Varying Soil Water Research Articles

Litter Chemistry Is a Main Driver of Inorganic Nitrogen in Disturbed Soils in the Arid Patagonian Monte

ABSTRACTChanges in plant cover and soil characteristics induced by grazing may affect litter quality and nitrogen (N) release under varying abiotic conditions. Our study was focused on the importance of litter chemistry as a main driver of inorganic N (ammonium‐N: NH4+‐N and nitrate‐N: NO3−‐N) release to soil. Both inorganic N forms are important components for N availability to plants and soil processes, and the long‐term conservation of soil‐N fertility. We analyzed the effect of secondary compounds and the C/N ratio in litter under varying soil water, and UV exposure on soil inorganic N (NH4+‐N and NO3−‐N) in Patagonian Monte degraded soils. We hypothesized that secondary compounds and C/N ratio in litter are main drivers of soil inorganic N under varying abiotic conditions. We conducted a microcosm experiment (13 months) using intact upper soil blocks from denuded soil areas. Surface soils were added with shrub (SL), and mixed grass and shrub (GSL) litter with high versus low secondary metabolites concentration and low vs. high C/N ratio, respectively. Microcosms were maintained under ambient and reduced UV exposure, and high and low soil water. We used microcosms without litter as controls. Monthly, we assessed NH4+‐N and NO3−‐N concentrations in upper and sub‐superficial soils. Litter chemistry interacting with abiotic factors did not significantly influence soil NH4+‐N at any soil depth while litter chemistry was a main driver of NO3−‐N in upper soil. SL enhanced NO3−‐N in upper soil compared with GSL independently of abiotic factors. In upper soils without litter and in those with GSL, the highest NO3−‐N concentration occurred mostly under high soil water and exposition to UV. We concluded that litter chemistry was a main driver of soil N fertility in disturbed rangelands. Shrub litter may enhance N fertility (NO3−‐N) in degraded soils.

Drought-responsive dynamics of H3K9ac-marked 3D chromatin interactions are integrated by OsbZIP23-associated super-enhancer-like promoter regions in rice

BackgroundIn response to drought stress (DS), plants undergo complex processes that entail significant transcriptome reprogramming. However, the intricate relationship between the dynamic alterations in the three-dimensional (3D) genome and the modulation of gene co-expression in drought responses remains a relatively unexplored area.ResultsIn this study, we reconstruct high-resolution 3D genome maps based on genomic regions marked by H3K9ac, an active histone modification that dynamically responds to soil water variations in rice. We discover a genome-wide disconnection of 3D genome contact upon DS with over 10,000 chromatin loops lost, which are partially recovered in the subsequent re-watering. Loops integrating promoter–promoter interactions (PPI) contribute to gene expression in addition to basal H3K9ac modifications. Moreover, H3K9ac-marked promoter regions with high affinities in mediating PPIs, termed as super-promoter regions (SPRs), integrate spatially clustered PPIs in a super-enhancer-like manner. Interestingly, the knockout mutation of OsbZIP23, a well-defined DS-responsive transcription factor, leads to the disassociation of over 80% DS-specific PPIs and decreased expression of the corresponding genes under DS. As a case study, we show how OsbZIP23 integrates the PPI cluster formation and the co-expression of four dehydrin genes, RAB16A–D, through targeting the RAB16C SPR in a stress signaling-dependent manner.ConclusionsOur high-resolution 3D genome maps unveil the principles and details of dynamic genome folding in response to water supply variations and illustrate OsbZIP23 as an indispensable integrator of the yet unique 3D genome organization that is essential for gene co-expression under DS in rice.

