Deeper Soil Layers Research Articles

Unravelling arsenic bioavailability in floodplain soils impacted by mining activities

Gold mining not only introduces mercury (Hg) contamination to soils but also facilitates the mobilization of other toxic substances, including arsenic (As). This study assessed the total content, chemical species, and bioavailable fraction of As in surface soils impacted by mining residues during frequent flooding. Analysis of 207 soil samples across the floodplain region of La Mojana, Colombia, screened to 2 mm with polyethylene mesh, revealed significant correlations (p < 0.05) between inorganic As, the residual phase, sulphur (S), iron (Fe), manganese (Mn), and aluminum (Al), indicating associations with sulfides and oxyhydroxides of Fe and Mn. The origin of toxicity was linked to suspended materials transported by rivers during flooding in areas with intense mining activity. Sites with better oxidizing conditions exhibited a higher presence of phases associated with amorphous and crystalline oxides in non-flooded areas. Although the bioavailable fraction was minimal in flooded sites, reducing conditions facilitated As mobility, resulting in higher concentrations in deeper soil layers, particularly as As(III). The contamination factor (CF) ranged from 1.3 to 11.1, and the geochemical index (Igeo) ranged from −0.2 to 2.9, indicating a moderate to high As contamination level in soils. This poses potential health risks, considering the agricultural use of these soils.

Effects of Deep Vertical Rotary Tillage on Soil Water Use and Yield Formation of Forage Maize on Semiarid Land

Forage maize is one of the most important feed crops for livestock production, and is mainly grown in northwest China. However, their growth is often stressed by limited soil water availability due to the arid climate. To provide more soil moisture, a high-efficiency tillage technique was required to make crops effectively use soil moisture in deep soil layers. Deep vertical rotary tillage is a promising choice for this purpose. In this study, a long-term (2020–2022) field experiment consisting of three treatments, i.e., traditional tillage (TT), deep rotary tillage (DT), and deep vertical rotary tillage (VRT), was carried out in semiarid areas of Loess Plateau, northwest China, to investigate the effects of VRT on soil water storage (SWS), phase crop evapotranspiration (ETc) during the pre- and post-flowering periods, dry matter accumulation, grain yields and the water use efficiency (WUE) of forage maize. The results showed that VRT significantly improved the absorption of soil moisture from deep layers, especially in dry years. During the pre-flowering period of a dry year (2020), VRT decreased SWS by 7.6%–10.0% in the 60–180 cm layer, and by 17.6%–18.5% in the 180–300 cm layer, respectively, compared to DT and TT. As a result, VRT increased ETc during the pre-flowering period by 6.1% and 9.2%, respectively. In wet years (2021 and 2022), VRT increased total ETc by 2.0%–7.9% in 2021, and by 10.1%–14.9% in 2022, respectively. On average, VRT increased the dry matter weight per plant by 1.0%–7.8%, grain yields by 2.4%–38.6%, biomass yields by 3.4%–16.2%, and WUE by 10.1%–30.0%, respectively. Particularly, the benefit of VRT for increasing yields and WUE was more noticeable in dry years. It can be concluded that VRT is a drought-tolerant and yield-boosting tillage technique that is suitable for rain-fed forage maize in semiarid areas of Loess Plateau, northwest China.

Quantitative importance of subsoil nitrogen cycling processes in Andosols and Cambisols under temperate forests

Nitrogen availability often limits plant growth in forest ecosystems. Plants, including trees, utilize soil inorganic nitrogen transformed via nitrogen cycling processes, including mineralization and nitrification. While most plant fine roots are distributed in surface soil layers, plants take up nitrogen even from subsurface soil layers in addition to the surface soil layers, especially under high nutrient competition. However, there is still limited knowledge about nitrogen cycles within deeper soil layers. In this study, we investigated the vertical profiles (0–60 cm) of the net nitrogen mineralization and nitrification rates at four Japanese forest sites with two different soil types (Andosols and Cambisols). The partial least square path modeling (PLS-PM) was used to determine factors affecting nitrogen cycling processes. The net nitrogen mineralization and nitrification rates per unit soil weight were considerably higher in the surface soil layer than in the deeper soil layers in Andosols but not in Cambisols. PLS-PM analysis showed that microbial biomass and soil organic matter quantities were the important factors influencing the net nitrogen mineralization and nitrification rates, indicating that a similar mechanism, which drives the spatial variations of nitrogen cycling processes in the surface soil layer, predominantly regulates the vertical variations of the processes. Moreover, it was estimated that the net nitrogen mineralization rate could be comparable at all soil types and depths when the rate was expressed per unit soil volume. Therefore, subsoil layers could be a quantitatively important source of plant-available nitrogen in Andosols and Cambisols.

