Moisture Regimes Research Articles

Comparative anatomical and morphological study of vegetative organs of Gymnospermium altaicum (Pall.) Spach from natural populations

Plants growing in arid environments developed structural adaptations to reduce water loss and dissipate excessive light energy. However, such adaptations as thick cuticle, sunken stomata, developed mechanical tissue, and trichomes, may have various functions and can also be found in plants growing in mesic environments. To better understand the role of xeromorphic adaptations, it is important to study plants of the same species from different habitats. The object of our study was Gymnospermium altaicum (Pall.), a small perennial plant having the status of a rare species for Kazakhstan. For anatomical and morphometric studies, plants were sampled from three populations with different moisture regimes. Populations 1 and 3 were growing in drier conditions, on south-east and north-east slopes, respectively, while population 2 was found on a north-facing slope receiving more rainfall. We demonstrate, for the first time, that anatomical features and morphometric parameters of G. altaicum are correlated to the humidity variations. The xeromorphic features of vegetative organs of plants from populations 1 and 3 were not observed in plants from population 2. The outcomes of this research will help us to better understand the adaptive potential of G. altaicum and develop effective conservation strategies for its wild populations.

Studies on effect of seed hydration value of various soybean varieties with respect to soil types and moisture regimes

Studies on effect of seed hydration value of various soybean varieties with respect to soil types and moisture regimes

Study on the heat and vapor transfer resistance of the basement’s outer walls and calculation of moisture regime: A case study of Uzbekistan

Study on the heat and vapor transfer resistance of the basement’s outer walls and calculation of moisture regime: A case study of Uzbekistan

Study of the temperature and moisture regime of building walls in various construction areas

The article is devoted to the problems of assessing the balance of moisture transfer when calculating protection against waterlogging of building envelopes. For the calculation, several localities have been selected in which the wall of a building with given climatic parameters and internal air parameters for a living space were modeled. In order to model protection against waterlogging, 3 cities were chosen: Smolensk, Izhevsk and Dudinka. A calculation to protect the building envelope from waterlogging has been carried out. The values of resistance to vapor permeation and heat transfer of each layer of a multilayer building envelope have been calculated. The complex of maximum humidification was assessed, on the basis of which the values of the temperature of the greatest humidification were determined. The values of the actual resistance to vapor permeation and the required resistance to vapor permeation were calculated relative to the plane. Three examples of possible moisture transfer balance were obtained. It was also determined that the construction of the building wall under study is permitted in Smolensk and Dudinka. The researched wall cannot be used in Izhevsk.

Water use efficiency, economic feasibility and suitable moisture regime for wheat (Triticum aestivum L.)

Water use efficiency, economic feasibility and suitable moisture regime for wheat (Triticum aestivum L.)