Generation and evaluation of energy and water fluxes from the HOLAPS framework: Comparison with satellite-based products during extreme hot weather

Improving our understanding of the energy and water exchanges between the land surface and the lower atmosphere (i.e. land–atmosphere interactions), and how climate change may affect them, is crucial to predict changes in temperature and precipitation extremes. Observations of energy and water fluxes at the land surface are typically retrieved from the eddy covariance method, which presents limitations related to spatial and temporal gaps, and the non-closure of the energy and water balances. Meanwhile, soil moisture (SM) products derived from satellite data have been widely used at regional and global scales, but they are limited to capture only surface soil water content and variations. The combination of remote sensing (RS) data and modelling frameworks is called to be the solution to improve the spatial coverage and vertical resolution of land–atmosphere interactions data, ensuring the energy and water balance closure. Here, we explore the combination of remote sensing and meteorological data with a physical-based modelling framework, the High resOlution Land Atmosphere Parameters from Space (HOLAPS). We used HOLAPS to produce hourly consistent estimates of energy and water fluxes over Europe at 5 km resolution. HOLAPS and other satellite-based evapotranspiration and sensible heat flux products from the literature are evaluated against the water balance method and eddy covariance measurements. HOLAPS SM estimates together with other RS-modelling products are also evaluated against ground-based measurements at the surface and in the root zone. The evaluation of HOLAPS ET estimates show similar performance to the other products with Kling–Gupta efficiency (KGE) ¿ -0.41 in comparison with eddy covariance measurements from FLUXNET in all seasons but in boreal winter. The simulation of H is more uncertain than for ET with KGE values ranging from -2.5 to 0.8 along the products and stations at monthly scales. HOLAPS reaches slightly better results than the rest of ET and H products at daily scales in summer (KGE ¿ 0.3 for ET and KGE ¿ 0.0 for H) and during hot conditions (KGE ¿ 0.2 for ET and KGE ¿-0.2 for H), while the state-of-the-art products show KGE ¿ 0.1 for ET and KGE ¿ -0.41 for H in summer and KGE ¿ -0.1 for ET and KGE ¿ -0.6 for H during hot conditions. All products evaluated here yield a reasonable performance (KGE ¿-0.41 at most sites) in simulating SM at the surface and in the root zone. Our results expose the need for further investigating and improving product performances during extreme conditions. The good performance of HOLAPS together with its inherent advantages (RS data driven, high temporal and spatial resolution, spatial and temporal continuity, soil moisture at different depths and long-term consistent evapotranspiration and sensible heat flux estimates) support its use for agricultural and forest management activities as well as to study land–atmosphere interactions based on Earth Observations.

Aging of biodegradable microplastics and their effect on soil properties: Control from soil water

The ecological risks of biodegradable microplastics (BMPs) to soil ecosystems have received increasing attention. This study investigates the impacts of polylactic acid microplastics (PLA-MPs) and polybutylene adipate terephthalate microplastics (PBAT-MPs) on soil properties of black soil (BS) and fluvo-aquic soil (FS) under three water conditions including dry (Dry), flooded (FL), and alternate wetting and drying (AWD). The results show that BMPs exhibited more evident aging under Dry and AWD conditions compared to FL condition. However, BMPs aging under FL condition induced more substantial changes in soil properties, especially dissolved organic carbon (DOC) concentrations, than under Dry and AWD conditions. BMPs also increased the humification degree of soil dissolved organic matter (DOM), particularly in BS. Metagenomic analysis of PBAT-MPs treatments showed different changes in microbial community structure depending on soil moisture. Under Dry conditions, PBAT-MPs enhance the ammonium-producing process of soil microbial communities. Genes related to N nitrification and benzene degradation were enriched under AWD conditions. In contrast, PBAT-MPs do not change the abundance of genes related to the N cycle under FL conditions but significantly reduce genes related to benzene degradation. This reduction in benzene degradation genes under FL condition might potentially slow down the degradation of PBAT-MPs, and could lead to temporary accumulation of benzene-related intermediates. These findings highlight the complex interactions between BMPs, soil properties, and microbial communities, emphasizing the need for comprehensive evaluations of BMPs’ environmental impacts under varying soil water conditions.

Variability of soil water and effect of soil reconstruction in Xilin Hot steppe mining area

Variability of soil water and effect of soil reconstruction in Xilin Hot steppe mining area

Seasonal and vertical patterns of water availability and variability determine plant reproductive phenology.

