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A new experimental laboratory design is introduced to analyze and quantify transport and turnover processes in top‐ and subsoils. The proposed technique allows the monitoring of transformation processes in an undisturbed soil matrix while preserving entirely intact soil particle interfaces. The experimental setup with undisturbed soil samples, which are embedded into two coupled gas sealed chambers, allows on‐time measurement of soil respiration processes under realistic moisture, water flux, and temperature conditions. Core Ideas: We introduce improved column breakthrough experiments with the advantage of visual monitoring processes.The stated device combines laboratory precision and controllability with field conditions such as temperature regime.Due to its design, it is possible to combine soil horizons, which allows us to simulate soil profiles.In combination with labeled C, small‐scale mass balancing of the C cycle is possible.The controllability allows flow in unsaturated conditions with control over water content and flow velocity column breakthrough experiments with the advantage of visual monitoring processes. [ABSTRACT FROM AUTHOR]

Soil moisture is a critical land surface variable, affecting a wide variety of climatological, agricultural, and hydrological processes. Determining the current soil moisture status is possible via a variety of methods, including in situ monitoring, remote sensing, and numerical modeling. Although all of these approaches are rapidly evolving, there is no cohesive strategy or framework to integrate these diverse information sources to develop and disseminate coordinated national soil moisture products that will improve our ability to understand climate variability. The National Coordinated Soil Moisture Monitoring Network initiative has developed a national strategy for network coordination with NOAA's National Integrated Drought Information System. The strategy is currently in review within NOAA, and work is underway to implement the initial milestones of the strategy. This update reviews the goals and steps being taken to establish this national‐scale coordination for soil moisture monitoring in the United States. Core Ideas: Soil moisture is a critical yet underrepresented land surface variable.Soil moisture data collection is undergoing rapid growth and innovation.We present a strategy for a nationally coordinated monitoring network. [ABSTRACT FROM AUTHOR]

The Richardson–Richards equation (RRE) is a widely used partial differential equation (PDE) for modeling moisture dynamics in unsaturated soil. However, field soil moisture observations do not always satisfy RRE. In this paper, we introduce a new physically constrained machine learning (PCML) approach to derive governing soil water flow PDE directly from moisture observations. This paper is viewed as a feasibility study and reports results of our first attempt in developing the PCML approach. Here, we rely on noisy synthetic soil moisture data obtained from the linear RRE subject to real flux boundary conditions. The linear RRE was used as a reference PDE to check the PCML‐derived PDEs, where the PCML performance was shown to be highly dependent upon the sample size in time and space. Results presented here confirm the feasibility of deriving soil water flow governing PDEs directly from soil moisture observations using PCML. Core Ideas: A physically constrained machine learning approach is introduced in soil hydrology.It enables retrieving soil water flow equation(s) from moisture observations.It enables adding new data‐driven terms to the Richardson–Richards equation. [ABSTRACT FROM AUTHOR]

Soil moisture data from the Oklahoma Mesonet have been used in numerous fields within the Earth sciences, including agriculture, hydrology, and meteorology. Soil matric potentials measured by heat dissipation sensors at Oklahoma Mesonet stations have been converted to soil volumetric water content estimates using soil water retention curve parameters estimated by the Rosetta pedotransfer function. Recently, an improved version of Rosetta, Rosetta3, was released. Informed by this new pedotransfer function and soil sampling at additional locations, an improved version of the Oklahoma Mesonet soil physical property database, MesoSoil v2.0, has been created. This article presents this new soil database, compares soil water retention parameters estimated using Rosetta3 with those derived from the original Rosetta model, and describes the effects of changes in those parameters on estimated volumetric water content. Using the Rosetta3 model led to changes in the estimated water retention parameters, most notably decreases in the parameter α, which is related to the inverse of the air‐entry potential. These changes resulted in volumetric water content estimates that differed from those based on Rosetta1, with mean absolute differences averaging 0.02 cm3 cm–3 across all site‐years and the greatest differences occurring during wet periods. The mean volumetric water content estimated using the Rosetta3 parameters across more than 100 sites was not significantly different from that determined by soil sampling. The updated database is publicly available and may be found here: http://soilphysics.okstate.edu/data. Core Ideas: Rosetta3 pedotransfer function was used to develop an updated Oklahoma Mesonet soil property database.Along with recent recalibration, the new database improves soil moisture estimates.The greatest changes in volumetric water content estimates were observed during wet conditions. [ABSTRACT FROM AUTHOR]

Local tree species distributions in tropical forests correlate strongly with soil water availability. However, it is unclear how species distributions are shaped by demographic responses to soil water availability. Specifically, it remains unknown how growth affects species distributions along water availability gradients relative to mortality.We quantified spatial variation in dry season soil water potential (SWP) in the moist tropical forest on Barro Colorado Island, Panama, and used a hierarchical Bayesian approach to evaluate relationships between demographic responses of naturally regenerating seedlings to SWP (RGRs and first‐year mortality) and species distributions along the SWP gradient for 62 species. We also tested whether species that were more abundant at the wet or dry end of the gradient performed better (a) at their "home end" of the gradient ("best at home" hypothesis) and (b) "at home" compared to co‐occurring species ("home advantage" hypothesis).Four and five species responded significantly to SWP in terms of growth or mortality respectively. Growth (but not mortality) responses were positively related to species distributions along the SWP gradient; species with a more positive (negative) growth response to SWP were more abundant at higher (lower) SWP, that is, at wetter (drier) sites. In addition, wet distributed species grew faster on the wet end of the SWP gradient than on the dry end ("best at home") and grew faster on the wet end than dry distributed species ("home advantage"). Mortality rates declined with seedling size for all species. Thus, seedling growth responses to SWP indirectly shaped local species distributions by influencing seedling size and thereby mortality risk.Synthesis. By demonstrating how growth responses to spatial variation in soil water availability affect species distributions, we identified a demographic process underlying niche differentiation on hydrological gradients in tropical forests. Recognizing the role of these growth responses in shaping species distributions should improve the understanding of tropical forest composition and diversity along rainfall gradients and with climate change. This study shows that growth responses to soil moisture play an important role in shaping the distribution of tree seedlings along a local soil moisture gradient. Species that grew well on the wet end of the gradient were more abundant there because they became taller more quickly, reducing their mortality risk, and because they grew faster than dry distributed species. [ABSTRACT FROM AUTHOR]

Highlights • Water use of coniferous and broad-leaved tree species was studied in Northern China. • The trees showed opposite water use patterns under different precipitation. • The different water use strategy of the mixed forest may be due to root distribution. • The P. orientalis was more sensitive to precipitation than Q. variabilis. Abstract Extreme drought and precipitation are expected to occur more frequently due to climate change, which may influence the water uptake patterns by vegetation in the rocky mountainous area of northern China. In this work, dual stable isotopes were used to detect the water sources of mixed forest of coniferous and broad-leaved tree species and their response of leaf water potential under differently sized precipitation events (no rain: 0.0 mm; light rain: 9.8 mm; moderate rain: 21.8 mm; large rain: 31.6 mm and rainstorm: 51.2 mm). The results showed that Platycladus orientalis and Quercus variabilis had different water use strategies and opposite responses to precipitation. On dry (no rain) days, P. orientalis and Q. variabilis predominantly obtained water from natural springs (43.3% and 36.2%, respectively) and deep soil layer (32.8% and 31.3%, respectively), while Q. variabilis also used water from shallow soil layer (23.4%). Following the rainfall events, the P. orientalis with dense and shallow fine root system absorbed more water from the soil surface layers (23.1–33.5%) and precipitation (15.2–30.7%). The pre-dawn water potential (ψ pd) and the midday water potential (ψ md) of P. orientalis increased with the amount of rainfall, revealing a sensitive response to precipitation. On the other hand, Q. variabilis mostly took up water from natural springs (32.3–36.7%) and deep soil layer (33.8–37.1 %) after the rainfall events through its well-developed taproot system. The ψ pd and ψ md of Q. variabilis had no significant variation between no rain and light rain events, though they increased significantly for large rainfall and rainstorm events with > 60 cm of soil water recharge provided by the precipitation. The study provides more insights into reforestation and water management in the region of northern China. [ABSTRACT FROM AUTHOR]