Multi-trait association mapping for phosphorous efficiency reveals flexible root architectures in sorghum

BackgroundOn tropical regions, phosphorus (P) fixation onto aluminum and iron oxides in soil clays restricts P diffusion from the soil to the root surface, limiting crop yields. While increased root surface area favors P uptake under low-P availability, the relationship between the three-dimensional arrangement of the root system and P efficiency remains elusive. Here, we simultaneously assessed allelic effects of loci associated with a variety of root and P efficiency traits, in addition to grain yield under low-P availability, using multi-trait genome-wide association. We also set out to establish the relationship between root architectural traits assessed in hydroponics and in a low-P soil. Our goal was to better understand the influence of root morphology and architecture in sorghum performance under low-P availability.ResultIn general, the same alleles of associated SNPs increased root and P efficiency traits including grain yield in a low-P soil. We found that sorghum P efficiency relies on pleiotropic loci affecting root traits, which enhance grain yield under low-P availability. Root systems with enhanced surface area stemming from lateral root proliferation mostly up to 40 cm soil depth are important for sorghum adaptation to low-P soils, indicating that differences in root morphology leading to enhanced P uptake occur exactly in the soil layer where P is found at the highest concentration.ConclusionIntegrated QTLs detected in different mapping populations now provide a comprehensive molecular genetic framework for P efficiency studies in sorghum. This indicated extensive conservation of P efficiency QTL across populations and emphasized the terminal portion of chromosome 3 as an important region for P efficiency in sorghum. Increases in root surface area via enhancement of lateral root development is a relevant trait for sorghum low-P soil adaptation, impacting the overall architecture of the sorghum root system. In turn, particularly concerning the critical trait for water and nutrient uptake, root surface area, root system development in deeper soil layers does not occur at the expense of shallow rooting, which may be a key reason leading to the distinctive sorghum adaptation to tropical soils with multiple abiotic stresses including low P availability and drought.

A short-term effect of multi-species pastures and the plant’s physiological response on pasture growth

Multi-species pastures that include species with dissimilar physiological responses to water restriction (i.e., dehydration avoidance) and species that have a greater soil water access (i.e., deep-rooted species), can buffer the reduction in summer growth experienced by more shallow-rooted species and can out-yield pastures with less capacity to access soil water. The aim of the present study was to evaluate the performance of multi-species pastures comprising both deep-rooted and shallow-rooted species, under grazing by sheep, in relation to pasture growth, the seasonal changes in pasture botanical composition, and the plants’ physiological responses to field conditions across the year. The evaluated pastures were: Bromus valdivianus (Bv); Lolium perenne + Trifolium repens (Lp); Plantago lanceolata (Pl); B. valdivianus + L. perenne + T. repens (grass mixture pasture, GM); and B. valdivianus + L. perenne + T. repens + P. lanceolata (complex mixture pasture, CM). Herbage mass, net photosynthesis, leaf water relations and soil water content (SWC) at 10, 40 and 70 cm soil depths were evaluated. The SWC fluctuation through the year was related to rainfall within each season, and differences between the treatments were taken as an indirect indicator of soil water access and soil water uptake by the roots. During the soil water restriction period, mixed pastures based on species that differed in their soil water access buffered the reduced growth rate of the sensitive species, due to a decrease in competition for water uptake within the deeper soil layer (CM pasture). A shift of dominance between species, as measured in the CM pasture, buffered the reduction in pasture growth rate seen in the monocultures. The Bv pasture, which is tolerant of water restriction, had a similar annual yield to the multi-species pastures (both GM and CM). The present study highlighted the capacity of the deep-rooted species (B. valdivianus and P. lanceolata) to avoid periods of soil water restriction by extracting water from deeper soil layers.

