Differences In Soil Organic Matter Research Articles

Study on Soil Fertility Characteristics of Walnut Orchards with Different Parent Materials and Soil Types in Gyaca County, Tibet

Walnut trees on the Tibetan Plateau have sustainable and nutritious characteristics. They grow naturally without the use of any chemical fertilizers and pesticides. Therefore, the soil fertility of walnut orchards is a key factor influencing walnut yield and quality. This experiment measured and analyzed the basic soil nutrient content, microbial biomass carbon (MBC), nitrogen (MBN), phosphorus (MBP), and leaf nutrient indicators in five types of representative walnut orchard soil parent materials in Gyaca County to clarify the fertility characteristics of different soil types and their correlations with walnut nutrients, providing a basis for the sustainable development of the plateau walnut industry. The results showed that there were significant differences in soil organic matter (SOM), total nitrogen (TN), available nutrient contents, and microbial activity among soil types with different parent materials. The comprehensive representation of available nutrient levels in the soils is as follows: gray-cinnamon soil and calcareous alluvial soil > mountain meadow soil > plateau prairie soil and brush prairie soil. The average MBC, MBN, and MBP contents in the five soils were 368.8 mg/kg, 28.4 mg/kg, and 23.6 mg/kg, respectively, and the content in the topsoil (0–20 cm) was higher than that of the subsoil (20–40 cm). The total nitrogen (PN), total phosphorus (PP), and total potassium (PK) contents in walnut leaves were found to be closely related to the soil physicochemical properties and microbial activity, among which five indicators, including soil TN, available nitrogen (AN), SOM, MBC, and slowly available potassium (SAK), had the greatest impact on leaf nutrient levels. These findings are valuable for the future management and development of walnut orchards. Therefore, for different soil parent materials and soil types, improving the soil fertility and actively applying nitrogen-rich organic fertilizers should be prioritized to improve the yield and quality of Tibetan Plateau walnuts.

Effects of γ-polyglutamic acid supplementation on alfalfa growth and rhizosphere soil microorganisms in sandy soil

This study aimed at exploring the effects of γ-polyglutamic acid on the growth of desert alfalfa and the soil microorganisms in the rhizosphere. The study examined the effects of varying concentrations of γ-polyglutamic acid (0%-CK, 2%-G1, 4%-G2, 6%-G3) on sandy soil, the research investigated its impact on the growth characteristics of alfalfa, nutrient content in the rhizosphere soil, and the composition of bacterial communities. The results indicated that there were no significant differences in soil organic matter, total nitrogen, total phosphorus, total potassium, and available phosphorus content among the G1, G2, and G3 treatments. Compared to CK, the soil nutrient content in the G2 treatment increased by 14.81–186.67%, showing the highest enhancement. In terms of alfalfa growth, the G2 treatment demonstrated the best performance, significantly increasing plant height, chlorophyll content, above-ground biomass, and underground biomass by 54.91–154.84%. Compared to the CK treatment, the number of OTUs (operational taxonomic units) in the G1, G2, and G3 treatments increased by 14.54%, 8.27%, and 6.84%, respectively. The application of γ-polyglutamic acid altered the composition and structure of the bacterial community, with Actinobacteriota, Proteobacteria, Chloroflexi, Acidobacteriota, and Gemmatimonadota accounting for 84.14–87.89% of the total bacterial community. The G2 treatment significantly enhanced the diversity and evenness of soil bacteria in the rhizosphere. Redundancy analysis revealed that organic matter, total nitrogen, total potassium, moisture content, and pH were the primary factors influencing the structure of bacterial phyla. At the genus level, moisture content emerged as the most influential factor on the bacterial community. Notably, moisture content exhibited a strong positive correlation with Acidobacteriota, which in turn was positively associated with indicators of alfalfa growth. In summary, the application of γ-polyglutamic acid at a 4% ratio has the potential for improving sandy soil quality, promoting plant growth, and regulating the rhizosphere microbial community.