Highlights • We focused on tree-ring width (RWI) and potential evapotranspiration index (SPEI). • The relationship between RWI and SPEI was stronger under drier conditions. • SPEI of November and June were the most important predictors explaining RWI. • Beech tree growth was controlled by soil water supply and atmospheric evaporative demand. Abstract Due to the recent spread of forest die-off worldwide, concerns arise about the relative influence of specific climate parameters on tree growth decline in semi-arid environments, such as the Mediterranean mountain forests. As temperatures increase, drought may reduce tree productivity and survival across these forest ecosystems. Drought-induced tree growth decline can be interpreted as an early-warning signal of forest vulnerability. Here, we modeled the relationship between tree-ring width index (RWI) of beech populations in mountain forests of south-central Italy and the standardized precipitation evapotranspiration index (SPEI) derived from local weather stations. The aim of the research was to propose a procedure to determine the tipping point of drought severity triggering tree decline in beech forests. We focused on the cumulative water balance over the previous 1 month, which was particularly appropriate in relationship with the soil water conditions of these Mediterranean mountains. Under drier conditions, the correlation between RWI and SPEI was stronger, soil water supply (early fall of current year) and atmospheric evaporative demand (late spring of current year) being the dominant factors limiting tree growth of southern beech populations. [ABSTRACT FROM AUTHOR]

A four-year study was conducted to establish the effects of drip and microsprinkler irrigation systems on populations of Pratylenchus penetrans , early plant growth, and fruit yield of sweet cherry trees planted into soil previously used for apple production. The effects of irrigation type on root colonization by arbuscular mycorrhizal fungi, the abundance of soil microbial antagonists, soil biological suppressiveness, plant nutrition, and soil water content were also evaluated. Trees that received drip irrigation had larger trunk diameters than trees irrigated with microsprinklers throughout the first four years of orchard establishment, with greater total fruit yield also observed with drip irrigation in the fourth growing season. Populations of P. penetrans in soil and roots were smaller under drip irrigation than microsprinkler. Trees irrigated using drip emitters had higher per cent root colonization by arbuscular mycorrhizal fungi than those irrigated by microsprinklers, and had a greater density of fine roots in soil. Drip irrigation also increased soil volumetric water content in the root zone, with soil moisture content often approaching or exceeding field water-holding capacity relative to that of microsprinklers. Overall, drip irrigation shows potential as a component of an integrated pest management strategy for reducing the effect of P. penetrans on newly planted sweet cherry. [ABSTRACT FROM AUTHOR]

Izapa is famous for its monumental architecture and extensive corpus of carved stelae dated to the Late Formative Guillén phase (300–100 cal b.c.). The site was first established, however, as the capital of a kingdom during the second half of the Middle Formative period (750–300 cal b.c.). Little is known of the first centuries of the site's occupation or how this early kingdom coalesced with Izapa as its capital. In 2012, the Izapa Regional Settlement Project (IRSP) excavated 21 test units and ran 10 radiocarbon accelerator mass spectrometry (AMS) dates in order to begin correcting this lacuna. These excavations were the first at the site to screen soil matrices and recover artifact samples that can be quantitatively analyzed. We undertook excavations in areas north and south of Group B, the original center of Izapa. This work dates the northern expansion of the site's main platform (under Mound 30a) to the Terminal Formative Itstapa phase (cal a.d. 100–300) that resulted in a doubling of the platform's size. Further, we documented that there were three distinct construction episodes in the Terminal Formative expansion and that a central staircase and ramp were built of stone during the second episode. Buried below the Terminal Formative platform expansion was a white clay surface built during the Escalón phase (750–500 cal b.c.) and used through to Guillén times. At the long, linear Mound 62 that defines the eastern edge of Izapa's site core, we documented two episodes of Guillén-phase monumental construction. Buried below this construction fill at Mound 62, a hearth feature and stone alignment are dated to the late Middle Formative based on radiocarbon assays and the results of ceramic analysis. Excavations at Mound 72 and 73 documented that Izapa's E-Group (newly recognized with lidar [light detection and ranging] data) was established in the late Middle Formative period and then significantly augmented during the Guillén phase. The architectural program at Izapa saw its apogee during the Late Formative period, but was first established during the preceding centuries of the Middle Formative. Ten new AMS dates confirm the dating of the Escalón, Frontera, and Guillén phases to 750–100 cal b.c. Ceramic analysis allowed us to differentiate quantitatively between midden deposits and construction fill through the site's occupation and to recognize domestic versus public spaces during the first centuries of the Izapa kingdom's coalescence. We identify late Middle Formative period middens based on the high density of ceramics in addition to good surface preservation of sherds and a lack of temporal mixing of types. The designation of high-artifact density middens contrasts with the contents of Late and Terminal Formative construction fill with lower ceramic sherd densities and mixing of temporally diagnostic types. Off-mound contexts (where construction fill was mined) had even lower ceramic densities than construction fill and the sherds were very eroded. Analysis of ceramic remains from late Middle Formative period midden deposits also allowed us to infer differences in public and domestic areas of the site during the first centuries of its occupation. Formal and metric variables from these ceramic assemblages identify dish-to-jar ratios that differentiate domestic contexts (with an assortment of vessel forms) from more publically oriented areas of the site (with more serving dishes). The differential distribution of rim diameters of fancy and plain dishes allows us to identify areas of Izapa where domestic activities predominate and indicate that more publically oriented feasting practices occurred at the site center near the main pyramid (Mound 30a) during the late Middle Formative period. [ABSTRACT FROM AUTHOR]

Copyright of Cuadernos de Investigación Geográfica is the property of Universidad de la Rioja, Servicio de Publicaciones 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.)

Soil moisture amount and distribution control evapotranspiration and thus impact the occurrence of convective precipitation. Many recent model studies demonstrate that changes in initial soil moisture content result in modified convective precipitation. However, to quantify the resulting precipitation changes, the chaotic behavior of the atmospheric system needs to be considered. Slight changes in the simulation setup, such as the chosen model domain, also result in modifications to the simulated precipitation field. This causes an uncertainty due to stochastic variability, which can be large compared to effects caused by soil moisture variations. By shifting the model domain, we estimate the uncertainty of the model results. Our novel uncertainty estimate includes 10 simulations with shifted model boundaries and is compared to the effects on precipitation caused by variations in soil moisture amount and local distribution. With this approach, the influence of soil moisture amount and distribution on convective precipitation is quantified. Deviations in simulated precipitation can only be attributed to soil moisture impacts if the systematic effects of soil moisture modifications are larger than the inherent simulation uncertainty at the convection-resolving scale. We performed seven experiments with modified soil moisture amount or distribution to address the effect of soil moisture on precipitation. Each of the experiments consists of 10 ensemble members using the deep convection-resolving COSMO model with a grid spacing of 2.8 km. Only in experiments with very strong modification in soil moisture do precipitation changes exceed the model spread in amplitude, location or structure. These changes are caused by a 50 % soil moisture increase in either the whole or part of the model domain or by drying the whole model domain. Increasing or decreasing soil moisture both predominantly results in reduced precipitation rates. Replacing the soil moisture with realistic fields from different days has an insignificant influence on precipitation. The findings of this study underline the need for uncertainty estimates in soil moisture studies based on convection-resolving models. [ABSTRACT FROM AUTHOR]

Copyright of Acta Scientiarum Polonorum. Formatio Circumiectus is the property of Wydawnictwo Uniwersytetu Rolniczego im. Hugona Kollataja w Krakowie 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.)