Challenges in geochemical modelling of metal(loid) solubility and binding mechanisms along a soil profile at a multi-contaminated site

Recognising the need for robust models in predicting groundwater contamination risks from metal(loid)s in contaminated topsoil, this study focuses on the geochemical behaviour of As, Cd, Cu, Pb, Sb and Zn in one of Sweden's most heavily contaminated areas. Samples were collected from the waste zone and underlying subsoil down to 5 m and batch experiments were carried out to assess pH-dependent solubility. The results indicate that Cd, Cu, Pb and Zn are efficiently immobilized in the waste zone, while As(V) and Sb(V) are more easily leached. With the exception of Pb and Cu at high pH, the mobilized metals appear to be predominantly in a truly dissolved state, as confirmed by ultrafiltration at 10 kDa.Speciation modelling using Visual MINTEQ did not suggest a significant role of precipitates such as Zn or Pb arsenates and phosphates, although their involvement could not be ruled out. To better understand sorption/desorption patterns, a multi-surface geochemical model was established, drawing on the Stockholm Humic and CD-MUSIC models for organic matter and Fe/Al (hydr)oxide sorption. However, when default parameters were used, the model consistently overestimated the solubility of Cd, Cu, Pb and Zn in both the waste zone and the uncontaminated subsoil. In contrast, As(V) solubility was generally underestimated, also when the reactive surface area of the Fe- and Al (hydr)oxides was decreased in the model. The model's performance was better for Sb(V), though not without imperfections. When the parameters for organic matter were adjusted such that 100% of the solid-phase organic matter was active with respect to ion binding, but only 25% of the dissolved organic matter, the model description improved considerably for Pb and Cu in the upper soil layers. The model revealed distinct differences in the adsorption behaviour of the metal cations, with Pb being sorbed mostly to Fe/Al (hydroxides), whereas a considerable part of Cu was sorbed to organic matter, particularly in the waste zone.Possibly, the dissolution of easily weatherable metal-containing mineral phases may have contributed to the poor model performance for Cd, Zn and for Cu in the deeper soil layers, although other factors, such as a contribution of hydrous SiO2 or Mn oxides to metal binding, could not be ruled out. Metal sorption to carbonate phases may also have been a contributing factor in the waste zone. Lastly, the reactivity of Fe- and Al (hydr)oxides may have been overestimated by oxalate extraction when default parameters for high-surface-area ferrihydrite were applied.These findings provide valuable insights for environmental management and underscore the need for a more detailed characterization of metal(loid) sorption in contaminated soils, as well as the development of improved modelling strategies to enhance solubility predictions.

The limited effect of deforestation on stabilized subsoil organic carbon in a subtropical catchment

Abstract. Predicting the quantity of soil organic carbon (SOC) requires understanding how different factors control the amount of SOC. Land use has a major influence on the function of the soil as a carbon sink, as shown by substantial organic carbon (OC) losses from the soil upon deforestation. However, predicting the degree to which land use change affects the OC content in soils and the depth down to which this occurs requires context-specific information related to, for example, climate, geochemistry, and land use history. In this study, 266 samples from forests and agricultural fields were collected from 94 soil profiles down to 300 cm depth in a subtropical region (Arvorezinha, southern Brazil) to study the impact of land use on the amount of stabilized OC along the soil profile. We found that the stabilized OC content was not affected by land use below a depth of 90 cm. Along the soil profile, the amount of stabilized OC was predominantly controlled by land use and depth in addition to the silt and clay content and aluminium ion concentrations. Below 100 cm, none of the soil profiles reached a concentration of stabilized OC above 50 % of the stabilized OC saturation point (i.e. the maximum OC concentration that can physically be stabilized in these soils). Based on these results, we argue that it is unlikely that deeper soil layers can serve as an OC sink over a timescale relevant to global climate change due to the limited OC input in these deeper layers. Furthermore, we found that the soil weathering degree was not a relevant control on the amount of stabilized OC in our profiles because of the high weathering degree of the studied soils. It is therefore suggested that, while the soil weathering degree might be an effective controlling factor of OC stabilization over a large spatial scale, it is not an informative measure for this process at regional and local scales (with similar climate, bedrock, and weathering history) in highly weathered soils.

