Increasing Soil Depth Research Articles

The heterogeneity of Pinus yunnanensis plantation growth was driven by soil microbial characteristics in different slope aspects

The slope aspect is an important environmental factor, which can indirectly change the acceptable solar radiation of forests. However, the mechanism of how this aspect changes the underground ecosystem and thus affects the growth of aboveground trees is not clear. In this study, Pinus yunnanensis plantation was taken as the research object, and the effects of soil and microbial characteristics on tree growth under different slope aspects and soil depths were systematically analyzed. The tree height (H) and ground diameter (GD) on the sunny slope were 7.64% and 8.69% higher than those on the shady slope. The soil pH, alkaline hydrolyzable nitrogen (AHN), available phosphorous (AP), available potassium (AK), total nitrogen (TN), total phosphorous (TP), and total potassium (TK) were significantly different between the different slope aspects. With the increase in soil depth, the content of organic matter (OM), AHN, AP, and AK decreased. There were significant differences in soil microbial diversity and community structure between the different slope aspects, but there was no significant difference among different soil depths. The abundance of Proteobacteria on a sunny slope was lower than that on a shady slope, and the richness of Firmicutes and Planctomycetota was higher than that in a shady slope. With the increase of soil depth, the richness of Proteobacteria increased, and the richness of Firmicutes and Planctomycetota decreased. The structural equation model showed that the influence of soil bacteria and fungi on soil characteristics was much greater than that on tree growth, and the influence of soil characteristics on tree growth was much greater than that of soil microorganisms. The slope aspect caused the difference of soil microorganisms, further affected the soil characteristics and led to the heterogeneity of aboveground forest growth. The insights gleaned from this study hold the potential to inform the formulation of customized management strategies, thereby enhancing resource utilization efficiency and fostering the vitality of forest ecosystems. Furthermore, this research offers theoretical underpinning for the targeted cultivation of coniferous plantations.

Spatiotemporal Dynamics of Fine Root Biomass in Chinese Fir (Cunninghamia lanceolata) Stumps and Their Impacts on Soil Chemical Properties

Stumps are residuals from artificial forest harvesting, persist in forest ecosystems, and have garnered attention for their ecological roles in soil and water conservation, carbon sequestration, and forest regeneration. However, the spatiotemporal dynamics of stump fine root biomass and their impact on soil nutrient cycling remain unclear. This study focuses on the fine roots of Chinese Fir (Cunninghamia lanceolata) stumps generated during the construction of national reserve forests at Xishan State Forest Farm, Linwu County, Hunan Province, from 2014 to 2022. Employing a space-for-time substitution approach, we investigated the spatiotemporal dynamics of fine root biomass (FRB) and its effects on soil chemical properties. The results indicated that the Chinese Fir stump FRB significantly differed with increasing residual time across various soil layers and distances, with an average annual loss rate of 8.40%–9.96%. The living fine root biomass (LFRB) was predominantly concentrated in the 0–20 cm soil layer and decreased with increasing soil depth. Initially, the LFRB was closer to the stumps; however, this proximity effect diminished over time. There were no significant differences in the fine root loss coefficients between layers, within the vertical soil profile with 95% root loss over a time span of 15.1–15.9 years. However, there were horizontal differences, with a 95% root loss over a time span of 13.7–17.0 years. The changes in soil organic matter (SOM) and total nitrogen (STN) content over the study period exhibited a trade-off relationship with the loss of LFRB, with SOM and STN peaking 1 year after the peak of dead fine root biomass (DFRB), suggesting a combined effect of living root exudates and dead root decomposition on SOM and STN enhancement. The trend of LFRB loss was generally inverse to the changes in the soil’s total phosphorus (STP) content, which gradually increased with extended stump retention, indicating that stumps provide a long-term source of phosphorus for the soil. The study also revealed that living fine roots of Chinese Fir stumps can persist in forest soils for a relatively long time and that their biomass dynamics positively affect soil nutrients and carbon storage. These findings provide theoretical support for forest management and suggest that retaining stumps in post-harvest forest management can maintain soil fertility and ecological functions.

Response of the germinable soil seed bank of temperate Leymus chinensis meadows to mowing regimes.

