Physical and mechanical properties and microstructures of submarine soils in the Yellow Sea

In recent years,the exploration of seabed has been intensified,but the submarine soils of silt and sand in the Yellow Sea area have not been well investigated so far.In this study,the physical and mechanical properties of silt and sand from the Yellow Sea were measured using a direct shear apparatus and their microstructures were observed using a scanning electron microscope.The test results suggest that the shear strength of silt and sand increases linearly with the increase of normal stress.Based on the direct shear test,the scanning electron microscope was used to observe the section surface of sand.It is observed that the section surface becomes rough,with many“V”‐shaped cracks.Many particles appear on the surface of the silt structure and tend to be disintegrated.The X‐ray diffraction experiment reveals that the sand and silt have different compositions.The shear strength of sand is slightly greater than that of silt under high stress,which is related to the shape of soil particles and the mineral composition.These results can be a reference for further study of other soils in the Yellow Sea;meanwhile,they can serve as soil parameters for the stability and durability analyses of offshore infrastructure construction.

Soil Physico-Chemical Properties and Different Altitudes Affect Arbuscular Mycorrhizal Fungi Abundance and Colonization in Cacao Plantations of Cameroon

This study aims to investigate the abundance of AMF according to soil properties and altitudes in different cacao plantations of Cameroon. Physico-chemical analyses were made on soil samples collected from three agro-ecological zones. Soil samples were also used to evaluate directly the AMF abundance following the various altitudes and after trapping by sorghum plant. The results showed that soil properties, AMF spore abundances and colonization fluctuated significantly at different altitudes. The most represented texture was sandy loam. The bimodal zone presented a homogeneous texture (sandy loam) in all its localities. Cacao soil chemical characteristics showed that, the highest nitrogen rate (0.47%;p 0.05, Scott-Knott test) was recorded at Melong in a monomodal zone while Tonga in the Western highlands displayed the lowest rate (0.13%). Soil P concentration was significantly high in monomodal zones (Mbanga and Melong). Soil pH level indicated that the soil from Tonga in the Western highlands was neutral (pH = 6.67), and soils of other localities under study were acidic with the lowest (4.75) pH level recorded at Melong in a monomodal zone. In soil samples, the highest spore density (1.03 spores/g soil) was observed at Ntui in Bimodal zone, while the lowest spore density (0.26 spores/g soil) was observed at Bafang in the Western highlands. Root colonization showed that the sample from Bokito in a bimodal zone displayed the best frequency of mycorrhization (86.11%) while the sample from Bafang in the Western highlands recorded the lowest (27.11%). The PCA analysis highlighted that available phosphorus, pH and altitude all strongly correlated with AMF root colonization ability and can be used as a predictor of AMF colonization ability in cacao rhizosphere.

Effect of salinization on soil properties and mechanisms beneficial to microorganisms in salinized soil remediation-a review

Salinized soil is an important reserved arable land resource in China.The management and utilization of salinized soil can safeguard the current size of arable land and a stable grain yield.Salt accumulation will lead to the deterioration of soil properties,destroy soil production potential and damage soil ecological functions,which in turn will threaten global water and soil resources and food security,and affect sustainable socio-economic development.Microorganisms are important components of salinized soil.Microbial remediation is an important research tool in improving salinized soil and is key to realizing sustainable development of agriculture and the ecosystem.Knowledge about the impact of salinization on soil properties and measures using microorganisms in remediation of salinized soil has grown over time.However,the mechanisms governing these impacts and the ecological principles for microbial remediation are scarce.Thus,it is imperative to summarize the effects of salinization on soil physical,chemical,and microbial properties,and then review the related mechanisms of halophilic and halotolerant microorganisms in salinized soil remediation via direct and indirect pathways.The stability,persistence,and safety of the microbial remediation effect is also highlighted in this review to further promote the application of microbial remediation in salinized soil.The objective of this review is to provide reference and theoretical support for the improvement and utilization of salinized soil.

