The rhizosphere, distinct from bulk soil, is defined as the volume of soil around living roots and influenced by root activities. We investigated protease, invertase, cellulase, urease, and acid phosphatase activities...The rhizosphere, distinct from bulk soil, is defined as the volume of soil around living roots and influenced by root activities. We investigated protease, invertase, cellulase, urease, and acid phosphatase activities in rhizosphere and bulk soils of six Nothotsuga longibracteata forest communities within Tianbaoyan National Nature Reserve, including N. longibracteata ＋ either Phyllostachys pubescens, Schima superba, Rhododendron simiarum, Cunninghamia lanceolata, or Cyclobalanopsis glauca, and N. longibracteata pure forest. Rhizosphere soils possessed higher protease, invertase, cellulase, urease, and acid phosphatase activities than bulk soils. The highest invertase, urease, and acid phosphatase activities were observed in rhizosphere samples of N. longibracteata ＋ S. superba. Protease was highest in the N. longibracteata ＋ R. simiarum rhizosphere, while cellulase was highest in the pure N. longibracteata forest rhizosphere. All samples exhibited obvious rhizosphere effects on enzyme activities with a significant linear correlation between acid phosphatase and cellulase activities （p 〈 0.05） in rhizosphere soils and between protease and acid phosphatase activities （p 〈 0.05） in bulk soils. A principal component analysis, correlating 13 soil chemical properties indices relevant to enzyme activities, showed that protease, invertase, acid phosphatase, total N, and cellulase were the most important variables impacting rhizosphere soil quality.展开更多
Harnessing disease suppressive microbiomes constitutes a promising strategy for optimizing plant growth.However,relatively lttle information is available about the relationship between bulk and rhizosphere soil microb...Harnessing disease suppressive microbiomes constitutes a promising strategy for optimizing plant growth.However,relatively lttle information is available about the relationship between bulk and rhizosphere soil microbiomes.Here,the assembly of banana bulk soil and rhizosphere microbiomes was investigated in a mono-culture system consisting of bio-organic(BIO)and organic management practices.Applying BIO practice in newly reclaimed fields resulted in a high-efficiency biocontrol rate,thus providing a promising strategy for pre-control of Fusarium wilt disease.The soil microbiota was further characterized by MiSeq sequencing and quantitative PCR.The results indicate that disease suppression was mediated by the structure of a suppressive rhizosphere microbiome with respect to distinct community composition,diversity and abundance.Overall microbiome suppressiveness was primarily related to a particular set of enriched bacterial taxa affiliated with Pseudomonas,Terrimonas,Cupriavi-dus,Gp6,Ohtaekwangia and Duganella.Finally,struc-tural equation modeling was used to show that the changes in bulk soil bacterial community determined its induced rhizosphere bacterial community,which serves as an important and direct factor in restraining the pathogen.Collectively,this study provides an integrative approach to disentangle the biological basis of disease-suppressive microbiomes in the context of agricultural practice and soil management.展开更多
To investigate the effects of coal mining on soil physical properties,sandy lands with three major vegetation types(Salix psammophila,Populus simonii,and Artemisia ordosica)were investigated by the ring knife method a...To investigate the effects of coal mining on soil physical properties,sandy lands with three major vegetation types(Salix psammophila,Populus simonii,and Artemisia ordosica)were investigated by the ring knife method and double-ring infiltrometer.Specifically,variations in soil bulk density and water infiltration rate and the influences of coal mining and vegetation type on the properties during different subsidence stages were studied at the Shendong Bulianta mine.The results showed that,in the period before mining,soil bulk density occurred in the order A.ordosica>P.simonii>S.psammophila,with a negative correlation between the initial infiltration rate and steady infiltration rate being observed.In the period during mining and 3 months after mining,there were no significant differences in soil bulk density and water infiltration rate among vegetation types.At 1 year after mining,the soil bulk density occurred in the order A.ordosica>S.psammophila>P.simonii,having a negative correlation with the steady infiltration rate.The water infiltration depths of the S.psammophila,P.simonii and A.ordosica were 50,60,and 30 cm,respectively.The infiltration characters were simulated by the Kostiakov equations,and the simulated and experimental results were consistent.Linear regression revealed that vegetation types and soil bulk density had significant effects on soil initial infiltration rate during the four study periods,and the infiltration rate of the period 1 year after mining was mainly influenced by the soil bulk density of the period before mining.The results indicated that vegetation types had significant effects on soil bulk density,and that the tree-shrub-grass mode was better than one single plantation for water conversation and vegetation recovery in sandy land subjected to mining.展开更多
Regression models for predicting soil bulk density(BD) have usually been related to organic matter content, but it remains unknown whether soil acidity modifies this relationship, particularly for afforested/reforeste...Regression models for predicting soil bulk density(BD) have usually been related to organic matter content, but it remains unknown whether soil acidity modifies this relationship, particularly for afforested/reforested soils. We measured soil BD along with organic matter content and pH in an afforested/reforested area in Northwest and Northeast China. Using these measurements, we parameterized and validated three BD models: the Adams equation, and exponential and radical models. Model validation showed that the Adams equation failed to predict the BD of the afforested/reforested soils, producing a large overestimation. Incorporation of soil pH into the Adams equation significantly improved its performance. The exponential and radical models parameterized by the measured data simulated soil BD quite well, particularly when soil pH was incorporated. However, incorporation of soil texture variables into these models did not improve model performance compared with the pH-modified models. This led to the conclusion that the Adams equation, exponential, and radical models with pH modification are applicable to afforested/reforested soils with various acidities.展开更多
Diffusion coefficients of chloride ions in four soils of different texture with varying effective moisture content and varying bulk density from 1.1 to 1.6 g cm3 under three different temperatures were determined by t...Diffusion coefficients of chloride ions in four soils of different texture with varying effective moisture content and varying bulk density from 1.1 to 1.6 g cm3 under three different temperatures were determined by the diffusion-cell method using 36Cl-labelled CaCl2 solution. The results showed that activation energy decreased with water content, which indicated that the threshold for diffusion was lower at a higher soil moisture rate. Therefore, the diffusion coefficient (D) of chloride ions in soil increased consistently with soil moisture. Although a near linear increase in the diffusion coefficient with increasing soil moisture or bulk density in all the soils was observed, the increase rate in different soils was not the same. The D value increased with temperature, and with temperature increased by 10℃ in the range from 5 "C to 45℃ theD valve increased by 10%～30%, averaging about 20%.展开更多