Soil water potential (SWP) is a key parameter for characterizing water stress. Typically, a tensiometer is used to measure SWP. However, the measurement range for commercially available tensiometers is limited to 290 kPa and a tensiometer can only provide estimate of SWP at a single location. In this study, a new approach was developed for estimating SWP from spectral reflectance data of a standing rice crop over the visible to shortwave-infrared region (wavelength: 350-2,500 nm). Five water stress treatments corresponding to targeted SWP of 230, 250, 270, 2120, and 2140 kPa were examined by withholding irrigation during the vegetative growth stage of three rice varieties. Tensiometers and mechanistic water flow model were used for monitoring SWP. Spectral models for SWP were developed using partial-leastsquares regression (PLSR), support vector regression (SVR), and coupled PLSR and feature selection (PLSRFS) approaches. Results showed that the SVR approach was the best model for estimating SWP from spectral reflectance data with the coefficient of determination values of 0.71 and 0.55 for the calibration and validation data sets, respectively. Observed root-mean-squared residuals for the predicted SWPs were in the range of 27 to 219 kPa. A new spectral water stress index was also developed using the reflectance values at 745 and 2,002 nm, which showed strong correlation with relative water contents and electrolyte leakage. This new approach is rapid and noninvasive and may be used for estimating SWP over large areas. [ABSTRACT FROM AUTHOR]

The main environmental stresses of Italian croplands are discussed in relation to their interactions with ozone effects on crops. Water deficit and salinization are frequent in Mediterranean environments during spring-summer causing a decrease of soil water potential and water uptake by roots and consequently stomatal closure. These stresses also stimulate secondary metabolism and antioxidant accumulation, which also serves as a stress protection mechanism. High concentrations of tropospheric ozone are common all over Italy during the spring-summer season. Ozone injuries to vegetation are related to its penetration into plant tissues, mostly via stomatal uptake, rather than to tropospheric concentrations per se. In several crops, closure of stomata due to drought/salinization reduces ozone entering into leaf tissues and counteracts possible ozone damages. Furthermore, the stimulation of antioxidant synthesis as a response to environmental stresses can represent a further protection factor from ozone injuries for Mediterranean crops.The co-existence of stress-induced stomatal closure and high ozone levels during spring-summer in Mediterranean environments implies that models that do not take into account physiological responses of crops to drought and salinity stress may overestimate ozone damages when stress responses overlap with seasonal ozone peaks. The shift from concentration-based to flux-based approaches has improved the accuracy of models to assess ozone effects on agricultural crops. It is, however, necessary to further refine the flux concept with respect to the plant abiotic stress defense capacity that can differ among genotypes, climatic conditions, and physiological states. [ABSTRACT FROM AUTHOR]

One of the main limitations in applying fertilisers at a variable rate according to soil requirements is the number of samples required to spatially represent soil attributes. Currently, to map soil attributes with high accuracy, a high sample density is needed, which is often unfeasible. One technique that minimizes the number of samples required is the use of maps that have prior information of the soil spatial variability, making it possible to identify representative sampling locations in the field. Soil apparent electrical conductivity (ECa) is a powerful indicator of the characteristics of the soil matrix, and it can be easily measured. The objectives of this study were to determine the efficacy of ECa for mapping the spatial variability of soil properties using a targeted and reduced number of samples (which is economically feasible for growers). A high sampling density was applied in an experimental sugarcane field to assess the spatial variability of soil attributes, and ECa was read by a direct contact sensor. Thematic maps of important agronomic attributes were generated using the high sample density and compare with a targeted and reduced sampling helped by ECa measurements. The methodology used to obtain the spatial variability maps of soil chemical and physical properties indicated that it was possible to obtain maps of acceptable accuracy (r = 0.82 and 0.59 for clay and pH, respectively) that could be used to formulate lime recommendations for variable-rate applications. The total lime spent (28 tons) based on the application maps generated by a targeted sampling mesh (20 sampling points) was very similar to that (30 tons) obtained based on high-density sampling (204 sampling points), representing a large improvement in soil sampling methodology. Here we demonstrated that ECa can improve prediction maps and enables efficient sample orientation. This approach provides an interesting way to map soil properties over large areas using a feasible sampling method and can help farmers in crop management while respecting environmental and soil requirements. [ABSTRACT FROM AUTHOR]

Large-scale vegetation restoration on the Loess Plateau in China has been performed by the central government in recent decades; however, the planting of incompatible vegetation during these efforts has resulted in serious environmental problems, such as dry soil layers, that are widespread and difficult to ameliorate. To determine the proper evaluation indices for plant available soil water content (PASWC) in commonly reforested plants and crops, we examined the physiological responses of Robinia pseudoacacia (tree), Amorpha fruticosa (shrub), Medicago sativa (perennial leguminous herb) and Zea mays (crop) to prolonged drought; these plants were planted widely in the semiarid Loess Plateau region of China. Leaf water status, gas exchange and fluorescence parameters did not show marked changes at the beginning of the prolonged drought but changed rapidly as PASWC continued to decrease. These data were fitted with a sigmoid function ( P < 0.0001). In addition, different physiological parameters showed different PASWC thresholds; the fluorescence parameters exhibited the lowest PASWC threshold among the four species, with an upper threshold that was less than 50% of the PASWC for all but Z. mays . In this study, the photosynthesis rate was a better indicator of the PASWC, and the upper and lower thresholds of PASWC of the normalized photosynthesis rate were 64.1% and 47.6%, 83.0% and 44.1%, 82.7% and 35.2%, 82.9% and 39.3% for R. pseudoacacia , A. fruticosa , M. sativa and Z. mays , respectively. The current study also suggests that R. pseudoacacia is a suitable afforestation species in areas with higher levels of rainfall. These results provide important information for determining the PASWC and the supply capacity of soil water on the Loess Plateau. [ABSTRACT FROM AUTHOR]

Information on N management in organic flue-cured tobacco production is limited. Research was conducted from 2012-2013 to determine the effects of two certified organic N sources applied at three rates on the yield, quality, and chemical constituents of flue-cured tobacco. These organic N sources included Nature Safe 13-0-0 (NS) and Nutrimax 12-1-0 (NM), both of which consisted of hydrolyzed poultry feather meal. Application rates for both fertilizer sources were 17 kg N ha-1 above recommendation (B+), at recommendation (B), and 17 kg N ha-1 below recommendation (B-). A conventional control containing ureaammonium-nitrate (UAN) was applied at the B application rate. Tobacco yield and quality were similar among conventional and organic N programs. Leaf N concentration, SPAD measurements at flowering, and total alkaloid concentration of cured leaves responded positively to increased N application rates, regardless of organic fertilizer source. The largest increases in nitrogenousbased leaf constituents were observed in this study where B+ treatments were applied; however, those increases did not translate into increased leaf yield or quality and could delay the initiation of leaf senescence in growing seasons with low soil moisture. Results from this study demonstrate the acceptability of poultry feather meal sources for organic tobacco production, and confirm that application rates of organic N sources should follow conventional recommendations. [ABSTRACT FROM AUTHOR]

Silver birch ( Betula pendula Roth) allocates substantial resources to the production of glandular trichomes. If these trichomes can protect trees from temperature and water stress, their production would be expected to increase under these conditions. We studied how glandular trichome density and number in the leaves of two-year-old silver birch plantlets respond to single and combined treatments of elevated temperature (+1 °C) and three different levels of soil moisture (low, normal, and excess watering). Moreover, we quantified the seasonal variation in trichome density in mature long-shoot leaves of young, greenhouse-grown silver birches. Our results demonstrate clear differences between responses of glandular trichomes on different leaf surfaces. On the adaxial leaf surface, both drought and elevated temperature reduced the production of glandular trichomes. Interestingly, this response was absent in plants subjected to the combined treatment. Glandular trichome production on the abaxial leaf surface increased considerably in leaves produced during the growing season, reflecting a seasonal trend. Maintaining a strong seasonal increase in trichome production of abaxial surfaces even in low-water conditions suggests an important, though still unknown, role for abaxial glandular trichomes. In silver birch stems, those trichomes are strongly responsible for herbivore defense. [ABSTRACT FROM AUTHOR]