Mowing is a primary practice in temperate L. chinensis meadows, which are severely degraded due to frequent mowing, overgrazing, and other factors, necessitating restoration and sustainable management. The natural recovery of these grasslands hinges on their germinable soil seed banks, which form the basis for future productivity. Thus, germinable soil seed banks are critical for restoring overexploited meadows. In this study, we conducted germination experiments on 135 soil samples from various depths to comprehensively analyze the germinable seed bank under different mowing regimes. The main results were as follows: (1) the germinable soil seed bank density decreased significantly with a mowing event per year (C1), and the number of perennial grass seeds and upper grass seeds also decreased under the mowing event per year; (2) the size of the germinable soil seed bank increased under the other mowing regimes (control area without mowing or grazing, CK; mowing event every 2 years, C2; mowing event every 3 years, C3; and mowing event every six years, C6) relative to that under once-a-year mowing. With increasing soil depth, the number of germinable soil seeds decreased significantly. Most of the seeds in the germinable soil seed banks were distributed in the 0-2 cm soil layer, accounting for approximately 80% of the total, and at depths of 5-10 cm, the number of seeds of upper grasses was greater than that of perennial grasses. (3). During the mowing event each year, the seed bank of germinable soil seeds significantly decreased. Mowing every 2 years provides a one-year interval for natural vegetation growth, allowing for greater retention of seeds in the germinable soil seed bank. Mowing every 6 years significantly reduces the disturbance frequency, providing ample time for plant reproduction and resulting in the accumulation of germinable seeds in the soil.

Trees shape the soil microbiome of a temperate agrosilvopastoral and syntropic agroforestry system

Agroforestry systems are multifunctional land-use systems that promote soil life. Despite their large potential spatio-temporal complexity, the majority of studies that investigated soil organisms in temperate cropland agroforestry systems focused on rather non-complex systems. Here, we investigated the topsoil and subsoil microbiome of two complex and innovative alley cropping systems: an agrosilvopastoral system combining poplar trees, crops, and livestock and a syntropic agroforestry system combining 35 tree and shrub species with forage crops. Increasing soil depth resulted in a decline of bacterial and fungal richness and a community shift towards oligotrophic taxa in both agroforestry systems, which we attribute to resource-deprived conditions in subsoil. At each soil depth, the microbiome of the tree rows was compositionally distinct from the crop rows. We detected a shift towards beneficial microorganisms as well as a decline in putative phytopathogens under the trees as compared to the crop rows. Finally, based on our results on community dissimilarity, we found that compared to an open cropland without trees, spatial heterogeneity introduced by the tree rows in the agrosilvopastoral system translated into a compositionally less homogeneous soil microbiome, highlighting the potential of agroforestry to counteract the homogenization of the soil microbiome through agriculture.

Exploring the multifaceted reason for deficits in soil water within different soil layers in China’s drylands

Soil water regulates the hydrological cycle and provides the water required for vegetation growth in drylands. However, existing studies have rarely investigated the reason for changes in soil water within different layers and compared differences in the contribution of driving factors from spatial and inter-annual perspectives. This study analyzed the dynamics of soil water content (SWC) at shallow (0–28 cm), intermediate (28–100 cm), and deep (100–289 cm) layers. The individual and interactive effects of different environmental factors on the spatial heterogeneity of SWC were investigated using the geographical detector. By selecting evapotranspiration (ET), precipitation, air temperature, land surface temperature (LST), and the Normalized Difference Vegetation Index (NDVI), we determined the influences of these factors on SWC dynamics for each layer as well as their contributions using ridge regression. Meanwhile, we also analyzed the influence of extreme events and lag effects of climatic factors on SWC. The results showed that SWC in each layer primarily exhibited a downward trend. In different layers, all interactive factors (two factors) had stronger effects on the spatial heterogeneity of SWC compared to any individual factor. Precipitation was the largest contributor (25.03±20.66%) to SWC dynamics in shallow layer but its contribution decreased with increasing soil depth. NDVI mainly controlled the SWC in intermediate and deep layers with the largest contribution and exerted a dual effect on SWC. The contributions of air temperature and LST were the smallest. The lagged months of precipitation and air temperature on SWC increased with soil depth. Precipitation extremes with long duration and warm temperature extremes had large contributions and exceeded that of the average climate changes. These findings can provide a deeper insight into soil water dynamics and their environmental factors and scientific guidance for maintaining the hydrological cycle and sustainable development of vegetation in drylands.

