Depth Of Soil Layer Research Articles

Dynamic characteristics of near-surface spontaneous combustion gas flux and its response to meteorological and soil factors in coal fire area

Accurate identification of the early stages of coal-fire combustion is important for effectively controlling the spread of coal fires. CO2 and CO, as characteristic gases in the early stage of coal fire combustion, can be effectively monitored by in-situ monitoring near the surface. However, in the previous in-situ monitoring methods, the influence of surface meteorological and soil factors on the release law of characteristic gases is often ignored. Therefore, this paper considers the complexity of the geological conditions in the coal fire area, a system, and equipment for obtaining the near-surface CO2 and CO variation laws in the early stage of coal fire combustion proposed by the concentration gradient method (CGM). The system and equipment realize the simultaneous online coupling of multi-area and multi-parameter data and conduct field investigations on the Wuda coal fire area. The results show that in the early stage of coal combustion, the change patterns of CO2 and CO concentrations in different regions are anomalous, and the CO2 concentration was higher than the CO concentration. The CO2 and CO concentrations in shallow soil increased with the increase of soil depth, and compared with other areas, the CO2 and CO concentration was the highest. The shallow soil and CO2 were identified as the key areas and characteristic gases for identifying the early stage of coal-fire combustion. The CO2 flux (CF) of different shallow soil depths decreased with increased soil layer depth. Variation of soil-surface CO2 flux (S-SCF) estimated by flux extrapolation method (FLEM). The change of S-SCF is controlled by meteorological and soil factors, and there is a certain connection between it and the “respiration phenomenon” in the fissure area. Thus, this study provides a theoretical basis for effectively identifying the early stages of coal-fire combustion.

Irrigation-facilitated low-density polyethylene microplastic vertical transport along soil profile: An empirical model developed by column experiment

The emerging issue of microplastic pollution of agricultural soils derives from the intensive utilization of plastic mulching film. Although surface runoff may transport microplastic off-site, infiltration may also facilitate microplastic transport from surface soil to deeper depths. Microplastic comprises a relatively new category of soil contaminants, whose transport in the soil has not yet been widely studied. In this study, we investigated microplastic transport from contaminated surface soil (50 g kg-1) driven by irrigation, from permanent wilting point to saturation, and developed an empirical model to characterize the resulting accumulation of microplastic along soil profile. A soil column experiment was conducted under various treatments: the control, 1, 2 and 4 runs of irrigation. Soil samples were collected from inside and outside of soil cracks (if present) in each soil layer (0–2 cm (source layer), 2–5 cm, 5–10 cm, 10–20 cm, 20–30 cm, 30–40 cm, 40–50 cm). The results showed that with increasing irrigation runs, microplastic in the source soil layer decreased, while microplastic contents in deeper soil depths increased significantly (p < 0.05), varying from 7.03 g kg-1 in 2–5 cm to 0.29 g kg-1 in 40–50 cm soil. The microplastic content detected in soil cracks was 1.3–17.8 times higher than that detected in the soil matrix at similar depths, indicating that the transported microplastic is prone to be enriched in soil cracks. In addition, the total amount of transported microplastic increased 1.5 times after four irrigation runs, and the variations were significantly observed especially at deeper soil depths. Based on correlation analyses, data-fitted empirical models that relate cumulative microplastic to the depth of soil layer and irrigation runs indicate that irrigation-facilitated microplastic transport could be well-characterized (R2 >0.92). Further research is needed to develop an physical-based model in order to assess microplastic migration risks driven by irrigation and other agricultural management practices.

THE EFFECT OF ECOLOGICAL FACTORS ON GROWTH OF Sterculia foetida L. IN BUON DON AND EA SUP DISTRICTS, DAK LAK PROVINCE

Accurate and reliable assessment of site suitability for the growth of selected plant species is critical for afforestation projects and programs to improve rural livelihoods. This research examines the relationship between growth of Sterculia foetida L. and six ecological factors in Buon Don and Ea Sup districts, Dak Lak Province. The purpose of the research is to predict the growth in average height and trunk diameter of the trees using ecological factors that are easy to measure and observe. These include topography (slope) and soil characteristics (clay ratio, depth of soil layer, surface and subsurface rock concentrations, and agglomeration ratio). The ecological factors were evaluated by multivariable regression analysis of growth data from 31 experimental plots, 16 in Buon Don district and 15 in Ea Sup district. The results show that four of the six factors affect average growth in tree height and that five factors affect average trunk diameter growth. The findings are of practical value for households and agricultural extension officers to consider before planting Sterculia foetida L. in the two areas.