Soil bulk density is a basic but important physic soil property related to soil porosity,soil moisture and hydraulic conductivity,which is crucial to soil quality assessment and land use management.In this study,we ev...Soil bulk density is a basic but important physic soil property related to soil porosity,soil moisture and hydraulic conductivity,which is crucial to soil quality assessment and land use management.In this study,we evaluated the spatial variability of soil bulk density in the 0–20,20–40,40–60 and 60–100 cm layers as well as its affecting factors in Southwest China’s agricultural intensive area.Results indicated the mean value of surface soil bulk density(0–20 cm)was 1.26 g cm^(–3),significantly lower than that of subsoil(20–100 cm).No statistical difference existed among the subsoil with a mean soil bulk density of 1.54 g cm^(–3).Spatially,soil bulk density played a similar spatial pattern in soil profile,whereas obvious differences were found in details.The nugget effects for soil bulk density in the 0–20 and 20–40 cm layers were 27.22 and27.02%while 12.06 and 3.46%in the 40–60 and 60–100 cm layers,respectively,gradually decreasing in the soil profile,indicating that the spatial variability of soil bulk density above 40 cm was affected by structural and random factors while dominated by structural factors under 40 cm.Soil organic matter was the controlling factor on the spatial variability of soil bulk density in each layer.Land use and elevation were another two dominated factor controlling the spatial variability of soil bulk density in the 0–20 and 40–60 cm layers,respectively.Soil genus was one of the dominated factors controlling the spatial variability of soil bulk below 40 cm.展开更多
The main aim of soil monitoring system is to obtain the knowledge of the most current state and development of soil properties according to concrete threats to soil. To determine the significant changes of soil proper...The main aim of soil monitoring system is to obtain the knowledge of the most current state and development of soil properties according to concrete threats to soil. To determine the significant changes of soil properties in time, it is important to know spatial variability of concrete soil parameter for concrete site. Only those time changes of the soil parameter are significant, which exceed its spatial variability at the site. The main aim of the study has been focused on the evaluation of small-scale site heterogeneity of equilibrium soil bulk density and the integration of impact of this heterogeneity in evaluation of degradation process of soil compaction in time. As site variation coefficients have considerably varied at standard sampling with five repetitions during monitoring period, one-time detail spatial variability mapping of soil bulk density was realized at 17 repetitions on five selected monitoring sites with different soil type, texture and use. This increase in the number of sampling points helped us to specify and stabilize the values of variation coefficients (between minimum and maximum by standard sampling) as well as the extent of confidence intervals. Standard deviations at the chosen monitoring sites moved from 0.039 to 0.118 g·cm<sup><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">-</span>3</span></sup><span style="font-family:Verdana;"> in topsoil and from 0.031 to 0.067 g·cm</span><sup><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">-</span>3</span></sup><span style="font-family:Verdana;"> in subsoil and expressed as variation coefficient 2.9% - 9.2% and 2.0% - 4.9%, respectively. The intervals of significant time changes of soil bulk density for the sites and depths were determined on the base of its site confidence interval (95%) and uncertainty rate of its measure methodology. The time changes of bulk density values between single year-to-year sampling were overlapped by this interval of significant changes to obtain significant bulk density changes in time. This method allowed us to distinguish significant time changes in soil bulk density from insignificant ones. The bulk density value changes on the monitoring sites were significant in the range of six to nine years within observed period 2002-2014 in both depths.</span>展开更多
<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environ...<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 Elite<span style="white-space:nowrap;"><sup>TM</sup></span> nuclear gauge method (radiation) for measuring bulk density (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span>) and volumetric moisture content (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span>) in a clay loam soil. Soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> obtained using the core method (1.454, 1.492 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) were greater than those obtained using the radiation method (1.343, 1.476 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths;however, the CV’s of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span>, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> for many agricultural, hydrological and environmental studies in most soils.</span>展开更多
[Objective] This study was to reveal the effect of different land use patterns on physical characteristics of soil water in the Yellow River wetland in Shaanxi Province.[Method]Taking Yellow River wetland in Shaanxi P...[Objective] This study was to reveal the effect of different land use patterns on physical characteristics of soil water in the Yellow River wetland in Shaanxi Province.[Method]Taking Yellow River wetland in Shaanxi Province as experimental plot,we compared the physical properties of the soil water under different land use patterns and studied the physical properties and the change law of soil water during the wetland degeneration process.[Result]Under different land use patterns,soil bulk density rose with the increase of soil depth.During the degeneration process of from river wetland to reclaimed wetland（paddy field）,finally to abandoned land owing to salinization,the mean soil bulk density reduced correspondingly from 1.474 to 1.522 g/cm3,finally to 1.593 g/cm3 when abandoned.Accompanying wetland degeneration,soil became compact increasingly,and the indicators of soil porosity（total porosity,capillary porosity,non-capillary porosity）were also reduced with the change of land use patterns,in which,capillary porosity and total porosity reached the extremely significant level with the change of land use patterns,and non-capillary porosity reached significant level.The changes of soil porosity condition accelerated the deterioration of wetland.Under different land use patterns,the maximum soil moisture capacity,capillary moisture capacity and minimum moisture capacity all showed a similar change law.Compared with wetland,the maximum soil moisture capacity of reclaimed land（paddy field）and salinized land respectively decreased by 5.7% and 22.3%,capillary moisture capacity by 0.2% and 19.4%,minimum moisture capacity by 2.7% and 15.9%.Of the three land use patterns,wetland displayed both higher water holding capacity and water drainage capacity over reclaimed land（paddy field）and salinized land.By comparison with wetland,the reclaimed land（paddy field）and salinized land respectively decreased by 12.4% and 15.2% in total water holding capacity,and by 2.7% and 15.9% in total water drainage capacity.[Conclusion]To conserve the water resource in Yellow River wetland,regulate the hydrological cycle and enhance drought and water logging resistances,it should be noted that reasonable countermeasures be taken to exploit the state-owned forest land and paddy field around the wetland and the related resources.展开更多