Soil Organic Carbon Storage and Stratification in Land Use Types in the Source Area of the Tarim River Basin

Accurate analysis of soil organic carbon (SOC) under different land uses in ecologically fragile arid zones is essential for effective regulatory measures and improvement of ecological quality. This study selected the ecologically fragile Tarim River source area as an example, aiming to quantitatively assess the SOC content, storage, carbon sequestration potential, and stratification ratio (SR) of different ecological land use types. Soil depths from 0–50 cm were determined and analyzed using the K2Cr2O7-H2SO4 oxidation method, the equivalent soil mass method and mathematical statistics. Forest, shrubland, and grassland ecological land types were included. The results show the following: (1) Both SOC content and storage showed a decrease with increasing soil depth. The total SOC content and storage sequence from high to low were natural forest, grassland, and shrubland. (2) There are variations in the SOC sequestration potential among the different ecological land types and shrubland (40.64 Mg C ha−1) > grassland (37.69 Mg C ha−1). (3) The SRs of the SOC in the forest were significantly greater than those in the shrubland and grassland. The different ecological land types had significant impacts on SR2, SR3, and SR4. SR2 could serve as a reliable index for assessing the impact of management practices on soil quality. The study area has a high potential for soil carbon sequestration in the future under these ecological conservation and management measures.

Effect of Tannery Organic Matter on the Migration and Transformation of Chromium in Soil

ABSTRACT Chromium (Cr) contamination is one of the main pollution issues in the soils of tanning industries. Nevertheless, it is unclear how tannery organics affect the movement and transformation of Cr in soil. Column leaching tests were carried out to investigate the impact of various tannery organics, such as phenol, dyes, and surfactants on Cr mobility in tannery soil. The cumulative release of Cr from the soil was less in the presence of tannery organics than that from the non-tannery organics treated group. This suggests that the tannery organics enhanced the fixing of Cr in the soil. Cr was poured from the top of the soil column in the form of Cr (III) solution for leaching, and the concentration of Cr decreased with the increase of soil depth regardless of the presence of tannery organic matter. After leaching, the residual Cr concentration in the soil was 59%−78% of the total Cr concentration. The potential risk of Cr in the soil/groundwater system decreased in the presence of the tannery organics, which decreased the bioavailability of Cr and increased the percentage of Cr in residual state. Understanding the relationship between Cr migration and tannery organics in soil is helpful for soil environment risk assessment of tannery site.

Enhanced Carbon Sequestration and Microbial Activities Under Apple‐Based Agroforestry Systems in Kullu Valley of Himachal Pradesh

ABSTRACTBackgroundIntegrating fruit trees is among the promising agroforestry technologies. Intercropping of fruit trees with remunerative crops, particularly vegetables, could generate higher income for farmers.AimThe present study involves the assessment of apple‐based agroforestry systems integrated with various agricultural crops such as black gram, capsicum, tomato, and brinjal and evaluated the effect of integrated farming on soil properties, microbial biomass, and enzyme activities.MethodsThe experiment was conducted in Randomized Block Design by considering sole apple, sole tomato, sole brinjal, sole capsicum, sole black gram, apple + tomato, apple + brinjal, apple + capsicum, and apple + black gram as treatments.ResultsThe study revealed the performance of the agroforestry system where apple and tomato in combination perform better than others and sole cropping. The competition for moisture, nutrients, and other limiting resources in agroforestry system where apple trees are grown in combination with brinjal, capsicum, and black gram resulted in poor plant's growth and yield. This combination of crops also significantly affected the organic carbon, porosity, bulk, and particle densities. The available N, P, and K contents decreased with the increased soil depth. It was observed that microbial biomass in terms of carbon (Cmic), nitrogen (Nmic), and phosphorus (Pmic) was higher where tomato was grown in apple‐based agroforestry systems than in sole cropping. Higher enzymatic activities for acid and alkaline phosphatase, catalase, and dehydrogenase were recorded in agroforestry system where tomatoes were grown in the presence of apple trees.ConclusionsThe results reported that a combination of apple and tomato is the most successful system as tomato crop performs better under the apple tree canopy, possibly due to the favorable microenvironment and tree‐crop compatibility.

Assessing the impact of multi-source environmental variables on soil organic carbon in different land use types of China using an interpretable high-precision machine learning method