STUDI KOMPARASI KAPASITAS DUKUNG RENCANA DAN KAPASITAS DUKUNG AKTUAL FONDASI TIANG PANCANG PADA KONSTRUKSI SLAB ON PILE JALAN TOL SEMARANG – DEMAK SEKSI 2

Semarang - Demak Toll Road Section 2 with a length of 16.31 km crosses the North Coast of Java. The regional geological map shows that the North Coast of Java has alluvial soil layers with clay and silt characteristics. The results of soil investigations show that the depth of the soft layer reaches more than 60 m. This condition triggers construction engineering to support the Highway above it. One of the efforts to fulfill the elevation plan (finish grade) is the flyover concept with slab on pile construction. The planned traffic lane is laid on a concrete slab which is supported by piles with a diameter of 600 mm. With sufficiently deep soft soil layers, the bearing capacity of the foundation piles is borne by the frictional resistance provided by the soil along the piles. This comparative study compares the planned carrying capacity calculated by the empirical formula with the actual carrying capacity of the field as a result of the PDA Test. Calculations were made on 5 test poles for later comparisons were made with the PDA test record data. For the case of 14 days driving at the research location, the pile bearing capacity from the PDA test results is still below the design bearing capacity. The average actual carrying capacity obtained from the 5 test piles is 278 tons. This value is below the planned carrying capacity of the Shio &amp; Fukui method of 381 tons, Meyerhoff's 355 tons, Biaud et al's 777 tons, and Luciano Decourt's 605 tons. At the age of the pile 14 days after the erection was completed, the results of the calculation of the bearing capacity of the Meyerhoff method are closest to the actual bearing capacity of the PDA test results with a ratio of 1.26. The next method is Shio &amp; Fukui with a ratio of 1.36, Luciano Decourt (2.16), and Biaud et al (2.81). Some of the results of previous studies showed a positive correlation between the age after completion of the pile and the frictional carrying capacity. For this type of friction pile, this is of course very influential, so that it is possible that when it is realized that it is carried out with a longer service life, the actual bearing capacity obtained will increase. This requires further research to obtain a time relationship with an increase in pile bearing capacity, especially for locations that have deep soft soil layers such as in this study location.

Combined effects of rainfall‐runoff events and antecedent soil moisture on runoff generation processes in an upland forested headwater area

AbstractIn this study, we investigate the combined effect of different rainfall‐runoff event types and antecedent soil moisture (ASM) on runoff processes in the headwater elementary discharge area of a small forested upland catchment. The study focuses on (i) the relationship between soil moisture thresholds and runoff generation; (ii) the combined effect of ASM and tree vicinity and (iii) the relationship between different rainfall‐runoff event types and different types of runoff (baseflow and stormflow). The results suggest that ASM has a strong impact on local runoff generation processes. Soil water content (35%–36%) threshold exceedance was related to stormflow runoff generation caused by the activation of quick preferential flow paths in the soil during storm events, especially in the upper and the deepest soil layers. At the same time, unexpected non‐linear increases in baseflow runoff ratios were documented during dry, precipitation‐free, periods and when the 31%–34% soil moisture threshold was exceeded, presumably due to the hydrological connection of farther slope areas during these conditions. Multiple stormflow periods, which exhibited the lowest runoff coefficient, were the most significant events in terms of water retention and soil water recharge due to increased vertical hydrological connectivity enabling more rapid transport to deeper soil layers. However, this rainfall type occurred least often over the study period. The important role of forest stands (individual trees) in creating spatial patterns of soil moisture and preferential infiltration paths to deeper soil layers was also confirmed. These results contribute towards a better conceptualisation of hydrological behaviour in elementary headwater discharge areas and highlight the potential dangers associated with expected increases in extreme weather events.