The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy ...The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+sorption, and the p H changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+followed a descending order of clay > coarse sand > bulk soil > silt> sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+by the bulk soil and the aggregates, which were divided into two stages(rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations(P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The p H of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the p H of the solution was minimized nearly simultaneously.The sorption progress of Cu2+by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil p H and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil.展开更多
The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils we...The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils were evaluated for each scenic spots by calculating its soil impact indexes （SII） in the park. The results indicated that visitors＇ activities caused a serious influence on the soil in the park, especially in the two most used scenic spots-- Yellowstone Village and Gold Whip Stream. The impact of tourism on soil mainly occurred within 3 m along the trails. The impact shapes are classified into six type as single-sided node type, double-sided node type, cross node type, single-sided linkage type, double-sided linkage type and short-cut linkage type. Of six types of impact shapes, the single-sided node type and double-sided type were dominant. The average water contents of soil for six scenic spots at sample areas of 1 m, 2 m and 3 m from trial is 36.6%, 24.5% and 2.2% lower than that of the control area, respectively. The average soil hardness for six scenic spots at 1m, 2 m, and 3m from the trails tramped increased 167.9%, and 122.2%, and 15.8%, respectively, compared with the control area. Soil bulk density increased 26.5% at 1 m and 20.9% at 2 m from the trails. The main countermeasures for reducing the range and extent of tourism impact on soil are discussed.展开更多
Earthworms are crucial to soil ecosystems as keystone species.They perform various ecological functions through their associated microbiomes.However,the characteristics of these microbiomes in various vermicompartment...Earthworms are crucial to soil ecosystems as keystone species.They perform various ecological functions through their associated microbiomes.However,the characteristics of these microbiomes in various vermicompartments(earthworm-associated compartments)within soil-earthworm systems have not been systematically studied.Here,using earthworms of two ecotypes(i.e.,epigeic Eisenia fetida and anecic Metaphire guillelmi)as models,we conducted a full and comprehensive exploration of the bacterial community in several potential distinct compartments,including bulk soil,drilosphere,gut wall,gut content,and casts,through 2D-terraria incubation technology and high-throughput sequencing approaches.Bacterial diversity,community structures in each compartment,differential OTUs in vermicompartments compared with bulk soil,and the co-occurrence relationship of bacteria in bulk soil and gut-compartments(i.e.,gut wall and gut content)were assessed.Results showed that three major vermicompartments,i.e.,drilosphere,gut,and casts,were distinctly different in hosting the bacterial community.The levels of alpha diversity followed the order of drilosphere>casts>gut wall≈gut content.These patterns of vermicompartments along earthworms did not vary with ecotype,implying that the vermicompartments were the primary factors influencing the bacterial community.Finally,based on the difference in microbiomes in gut-compartments and the state-of-the-art use of the term“gut microbiomes”,it is recommended to establish a unified definition of gut microbes that encompasses microbiomes residing in both the gut wall and gut content,which could provide a clear and consistent understanding of gut microbiomes.This work provides a comprehensive overview of earthworm-associated microbiomes,enhancing our understanding of fundamental earthworm ecology and soil biology.展开更多
Soil organic carbon(SOC)and its relationship with landscape attributes are important for evaluating current regional,continental,and global carbon stores.Data of SOC in surface soils(0–20 cm)of four main soils,Cambis...Soil organic carbon(SOC)and its relationship with landscape attributes are important for evaluating current regional,continental,and global carbon stores.Data of SOC in surface soils(0–20 cm)of four main soils,Cambisol,Arenosol,Phaeozem,and Chernozem,were collected at 451 locations in Nongan County under maize monoculture in the Song-Nen Plain,Northeast China.The spatial characteristics of soil organic carbon were studied,using geographic information systems(GIS)and geostatistics.Effects of other soil physical and chemical properties,elevation,slope,and soil type on SOC were explored.SOC concentrations followed a normal distribution,with an arithmetic mean of 14.91 g kg-1.The experimental variogram of SOC was fitted with a spherical model.There were significant correlations between soil organic carbon and bulk density(r=-0.374**),pH(r=0.549**),total nitrogen(r=0.781**),extractable phosphorus(r=-0.109*),exchangeable potassium(r=0.565**),and cation exchange capacity(r=0.313**).Generally,lower SOC concentrations were significantly associated with high elevation(r=-0.429**).Soil organic carbon was significantly negatively correlated with slope gradient(r=-0.195**).Samples of the Cambisol statistically had the highest SOC concentrations,and samples of the Arenosol had the lowest SOC value.展开更多
We selected four kinds of land use types from Caohai wetlands of Guizhou plateau（a total number of 32 soil profiles） to study the distribution characteristics of organic carbon content in soil. With different ways o...We selected four kinds of land use types from Caohai wetlands of Guizhou plateau（a total number of 32 soil profiles） to study the distribution characteristics of organic carbon content in soil. With different ways of land use, the organic carbon content of soil profiles and organic carbon density show the tendency of decreasing firstly and then increasing from top to bottom. With the increase of depth, the vertical difference becomes smaller first and then starts increasing. Land reclamation reduces the soil organic carbon content and density, changing its distribution structure in topsoil. The average content of organic carbon in Caohai wetlands are as follows： lake bed silt [ marsh wetland [ farmland [ woodland, the average organic carbon content of lake bed silt, marsh wetland,farmland and woodland are 16.40, 2.94, 1.81 and 1.08 %,respectively. Land reclamation reduces the organic carbon content of soil, therefore the conversion of cultivated lands to wetlands and the increase of forest coverage will help to fix the organic carbon in soil and increase its reserves.展开更多
The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices ...The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients （CU） of approximately 65, 80, and 95% （referred to as low, medium, and high uniformity, respectively） and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity （ECb） was monitored continuously with approximately equally spaced frequency domain reflectometry （FDR） sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.展开更多