To explore the impact of environmental factors on soil organic carbon (SOC) with machine learning (ML) model is of great significance for mitigating climate change and soil carbon sequestration and emission reduction. However, the traditional ML model is limited by the hyperparameter adjustment of artificially trial-and-error experimentation and the inexplicability of fitting process, and the precision and performance of ML model cannot be fully utilized. For the end, this study developed a tree-structured Parzen estimator-extreme gradient boosting (TPE-XGBoost) method based on SHapley additive explanations (SHAP) analysis to analyze the response of climate, human activities, soil properties and terrain for SOC (0-200cm) in different land use types of China. The results of descriptive statistics described the order of SOC content: forest land > grassland > cultivated land > unused land. With the increase of soil depth, the SOC content of all land types decreased continuously, and the values indicate a left-skewed non-normal distribution. The fitting accuracy (R2) of TPE-XGBoost model for SOC content was greater than 0.8. At the depth of 0-5cm, the prediction accuracy of cultivated land (R2 = 0.96), grassland (R2 = 0.93), forest land (R2 = 0.95) and unused land (R2 = 0.95) was the highest. The result of SHAP analysis showed that the factors that contributed the most to the fitting accuracy of cultivated land, grassland, forest land and unused land in all depths were temperature, soil pH, temperature and elevation. From surface to deep soil, the mean SHAP value showed a downward trend, indicating that the driving force of environmental factors on the content of SOC gradually weakened. The individual explanations of the variance partitioning (VP) analysis of climate, terrain, and soil property for cultivated land (0-200cm), forest land (30-60cm), and unused land (0-200cm) was as high as 0.32, 0.17, and 0.16, respectively, which indicated that these environmental factors had a high response to SOC content. It is found that the appropriate temperature not only promotes plant roots to obtain nutrients, but also interacts with soil pH on microorganisms, thereby increasing the SOC content. The results confirm that the TPE-XGBoost model based on SHAP analysis can reliably explain the nonlinear driving effect of environmental factors on the SOC, which provides credible decision support for accounting carbon budget and carbon sequestration in large-scale regions.

Distribution and key influential factors of comammox in drained and waterlogged soils of zoige plateau peatland

Peatlands are important carbon and nitrogen reservoirs, playing crucial roles in nitrogen cycling. During microbially-driven nitrogen cycling, nitrous oxide (N2O, 298 times global warming potential of CO2) can be emitted, exacerbating global warming. Complete ammonia-oxidizing bacteria (comammox), a newly discovered group of prokaryotes, can independently oxidize ammonia directly to nitrate, bypassing the nitrite stage, and thereby reducing N2O production associated with the traditional two-step nitrification process. However, information on comammox distribution and its key influential factors in plateau peatlands remains scarce. Thus, this study chose Zoige plateau peatland in China to collect soil samples from different soil types (drained and waterlogged), across different seasons (non-growing and growing), and at various depth (0–100 cm) to assess comammox abundance and community composition. Additionally, soil properties were analyzed and correlated with comammox abundance and community composition to identify the key factors affecting comammox distribution. Comammox abundance varied significantly across soil types, depth, and sampling seasons. Waterlogged soils demonstrated higher comammox abundance than drained soils. In waterlogged soils, comammox abundance showed higher during growing season than non-growing season, while the opposite trend was observed in drained soils. Regardless of soil types, comammox abundance decreased with increasing soil depth. In soils of Zoige plateau peatland, comammox clades A.1, A.2, A.3 and B.1 were identified, with clade B.1 dominating the comammox community. Both Nitrospira sp. CG24A (clade B.1) and Candidatus Nitrospira nitrificans (clade A.1) showed great seasonal variations. Soil properties, including moisture, pH, carbon, and nutrients, collectively influenced comammox abundance and diversity. Among these factors, NH4+-N was the main factor affecting comammox abundance, while moisture primarily drove community distribution. These findings provide valuable insights into comammox distribution, enhancing our understanding of its potential role in mitigating N2O emissions and thus nitrogen cycling in plateau peatland soils.

Impact of Grazing Tibetan Pigs on Soil Quality

Pig manure, as an organic fertilizer, can significantly affect soil nutrient content, pH, and electrical conductivity. Moreover, the accumulation of heavy metals in pig manure and their potential ecological risks are also important concerns in soil management. Additionally, grazing systems may influence soil health and ecological balance by altering the soil microbial community structure. Therefore, this study investigates the impact of grazing Tibetan pigs on soil quality, focusing on the physicochemical properties, heavy metal accumulation, and microbial diversity. In the surface soil after grazing (GS0), pH, EC, AP, and AK were significantly higher than before grazing (NS0) (p < 0.05), while AN showed no significant difference. In the 10 cm soil layer, pH, EC, AK, and AN in GS10 were significantly higher than in NS10 (p < 0.05), whereas AP was significantly lower (p < 0.05). At the 20 cm depth, pH, EC, AP, and AK in GS20 were significantly higher than in NS20 (p < 0.05), but AN was significantly lower (p < 0.05). Overall, AN, AP, and AK decreased with increasing soil depth, while pH and EC showed no significant changes between the 10 cm and 20 cm layers (p > 0.05). In GS0 soil, the contents of Cd(II) and Zn(II) were significantly lower than those in NS0 (p < 0.05), while Pb(II) content was significantly higher (p < 0.05). There were no significant differences in Cu(II), Ni(II), Cr(VI), As(V), and Hg(II) (p > 0.05). In GS10 soil, Ni and Pb(II) contents were higher, whereas Cu(II), Zn(II), and Hg(II) contents were lower. In GS20 soil, Pb(II) and Cr(VI) contents were higher, while Cu(II) and Zn(II) contents were lower. Overall, GS had consistently lower Cd(II), Cu(II), Zn(II), and Hg(II) contents at all depths compared to NS, while Pb(II) and Cr(VI) contents were higher, showing depth-related variation trends, possibly due to plant absorption and heavy metal leaching. Probiotics such as Firmicutes, Bacteroidetes, and Acinetobacter increased significantly in soil, resulting in changes in the soil bacterial community.