Analysis of soil organic matter influencing factors in the Huangshui River Basin by using the optimal parameter-based geographical detector model

To quantitatively analyze the spatial distribution of soil organic matter (SOM) content and its main influencing factors in the Huangshui River Basin, Qinghai Province, China, a total of 13 factors including topography, climate, soil properties, and vegetation cover were selected. The influence of these factors on the spatial distribution of SOM content was analyzed using the geographical detector model and the Pearson correlation coefficient method. The results showed that the average SOM content in the cultivated soil layer of the Huangshui River Basin was 28.38 g·kg−1. The results of factor detection and Pearson correlation analysis indicated that the three dominant factors causing differences in the spatial distribution of SOM content were mean annual temperature, altitude, and soil pH. Furthermore, SOM content was negatively correlated with temperature and positively correlated with elevation. When the factors interacted, they exhibited a type of bi-enhance or nonlinear-enhance. The interaction between two factors improved the explanatory power of SOM, indicating the complexity of factors causing spatial distribution differences in SOM. This study provides a favorable basis for precision fertilization, soil improvement, and of soil quality improvement in the Huangshui River Basin.

Improving digital mapping of soil organic matter in cropland by incorporating crop rotation

Despite human activities are key influencing factors for cropland soil organic matter (SOM), detailed characterization of human activities has always been limited in the digital mapping of SOM due to the lack of proper representations of human’s cropland use activities. Crop rotation is an essential human agricultural practice significantly affecting the spatial–temporal variations of SOM due to the periodically dynamic changes of crops. Thus, incorporating crop rotation in the digital soil mapping holds high potential for improving SOM prediction. Here, we applied time-series radar Sentinel-1 and optical Sentinel-2 to map crop rotation systems by a hierarchical rule-based method. Then we explored the effectiveness of incorporating such information in predicting SOM by implementing various combinations of predictive variables. We chose a typical multiple cropping region with various crop rotations in southern China. The model performance was evaluated by 10-fold cross-validation. Results showed significant differences in SOM among the crop rotation systems, and the single rice rotated with vegetables has the highest SOM followed by the high-diversity vegetables and long-term orchard systems. Adding crop rotation enhanced the predictability of SOM with a decrease in RMSE by 7% and an increase in R2 by 24%. Furthermore, the crop rotation systems appeared more important in the predictive models than the soil, topographic, and climatic variables. Our results demonstrated the effectiveness of including crop rotation in predicting SOM over complex agricultural landscapes. Our study indicated that human activities should be characterized more detailedly in cropland soil mapping, and that crop rotation containing information on the seasonal dynamics of cropland may be an option for such characterization.

Multi-Scale Integration and Distribution of Soil Organic Matter Spatial Variation in a Coal–Grain Compound Area

Soil organic matter (SOM) scale effects are critical for crop growth and food security, especially in coal–grain complexes. However, few studies describe the spatial variation in SOM and its influencing factors at different sampling scales. Here, geostatistical theory and mathematical statistical methods were adopted to analyze the spatial variation characteristics of and structural differences in SOM in the coal mining subsidence area at Zhaogu No. 2 Mine at different sampling scales. The results showed that SOM varied spatially at large, medium, and small scales, and the coefficients of variation were 28.07%, 14.93%, and 14.31%, respectively, which are moderate values. The characteristic functions of the SOM content at different sampling scales differed, and the spatial structure scale effect was obvious. The spatial distribution of the SOM content fitted by the multiscale fitting model method was generally the same as the spatial distribution law of the SOM content fitted by the single scale kriging interpolation method; however, in terms of the detailed expression and spatial distribution of small-scale SOM content, the fitting model method was more accurate, and the accuracy increased by 36%. At the different sampling scales, sample size and soil type had specific effects on the SOM spatial distribution. These results provide research concepts and technical countermeasures for improving food security and the ecological environment in the coal–grain complex and help ensure sustainable agricultural lands.