Biogenic volatile organic compounds (BVOCs) are continually emitted from plants and are also a component of smoke during vegetation fire. Although vegetation fire events have been shown to have implications for the dynamics of soil water repellency (SWR) and there have been anecdotal reports that forest smoke can induce water repellency, the role of BVOCs in this process has not been explored. Accordingly, we investigated a selection of major BVOCs (cis-3-hexen-1-ol; levoglucosenone; 2-methyl-3-buten-2-ol; cineole; α-phellandrene; α-terpinene) that are emitted from the dominant native vegetation of Australia during fire. The potential of each compound to induce SWR was investigated by applying different loadings on acid washed sand (AWS) (300-350 µm diameter) and then assessing water repellency with the molarity of ethanol drop test. A long-chain amphiphilic molecule (palmitic acid) was also applied to AWS for comparison. Although palmitic acid was effective at inducing water repellency, the BVOCs were not, even at high loadings (5 × 10 mol g). Fully atomistic molecular dynamics simulations complemented the experimental measurements. These studies suggested that poor expression of water repellency by the BVOCs could be explained by their tendency to exhibit weak interactions towards the quartz surface but strong molecule-molecule attractions. In comparison, the long-chain amphiphilic molecules exhibited a balance between molecule-molecule and molecule-surface interactions that favored surface adhesion, which in turn led to the formation of a hydrophobic layer. [ABSTRACT FROM AUTHOR]

Soil moisture is the main limiting factor for vegetation growth at shell ridges in the Yellow River Delta of China. The objective of this study was to explore the soil moisture response of photosynthetic parameters and transpiration in Tamarix chinensis Lour., a dominant species of shell ridges. Leaf photosynthetic light-response parameters and sap flow were measured across a gradient of relative soil water content (RWC), from drought (23%) to waterlogging (92%) conditions. Leaf photosynthetic efficiency and stem sap flow of T. chinensis showed a clear threshold response to soil moisture changes. Leaf net photosynthetic rate, water-use efficiency (WUE), light-saturation point, apparent quantum yield, maximum net photosynthetic rate, and dark respiration rate peaked at moderately high RWC, decreasing towards high and low values of RWC. However, peak or bottom RWC values substantially differed for various parameters. Excessively high or low RWC caused a significant reduction in the leaf photosynthetic capacity and WUE, while the high photosynthetic capacity and high WUE was obtained at RWC of 73%. With increasing waterlogging or drought stress, T. chinensis delayed the starting time for stem sap flow in the early morning and ended sap flow activity earlier during the day time in order to shorten a daily transpiration period and reduce the daily water consumption. The leaf photosynthetic capacity and WUE of T. chinensis were higher under drought stress than under waterlogging stress. Nevertheless, drought stress caused a larger reduction of daily water consumption compared to waterlogging, which was consistent with a higher drought tolerance and a poor tolerance to waterlogging in this species. This species was characterized by the low photosynthetic capacity and low WUE in the range of RWC between 44 and 92%. The RWC of 49-63% was the appropriate range of soil moisture for plant growth and efficient physiological water use of T. chinensis seedlings. [ABSTRACT FROM AUTHOR]

Sensitivity analysis and multiobjective optimisation are established diagnostic instruments for the identification of uncertainty factors and structural deficits in environmental simulation models. Although the application of both techniques provides a comprehensive understanding of model behaviour, they are seldom practised in combination. In this study, the Sobol global sensitivity method and the multiobjective algorithm AMALGAM are combined to assess the agro-hydrological SWAP model for simulating the soil water balance of different sole and mixed crops based on hydrological and phenological field observations. Fifteen unknown model parameters are subjected to the sensitivity analysis (GSA) with the aim of finding their importance to model performance of matric potential ( F ) and soil water content ( F ). Subsequently, sensitive parameters are calibrated by optimising F and F simultaneously. The GSA showed that the description of the rooting density and potential evapotranspiration is of crucial important to F , and that soil properties are most relevant for F . Parameter interactions played a primary role in the response of matric potential, being irrelevant for F . Structural model deficiencies in reproducing both objectives simultaneously were found in the multiobjective analysis, meaning that deterioration in the fit to one of the objectives is in favour of the other. However, solutions exist that produce satisfying fits to both observational types, suggesting that the SWAP model has the capability of simulating the soil water balance of the crops considered. The results of the evaluation period revealed model deficiencies in simulating the process under an environmental regime significantly different from that of the calibration period, indicating the necessity of acquiring a broader spectrum of environmental regimes for parameter calibration. Overall, this study demonstrates how complex and variable the relationship between parameters and model outputs can be in environmental models and highlights the value of combining global sensitivity analysis and multiobjective optimisation in order to improve model performances. [ABSTRACT FROM AUTHOR]

Recently, a method based on the soil water flux (F)-saturation (Q) relationship, F(Q), assumed to be independent of time and soil properties, has become an important technique to simplify solving Richards' equation so as to develop a simple, rapid, and low-cost approach to estimate soil hydraulic properties. However, the actual F(Q) is soil pore-structure dependent. So far, there exists no theory that can provide a specific functional form of soil pore-structure-dependent F(Q). In this research, we derived a general soil moisture profile function and then a general expression of F(Q): F = Q[1 + a2(1 − Q 2 1/a)]. The only parameter in F(Q), a2, is a function of the initial soil water saturation and the soil pore structure index that reflects the shape of the soil water retention curve. Infiltration experiments with three test soils and four actual soils were conducted to test the proposed relationships. The results verified the independence of F(Q) on time at small time scales. The results also indicated that the derived formula predicted F(Q) in good agreement with what was measured for all test soils under different initial soil moisture conditions. In addition, the upper and lower limit curves of F(Q) calculated by the proposed formula were consistent with the theoretical curves. Compared with other empirical relationships, the new formula was the best for describing the theoretical upper limit curve of F(Q). Furthermore, the new theoretical relationship was also found to be appropriate for horizontal absorption. Generally, the developed relationship is more accurate and helpful to solve Richards' equation. [ABSTRACT FROM AUTHOR]

In one of the widely used methods to estimate surface runoff - Soil Conservation Service Curve Number (SCS-CN), the antecedent moisture condition (AMC) is categorized into three AMC levels causing irrational abrupt jumps in estimated runoff. A few improved SCS-CN methods have been developed to overcome several in-built inconsistencies in the soil moisture accounting (SMA) procedure that lies behind the SCS-CN method. However, these methods still inherit the structural inconsistency in the SMA procedure. In this study, a modified SCS-CN method was proposed based on the revised SMA procedure incorporating storm duration and a physical formulation for estimating antecedent soil moisture ( V ). The proposed formulation for V estimation has shown a high degree of applicability in simulating the temporal pattern of soil moisture in the experimental plot. The modified method was calibrated and validated using a dataset of 189 storm-runoff events from two experimental watersheds in the Chinese Loess Plateau. The results indicated that the proposed method, which boosted the model efficiencies to 88% in both calibration and validation cases, performed better than the original SCS-CN and the Singh et al. (2015) method, a modified SCS-CN method based on SMA. The proposed method was then applied to a third watershed using the tabulated CN value and the parameters of the minimum infiltration rate ( f ) and coefficient ( β) derived for the first two watersheds. The root mean square error between the measured and predicted runoff values was improved from 6 mm to 1 mm. Moreover, the parameter sensitivity analysis indicated that the potential maximum retention ( S) parameter is the most sensitive, followed by f . It can be concluded that the modified SCS-CN method, may predict surface runoff more accurately in the Chinese Loess Plateau. [ABSTRACT FROM AUTHOR]

This study aimed at assessing the effects of increased air temperature and reduced soil moisture content on the multi-generation toxicity of a soil polluted by metal/metalloid mining wastes. Enchytraeus crypticus was exposed to dilution series of the polluted soil in Lufa 2.2 soil under different combinations of air temperature (20 °C and 25 °C) and soil moisture content (50% and 30% of the soil water holding capacity, WHC) over three generations standardized on physiological time. Generation time was shorter with increasing air temperature and/or soil moisture content. Adult survival was only affected at 30% WHC (∼30% reduction at the highest percentages of polluted soil). Reproduction decreased with increasing percentage of polluted soil in a dose-related manner and over generations. Toxicity increased at 30% WHC (>50% reduction in EC 50 in F0 and F1 generations) and over generations in the treatments at 20 °C (40–60% reduction in EC 50 in F2 generation). At 25 °C, toxicity did not change when combined with 30% WHC and only slightly increased with 50% WHC. So, higher air temperature and/or reduced soil moisture content does affect the toxicity of soils polluted by metal/metalloid mining wastes to E. crypticus and this effect may exacerbate over generations. [ABSTRACT FROM AUTHOR]