Experimental investigation into the salinity effect on the physicomechanical properties of carbonate saline soil

For engineering structures with saline soil as a filling material,such as channel slope,road subgrade,etc.,the rich soluble salt in the soil is an important potential factor affecting their safety performance.This study examines the Atterberg limits,shear strength,and compressibility of carbonate saline soil samples with different NaHCO3 contents in Northeast China.The mechanism underlying the influence of salt content on soil macroscopic properties was investigated based on a volumetric flask test,a mercury intrusion porosimetry(MIP)test,and a scanning electron microscopic(SEM)test.The results demonstrated that when NaHCO3 contents were lower than the threshold value of 1.5%,the bound water film adsorbed on the surface of clay particles thickened continuously,and correspondingly,the Atterberg limits and plasticity index increased rapidly as the increase of sodium ion content.Meanwhile,the bonding force between particles was weakened,the dispersion of large aggregates was enhanced,and the soil structure became looser.Macroscopically,the compressibility increased and the shear strength(mainly cohesion)decreased by 28.64%.However,when the NaHCO3 content exceeded the threshold value of 1.5%,the salt gradually approached solubility and filled the pores between particles in the form of crystals,resulting in a decrease in soil porosity.The cementation effect generated by salt crystals increased the bonding force between soil particles,leading to a decrease in plasticity index and an improvement in soil mechanical properties.Moreover,this work provides valuable suggestions and theoretical guidance for the scientific utilization of carbonate saline soil in backfill engineering projects.

Effects of site preparation methods on soil physical properties and outplanting success of coniferous seedlings in boreal forests

This study assessed the effect of patch scarification and mounding on the physical properties of the root layer and the success of tree planting in various types of forests.This study was conducted on 12 forest sites in taiga forests of the European part of Russia.A total of 54 plots were set up to assess seedling survival;root collar diameter,height,and heigh increment were measured for 240 seedlings to assess growth.In the rooting layer,240 soil samples were taken to determine physical properties.The study showed that soil treatment methods had no effect on bulk density and total porosity in Cladina sites.However,reduced soil moisture was noted,particularly in mounds,resulting in increased aeration.In Myrtillus sites,there were increased bulk density,reduced soil moisture,and total porosity in the mounds.Mounding treatment in Polytrichum sites resulted in reduced soil moisture and increased aeration porosity.In the Myrtillus and Polytrichum sites,patch scarification had no effects on physical properties.In Polytrichum sites,survival rates,heights,and heigh increments of bareroot Norway spruce seedlings in mounds were higher than in patches;however,the same did not apply to diameter.In Cladina and Myrtillus sites,there was no difference in growth for bareroot and containerised seedlings with different soil treatments.Growing conditions and soil types should be considered when applying different soil treatment methods to ensure high survival rates and successful seedling growth.

Near-Surface Soil Chemical Properties as Affected by Cover Crops Over Time in the Lower Mississippi River Valley

Typical row-crop agricultural practices can potentially be harmful to soil health and future sustainability. The use of cover crops (CC) as a mechanism to improve soil health on a wide scale remains underutilized. Soil health remains a major concern for the sustainability of agricultural productivity, therefore, research into CC implementation as a mean to preserve or improve soil health is warranted. The objective of this study was to evaluate the effects of CC on the soils in the eastern Arkansas portion of the Lower Mississippi River Valley (LMRV) over time for various chemical soil parameters, including pH, soil organic matter (SOM), soil elemental contents (i.e., P, K, Ca, Mg, S, Na, Fe, Mn, Zn, Cu, and B), soil respiration, and a generalized soil health score index. Soil pH decreased over time under both CC and no-cover-crop (NCC) treatments, by −0.3 and −0.2, respectively. Soil OM decreased over time under NCC by −0.1%, but did not differ between CC treatments. Soil N availability decreased over time under NCC (−22.6 kg·ha−1), but did not change over time under CC. Soil respiration decreased over time under both CC and NCC, by −76.1 mg·L−1 and −77.3 mg·L−1, respectively, though there was no effect of CC treatment. The Haney soil health score index decreased under CC (−7.0) and NCC (−6.8) without an effect from CC treatment. Results of the study place emphasis on the temporal nature of soil health as influenced by cover crops and their potential to improve soil health.