Impact of roots on the shear strength of root-reinforced soil on slopes

Abstract Tropical countries generally receive high rainfall throughout the year causing high runoff, wet soils and erosion. Undulating terrain from continuing erosion and frequent occurrences of landslides are the features of topographic evolution under such hydrological conditions. Vegetation is the only natural supporting factor that mitigates both erosion and landslides. It contributes to controlling soil erosion and strengthening of the soil by forming a mesh of roots at the surface. The objective of this study is to quantify soil strength on slopes when there is a presence of roots. Undisturbed samples were taken from two different depths of soil. The exact depth and distance varied slightly to avoid large roots and large gravel particles present in the natural environment. Immediately after sampling, the triaxial tests were performed under unconsolidated and undrained conditions. Subsequently, the tested samples were crushed carefully, to manually recover all roots and to classify the soil. From this study, it was observed that the presence of root fibres within the soil matrix has enhanced the soil strength through a binding action in the fibre-soil composite. The correlation between root content and shear strength is prominent near the surface and becomes less obvious in deeper soil layers when the root concentration becomes more sparsely distributed.

Hydrometeorological response to afforestation in the UK: findings from a kilometer-scale climate model

Afforestation is of international interest for its positive benefits on carbon storage, ecology, and society, but its impacts on terrestrial and atmospheric processes are still poorly understood. This study presents the first use of a coupled land surface and convection permitting atmospheric model (CPM) to quantify hydrometeorological effects of afforestation across the United Kingdom, focusing on atmospheric processes often missing in hydrological models. Generating a scenario of 93 000 km2 (40%) additional woodland across the UK, the periods of 2042–2052 and 2062–2072 are analysed. Simulated afforestation alters seasonal and regional UK hydrometeorology. Countrywide runoff increases in all seasons (between 5.4–11 mm and 4.3–8.6% per season) due to elevated subsurface flows from greater soil moisture. Evaporation decreases in summer (−20.6 mm, −10%) but increases in winter (8.1 mm, 15%) whereas rainfall increases throughout all seasons (between 2.2–6.86 mm and 0.9%–2.2% per season). Greater winter rainfall is detected along Great Britain’s west coastline as increased surface roughness produces prolonged and heavier rainfall. In the summer, lower albedo increases potential evapotranspiration and reduces near surface specific humidity: water is locked in deeper soil layers as transpiration diminishes and the topsoil dries out. However, the magnitude of hydrometeorological change due to altered land cover is smaller than the uncertainty in local climate change projections. This work sets a precedent in illustrating the impacts of afforestation on hydrology using a high-resolution CPM and highlights the importance of coupled hydrometeorological processes when investigating land cover impacts on hydrological processes.

Bare Patches Created by Plateau Pikas Contribute to Warming Permafrost on the Tibet Plateau

AbstractPlateau pikas, small mammals native to the Qinghai‐Tibet Plateau (QTP), create bare patches through burrowing. No previous assessment exists on their impact on permafrost. This study fills this gap by simulating hypothetical scenarios in the Three Rivers Headwaters Region of the QTP using the Noah‐MP model for the plant growing seasons during 2015–2018. Our findings reveal a significant increase in soil temperature in the active layer due to pika‐induced bare patches, particularly during July–August. The average temperature rise at 2.5 cm depth was 0.36°C in permafrost regions and 0.29°C in seasonally frozen ground regions during August. Minimal impact on unfrozen water content was observed, with a slight increase in deep soil layers in permafrost regions, and negligible in seasonally frozen areas. These findings underscore the previously unexplored influence of pika burrowing on permafrost temperature, suggesting a potential risk of accelerating permafrost degradation, especially in permafrost‐dominated regions.

Soil moisture and soil organic carbon coupled effects in apple orchards on the Loess Plateau, China