Changing precipitation regimes can influence terrestrial plants and ecosystems. However, plant phenological responses to changing precipitation temporal patterns and the underlying mechanisms are largely unclear. This study was conducted to explore the effects of seasonal precipitation redistribution on plant reproductive phenology in a temperate steppe. A field experiment with control (C), advanced (AP) and delayed (DP) growing-season precipitation peaks, and the combination of AP and DP (ADP) were employed. Seven dominant plant species were selected and divided into two functional groups (early- vs. middle-flowering species, shallow- vs. deep-rooted species) to monitor reproductive phenology including budding, flowering, and fruiting date, as well as reproductive duration for four growing seasons from 2015 to 2017, and 2022. The AP, but not DP treatment advanced the phenological (i.e., budding, flowering, and fruiting) dates and lengthened the reproductive duration across the 4 growing seasons and 7 monitored species. In addition, the phenological responses showed divergent patterns among different plant functional groups, which could be attributed to shifts in soil moisture and its variability in different months and soil depths. Moreover, species with lengthened reproductive duration increased phenological overlap with other species, which could have a negative impact on their dominance under the AP treatment. Our findings reveal that changing precipitation seasonality could have considerable impacts on plant phenology by affecting soil water availability and variability. Incorporating these two factors simultaneously in the phenology models will help us understand the response of plant phenology under intensified changing precipitation scenarios. In addition, the observations of decreased dominance for the species with lengthened reproductive duration suggest that changing reproductive phenology can have a potential to affect community composition in grasslands under global change.

Integrated Effects of Soil Moisture on Wheat Hydraulic Properties and Stomatal Regulation.

The development of water-saving management relies on understanding the physiological response of crops to soil drought. The coordinated regulation of hydraulics and stomatal conductance in plant water relations has steadily received attention. However, research focusing on grain crops, such as winter wheat, remains limited. In this study, three soil water supply treatments, including high (H), moderate (M), and low (L) soil water contents, were conducted with potted winter wheat. Leaf water potential (Ψleaf), leaf hydraulic conductance (Kleaf), and stomatal conductance (gs), as well as leaf biochemical parameters and stomatal traits were measured. Results showed that, compared to H, predawn leaf water potential (ΨPD) significantly reduced by 48.10% and 47.91%, midday leaf water potential (ΨMD) reduced by 40.71% and 43.20%, Kleaf reduced by 64.80% and 65.61%, and gs reduced by 21.20% and 43.41%, respectively, under M and L conditions. Although gs showed a significant difference between M and L, Ψleaf and Kleaf did not show significant differences between these treatments. The maximum carboxylation rate (Vcmax) and maximum electron transfer rate (Jmax) under L significantly decreased by 23.11% and 28.10%, stomatal density (SD) and stomatal pore area index (SPI) under L on the abaxial side increased by 59.80% and 52.30%, respectively, compared to H. The leaf water potential at 50% hydraulic conduction loss (P50) under L was not significantly reduced. The gs was positively correlated with ΨMD and Kleaf, but it was negatively correlated with abscisic acid (ABA) and SD. A threshold relationship between gs and Kleaf was observed, with rapid and linear reduction in gs occurring only when Kleaf fell below 8.70 mmol m-2 s-1 MPa-1. Our findings demonstrate that wheat leaves adapt stomatal regulation strategies from anisohydric to isohydric in response to reduced soil water content. These results enrich the theory of trade-offs between the carbon assimilation and hydraulic safety in crops and also provide a theoretical basis for water management practices based on stomatal regulation strategies under varying soil water conditions.

Impact of moisture on the degradation and priming effects of poly(lactic acid) microplastic