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Soil compaction occurs widely in modern agriculture, leading to reduced crop yields and enhanced soil N 2 O emissions. Biochar, an emerging biomass-pyrolysis product with porous structure, is hypothesized to alleviate soil compaction problems. A field mesocosm experiment involving biochar addition and soil compaction in a factorial design was conducted on a land cultivated with wheat. The results showed that biochar had little effect on wheat grain yield, but it increased wheat vegetative growth and reduced seasonal cumulative soil N 2 O emissions from both compacted and non-compacted soils. Across all treatments, biochar-induced changes in individual soil N 2 O fluxes mainly occurred within a couple of days after nitrogen fertilization, and were sensitive to soil moisture, with an average increase of 13% under low soil moisture conditions (<70% water holding capacity (WHC)) that was likely driven by increased abundance of ammonia-oxidizing archaea and bacteria, and an average decrease of 36% under high soil moisture conditions (>70% WHC) that was likely induced by raised abundance of N 2 O-reducing bacteria. The stimulated population sizes of nitrifiers and denitrifiers in biochar-amended soils were more dependent on biochar's chemical mediation (a shift of soil pH from moderate acidity towards neutrality) than physical mediation. This study indicated that biochar could alleviate soil compaction stress on wheat growth and mitigate soil N 2 O emissions, and to promote biochar's role in reducing soil N 2 O emissions, the best practice for nitrogen fertilization is before precipitation or followed by irrigation. [ABSTRACT FROM AUTHOR]

The regularities of moisture behavior in the system of surface air - vegetation cover - soil with the use of moisture potential are established. It is shown that the moisture potential in soil, leaves of plants, changes in the moisture potential in the soil-plant system, and relative transpiration is related to functional dependencies. It is well established that each group plants (hygrophytes, mesophytesand xerophytes) is characterized a certain narrow range of soil moisture potential, in which the relative transpiration values do not fall below the optimal level (1.0-0.9). This interval is virtually independent of soil properties and meteorological conditions и can be used as the optimal criterion for plant moisture supply.

Water percolation and flow processes in subsurface geologic media play an important role in determining the water source for plants and the transport of contaminants or nutrients, which is essential for water resource management and the development of measures for pollution mitigation. During June 2013, the dynamics of the rainwater, soil water, subsurface flows and groundwater in a shallow Entisol on sloping farmland were monitored using a hydrometric and isotopic approach. The results showed that effective mixing of rainwater and soil water occurred in hours. The rebound phenomenon of δD profiles in soils showed that most isotope-depleted rainwater largely bypassed the soil matrix when the water saturation in the soil was high. Preferential-flow, which was the dominant water movement pattern in the vadose zone, occurred through the whole soil profile, and infrequent piston-flow was mainly found at 20-40 cm in depth. The interflow in the soil layer, composed of 75.2% rainwater, was only generated when the soil profile had been saturated. Underflow in the fractured mudrock was the dominant flow type in this hillslope, and outflow was dominated by base flow (groundwater flow) with a mean contribution of 76.7%. The generation mechanism of underflow was groundwater ridging, which was superimposed upon preferential-flow composed mainly of rainwater. The quick mixing process of rainwater and soil water and the rapid movement of the mixture through preferential channels in the study soil, which shows a typical bimodal pore size distribution, can explain the prompt release of pre-event water in subsurface flow. Water sources of subsurface flows at peak discharge could be affected by the antecedent soil water content, rain characteristics and antecedent groundwater levels. Copyright © 2016 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Soil hydraulic properties (SHPs) control infiltration and redistribution of moisture in a soil column. The Noah land surface model (LSM) default simulation selects SHPs according to a location's mapped soil texture class. SHPs are instead estimated at seven sites in North America through calibration. A single-objective algorithm minimizes the root-mean-square difference (RMSD) between simulated surface soil moisture and observations from 1) a dense network of in situ probes, 2) Soil Moisture Ocean Salinity (SMOS) satellite retrievals, and 3) SMOS retrievals adjusted such that their mean equals that of the in situ network. Parameters are optimized in 2012 and validated in 2013 against the in situ network. RMSD and unbiased RMSD (ubRMSD) assess resulting surface soil moisture behavior. At all sites, assigning SHP parameters from a different soil texture than the one that is mapped decreases the RMSD by an average of 0.029 cm3 cm−3. Similar improvements result from calibrating parameters using in situ network data (0.031 cm3 cm−3). Calibrations using remotely sensed data show comparable success (0.029 cm3 cm−3) if the SMOS product has no bias. Calibrated simulations are superior to texture-based simulations in their ability to decrease ubRMSD at times of year when the default simulation is worst. Changes to both RMSD and ubRMSD are small when the default simulation is already good. Most calibrated simulations have higher runoff ratios than do texture-based simulations, a change that warrants further evaluation. Overall, parameter selection using SMOS data shows good potential where biases are low. [ABSTRACT FROM AUTHOR]

Precision and accuracy of DFM capacitance probes with temperature sensors were evaluated for measuring temperature. Two sets of DFM probes were used in this experiment, one set of 17 for testing the performance of the temperature sensors and the other set of 16 probes to evaluate how to improve the accuracy of measurements of the DFM temperature sensors. Standard deviation (SD) as a measure of precision shows that the range of precision for the all the observations was 0.15–1.08 °C. The accuracy of the device, using means of the absolute errors, for measuring temperature was ±1.28 °C. The DFM temperature sensors were able to measure temperature with high precision while the accuracy of the measurements was improved with calibration procedure. The accuracy was improved up to ±0.06 °C with the calibration procedure. It was concluded from the study that the device is suitable for measuring temperature effectively. Using equation derived during calibration procedure before installation of the device will increase sensors performance in terms of temperature measurements accuracy. The DFM capacitance probe is durable, with easy logging, and data management of high accuracy and precision or repeatability. It can also simultaneously collect data on multiple parameters such as soil water and soil temperature. [ABSTRACT FROM AUTHOR]

This paper documents the capability of the ARW/WRF regional climate model to regionalize near-surface atmospheric variables at high resolution (8 km) over Burgundy (northeastern France) from daily to interannual timescales. To that purpose, a 20-year continuous simulation (1989-2008) was carried out. The WRF model driven by ERA-Interim reanalyses was compared to in situ observations and a mesoscale atmospheric analyses system (SAFRAN) for five near-surface variables: precipitation, air temperature, wind speed, relative humidity and solar radiation, the last four variables being used for the calculation of potential evapotranspiration (ET). Results show a significant improvement upon ERA-Interim. This is due to a good skill of the model to reproduce the spatial distribution for all weather variables, in spite of a slight over-estimation of precipitation amounts mostly during the summer convective season, and wind speed during winter. As compared to the Météo-France observations, WRF also improves upon SAFRAN analyses, which partly fail at showing realistic spatial distributions for wind speed, relative humidity and solar radiation-the latter being strongly underestimated. The SAFRAN ET is thus highly under-estimated too. WRF ET is in better agreement with observations In order to evaluate WRF's capability to simulate a reliable ET, the water balance of thirty Douglas-fir stands was computed using a process-based model. Three soil water deficit indexes corresponding to the sum of the daily deviations between the relative extractible water and a critical value of 40 % below which the low soil water content affects tree growth, were calculated using the nearest weather station, SAFRAN analyses weather data, or by merging observation and WRF weather variables. Correlations between Douglas-fir growth and the three estimated soil water deficit indexes show similar results. These results showed through the ET estimation and the relation between mean annual SWDI and Douglas-fir growth index that the main difficulties of the WRF model to simulate soil water deficit is mainly attributable to its precipitation biases. In contrast, the low discrepancies between WRF and observations for air temperature, wind speed, relative humidity and solar radiation make then usable for the water balance and ET computation. [ABSTRACT FROM AUTHOR]