Effects of straw mulching combined with nitrogen application on soil organic matter content and atrazine digestion

To explore the response of atrazine (AT) degradation rate, soil organic matter (SOM) distribution and the relationship between them to straw mulching and nitrogen application, field experiments were conducted to study the distribution of SOM content and AT degradation rate under different straw returning modes combined with nitrogen fertilization in 2 years in Hetao Irrigation District. No (N0), low (NL), medium (NM), and high (NH) levels of N fertilization were incorporated into the soil combined with the surface coverage straw (Treatment BN0, BNL, BNM, BNH, respectively) and the deeply buried straw (Treatment SN0, SNL, SNM, SNH, respectively). The traditional cultivation was used as a control treatment (Treatment CK). The results showed that SOM content of Treatment B was accumulated in 0~20 cm soil layer. The largest SOM content of Treatments B in 0~20 cm soil layer was found in BNH treatment, with an average increase of 14.2% and 24.1% significantly when compared with those in CK and SNH (P < 0.05), respectively. The SOM content of Treatments B increased with the increase of nitrogen application and decreased with the deepening of soil depth. The SOM content of Treatment S was accumulated in the soil layer (20~40 cm and 40~60 cm) near the inter-layer. With the increase of nitrogen application and depth of soil layer, the SOM content increased firstly and then decreased. SNM had the largest SOM content in the soil layer of 20~40 cm and 40~60 cm, with an average increase of 82.6% and 67.7% when compared with Treatment CK (P < 0.05). In the soil layer over 60 cm, there was no significant difference in SOM content of different straw returning methods under the same nitrogen level (P > 0.05). Straw returning methods and nitrogen application level significantly affected AT digestion rate and digestion half-life, with significant differences among treatments (P < 0.05). It found that treatment SNM had the highest digestion rate and the shortest half-life of AT. Compared with Treatment CK, the digestion rate of Treatment SNM was increased by 5.3% on average, and the half-life was shortened by 3.9 days on average. Single regression and stepwise regression analysis of the half-life of AT degradation and SOM content in different soil layers (0~20 cm and 20~40 cm) showed that the degradation of AT was greatly affected by SOM content of 20~40 cm soil layer. Based on the comprehensive analysis, the effect of straw deep burial combined with medium nitrogen application rate (Treatment SNM) was best, which could achieve the goal of increasing SOM content and shortening the half-life of AT digestion. The research provided a technical support for straw resource utilization, alleviated AT pollution and improved farmland ecological environment in Hetao Irrigated District.

Changes in Cu accumulation and fractionation along soil depth in acid soils of vineyards and abandoned vineyards (now forests)

This study investigated changes in copper accumulation and fractionation based on the depth of soils obtained from active and abandoned vineyards. Soil samples were collected at different depths in three areas with active and abandoned vineyards, and the concentrations of total copper and copper fractions were measured in these soil samples. Results revealed that in active vineyards, total copper accumulation was the highest in the first layer of soil (depth = 0–2 cm), with concentrations (193–892 mg kg−1) considerably higher than those in the deepest soil layer (depth = 40–50 cm; concentration = 63–71 mg kg−1). This accumulation was significantly correlated with the total carbon concentration in the soil. However, the total copper concentration in abandoned vineyards (84–374 mg kg−1) was the highest in the subsurface layers (depth = 10–15 cm) and was not significantly correlated with the total carbon content. Moreover, the percentage of available copper was lower in abandoned vineyards than in active vineyards. In terms of copper fractionation, the main fraction in active vineyard soil was copper bound to organic matter, whereas the main fraction in abandoned vineyard soil was residual copper. Therefore, vineyard abandonment and its transformation into forest changed the distribution and fractionation of copper based on soil depth, thus decreasing the amount of available copper and improving the soil quality, which could enable new ecosystems.