Variation in Soil Moisture Content and Soil Organic Carbon in Different Agroforestry Practices in Moshi Rural District, Northern Tanzania

Agroforestry has been widely practiced in the northern highlands of Tanzania because of its prominent effects in reducing soil losses, maintaining soil moisture contents (SMCs), and improving land-use efficiency and farmer’s livelihood. We tested the hypothesis that variations of soil moisture contents in 0-20 cm and 20-40 cm depths from various agroforestry Practices differ significantly in intensified small-scale agroforestry systems. The relationship between SMCs and soil organic carbon was also evaluated. Soil samples were collected from 10 x 10 m2 plot in three points along the diagonal of the quadrat using soil auger. SMCs were determined by gravimetric method and expressed as SMC%. SOC was determined by Walkley and Black method and expressed as SOC %. The variation in SMCs% among the different agroforestry Practices were statistically determined by ANOVA in R software while the correlation between SMCs and SOC were statistically determined by Pearson product-moment analysis. Variation of SMCs was statistically insignificant (p>0.05) among surveyed sites. SMCs increased significantly (p<0.05) with increasing soil depth from 0-40 cm depth in all agroforestry Practices except in the mixed intercropping agroforestry practice (MAP). At 0-20 cm and 20-40 cm, SMCs differed significantly among agroforestry Practices (P = 0.071) and (P = 0.003), respectively. Coffee Intercropping Agroforestry Practice (CIAP) had higher (P<0.05) SMCs at 0-20 cm depth compared to BAP and MWPAP. But, at 20-40 cm depth, soil moisture contents in CIAP differed significantly (P<0.05) with SMCs all AFPs. SMCs showed a positively significant (P<0.05) relationship with SOC within 0-20 cm and 20-40 cm depths. The current study confirms that different agroforestry practices have different influence on the amount and vertical distribution of soil moisture. Therefore, management practices in agroforestry systems should aim to encourage the use of practices which ensure a stable amount of moisture contents in the soil

Investigating the Effects of Elevation on Microbial Communities and Soil Properties at Fanjing Mountain, China

Elevation is one of the most influential factors affecting soil characteristics and microbial communities in forest ecosystems. Nevertheless, there is no consensus on how soil characteristics, soil microbials, and their relationships response to the elevation of the mountain ecosystem. We investigated the soil physicochemical characteristics, the activity of soil enzymes, and the microbial community at elevational sites from 600 to 2400 m above sea level (asl) in the western slopes of the Fanjing Mountain ecosystem, China. The soil microbial communities were determined by high throughput 16S rRNA and ITS amplicon sequencing. The results demonstrated that soil total nitrogen (TN) showed a slight decrease, whereas total phosphorus (TP) and total potassium (TK) gradually tended to increase with increasing elevation. The large macroaggregates (>2 mm) accounted for the largest proportion of the aggregate fraction (66.23%–76.13%) in the 0–10 cm soil layer with elevation. The average values of the soil electrical conductivity (EC), soil organic carbon (SOC), and cation exchange capacity (CEC) concentration in the 0–60 cm layer undulated with increasing elevation, and the highest values were observed at 1500–1800 m asl and 1800–2100 m asl, respectively. The activities of soil urease, sucrase, acid phosphatase, and catalase clearly differed (p < 0.05) with increasing elevation, and the minimum values were found at 2100–2400 m asl. Interesting, with increasing soil depth, the values of these factors tended to decrease, indicating surface aggregation. In addition, the soil microbial (bacterial and fungal) community diversity exhibited a single-peak pattern with elevation. Our results also revealed that the soil bacterial and fungal communities varied significantly at different elevation sites. The bacterial communities were dominated by the phyla Acidobacteria, Pseudomonadota, and Chloroflexi, and the phyla Basidiomycota and Ascomycota dominated the fungal communities. The Pearson and redundancy analyses revealed that the SOC, TP, four soil enzymes, and soil aggregates were significant factors influencing the soil microbial community. In conclusion, soil properties and enzyme activities jointly explained the elevational pattern of the soil microbial community in the Fanjing Mountain. The results of this study provide insights into the influence of elevation on soil characteristics, microbial communities, and their relationships in the Fanjing Mountain ecosystem.