Soil organic matter in temperate forest-grassland systems: A case study from the Southern Cis-Ural, Russia

Understanding the dynamics of SOM in different land use types is critical for effective land management and climate mitigation strategies. In this study, we investigated the differences in soil organic matter (SOM) content between forest and grassland landscapes in the mountainous zone of Republic of Bashkortostan, Russia. We collected soil samples from multiple locations under both land use types and analysed them for SOM content using standard laboratory techniques. The results showed that the SOM content varied from 2.2 to 15.3% under forest landscape with an average of 6.7% and was characterized by high variability (51.8%). The SOM concentrations under grassland ranged from 2.1 to 6.5% with an average of 3.2%, while the coefficient of variation was 31.8%. According to the classification, the average SOM value in forest soils was classified as “high”, while in grassland soils it was classified as “low”. Overall, the variability in SOM content within forested landscapes can be influenced by a range of factors, including topography, erosion, and redeposition of soil. These factors contributed to the complex patterns of SOM accumulation and decomposition observed in forest soils, and should be considered when evaluating the potential impacts of land use change on SOM. Our study highlights the importance of understanding the factors that influence SOM content in soils, and the need for careful management of land use systems to maintain or enhance soil fertility and productivity.

Effect of No-Tillage Management on Soil Organic Matter and Net Greenhouse Gas Fluxes in a Rice-Oilseed Rape Cropping System

No-tillage (NT) management is considered a leading approach for sustaining crop production and improving soil and environmental quality. Based on a long-term no-tillage experiment in a rice–oilseed rape cropping system, we examined differences in soil organic matter (SOM), soil microbial carbon (C) and nitrogen (N) content, and methane (CH4) and carbon dioxide (CO2) fluxes between NT and conventional tillage (CT) management. SOM under NT was 21.0 g kg–1, and a significant difference was detected between 2004 and 2016. SOM increased under NT and CT by averages of 0.60 and 0.32 g kg–1 year–1, respectively. Soil microbial C and N content were higher under CT than under NT. However, soil C:N ratios under NT were 17.4 and 9.7% higher than the CT, respectively, whereas soil microbial C:N ratios under NT were on average 9.47 and 9.70% higher. In addition, about 70% of CO2 net uptake and over 99% of net CH4 emissions occurred during the rice season in May–September in the rice–oilseed rape cropping system. Annual cumulative CH4 and daytime net ecosystem CO2 exchange (NEE) under NT was 1813.9 g CO2 equiv. m–2, 10.8% higher than that under CT. Our results suggest that a higher soil microbial C:N ratio and NEE (CH4 and daytime CO2) could contribute to increasing SOM/C in the surface soil under NT management.

Effect of inflorescence litter from distinct species and life forms on soil nutrients and microbial biomass in the eastern Tibetan Plateau

The influence of plant litter on soil varies with soil depth, species composition, and life forms of plants. Recalcitrant indexes are significantly lower in inflorescence litter as compared to leaf litter (C/N, N/P, lignin, cellulose, lignin-cellulose index, and lignin/N), with a majority of the interactions occurring between species and litter types. In a field pot experiment, N exchangeable pool and soil solutions with and without litter addition differed significantly with increased soil dissolvable inorganic nitrogen (DIN) and available phosphorus (A−P) at 0–5 cm shallow soil layer in samples with added litter. However, there was an unexpected decline in soil organic matter (SOM) after inflorescence litter addition as higher content of non-structural carbohydrates triggered faster decomposition of SOM. Exchangeable pool had significant interactions between litter addition and soil depth. Furthermore, different NH4+−N and Organic−N in soil solution were developed from litter addition, but the differences in SOM was mainly determined by soil depths. Both microbial biomass carbon (MBC) and microbial biomass nitrogen (MBN) were improved with inflorescence litter addition in the shallow soil layer. After sorting the inflorescence litters according to life forms, A−P was the most dominant nutrient and DIN was the least dominant nutrient in phanerophytes while a completely contrasting trend was seen in geophytes. Thus, chemical properties of inflorescence litter were remarkably different from those of leaf litter, which elicited species-specific and life form-specific effects on soil nutrient pool, and efficiently modified soil nutrients.