Soil amending with biochar has been viewed as a sustainable way to improve soil moisture holding capacity. The potential of biochar application to improve water status of crops under drought stress has not been extensively evaluated. In this study, we evaluated the impact of biochar application (0%, 1%, and 2% w/w soil) on some important physiological traits of milk thistle (Silybum marianumL. Gaertn) under moderate and severe drought stress conditions in a controlled environment. Although, the application of biochar at the higher rate slightly improved soil moisture holding capacity, the magnitude of its effect was not sufficient to influence plant performance under drought stress. To get the positive effects of biochar application on milk thistle performance under drought stress, application with higher rates is probably necessary. [ABSTRACT FROM AUTHOR]

The Temperature Vegetation Dryness Index (TVDI) was derived from the relationship between remotely sensed vegetation indices and land surface temperature (TS) in this study for assessing the soil moisture status at regional scale in South Korea. The Leaf Area Index (LAI) is newly applied in this method to overcome the increasing uncertainty of using the Normalized Difference Vegetation Index (NDVI) at high vegetation conditions. Both dryness indices were found to be well correlated with in situ soil moisture and 8-day average precipitation at most of the in situ measurement sites. The dryness indices accuracy was found to be influenced by rainfall events. An average correlation coefficient was improved from -0.253 to -0.329 when LAI was used instead of NDVI in calculating the TVDI. In the spatial analysis between the dryness indices and Advanced SCATterometer (ASCAT) surface soil moisture (SSM) using geographically weighted regression (GWR), the results showed the average negative correlation (R) between the variables, while LAI-induced TVDI was more strongly correlated with SSM on average with the R value improved from -0.59 to -0.62. Both dryness indices and ASCAT SSM mappings generally showed coherent patterns under low vegetation and dry conditions. Based on these results, the LAI-induced TVDI accuracy as an index for soil moisture status was validated and found appropriate for use as an alternative and complementary method for NDVI-induced TVDI. [ABSTRACT FROM AUTHOR]

Gas exchange and photosystem II (PSII) activities in the leaves of 2-year-old 'Bluecrop' highbush blueberry (Vaccinium corymbosum) were monitored during water stress and subsequent re-irrigation to investigate the effects of the intensity of water stress on changes in photosynthetic characteristics. The blueberry shrubs were not irrigated for 3 to 5 weeks, then re-irrigated daily up to 8 weeks. The decrease in soil water potential during water stress caused a progressive decrease in leaf water potential. Soil water potentials decreased to -0.26 MPa and -0.34 MPa at 3 and 5 weeks, respectively, following water stress, but recovered following subsequent re-irrigation, while the soil water potential in daily-irrigated shrubs was maintained at over -0.13 MPa throughout the experiment. Chlorophyll concentrations decreased with an increasing duration of water stress. Chlorophyll concentrations in leaves on shrubs subjected to water stress for 5 weeks did not recover following re-irrigation, unlike those subjected to water stress for 3 weeks. The leaves on shrubs subjected to water stress for 5 weeks maintained lower levels of chlorophyll during reirrigation. The net rate of C 0 2 assimilation (A„) decreased significantly with anincreasing duration of water stress. Reirrigation reversed the decrease in A„ in leaves on shrubs subjected to water stress for 3 weeks. Stomatal conductance (gs) exhibited a similar pattern to A„. The actual quantum yield of photosystem Π (ΦPSΠ) and the electron transport rate (ETR) also decreased significantly with anincreasing duration of water stress, although the FvIFm ratio was not affected. ΦPSΠ and ETR values in the leaves on shrubs subjected to water stress for 5 weeks did not recover after reirrigation, unlike those subjected to water stress for 3 weeks. Non-photochemical quenching increased with an increasing duration of water stress, but subsequent re-irrigation did not reverse the increase. These results indicate that the timing of re-irrigation of water-stressed 'Bluecrop' highbush blueberry is critical in order to maintain their photosynthetic capacity. Among the photosynthetic characteristics measured, ΦPSΠ and ETR could be used as sensitive indicators to assess the physiological status of leaves of 'Bluecrop' highbush blueberry growing under water stress conditions. [ABSTRACT FROM AUTHOR]

Heat dissipation sensors are used to measure matric potential in soils. A van Genuchten equation can be used to it the relationship between measured heat dissipation and matric potential. Calibration is required for each probe because of intrinsic variability in the properties of the porous material. However, calibration is time-consuming (months), requiring numerous measurements taken by a pressure plate apparatus over their operational range. Here the feasibility of minimizing the number of measurement points required to reliably characterize the calibration curve is explored. A two parameter (m = 1-1/n) and a three parameter (m is a free parameter) van Genuchten type model is used for the calibration. We explore how reducing the number of calibration measurement points impacts the resulting calibration curve, that is, what is the information content that each measurement provides, and how significantly is the calibration performance degraded by removing measurement points. We also consider how measurement errors during the calibration process, which are understood to be non-uniform over the range of matric potential values, result in uncertainty in the calibration curve, and explore how this uncertainty can be minimized. Different measurement locations (i.e., matric potential values) are found to contain different information content. A two-parameter-model calibration using four calibration points is recommended; and the specific location of these four points is essential to maximize the accuracy and the efficiency of the calibration. As a rule of thumb, the four points should be uniformly distributed on a log-scale over the pressure range from 20 to 1000 kPa. [ABSTRACT FROM AUTHOR]

Radovesice Dump is a part of brown-coal Most basin, which is situated in the northern part of the Czech Republic. Grey clays are the anthropogenic substrates, which have been used here as a reclamation material in most cases. Water potential of these substrates corresponds to their physical properties, annual precipitation, soil temperature and terrain exposition. All of these characteristics are the limiting factors of soil water, which is available to plants. Area left to spontaneous succession and reclaimed area served as the serviced ones. Water potential was studied in three depths (10, 20 and 30 cm) of soil profile and the evaluated values showed significant difference between individual depths as well as exposition. As far as chemical analyses are concerned, the highest values were recorded in case of reclaimed area, whereas the levels of soil moisture here were medium. On the other hand, area left to spontaneous succession showed the lowest values in this sense, however specific representation of vegetation was much large-scale. As far as microbiological characteristics are concerned, the concentrations of phospholipid fatty acids were relatively low in both cases. To the dominant herb species belonged Calamagrostis epigejos, Urtica dioica, Alopecurus pratensis and Astragalus glycyphyllos. It was found that spontaneous succession was more variable as far as the specific representation of vegetation is concerned, though favourable soil physical and chemical properties were provided by technical reclamation too.. [ABSTRACT FROM AUTHOR]

Thousand cankers disease ( TCD), a lethal fungal dieback of eastern black walnut ( Juglans nigra), caused by Geosmithia morbida, and spread by the walnut twig beetle, Pityophthorus juglandis, was documented in 2009 to be very destructive in the western United States and was identified in the native range of J. nigra at Knoxville, Tennessee, in 2010, and in 2011 at Richmond, Virginia. Beginning late 2010, we studied branch dieback levels (per cent live crown) and new TCD symptom development at these two quarantined locations monthly for 3 years. Of the 106 trees studied (53 at each location), 31 trees had low live crown ratings of 70 to 0% with little change over the 3 years of the study. One per cent of the trees developed new symptoms on a per-year basis. Thus, a moderate level of TCD (mean = 76% live crown) was present in these two locations, and most trees were in a quiescent or dormant TCD condition for 3 years, an important finding not previously reported. We found new TCD symptoms developed in Richmond in 2011 and 2012 when precipitation from January 1 to the end of August was low (60-64 cm), and not when the precipitation in Richmond was higher (99 cm). In late 2012, in Richmond, soil water potential assays indicated that some black walnut trees were under severe physiological stress (−15 bars). In contrast, in 2013, high precipitation levels (99 and 130 cm) and high soil water potentials (−0.1 to −3 bars) at both locations were associated with extensive new foliage and stem growth and recovery from TCD. Further research is needed on water relationships in regard to TCD and black walnut health. [ABSTRACT FROM AUTHOR]