A large number of economic forests, especially apple orchards (AOs) in the Loess Plateau region of China, have been planted to develop the local economy and increase the income of farmers. The two main constraints preventing AOs on the Loess Plateau from developing sustainably and producing a high and steady yield are soil moisture content (SMC) and soil organic carbon (SOC). Nevertheless, little is currently known about the contributions of roots to these changes in the soil profile and the temporal modes of the SMC-SOC coupled effects. In our research, we analyzed the dynamic changes in SMC and SOC in AOs of various years in northern Shaanxi Province, as well as the coupled relationship between the two, and attempted to describe the function of roots in these changes. Research have shown: (1) As the age of the AOs increased, the SMC continued to decline throughout the 0–500 cm profile, especially at depths of 100–500 cm. SMC depletion mainly occurred in AOs aged 20 years (30.02%/year) and 30 years (31.18%/year). (2) Compared with abandoned land (AL), all the AOs except for the 6-year-old AO showed a carbon sequestration effect, and the carbon sequestration effect increased with age. The carbon sequestration rate of the 12-year-old AO was the highest and then decreased with age. Both surface and deeper soils showed better carbon sequestration, with a large amount of SOC being sequestered in deeper soil layers (> 100 cm). (3) The coupled effects of SMC and SOC varied with age and depth. The SMC in the deeper layers was significantly negatively correlated with SOC. Root dry weight density (RDWD) was significantly negatively correlated with SMC and significantly positively correlated with SOC. Path analysis suggested that SMC directly affects SOC at different soil depths, and regulates SOC by affecting RDWD, but these effects are significantly different at different depths. Therefore, we propose that management of AO should focus on the moisture deficit and carbon sequestration capabilities of deeper soils to ensure the sustainability of water use in AOs and the stability of agricultural carbon sequestration on the Loess Plateau.

Precipitation exacerbates spatial heterogeneity in the propagation time of meteorological drought to soil drought with increasing soil depth

The propagation of meteorological droughts to soil droughts poses a substantial threat to water resources, agricultural production, and social systems. Understanding drought propagation process is crucial for early warning and mitigation, but mechanisms of the propagation from meteorological drought to soil drought, particularly at varying soil depths, remain insufficiently understood. Here, we employ the maximum correlation coefficient method and the random forest (RF) model to investigate the spatiotemporal patterns and drivers of propagation time (PT) from meteorological drought to soil drought at four different depths across China from 1980 to 2018. Our findings reveal consistently higher PT in northern China and lower PT in southern China across varying soil depths, with more pronounced spatial heterogeneity with increasing soil depth. Furthermore, we identify temperature and precipitation as determinants of spatial patterns of PT in surface and deeper soil layers, respectively. Additionally, precipitation emerges as the dominant factor influencing changes in PT between different soil layers. Our study highlights a discernible shift in PT drivers from temperature to precipitation as soil depth increases and the significant impact of precipitation on exacerbating spatial heterogeneity in PT. This study contributes to an enhanced comprehension of the propagation process from meteorological drought to soil drought at different depths, which can aid in establishing practical drought mitigation measures and early warning systems.

Biomass recovery of coastal young mangrove plantations in Central Thailand

Around one-third of the world’s most carbon-rich ecosystems, mangrove forests, have already been destroyed in Thailand owing to coastal development and aquaculture. Improving these degraded areas through mangrove plantations can restore various coastal ecosystem services, including CO2 absorption and protection against wave action. This study examines the biomass of three coastal mangrove plantations (Avicennia alba) of different ages in Samut Prakarn province, Central Thailand. Our aim was to understand the forest biomass recovery during the early stages of development, particularly fine root biomass expansion. In the chronosequence of the mangrove plantations, woody biomass increased by 40% over four years from 79.7 ± 11.2 Mg C ha-1 to 111.7 ± 12.3 Mg C ha−1. Fine root biomass up to a depth of 100 cm was 4.47 ± 0.33 Mg C ha−1, 4.24 ± 0.63 Mg C ha−1, and 6.92 ± 0.32 Mg C ha−1 at 10, 12, and 14 year-old sites, respectively. Remarkably, the fine root biomass of 14-year-old site was significantly higher than those of the younger sites due to increase of the biomass at 15–30 cm and 30–50 cm depths. Our findings reveal that the biomass recovery in developing mangrove plantations exhibit rapid expansion of fine roots in deeper soil layers.

