Shallow Soil Research Articles

Interpretation of suspended sediment concentration‐runoff hysteresis loops in two small karst watersheds

AbstractQuantifying suspended sediment concentration‐runoff (SSC‐Q) hysteresis can help to understand the source and transport mechanism of sediment. Due to the unique lithology, shallow soil, high infiltration capacity, complex geomorphology and heterogeneous landscape of karst watersheds in southwestern China, SSC‐Q hysteresis patterns remain unclear in this region. In the present study, the hysteresis index (HI) was used to quantify the SSC‐Q hysteresis pattern. The effects of rainfall and runoff on the HI were also evaluated from 2014 to 2019 in the Mahuangtian (2.26 km2) and Muzhaihe (0.09 km2) karst watersheds. The results showed that the clockwise loops accounted for more than 60% of the total hysteresis patterns in the two karst watersheds. In contrast, the counter‐clockwise and figure‐eight loops occupied no more than 30% and 10% of the total hysteresis patterns, respectively. These differences in the hysteresis patterns probably resulted from the spatial distribution of sediment sources and hydrological connectivity. The HI was significantly affected by the maximum discharge in the Mahuangtian watershed (P < 0.05) and by the flashiness index in the Muzhaihe watershed. This may be attributed to their different 3D hydrogeological structure, lithology and watershed size. This study can facilitate a better understanding of suspended sediment dynamics and provide important guidance for accurately implementing soil and water conservation strategies in karst areas.

Investigation of Lunar Shallow Subsurface Water Content and Soil Elemental Composition via Active Neutron Detection

The detection of planetary water and soil elements is a pivotal area of research due to its implications for understanding celestial bodies. Within the realm of planetary sampling missions, attention is predominantly directed toward the shallow surface layers, typically to a depth of 1 m. This paper examines the Moon as a case study, employing Monte Carlo simulations to introduce an active detection methodology that integrates high-energy neutron pulse generators with neutron and gamma detectors. Simulations were made of the albedo neutrons and prompt gamma counts after mitigating the interference of secondary neutrons and gamma rays, which result from the interaction between galactic cosmic rays and the lunar surface. The depth limit of active neutron detection on the shallow surface is about 100 cm. The cadmium ratio (CdR), the ratio between total neutron counts and counts caused by nonthermal neutrons, facilitates the rapid and accurate water content calculation using a fitted CdR curve. Standard gamma spectra of the associated elements, derived through Monte Carlo simulations, along with the mixed gamma spectra requiring resolution, form the foundation for the spectral analysis. Utilizing the weighted least-squares method to invert gamma spectra facilitates the identification of the content of associated elements. Integrating the analysis of albedo neutron energy spectra with prompt gamma spectra allows for the rapid assessment of the region’s water content and soil conditions. Moreover, this study also explores the impact of variations in the content of associated elements on the determination of water content.

Study on seismic response of liquefiable soil-pile group considering pile cap and soil contact

In this paper, based on the centrifuge test of liquefied soil-pile foundation system, a numerical model of liquefied soil-pile foundation-structure system is modelled by using OpenSees platform. In the simulation model, the friction effect between liquefied ground and low pile cap is considered, and the method of establishing virtual nodes is used to deal with the non-linear contact between liquefiable soil and low pile cap. The rationality and effectiveness of the numerical simulation method adopted in this paper has been verified and evaluated by comparing with the results of centrifuge experiments. A typical liquefaction soil-pile integrated finite element model is modelled using validated numerical simulation methods. The law of seismic response of the pile foundation system with different embedding depths of pile cap, different contact modes between the pile cap and saturated sand, and the thickness of the overlying saturated loose sand layer are discussed. The results show that the pile cap and pile foundation in the high pile cap system show higher seismic response characteristics than the other three low pile cap system conditions; Under the condition of different contact modes between the pile cap and the surrounding saturated sand, the peak bending moment and residual displacement of the pile foundation calculated by the bond contact are larger than calculated by the friction contact, and the deformation of pile is more significant. By comparing the working conditions of different thicknesses of overlying saturated loose sand layer, it is found that the degree of liquefaction in shallow soils is less affected by thickness of the saturated loose sand. As the thickness of saturated loose sand layer increases, the peak bending moment and residual displacement at the top of the pile also gradually increase. The change of peak bending moment at the soil interface is more obvious.