Physico-Chemical Properties of Soils from Diguel and Koudalwa Tchad,and Phytoremediation Potentials of Acasia and Kinkeliba Plants in Removing Cr and Cu from These Soils

The aim of this study to investigate the physico-chemical properties of soils from Diguel and Koudalwa Tchad,and phytoremediation potentials of acasia and kinkeliba plants in removing Cr and Cu from these soils.Soil was sampled from the tannery plant in Diguel and agricultural land around crude oil activities in Koudalwa.Soils were characterized by the following properties:pH,(Electrical Conductivity),TDS(Total Dissolved Solids),salinity,bulk density,OM(Organic Matter),nitrate,phosphate,clay,silt,sand,and textural class.The acasia and kinkeliba plants were used to decontaminate Cu and Cr from sample soils for 30 days period.The bulk density of all the soil samples from Kouldawa was higher compared to Diguil,ranging from 1.421 to 1.64 g/cm^(3)compared to 1.21 to 1.51 g/cm^(3)for Diguel.Most of the soils in Kouldawa are mineral soils,while those of Diguel are mostly mineral soil with some organics.Diguel soils are richer in nitrate(577.9 to 2,687.32 mg/kg in Diguel and 33.64 to 197.64 mg/kg in Kouldawa)and phosphate than soils from Kouldawa.Soils from the studied areas are not saline except for a subsurface soil in Diguel(salinity,4.21;EC,4.280 dS/m;TDS,3,040 mg/L).The highest amount of Cr and Cu removed by acasia is 78%and 53.12%compared to 73.8%and 52.21%by kinkeliba.Diguel soil can be very suitable for agriculture and Kouldawa soils for construction.Acasia and kinkeliba can be effectively used to decontaminate the studied soils from heavy metal pollution.

Impact of Different Rates of Nitrogen Supplementation on Soil PhysicochemicalProperties and Microbial Diversity in Goji Berry

Goji berry(Lycium barbarum L.)is substantially dependent on nitrogen fertilizer application,which can signifi-cantly enhance fruit yield and Goji berry industrial development in Ningxia,China.This study aimed to analyze the functions of differential nitrogen application rates including low(N1),medium(N2),and high(N3)levels in soil microbial community structure(bacterial and fungal)at 2 diverse soil depths(0-20,20-40 cm)through high-throughput sequencing technology by targeting 16S RNA gene and ITS1&ITS2 regions.All the observed physicochemical parameters exhibited significant improvement(p<0.05)with increased levels of nitrogen and the highest values for most parameters were observed at N2.However,pH decreased(p<0.05)gradually.The alpha and beta diversity analyses for bacterial and fungal communities’metagenome displayed more similarities than differences among all groups.The top bacterial and fungal phyla and genera suggested no obvious(p>0.05)differences among three group treatments(N1,N2,and N3).Furthermore,the functional enrichment analysis demonstrated significant(p<0.05)enrichment of quorum sensing,cysteine and methionine metabolism,and transcriptional machinery for bacterial communities,while various saprotrophic functional roles for fungal communities.Conclusively,moderately reducing the use of N-supplemented fertilizers is conducive to increasing soil nitrogen utilization rate,which can contribute to sustainable agriculture practices through improved soil quality,and microbial community structure and functions.