Long-term crop rotation diversification enhances maize drought resistance through soil organic matter

Climate change adaptation requires building agricultural system resilience to warmer, drier climates. Increasing temporal plant diversity through crop rotation diversification increases yields of some crops under drought, but its potential to enhance crop drought resistance and the underlying mechanisms remain unclear. We conducted a drought manipulation experiment using rainout shelters embedded within a 36-year crop rotation diversity and no-till experiment in a temperate climate and measured a suite of soil and crop developmental and eco-physiological traits in the field and laboratory. We show that diversifying maize-soybean rotations with small grain cereals and cover crops mitigated maize water stress at the leaf and canopy scales and reduced yield losses to drought by 17.1 ± 6.1%, while no-till did not affect maize drought resistance. Path analysis showed a strong correlation between soil organic matter and lower maize water stress despite no significant differences in soil organic matter between rotations or tillage treatments. This positive relationship between soil organic matter and maize water status was not mediated by higher soil water retention or infiltration as often hypothesized, nor differential depth of root water uptake as measured with stable isotopes, suggesting that other mechanisms are at play. Crop rotation diversification is an underappreciated drought management tool to adapt crop production to climate change through managing for soil organic matter.

Soil management legacy alters weed-crop competition through biotic and abiotic pathways

Agricultural practices often have persistent effects on soil physicochemical properties and soil biota, which can feedback to influence plant performance. We investigated management-induced differences in soil fertility and soil microbiota for their legacy effects on plant nutrient acquisition and crop/weed competition. Sorghum bicolor (L.) Moench (sorghum), Ambrosia artemisiifolia (L) (ragweed), and Amaranthus powellii S. Wats. (pigweed) were grown as monocultures and mixtures in the greenhouse in soils with distinct management histories. Cross inoculations of sterilized soils were used to quantify biotic vs. abiotic influence on plant growth, nutrient uptake and competitive outcomes. Differences in management history led to a two-fold difference in soil organic matter (OM), and a 37% increase in N acquisition in all species in the high OM soil. The increase in N availability preferentially benefitted pigweed growth at the expense of sorghum. However, microbiota from the high OM soil alleviated the negative effects of pigweed competition on sorghum. Soil management legacy also affected sorghum tiller production and mycorrhizal colonization. Management-induced differences in soil biotic and abiotic factors altered plant performance in a species-specific manner. Management legacy effects on soil microbiota have the potential to increase crop competitiveness against some weed species.

Soil faunal community composition alters nitrogen distribution in different land use types in the Loess Plateau, China

Environmental factors and human disturbance can affect the richness and diversity of soil fauna and nutrients. However, few studies have systematically evaluated the soil faunal community composition and N distribution and the relationships between them in different land use types in the Loess region of China. In this study, we assessed the correlation between these factors and their variation among three land use types: woodland, grassland, and abandoned land. The results revealed Formicidae (34.9%), Isopoda (26.1%), and Lumbricidae (11.2%) to be the dominant groups of soil fauna in the Loess area. The soil faunal community composition was related to both the soil and land use types (p < 0.05). The effects of different land use types on soil physicochemical properties change the community distribution of soil fauna, thus, affecting the role of soil faunae in the N cycle. The differences in soil organic matter, soil moisture content, and bulk density affect the composition of the soil faunal community. The diversity index of soil faunae in the three land use types was the highest in woodland (0.59–2.31) and the lowest in abandoned land (0.41–1.92). The contents of total N, nitrate N, ammonium N, and microbial biomass N were the highest in woodland followed by grassland and abandoned land. Redundancy analysis indicated significant positive correlations between individuals of Lumbricidae and NH4+-N, individuals of Stylommatophora and NO3−-N, individuals of Acariformes and total N, and individuals of Isoptera and microbial biomass N. Different land use types, therefore, alter the diversity and richness of the soil faunae in the Loess region, and the soil faunal community composition plays a significant role in promoting the content of different N forms in the soil environment.