The rainfall-runoff process (RRP) is an important part of hydrologic process. There is an effective measure to sttages (jointiudy RRP through artificial rainfall simulation. This paper describes a study on three growing sng stage, tasseling stage, and mature stage) of spring maize in which simulated rainfall events were used to study the effects of various factors (rainfall intensity and slope gradient) on the RRP. The RRP was tested with three different rainfall intensities (0.67, 1.00, and 1.67 mm/min) and subjected to three different slopes (5°, 15°, and 20°) so as to study RRP characteristics in semiarid regions. Regression analysis was used to study the results of this test. The following key results were obtained: (1) With the increase in rainfall intensity and slope, the increasing relationship with rainfall duration, overland flow, and cumulative runoff, respectively, complied with logarithmic and quadratic functions before reaching stable runoff in each growing stage of spring maize; (2) The runoff coefficient increased with the increase in rainfall intensity and slope in each growing stages of spring maize. The relationship between runoff coefficient, slope, rainfall intensity, rainfall duration, antecedent soil moisture, and vegetation coverage was multivariate and nonlinear; (3) The runoff lag time decreased with the increase in rainfall intensity and slope within the same growing stage. In addition, the relationship between runoff lag time, slope, rainfall intensity, antecedent soil moisture, and vegetation coverage could also be expressed by a multivariate nonlinear equation; (4) The descent rate of soil infiltration rate curve increased with the increased rainfall intensity and slope in the same growing stage. Furthermore, by comparing the Kostiakov, Horton, and Philip models, it was found that the Horton infiltration model was the best for estimating soil infiltration rate and cumulative infiltration under the condition of test. [ABSTRACT FROM AUTHOR]

Investigation of the temperature effects on the water retention properties of compacted bentonite is of great importance in the context of geological disposal of high-level radioactive waste (HLW) based on the multi-barrier concept. Gaomiaozi (GMZ) bentonite, collected from the Inner Mongolia Autonomous Region of China, has been selected as a potential buffer/backfill material for the construction of Chinese HLW deep geological repository. In this study, soil water retention curves (SWRCs) of both confined and unconfined compacted GMZ01 bentonite specimens with an initial dry density of 1.70 g/cm were investigated at temperatures 20, 40, 60 and 80 °C. Results indicate that the water content decreases as temperature rises, even though the temperature effects on the water retention capacity of compacted GMZ01 bentonite depend on constraint-conditions. The influence of constraint conditions is more significant at relatively low suctions. Under unconfined conditions, the temperature effect is insignificant. However, under confined conditions, the influence on the water retention capacity is found to be significantly suction dependent. The hysteresis behavior of unconfined compacted bentonite becomes less significant as temperature increases. Based on the corresponding results obtained, a modified model was developed for describing the SWRCs of confined compacted GMZ01 bentonite with consideration of temperature effects. It appears that the calculated SWRCs agree well with the experimental ones, indicating that the modified model can satisfactorily describe the effect of temperature on the water retention properties of confined compacted GMZ01 bentonite. [ABSTRACT FROM AUTHOR]

The IGCM4 (Intermediate Global Circulation Model version 4) is a global spectral primitive equation climate model whose predecessors have extensively been used in areas such as climate research, process modelling and atmospheric dynamics. The IGCM4's niche and utility lies in its speed and flexibility allied with the complexity of a primitive equation climate model. Moist processes such as clouds, evaporation, atmospheric radiation and soil moisture are simulated in the model, though in a simplified manner compared to state-of-the-art global circulation models (GCMs). IGCM4 is a parallelised model, enabling both very long integrations to be conducted and the effects of higher resolutions to be explored. It has also undergone changes such as alterations to the cloud and surface processes and the addition of gravity wave drag. These changes have resulted in a significant improvement to the IGCM's representation of the mean climate as well as its representation of stratospheric processes such as sudden stratospheric warmings. The IGCM4's physical changes and climatology are described in this paper. [ABSTRACT FROM AUTHOR]

Persistent soil moisture deficits during flowering and yield formation stage are referred to as late-season agricultural drought. This study aims to assess late-season agricultural drought in cotton- and millet-growing districts of Andhra Pradesh, India, during summer cropping season 2011. Satellite-based indices like the Normalized Difference Vegetation Index, Normalized Difference Water Index and their Vegetation Condition Index from MODIS were analyzed. The root zone Soil Moisture Index (SMI) using soil water balance model for cotton and millet (sorghum and pearl millet) crops was derived to evaluate the soil moisture status. The analysis was carried out by comparing the satellite-derived indices with the previous normal years, and the assessments were made. The satellite-based indices clearly brought out the stress that the crop endured during late October and November, while SMI indicated soil water stress in early October. The soil- and crop-specific SMI's were able to clearly indicate the exact period of water stress. The results show that millet crop was able to escape drought due to sufficient rainfall and its shorter duration, while cotton crop did not have enough soil moisture during the critical stage of flowering and boll formation and suffered severe yield loss due to the late-season agricultural drought. [ABSTRACT FROM AUTHOR]

A substantial number of models predicting the soil moisture characteristic curve (SMC) from particle size distribution (PSD) data underestimate the dry range of the SMC especially in soils with high clay and organic matter contents. In this study, we applied a continuous form of the PSD model to predict the SMC, and subsequently we developed a physically based scaling approach to reduce the model's bias at the dry range of the SMC. The soil particle packing density was considered as a metric of soil structure and used to define a soil particle packing scaling factor. This factor was subsequently integrated in the conceptual SMC prediction model. The model was tested on 82 soils, selected from the UNSODA database. The results show that the scaling approach properly estimates the SMC for all soil samples. In comparison to the original conceptual SMC model without scaling, the scaling approach improves the model estimations on average by 30 %. Improvements were particularly significant for the fine- and medium-textured soils. Since the scaling approach is parsimonious and does not rely on additional empirical parameters, we conclude that this approach may be used for estimating SMC at the larger field scale from basic soil data. [ABSTRACT FROM AUTHOR]

The article focuses on the evaluation of soil moisture (SM) product from Advanced Synthetic Aperture Radar (ASAR) data and in-situ measurements in Ireland. Topics include the use of Essential Climate Variable (ECV) pixel, the different sets of ASAR and in-situ data. Several charts are also presented which describe the process of generating ECV SM product and the approaches for the analysis of SM products.

Large-scale hydrological models are nowadays mostly calibrated using observed discharge. As a result, a large part of the hydrological system, in particular the unsaturated zone, remains uncalibrated. Soil moisture observations from satellites have the potential to fill this gap. Here we evaluate the added value of remotely sensed soil moisture in calibration of large-scale hydrological models by addressing two research questions: (1) Which parameters of hydrological models can be identified by calibration with remotely sensed soil moisture? (2) Does calibration with remotely sensed soil moisture lead to an improved calibration of hydrological models compared to calibration based only on discharge observations, such that this leads to improved simulations of soil moisture content and discharge? A dual state and parameter Ensemble Kalman Filter is used to calibrate the hydrological model LISFLOOD for the Upper Danube. Calibration is done using discharge and remotely sensed soil moisture acquired by AMSR-E, SMOS, and ASCAT. Calibration with discharge data improves the estimation of groundwater and routing parameters. Calibration with only remotely sensed soil moisture results in an accurate identification of parameters related to land-surface processes. For the Upper Danube upstream area up to 40,000 km2, calibration on both discharge and soil moisture results in a reduction by 10-30% in the RMSE for discharge simulations, compared to calibration on discharge alone. The conclusion is that remotely sensed soil moisture holds potential for calibration of hydrological models, leading to a better simulation of soil moisture content throughout the catchment and a better simulation of discharge in upstream areas. [ABSTRACT FROM AUTHOR]