Soil depth determine the ecological stoichiometry of soil aggregates after returning ancient rice terraces to forest

Soil carbon-nitrogen-phosphorus (CNP) ecological stoichiometry is an effective means of reflecting soil nutrient status, transformations, and limitations, but the effect of returning ancient rice terraces to forest on soil CNP stoichiometry is still unclear at the aggregate scale in the subtropical hilly areas of southern China. This study explored how the CNP content and stoichiometry of soil water-stable aggregates responded after returning ancient rice terraces to forest in the soil layer depth of 0–60 cm in subtropical hilly areas. The results showed that the stability, soil organic carbon (SOC), total nitrogen (TN), C/P, and N/P ratios of soil aggregates decreased significantly with soil depth in ancient rice terraces, Chinese fir (Cunninghamia lanceolata), and moso bamboo (Phyllostachys pubescens). The proportion of macroaggregates decreased gradually and the proportion of microaggregates increased significantly after the soil depth increased. Returning ancient rice terraces to Chinese fir was more conducive to increasing the SOC, TN, C/P, and N/P ratios of soil aggregates, which may be related to plant litter biomass. Eta squared analysis showed that soil depth had a greater impact on soil aggregate stability (34 %, 38 %, and 46 %), CNP content (34 %–45 %), and stoichiometry (34 %–57 %) than land use types and their interactions. These findings indicated that returning ancient rice terraces to Chinese fir and moso bamboo can significantly alter soil water-stable aggregate stability, CNP content, and stoichiometry, and soil depth plays an extremely important role in changing them. Future research should focus on the ecological impacts of soil depth on agroforestry ecosystems.

Straw Strip Mulching Increased Soil Organic Carbon Components of a Wheat Field in Dry Farming Regions of the Loess Plateau

To explore the response of soil organic carbon (SOC) and carbon components to surface coverage in wheat fields in semi-arid rainfed regions, a two-year field experiment was conducted under three treatments: straw strip mulching (SM), transparent plastic film mulching (PM) and no mulching (CK). We researched the dynamic feature of soil organic carbon (SOC) and its components at different growth stages of winter wheat under different mulching methods, including microbial biomass carbon (MBC), dissolved organic carbon (DOC), mineralizable carbon (PCM) and easily oxidized carbon (EOC). The results showed that SOC and its components in different soil layers decreased with an increase of soil layer depth. Compared with CK, the SM treatment increased SOC in the 0–40 cm soil layer by 2.83–8.92%, MBC by 12.09–18.40%, DOC by 3.73–9.79%, PCM by 4.82–12.48% and EOC by 6.01–11.68% during the different periods, and an overall increase was greater in the 0–20 cm soil layer than in the 20–40 cm soil layer. The impact of PM on SOC was less significant compared with CK; MBC and PCM had an overall positive effect, and DOC and EOC behaved differently from year to year. In conclusion, SM can improve SOC and its components content in dryland of northwest China, which is conducive to the sustainable management and efficient utilization of maize straw resources and has significant ecological benefits.

Mulching broad ridges with a woven polypropylene fabric increases the growth and yield of young pear trees ‘Yuluxiang’ in the North China Plain

Unlike traditional ridging, mulching broad ridges with a woven polypropylene fabric (WPF) can reduce soil evaporation during the drought season and avoid long saturation time in the root zone of pear trees during the rainy season. In this study, field experiments were conducted from 2017 to 2020 in a pear orchard in the North China Plain to investigate the effects of mulching broad ridges (0.3 m in height and 2 m in width) with WPF on soil temperature and moisture, nitrogen leaching, vegetative and reproductive growth of young pear trees (Pyrus bretschneideri Rehd. ‘Yuluxiang’). The experiments involved two treatments, namely, control (traditional no-ridge planting without mulching) and mulching broad ridges with WPF (RM treatment). The results showed that the RM treatment increased soil moisture and temperature and decreased nitrogen leaching, resulting in vigorous growth of the young pear trees. Moreover, the RM treatment increased the tree trunk cross-sectional area and height of the young pear trees by 37% and 8% in 2020, respectively. The nitrate nitrogen content at the soil layer depth of 0–30 cm was significantly higher in the RM than that in control. Furthermore, the RM treatment significantly increased the fruit yield due to larger tree size. In addition, compared with control, significantly higher fruit soluble solid content of RM treatment was detected in 2020. High precipitation (423 mm) occurred during fruit enlargement stage in 2020, RM treatment decreased the rainfall infiltration in the ridge and the soil moisture in root region, resulting in the improvement of fruit quality, compared with control. Therefore, mulching broad ridges with WPF can be implemented to increase soil moisture during drought season, soil temperature, and nitrate nitrogen content, thereby improving the growth and fruit yield of young pear trees. Additionally, it can reduce soil moisture in the root zone during the rainy season and improve the fruit quality of the trees. Finally, it can reduce nitrate nitrogen leaching, thereby reducing environmental pollution.