Effects of the freeze–thaw process on sources and pathways of subsurface flow in an alpine hillslope on the northeastern Qinghai-Tibet Plateau

The impact of the freeze–thaw process on the active layer is reflected in the changed subsurface flow (SSF) process in cold alpine regions. Identifying sources and pathways of SSF in the freeze–thaw process is critical but difficult, and the related dominant factors and mechanisms are still unknown. In this paper, the effective identification and analysis of SSF are promoted based on field sampling data from the thawing (June) to freezing (September) period of 2022 in the Qinghai Lake basin on the northeastern Qinghai-Tibetan Plateau. By the proposed method with a high sampling frequency and refined sampling spatial scale, the sources and pathways of SSF are clearly identified. The results are as follows: (1) The soil temperature is considered the most fundamental factor affecting the SSF pathways, it influences water infiltration to the deep layer and the effect is extended to the saprolite and weathered bedrock layers. (2) Thawing promotes water to infiltrating into deep layer. 30 cm soil water contributes the most to SSF (2 %–86 %) in the thawing period, while the contribution difference of the water from the 30 cm, 60 cm, and 90 cm layers is small (ranging from 32 %–33 %, 24 %–26 %, and 32 %–35 %, respectively) in the thawed period. (3) Meanwhile, the soil water from different slope positions contribute differently to SSF, and the SSF from deep soil layer is transit in prolong paths and depths. It is caused by the out-of-sync water transit process in the hillslope. With continuing climate warming, we propose that the differences in the water sources of SSF across soil layers may decrease, while the differences in the transit processes of SSF across soil layers may increase.

Effect of vegetation restoration type and topography on soil water storage and infiltration capacity in the Loess Plateau, China

Vegetation restoration effectively mitigates soil erosion and improves soil properties, but in drylands, it can lead to soil water scarcity and disrupt ecological balance. Until now, limited research has examined the combined effects of vegetation restoration type and topography on soil water and infiltration in the Loess Plateau of China. Here, we investigated soil water content (SWC), soil water storage (SWS), soil infiltration rates and related soil properties in typical forestland, shrubland, and grassland across five slope positions on steep slopes, and compared them with cropland. The results indicated that vegetation restoration significantly decreased SWS compared to cropland. Across the entire 0–500 cm depth, reductions were observed at 30.9 %, 33.2 %, and 20.8 % for forestland, shrubland, and grassland, respectively, with forestland and shrubland demonstrating a more pronounced decrease, particularly in deeper soil layers. Shrubland had the lowest SWS on the upper, middle, and top slopes, while forestland showed the lowest SWS on the lower and foot slopes. In terms of infiltration, vegetation restoration generally increased steady infiltration rate but resulted in reduced initial and mean infiltration rates (except for shrubland). Shrubland had the highest infiltration rates, followed by forestland, while grassland had the lowest rates. Soil infiltration rates decreased gradually along the slope, indicating that the impact of vegetation restoration on soil infiltration improvement weakened with lower slope positions. Vegetation restoration type had a stronger direct and total effects on infiltration than slope position. Yet, the indirect influence of slope position through clay content and SWC outweighed that of vegetation restoration type. Our findings highlight the comprehensive assessment of the eco-hydrological effects of vegetation restoration is essential for identifying suitable species and designing optimal spatial distribution, ultimately maximizing the ecological benefits of the restoration. These insights can offer valuable guidance for ecological restoration and land management in fragile dryland ecosystems.

The impact of continuous cultivation of Ganoderma lucidum on soil nutrients, enzyme activity, and fruiting body metabolites