AbstractThe degradation of biodegradable microplastics (MPs) can either stimulate or inhibit the decomposition of soil organic carbon (SOC), but the factors influencing these phenomena remain unclear. In this study, we used the 13C natural abundance to differentiate between carbon dioxide (CO2) arising from the mineralization of SOC and poly(lactic acid) (PLA) MP under varying soil water holding capacity (WHC) in alkaline and acidic soils. We also quantified the incorporation of soil‐ or PLA‐derived carbon (C) into phospholipid fatty acid (PLFA)‐distinguishable microbial groups. An increase in soil moisture did not significantly affect PLA MP degradation in alkaline soil, but significantly increased PLA degradability in acidic soil. In particular, the percentages of PLA‐derived C incorporated into PLFA‐distinguishable gram‐negative and gram‐positive bacteria were 14%–63% and 5%–33%, respectively, in all the treatments. The presence of PLA MP induced positive priming effects from 0 to 20 d in all the treatments but subsequently induced negative priming effects under some conditions. The total priming effects induced by PLA MP were significantly greater in alkaline soil with ≥70% WHC (37–43 mg C kg−1 soil) than in this soil with 50% WHC (8.6 mg C kg−1 soil). The total priming effect was 72–78 mg C kg−1 soil in acidic soil with ≤70% WHC, but a negative priming effect was observed in this soil with 90% WHC (−56 mg C kg−1 soil). In alkaline soil, the dissolved organic carbon content was positively correlated with the priming effect, but a negative relationship was observed between the priming effect and the amount of soil‐derived C incorporated into gram‐negative bacteria and fungi. In acidic soil, a positive correlation was found between the priming effect and the soil nitrate content. In summary, our findings indicate that 0.4%–2.8% of PLA MP was degraded in soils after 2 months, and that the intensity and direction of the priming effect induced by PLA MP are regulated by soil moisture and pH, but further exploration is needed to elucidate the microbial mechanisms underlying these effects.

Arbuscular mycorrhizal fungi increased biomass, nutritional value, and cochineal resistance of Opuntia ficus-indica plants

BackgroundOpuntia ficus-indica (L.) Miller is dominantly growing on degraded soils in arid and semi-arid areas. The plants might establish a strong association with arbuscular mycorrhizal fungi (AMF) to adapt to nutrient, drought, and herbivore insect stress. The objective of this study was to investigate the effects of AMF inoculations and variable soil water levels (SWA) on the biomass, nutrient concentration, nutritional composition, and nutrient digestibility of the spiny and spineless O. ficus-indica by inducing resistance to cochineal stress. One mother Opuntia ficus-indica cladode was planted in a single pot in each field with 24 kg mixed soil. AMF inoculums were cultured in sorghum plants in a greenhouse and were inoculated in the planted cladodes. The planted cladodes were arranged using a completely randomized design (CRD) with three factors: AMF (present and absent); O. ficus-indica type (spiny and spineless) and four water treatments with 0–25% of plant available soil water (SWA), 25–50% of SWA, 50–75% of SWA, and 75–100% of SWA.ResultsDrought stress reduced the below and above-ground biomass, cladode nutrient content, nutritional composition, and in vitro dry matter digestibility (IVDMD) and in vitro organic matter digestibility (IVOMD). AMF colonization significantly increased biomass production with significant changes in the macro and micro-nutrient concentrations of O. ficus-indica. AMF inoculation significantly increased the IVDMD and IVOMD of both O. ficus-indica types by improving the biomass, organic matter (OM), crude protein (CP), and reduced fiber and ash contents. AMF-inoculated cladodes improved the nutrient concentrations of the cladodes. AMF caused an increase in biomass production, increased tolerance to cochineal stress, and improved nutrient concentration, nutritional composition, and nutrient digestibility performance of O. ficus-indica plants.ConclusionsAMF improved the performance of the O. ficus-indica plant to resist drought and cochineal stress and increased the biomass, nutrient concentration, nutritional composition, and nutrient digestibility. The potential of O. ficus-indica to adapt to cochineal stress is controlled by the macro and micro-nutrient concentration brought by the AMF association.

Soil basal respiration and nitrogen mineralization from C3 and C4 grass dominated plant communities respond differently to temperature and soil water variation

Key environmental influences on soil basal respiration (Rs) and nitrogen mineralization (ΔIN) are temperature and soil water content (SWC) and both are being altered by climate change. Yet we cannot expect that variation in temperature and SWC will equally affect all ecosystems. We examine the influences of temperature and SWC on Rs and ΔIN in two grassland plant communities dominated by C3 or C4 species. We collected soil samples from these communities and incubated them at temperatures (5 °C, 10 °C, 15 °C, and 25 °C) and four SWC (10%, 20%, 30% and 40% by weight). After four one-month incubation experiments, we found that (1) plant communities, temperature, and SWC significantly influenced Rs and ΔIN; (2) the highest Rs and ΔIN occurred at 25 °C and 30% SWC in the C4 plant community; (3) in the driest soils, N was immobilized in both communities regardless of temperature. We suggest that there is a greater limitation to C and N mineralization in the C3 plant community than in the C4 plant community making the C3 community less sensitive to variation in temperature and SWC.