Leguminosae plants play a key role in affecting soil physical-chemical and biological properties during grassland succession after farmland abandonment in the Loess Plateau,China

Leguminosae are an important part of terrestrial ecosystems and play a key role in promoting soil nutrient cycling and improving soil properties.However,plant composition and species diversity change rapidly during the process of succession,the effect of leguminosae on soil physical-chemical and biological properties is still unclear.This study investigated the changes in the composition of plant community,vegetation characteristics,soil physical-chemical properties,and soil biological properties on five former farmlands in China,which had been abandoned for 0,5,10,18,and 30 a.Results showed that,with successional time,plant community developed from annual plants to perennial plants,the importance of Leguminosae and Asteraceae significantly increased and decreased,respectively,and the importance of grass increased and then decreased,having a maximum value after 5 a of abandonment.Plant diversity indices increased with successional time,and vegetation coverage and above-and below-ground biomass increased significantly with successional time after 5 a of abandonment.Compared with farmland,30 a of abandonment significantly increased soil nutrient content,but total and available phosphorus decreased with successional time.Changes in plant community composition and vegetation characteristics not only change soil properties and improve soil physical-chemical properties,but also regulate soil biological activity,thus affecting soil nutrient cycling.Among these,Leguminosae have the greatest influence on soil properties,and their importance values and community composition are significantly correlated with soil properties.Therefore,this research provides more scientific guidance for selecting plant species to stabilize soil ecosystem of farmland to grassland in the Loess Plateau,China.

Soil seed bank is affected by transferred soil thickness and properties in the reclaimed coal mine in the Qilian Mountains, China

Reclamation of lands abandoned after mining in mountain areas is critical to erosion control,safety from landslides,and ecological protection of mountain ecosystems.However,little is known about alpine coal mine reclamation using the soil seed bank as a potential source for revegetation.We collected samples of persistent soil seed bank for germination experiments from nine reclaimed sites with different soil cover thicknesses and from six control sites in the Qilian Mountains of China.Soil properties of each site were determined(including soil water content,soil available potassium,soil available phosphorus,soil total nitrogen,pH,soil organic matter,soil total phosphorus,and soil total potassium,and soil alkali-hydrolyzable nitrogen),and the relationships of the characteristics of the soil seed bank with soil cover thickness and soil properties were examined.The results showed that the density,number of species,and diversity of the topsoil seed bank were significantly correlated with soil cover thickness,and all increased with the increment of soil cover thickness.Soil cover thickness controlled the soil seed bank by influencing soil properties.With the increase in soil cover thickness,soil properties(e.g.,soil organic matter,soil total nitrogen,etc.)content increased while soil pH decreased.The soil seed bank had the potential to restored the pre-mining habitat at reclaimed sites with approximately 20-cm soil cover thickness.Soil properties of reclaimed sites were lower than that of natural sites.The relationship between the soil seed bank and soil cover thickness determined in this study provides a foundation for improving reclamation measures used in coal mines,as well as for the management and monitoring of reclaimed areas.

Unraveling the hydraulic properties of loess for landslide prediction:A study on variations in loess landslides in Lanzhou,Dingxi,and Tianshui,China

Loess has distinctive characteristics,leading to frequent landslide disasters and posing serious threats to the lives and properties of local re sidents.The involvement of water repre sents a critical factor in inducing loess landslides.This study focuses on three neighboring cities sequentially situated on the Loess Plateau along the direction of aeolian deposition of loess,namely Lanzhou,Dingxi,and Tianshui,which are densely populated and prone to landslide disasters.The variations in hydraulic properties,including water retention capacity and permeability,are investigated through Soil Water Characteristic Curve(SWCC)test and hydraulic conductivity test.The experimental findings revealed that Tianshui loess exhibited the highest water retention capacity,followed by Dingxi loess,while Lanzhou loess demonstrated the lowest water retention capacity.Contrastingly,the results for the saturated permeability coefficient were found to be the opposite:Tianshui loess showed the lowest permeability,whereas Lanzhou loess displayed the highest permeability.These results are supported and analyzed by scanning electron microscopy(SEM)observation.In addition,the water retention capacity is mathematically expressed using the van Genuchten model and extended to predict unsaturated hydraulic properties of loess.The experimental results exhibit a strong accordance with one another and align with the regional distribution patterns of disasters.