Herbaceous-shrub species composition, diversity and soil attributes in moist grassland, shrub grassland and savanna in Central Brazil

The Cerrado biome comprises a mosaic of different vegetation types such as grasslands, savannas and forests. We studied soil properties and the herbaceous-shrub layer vegetation in moist grassland, shrub grassland and savanna. We assume that the moist grassland will present a distinct species composition from the other vegetation types, as waterlogging leads to changes in soil features that act as a filter of species that are adapted to this condition. The results showed that the soil in the moist grassland was distinct from the ones in savanna and shrub grassland. We found that the soil organic matter and the proportion of clay particles determined the variation in composition/cover and richness in the herbaceous-shrub layer in the three vegetation types. Higher organic matter content and smaller proportion of clay particles explained the larger distinction in richness and cover in moist grassland (lowest one) compared to shrub grassland and savanna sites. A total of 228 species in 47 families were sampled in the three vegetation types, and only five species were common to all three. The results revealed that, on a local scale, adjacent vegetation types of Cerrado with differences in soil organic matter and clay vary greatly in terms of growth forms, species composition and cover in the herbaceous-shrub layer. Understanding how herbaceous-shrub species richness and cover is related to soil nutrients, and texture heterogeneity in the mosaic of the vegetation types of the Cerrado may be useful in maintaining plant species structure and diversity.

Effects of burning harvested residues on the archaeal and bacterial communities of Eucalyptus urophylla substituting native vegetation

The land preparation method of burning harvested residues considerably affects soil archaeal and bacterial communities. However, the changes in the archaeal and bacterial communities of Eucalyptus urophylla plantation and the driving factors of microbial community diversity are still unknown. This study explored the effects of E. urophylla replacement for native vegetation and the burning of harvested residues on the diversity of archaeal and bacterial communities. Soil samples were collected from the E. urophylla plantation with burnt (Burn) and retained (Retain) harvest residues after 5 years, and the native vegetation was selected as a control (CK). Results show that significant differences in soil organic matter, available phosphorus, available boron, soil bulk density, and moisture content were found among the three stands (p < 0.05), and the concentrations of OM, AP and AB in Burn are the lowest, and BD is the highest. CK has the highest diversity of archaeal and bacterial communities, whereas Burn has the lowest. The co-occurrence network pattern of CK shows high robustness and high positive interaction between archaea and bacteria. However, Burn's network shows extremely low robustness and high negative interaction. Available phosphorus, organic matter, and bulk density are the key factors affecting archaeal and bacterial communities as confirmed by random forest models, redundant analysis, and structural equation modeling. Furthermore, the influence of environmental factors on archaeal communities is greater than that on bacteria, and the total effect of environmental factors on bacteria through archaeal community mediation is significant, including 79.45% indirect effects. These results can serve as a reference to enhance the management of harvested residues in E. urophylla plantations in the future.