Анализ сезонной и разногодичной динамики горных ландшафтов Северного Кавказа

Introduction. The spatial structure of the landscapes of the North Caucasus has been fairly well studied to date, which cannot be said about the temporal structure. The climatic changes noted in the territory of the North Caucasus are undoubtedly reflected in the temporal structure of landscapes, which determines the relevance of this study, the purpose of which is to identify common features and characteristic features of the seasonal and year-to-year dynamics of the mountain landscapes of the North Caucasus. Materials and methods. To analyze the seasonal and year-to-year dynamics of the mountain landscapes of the North Caucasus, methodological approaches developed by L.N. Beruchashvili and V.V. Bratkov and tested by him for various territories. The analysis of the seasonal and yearly variability dynamics of the mountain landscapes of the North Caucasus was carried out on the example of mountain-hollow (Shatoy) and mountain-valley (Ahty) landscapes. In the Excel spreadsheet, the material was processed in three gradations: temperature regime, moisture regime and trends in the vertical structure. Processing was carried out using data (average temperature and precipitation) from the Shatoy and Ahty weather stations for the period from 1961 to 2020. On the basis of the results obtained, the seasonal and yearly variability dynamics of the mountain landscapes of the North Caucasus was derived in percentage terms. Results. The occurrence and correlation of groups of states over time periods, reflecting the conditions of heat and moisture supply, vary quite significantly, to which different groups of intralandscape vegetation react differently. However, in general, the temporal structure of the mountain-basin and mountain-valley landscapes of the North Caucasus is stable, and modern climate changes do not lead to the emergence of new states that are not typical for the analyzed landscapes. Discussion. The latest studies of the seasonal and temporal dynamics of the landscapes of the North Caucasus and its individual regions end in 2015. We continued this direction, because in our opinion, it is relevant and promising. Our study confirms the conclusions of the authors of previous years that, despite climatic changes, the temporal structure of mountain landscapes is stable. Conclusion. In the temporal structure of the mountain landscapes of the North Caucasus, the main share belongs to humid and semi-humid states in summer and nival in winter. The ratios of groups of states over time intervals within mountain landscapes change quite significantly. As a result, the conditions for the growth of different groups of vegetation change. So, with an increase in the proportion of cryothermal conditions, as it was in 1971-1975 conditions become less favorable for the growth of woody vegetation, but more favorable for the development of grassy vegetation of the steppe type. With an increase in summer humidity, which is manifested by an increase in the proportion of the corresponding states, and a simultaneous softening of winter conditions, during which the proportion of nival states increases and a decrease in cryothermal states, as was the case in 1996–2000, the temporal structure becomes similar to forest landscapes. Resume. An analysis of the temporal structure of the mountain landscapes of the North Caucasus showed that it is characterized by high stability. Despite the noted climatic changes, there are no prerequisites for changing the temporal and, as a result, the landscape structure of the mountain landscapes of the North Caucasus. Suggestions for practical application and direction for future research. The results of the study can be useful in agriculture to identify the relationship between certain conditions and crop yields and forecasting natural hazards (droughts, frosts, etc.).

Yield response and economic evaluation of drip-fertigated muskmelon cultivated under mulched conditions

A study was carried out to standardize the moisture regime (irrigation) and fertigation (N:P:K levels) for improved crop establishment, plant growth, yield and fruit quality of muskmelon under drip irrigation cum fertigation and mulching during 2017-18 and 2018-19. The treatments included three levels of drip irrigation viz. 100% of crop evapotranspiration (ETc), 80% of ETc and 60% of ETc , with and without silver black polythene plastic mulching in main plots and three levels of fertigation viz. 100% of recommended dose of fertilizer (RDF), 80% of RDF and 60% of RDF in subplots. Drip irrigation at 100% of ETc and fertigation at 100% of RDF with mulching helped to improve the vine length, number of primary branches, average fruit weight, diameter and yield when compared with conventional (control) as well as other treatments. These results were statistically at par with that obtained under drip irrigation at 80% of ETc and fertigation at 80% of RDF with mulching. The yield under drip fertigation varied from 168.8-202.8 q/ha, which is about 16.5% higher as compared to conventional treatment. Drip fertigation under mulched conditions resulted in 17.2% higher net returns as compared to conventional treatment. Thus, it may be concluded that drip fertigation at 80% of ETc and fertigation at 80% of RDF with plastic mulching is beneficial for improving productivity of muskmelon with about 80.9% and 20.0% saving of water and fertilizers as compared to conventional method in the present study region

Effect of Irrigation Scheduling and Different Sowing Dates on Water Productivity and Economics of Wheat (Triticum aestivum L.)

“Effect of moisture regime under different sowing dates of wheat crop (Triticum aestivum L.)” was investigated at Acharya Narendra Deva University of Agriculture & Technology, Ayodhya (U.P.) Agronomy Research Farm in rabi season 2021-22. Twelve main plot treatments included 15th November, 25th November, and 5th December sowing dates, while four sub plot treatments included irrigation at 0.6, 0.8, 1.0, and 1.2 IW/CPE ratios. Split plot design was used for three replications. Under 15th November sowing, all growth, yield, and characteristics rose dramatically. Irrigation at 1.0 IW/CPE ratio increased wheat shoot m-2, plant height (cm), dry matter accumulation (g m-2), yield characteristics, grain and straw yield (q ha-1) considerably. D113 (15 November planting with irrigation at 1.0 IW/CPE ratio) had the best net return and D1I2 (15 November sowing with irrigation at 0.8 IW/CPE proportion) the highest B:C ratio (2.54). Wheat yields were highest when sown on November 15. Under 15th November planting, water use efficiency was highest (9.85 kg ha-1mm-1). Irrigation with 1.0 IW/CPE ratio had the maximum water usage efficiency (9.34 kg ha-1 mm-1). The 15 November seeding with irrigation at 1.0 IW/CPE ratio yielded the highest net return (1,17,124.00), making wheat farming profitable. Maximum B:C ratio (2.54) with I1D2 therapy.