Application of Different Indices for Soil Heavy Metal Pollution Risk Assessment Comparison and Uncertainty: A Case Study of a Copper Mine Tailing Site

The concentrations of Cu, Zn, As, Pb, Cr, and Cd in soil were analyzed in a mining area in the Inner Mongolia Autonomous Region, China. The average metal concentrations in the soil samples were 204.07 mg/kg, 88.15 mg/kg, 14.47 mg/kg 88.52 mg/kg, 56.45 mg/kg, and 0.235 mg/kg, respectively. Based on the evaluation standards, background values of the soil heavy metals, multiple soil pollution assessment indices, such as the single factor index (Pi), the geological accumulation index (Igeo), the Nemerow index (Pn), the ecological risk index (ER), and the health risk index (HI) were applied to evaluate the soil environmental risks in the study area. It was found that in different soil layer depths (0–10 cm, 10–30 cm, and 30–50 cm), the evaluation result of each index showed that there were significant spatial differences in soil pollution levels, and the focus of different indices differed greatly from each other. The Pi put 18.14% of the area at high risk of soil contamination levels, due to the fact that this index highlights the Cu pollution factor more than other indices and relatively amplifies hazards in some high-risk areas. While the Pn indicated that 61.36% of the study area was at a safe level of soil contamination, it can underestimate the regional soil heavy metal pollution risk. In order to scientifically carry out soil-pollution-risk prevention and control, it is necessary to comprehensively compare and analyze the information disclosed by different indices.

Studies on the ecology of Bulinus globosus snails: Evidence against burrowing into the soil during the dry season

Background:Bulinus globosus snail was the intermediate host of schistosome hematobium and hard to be found during the dry season. This study aimed to understand the vertical distribution of B. globosus in desiccated and re-hydrated soils and provide evidence on whether snails can drill into the soil for summer.Methods: Four laboratory/field experiments were designed to study the downward movement of the snails in desiccated soils or upward movement in re-watered soils. In Experiment 1, aquaria containing snails on the soil surface were placed in an outdoor environment to desiccate naturally. Then, snails were retrieved from different soil layers. In Experiment 2, snails on the soil surface were covered with an extra 5 cm layer of soil and 4 cm layer of water. The snail positions and survival rates were checked on the first, third, fifth, seventh, and ninth day. In Experiment 3, a seasonal ditch was selected in the field. After the soil in the ditch was naturally desiccated, 1cm, 1–3cm, 3–5cm, and 5–10 cm depth of soil layers were screened to retrieve snails. In Experiment 4, after the above ditch was naturally re-watered, snails were checked in the surface water once a week for 5 weeks.Results: At the end of Experiment 1, all the snails were only found at the soil surface. At the end of Experiment 2, snails were found neither within nor on top of the 4 cm layer of extra mud. At the end of Experiment 3, 96.92% of snails remained on the soil surface. Next, 2.77% of living snails were found in the mud crack within 1–5 cm depth. In Experiment 4, after the experimental field was naturally re-watered, no snails were found above the soil surface.Conclusion:B. globosus snails do not initially move downward into the soil during the dry season or upward to the soil surface after being re-watered.

Soil Texture and Its Relationship with Environmental Factors on the Qinghai–Tibet Plateau

Soil texture data are the basic input parameters for many Earth System Models. As the largest middle–low altitude permafrost regions on the planet, the land surface processes on the Qinghai–Tibet Plateau can affect regional and even global water and energy cycles. However, the spatial distribution of soil texture data on the plateau is largely unavailable due to the difficulty of obtaining field data. Based on collection data from field surveys and environmental factors, we predicted the spatial distribution of clay, silt, and sand contents at a 1 km resolution, from 0–5, 5–15, 15–30, 30–60, 60–100, and 100–200 cm soil depth layers. The random forest models were constructed to predict the soil texture according to the relationships between environmental factors and soil texture data. The results showed that the soil particles of the QTP are dominated by sand, which accounts for more than 70% of the total particles. As for the spatial distribution, silt and clay contents are high in the southeast plateau, and low values of silt and clay mainly appeared in the northwest plateau. Climate and NDVI values are the most important factors that affect the spatial distribution of soil texture on the QTP. The results of this study provide the soil texture data at different depths for the whole plateau at a spatial resolution of 1 km, and the dataset can be used as an input parameter for many Earth System Models.