Differences in soil organic matter and humus of sandy soil after application of biochar substrates and combination of biochar substrates with mineral fertilizers

The effort to achieve the sustainable farming system in arable soil led to the intensive search for a new solution but an inspiration can also be found in the application of traditional methods of soil fertility improvement as it is shown in numerous examples in history. Recently many scientific teams have focused their attention on the evaluation of biochar effects on soil properties and crop yields. Since there are a lot of knowledge gaps, especially in explanations how biochar can affect soil organic matter (SOM) and humus substances, we aimed this study at the solution of these questions. Therefore, the objective of the experiment was to evaluate the impact of two biochar substrates (B1 – biochar blended with sheep manure, and B2 – biochar blended with sheep manure and the residue from the biogas station) at two rates (10 and 20 t ha-1) applied alone or in combination with mineral fertilizers (Urea was applied in 2018, at rate 100 kg ha-1, and Urea at rate 100 kg ha-1 + AMOFOS NP 12-52 at 100 kg ha-1 were applied in 2019) on the quantity and quality of SOM and humus of sandy soil (Arenosol, Dolná Streda, Slovakia). The results showed that application of the biochar substrates together with mineral fertilizers (MF) had more pronounced effect on the organic matter mineralization in the sandy soil which resulted in low accumulation of soil organic carbon (Corg) and labile carbon compared to biochar substrates treatments without MF. The share of humic substances in Corg significantly decreased by 16, 50, 16 and 24% in B1 at 10 t ha-1, B1 at 20 t ha-1, B2 at 10 t ha-1 and B2 at 20 t ha-1 treatments, respectively, compared to the control. A similar tendency was observed for biochar substrates treatments + MF, compared to MF control. The carbon content of humic substances (CHS) was equal to 4.40 – 5.80 g kg-1 and the biochar substrates had statistically significant influence on CHS content. On average, there was a smaller decrease of CHS in B1 at rate 10 t ha-1 than at rate 20 t ha-1 and no effect of B2 compared to control. The carbon content of fulvic acid (CFA) was 9% higher in B1 at 10 t ha-1, and 20 t ha-1, 47% higher in B2 at 10 t ha-1 and 17% higher in B2 at 20 t ha-1 compared to control. As a result of biochar substrates + MF application, the reduction in CFA was observed. The results showed a decrease of CHA : CFA ratio with association to biochar substrates alone application compared to control on one hand, and a wider of CHA : CFA ratio in biochar substrates + MF treatments in comparison to MF control on the other hand. Humus stability was increased in biochar substrates alone treatments compared to control, on the other hand, compared to MF control, the application of biochar substrates + MF resulted in a lower humus stability.

Immediate Changes in Organic Matter and Plant Available Nutrients of Haplic Luvisol Soils Following Different Experimental Burning Intensities in Damak Forest, Hungary

One of the major pedological changes produced by wildfires is the drastic modification of forest soil systems properties. To our knowledge, large research gaps are currently present concerning the effect of such fires on forest Haplic Luvisols soils in Central Europe. In this study, the effects of experimental fires on soil organic matter and chemical properties at different burning intensities in a Central European forest were examined. The study was conducted at Damak Forest, in Hungary, ecosystem dominated by deciduous broadleaf trees, including the rare Hungarian oak Quercus frainetto Ten. The experimental fires were carried out in nine different plots on Haplic Luvisol soils transferred from Damak Forest to the burning site. Three types of fuel load were collected from the forest: litter layer, understorey and overstorey. Groups of three plots were burned at low (litter layer), medium intensity (litter and understorey) and high intensity (litter, understorey and overstorey). Pre-fire and post-fire soil samples were taken from each plot, analysed in the laboratory and statistically compared. Key plant nutrients of organic matter, carbon, potassium, calcium, magnesium and phosphorus were analysed from each sample. No significant differences in soil organic matter and carbon between pre- and post-fire samples were observed, but high intensity fires did increase soil pH significantly. Calcium, magnesium and phosphorus availability increased significantly at all fire intensity levels. Soil potassium levels significantly decreased (ca. 50%) for all intensity treatments, in contrast to most literature. Potassium is a key nutrient for ion transport in plants, and any loss of this nutrient from the soil could have significant effects on local agricultural production. Overall, our findings provide evidence that support the maintaining of the current Hungarian fire prevention policy.