In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage （no-tillage and subsoiling） could decrease soil bulk d...In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage （no-tillage and subsoiling） could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0-40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon （SOC）, total nitrogen （TN）, water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested： no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 （NT-ST-NT）; subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 （ST-NT-ST）; and conventional tillage over years 1-3 （CT）. Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0-40 cm soil, with the greatest effect under ST-NT-ST. In 0-20 and 2（}-40 cm soils, the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the 〉 2 mm and 〈 0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.展开更多
Understanding the effects of cover crops and tillage on soil physical properties is important for determining soil productivity. This study was conducted at Lincoln University＇s Freeman Center, USA to evaluate the ef...Understanding the effects of cover crops and tillage on soil physical properties is important for determining soil productivity. This study was conducted at Lincoln University＇s Freeman Center, USA to evaluate the effects of tillage and cover crop management on soil hydraulic properties. The field site included three replicate blocks in a randomized complete block design with each plot measuring 21.3 m in length and 12.2 m in width. Treatment factors were tillage at two levels （moldboard plow tillage vs. no tillage） and cover crop at two levels （cereal rye （Secale cereal） cover crop vs. no cover crop）. Soil samples were collected in late spring/early summer from each treatment at 10-cm depth increments from the soil surface to a depth of 40 cm using cores （76.2-mm diameter and 76.2-mm length）. Soil bulk density was 13% lower with tillage compared with no-tillage. Volumetric water content was significantly higher at 0.0 and -0.4 kPa pressures with tillage compared with no tillage. Tillage increased the proportion of coarse mesopores by 32gc compared with no tillage, resulting in 87% higher saturated hydraulic conductivity （Ksat）. Cover crop increased the proportion of macropores by 24~ compared with no cover crop; this can potentially increase water infiltration and reduce runoff. As a result of higher macroporosity, Ksat was higher under cover crop compared with no cover crop. This study demonstrated that tillage can benefit soil hydraulic properties in the short term, but these effects may not persist over time. Cover crops may slightly improve soil hydraulic properties, but longer term studies are needed to evaluate the long-term effects.展开更多
Objective:To investigate the amounts of extractable organic nitrogen(EON),and the relationships between EON and total extractable nitrogen(TEN),especially the amino acids(AAs) adsorbed by soils,and a series of other h...Objective:To investigate the amounts of extractable organic nitrogen(EON),and the relationships between EON and total extractable nitrogen(TEN),especially the amino acids(AAs) adsorbed by soils,and a series of other hydrolyzed soil nitrogen indices in typical land use soil types from southeast China.Under traditional agricultural planting conditions,the functions of EON,especially AAs in the rhizosphere and in bulk soil zones were also investigated.Methods:Pot experiments were conducted using plants of pakchoi(Brassica chinensis L.) and rice(Oryza sativa L.).In the rhizosphere and bulk soil zone studies,organic nitrogen components were extracted with either distilled water,0.5 mol/L K2SO4or acid hydrolysis.Results:K2SO4-EON constituted more than 30% of TEN pools.K2SO4-extractable AAs accounted for 25% of EON pools and nearly 10% of TEN pools in rhizosphere soils.Overall,both K2SO4-EON and extractable AAs contents had positive correlations with TEN pools.Conclusions:EON represented a major component of TEN pools in garden and paddy soils under traditional planting conditions.Although only a small proportion of the EON was present in the form of water-extractable and K2SO4-extractable AAs,the release of AAs from soil exchangeable sites might be an important source of organic nitrogen(N) for plant growth.Our findings suggest that the content of most organic forms of N was significantly greater in rhizosphere than in bulk soil zone samples.However,it was also apparent that the TEN pool content was lower in rhizosphere than in bulk soil samples without added N.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.31370624)the Specialized Research Fund for the Doctoral Program of Higher Education(Grant No.20103515110005)+3 种基金the National Science Foundation of Fujian,China(Grant No.2011J01071)Young Teacher Project of Fujian Province(Grant No.JA13118JK2013016)the National College Students’Innovation and Entrepreneurship Training Program(Grant No.111zc3009)
文摘The rhizosphere, distinct from bulk soil, is defined as the volume of soil around living roots and influenced by root activities. We investigated protease, invertase, cellulase, urease, and acid phosphatase activities in rhizosphere and bulk soils of six Nothotsuga longibracteata forest communities within Tianbaoyan National Nature Reserve, including N. longibracteata ＋ either Phyllostachys pubescens, Schima superba, Rhododendron simiarum, Cunninghamia lanceolata, or Cyclobalanopsis glauca, and N. longibracteata pure forest. Rhizosphere soils possessed higher protease, invertase, cellulase, urease, and acid phosphatase activities than bulk soils. The highest invertase, urease, and acid phosphatase activities were observed in rhizosphere samples of N. longibracteata ＋ S. superba. Protease was highest in the N. longibracteata ＋ R. simiarum rhizosphere, while cellulase was highest in the pure N. longibracteata forest rhizosphere. All samples exhibited obvious rhizosphere effects on enzyme activities with a significant linear correlation between acid phosphatase and cellulase activities （p 〈 0.05） in rhizosphere soils and between protease and acid phosphatase activities （p 〈 0.05） in bulk soils. A principal component analysis, correlating 13 soil chemical properties indices relevant to enzyme activities, showed that protease, invertase, acid phosphatase, total N, and cellulase were the most important variables impacting rhizosphere soil quality.
基金This research was funded by the National Key Research and Development Program(2017YFD0202101)the National Natural Science Foundation of China(31672239 and 31972509)+1 种基金the 111 project(B12009),the Priority Academic Program Development of the Jiangsu Higher Education Institutions(PAPD)the Innovative Research Team Development Plan of the Ministry of Education of China(IRT17R56).
文摘Harnessing disease suppressive microbiomes constitutes a promising strategy for optimizing plant growth.However,relatively lttle information is available about the relationship between bulk and rhizosphere soil microbiomes.Here,the assembly of banana bulk soil and rhizosphere microbiomes was investigated in a mono-culture system consisting of bio-organic(BIO)and organic management practices.Applying BIO practice in newly reclaimed fields resulted in a high-efficiency biocontrol rate,thus providing a promising strategy for pre-control of Fusarium wilt disease.The soil microbiota was further characterized by MiSeq sequencing and quantitative PCR.The results indicate that disease suppression was mediated by the structure of a suppressive rhizosphere microbiome with respect to distinct community composition,diversity and abundance.Overall microbiome suppressiveness was primarily related to a particular set of enriched bacterial taxa affiliated with Pseudomonas,Terrimonas,Cupriavi-dus,Gp6,Ohtaekwangia and Duganella.Finally,struc-tural equation modeling was used to show that the changes in bulk soil bacterial community determined its induced rhizosphere bacterial community,which serves as an important and direct factor in restraining the pathogen.Collectively,this study provides an integrative approach to disentangle the biological basis of disease-suppressive microbiomes in the context of agricultural practice and soil management.