Grazing exclusion promotes soil organic carbon accumulation in Tibetan grasslands with lower temperatures

BackgroundGrazing exclusion is a practical approach to restore vegetation in degraded grasslands and enhance soil organic carbon (SOC) sequestration. However, the dynamics and drivers of SOC in grasslands after grazing exclusion have not been well documented, especially in ecosystems with cold climates.MethodsHere, we established 14 paired treatments (grazing exclusion vs. free-grazing) along a 600-km transect in the northeastern zone of the Qinghai-Tibet Plateau. After six years, we analyzed vegetation biomass dynamics and measured the soil physicochemical properties and organic C concentration across three depths (0–10, 10–20, and 20–30 cm).ResultsGrazing exclusion significantly increased above- and belowground biomass (139.85% and 43.30%, respectively), pH (1.38%), total phosphorus (3.29%), nitrate nitrogen (18.03%), and ammonium nitrogen (17.81%), but significantly decreased soil bulk density (2.43%) and clay content (10.49%), particularly in 0–30 cm. Specifically, SOC concentrations positively responded to grazing exclusion (0–10 cm) in 9 of the 14 sites evaluated. The effects of grazing exclusion on SOC concentrations were significantly higher in areas with a mean annual temperature (MAT) below 0 °C compared to those in sites with a high MAT (> 0 °C). The SOC concentrations significantly correlated with the mean annual precipitation (MAP) in both treatments, but these correlations diminished with increasing soil depth. Ridge regression analysis showed that soil chemical properties (e.g., total nitrogen and phosphorus) positively influenced SOC accumulation, while MAT negatively influenced it after grazing exclusion. Path analysis further revealed that MAT indirectly regulated SOC dynamics via soil chemical properties.ConclusionsOur study highlights that grazing exclusion results in an asynchronous SOC and plant biomass accumulation and may be more beneficial for SOC sequestration in Qinghai-Tibet Plateau grasslands with lower temperatures. Also, humid climates promote SOC concentration in alpine grasslands. These results could help develop management practices and policies that promote sustainable grassland management.

Integrating multi-source remote sensing and machine learning for root-zone soil moisture and yield prediction of winter oilseed rape (Brassica napus L.): A new perspective from the temperature-vegetation index feature space

Accurately assessing root-zone soil moisture is crucial for precision irrigation, as it directly influences crop yield. The Temperature-Vegetation Index (Ts-VI) Feature Space, which combines land surface temperature (Ts) and vegetation index (VI), is widely used to evaluate root-zone soil moisture in vegetated areas. However, its effectiveness in estimating crop yield remains unclear. Therefore, the objectives of this study are: (1) to collect multispectral and thermal infrared remote sensing data from a two-year (2021–2023) field experiment on winter oilseed rape (Brassica napus L.), and to optimize and evaluate the fitting methods of the dry and wet edges of the Ts-VI feature space based on the selected vegetation indices; (2) to analyze the spatiotemporal patterns of the Temperature Vegetation Dryness Index (TVDI) derived from the optimized Ts-VI feature space and estimate root-zone soil moisture (SM) and crop yield; and (3) to precisely invert the SM and yield of winter oilseed rape in the 0–60 cm root-zone using three machine learning algorithms—Support Vector Regression (SVR), Extreme Gradient Boosting Regression (XGBR), and Random Forest Regression (RFR)—based on the optimized TVDI. Results indicate that, among the various fitting methods, the polynomial fitting method shows the best performance. The performance of the root-zone soil moisture prediction models across different growth stages follows the order of budding stage > seedling stage > flowering stage, and with the increase of soil depth, the performance of the model gradually deteriorates.In the yield inversion of winter oilseed rape, TVDI effectively predicts yield, with the coefficient of determination (R2) ranging from 0.430 to 0.480 and RMSE ranging from 213.399 to 267.212 kg ha−1 during the seedling stage, R2 ranging from 0.640 to 0.747 and RMSE ranging from 110.712 to 178.133 kg ha−1 during the budding stage, and R2 ranging from 0.680 to 0.773 and RMSE ranging from 83.815 to 147.301 kg ha−1 during the flowering stage. The flowering stage effectively reflects crop yield trends and allows for accurate yield prediction of winter oilseed rape up to two months in advance. A comparison of the modeling results from XGBR, SVR, and RFR shows that XGBR provides the best fit for both root-zone soil moisture and yield predictions. Compared to linear regression models, the three machine learning models significantly improve accuracy and fit, providing more precise evaluations of root-zone soil moisture and yield. In addition, through the comparison and verification of this method in other regions, it shows that the results also have certain reference value. The combination of the Ts-VI feature space and machine learning algorithms not only enables precise monitoring of root-zone soil moisture conditions but also predicts future crop yield trends, offering valuable insights for water resource management and irrigation decision-making in precision agriculture.