Faced with declining soil-water potential, plants synthesize abscisic acid ( ABA), which then triggers stomatal closure to conserve tissue moisture. Closed stomates, however, also create several physiological dilemmas. Among these, the large CO2 influx required for net photosynthesis will be disrupted. Depleting CO2 in the plant will in turn bias stomatal opening by suppressing ABA sensitivity, which then aggravates transpiration further. We have investigated the molecular basis of how C3 plants resolve this H2O- CO2 conflicting priority created by stomatal closure. Here, we have identified in Arabidopsis thaliana an early drought-induced spermidine spermine- N1 -acetyltransferase homolog, which can slow ABA-mediated stomatal closure. Evidence from genetic, biochemical and physiological analyses has revealed that this protein does so by acetylating the metabolite 1,3-diaminopropane ( DAP), thereby turning on the latter's intrinsic activity. Acetylated DAP triggers plasma membrane electrical and ion transport properties in an opposite way to those by ABA. Thus in adapting to low soil-water availability, acetyl- DAP could refrain stomates from complete closure to sustain CO2 diffusion to photosynthetic tissues. [ABSTRACT FROM AUTHOR]

This study investigates the impact of potential large-scale irrigation on the West African monsoon using the Massachusetts Institute of Technology regional climate model (MRCM). A new irrigation module is implemented to assess the impact of location and scheduling of irrigation on rainfall distribution over West Africa. A control simulation (without irrigation) and eight sensitivity experiments (with irrigation) are performed and compared to discern the effects of irrigation location and scheduling. It is found that the irrigation effect on soil moisture could force significant changes in spatial distribution and magnitude of rainfall, depending on the latitudinal location of irrigation. In general, the large irrigation-induced surface cooling owing to anomalously wet soil tends to suppress moist convection and rainfall, which in turn induces local subsidence and low-level anticyclonic circulation. These local effects are dominated by a consistent reduction of local rainfall over the irrigated land, irrespective of its location. However, the remote response of rainfall distribution to irrigation exhibits a significant sensitivity to the latitudinal position of irrigation and the intraseasonal variation of supplied irrigation water. The low-level northeasterly airflow associated with an anticyclonic circulation centered over the irrigation area, induced at optimal location and timing, would enhance the extent of low-level convergence areas through interaction with the prevailing monsoon flow, leading to a significant increase in rainfall. As the location of the irrigation area is moved from the coast northward, the regional rainfall change exhibits a significant decrease first, then increases gradually to a maximum corresponding to irrigation centered around 20°N, before it declines again. [ABSTRACT FROM AUTHOR]

Abstract: The burrowing activity of earthworms leads to soil structural changes by compaction of surrounded soil matrix, which represents the so-called drilosphere. This is a distinct volume around the resulting macropore, which controls various soil processes. In the aim to detect the bulk density variation around earthworm burrows, two repacked soil columns from a silt loam with defined water content and bulk density were created, separately inoculated with the anecic earthworm species Lumbricus terrestris, stored under constant conditions for 7weeks and finally analyzed by means of X-ray computed tomography. A basic voxel approach was developed to conduct a gapless analysis of the drilosphere and surrounding soil matrix. The measured Hounsfield Units of basic voxels (pixel size of 0.25mm and slice thickness of 0.625mm) were converted into the corresponding dry bulk density (BD). The initial mean BD of an entire horizontal soil slice was 1.34Mgm−3 (core 1) and 1.38Mgm−3 (core 2). Due to burrowing L. terrestris compacted the inner boundary of the drilosphere (burrow wall) up to a BD of at least 1.75Mgm−3 which equates to more than 30% compared to the soil matrix. The BD decreased from the inner boundary of the drilosphere to its outer boundary, which is a transition zone to the surrounding soil matrix. However, the BD decrease was not concentrically uniform but revealed heterogeneous patterns of zones with different BD-classes. This locally heterogeneous BD distribution is an evidence of radial earthworm forces acting anisotropically. We conclude that BD heterogeneity in the drilosphere of L. terrestris might have notable implications for the understanding of lateral transfer of water and solutes in the soil profile. [Copyright &y& Elsevier]

This study presents the results of research on the deficiencies of water content in the Albeluvisols within central Wielkopolska during 2009-2011. The objective was to determine the soil water deficiencies in relation to the lower limit of plant available water (LLPAW) calculated at a matric potential of -31 kPa (LLPAW31), -49 kPa (LLPAW49), -59 kPa (LLPAW59) and -88 kPa (LLPAW88). The research results indicate that crop water deficiency and the depth of soil drying up were mainly determined by the rainfall. During periods of vegetation the strongest and deepest drying up was observed in 2011. In this year, in the Stagnic Albeluvisols at a depth of about 70 cm the soil matric potential of -59 kPa was observed, while in Gleyic Albeluvisols, a depth of 60 cm was also observed. The highest soil water deficiencies were observed from the third decade in May to the second decade in July. These deficiencies in 100 cm thickness were 7 mm, 19 mm, 25 mm and 40 mm, in relation to LLPAW88, LLPAW59, LLPAW49 and LLPAW31 respectively. Considering the 30 cm soil thickness, the water deficiencies were noted from the third decade in April to the second decade in July. In the analysed Albeluvisols, the calculated average soil matric potential depth equal to the field capacity was about 65-70 cm in 2011, whereas in 2009 and 2010 it was 50-55 cm. [ABSTRACT FROM AUTHOR]

Abstract: This article reviews the current knowledge on terrestrial enchytraeid diversity in Latin America and it outlines the research potential that this group offers. Enchytraeids occur worldwide in all soils with sufficient moisture, oxygen and nutrient supply, but knowledge on their diversity and functioning in the tropics is practically non-existent, except in Latin America. Here, taxonomic efforts and research projects have led to the knowledge of currently 62 terrestrial or semi-aquatic species. Abundance of enchytraeids could be determined at the species level, and differences in the ecological behaviour of species were detected concerning factors such as soil type and land use. Especially South America harbours a rich and idiosyncratic enchytraeid fauna, dominated by genera or species absent or rare in other regions of the world, which is interesting from the phylogenetic point of view. However, only a minute fraction of the actual diversity is known to-date. Seventeen species are possibly peregrines. Densities appear to be comparable to those in temperate regions, from below 10,000 to 270,000ind.m−2, suggesting that enchytraeids may be as important for soil processes as in temperate regions. Site-specific species richness makes enchytraeids good biological indicators. Enchytraeids provide a widely open field for research in Latin America ranging from taxonomy and faunistics over biogeography, phylogenetics, comparative morphology, and developmental biology, to fundamental and applied ecology. The widespread ignorance concerning enchytraeids among scientists and naturalists as well as the current taxonomic impediment should be overcome by sound taxonomical and ecological work, training courses, identification manuals and popularization. [Copyright &y& Elsevier]

The natural environment and livelihoods in the Lower Mekong Basin (LMB) are significantly affected by the annual hydrological cycle. Monitoring of soil moisture as a key variable in the hydrological cycle is of great interest in a number of Hydrological and agricultural applications. In this study we evaluated the quality and spatiotemporal variability of the soil moisture product retrieved from C-band scatterometers data across the LMB sub-catchments. The soil moisture retrieval algorithm showed reasonable performance in most areas of the LMB with the exception of a few sub-catchments in the eastern parts of Laos, where the land cover is characterized by dense vegetation. The best performance of the retrieval algorithm was obtained in agricultural regions. Comparison of the available in situ evaporation data in the LMB and the Basin Water Index (BWI), an indicator of the basin soil moisture condition, showed significant negative correlations up to R = -0.85. The inter-annual variation of the calculated BWI was also found corresponding to the reported extreme hydro-meteorological events in the Mekong region. The retrieved soil moisture data show high correlation (up to R = 0.92) with monthly anomalies of precipitation in non-irrigated regions. In general, the seasonal variability of soil moisture in the LMB was well captured by the retrieval method. The results of analysis also showed significant correlation between El Niño events and the monthly BWI anomaly measurements particularly for the month May with the maximum correlation of R = 0.88. [ABSTRACT FROM AUTHOR]