Preserving isohydricity: vertical environmental variability explains Amazon forest water use strategies.

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, 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 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. By 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.

Overview of the Impact of Compost on Bulk Density, Aggregate Consistency and Cation Exchange Capacity of Soils and its Consequential Effect on Crop Productivity

Organic fertilizers offer several advantages over chemical fertilizers and are an environmentally friendly alternative that could help sustainably farmed land. Reviewing indigenous knowledge of the agronomic applications of organic manure and its possible contribution to agricultural growth was the goal of this article. It is evident that organic manures from various plant and animal sources can be used to satisfy certain field needs. However, the use of organic manures is still primarily conventional since they have not been well received by agricultural strategies. When bulky organic manures are directly applied to soil, they accelerate mineralization and reduce the rate at which nutrients, especially nitrogen, are released. Compared to raw resources, which have limited value and certain disadvantages, composting these wastes appears to offer significant potential. The majority of researchers verified that adding compost might enhance the soil's organic matter content, nutrient status, and physical, chemical, and biological properties. Soil organic matter concentrations rise in every long-term compost treatment study. But since they contain more stable carbon than fresh or immature composts, mature composts raise Soil organic matter considerably more effectively. Furthermore, because compost has so many beneficial effects on the physical, chemical, and biological aspects of soil, it helps to stabilize and improve crop quality and yield. As a result, the majority of studies have demonstrated that compost has an equalizing influence on seasonal and annual variations in soil temperature, air, water, and plant nutrient availability, as well as crop yields. mostly due to the nutrients' gradual release and availability in compost-combined fertilization techniques, which frequently yield positive outcomes. Therefore, composting can be a useful choice for building effective plant-nutrient management methods in many settings for sustainable agricultural systems within small-scale farming in impoverished nations.

Distribution and Variation of Soil Water and Salt before and after Autumn Irrigation

Autumn irrigation is a key measure for alleviating soil salinity and promoting sustainable agricultural development in the Hetao Irrigation district; however, only a part of farmland is irrigated in autumn during the non-growth period of crops, which leads to the redistribution of soil water and salt between autumn-irrigated land (AIL) and adjacent non-autumn-irrigated land (NAIL) after autumn irrigation. To explore the distribution and variation of soil water and salt in different positions of AIL and NAIL after local autumn irrigation and reveal the interaction range between AIL and NAIL, field experiments were carried out for two years in typical test areas. The results showed that compared with non-autumn irrigation, autumn irrigation improved the distribution uniformity of soil water and salt profiles in both horizontal and vertical directions; after autumn irrigation, the water content of the soil at the nearest sampling point to the boundary in the AIL increased the least, but the desalination rate was the greatest, while the water and salt contents of the soil within 45 m from the sampling points to the boundary in the NAIL both increased significantly. NAIL received the drainage of AIL and made the groundwater level after the rise in AIL fell quickly back, but unreasonable autumn irrigation caused the groundwater level of AIL to remain at a high level before freezing, exacerbating the risk of groundwater carrying salts to the surface soil during the freezing and thawing period, detrimental to the growth of crops in the next spring. The research results are of great significance to the rational use of farmland water resources and the improvement of soil salinization in cold and dry areas.

Topographic regulations on ecohydrological dynamics in a montane forest catchment and the implications for plant adaptation to environment

Rugged and covered by vegetation, most of the Earth’s terrestrial surfaces constantly interact with ecohydrological processes and influence ecosystem functioning and stability. To understand how water and vegetation interact in adaptation to environmental change under topographic regulations, we conducted an experiment in a montane catchment in South Australia during 2012–2014. We presented the dynamics of microclimate, soil moisture and transpiration (Ec) in two plots on the north- and south-facing slopes (NFS and SFS), and discussed how plants may adapt to environment with varied water and energy availabilities. It was found that (1) the maximum Ec occurred in spring when both energy and water supplies were optimal for tree growth, whilst the minimum appeared in autumn mainly related to soil water deficit; (2) the largest differences in Ec from two eucalyptus species were in winter (NFS > SFS) and summer (SFS > NFS) related to seasonal variations of radiation and soil water modulated by terrain aspect; (3) faster and greater soil water depletion on NFS than SFS in dry seasons was most likely resulted from evapotranspiration; and (4) total plot transpiration was similar on the opposite slopes despite the topography-induced seasonal differences. The species on SFS were less vulnerable than those on NFS in dry environments reflected by relatively higher transpiration. Our results may indicate that antecedent soil water storage and the following dry-season replenishment are particularly important for tree survival especially those on the equator-facing slopes. The comparisons have sound implications for understanding the ecohydrological dynamics and hillslope forest management in semi-arid areas.