Soil Physicochemical Properties and Carbon Storage Reserve Distribution Characteristics of Plantation Restoration in a Coal Mining Area

The Bulianta Coal Mine is among the problematic coal mining areas in China that is still creating environmental damage, especially associated with soil destruction. Therefore, a scientific investigation was conducted to establish a scientific basis for evaluating the impact of planted forest on soil physical and chemical properties, as well as the ecological benefits following 15 years of vegetation restoration in the area. The soil physicochemical characteristics and distribution of organic carbon storage in the 0–80 cm layer soils of Pinus sylvestris forests, Prunus sibirica forests, and Hippophae rhamnoides forests restored after 5, 10, and 15 years were investigated. The immersion method was used to determine soil porosity and density followed by the determination of soil indicators, and a statistical ANOVA test was applied to examine the differential effects of different vegetation types and restoration years on soil properties. The results clearly demonstrated the following: (1) The recovery of vegetation was achieved after a period of 15 years, with the average bulk density of the 0–80 cm soil layer as follows: P. sylvestris forest (1.513 g·cm−3) > P. sibirica forest (1.272 g·cm−3) > H. rhamnoides forest (1.224 g·cm−3), and the differences among different forest types were statistically significant (p < 0.05). (2) In planted forests, soil nutrients were predominantly concentrated in the 0–20 cm layer, while soil carbon storage exhibited a decline with an increasing soil depth. (3) The soil carbon storage across the three forest types was as follows: P. sylvestris forest (45.42 t·hm−2) > P. sibirica forest (44.56 t·hm−2) > H. rhamnoides forest (41.87 t·hm−2). In summary, during the ecological vegetation restoration process in the Bulianta Core Mine, both P. sylvestris forest and P. sibirica forest exhibit superior carbon storage capacities compared to H. rhamnoides forest, as well as more effective soil improvement outcomes.

Soil quality assessment and its response to water flow connectivity in different vegetation restoration types, eastern China

Vegetation restoration is the most widely used forest management practice for degraded soils, but the responses of soil quality in different vegetation restoration types may vary. In addition, the relationship between water flow paths connection and soil quality needs to be further explored. In this study, the soil quality index (SQI) and the index of water flow connectivity (IWFC) in the six water flow patterns (PFP, SSB, WSB, CPS, CPW, and CSW) were explored at three forest stands (oak, pine, and bamboo forests) with 50 years for enclosure. The results showed that the bamboo forest stand had the best soil quality as a whole (0.534 ± 0.135), followed by pine (0.530 ± 0.180) and oak forest stands (0.435 ± 0.205). The IWFC in PFP, CPS and CPW water flow patterns decreased gradually with increasing soil depth, while in SSB, WSB and CSB water flow patterns, the IWFC increased at first and then decreased. Finally, the IWFC in the CPW water flow pattern showed the largest positive correlation with the SQI (P < 0.05). The IWFC in the CPW water flow pattern driven by soil physical properties could mainly control the changes in the SQI indirectly (average IE = 0.825) by influencing soil nutrient (average IE = 0.447) and biological (average IE = 0.485) properties, while its direct effects could be ignored (average DE = −0.074), which demonstrated that the joint effects of preferential flow paths and weak stream buffer zones can dramatically reflect the changes in soil quality. The better soil improvement effect of bamboo and pine forest stands compared to the oak forest stand should be given more consideration. This study provided new insights for the assessment of the relationship between soil hydrology and soil quality.