The impact of northern red oak (Quercus rubra; Fagaceae) on the forest phytodiversity in Ukraine

The impact of Quercus rubra on the plant diversity of native forests of Ukraine has been investigated. The plant communities of artificial plantations dominated by northern red oak have such general features as poor species composition, with projective coverage values of other species not exceeding 5%, and a simplified vertical structure of the tree layers. In natural forest plant communities with the participation of Q. rubra, there are no rare and typical nemoral dominant species, which results in disruption of consortial relations in ecosystems. Such changes are due to the biological and ecological peculiarities of this species, in particular, its dense crown, abundant biomass of leaves, which reduces lighting, and allelopathic properties; all those factors affect the physical and chemical characteristics of biotopes. Quercus rubra artificial plantations are more adaptive to changes of natural conditions and are able to withstand harsher winters and lack of precipitation. The ecological amplitude of this species is wide, and even with an increase in the average annual temperature by 3 °C most of the ecological indicators do not go beyond the optimum zone of the species, except for the soil moisture and thermal regime. The amplitudes of main indicators of ecological factors of temperate forests and Q. rubra artificial plantations overlap. The dominance of Q. rubra reduces the quality of ecosystem services of native forests. The high competitive advantages of Q. rubra are the reason for the impossibility of natural restoration of the typical broad-leaved or coniferous forests on those land plots where they were replaced by artificial plantations of northern red oak or its tree layers were formed as the results of the spontaneous distribution of this species. In the successions, the communities with the participation of northern red oak are potentially able to replace the native forest phytocoenoses.

How Have Hydrological Extremes Changed over the Past 20 Years?

Abstract Severe floods and droughts, including their back-to-back occurrences (weather whiplash), have been increasing in frequency and severity around the world. Improved understanding of systematic changes in hydrological extremes is essential for preparation and adaptation. In this study, we identified and quantified extreme wet and dry events globally by applying a clustering algorithm to terrestrial water storage (TWS) data from the Gravity Recovery and Climate Experiment (GRACE) and GRACE Follow-On (FO). The most intense events, ranked using an intensity metric, often reflect impacts of large-scale oceanic oscillations such as El Niño–Southern Oscillation and consequences of climate change. The severity of both wet and dry events, represented by standardized TWS anomalies, increased significantly in most cases, likely associated with intensification of wet and dry weather regimes in a warmer world, and consequently, exhibited strongest correlation with global temperature. In the Dry climate, the number of wet events decreased while the number of dry events increased significantly, suggesting a drying trend that may be attributed to climate variability and possible increases in irrigation and reliance on groundwater. In the Continental climate where temperature has risen faster than global average, dry events increased significantly. Characteristics of extreme events often showed strong correlations with global temperature, especially when averaged over all climates. These results suggest changes in hydrological extremes and underscore the importance of quantifying total water storage changes when studying hydrological extremes. Extending the GRACE/FO record, which spans 2002 to the present, is essential to continuously tracking changes in TWS and hydrological extremes.

Soil enzyme activities in heavily manured and waterlogged soil cultivated with ryegrass (Lolium multiflorum)