Short-term effect of reducing conventional tillage intensity on some physical and chemical properties of volcanic soils in Rwanda

Volcanic soils which comprise a minor portion worldwide are generally characterized by their high natural fertility yet susceptible to soil erosion due to their fragility. Regardless of which, the success in soil management to maintain its quality depends on the understanding of how the soil properties respond to its disturbance through tillage practices over time. This study was conducted in the highland region of Rwanda, Musanze District, Busogo Sector from December 2016 to June 2017, to evaluate the short term effect of conventional and reduced tillage on certain physical and chemical properties of volcanic soils. Bulk density (BD) and total porosity (TP) as induced soil compaction and aeration respectively were selected as soil physical properties. Soil pH, soil organic matter (SOM) and soil organic carbon (SOC) as generally used in soil fertility assessments and land suitability were selected as soil chemical properties. Soil samples were collected at the end of May 2017 from the plots laid out in RCBD replicated four times, then analyzed and data were subjected to ANOVA using GeniStat software. The results showed no significant difference in SOM and BD (p>0.05) while soil pH was significantly different (p<0.05) in these tillage systems. The results of this study evinced that reduced tillage is suitable in this region, since it is promising in the SOM enhancement. Evidences of this study will expose researchers and policy makers to new strategies to improve the soil structure stability, yet minimizing soil vulnerability in this highland region and countrywide. Key words: Tillage, soil properties, soil disturbance, volcanic soils.

Effects of freshwater inputs on soil quality in the Yellow River Delta, China

With the degradation or loss of coastal wetlands, more and more restoration projects have been widely conducted. Freshwater inputs have been proved to be an effective restoration way for degraded coastal wetlands. However, little information is available on the changes in soil quality caused by freshwater inputs. Soil samples were collected to a depth of 50 cm in freshwater restoration wetlands (FRW), tidal salt marshes with Suaeda salsa (SSM) and tidal salt marshes with Tamarix chinensis (TSM) in the Yellow River Delta, China, in August 2015, to investigate the changes in soil quality after freshwater inputs. Our results showed that soil salinity was significantly higher in natural wetlands than that in freshwater restoration wetlands (p < 0.05), while no significant differences in soil organic matter (SOM) were observed among three wetlands (p > 0.05). Cluster analysis and principal component analysis exhibited that soil samples in natural wetlands and freshwater restoration wetlands were clearly distinguished. Soil properties were screened and transformed to establish a soil quality index (SQI) for the assessment of soil quality. Soil salinity, SOM and silt were selected in the minimum data set in this study. Although there were no statistical differences in SQIs (p > 0.05), both linear SQI (SQIL) and non-linear SQI (SQINL) for three wetlands followed the order: SSM > FRW > TSM. And the SQIL values were lower compared with SQINL. The contributions of soil salinity to SQIL for three wetlands and SQINL for TSM and SSM were the highest in the minimum data for three wetlands, while SOM showed the highest contribution proportion of SQINL for FRW.

Soil physicochemical properties associated with quasi-circular vegetation patches in the Yellow River Delta, China

