial non-rainfall water resource in arid regions, warrants further experimental investigation, particularly on two typical land surfaces: bare soil and gravel. This study examined the formation characteristics and influencing factors of vapor adsorption in an arid region of Northwestern China. Observations and analyses were conducted on adsorption and evaporation measurements taken by two small weighing lysimeters (SLSs); soil temperature at a depth of 5 cm; surface temperature; relative humidity; and air temperature at a height of 30 cm above the ground from 2019 to 2020. The adsorbed water in this area was more abundant at night and less abundant during the day, with a stable nightly adsorption rate of 0.013 mm/h. Adsorption was more frequent in spring and winter (from January to June and November to December), accounting for about 90% of the total annual adsorption. In 2019 and 2020, the ratio values of adsorption to evaporation were 0.16 and 0.10 for bare soil, and 0.10 and 0.12 for gravel, respectively. Adsorption was more likely to occur when the soil moisture content was less than 13%; the highest adsorption frequency was close to 20% when the RH was between 75 and 95%; low soil temperatures were more conducive to the occurrence of adsorption. The effect of temperature differences (Ta−Ts) on adsorption was stronger than that of relative humidity. The adsorption frequency generally showed a bimodal change with increasing temperature difference, but the effect of temperature differences was less effective for gravel than bare soil. When the relative humidity was high and the temperature difference was weakly positive, the maximum adsorption intensity could reach 0.18 mm/h. [ABSTRACT FROM AUTHOR]

With the intensification of global change, forests are subjected to varying degrees of drought or high-temperature stress, which has an indelible impact on the growth of trees. However, knowledge on the response of sap flow to environmental changes in different types of forests is still rare, especially in China's subtropical forest ecosystem. Consequently, studying how different tree species regulate their sap flow in response to shifting environmental conditions is essential for understanding forest transpiration, water use efficiency, and drought stress resilience. Therefore, this study aimed to investigate the sap flow dynamics of seven tree species in five forest plots, i.e., pine forest (PF), two types of mixed conifer-broadleaf forests (MF1+MF2), monsoon evergreen broadleaved forest (MEBF), and montane monsoonal evergreen broad-leaf forest (MOBF) at Dinghushan National Reserve in Southern China, using the heat dissipation probe technique and synchronous environmental factor recordings. Results demonstrated a significant influence of photosynthetic active radiation (PAR) on sap flow across all tree species, with mean PAR values ranging from over 1200 to 425 μmol m−2 s−1, establishing it as the principal driving factor. This observation underscores the heightened responsiveness or sensitivity of tree species to variations in PAR as the forest undergoes development and maturation. The correlation between vapor pressure deficit (VPD) and tree sap flow decreased as succession progressed. Moreover, the influence of soil water content (SWC) on sap flow stability against environmental changes increased. Similar patterns were also found between the two MF, with MF-2 displaying ecological characteristics and environmental conditions more closely aligned with those of the late-successional MEBF. The study reveals the intricate relationship between environmental factors and sap flow regulation in tree species within a subtropical forest ecosystem. Addressing a comparative gap in sap flow correlation among dominant tree species at Dinghushan, it establishes a hydro-physiological foundation for understanding tree species substitution during forest succession. The results provide key insights for forest management and climate-related research. Future studies should delve into the long-term implications of observed sap flow dynamics, exploring their impact on tree species adaptability amid ongoing environmental changes.

Background Soil water content is one of the critical indicators in agricultural systems. Visible/near-infrared hyperspectral remote sensing is an effective method for soil water estimation. However, noise removal from massive spectral datasets and effective feature extraction are challenges for achieving accurate soil water estimation using this technology. Methods This study proposes a method for hyperspectral remote sensing soil water content estimation based on a combination of continuous wavelet transform (CWT) and competitive adaptive reweighted sampling (CARS). Hyperspectral data were collected from soil samples with different water contents prepared in the laboratory. CWT, with two wavelet basis functions (mexh and gaus2), was used to pre-process the hyperspectral reflectance to eliminate noise interference. The correlation analysis was conducted between soil water content and wavelet coefficients at ten scales. The feature variables were extracted from these wavelet coefficients using the CARS method and used as input variables to build linear and non-linear models, specifically partial least squares (PLSR) and extreme learning machine (ELM), to estimate soil water content. Results The results showed that the correlation between wavelet coefficients and soil water content decreased as the decomposition scale increased. The corresponding bands of the extracted wavelet coefficients were mainly distributed in the near-infrared region. The non-linear model (ELM) was superior to the linear method (PLSR). ELM demonstrated satisfactory accuracy based on the feature wavelet coefficients of CWT with the mexh wavelet basis function at a decomposition scale of 1 (CWT(mexh_1)), with R2, RMSE, and RPD values of 0.946, 1.408%, and 3.759 in the validation dataset, respectively. Overall, the CWT(mexh_1)-CARS-ELM systematic modeling method was feasible and reliable for estimating the water content of sandy clay loam.