Extended waterlogging (WL) conditions can alter soil enzyme activities and their role in maintaining healthy soils. We assessed the effects of soil moisture regimes (field capacity [FC] and WL) and phosphorus (P) rates (0, 15, 30, 45 kg available P ha–1) on ( i) soil enzymes and microbial biomass carbon (MBC), microbial biomass nitrogen (MBN), and microbial biomass P (MBP); and ( ii) dissolved organic carbon (DOC) and total dissolved nitrogen (TDN). The treatments were tested in a 4-month greenhouse experiment using intact soil columns under annual ryegrass ( Lolium multiflorum). WL decreased the activity of β-glucosidase and acid phosphomonoesterase but increased N-acetyl-β-glucosaminidase in soils. These changes were associated with changes in MBC, DOC, MBN, and TDN, but not MBP. Anoxic conditions in WL soil promote the activity of anaerobes and contribute to the reduction of Fe oxyhydroxides and the release of DOC, TDN, and P in the soil solution. The activity of the extracellular enzymes decreased in WL with additions of slurry indicating adequate supply of C, N, and P. Our results also showed that both enzyme activities and microbial biomass were restricted in the upper soil layer with limited downward movement along the soil profile. We can conclude that since these enzymes control the hydrolysis of cellulose, phosphomonoester, and chitin, soil moisture influences the direction and magnitude of C, N, and P in manured and waterlogged soil cultivated with ryegrass.

The vegetation of Holocene coastal dunes of the Cape south coast, South Africa.

The vegetation of calcareous coastal dunes of Holocene age along the south coast of South Africa's Cape Floristic Region is poorly described. This vegetation comprises a mosaic of communities associated with two biomes, Fynbos and Subtropical Thicket. Previously, expert knowledge rather than quantitative floristic analysis has been used to identify and delimit vegetation units. In many areas, mapped units conflate vegetation on Holocene sand with that on unconsolidated sediments of late Pleistocene age, despite pronounced species turnover across this edaphic boundary. Despite dominance by Cape lineages and fynbos vegetation, dune vegetation in the eastern part of the region has been included in the Subtropical Thicket Biome rather than the Fynbos Biome. The high levels of local plant endemism associated with this dune vegetation and the small and fragmented configuration of these habitats, makes it an urgent conservation priority especially when placed in the context of rising sea levels, increasing development pressures and numerous other threats. Here we provide a quantitative analysis of 253 plots of the 620 km2 of Holocene dune vegetation of the study area using phytosociological and multivariate methods. We identified six fynbos and two thicket communities based on the occurrences of 500 species. Following a long tradition in Cape vegetation typology, we used the Strandveld (beach vegetation) concept as our first-order vegetation entity and identified six units based on the fynbos floras. These were, from east to west, Southeastern Strandveld, St Francis Strandveld, Goukamma Strandveld, Southwestern Strandveld and Grootbos Strandveld. Each unit was differentiated by a suite of differential species, most being Holocene dune endemics. The two thicket communities-Mesic and Xeric Dune Thicket-showed limited variation across the study area and were subsumed into the Strandveld units. We discussed our findings in terms of vegetation-sediment relationships, emphasizing the need for a greater geographical coverage of sediment ages to facilitate a better understanding of deposition history on vegetation composition. We also discussed the role of soil moisture and fire regime on structuring the relative abundance of fynbos and thicket across the Holocene dune landscape. Finally, we address the conservation implications of our study, arguing that all remaining Holocene dune habitat should be afforded the highest conservation priority in regional land-use planning processes.

Extreme precipitation promotes invasion in managed grasslands.

Climate change is increasing the frequency and intensity of extreme events like drought and flooding, which threaten to amplify other global change drivers such as species invasion. We investigate the effect of wet and dry extreme precipitation regimes on invasive species' abundances in northern tallgrass prairies. Because soil moisture is a key determinant of prairie composition, theory and evidence suggest drought conditions will hinder invasion, whereas wetter conditions will enhance invasion. To test this hypothesis, we explored the effect of precipitation on invasive plant species abundance from 2010 to 2019 in 25 managed prairies using observations from 267 transects comprising 6675 plots throughout western Minnesota, USA. We estimated how increases in the number of extremely wet or dry months in a year altered overall invasive species abundance and the abundance of the highly invasive grasses Poa pratensis and Bromus inermis. We found that a greater occurrence of abnormally wet months increased invasive species abundance but found mixed evidence that abnormally dry conditions hindered invasion. Further, more moderately wet and dry months reduced native grass abundance. Together, these results suggest that more frequent extremely wet months may intensify invasive dominance and that dry months may not counterbalance these trends. Given the considerable uncertainty still surrounding the interactive effects of climate change and invasion on native plant communities, this research represents an important step toward quantifying the complex influence of precipitation extremes on invasion dynamics in managed ecosystems of critical conservation concern.