Hydrology Outweighs Temperature in Driving Production and Export of Dissolved Carbon in a Snowy Mountain Catchment

AbstractTerrestrial production and export of dissolved organic and inorganic carbon (DOC and DIC) to streams depends on water flow and biogeochemical processes in and beneath soils. Yet, understanding of these processes in a rapidly changing climate is limited. Using the watershed‐scale reactive‐transport model BioRT‐HBV and stream data from a snow‐dominated catchment in the Rockies, we show deeper groundwater flow averaged about 20% of annual discharge, rising to ∼35% in drier years. DOC and DIC production and export peaked during snowmelt and wet years, driven more by hydrology than temperature. DOC was primarily produced in shallow soils (1.94 ± 1.45 gC/m2/year), stored via sorption, and flushed out during snowmelt. Some DOC was recharged to and further consumed in the deeper subsurface via respiration (−0.27 ± 0.02 gC/m2/year), therefore reducing concentrations in deeper groundwater and stream DOC concentrations at low discharge. Consequently, DOC was primarily exported from the shallow zone (1.62 ± 0.96 gC/m2/year, compared to 0.12 ± 0.02 gC/m2/year from the deeper zone). DIC was produced in both zones but at higher rates in shallow soils (1.34 ± 1.00 gC/m2/year) than in the deep subsurface (0.36 ± 0.02 gC/m2/year). Deep respiration elevated DIC concentrations in the deep zone and stream DIC concentrations at low discharge. In other words, deep respiration is responsible for the commonly‐observed increasing DOC concentrations (flushing) and decreasing DIC concentrations (dilution) with increasing discharge. DIC export from the shallow zone was ~66% of annual export but can drop to ∼53% in drier years. Numerical experiments suggest lower carbon production and export in a warmer, drier future, and a higher proportion from deeper flow and respiration processes. These results underscore the often‐overlooked but growing importance of deeper processes in a warming climate.

Spatial distribution of soil depth in relation to slope as a consequence of erosion-accumulation processes in loess lowland hills of Slovakia

Abstract In our study, we examined the influence of slope gradient on erosion processes and present soil formation and change on loess hills. We analysed data from the two study areas and found that slope gradient is a significant factor influencing soil depth as well as humus horizon thickness. At the Báb locality, we observed a negative correlation between slope gradient and soil depth (r = –0.206, p < 0.05) and a negative correlation between slope gradient and humus horizon thickness (r = –0.227, p < 0.01). At the Nová Vieska locality, there was a negative correlation between slope gradient and soil depth (r = –0.334, p < 0.02), as well as between slope gradient and humus horizon thickness (r = –0.356, p < 0.01). These findings confirm that slope gradient is a key factor influencing soil formation in loess hills, and has a significant impact on its depth and soil profile. The analysis revealed that a critical slope of 3° significantly influences soil formation, with shallower soils and a thinner humus horizon occurring on steeper slopes. Our findings have important implications for planning erosion control measures and soil management depending on the location and slope gradient. Overall, our work provides insights into soil formation processes in loess hills and contributes to a better understanding of the interactions between slope gradient and erosive processes.

Liquefaction Potential Analysis of Irrigation Canals at Sidera Area-Sigi Regency

Abstract An earthquake measuring 7.5 on the Richter scale that occurred in Palu on 28 September 2018 resulted in liquefaction where the soil lost its bearing capacity due to increased pore water pressure. The liquefaction disaster caused great damage to the Gumbasa Irrigation channel, a large part of which is in the alluvial fan area. This study aims to analyze the potential of liquefaction in irrigation canals in the Sidera village area, Sigi Regency. Using SPT (Standard Penetration Test) data from 2 boreholes with a depth of ± 20 m, MASW data, and Earthquake Risk Map. Researchers analyzed with the Seed Simplified Procedure approach, The researchers analyzed the Simplified Procedure method proposed by Seed, which uses a stress-based approach that uses the ratio of soil shear strength (CRR) and earthquake-induced soil shear stress (CSR). The results of the analysis using Peak Ground Acceleration (PGA) of 0.43 and groundwater level variations of -2.85 m (borehole BM 53) and -12.5m (Borehole BM 49) show that liquefaction occurs at depths of 4-8 m (BM 53) and 14-17 m (BM 49). The value of the Liquefaction Potential Index (LPI) increases and indicates a high liquefaction potential below the water table with the highest value of 17.88. The analysis shows that liquefaction is closely related to the shallow water table, soil type, and low N-SPT values. The high liquefaction potential requires prevention methods as a form of treatment.