In recent years, decreased runoff and sediment, intensified storm surge and seawater intrusion, urbanization, petroleum exploration, and production, and other factors have gradually deteriorated the unique wetland ecosystem in the Yellow River Delta (YRD). Although previous studies have analyzed the relationships between vegetation and soil properties at different scales, few studies have documented quasi-circular vegetation patches (QVPs) in the YRD, which appear to exhibit faster succession rates that make them ideal for studies on the relationships between vegetation and soil properties. Therefore, this study investigated differences in soil physicochemical properties at 0–20 cm depths between QVPs and inter-QVP bare soil areas, among QVPs, and among plant species communities. Additionally, spatial variations in soil physicochemical properties were explored in south-north and west-east transects across and within QVPs. The results showed that soils beneath QVPs had significant fertility island effects associated with soil organic matter (SOM) and total nitrogen (TN). Furthermore, these areas were richer in clay content, showed slightly higher pH values, and exhibited less available phosphorus (APH), available potassium (APO), total salt content, and silt content than those of bare soil areas. A multiple independent samples nonparametric Kruskal-Wallis H test detected significant differences in SOM, TN, APH, and pH among 18 QVPs, but no significant differences were found in APO, total salt content, sand, silt, and clay contents. Regardless of plant species, different plant species communities had significant effects on soil physicochemical properties. Particularly, soils underneath plant species communities with Tamarix chinensis were richer in SOM and TN, and they contained less APH, APO, and total salt content than those without T. chinensis. In each QVP, values of SOM and TN in soil samples along the patch perimeter were less than those of samples located midway toward the perimeter, and these values were less than those of samples centered in the patch. However, APO and total salt content values exhibited opposite changes from the perimeter to the center of the patch. The results also indicated significant differences in SOM, TN, APH, APO, and pH between south-north transect A and west-east transect B across QVPs, but no significant differences were found in total salt content, sand, silt, and clay contents. Therefore, the results of this study indicate that QVPs have significant effects on topsoil nutrients and salinity but little effects on soil texture. Furthermore, the occurrence and development of QVPs are associated with suitable soil conditions, including higher clay fractions and lower total salt content values.

Stoichiometric Characteristics of Soil in Several Different Communities

The content of nitrogen, phosphorus, potassium and organic matter in soil is an important index to determine soil nutrient status. In this paper, the contents of nitrogen, phosphorus, potassium, organic matter and soil salt in the soil of several different plant communities in the campus were measured by the chemical measurement characteristics of several different communities in University of Jinan. The differences in the measurement characteristics of soil chemical measurement in different plant communities were analyzed. The results showed that the highest organic matter content in several communities was Cherry Blossom community, 76.33mg/kg, and the highest ammonium nitrogen content was 196.08mg/kg; the highest content of available phosphorus was the community of Begonia, 168.14mg/kg, and the highest content of available potassium was the community of Robinia pseudoacacia, which was the highest salt content in 64.99mg/kg soil. The community of cherry blossoms is 569 μs. There was little difference in soil organic matter, available phosphorus and available potassium in different plant communities..

Evaluating relationships between soil chemical properties and vegetation cover at different slope aspects in a reclaimed dump

Conducting research about the relationships between soil chemical properties and vegetation coverage at different slope aspects is especially important in reconstructed ecosystems of vulnerable ecological regions. This study was conducted in the first reclaimed dump within the Pingshuo mining area of Shanxi Province, China, to analyze patterns of soil chemical properties (soil organic matter (SOM), soil total nitrogen (STN), soil available phosphorus (SAP) and soil available potassium (SAp) and vegetation coverage (NDVI) and their correlations at different slope aspects. In the reclaimed dump, 26 quadrats were established along four slope aspects (i.e., shady, semi-shady, sunny and semi-sunny slopes). There was no significant difference in SOM or STN among different slope aspects, while SAP differed between shady slopes compared to semi-shady, sunny and semi-sunny slopes; SAP differed significantly between semi-shady and semi-sunny slopes. The NDVI of semi-sunny slopes differed significantly from that of the other three aspects. There was variation in the relationships between NDVI and soil chemical properties, depending on the slope aspects. The logarithm of SOM and NDVI was related linearly on shady and semi-shady slopes, while NDVI was inversely related to the natural logarithm of the logarithm of SOM on sunny and semi-sunny slopes. STN and NDVI had a first-order function relationship on shady and semi-shady slopes, yet a quadratic function relationship on sunny and semi-sunny slopes. The relationships between SAP and NDVI were inverse on all types of slopes. On shady and semi-shady slopes, NDVI had a quadratic relationship with the logarithm of SAp, but it was well fitted by using a cubic function on sunny and semi-sunny slopes. The sensitivity coefficients of soil chemical properties and NDVI were different, and soil chemical properties changed differently depending on changes in NDVI at different slope aspects.