Characteristics of Soil Temperature, Humidity, and Salinity on Bird Island within Qinghai Lake Basin, China

The temperature, moisture, and salt content of soil in alpine regions are sensitive to changes in climatic factors and are important indicators of ecosystem functions. In this study, we collected soil moisture, temperature and electrical conductivity data at different depths at a sampling site on Bird Island in Qinghai Lake during winter using a continuous soil temperature, moisture and salt content monitoring system and analyzed their variations and influential factors. The variation in soil moisture showed an obvious ‘V-shaped’ pattern from 00:00 to 23:00 and an upward trend with soil layer depth. From 00:00 to 23:00, the overall soil temperature data fitted a ‘unimodal’ curve and showed a clear and continuous upward trend with soil layer depth at a rate of 0.684 (p &lt; 0.001). Soil electrical conductivity data also exhibited a distinct ‘V-shaped’ pattern from 00:00 to 23:00 and a continuous increase with increasing soil depth. The correlation between soil temperature, moisture, and conductivity and the spatial distribution of five climate factors indicated that climate factors accounted for 53.6% of the changes in soil temperature, moisture, and salinity. Climate factors showed a significant positive correlation with soil temperature, moisture, and conductivity (p &lt; 0.001), and air temperature was the most important factor influencing soil temperature and soil moisture changes, whereas wind direction was the most important factor influencing soil conductivity. (Wind direction and wind speed affect soil evapotranspiration, and then affect soil moisture and solute transport process). The results of this preliminary study reveal the characteristics associated with soil temperature, moisture, and salinity changes in winter within the wetlands of Bird Island on Qinghai Lake in the context of climate change, and they can be used as valuable reference data in further studies investigating associated changes in ecosystem functions.

Effect of Different Irrigation Regimes on the Early Development of Pot-Grown Black Locust Saplings

Black locust currently is considered to be the most important tree species of short-rotation forests in Hungary with the purpose of either woody biomass or industrial wood. Despite the general supposition on the drought tolerance of the species, water availability seems to be a more limiting factor to exploit the growing potential of highly productive new varieties than nutrient amendments. Preliminary measurements of the current study were made on the connection between the depth of the water-retaining soil layer and the growth of saplings on black locust plantations. A significant negative correlation was found between the depth of the water-retaining layer, the stem diameter and the height of the saplings. To investigate the phenomenon, a model experiment was launched with loamy sand soil in the pots. During six weeks, pots were watered every morning up to the weight referring to the 30, 40, 60 and 80% of field capacity (FC). Our results showed that 30% FC was only sufficient for the survival of the saplings, growth was only noticeable at plants with 40% FC or more. During the first 4 weeks, differences in growth and cumulative evapotranspiration between the 60% and 80% FC treatment were not considerable. However, in the last two weeks, saplings with the highest FC produced substantially higher biomass, resulting in a one-third higher final weight than those of FC 60%. Even with the limited soil capacity of the pots, water use of these saplings of 1 m height and 1 cm stem diameter exceeded 1.5 L per day. Our results confirmed that black locust is a water-intensive species with a high water use potential, which emphasizes the importance of irrigation on nurseries and the first years of plantations.

Younger carbon dominates global soil carbon efflux.