Growth, earlywood anatomy and wood nutrients respond to precipitation and flow in semi-arid riparian tamarisk forests

Riparian forests from semi-arid regions with saline soils are dominated by facultative phreatophytes such as tamarisks (Tamarix spp.). Tamarisks tolerate drought and salt stress by using shallow and deep soil water sources depending on precipitation and flow variability in ephemeral or permanent streams. Therefore, their radial growth and wood anatomy would differently respond to precipitation and drought severity depending on stream ephemerality. To assess these responses, tree-ring-width, earlywood anatomy and sapwood nutrient concentrations were measured in five riparian tamarisk stands located in semi-arid north-eastern Spain. These sites experienced different aridity degrees and were located near ephemeral (e.g., Lanaja-dry site) or permanent streams in intensively irrigated agricultural areas (e.g., Valcuerna). Tree rings were widest in Peñaflor (2.94 mm) and narrowest in the driest Lanaja-dry site (1.11 mm), where tree-to-tree growth coherence was higher than in the other sites. Wet conditions during the water year enhanced growth, particularly in the most responsive Lanaja-dry site and in Lopín, whereas elevated flow increased the earlywood hydraulic diameter in Valcuerna. In the Lanaja-dry site, Ca, Cu, K and Mn wood concentrations were higher than in Valcuerna, but C and N concentrations were lower. Elevated Ca wood concentrations correspond to higher drought stress in the Lanaja-dry site, whereas higher N concentrations reflect eutrophication due to extensive use of agricultural fertilizers in Valcuerna. In sites near permanent streams such as Valcuerna, depth to groundwater may be a more robust proxy of growth than in drier sites located near more ephemeral streams such as Lanaja-dry site where tamarisk growth is constrained by 12-month long spring droughts.

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Shallow Soil Response to a Buried Chemical Explosion With Geophones and Distributed Acoustic Sensing

Variable soil moisture responses to rainfall events in fields under different management practices

AbstractSoil moisture response to rainfall is a key factor that dictates how well a landscape can support crop growth as well as its susceptibility to water runoff and leaching, however, few studies have investigated how agricultural management impacts this important soil function. This study compares two common agricultural soil treatments (cover crops and soil compaction) and their soil moisture response to rainfall in comparison to a control. In a humid temperate climate during March to November, individual rainfall events were delineated over two growing seasons and corresponding soil moisture responses were identified using in situ soil moisture sensors at four soil depths (20, 30, 40, and 60 cm). Results suggest that hydrological responses differed with both event type and management treatment. Not all rainfall events triggered a response: those that triggered responses at shallower soil depths were typically characterized by higher total event rainfall, and higher maximum and average rainfall intensity. In contrast, rainfall events triggering responses at deeper soil depths were characterized by longer event duration as well as higher 10‐day antecedent rainfall (AR). Soil moisture responses for the cover crop treatment were characterized by relatively lower initial and peak soil moisture at shallower depths but higher values at 60 cm depth, whereas soil moisture responses for the control and compacted soil treatments demonstrated the opposite. Matrix flow was most often generated for rainfall events with high magnitude and was not preferentially associated with any particular soil treatment. However, specific conditions were needed to generate vertical preferential flow, namely high total event rainfall for both horizons, or high AR for preferential flow in the Ap horizon, or high rainfall intensity for preferential flow in the Bt horizon. Our findings demonstrate the potential for detailed event‐based soil water process analysis using high‐frequency, multi‐depth soil moisture data.