Digital mapping of soil physical and mechanical properties using machine learning at the watershed scale

Knowledge about the spatial distribution of the soil physical and mechanical properties is crucial for soil management,water yield,and sustainability at the watershed scale;however,the lack of soil data hinders the application of this tool,thus urging the need to estimate soil properties and consequently,to perform the spatial distribution.This research attempted to examine the proficiency of three machine learning methods(RF:Random Forest;Cubist:Regression Tree;and SVM:Support Vector Machine)to predict soil physical and mechanical properties,saturated hydraulic conductivity(Ks),Cohesion measured by fall-cone at the saturated(Psat)and dry(Pdry)states,hardness index(HI)and dry shear strength(SS)by integrating environmental variables and soil features in the Zayandeh-Rood dam watershed,central Iran.To determine the best combination of input variables,three scenarios were examined as follows:scenarioⅠ,terrain attributes derivative from a digital elevation model(DEM)+remotely sensed data;scenarioⅡ,covariates of scenarioⅠ+selected climatic data and some thematic maps;scenarioⅢ,covariates in scenarioⅡ+intrinsic soil properties(Clay,Silt,Sand,bulk density(BD),soil organic matter(SOM),calcium carbonate equivalent(CCE),mean weight diameter(MWD)and geometric weight diameter(GWD)).The results showed that for Ks,Psat Pdry and SS,the best performance was found by the RF model in the third scenario,with R2=0.53,0.32,0.31 and 0.41,respectively,while for soil hardness index(HI),Cubist model in the third scenario with R2=0.25 showed the highest performance.For predicting Ks and Psat,soil characteristics(i.e.clay and soil SOM and BD),and land use were the most important variables.For predicting Pdry,HI,and SS,some topographical characteristics(Valley depth,catchment area,mltiresolution of ridge top flatness index),and some soil characteristics(i.e.clay,SOM and MWD)were the most important input variables.The results of this research present moderate accuracy,however,the methodology employed provides quick and costeffective information serving as the scientific basis for decision-making goals.

Influence of different soil properties on the failure behavior of deposit slope under earthquake after rainfall

In this study,the influence of soil properties on the failure behavior and mechanism of slope under earthquake after rainfall was studied with shaking table test in the laboratory,in which the failure process of slope and instant responses of water content and pore water pressure were tested.Based on the principle of similarity,a model test was designed.The experimental results showed that soil properties exhibit significant influence on failure mode and failure mechanism of slope.Local flowslide,local failure,and creep flowslide failure modes appear in the slope exposed to only rainfall.However,under earthquake after rainfall,the other three failure modes occur,i.e.,local slip failure,overall slip failure,and shallow scouring and creep flowslide failure.The spatial distribution of water content and pore water pressure are the two key factors leading to slope failure.Furthermore,due to the difference of permeability,the soil properties not only affect the spatial distribution of water content of the slope after rainfall,resulting in the peak pore water pressure which occurs mainly near the foot of the slope and near the bedrock interface in the middle and lower parts of the slope,but also affect the dissipation of excess pore water pressure in the process of earthquake.Finally,it is discovered that different types of soil lead to significant differences in the peak acceleration of slope failure.The critical acceleration of slope with coarse-grained soil is greater than that of slope with fine-grained soil.The critical acceleration of slope failure shows a close relationship with soil properties.

Mechanical properties of dredged soil reinforced by xanthan gum and fibers

Biopolymers have become popular in geotechnical engineering as they provide a carbon-neutral alternative for soil solidification.Xanthan gum(XG)and jute fiber(JF)were selected to solidify the Yellow River dredged soil.The mechanical behavior of solidified dredged soil(SDS)was investigated using a series of uniaxial compression and splitting tension tests at different XG and JF contents and fiber lengths.The results indicate that on the 28th day,the unconfined compressive strength(UCS)values of SDS samples reached 2.83 MPa and splitting tensile strength(STS)of 0.763 MPa at an XG content of 1.5%.When the JF content was greater than 0.9%,the STS of the SDS samples decreased.This is because that the large fiber content weakened the cementation ability of XG.The addition of JF can significantly increase the strain at peak strength of SDS samples.There is a linear relationship between the UCS and STS of the dredged soils solidified by XG and JF.Microanalysis shows that the strength of SDS samples was improved mainly via the cementation of XG itself and the network structure formed by JF with soil particles.The dredged soil reinforced by XG and JF shows better mechanical performance and has great potential for application.

