The most important parameter affecting ground-penetrating radar （GPR） measurements is the complex effective relative permittivity εr^＊,eff because it controls the propagation velocity and the reflection of GPR pul...The most important parameter affecting ground-penetrating radar （GPR） measurements is the complex effective relative permittivity εr^＊,eff because it controls the propagation velocity and the reflection of GPR pulses. Knowing εr^＊,eff of soils passed through by electromagnetic waves increases accuracy in soil thickness and interface identification. Complex effective relative permittivity εr^＊,eff= εr^＊,eff - jεr^＊,effof 25 soil samples with textures ranging from loamy sand to silty clay was measured using the two-electrode parallelplate method. The measurements were conducted at defined water contents for frequencies from 1 MHz to 3 GHz. The results confirm the frequency dependence of εr^＊,eff and show that the dielectric behavior of soil-water mixtures is a function of water content. Applying the experimental data of this study with predictions based on the empirical model by Toppet aL （1980）, we find that Topp et aL＇s curve tends to underestimate the real part of εr^＊,eff measured. Along with frequency and water content, soil texture and organic matter affect soil permittivity. Moreover, the real part of εr^＊,eff increases at higher dry bulk densities. Output from our calibration model enables us to predict εr^＊,eff for the soil samples which were tested under the actual in situ soil water content. This results in high accuracy of soil thickness prediction.展开更多
Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims ...Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims to investigate the influence of plant roots on the tensile strength of soil.For this investigation,Amorpha fruticose was selected due to its large root diameter and the ease of root extraction.Indoor tensile tests were conducted on individual roots and root-soil complexes under three varying factors.The results indicate a power law relationship between root diameter and tensile strength.Increased root content and dry density notably enhance the tensile strength of the root-soil complex while roots mitigate damage associated with soil brittleness.When root content increases from 0 to 10,the maximum enhancement in tensile strength of the root-soil complex reaches 42.3 kPa.The tensile strength of the root-soil complex at a dry density of 1.7 g/cm^(3)is four to five times greater than that of the complex at a dry density of 1.4 g/cm^(3).Moreover,as moisture content increases,the tensile strength of the root-soil complex initially rises before declining,with an increase range of 7.7-35.8 kPa.These findings provide a scientific basis for understanding the role of vegetation roots in soil tensile strength and for guiding slope reinforcement strategies.展开更多
The research presents the first results of aluminium speciation analysis in aqueous extracts of individual plant parts of Betula pendula and soil samples, using High Performance Ion Chromatography with Diode Array Det...The research presents the first results of aluminium speciation analysis in aqueous extracts of individual plant parts of Betula pendula and soil samples, using High Performance Ion Chromatography with Diode Array Detection（HPIC-DAD）. The applied method allowed us to carry out a full speciation analysis of aluminium in the form of predominant aluminium–fluoride complexes： AlF（（x = 2,3,4））^（（3-x））（first analytical signal）, AlF^（2＋）（second analytical signal） and Al^（3＋）（third analytical signal） in samples of lateral roots, tap roots, twigs, stem, leaf and soil collected under roots of B. pendula. Concentrations of aluminium and its complexes were determined for two types of environment characterised by different degree of human impact：contaminated site of the Chemical Plant in Luboń and protected area of the Wielkopolski National Park. For all the analysed samples of B. pendula and soil, AlF（（x = 2,3,4））^（（3-x））had the largest contribution, followed by Al^（3＋）and AlF^（2＋）. Significant differences in concentration and contribution of Al–F complexes and Al^（3＋）form, depending on the place of sampling（different anthropogenic pressure） and plant part of B. pendula were observed. Based on the obtained results, it was found that transport of aluminium is ＂blocked＂ by lateral roots, and is closely related to Al content of soil.展开更多
The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The...The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.展开更多
Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mech...Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mechanical and physical properties such as shear strength, compressibility, shrinkage and swelling potentials. Although, several studies have been conducted regarding the land use effects on various soil mechanical properties, little is known about the effects of land use and slope positions on Atterberg limits and consistency indices. This study was conducted to investigate the effects of land use and slope position on selected soil physical and chemical properties, Atterberg limits and consistency indices in hilly region of western Iran. Three land uses including dryland farming, irrigated farming and pasture and four slope positions(i.e., shoulder, backslope, footslope, and toeslope) were used for soil samplings. One hundred eleven soil samples were collected from the surface soil(0-10 cm). Selected physical and chemical properties, liquid limit(LL), plastic limit(PL) and shrinkage limit(SL) were measured using the standard methods; and consistency indices including plastic index(PI), friability index(FI), shrinkage index(SI) and soil activity(A=PI/clay) were calculated. The results showed that irrigated farming significantly increased organic matter content(OM) and OM/clay ratio, and decreased bulk density(ρb) and relative bulk density(ρb-rel) as a result of higher biomass production and plant residues added to the soil compared to other land uses. Except for sand content, OM, ρb, cation exchange capacity(CEC) and calcium carbonate equivalent(CCE), slope position significantly affected soil physical and chemical properties. The highest values of silt, OM/clay and CEC/clay were found in the toeslope position, predominantly induced by soil redistribution within the landscape. The use of complexed(COC)- noncomplexed organic carbon(NCOC) concept indicated that majority of the studied soils were located below the saturation line and the OM in the soils was mainly in the COC form. The LL, PI, FI and A showed significant differences among the land uses; the highest values belonged to the irrigated farming due to high biomass production and plant residues returned to the soils. Furthermore, slope position significantly affected the Atterberg limits and consistency indices except for SL. The highest values of LL, PI, SI and A were observed in the toeslope position probably because of higher OM and CEC/clay due to greater amount of expandable phyllosilicate clays. Overall, soils on the toeslope under irrigated farming with high LL and SI and low values of FI need careful tillage management to avoid soil compaction.展开更多
Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morpholo...Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morphological indicators, and analyzes the soil crack＇s morphological features under various development degrees. By statistic analysis, three quantitative indicators for surface morphology are selected, namely soil crack area density, area weighted mean fractal dimension and connectivity index R, which can not only express the development intensity of soil cracks, but also effectively describe its morphological complexity and connectivity. The research results set a good base for the establishment of soil crack assessment system in Yuanmou arid-hot valley region.展开更多
The Tangba high slope is mainly composed of coarse soils and supplies core wall materials for the construction of the Changheba dam. Since the filling intensity of the Changheba dam is high, the Tangba high slope suff...The Tangba high slope is mainly composed of coarse soils and supplies core wall materials for the construction of the Changheba dam. Since the filling intensity of the Changheba dam is high, the Tangba high slope suffers from a high-intensity excavation process, and reinforcement measures are usually not implemented immediately. Moreover, the distribution of useful materials is uneven and insufficient, and the mixing of different soil materials is necessary; thus, multiple simultaneous excavations and secondary excavation are inevitable. In the construction period from 2012 to 2016, large deformations occurred in this area, and one of the largest monitored horizontal deformations whose direction points to the opposite side of the valley even reached more than 8000 mm. According to field investigation, site monitoring and theoretical analysis, the large deformation in the Tangba high slope can be divided into two phases. In the first phase, the excavation construction breaks the original stress equilibrium state; in the second phase, the precipitation infiltration accelerates the deformation. Thus, the excavation construction and precipitation infiltration are the two major factors promoting the deformation, and the high-intensity and complex excavation process is the fundamental cause. Notably, rate of slope deformation significantly accelerated in rainy seasons due to precipitation infiltration; the rate also accelerated in early 2016 due to the high-intensity, complex excavation process. Comprehensively considering the above factors, timely and effective reinforcement measures are essential.展开更多
Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P ...Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P desorption and the relationship between phosphate sorption and desorption. Among the soil series, the Ghior soil had the highest percent clay (59.32%) and free iron oxide (15241 mg·kg–1) content. Along the catena of the calcareous soils, percent clay contents increased. For sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 mg·P·L–1 solution. For desorption, three extractants namely, SO42- (0.005 M) as Na2SO4, HCO3- (0.01 M) as NaHCO3 and distilled water were used at extractant to soil ratios of 30:1, 60:1 and 100:1 (v/w). Among the sorption equations, the Langmuir equation showed better fit to the sorption data at higher P concentrations. The amount of phosphate desorbed by all the three extractants increased significantly with the increasing extractant to soil ratios. Phosphate desorption by and water molecules was highly correlated with pH, percent clay and free iron oxide content of the soil. Significant positive correlation (r > 0.64, P L). Phosphate desorption by SO42- and water molecules was also positively correlated with Freundlich constant, N (r > 0.67, P 0 (r > 0.72, P –0.77, P L). The results suggest that freshly sorbed phosphate ions (inner-sphere complex forming species) can be readily desobed by outer-sphere complex forming species like sulphate and bicarbonate ions. Water molecules also desorbed significant amount of freshly sorbed phosphate from the soil colloids.展开更多
Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical re...Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical regions. Soil health is fundamental to the sustainable development of rubber plantations. The objective of the study is to explore the influence of different complex ecological cultivation modes on the stability of soil aggregates in rubber based agroforestry systems. In this study, the ecological cultivation mode of rubber—Alpinia oxyphylla plantation, the ecological cultivation mode of rubber—Phrynium hainanense plantations, the ecological cultivation mode of rubber—Homalium ceylanicum plantations and monoculture rubber plantations were selected, and the particle size distribution of soil aggregates and their water stability characteristics were analyzed. The soil depth of 0 - 20 cm and 20 - 40 cm was collected for four cultivation modes. Soil was divided into 6 particle levels > 20 cm. soil was divided into 6 particle levels > 5 mm, 2 - 5 mm, 1 - 2 mm, 0.5 - 1 mm, 0.25 - 0.5 mm, and 0.053 - 0.25 mm according to the wet sieve method. The particle size proportion and water stability of soil aggregates were determined by the wet sieve method. The particle size proportion and water stability of soil aggregates under different ecological cultivation modes were analyzed. The results showed that under different ecological cultivation modes in the shallow soil layer (0 - 20 cm), the rubber—Alpinia oxyphylla plantation and the rubber—Phrynium hainanense plantation promoted the development of dominant soil aggregates towards larger size classes, whereas the situation is the opposite for rubber—Homalium ceylanicum plantation. In soil layer (20 - 40 cm), the ecological cultivation mode of rubber—Phrynium hainanense plantation developed the dominant radial level of soil aggregates to the diameter level of large aggregates. Rubber—Alpinia oxyphylla plantation and rubber—Homalium ceylanicum plantation, three indicators, including the water-stable aggregate content R<sub>0.25</sub> (>0.25 mm water-stable aggregates), mean weight diameter (MWD), and geometric mean diameter (GMD), were all lower than those in the rubber monoculture mode. However, in the rubber—Phrynium hainanense plantation, the water-stable aggregate content R<sub>0.25</sub>, mean weight diameter, and geometric mean diameter were higher than in the rubber monoculture mode, although these differences did not reach statistical significance.展开更多
The repeated effects of vulnerable habitat and unreasonable human activities on the Bashang Plateau of China led the chestnut soil to degrade. It expresses in reducing soil CEC, decreasing nutrient content, decomposi...The repeated effects of vulnerable habitat and unreasonable human activities on the Bashang Plateau of China led the chestnut soil to degrade. It expresses in reducing soil CEC, decreasing nutrient content, decomposing organic complexes, and reducing humus in loose, steady and tight bond forms, respectively. The percentage of three forms are 21%—34%, 44%—55% and 5%—6.2%, respectively.展开更多
基金supported by the German Research Foundation (DFG) (No. SFB 299)
文摘The most important parameter affecting ground-penetrating radar （GPR） measurements is the complex effective relative permittivity εr^＊,eff because it controls the propagation velocity and the reflection of GPR pulses. Knowing εr^＊,eff of soils passed through by electromagnetic waves increases accuracy in soil thickness and interface identification. Complex effective relative permittivity εr^＊,eff= εr^＊,eff - jεr^＊,effof 25 soil samples with textures ranging from loamy sand to silty clay was measured using the two-electrode parallelplate method. The measurements were conducted at defined water contents for frequencies from 1 MHz to 3 GHz. The results confirm the frequency dependence of εr^＊,eff and show that the dielectric behavior of soil-water mixtures is a function of water content. Applying the experimental data of this study with predictions based on the empirical model by Toppet aL （1980）, we find that Topp et aL＇s curve tends to underestimate the real part of εr^＊,eff measured. Along with frequency and water content, soil texture and organic matter affect soil permittivity. Moreover, the real part of εr^＊,eff increases at higher dry bulk densities. Output from our calibration model enables us to predict εr^＊,eff for the soil samples which were tested under the actual in situ soil water content. This results in high accuracy of soil thickness prediction.