Role of Soil Moisture and Temperature on Development of Fusarium Wilt in Cucumber

The research experiment was conducted during the June to August of 2018 under green-house condition at the Experimental farm, Department of Plant Pathology, Dr YS Parmar University of Horticulture and Forestry, Nauni Solan, Himachal Pradesh, India. Mass culture of the pathogenic fungus, Fusarium oxysporum prepared on the corn sand meal medium were inoculated into the sterilized soil (7 cm diameter) in controlled conditions. Sterilized distilled water was sprinkled onto the inoculated soil followed by covering them pots with polythene sheet for about one week for build-up of inoculum. Different moisture and temperature regimes were tested for disease development. Results obtained from the experiments revealed that maximum disease incidence was observed at a soil moisture level of 45% however, no disease was observed at 15% soil moisture regime. Disease development was observed at all the temperature regimes tested except at 15oC where no disease progression was observed even after 21 days of inoculation. Maximum disease incidence (%) was recorded at 25oC temperature. Thus, the present studies indicated that extreme temperature and moisture levels were not found to be favourable for the development of the Fusarium wilt disease in cucumber as disease was observed at optimum environmental conditions of the Fusarium wilt disease in cucumber as disease was observed at optimum environmental conditions.

Habitat fragmentation affects climate adaptation in a forest herb

Abstract Climate change and the resulting increased drought frequencies pose considerable threats to forest herb populations, particularly where additional environmental challenges jeopardize responses to selection. Specifically, habitat fragmentation may hamper climate adaptation by altering the distribution of adaptive genetic variation and may also induce evolutionary changes in mating systems. To assess how habitat fragmentation disrupts climate adaptation, we conducted a common garden experiment with Primula elatior offspring originating from 24 populations sampled along a latitudinal gradient with varying climate and landscape characteristics. We then quantified a range of vegetative, regulatory and reproductive traits under distinct soil moisture regimes to evaluate imprints of local adaptation and phenotypic plasticity. Additionally, we conducted a more extensive field campaign in 60 populations along the same latitudinal gradient to evaluate the potential evolutionary breakdown of reciprocal herkogamy. For large, connected populations, our results demonstrated an evolutionary shift from a strategy in southern populations that seems aligned with drought avoidance—where plants minimize their exposure to dry conditions and optimize photosynthesis—to a drought tolerance strategy in northern populations, where plants are adapted to function despite water scarcity. However, habitat fragmentation disrupted climate clines and the adaptive responses to drought stress in key traits related to growth, biomass allocation and water regulation. Additionally, our findings indicate the onset of evolutionary breakdown in reciprocal herkogamy and divergence in other key flower traits. The disruption of climate clines, drought responses and adaptations in mating systems contributed to a substantially diminished flowering investment across the distribution range, with the most pronounced effects observed in southern fragmented populations. Synthesis. We present novel empirical evidence of how habitat fragmentation disrupts climate adaptation and drought tolerance in a wide range of traits along the range of the forest herb Primula elatior. These findings emphasize the need to account for habitat fragmentation while designing effective conservation strategies in order to preserve and restore resilient meta‐populations of forest herbs amidst ongoing global changes.

Dehumidification efficiency in the conditions of climate change in the Novgorod region

Agricultural production is closely related to natural and climatic factors, of which meteorological factors are the most variable and active. The analysis of climatic precipitation and temperature norms according to the data of 4 meteorological stations of the Novgorod region for the period 1891-2020 showed their steady increase, except for the Novgorod meteorological station, where the annual precipitation rate by 2020 decreased against the background of temperature growth. Analysis of the results of meteorological observations over the past 60 years has shown that there is a steady trend in the Novgorod region to increase the degree of humidification: the hydrothermal coefficient has increased from 1.36 to 1.46. This happened due to the excess of the increase in precipitation over the increase in temperature, so agricultural production of crop production is impossible without reclamation measures. The aim of the research was to gain new knowledge in the formation of soil moisture regimes under the influence of drainage reclamation in the conditions of climate change. In the Non-Chernozem zone, two main methods of drainage are common - a network of open channels and closed drains. Studies on the formation of soil moisture regimes were carried out during 2019-2021 on experimental production sites of closed and open drainage on 8 variants of structures. The conducted studies of the efficiency of the drainage systems of closed and open drainage allowed us to conclude that closed drainage systems better provide the water-air regime of the soil compared to open drainage: the period of soil being in a waterlogged state is 2 times shorter (50 days on open drainage structures and 25 days on closed drainage structures).The most optimal water-air regime of the soil among the options with closed drainage was provided by drainage systems with filling the drainage trench with wood chips, on which the range of moisture changes in the root-inhabited soil layer during 3 years of observation was closest to optimal and amounted to 210-114 mm. Among the options for open drainage are systems of runoff hollows in combination with cultivation strips.