Effects of Different Planting Years on Physicochemical Properties and Enzyme Activities in Soil of Rice-Cherry Tomato Rotation

Crop rotation periodicity has always been one of the research focuses currently. In this study, the physicochemical properties, nutrient contents and enzyme activities were investigated in soils from rice-cherry tomato rotation for one year (1a), three years (3a), five years (5a), seven years (7a) and ten years (10a), respectively. The major objective was to analyze the optimal rotation years of rice-cherry tomato from soil perspective, so as to provide theoretical basis for effectively avoiding continuous cropping obstacles of cherry tomato via studying the response characteristics of soil physicochemical properties, nutrient contents and enzyme activities to planting years of rice-cherry tomato rotation system. The results were as follows: 1) Soil pH value was increased year by year during 1a to 5a, reached the highest value 5.32 at 5a. However, soil acidity was sharply enhanced during 7a to 10a (P P •kg-1 at 5a. 3) The content of soil available phosphorus was increased year by year with increasing of crop rotation years, and increased by 110% to 173% during 3a to 10a (P P P < 0.05). In conclusion, long-term single rotation pattern of rice-cherry tomato would aggravate soil acidification, prompt soil nutrient imbalance and reduce soil enzyme activity. 5a to 7a would be the appropriate rotation period for rice-cherry tomato, or else it would reduce soil quality, resulting in a new continuous cropping obstacle of cherry tomato.

GIS-Based Assessment of Soil Chemical and Physical Properties as a Basis for Land Reclamation in Toshka Area, Aswan, EGYPT

The accurate assessment of soil properties is a crucial factor for composing and implementing reclamation plans. The main objective of this study was to evaluate soil chemical and physical properties and calculate the chemical and fertility index for assisting land reclamation in Toshka area. The Toshka area is located between latitudes 31°32'N and 31°36'N and longitudes 32°40'E and 32°60'E. GIS was used to select 16 sites. The results revealed the soil has undesirable characteristics. The soil pH ranged from slightly alkaline to moderately alkaline. Furthermore, it was characterized as saline (with a ECe of 4.65 - 11.45 dS⋅m−1) and moderately calcareous soil (with CaCO3 at 11.85% - 17.20%). The soil had a low soil organic matter content which did not exceed 0.18%. The soil was dominated by a sandy loam texture (62.50%) followed by a sandy clay loam texture (18.75%). The bulk density, total soil porosity and saturated hydraulic conductivity values varied with 1.38 - 1.55 Mg⋅cm−3, 41.85% - 48.45% and 1.20 - 3.34 cm⋅h−1, respectively. The chemical index ranged from low to moderate quality. The correlations between the parameters osculated between negative and positive. Therefore, the soil may be reclaimed if the soil properties are improved and crop selection is optimized for this soil.

Re-Examining Field-Surveyed Variations in Elevation and Soil Properties with a 1-m Resolution LiDAR-Generated DEM