The biogeophysical impacts of land cover changes in Northern Hemisphere permafrost regions

The permafrost zone in the Northern Hemisphere has experienced substantial land cover changes (LCCs) in recent decades, resulting in significant impacts on climate and ecosystems by regulating land–atmosphere interactions, energy, water fluxes, and carbon exchange. However, the response of LCCs to climate change is highly variable, especially in terms of biogeophysical effects in high latitude regions. The goal of this study therefore is to quantify the biogeophysical effects of LCCs in Northern Hemisphere permafrost regions. We combine land cover and climate data and separate natural and biogeophysical impacts of LCCs to estimate the contribution on the surface and shallow soil temperatures. From 2001 to 2020, approximately 26 % of the permafrost zone experienced LCCs. LCCs caused a decrease in albedo (−0.15 ± 1.03 %) and an increase in snow depth (2.04 ± 31.96 cm), evapotranspiration (2.19 ± 11.37 mm), and surface heat flux (0.09 ± 1.36 W/m2), resulting in an increase in temperatures: 0.03 ± 0.42 K (surface temperature), 0.07 ± 0.46 K (0–10 cm soil temperature), 0.07 ± 0.45 K (10–100 cm soil temperature), and 0.06 ± 0.43 K (100–200 cm soil temperature), which could increase the risk of permafrost degradation. Seasonally, LCCs exacerbate the temperature difference between winter and summer. Albedo dominates surface temperature changes, with about 87.5 % of surface temperature changes coinciding with albedo changes. Soil temperatures are regulated by snowpack and surface heat fluxes, in addition to albedo.

Shaking table tests and numerical analysis of monopile-supported offshore wind turbines under combined wind, wave and seismic loads

Currently, large-diameter monopile-supported offshore wind turbines (OWTs) are widely used in offshore areas of China. However, considerable numbers of wind farms are located in seismically active areas with liquefiable soil layers. Therefore, shaking table tests and numerical simulation based on a scaled model of Siemens SWT-4.0-130 OWTs were carried out to investigate the failure mechanism of the OWT system in liquefiable sand under combined wind, wave and seismic loads. The scaling law focusing on the governing physical mechanism of the OWT system considering multi-field coupling are presented and verified. The dynamic responses of the OWT and the excess pore pressure fluctuation around the soil-monopile domain in different operating states are discussed and compared. The results show that the proposed scaling laws can well restore the dynamic characteristics of the prototype. The seismic excitation is the dominant load for inducing the structural response under combined wind, wave and seismic loads. Due to the coupling effect, the dynamic responses under combined wind and wave loads were slightly less than the superposition of structural responses under separated wind or wave loads. Liquefaction of the shallow soil layer within the range of four times the pile diameter was detected when the PGA reached 0.4 g (three-dimensional input) or 0.64 g (one-dimensional input), which induced obvious tilt and settlement of the OWT model after the test. The sudden increase in the pore pressure resulted in the liquefaction of soil, which further led to a significant decrease in the natural frequencies and decay of the acceleration responses at the tower top. The above findings are expected to provide valuable experience for the 1 g underwater shaking table tests on OWT systems and insights for the practical design of OWTs in seismically active areas.

Natural Hydrogen in the Northern Perth Basin, WA Australia: Geospatial Analysis and Detection in Soil Gas for Early Exploration

The scope of this work is to empirically check and prove the practical applicability of the Primordially Hydridic Earth (PHE) concept for early exploration of the resources of naturally occurring hydrogen. With the PHE concept postulates interpreted within the local geological, tectonic, petrological and geophysical context, the reconnaissance plan, as well as the field exploration and data acquisition programs, were put together and implemented in the field. The results obtained from the surface (<1m deep) soil gas survey performed in Western Australia (WA) resulted in values of hundreds of ppm H<sub>2</sub>, including three samples with a concentration of hydrogen exceeding the gas sensor detection limit of 2,000 parts per million (ppm) (the all-Australia record). Similarly, several of the shallow soil samples used for obtaining headspace gas extracts yielded dozens % H<sub>2</sub>, which was established utilizing Gas Chromatography (GC) technology. The latter tests established the all-Australia record of 58.3% (norm.) H<sub>2</sub> concentration from 15 m depth, being the highest reading from the area of research. At one location, a concentration of He exceeding 8,000ppm was detected in a 1m surface soil gas sample analyzed by the independent lab. The most important outcome was finding natural hydrogen where it was expected and predicted. On the other hand, H<sub>2</sub> concentrations exceeding the natural background of 1-3ppm were not detected in the soil gas readings outside of the areas identified using the PHE concept as a theoretical foundation. It may be stated that overall, the practical application of the PHE concept along with the thoroughly planned utilization of carefully selected exploration techniques brings satisfactory results.