To explore the impacts of continuous Ganoderma lucidum cultivation on soil physicochemical factors, soil enzyme activity, and the metabolome of Ganoderma lucidum fruiting bodies, this study conducted two consecutive years of cultivation on the same plot of land. Soil physicochemical factors and enzyme activity were assessed, alongside non-targeted metabolomic analysis of the Ganoderma lucidum fruiting bodies under continuous cultivation. The findings unveiled that in the surface soil layer (0–15 cm), there was a declining trend in organic matter, ammonium nitrogen, available phosphorus, available potassium, pH, polyphenol oxidase, peroxidase, alkaline phosphatase, and sucrase, whereas nitrate nitrogen, electrical conductivity (EC), and salt content exhibited an upward trend. Conversely, in the deeper soil layer (15–30 cm), organic matter, ammonium nitrogen, available potassium, alkaline phosphatase, and sucrase demonstrated a decreasing trend, while nitrate nitrogen, available phosphorus, pH, EC, salt content, polyphenol oxidase, and soil peroxidase showed an increasing trend. Metabolomic analysis of Ganoderma lucidum fruiting bodies distinguished 64 significantly different metabolites between the GCK and GT groups, with 39 components having markedly higher relative contents in GCK and 25 components having significantly lower relative contents in GCK compared to GT. Moreover, among these metabolites, there were more types with higher contents in the fruiting bodies harvested in the first year (GCK) compared to those harvested in the second year (GT), with pronounced differences. KEGG pathway analysis revealed that GCK exhibited more complex metabolic pathways compared to GT. The metabolites of Ganoderma lucidum fruiting bodies were predominantly influenced by soil physicochemical factors and soil enzyme activity. In the surface soil layer (0–15 cm), the metabolome was significantly affected by soil pH, soil organic matter, available phosphorus, and soil alkaline phosphatase, while in the deeper soil layer (15–30 cm), differences in the Ganoderma lucidum metabolome were more influenced by soil alkaline phosphatase, soil catalase, pH, nitrate nitrogen, and soil sucrase.

Lichen biocrusts contribute to soil microbial biomass carbon in the northern temperate zone: A meta‐analysis

AbstractBiological soil crusts (biocrusts) have crucial ecological functions in dryland ecosystems, yet understanding the variations in soil microbial biomass within biocrusts across diverse ecosystems, climates and soil conditions remains limited. This knowledge gap constrains our understanding of how microbial communities within biocrusts regulate terrestrial carbon and nitrogen cycling. Hence, we conducted a meta‐analysis using 255 paired observations from 42 study sites across the northern temperate ecosystem. The analysis revealed that biocrusts harbour significantly higher soil microbial biomass carbon and nitrogen (SMBC and SMBN, respectively) levels than bare (non‐biocrust) soil across all habitat types. Notably, deeper soil layers (5–10 and &gt;10 cm) accumulated less SMBC and SMBN than biocrust and biocrust–5‐cm soil, revealing that biocrusts influence shallow soil environments. Ecosystem type, soil texture, depth and season emerged as key factors influencing the distribution of SMBC within biocrusts. Of particular interest, lichen biocrusts accumulated the most SMBC compared with other biocrust types. Furthermore, the difference in SMBC between biocrust and non‐biocrust soils was more pronounced in oligotrophic habitats (e.g., desert, grassland, sand and sandy loam soils) than in eutrophic habitats (e.g., forest and loam soils). Random forest analysis confirmed that soil variables affected SMBC accumulation in biocrusts more than climatic factors. Soil organic carbon (SOC), as the primary source of SMBC, could be the most important determinant. Moreover, the disparity between non‐biocrust SMBC and biocrust SMBC increased with increasing mean annual temperature (MAT) or decreasing altitude. These insights underscore the substantial contribution of lichen biocrusts to SMBC and emphasize the need to incorporate this knowledge into regional models for predicting the effects of climate change on soil carbon budgets within biocrust microbiomes in temperate ecosystems of the Northern Hemisphere.

Importance of stemflow to soil water replenishment in a montane forest of Popa Mountain Park, Myanmar

Stemflow (SF), rainwater that reach the ground by flowing down along the branches and trunk, is important in maintaining soil water content (SWC) and recharging groundwater in a forest. This study aims to investigate the importance of SF to soil water replenishment in a montane forest. Measurements of gross rainfall, SF at 9 trees, SWC at two different points for two soil depths and infiltration rates at the two points were carried out in Popa Mountain Park (PMP) in 2019. SF rates in PMP were high ranging from 4.0% to 18.8% of total gross rainfall. Mean SWC near the tree were 18.5% at 5 cm depth and 21.7% at 15 cm depth, respectively, while those outside the canopy area were 11.4% and 9.0%, respectively. SWC near the tree were significantly higher for both soil depths. Similarly, significant higher infiltration rate was found near the tree. Near the tree, infiltration rate exceeded the amounts of individual rain events helped to store more rainwater as SWC in deeper soil layers. In PMP, thus, vegetative cover particularly forested areas are expected to have hydrological advantages in restoring rainwater through a large amount of infiltrated SF into the soil.