Soil carbon (C) is comprised of a continuum of organic compounds with distinct ages (i.e., the time a C atom has experienced in soil since the C atom entered soil). The contribution of different age groups to soil C efflux is critical for understanding soil C stability and persistence, but is poorly understood due to the complexity of soil C pool age structure and potential distinct turnover behaviors of age groups. Here, we build upon the quantification of soil C transit times to infer the age of C atoms in soil C efflux (aefflux ) from seven sequential soil layer depths down to 2m at a global scale, and compare this age with radiocarbon-inferred ages of C retained in corresponding soil layers (asoil ). In the whole 0-2m soil profile, the mean aefflux is (mean with 5%-95% quantiles) year and is just about one-eighth of asoil ( year), demonstrating that younger C dominates soil C efflux. With increasing soil depth, both aefflux and asoil are increased, but their disparities are markedly narrowed. That is, the proportional contribution of relatively younger soil C to efflux is decreased in deeper layers, demonstrating that C inputs (new and young) stay longer in deeper layers. Across the globe, we find large spatial variability of the contribution of soil C age groups to C efflux. Especially, in deep soil layers of cold regions (e.g., boreal forests and tundra), aefflux may be older than asoil , suggesting that older C dominates C efflux only under a limited range of conditions. These results imply that most C inputs may not contribute to long-term soil C storage, particularly in upper layers that hold the majority of new C inputs.

Application of soil quality index to determine the effects of different vegetation types on soil quality in the Yellow River Delta wetland

Assessment of soil quality in different vegetation types of wetland ecosystems is essential for soil functioning, such as nutrient cycling and vegetation growth, particularly the maintenance of wetland ecosystem sustainability. Wetland degradation can extremely influence soil quality. However, prediction of soil quality in terms of soil quality index in wetland soils remains obscure. In this study with the fundamental goal to assess soil quality, we have intended to assemble a range of soil quality indicators to characterize the soil quality index (SQI). The minimum data set (MDS) from the Principal component analysis (PCA) was used to determine the SQI. With such objectives, three vegetation types: Robinia pseudoacacia community (tree), Tamarix chinensis community (bush), and Suaeda salsa community (grass) were selected in the Yellow River Delta wetland, eastern of China. A total of 108 soil samples [3 sites (tree, bush and grass)—3 field plots—3 replicates—4 soil depth layers: 0–10 cm, 10–20 cm, 20–40 cm, and 40–60 cm] were collected for laboratory analyses. This study showed that there were high variations in soil physical and chemical properties among the three sites. Soil organic carbon (SOC), silt, clay, and pH at tree site, total soil porosity (TSP), soil organic carbon (SOC), pH, and soil bulk density (SBD) at bush site, and total soil porosity (TSP), silt, and soil electronic conductivity (SEC) at grass site were retained in the MDS. SOC and TSP were the key soil quality indicators. The values of the SQI at 0–10 cm soil depth at all three sites (2.236, 0.895, and 2.573 respectively) were the highest compared with other soil depths, indicating the best soil quality in the upper soil layers (0–10 cm). The values of the SQI at 0–10 cm soil depth at both tree site and grass site were similar, and they were higher than those at bush site. At tree site, the values of the SQI decreased with increasing soil depth, which indicated that soil quality became worse with depth. At bush site, the values of the SQI decreased with increasing soil depth (0–40 cm), while the values increased at 40–60 cm depth, indicating better soil quality in the deeper soil layers (40–60 cm). At grass site, the values of the SQI at 10–20 cm and 40–60 cm soil depth were lower than those at 20–40 cm soil depth, indicating better soil quality at 20–40 cm soil depth. It is concluded that the SQI can be compared more accurately in different vegetation types of wetland ecosystems based on its simplicity and quantitative flexibility. These findings are of importance because the assessment of the SQI allows to quantify different vegetation effects on soil quality.

Effects of Permafrost Degradation on Soil Carbon and Nitrogen Cycling in Permafrost Wetlands

Climate change is one of the greatest threats to high-latitude permafrost and leads to serious permafrost degradation. However, few attention has been paid to whether peat soil carbon or nitrogen is sensitive to permafrost degradation. This study has selected three typical sample areas (MoHe-continuous permafrost, TaHe-Island-shaped melting permafrost, Jagdaqi-Island-shaped melting permafrost) as research object to compare the response rate and degree of peat soil carbon and nitrogen under permafrost degradation. The results show that soil organic carbon and nitrogen contents are the highest in 0–10 cm soil and permafrost regions show obvious surface aggregation. The carbon content of different types of frozen soil decreases with the depth of soil layer, and the differences are significant (p &amp;lt; 0.01). The distribution pattern of total nitrogen content in each soil layer among different permafrost types is Mohe &amp;lt; Tahe &amp;lt; Jagedaqi. And when it is getting vertically deeper than the surface layer, there is no significant difference between the soil layers in soil profile. The study also focuses on the variations of carbon and nitrogen content in different soil layers of peatland in typical permafrost regions. The results show that soil carbon responds faster to the degradation of frozen soil than soil nitrogen. Moreover, the accumulation degree of soil carbon is also significantly higher than soil nitrogen. Under climate change and for better permafrost conservation, it is necessary to study how the peatland’s soil carbon and the nitrogen are influenced by the permafrost degradation in high latitude.