This article presents a 2017 LiDAR-DEM guided 1-m resolution examination of field-surveyed elevation and soil property variations (5 × 5 m spacings) conducted in 1977 across a hummocky New Brunswick field used for potato production. This examination revealed that the field incurred minor elevation differences likely due to upslope erosion as revealed through increasing Sand % and CF % with increasing elevation, and increasing Silt % along low-lying areas. Soil moisture, field capacity, permanent wilting and nitrate nitrogen (NO3-N) also increased at downslope locations. Directly as well as indirectly, soil pH, ammonium nitrogen (NH4-N), Caesium137 (Cs137) and Mehlich-3 extracted Ca, Mg, K, Fe, Mn, Cu, and Zn were likewise affected by topographic location. Factor analyzing these variables led to: 1) a Soil Loss Factor that captured 24% of the textural variations;2) a Soil-Cropping Factor accounting for 16% of the N, P, K, Ca, Mg, Mn variations;3) a Soil Organic Matter (SOM) Factor relating 9% of the in-field variations for SOM, Fe, Zn, Cu to via organo-metal complexation and low NO3-N retention. Many of the topographic variations increased or decreased with the metric DEM-projected depth-to-water index (DTW) index. This index was set to 0 along DEM-derived flow channels with minimum upslope flow-accumulation areas of 0.1, 0.25, 0.5, 1 or 4 ha. Among these, the DTW > 4 ha threshold was useful for reproducing the textural variations, while the DTW > 0.25 ha threshold assisted in capturing trends pertaining to moisture retention and elemental concentrations.

Dietary Supplementation of <i>κ</i>-Carrageenan to Improve the Physio-Chemical and Functional Properties of White Bread

Fiber intake improves gut health and prevents non-communicable diseases. The current study investigates the substitution of carrageenan in white bread and evaluates its effect on the physiochemical and structural characteristics of bread. The 100% wheat flour was used as control and the test sample contained 4% carrageenan. The physio-chemical analysis showed that carrageenan-substitution improved the hydration properties of the flour (WHC—1.33 g/g;SC—3.50 ml/g). Carrageen substituted bread had reduced the loaf volume. The fiber content in carrageenan-substituted bread was noticeably higher (9.4 g%) than control (3.5 g%). Crude lipid (4.6 g%) and protein (7.0 g%) content improved with carrageenan-substitution. The mineral contents (Na, K, Mg, Ca, Fe, and Zn) were increased in carrageenan-breads. The texture profile analysis showed a decreased hardness (H1—92.3 N, H2—62.5 N) and improved springiness (5.3 mm) in carrageenan-bread.

Composition and properties of soil humus in a mixed forest of Cunninghamia lanceolata and Tsoongiodendron odorum

This study was conducted in Xinkou Experimental Forestry Farm of Fujian Agricultural and Forestry University, Sanming, Fujian Province in January 1999. Taking pure stand of Chinese fir as control, the authors measured and studied the content of organic carbon, content of humic acid (HA), ratio of HA to fulvic acid (FA), and the characteristics of infrared light spectrum and visible light spectrum of soil humus in the mixed forest of Chinese fir and Tsoong?tree. Compared to humus composition in the pure stand of Chinese fir, the content of soil organic C, HA content, and the E4 value of HA for different layers of soil, except for the ratio of HA to FA, showed a significant increase in the mixed forest, while the ratios of E4 to E6 had a little decrease. The infrared light spectrum of humic acid had an absorptive peak at 1650 cm-1. It is concluded that the levels of humification and aromaticity of soil humus are higher in the mixed forest, which is favorable for the improvement of soil structure and nutrient supply, thus improving the soil fertility to a certain degree.

Effects of Artificial Vegetation Restoration on Soil Physicochemical Properties in Southern Edge of Mu Us Sandy Land

[Objective] This study aimed to investigate the artificial vegetations on soil physicochemical properties of sandy land. [Method] The soil physicochemical proper- ties in five representative lands respectively covered by Artemisia ordosica, Salix cheilophila, Hedysarum scoparium, Populus simonii and Amorpha fruticosa, all of which were planted artificially at the same year were measured in the present study, using a bare soil as the control. [Result] Artificial vegetation improved the soil physicochemical properties by different extents in the lands covered by different plants. The soil physicochemical properties such as bulk density under A. Fruticosa and H. Scoparium were improved greatly. The frequency distribution of soil particle size under artificial vegetations exhibited a bimodal curve. The average soil particle size under A. fruticosa was the smallest, and the soil was very poorly sorted. The soil nutrients in the sandy land were not significantly improved by artificial vegeta- tion. [Conclusion] Artificial vegetation has a certain impact on soil properties in sandy land, as it greatly improves the soil physical properties but not the chemical properties.