Synthesis of high-Andean peat cores reveals suite of Holocene climate conditions favorable for peat formation

Peat-core records have a long history of being used for paleoclimate reconstructions in northern high-latitude regions but are less common in the southern tropical zone. In this study, we present a synthesis of published peat-core reconstructions and basal ages from high-elevation (>3000 m a.s.l.) sites in the northern and central Andes of South America. We complement this database by providing a new multi-proxy peat-core-based paleoecological reconstruction from the Alta Murmurani peatland, Cordillera Vilcanota, Peru. This record, with a peat inception age of 8980 cal. yr BP, was analyzed for plant macrofossils and stable isotopes (carbon, oxygen). This review (1) assesses the timing of peat initiation and development across the tropical high-elevation region of South America (8°N to 27°S); (2) assesses the reliability of peat-core paleoclimate reconstructions by comparing the peat-core inferences across sites and against other independent archives (e.g., lake sediments, ice cores, speleothems); and (3) determines which hydroclimatic conditions are favorable for peat formation and expansion across the study area. Our results show that peat initiation occurred throughout the Holocene, progressing from the northern Andes to central Andes, with highest initiation frequencies clustered at ca. 10,700 cal. yr BP and 8300 cal. yr BP, respectively. Our synthesis reveals that peat cores can be used to assess regional paleoclimate trends in the central Andes using a multi-proxy approach combining micro- and macrofossils such as pollen, stable isotopes, as well as organic and inorganic elemental analyses. We also identify three optimal peat-forming time periods, all with optimally wet conditions occurring at transitional hydroclimate phases: (1) following deglaciation, with warming temperatures and increased moisture related to glacial runoff (ca. 11,000 cal. yr BP and ∼8000 cal. yr BP), (2) under moderate moisture regimes related to intensifying ENSO and warmer conditions (∼3500 cal. yr BP), and (3) under conditions related to increased precipitation at the beginning of a cold period (Little Ice Age). We show that either regional climate (e.g., changes in precipitation) or local conditions (e.g., changes in glacial runoff) can promote peat formation across the study region.

What Do Cross-Range Germination, Growth, and Interaction Studies Reveal about the Behaviour of an Expansive Plant Species?

Understanding the invasion potential of any plant species is crucial for early detection in habitat conservation, particularly when observing their expansion within their native region. As a test species, we utilised Allium ursinum L., a dominant clonal species in early spring forest floors. We compared the species’ germination capacity in native (Hungarian) and non-native (North American) soils, its seedling growth, and competing performances with two co-occurring dominant species, Melica uniflora Retz. and Carex pilosa Scop., in ten soil types and three soil compositions, respectively. Additionally, the competitive interactions of A. ursinum with Convallaria majalis L., a species already introduced in North America, were assessed under three moisture conditions. The results revealed that A. ursinum exhibited enhanced germination in non-native soils, while its shoot growth was most vigorous in control soil. When grown in soils with different co-dominant species, A. ursinum seedlings exhibited varying growth rates, significantly influenced by solar radiation intensity. A. ursinum shoots displayed superior growth in soil collected from C. pilosa stands compared to soil originating from its own stands. Notably, A. ursinum effectively competed against C. majalis in moderate soil moisture conditions. Furthermore, increasing sand content improved the competitive ability of A. ursinum against C. pilosa and M. uniflora. Based on our findings, A. ursinum possesses an invasion potential for particular North American habitats. However, the extent of its potential is dependent upon soil and climatic conditions. Under medium moisture regime, A. ursinum might outcompete the already established C. majalis from its habitats. Additionally, it can potentially displace native species with comparable ecological characteristics, such as C. pilosa and M. uniflora, especially in loose soils. Similar cross-range seed germination, growth, and paired competition experiments with potential competitor species are highly recommended as these can not only elucidate its native range expansion but also various growth scenarios for its agricultural cultivation.