基金The authors would like to acknowledge financial support from the Joint Funds of the National Nature Science Foundation of China(No.U22A20232)Supported by Open Project Funding of Key Laboratory of Intelligent Health Perception and Ecological Restoration of Rivers and Lakes,Ministry of Education(HGKFZ07)+2 种基金the National Natural Science Foundation of China(No.51978249)Innovation Research Team Project of the Hubei Provincial Department of Science and Technology(JCZRQT202500027)the International Collaborative Research Fund for Young Scholars in the Innovation Demonstration Base of Ecological Environment Geotechnical and Ecological Restoration of Rivers and Lakes.
文摘Plant root systems serve as a natural reinforcing material,significantly improving soil stability.Furthermore,the tensile strength of soil is crucial in mitigating the formation of cracks.Consequently,this study aims to investigate the influence of plant roots on the tensile strength of soil.For this investigation,Amorpha fruticose was selected due to its large root diameter and the ease of root extraction.Indoor tensile tests were conducted on individual roots and root-soil complexes under three varying factors.The results indicate a power law relationship between root diameter and tensile strength.Increased root content and dry density notably enhance the tensile strength of the root-soil complex while roots mitigate damage associated with soil brittleness.When root content increases from 0 to 10,the maximum enhancement in tensile strength of the root-soil complex reaches 42.3 kPa.The tensile strength of the root-soil complex at a dry density of 1.7 g/cm^(3)is four to five times greater than that of the complex at a dry density of 1.4 g/cm^(3).Moreover,as moisture content increases,the tensile strength of the root-soil complex initially rises before declining,with an increase range of 7.7-35.8 kPa.These findings provide a scientific basis for understanding the role of vegetation roots in soil tensile strength and for guiding slope reinforcement strategies.
基金supported by the National Science Centre, Poland through research project DEC-2012/07/D/NZ8/01030
文摘The research presents the first results of aluminium speciation analysis in aqueous extracts of individual plant parts of Betula pendula and soil samples, using High Performance Ion Chromatography with Diode Array Detection（HPIC-DAD）. The applied method allowed us to carry out a full speciation analysis of aluminium in the form of predominant aluminium–fluoride complexes： AlF（（x = 2,3,4））^（（3-x））（first analytical signal）, AlF^（2＋）（second analytical signal） and Al^（3＋）（third analytical signal） in samples of lateral roots, tap roots, twigs, stem, leaf and soil collected under roots of B. pendula. Concentrations of aluminium and its complexes were determined for two types of environment characterised by different degree of human impact：contaminated site of the Chemical Plant in Luboń and protected area of the Wielkopolski National Park. For all the analysed samples of B. pendula and soil, AlF（（x = 2,3,4））^（（3-x））had the largest contribution, followed by Al^（3＋）and AlF^（2＋）. Significant differences in concentration and contribution of Al–F complexes and Al^（3＋）form, depending on the place of sampling（different anthropogenic pressure） and plant part of B. pendula were observed. Based on the obtained results, it was found that transport of aluminium is ＂blocked＂ by lateral roots, and is closely related to Al content of soil.
基金Supported by China National Natural Science Foundation(Nos.21071102 and 91126013)Joint Funds of China National Natural Science Foundation and China Academy of Engineering Physics(No.10476015)National Fund of China for Fostering Talents in Basic Science(No.J1210004)
文摘The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.