Does biochar improve nutrient availability in Ultisols of tree plantations in the Ecuadorian Amazonia?

AbstractThe application of biochar to strongly weathered soils is thought to supply nutrients and improve nutrient retention. We hypothesized that biochar increases (a) total N, bioavailable macronutrient (NH4–N, P, K, Ca, Mg), micronutrient (Fe, Mn, Zn, Cu), and plant‐beneficial Na concentrations; and (b) nutrient retention in the topsoil. We grew the native leguminous Brazilian firetree [Schizolobium parahyba var. amazonicum (Ducke) Barneby] and the exotic beechwood (Gmelina arborea Roxb.) in a full factorial split‐split‐plot design at La Victoria and Los Zapotes, Ecuadorian Amazonia. The treatments included amendment of mineral fertilizer plus lime, 3 and 6 t ha−1 biochar (locally produced charcoal), and a control. We sampled the 0‐to‐0.25‐ and 0.25‐to‐0.50‐m soil depth layers before the start of the experiment in 2009 and six times until 2013. The site at Los Zapotes was more fertile as reflected by a significant site effect on most studied soil properties in both depth layers. Biochar increased modified Olsen (NaHCO3+EDTA)‐extractable Ca (p &lt; .05) and Zn concentrations (p &lt; .1) and total N concentrations (p &lt; .05) in topsoil. Mineral fertilizer plus lime increased Olsen‐extractable P, K, Ca, Mg, and Zn concentrations (all p &lt; .05) but reduced Olsen‐extractable Fe concentrations (p &lt; .05) in topsoil. Biochar increased Ca (p &lt; 0.1) and Zn (p &lt; .05) retention in mineral fertilized topsoils but decreased total N retention (p &lt; .05) in unfertilized topsoils. The amendment of up to 6 t ha−1 biochar did not increase the fertility of the studied degraded Amazonian Ultisols sufficiently to enhance tree growth.

The Effect of the Distance from a Path on Abiotic Conditions and Vascular Plant Species in the Undergrowth of Urban Forests and Parks.

Urban forests and parks are essential for the maintenance of biodiversity as well as human health and well-being. Residents and tourists commonly use urban forests and parks for recreational and sport purposes, contributing to changes in vegetation. This study aimed to assess the effect of distance from formal paths on the abiotic conditions, vegetation cover, as well as ecological diversity of vascular plant species in the undergrowth of urban forests and parks. The investigations were carried out in 2021 in 10 urban forests and 10 urban parks located in Kraków (southern Poland), using a total of 400 plots (1 × 1 m) situated in close (CL) and further (FU) vicinity of formal paths. We found a positive effect of the distance from the path on the depth of the compact soil layer, vegetation cover and height of the tallest shoot in the undergrowth of urban forests and parks. On the other hand, the distance from the path had a negative effect on the number of vascular plant species in the undergrowth in both forests and parks. Forests and parks differed significantly from each other in light intensity, the content of P in soil, depth of compact soil layer, number of species, as well as in cover-abundance of species representing different life forms, dispersal types, habitat affiliations and origins. Trampling leads to low plant cover and height of the undergrowth, as well as contributing to shallow localization of the compact soil layer near paths. Human movement on paths (walking, running, biking) with accompanying pets contributes to the successful dispersal of plants, resulting in high species richness. High light intensity in urban parks enhances the total number of species, cover-abundance of meadow and grassland plants, as well as cover-abundance of hemicryptophytes. The number of alien species was higher in parks than in forests, but the cover-abundance of alien plants was higher in forests than in parks. Urban forests are more suitable for the growth and biomass production of some alien herbs than urban parks, as mowing commonly used in parks appears to be an important factor in reducing their cover abundance. Regular fertilization and irrigation contribute to the high content of phosphorus in the soil, as well as to the high cover-abundance of meadow and grassland plants in urban parks. Urban forests enhance cover abundance of plants with dispersal mechanisms of the Bidens and Lycopodium types, whereas urban parks promote cover abundance of plants with the dispersal of the Allium type. Further study is needed to confirm the role of urban forests and parks in the preservation of ancient forest species, as well as to develop an appropriate design of paths that will allow the protection of vegetation and soil in urban forests and parks.