Transition from opportunistic to conservative water use strategy with the growth of Robinia pseudoacacia in a typical watershed in the semiarid Loess Plateau

Understanding water use strategy is essential to evaluate plant adaptability in water-limited regions, but whether this strategy changes with plant growth needs further investigation. Robinia pseudoacacia is an exotic pioneer plantation species widely planted in the semiarid Loess Plateau of China to restore degraded ecosystems. Plant water uptake proportion from different soil layers and the water uptake pattern calculated through soil water uptake niche breadth (B index) were determined for R. pseudoacacia in 11-, 25-, 33–, and 43-yr plantations. Leaf physiological parameters and carbon stable isotopic composition (δ13C) were measured concurrently to calculate short-term and long-time integrated water use efficiency (WUE). Then, the water use strategy for R. pseudoacacia at different plantation ages was assessed through water uptake patterns, stomatal conductance (gs), and WUE variation under varied soil water conditions. Results showed that R. pseudoacacia maintained high gs and low short-term WUE and δ13C through a relative equal water uptake pattern and absorbed water within 0 − 400 cm soil depths in 11- and 25-yr plantations. However, this species exhibited an exclusive water uptake pattern and absorbed water mainly from 50 − 400 cm soil depth, adopted low gs and high short-term WUE and δ13C in 33– and 43-yr plantations. Therefore, R. pseudoacacia transited from an opportunistic to a conservative water use strategy with plant growth. The short-term WUE and δ13C were mainly and significantly influenced by gs and specific leaf area, respectively. Furthermore, the significant influence of B index on gs, δ18OΔ, short-term WUE, and δ13C indicated that R. pseudoacacia coordinated both water uptake pattern and water use behavior to contend with varied soil water conditions. This study suggested that changes in age-related water use strategy were essential for the adaptability of R. pseudoacacia in water-limited conditions.

The influence mechanism of soil pore structure on spatial variability of soil water and nutrients in the mining-induced subsidence area of China northwest

The influence mechanism of soil pore structure on spatial variability of soil water and nutrients in the mining-induced subsidence area of China northwest

Within-field extrapolation away from a soil moisture probe using freely available satellite imagery and weather data

Recognition of the importance of soil moisture information to the optimisation of water-limited dryland cereal production has led to Australian growers being encouraged to make use of soil moisture sensors. However, irrespective of the merits of different sensing technologies, only a small soil volume is sensed, raising questions as to the utility of such sensors in broadacre cropping, especially given spatial variability in soil water holding capacity. Here, using data collected from contrasting sites in South Australia and Western Australia over two seasons, during which either wheat or barley were grown, we describe a method for extrapolating soil moisture information away from the location of a probe using freely-available NDVI time series and weather data as covariates. Relationships between soil moisture probe data, cumulative NDVI (ΣNDVI), cumulative net precipitation (ΣNP) and seasonal growing degree days (GDD) were significant (P < 0.0001). In turn, these could be used to predict soil moisture status for any location within a field on any date following crop emergence. However, differences in ΣNDVI between different within-field zones did not fully explain differences in the soil moisture from multiple sensors located in these zones, resulting in different calibrations being required for each sensor or zone and a relatively low accuracy of prediction of measured soil moisture (R2adj ~ 0.4–0.7) which may not be sufficient to support targeted agronomic decision-making. The results also suggest that at any location within a field, the range of variation in soil moisture status down the soil profile on any given date will present as greater than the spatial variation in soil moisture across the field on that date. Accordingly, we conclude that, in dryland cereal cropping, the major value in soil moisture sensors arises from an enhanced ability to compare seasons and to relate similarities and differences between seasons as a guide to decision-making.