Soil development trajectories, chemical weathering and pedogenic mineral (trans)formation on glauconitic calcarenites in a Mediterranean area

Glauconite forms in shallow marine basins under oxic to suboxic conditions. It is an Fe-rich sheet silicate often found in calcareous sandstones. How soils evolve on glauconitic sandstones (calcarenite) is poorly addressed: therefore, we investigated the evolutional trajectories. These soils should be enriched in Fe, depleted in K and contain kaolinite and smectite resulting from weathering. We investigated 11 soil profiles on glauconitic calcarenite in a Mediterranean area. The elemental contents, fractions of Fe and Al, soil mineralogy, magnetic susceptibility and stable isotopic composition (C, O) of the bulk soil and carbonates were analysed to explore pedogenesis.The carbonates reflect a former marine basin having onshore organic matter resulting from freshwater input. With soil formation, the primary carbonates were replaced by pedogenic carbonates having a lower δ13C and δ18O signal. Several sites were influenced by human activity since ancient times, reflected by the magnetic susceptibility. The shallow soils had a low weathering degree (CIA of 55 to 70). The better developed Vertisols exhibited a CIA value of up to 85. All soils contained smectite and quartz and, depending on the weathering degree, calcite. Kaolinite formation was connected to high Ca, K, Mg and Na losses. The high oxalate- and dithionite-extractable Fe contents are explained by glauconite weathering. Kaolinite is inherited from the parent material but also actively forms in the soils probably through precipitation from soil water. Due to the presence of smectite and oxyhydroxides the soils sequester a high amount of soil organic carbon (up to 30 kg/m2). Topography exerts a distinct influence on weathering and soil formation. Deepest soils and an advanced weathering stage were measured on footslope sites and shallow soils having a low weathering degree on crest/shoulder sites. Soils on glauconitic calcarenite represent a unique weathering environment that should be investigated even more at the micro-scale.

Soil depth and catchment geomorphology: A field, vegetation and GIS based assessment

Soil depth is closely related to topography and influences vegetation health and landscape productivity at both hillslope and catchment scales. Soil depth also influences land management and ecosystem sustainability. However, comprehensive hillslope and catchment scale soil depth data remain scarce. In response, this study investigates the relationship between soil depth, surface and bedrock topographic metrics (elevation, slope, aspect, and SAGA topographic wetness index - SWI), and pasture response within a semi-arid hillslope ecosystem in south-eastern Australia. The Normalized Difference Vegetation Index (NDVI) was used as an indicator of vegetation health. A dataset of 183 soil depth measurements was collected using a petrol-powered auger across a 6-ha catchment. Our findings reveal that the relationships between soil depth, topography and vegetation response are complex. There was a general increase in soil depth downslope, indicating potential fluvial transport processes involving erosion and deposition. A subtle increase in NDVI was observed upslope. Soil depth showed no strong correlations with aspect or SWI, but a weak inverse relationship was observed with slope angle. Notably, NDVI displayed a positive correlation with SWI while showing an inverse correlation with slope. Furthermore, the study highlights instances of shallower soils and reduced grass cover beneath two isolated trees, potentially attributable to cattle movement. Soil erosion rates for the catchment are known and soil production rates can be estimated. The data suggests that under current land use practices, soil is being lost at a rate faster than it is being produced. These findings provide valuable insights for land management strategies and sustainable ecosystem maintenance, while demonstrating the complexity of the soil-landscape system.