Effects of Litter Decomposition on Soil N in Picea mongolica Forest at Different Forest Ages

In order to study the effects of litter decomposition on soil nitrogen of Piceamongolica in different forest ages, young forest (0–5a), middle-aged forest (5–30a), and near-mature forest (30–40a) stands were selected in the Baiyinaobao National Nature Reserve. Litter decomposition was assessed using the decomposition bag method. The seasonal and vertical spatial variation characteristics of total N, NH4+—N, and NO3−—N caused by litter decomposition in P. mongolica forest soil were studied for different stand ages. Results showed that: (1) There was a positive correlation between litter N content and soil organic matter, total N content, and NO3−—N content across different forest ages (p &lt; 0.05). There was a negative correlation between litter N and NH4+—N contents. A negative correlation between litter C content and soil organic matter, total N, and NO3−—N contents was also observed. (2) In this study, the total N and NO3−—N increased with the increase in N content during litter decomposition.NH4+—N in the soil was positively correlated with sample date, soil NO3−—N, and forest age (p &lt; 0.05), and negatively correlated with soil depth (p &lt; 0.01). NO3−—N in the soil was negatively correlated with sample date and forest age (p &lt; 0.05), and significantly negatively correlated with soil depth (p &lt; 0.01). (3) the NH4+—N content is greater than that of NO3−—N in each soil layer for the three forest ages. The correlation analysis indicated which factors influenced NH4+—N and NO3−—N in the soil. The content decreased during February and November and increased in May and August. (4) The total N, NH4+—N, and NO3−—N in the forest soils across the three forest ages increased with the depth of the soil layer (0–50 cm) and showed an overall downward trend. The contents of NH4+—N in the soil layer from the young forest (0–10 cm, 10–20 cm and 20–30 cm, 30–40 cm, and 40–50 cm) differed significantly (p &lt; 0.05), as did the NO3−—N results (p &lt; 0.05), while results from the middle-aged forest and near-mature forest increased with soil layer depth. There was no significant difference in the NH4+—N soil content. (5) The NH4+—N in the forest soils showed a trend from mature forest &gt; middle-aged forest &gt; young forest. This trend for soil NO3−—N content is consistent with that of the NH4+—N content in the Picea mongolica forest soil.

Simplified Assessment Methodology of Radionuclide Contamination for Subsurface Soil

Determining whether to release a site after decommissioning a nuclear facility should be preceded by an environmental impact assessment of the exposure radiation dose according to the radionuclides in the soil. Currently, in Korea, various evaluation methodologies and decommissioning technologies are being studied for the first decommissioning of nuclear power plants, starting with Kori Nuclear Power Plant Unit (Kori-1), which is based on the “Multi-Agency Radiation Survey and Site Investigation Manual MARSSIM” developed in the United States. The scope and evaluation targets of deep soil may differ depending on the purpose, but it has been confirmed that the International Atomic Energy Agency and the U.S. Nuclear Regulatory Commission are targeting subsurface soil. MARSSIM outlines the need for an evaluation of this subsurface soil but does not suggest specific methods. In NUREG-1757, which complements MARSSIM, it is confirmed that subsurface soil specifically means a soil layer that is 15 to 30 cm deep in the surface layer. In the current study, using the previously verified computational code RESidual RADioactivity (RESRAD)-ONSITE, a methodology for summation is proposed to evaluate the impact of subsurface soil more flexibly and realistically while minimizing the exposure dose evaluation procedure. When using RESRAD-ONSITE according to this evaluation methodology, it was confirmed that it is possible to respond to changes in the depths of various soil layers. In addition, it was also confirmed that this methodology is adaptable to the contamination of nuclides, such as 60Co, 137Cs, 152Eu, and 154Eu, which are expected to be major nuclides when decommissioning nuclear facilities.