Root water uptake patterns are controlled by tree species interactions and soil water variability

Abstract. Root water uptake depends on soil moisture which is primarily fed by throughfall in forests. Several biotic and abiotic elements shape the spatial distribution of throughfall. It is well documented that throughfall patterns result in reoccurring higher and lower water inputs at certain locations. However, how the spatial distribution of throughfall affects root water uptake patterns remains unresolved. Therefore, we investigate root water uptake patterns by considering spatial patterns of throughfall and soil water in addition to soil and neighboring tree characteristics. In a beech-dominated mixed deciduous forest in a temperate climate, we conducted intensive throughfall sampling at locations paired with soil moisture sensors during the 2019 growing season. We employed a linear mixed-effects model to understand controlling factors in root water uptake patterns. Our results show that soil water patterns and interactions among neighboring trees are the most significant factors regulating root water uptake patterns. Temporally stable throughfall patterns did not influence root water uptake patterns. Similarly, soil properties were unimportant for spatial patterns of root water uptake. We found that wetter locations (rarely associated with throughfall hotspots) promoted greater root water uptake. Root water uptake in monitored soil layers also increased with neighborhood species richness. Ultimately our findings suggest that complementarity mechanisms within the forest stand, in addition to soil water variability and availability, govern root water uptake patterns.

Spatial variability and forecast of soil water in the ultra‐deep loess profile across a south–north transect of the Chinese Loess Plateau

AbstractKnowledge of the spatial variability and forecast of soil water in the ultra‐deep (&gt;21 m) loess profile are important for understanding the chemical, physical, and biological processes in the CZ. In this study, we regularly monitor soil water content (SWC) in deep soil profile along regional transect on the Loess Plateau. Descriptive statistical analysis found that the coefficient of variation (CV) of mean SWC in Ansai and Shenmu were 16.036% and 13.606%, respectively, indicating moderate variability. The CV of mean SWC in Yangling, Changwu, and Fuxian were 4.111%, 7.951%, and 6.117%, respectively, showing low variability. Geo‐statistical analysis indicated that mean SWC showed strong spatial dependence. Wavelet analysis showed that the approximative trend of mean SWC in five sampling sites showed an increased trend along depth series. In addition, a good fit line equation (R2 = 0.329) was established by using observed values and ANN‐forecast of three sites (Yangling, Fuxian, and Shenmu). And the RMSE values of five sample sites, respectively, were 1.302, 4.546, 2.662, 6.231, and 4.293. This study fills the gap in research' ultra‐deep (&gt;21 m) soil water changes and forecast, evidence from soil borehole data. At the same time, our research provides valuable information for the vegetation restoration and modelling of deep soil water.

Water uptake by plants under nonuniform soil moisture conditions: A comprehensive numerical and experimental analysis

The spatiotemporal pattern of root water uptake (RWU) depends on multiple factors, such as plant root biomass, soil water availability, and prevailing weather conditions at the site. The water uptake reduction due to the nonuniformity in soil water contents is often mitigated through compensated root water uptake (CRWU) and hydraulic redistribution (HR). Although previous studies have often considered these two processes independently due to the simplicity and feasibility of analyzing them separately, CRWU and HR can coexist in field conditions. Therefore, this work demonstrates the importance of considering CRWU and HR simultaneously in estimating daily transpiration and RWU distribution for nonuniform soil moisture conditions. For that, we have implemented the mechanistic RWU models developed by de Jong van Lier et al. (denoted below as the DJ model), Couvreur (CR), and Nimah and Hanks (NH) (see the references in the main text) into the widely-used HYDRUS-1D model, in addition to the previously available Jarvis (JF) and Feddes (FD) models. The performance of these models was then compared for varying soil water contents and boundary conditions using experimental data and hypothetical modeling scenarios. Our analysis has shown that these models are beneficial in estimating RWU with varying degrees of accuracy. The DJ and CR models are effective in simultaneously simulating CRWU and HR. NH and JF models can simulate CRWU but cannot simulate HR satisfactorily. Implementing these models into the HYDRUS platform for simultaneously considering CRWU and HR will significantly improve the accuracy of RWU predictions.