Research on early identification of burning status in a fire area in Xinjiang based on data-driven

The early combustion stage in coalfield fire areas (CFA) is the initial phase of coal fire development and spread, making the effective identification of the combustion state crucial. To effectively identify the early combustion state of CFA, this study investigates the CFA in Xinjiang, China. Based on the abnormal characteristics of shallow soil and surface space, a data-driven evaluation method for identifying early combustion states of CFA is proposed. Construct a soil-gas dual-layer early combustion state assessment model of CFA. The evaluation model was applied and validated in the coal fire areas of Xinjiang, China.The results show that there are obvious differences in the spatial distribution of auto-ignition gas, temperature, humidity, surface vegetation coverage and other indicators in the shallow soil and surface space of the coal fire area. The early combustion states of coal fires in areas A, B, and C in the survey area are all in the combustion stage, the combustion state in area D is in the oxidation stage. The accuracy of the evaluation method is bidirectionally verified by the radon measurement method and the infrared thermal imaging detection method. It provides a theoretical basis for controlling the development and spread of coalfield fire areas.

Long-term fertilization increases soil but not plant or microbial N in a Chihuahuan Desert grassland

Abstract. Although the negative consequences of increased nitrogen (N) supply for plant communities and soil chemistry are well known, most studies have focused on mesic grasslands, and the fate of added N in arid and semi-arid ecosystems remains unclear. To study the impacts of long-term increased N deposition on ecosystem N pools, we sampled a 26-year-long fertilization (10 g N m−2 yr−1) experiment in the northern Chihuahuan Desert at the Sevilleta National Wildlife Refuge (SNWR) in New Mexico. To determine the fate of the added N, we measured multiple soil, microbial, and plant N pools in shallow soils at three time points across the 2020 growing season. We found small but significant increases with fertilization in soil-available NO3--N and NH4+-N, yet the soil microbial and plant communities do not appear to be taking advantage of the increased N availability, with no changes in biomass or N content in either community. However, there were increases in total soil N with fertilization, suggesting increases in microbial or plant N earlier in the experiment. Ultimately, the majority of the N added in this multi-decadal experiment was not found in the shallow soil or the microbial or plant community and is likely to have been lost from the ecosystem entirely.

Vegetation greening amplifies shallow soil temperature warming on the Tibetan Plateau

Vegetation changes are expected to alter soil thermal regimes, consequently modifying climate feedbacks related to frozen ground thawing and carbon cycling in cold regions. The Tibetan Plateau (TP) contains diverse alpine ecosystems and the largest area of frozen ground in low–mid latitude regions. Evidence suggests ongoing vegetation greening and permafrost degradation during the past several decades on the TP. However, the effect of vegetation changes on soil thermal regimes on the TP is not well understood. Here, we quantify the response of shallow soil temperature change to vegetation greening on the TP using remote–sensing data, in–situ observations, and physics–based modelling. Our results show that over the past 20 years, vegetation greening on the TP was accompanied a notable decrease in the area of bare land by approximately 0.7% (5000 km2). Annual mean soil temperature showed a significant warming trend of 0.57 °C decade–1 (p < 0.05) during the period 1983–2019, exceeding the warming rate of surface air temperature. Changes in vegetation resulted in a warming effect on annual shallow soil temperature of 0.15 ± 0.33 °C across the TP during the period 2000–2019. The warming effect varies with frozen soil types: 0.24 ± 0.48 °C in permafrost, 0.18 ± 0.36 °C in seasonally frozen ground, and 0.11 ± 0.32 °C in unfrozen ground. The net warming effect was caused by a decrease in albedo and increase in radiation penetrating the canopy, outweighing the cooling effect related to a limited increase in evapotranspiration.