Multi-year vertical and life cycle impacts of C-N management on soil moisture regimes

Understanding the long-term impact of C-N management practices on soil moisture content (SMC) is crucial for sustainable agriculture, particularly in mitigating seasonal droughts and storm rainfall constraints. A multi-year (2014–2018) field experiment was conducted, with high-frequency measurements and consideration of a full life cycle, as well as multiple vertical layers (0–100 cm, with intervals of 20 cm). Treatments were arranged in a split plot design with nitrogen (N) fertilizer input (N80% and N60%) as the whole-plot factor, and Carbon (C) treatments (Corg=organic fertilizer, Cstraw=straw mulching and full returning, Cinteg= Corg + Cstraw) were considered as the split-plot factor. The results demonstrated the Cinteg treatment resulted in the highest increase in the five-year averaged SMC (approximately 6.60% greater than Corg), followed by the Cstraw treatment. Additionally, the N60% treatment resulted in significantly higher SMC compared to the N80% treatment, with a range of 1.71–4.12% increase across the life cycle. Furthermore, the research revealed that the average SMC increased the most during the jointing-heading period and the least during the heading-maturity period across all treatments. The vertical results indicated a higher efficiency in water retention within the shallow layers (0–20 cm, 20–40 cm) compared to the deeper layers (80–100 cm) for all treatments. The study recommends adopting integrated C-N management practices, considering life cycle periods and vertical layers, to optimize soil moisture content. It offers valuable insights for optimizing soil moisture management strategies, alleviating seasonal droughts, enhancing water-use efficiency, and fostering sustainable agricultural practices.

Regimes of Soil Moisture–Wet-Bulb Temperature Coupling with Relevance to Moist Heat Stress

Abstract Human heat stress depends jointly on atmospheric temperature and humidity. Wetter soils reduce temperature but also raise humidity, making the collective impact on heat stress unclear. To better understand these interactions, we use ERA5 to examine the coupling between daily average soil moisture and wet-bulb temperature (Tw) and its seasonal and diurnal cycle at global scale. We identify a global soil moisture–Tw coupling pattern with both widespread negative and positive correlations in contrast to the well-established cooling effect of wet soil on dry-bulb temperature. Regions showing positive correlations closely resemble previously identified land–atmosphere coupling hotspots where soil moisture effectively controls surface energy partition. Soil moisture–Tw coupling varies seasonally closely tied to monsoon development, and the positive coupling is slightly stronger and more widespread during nighttime. Local-scale analysis demonstrates a nonlinear structure of soil moisture–Tw coupling with stronger coupling under relatively dry soils. Hot days with high Tw values show wetter-than-normal soil, anomalous high latent and low sensible heat flux from a cooler surface, and a shallower boundary layer. This supports the hypothesis that wetter soil increases Tw by concentrating surface moist enthalpy flux within a shallower boundary layer and reducing free-troposphere-air entrainment. We identify areas of particular interest for future studies on the physical mechanisms of soil moisture–heat stress coupling. Our findings suggest that increasing soil moisture might amplify heat stress over large portions of the world including several densely populated areas. These results also raise questions about the effectiveness of evaporative cooling strategies in ameliorating urban heat stress. Significance Statement The purpose of this study is to provide a global picture of the relationship between soil moisture anomalies and a heat stress metric that includes the joint effects of temperature and humidity. This is important because a better understanding of this relationship will help improve the prediction of extreme heat stress events and inform strategies for ameliorating heat stress. We find a widespread positive correlation between soil moisture and heat stress, in contrast to studies relying on temperature alone. This raises the possibility that, over much of the world, and in the most populous regions, strategies like irrigation or “greening” that can reduce temperature might be ineffective or even harmful in reducing heat stress with humidity incorporated.