基金supported by the National High-Tech Research and Development Projects(863 program)(2013AA102904).
文摘To investigate the effects of coal mining on soil physical properties,sandy lands with three major vegetation types(Salix psammophila,Populus simonii,and Artemisia ordosica)were investigated by the ring knife method and double-ring infiltrometer.Specifically,variations in soil bulk density and water infiltration rate and the influences of coal mining and vegetation type on the properties during different subsidence stages were studied at the Shendong Bulianta mine.The results showed that,in the period before mining,soil bulk density occurred in the order A.ordosica>P.simonii>S.psammophila,with a negative correlation between the initial infiltration rate and steady infiltration rate being observed.In the period during mining and 3 months after mining,there were no significant differences in soil bulk density and water infiltration rate among vegetation types.At 1 year after mining,the soil bulk density occurred in the order A.ordosica>S.psammophila>P.simonii,having a negative correlation with the steady infiltration rate.The water infiltration depths of the S.psammophila,P.simonii and A.ordosica were 50,60,and 30 cm,respectively.The infiltration characters were simulated by the Kostiakov equations,and the simulated and experimental results were consistent.Linear regression revealed that vegetation types and soil bulk density had significant effects on soil initial infiltration rate during the four study periods,and the infiltration rate of the period 1 year after mining was mainly influenced by the soil bulk density of the period before mining.The results indicated that vegetation types had significant effects on soil bulk density,and that the tree-shrub-grass mode was better than one single plantation for water conversation and vegetation recovery in sandy land subjected to mining.
基金supported by the National Basic Research Program of China (No.2014CB954004)the National Natural Science Foundation of China (No.31370492)
文摘Regression models for predicting soil bulk density(BD) have usually been related to organic matter content, but it remains unknown whether soil acidity modifies this relationship, particularly for afforested/reforested soils. We measured soil BD along with organic matter content and pH in an afforested/reforested area in Northwest and Northeast China. Using these measurements, we parameterized and validated three BD models: the Adams equation, and exponential and radical models. Model validation showed that the Adams equation failed to predict the BD of the afforested/reforested soils, producing a large overestimation. Incorporation of soil pH into the Adams equation significantly improved its performance. The exponential and radical models parameterized by the measured data simulated soil BD quite well, particularly when soil pH was incorporated. However, incorporation of soil texture variables into these models did not improve model performance compared with the pH-modified models. This led to the conclusion that the Adams equation, exponential, and radical models with pH modification are applicable to afforested/reforested soils with various acidities.
文摘Diffusion coefficients of chloride ions in four soils of different texture with varying effective moisture content and varying bulk density from 1.1 to 1.6 g cm3 under three different temperatures were determined by the diffusion-cell method using 36Cl-labelled CaCl2 solution. The results showed that activation energy decreased with water content, which indicated that the threshold for diffusion was lower at a higher soil moisture rate. Therefore, the diffusion coefficient (D) of chloride ions in soil increased consistently with soil moisture. Although a near linear increase in the diffusion coefficient with increasing soil moisture or bulk density in all the soils was observed, the increase rate in different soils was not the same. The D value increased with temperature, and with temperature increased by 10℃ in the range from 5 "C to 45℃ theD valve increased by 10%～30%, averaging about 20%.
基金supported by the National Natural Science Foundation of China (4120124)the Science Fund of the Education Department of Sichuan Province, China (16ZB0048)
文摘Soil bulk density is a basic but important physic soil property related to soil porosity,soil moisture and hydraulic conductivity,which is crucial to soil quality assessment and land use management.In this study,we evaluated the spatial variability of soil bulk density in the 0–20,20–40,40–60 and 60–100 cm layers as well as its affecting factors in Southwest China’s agricultural intensive area.Results indicated the mean value of surface soil bulk density(0–20 cm)was 1.26 g cm^(–3),significantly lower than that of subsoil(20–100 cm).No statistical difference existed among the subsoil with a mean soil bulk density of 1.54 g cm^(–3).Spatially,soil bulk density played a similar spatial pattern in soil profile,whereas obvious differences were found in details.The nugget effects for soil bulk density in the 0–20 and 20–40 cm layers were 27.22 and27.02%while 12.06 and 3.46%in the 40–60 and 60–100 cm layers,respectively,gradually decreasing in the soil profile,indicating that the spatial variability of soil bulk density above 40 cm was affected by structural and random factors while dominated by structural factors under 40 cm.Soil organic matter was the controlling factor on the spatial variability of soil bulk density in each layer.Land use and elevation were another two dominated factor controlling the spatial variability of soil bulk density in the 0–20 and 40–60 cm layers,respectively.Soil genus was one of the dominated factors controlling the spatial variability of soil bulk below 40 cm.