基金Isfahan University of Technology for the financial support of this study
文摘Atterberg limits and consistency indices are used for classifications of cohesive(fine-grained) soils in relation with compaction and tillage practices. They also provide information for interpreting several soil mechanical and physical properties such as shear strength, compressibility, shrinkage and swelling potentials. Although, several studies have been conducted regarding the land use effects on various soil mechanical properties, little is known about the effects of land use and slope positions on Atterberg limits and consistency indices. This study was conducted to investigate the effects of land use and slope position on selected soil physical and chemical properties, Atterberg limits and consistency indices in hilly region of western Iran. Three land uses including dryland farming, irrigated farming and pasture and four slope positions(i.e., shoulder, backslope, footslope, and toeslope) were used for soil samplings. One hundred eleven soil samples were collected from the surface soil(0-10 cm). Selected physical and chemical properties, liquid limit(LL), plastic limit(PL) and shrinkage limit(SL) were measured using the standard methods; and consistency indices including plastic index(PI), friability index(FI), shrinkage index(SI) and soil activity(A=PI/clay) were calculated. The results showed that irrigated farming significantly increased organic matter content(OM) and OM/clay ratio, and decreased bulk density(ρb) and relative bulk density(ρb-rel) as a result of higher biomass production and plant residues added to the soil compared to other land uses. Except for sand content, OM, ρb, cation exchange capacity(CEC) and calcium carbonate equivalent(CCE), slope position significantly affected soil physical and chemical properties. The highest values of silt, OM/clay and CEC/clay were found in the toeslope position, predominantly induced by soil redistribution within the landscape. The use of complexed(COC)- noncomplexed organic carbon(NCOC) concept indicated that majority of the studied soils were located below the saturation line and the OM in the soils was mainly in the COC form. The LL, PI, FI and A showed significant differences among the land uses; the highest values belonged to the irrigated farming due to high biomass production and plant residues returned to the soils. Furthermore, slope position significantly affected the Atterberg limits and consistency indices except for SL. The highest values of LL, PI, SI and A were observed in the toeslope position probably because of higher OM and CEC/clay due to greater amount of expandable phyllosilicate clays. Overall, soils on the toeslope under irrigated farming with high LL and SI and low values of FI need careful tillage management to avoid soil compaction.
基金the National Natural Science Foundation of China (30470297)the National Key Technologies Research and Development Program in the Eleventh Five-Year Plan of China (2006BAC01A11)the Youth Foundation of Institute of Mountain Hazards and Environment of Chinese Academy of Sciences
文摘Quantification of complicated surface morphology of soil crack is a prerequisite and key to soil crack study. This paper takes soil crack quads in Yuanmou arid-hot valley region as examples, selecting several morphological indicators, and analyzes the soil crack＇s morphological features under various development degrees. By statistic analysis, three quantitative indicators for surface morphology are selected, namely soil crack area density, area weighted mean fractal dimension and connectivity index R, which can not only express the development intensity of soil cracks, but also effectively describe its morphological complexity and connectivity. The research results set a good base for the establishment of soil crack assessment system in Yuanmou arid-hot valley region.
基金the support of the National Key R&D Program of China(2017YFC1501102)the Youth Science and Technology Fund of Sichuan Province(2016JQ0011)the Key Project of the Power Construction Corporation of China(ZDZX-5)
文摘The Tangba high slope is mainly composed of coarse soils and supplies core wall materials for the construction of the Changheba dam. Since the filling intensity of the Changheba dam is high, the Tangba high slope suffers from a high-intensity excavation process, and reinforcement measures are usually not implemented immediately. Moreover, the distribution of useful materials is uneven and insufficient, and the mixing of different soil materials is necessary; thus, multiple simultaneous excavations and secondary excavation are inevitable. In the construction period from 2012 to 2016, large deformations occurred in this area, and one of the largest monitored horizontal deformations whose direction points to the opposite side of the valley even reached more than 8000 mm. According to field investigation, site monitoring and theoretical analysis, the large deformation in the Tangba high slope can be divided into two phases. In the first phase, the excavation construction breaks the original stress equilibrium state; in the second phase, the precipitation infiltration accelerates the deformation. Thus, the excavation construction and precipitation infiltration are the two major factors promoting the deformation, and the high-intensity and complex excavation process is the fundamental cause. Notably, rate of slope deformation significantly accelerated in rainy seasons due to precipitation infiltration; the rate also accelerated in early 2016 due to the high-intensity, complex excavation process. Comprehensively considering the above factors, timely and effective reinforcement measures are essential.