Geochemical Characteristics and Environmental Risks of Cu in the Soil of A Sloping Vineyard (Phu Tho Province, Vietnam)

In the vineyards, the intensive use of cupric fungicides and fertilizers has resulted in Cu enrichment in the soils. Specifically, in sloping vineyards, the mobility of Cu can contribute to intensify the environmental risks. The research on geochemical characteristics of Cu is a key solution to explore the distribution of Cu in different geochemical fractions and understand the mobility and toxicity of this element in the environment. In this study, we aim to investigate the geochemical properties of Cu in the vineyard topsoil (0-20 cm) and subsoil (20-40-60 cm), using the improved three-step sequential extraction procedure developed by the Commission of the European Communities Bureau of Reference (BCR). In addition, the environmental risk is calculated by the environmental risk code (RAC) based on the percentage of Cu in the acid-soluble fraction. The results reveal that the mobility of Cu in the acid-soluble fraction (F1) and reducible fraction (Cu associated with the iron and manganese oxyhydroxides) (F2) tends to decrease with increasing soil depth. The major portion of Cu mostly exists in the strong bond with silicate clays (F4), accounting for 84% of total Cu content on average. Contrarily, the minor propotion of Cu associates with soil organic matter (F3) (3% on average). On the other hand, the content and proportion of Cu in the soil fractions are largerly influenced by basic soil properties (organic matter contents and fine soil particles). In addition, under the impact of soil erosion, higher percentages of F1 and F2 fractions of Cu are observed in the surface soil layers at the top of the hill compared to those at the backslope of the hill. The mean calculated RAC of 10.66%, 5.76%, and 5.38% for the 0-20 cm, 20-40 cm, and 40-60 cm soil layers, respectively, demonstrate a low risk to medium environmental risk level in the studied vineyard. Although an overall low risk level is observed for Cu in the studied vineyard soil, the deposition of Cu originating from repeated Cu-based pesticides and erosion is of particular concern in the vineyard soils.

STABLE CARBON ISOTOPE FOR EVALUATING SOIL ORGANIC CARBON BETWEEN RICE-CORN ROTATION AND CORN MONOCROPPING

Soil organic carbon (SOC) is a significant component that plays an important role in soil fertility and crop sustainable production. This study investigated SOC in soil profiles of rice-corn rotation and corn monocropping using a stable carbon isotope of SOC (δ13CSOC) technique. The soil samples were collected from two plots of rice-corn rotation and corn monocropping fields. Soil sampling was conducted in Tak province, involving the collection of 25 soil cores per plot down to a depth of 50 cm. Each soil profile was further segmented into ten depth layers: 0-5 cm, 5-10 cm, 10-15 cm, 15-20 cm, 20-25 cm, 25-30, 30-35, 35-40, 40-45, and 45-50 cm. The collected soil samples were then subjected to air drying, pulverization, and sieving through a 200-mesh sieve. The δ13CSOC in rice-corn rotation ranged from -28.41‰ to -23.72‰ while corn monocropping was -24.59‰ to -15.83‰. The results revealed that the values of δ13CSOC for each soil profile gradually increased with soil depth. Since δ13CSOC levels were negatively correlated to SOC. Therefore, SOC decreased with increasing soil depth in both the rice-corn and corn fields. However, significantly higher SOC contents were observed in rice-corn rotation rather than in corn monocropping fields (p &lt; 0.05). SOC contents were higher in soil with rice straw retention than without rice residues. The rotation of rice-corn practice could potentially retain organic carbon in soil better than corn monocropping.

Altitude, Land Use and Soil Depth Effects on Earthworm Density and its Relationship to Soil Properties in an On-Farm Study

Abstract Purpose Earthworms play a critical role in soil ecosystem functions through the cycling of organic matter and nutrients. However, some land uses or environmental conditions are more favorable habitats for them than others. Thus, the objectives of this study were to evaluate the prevalence of earthworm density and its relationship to land uses and soil properties. Methods The study was conducted in three districts (Wangdue Phodrang, Chhukha and Dagana) in Bhutan in three land uses (organic fields - OrgF, conventional fields - ConF and natural vegetation - NatV) under three altitudes (high-, mid- and low-altitudes) and three soil depths. Results Overall, earthworm density at high-altitude was significantly (P &lt; 0.001) higher than that at mid- and low-altitude sites. Further, across altitudes and soil depths, OrgF sites had a significantly (P &lt; 0.001) higher earthworm density (120 earthworms m− 2) compared to that in the NatV (56 earthworms m− 2) and ConF (43 earthworms m− 2) sites, and the density decreased significantly (P &lt; 0.001) and successively with the increase in soil depth. The coefficient of determination (R2 ≥ 0.51; P &lt; 0.001) showed a positive and moderate relationship between the earthworm density with soil organic C and total N in OrgF sites, but the relationship was weak (R2 ≤ 0.22) in the ConF or none in the NatV sites. Conclusions Substituting chemical fertilizers with organic manures could increase earthworm density by enhancing soil health through the cycling of organic materials and nutrients in the soil. The findings demonstrate empirical evidence for earthworm prevalence in different land use types across altitudinal gradients and provide valuable decision-making insights to land users and policymakers alike.