文摘The main aim of soil monitoring system is to obtain the knowledge of the most current state and development of soil properties according to concrete threats to soil. To determine the significant changes of soil properties in time, it is important to know spatial variability of concrete soil parameter for concrete site. Only those time changes of the soil parameter are significant, which exceed its spatial variability at the site. The main aim of the study has been focused on the evaluation of small-scale site heterogeneity of equilibrium soil bulk density and the integration of impact of this heterogeneity in evaluation of degradation process of soil compaction in time. As site variation coefficients have considerably varied at standard sampling with five repetitions during monitoring period, one-time detail spatial variability mapping of soil bulk density was realized at 17 repetitions on five selected monitoring sites with different soil type, texture and use. This increase in the number of sampling points helped us to specify and stabilize the values of variation coefficients (between minimum and maximum by standard sampling) as well as the extent of confidence intervals. Standard deviations at the chosen monitoring sites moved from 0.039 to 0.118 g·cm<sup><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">-</span>3</span></sup><span style="font-family:Verdana;"> in topsoil and from 0.031 to 0.067 g·cm</span><sup><span style="font-family:Verdana;"><span style="color:#4F4F4F;font-family:-apple-system, " font-size:16px;white-space:normal;background-color:#ffffff;"="">-</span>3</span></sup><span style="font-family:Verdana;"> in subsoil and expressed as variation coefficient 2.9% - 9.2% and 2.0% - 4.9%, respectively. The intervals of significant time changes of soil bulk density for the sites and depths were determined on the base of its site confidence interval (95%) and uncertainty rate of its measure methodology. The time changes of bulk density values between single year-to-year sampling were overlapped by this interval of significant changes to obtain significant bulk density changes in time. This method allowed us to distinguish significant time changes in soil bulk density from insignificant ones. The bulk density value changes on the monitoring sites were significant in the range of six to nine years within observed period 2002-2014 in both depths.</span>
文摘<span style="font-family:Verdana;">Soil bulk density and moisture content are dynamic properties that vary with changes in soil and field conditions and have many agricultural, hydrological and environmental implications. The main objective of this study was to compare between a soil core sampling method (core) and the CPN MC-3 Elite<span style="white-space:nowrap;"><sup>TM</sup></span> nuclear gauge method (radiation) for measuring bulk density (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span>) and volumetric moisture content (<span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span>) in a clay loam soil. Soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> measurements were determined using the core and radiation methods at 0 - 10 and 10 - 20 cm soil depths. The mean values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> obtained using the core method (1.454, 1.492 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) were greater than those obtained using the radiation method (1.343, 1.476 g<span style="color:#4F4F4F;font-family:" font-size:14px;white-space:normal;background-color:#f7f7f7;"="">·</span>cm<span style="white-space:nowrap;"><sup>−3</sup></span>) at the 0 - 10 and 10 - 20 cm depths, respectively. Mean <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<span style="font-size:10.9091px;">v</span></i></span></span></i></span> values averaged across both depths (referred to as the 0 - 20 cm depth) measured by the core method were 4.47% and 22.74% greater, respectively, than those obtained by the radiation method. The coefficients of variation (CV) of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"></span><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths;however, the CV’s of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> values for both methods were larger at the 0 - 10 cm depth than those measured at the 10 - 20 cm depth. Similarly, the CV values of soil <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span> values measured by the core method were lower than the CV values of those measured by the radiation method at both depths. There were significant differences between two methods in terms of <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> and <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>θ<sub>v</sub></i></span></span></i></span>, with the core method generating greater values than the radiation method at the 0 - 20 cm depth. These discrepancies between the two methods could have resulted from soil compaction and soil disturbance caused by the core and radiation techniques, respectively, as well as by other sources of error. Nevertheless, the core sampling method is considered the most common one for measuring <span style="white-space:nowrap;"><i><span style="font-family:Verdana;white-space:normal;"><span style="white-space:nowrap;"><i>ρ<sub>B</sub></i></span></span></i></span> for many agricultural, hydrological and environmental studies in most soils.</span>
基金Supported by National Natural Science Foundation of China(40871119)Key Science and Technology Program of Shaanxi Province,China(2007K01-15-1)~~
文摘[Objective] This study was to reveal the effect of different land use patterns on physical characteristics of soil water in the Yellow River wetland in Shaanxi Province.[Method]Taking Yellow River wetland in Shaanxi Province as experimental plot,we compared the physical properties of the soil water under different land use patterns and studied the physical properties and the change law of soil water during the wetland degeneration process.[Result]Under different land use patterns,soil bulk density rose with the increase of soil depth.During the degeneration process of from river wetland to reclaimed wetland（paddy field）,finally to abandoned land owing to salinization,the mean soil bulk density reduced correspondingly from 1.474 to 1.522 g/cm3,finally to 1.593 g/cm3 when abandoned.Accompanying wetland degeneration,soil became compact increasingly,and the indicators of soil porosity（total porosity,capillary porosity,non-capillary porosity）were also reduced with the change of land use patterns,in which,capillary porosity and total porosity reached the extremely significant level with the change of land use patterns,and non-capillary porosity reached significant level.The changes of soil porosity condition accelerated the deterioration of wetland.Under different land use patterns,the maximum soil moisture capacity,capillary moisture capacity and minimum moisture capacity all showed a similar change law.Compared with wetland,the maximum soil moisture capacity of reclaimed land（paddy field）and salinized land respectively decreased by 5.7% and 22.3%,capillary moisture capacity by 0.2% and 19.4%,minimum moisture capacity by 2.7% and 15.9%.Of the three land use patterns,wetland displayed both higher water holding capacity and water drainage capacity over reclaimed land（paddy field）and salinized land.By comparison with wetland,the reclaimed land（paddy field）and salinized land respectively decreased by 12.4% and 15.2% in total water holding capacity,and by 2.7% and 15.9% in total water drainage capacity.[Conclusion]To conserve the water resource in Yellow River wetland,regulate the hydrological cycle and enhance drought and water logging resistances,it should be noted that reasonable countermeasures be taken to exploit the state-owned forest land and paddy field around the wetland and the related resources.
基金the Science and Technology Support Project of Jiangsu Province(Project No.BE2013711)for financially supporting this study
文摘The Taihu Lake region in East China has become prone to soil acidification, which changes heavy metals such as copper(Cu) in soil into water-soluble species and increases the mobility and contamination risks of heavy metals in the biological environment. In this study, the kinetics of Cu2+sorption by the bulk soil and the aggregate size fractions of an acidic paddy soil collected from the Taihu Lake region, the effects of temperature on Cu2+sorption, and the p H changes of the solution were investigated by static sorption and magnetic stirring. The aggregate size fractions were prepared by low-energy ultrasonic dispersing and freeze-drying. The total sorption amounts of the bulk soil and the aggregate size fractions for Cu2+followed a descending order of clay > coarse sand > bulk soil > silt> sand, corresponding to those of organic matter content, free iron oxide content, free aluminum oxide content, and cation exchange capacity. The kinetic sorption curves of Cu2+by the bulk soil and the aggregates, which were divided into two stages(rapid and slow sequentially), were well fitted by the first-order equation, the diffusion equation, and the Elovich equation, showing significant correlations(P < 0.05). Specific and non-specific sorption dominated in the fast and slow stages, respectively, and the former was predominant throughout the sorption process. The specific sorption accelerated and the non-specific sorption decelerated with rising temperature. The p H of the solution decreased significantly during the specific sorption and remained unchanged or increased slightly during the non-specific sorption. When the specific sorption terminated, the p H of the solution was minimized nearly simultaneously.The sorption progress of Cu2+by the bulk soil significantly preceded that by the aggregates. Therefore, heavy metal contamination may be another factor reducing soil p H and metal sorption forms should be taken into consideration in studies of mitigating soil heavy metal pollution or determining environmental capacity of heavy metal in soil.