文摘Establishment of phosphate (P) retention and release capacity of soils is essential for effective nutrient management and environmental protection. In this experiment, we studied the influence of soil properties on P desorption and the relationship between phosphate sorption and desorption. Among the soil series, the Ghior soil had the highest percent clay (59.32%) and free iron oxide (15241 mg·kg–1) content. Along the catena of the calcareous soils, percent clay contents increased. For sorption study, the soils were equilibrated with 0.01 M CaCl2 solution containing 0, 1, 2, 4, 8, 16, 25, 50, 100 and 150 mg·P·L–1 solution. For desorption, three extractants namely, SO42- (0.005 M) as Na2SO4, HCO3- (0.01 M) as NaHCO3 and distilled water were used at extractant to soil ratios of 30:1, 60:1 and 100:1 (v/w). Among the sorption equations, the Langmuir equation showed better fit to the sorption data at higher P concentrations. The amount of phosphate desorbed by all the three extractants increased significantly with the increasing extractant to soil ratios. Phosphate desorption by and water molecules was highly correlated with pH, percent clay and free iron oxide content of the soil. Significant positive correlation (r > 0.64, P L). Phosphate desorption by SO42- and water molecules was also positively correlated with Freundlich constant, N (r > 0.67, P 0 (r > 0.72, P –0.77, P L). The results suggest that freshly sorbed phosphate ions (inner-sphere complex forming species) can be readily desobed by outer-sphere complex forming species like sulphate and bicarbonate ions. Water molecules also desorbed significant amount of freshly sorbed phosphate from the soil colloids.
文摘Rubber trees (Hevea brasiliensis Müll. Arg.) have been commercially cultivated for a century and a half in Asia, particularly in China, and they constitute a common element of plantation ecosystems in tropical regions. Soil health is fundamental to the sustainable development of rubber plantations. The objective of the study is to explore the influence of different complex ecological cultivation modes on the stability of soil aggregates in rubber based agroforestry systems. In this study, the ecological cultivation mode of rubber—Alpinia oxyphylla plantation, the ecological cultivation mode of rubber—Phrynium hainanense plantations, the ecological cultivation mode of rubber—Homalium ceylanicum plantations and monoculture rubber plantations were selected, and the particle size distribution of soil aggregates and their water stability characteristics were analyzed. The soil depth of 0 - 20 cm and 20 - 40 cm was collected for four cultivation modes. Soil was divided into 6 particle levels > 20 cm. soil was divided into 6 particle levels > 5 mm, 2 - 5 mm, 1 - 2 mm, 0.5 - 1 mm, 0.25 - 0.5 mm, and 0.053 - 0.25 mm according to the wet sieve method. The particle size proportion and water stability of soil aggregates were determined by the wet sieve method. The particle size proportion and water stability of soil aggregates under different ecological cultivation modes were analyzed. The results showed that under different ecological cultivation modes in the shallow soil layer (0 - 20 cm), the rubber—Alpinia oxyphylla plantation and the rubber—Phrynium hainanense plantation promoted the development of dominant soil aggregates towards larger size classes, whereas the situation is the opposite for rubber—Homalium ceylanicum plantation. In soil layer (20 - 40 cm), the ecological cultivation mode of rubber—Phrynium hainanense plantation developed the dominant radial level of soil aggregates to the diameter level of large aggregates. Rubber—Alpinia oxyphylla plantation and rubber—Homalium ceylanicum plantation, three indicators, including the water-stable aggregate content R<sub>0.25</sub> (>0.25 mm water-stable aggregates), mean weight diameter (MWD), and geometric mean diameter (GMD), were all lower than those in the rubber monoculture mode. However, in the rubber—Phrynium hainanense plantation, the water-stable aggregate content R<sub>0.25</sub>, mean weight diameter, and geometric mean diameter were higher than in the rubber monoculture mode, although these differences did not reach statistical significance.
文摘The repeated effects of vulnerable habitat and unreasonable human activities on the Bashang Plateau of China led the chestnut soil to degrade. It expresses in reducing soil CEC, decreasing nutrient content, decomposing organic complexes, and reducing humus in loose, steady and tight bond forms, respectively. The percentage of three forms are 21%—34%, 44%—55% and 5%—6.2%, respectively.