Illuminating the “Invisible”: Substantial Deep Respiration and Lateral Export of Dissolved Carbon From Beneath Soil

AbstractDissolved organic and inorganic carbon (DOC and DIC) influence water quality, ecosystem health, and carbon cycling. Dissolved carbon species are produced by biogeochemical reactions and laterally exported to streams via distinct shallow and deep subsurface flow paths. These processes are arduous to measure and challenge the quantification of global carbon cycles. Here we ask: when, where, and how much is dissolved carbon produced in and laterally exported from the subsurface to streams? We used a catchment‐scale reactive transport model, BioRT‐HBV, with hydrometeorology and stream carbon data to illuminate the “invisible” subsurface processes at Sleepers River, a carbonate‐based catchment in Vermont, United States. Results depict a conceptual model where DOC is produced mostly in shallow soils (3.7 ± 0.6 g/m2/yr) and in summer at peak root and microbial respiration. DOC is flushed from soils to the stream (1.0 ± 0.2 g/m2/yr) especially during snowmelt and storms. A large fraction of DOC (2.5 ± 0.2 g/m2/yr) percolates to the deeper subsurface, fueling deep respiration to generate DIC. DIC is exported predominantly from the deeper subsurface (7.1 ± 0.4 g/m2/yr, compared to 1.3 ± 0.3 g/m2/yr from shallow soils). Deep respiration reduces DOC and increases DIC concentrations at depth, leading to commonly observed DOC flushing (increasing concentrations with discharge) and DIC dilution patterns (decreasing concentrations with discharge). Surprisingly, respiration processes generate more DIC than weathering in this carbonate‐based catchment. These findings underscore the importance of vertical connectivity between the shallow and deep subsurface, highlighting the overlooked role of deep carbon processing and export.

Influence of Morphometric Relief Parameters on Soil Depth Changes and Humus Horizon Thickness in Relation to Erosion-Accumulation Processes: A Study in the Ipeľská Pahorkatina Hills, Slovakia

Abstract This study examines the spatial distribution of soil types and their susceptibility to erosion and accumulation processes in a study area in Slovakia. Field research involving 71 probes identified various soil types, with Regosols and Cutanic Luvisols being predominant. The study found that erosion-accumulation processes were detected in 69.97% of the probes, with changes observed in soil horizons. Soil analysis revealed different relations between soil depth, humus thickness, and terrain characteristics such as slope, slope length, and slope length and steepness factor (LS factor). Specifically, we confirmed a moderately strong positive correlation between soil depth and humus thickness (r = 0.597, n = 71, p &lt; 0.001). Shallow soils (0–30 cm) exhibited a very strong positive correlation between soil depth and humus horizon thickness (r = 0.978, n = 33, p &lt; 0.001). Conversely, no relationship was found in moderately deep soils (30–60 cm) (r = 0.018, n = 14, p &lt; 0.948). For deep soils, we identified a moderately strong positive correlation (r = 0.345, n = 24, p = 0.098). While slope and slope length showed relationships with soil depth and humus thickness, the LS factor did not exhibit a clear correlation. These findings underscore the importance of understanding soil dynamics in informing land management practices, especially in areas susceptible to erosion. Recommendations include continued monitoring of eroded soils and implementing erosion control measures to maintain soil health and sustainability in agricultural production amidst climate change challenges.

Regulating Cotton Growth via Rhizobium Species

Unpredictable precipitation is a common problem for plant growth in India’s Deccan plateau, which is known for its poor soil and frequent droughts. Critical to the regulation of plant diseases and the enhancement of plant growth are root-colonizing rhizobacteria like Rhizobium. Isolating productive Rhizobium species from soil around the Eturnagram region’s cotton rhizosphere was the goal of a study carried out at Palamuru University. Rhizobium variant-5, currently known as Rhizobium sp. PKS [NCBI-OK663003, NCMR-MCC4960], was one of five different strains of Rhizobium isolated using the top layer method. It showed strong support for the growth of six different cotton cultivars. Out of the six cotton varieties tested, the Mahyco cultivar had the lowest proline levels while having higher amounts of IAA, proteins, chlorophyll, and sugars. The effectiveness of Mahyco was confirmed by experimental field testing conducted in four distinct cotton agricultural soils of Mahabubnagar District using Rhizobium sp. PKS [NCBI-OK663003, NCMR-MCC4960]. Deep black soil showed improved phytohormone synthesis and good biochemical alterations, whereas shallow black soil showed that the strains considerably enhanced plant development. Based on these results, the novel Rhizobium sp. PKS could be used as a bioinoculant in cotton fields on the Deccan plateau, which could improve agricultural yields despite the harsh conditions.