基金This study was supported by the National Natural Science Foundation of China (NSFC30200040) and the Thousand-hundred-ten Talent Engineering project of Guangdong Province, P. R. China (03130401)
文摘The soil hardness, soil water content and soil bulk density along the trails of six scenic spots in the Zhangjiajie World Geopark were measured and analyzed, and the integrated effects of tourism trampling on soils were evaluated for each scenic spots by calculating its soil impact indexes （SII） in the park. The results indicated that visitors＇ activities caused a serious influence on the soil in the park, especially in the two most used scenic spots-- Yellowstone Village and Gold Whip Stream. The impact of tourism on soil mainly occurred within 3 m along the trails. The impact shapes are classified into six type as single-sided node type, double-sided node type, cross node type, single-sided linkage type, double-sided linkage type and short-cut linkage type. Of six types of impact shapes, the single-sided node type and double-sided type were dominant. The average water contents of soil for six scenic spots at sample areas of 1 m, 2 m and 3 m from trial is 36.6%, 24.5% and 2.2% lower than that of the control area, respectively. The average soil hardness for six scenic spots at 1m, 2 m, and 3m from the trails tramped increased 167.9%, and 122.2%, and 15.8%, respectively, compared with the control area. Soil bulk density increased 26.5% at 1 m and 20.9% at 2 m from the trails. The main countermeasures for reducing the range and extent of tourism impact on soil are discussed.
基金financed by the National Natural Science Foundation of China(Nos.42177258 and 41977047)the Fund Project of Shaanxi Key Laboratory of Land Consolidation,China(2019-ZD03)+1 种基金the Natural Science Foundation of Shanxi Province,China(No.20220302121322)a grant from the Shanxi Laboratory for Yellow River,China。
文摘Earthworms are crucial to soil ecosystems as keystone species.They perform various ecological functions through their associated microbiomes.However,the characteristics of these microbiomes in various vermicompartments(earthworm-associated compartments)within soil-earthworm systems have not been systematically studied.Here,using earthworms of two ecotypes(i.e.,epigeic Eisenia fetida and anecic Metaphire guillelmi)as models,we conducted a full and comprehensive exploration of the bacterial community in several potential distinct compartments,including bulk soil,drilosphere,gut wall,gut content,and casts,through 2D-terraria incubation technology and high-throughput sequencing approaches.Bacterial diversity,community structures in each compartment,differential OTUs in vermicompartments compared with bulk soil,and the co-occurrence relationship of bacteria in bulk soil and gut-compartments(i.e.,gut wall and gut content)were assessed.Results showed that three major vermicompartments,i.e.,drilosphere,gut,and casts,were distinctly different in hosting the bacterial community.The levels of alpha diversity followed the order of drilosphere>casts>gut wall≈gut content.These patterns of vermicompartments along earthworms did not vary with ecotype,implying that the vermicompartments were the primary factors influencing the bacterial community.Finally,based on the difference in microbiomes in gut-compartments and the state-of-the-art use of the term“gut microbiomes”,it is recommended to establish a unified definition of gut microbes that encompasses microbiomes residing in both the gut wall and gut content,which could provide a clear and consistent understanding of gut microbiomes.This work provides a comprehensive overview of earthworm-associated microbiomes,enhancing our understanding of fundamental earthworm ecology and soil biology.
基金Projcet supported by the Knowledge Innovation Program of the Chinese Academy of Sciences(No.KZCX2-YW-341)the National Basic Research Program of China(No.2009CB421103)the National Natural Science Foundation ofChina(Nos.40871187 and 40930527)
文摘Soil organic carbon(SOC)and its relationship with landscape attributes are important for evaluating current regional,continental,and global carbon stores.Data of SOC in surface soils(0–20 cm)of four main soils,Cambisol,Arenosol,Phaeozem,and Chernozem,were collected at 451 locations in Nongan County under maize monoculture in the Song-Nen Plain,Northeast China.The spatial characteristics of soil organic carbon were studied,using geographic information systems(GIS)and geostatistics.Effects of other soil physical and chemical properties,elevation,slope,and soil type on SOC were explored.SOC concentrations followed a normal distribution,with an arithmetic mean of 14.91 g kg-1.The experimental variogram of SOC was fitted with a spherical model.There were significant correlations between soil organic carbon and bulk density(r=-0.374**),pH(r=0.549**),total nitrogen(r=0.781**),extractable phosphorus(r=-0.109*),exchangeable potassium(r=0.565**),and cation exchange capacity(r=0.313**).Generally,lower SOC concentrations were significantly associated with high elevation(r=-0.429**).Soil organic carbon was significantly negatively correlated with slope gradient(r=-0.195**).Samples of the Cambisol statistically had the highest SOC concentrations,and samples of the Arenosol had the lowest SOC value.
基金supported by Project of Guizhou Special Funds for High-level Personnel (Grant Number TZJF-2011-44)Program for New Century Excellent Talents in University (NCET-12-0659)Project of Guizhou Governor Capital Fund (Guizhou province designed cooperative [2012]71)
文摘We selected four kinds of land use types from Caohai wetlands of Guizhou plateau（a total number of 32 soil profiles） to study the distribution characteristics of organic carbon content in soil. With different ways of land use, the organic carbon content of soil profiles and organic carbon density show the tendency of decreasing firstly and then increasing from top to bottom. With the increase of depth, the vertical difference becomes smaller first and then starts increasing. Land reclamation reduces the soil organic carbon content and density, changing its distribution structure in topsoil. The average content of organic carbon in Caohai wetlands are as follows： lake bed silt [ marsh wetland [ farmland [ woodland, the average organic carbon content of lake bed silt, marsh wetland,farmland and woodland are 16.40, 2.94, 1.81 and 1.08 %,respectively. Land reclamation reduces the organic carbon content of soil, therefore the conversion of cultivated lands to wetlands and the increase of forest coverage will help to fix the organic carbon in soil and increase its reserves.
基金supported by the National Natural Science Foundation of China (50979115)
文摘The dynamics of water and salt in soil were monitored in the 2010 and 2011 growing seasons of cotton to evaluate the salinity risk of soil under drip irrigation in arid environments for different management practices of drip system uniformity and irrigation amount. In the experiments, three Christiansen uniformity coefficients （CU） of approximately 65, 80, and 95% （referred to as low, medium, and high uniformity, respectively） and three irrigation amounts of 50, 75, and 100% of full irrigation were used. The distribution of the soil water content and bulk electrical conductivity （ECb） was monitored continuously with approximately equally spaced frequency domain reflectometry （FDR） sensors located along a dripline. Gravimetric samples of soil were collected regularly to determine the distribution of soil salinity. A great fluctuation in CU of water content and ECb at 60 cm depth was observed for the low uniformity treatment during the irrigation season, while a relatively stable variation pattern was observed for the high uniformity treatment. The ECb CU was substantially lower than the water content CU and its value was greatly related to the water content CU and the initial ECb CU. The spatial variation of seasonal mean soil water content and seasonal mean soil bulk electrical conductivity showed a high dependence on the variation pattern of emitter discharge rate along a dripline for the low and medium uniformity treatments. A greater irrigation amount produced a significantly lower soil salinity at the end of the irrigation season, while the influence of the system uniformity on the soil salinity was insignificant at a probability level of 0.1. In arid regions, the determination of the target drip irrigation system uniformity should consider the potential salinity risk of soil caused by nonuniform water application as the influence of the system uniformity on the distribution of the soil salinity was progressively strengthened during the growing season of crop.
基金Supported by the National Key Technologies Research and Development Program of the Ministry of Science and Technology of China during the 12th Five-Year Plan Period (No. 2012BAD09B03)the 111 Project of China (No. B12007)
文摘In rain-fed semi-arid agroecosystems, continuous conventional tillage can cause serious problems in soil quality and crop production, whereas rotational tillage （no-tillage and subsoiling） could decrease soil bulk density, and increase soil aggregates and organic carbon in the 0-40 cm soil layer. A 3-year field study was conducted to determine the effect of tillage practices on soil organic carbon （SOC）, total nitrogen （TN）, water-stable aggregate size distribution and aggregate C and N sequestration from 0 to 40 cm soil in semi-arid areas of southern Ningxia. Three tillage treatments were tested： no-tillage in year 1, subsoiling in year 2, and no-tillage in year 3 （NT-ST-NT）; subsoiling in year 1, no-tillage in year 2, and subsoiling in year 3 （ST-NT-ST）; and conventional tillage over years 1-3 （CT）. Mean values of soil bulk density in 0-40 cm under NT-ST-NT and ST-NT-ST were significantly decreased by 3.3% and 6.5%, respectively, compared with CT, while soil total porosity was greatly improved. Rotational tillage increased SOC, TN, and water-stable aggregates in the 0-40 cm soil, with the greatest effect under ST-NT-ST. In 0-20 and 2（}-40 cm soils, the tillage effect was confined to the 2-0.25 mm size fraction of soil aggregates, and rotational tillage treatments obtained significantly higher SOC and TN contents than conventional tillage. No significant differences were detected in SOC and TN contents in the 〉 2 mm and 〈 0.25 mm aggregates among all treatments. In conclusion, rotational tillage practices could significantly increase SOC and TN levels, due to a fundamental change in soil structure, and maintain agroecosystem sustainability in the Loess Plateau area of China.
基金funded by the USDA-National Institute of Food and Agriculture (NIFA) research (Cropping Systems Coordinated Agricultural Project: Climate Change Mitigation, and Adaptation in Cornbased Cropping Systems) grant (No. 2011-68002-30190)
文摘Understanding the effects of cover crops and tillage on soil physical properties is important for determining soil productivity. This study was conducted at Lincoln University＇s Freeman Center, USA to evaluate the effects of tillage and cover crop management on soil hydraulic properties. The field site included three replicate blocks in a randomized complete block design with each plot measuring 21.3 m in length and 12.2 m in width. Treatment factors were tillage at two levels （moldboard plow tillage vs. no tillage） and cover crop at two levels （cereal rye （Secale cereal） cover crop vs. no cover crop）. Soil samples were collected in late spring/early summer from each treatment at 10-cm depth increments from the soil surface to a depth of 40 cm using cores （76.2-mm diameter and 76.2-mm length）. Soil bulk density was 13% lower with tillage compared with no-tillage. Volumetric water content was significantly higher at 0.0 and -0.4 kPa pressures with tillage compared with no tillage. Tillage increased the proportion of coarse mesopores by 32gc compared with no tillage, resulting in 87% higher saturated hydraulic conductivity （Ksat）. Cover crop increased the proportion of macropores by 24~ compared with no cover crop; this can potentially increase water infiltration and reduce runoff. As a result of higher macroporosity, Ksat was higher under cover crop compared with no cover crop. This study demonstrated that tillage can benefit soil hydraulic properties in the short term, but these effects may not persist over time. Cover crops may slightly improve soil hydraulic properties, but longer term studies are needed to evaluate the long-term effects.
基金Project supported by the National Natural Science Foundation of China (Nos.30871595 and 31172032)the Special Fund for Agro-Scientific Research in the Public Interest,China(No.201003016)
文摘Objective:To investigate the amounts of extractable organic nitrogen(EON),and the relationships between EON and total extractable nitrogen(TEN),especially the amino acids(AAs) adsorbed by soils,and a series of other hydrolyzed soil nitrogen indices in typical land use soil types from southeast China.Under traditional agricultural planting conditions,the functions of EON,especially AAs in the rhizosphere and in bulk soil zones were also investigated.Methods:Pot experiments were conducted using plants of pakchoi(Brassica chinensis L.) and rice(Oryza sativa L.).In the rhizosphere and bulk soil zone studies,organic nitrogen components were extracted with either distilled water,0.5 mol/L K2SO4or acid hydrolysis.Results:K2SO4-EON constituted more than 30% of TEN pools.K2SO4-extractable AAs accounted for 25% of EON pools and nearly 10% of TEN pools in rhizosphere soils.Overall,both K2SO4-EON and extractable AAs contents had positive correlations with TEN pools.Conclusions:EON represented a major component of TEN pools in garden and paddy soils under traditional planting conditions.Although only a small proportion of the EON was present in the form of water-extractable and K2SO4-extractable AAs,the release of AAs from soil exchangeable sites might be an important source of organic nitrogen(N) for plant growth.Our findings suggest that the content of most organic forms of N was significantly greater in rhizosphere than in bulk soil zone samples.However,it was also apparent that the TEN pool content was lower in rhizosphere than in bulk soil samples without added N.
