As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and the...As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and theoretically; however, no studies have focused on understanding SSR on the Loess Plateau of China. This study investigated changes in SSR for three different tillage practices on the Loess Plateau of China and the effects of SSR on runoff and erosion yield during simulated rainfall. The tillage practices used were zero tillage（ZT）, shallow hoeing（SH） and contour ploughing（CP）. Two rainfall intensities were applied, and three stages of water erosion processes（splash erosion（I）, sheet erosion（II） and rill erosion（III）） were analyzed for each rainfall intensity. The chain method was used to measure changes in SSR both initially and after each stage of rainfall. A splash board was used to measure the splash erosion at stage I. Runoff and sediment data were collected continuously at 2-min intervals during rainfall erosion stages II and III. We found that SSR of the tilled surfaces ranged from 1.0% to 21.9% under the three tillage practices, and the order of the initial SSR for the three treatments was ZT〈SH〈CP. For the ZT treatment, SSR increased slightly from stage I to III, whereas for the SH and CP treatments, SSR decreased by 44.5% and 61.5% after the three water erosion stages, respectively, and the greatest reduction in SSR occurred in stage I. Regression analysis showed that the changes in SSR with increasing cumulative rainfall could be described by a power function（R2〉0.49） for the ZT, SH and CP treatments. The runoff initiation time was longer in the SH and CP treatments than in the ZT treatment. There were no significant differences in the total runoff yields among the ZT, SH and CP treatments. Sediment loss was significantly smaller（P〈0.05） in the SH and CP treatments than in the ZT treatment.展开更多
The effect of nanometer anatase TiO2 was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with di...The effect of nanometer anatase TiO2 was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with different amounts of TiO2 （0 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%） were exposed to UV-light irradiation for 25 hr. The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics. TiO2 significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO2 loading of 0 wt.% and 4 wt.%, respectively. In addition, the effects of H202, light intensity and humic acid on the degradation of phenanthrene were investigated. The degradation of phenanthrene increased with the concentration of H202, light intensity and the concentration of humic acids. It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO2 was a very promising technology for the treatments of soil polluted with organic substances in the future.展开更多
The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mecha...The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning＇s roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning＇s roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.展开更多
Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environ...Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environmental safety. The environmental behaviors of the two formulations were investigated in a bamboo forest under soil surface mulching conditions（CP） and non-covered cultivation conditions（NCP）. The half-lives of phoxim in soil under the two conditions in soil were 4.1–6.2 days（EC） and 31.5–49.5 days（G）,respectively. Phoxim in EC could be leached from the topsoil into the subsoil. A minimized leaching effect was observed for G under NCP. Inversely, an enhanced leaching effect was observed for G under CP. The G formulation resulted in more parent compound（in bamboo shoots） and metabolite（in soil） residues of phoxim than in the case of EC, especially under CP conditions. In addition, the intensity and duration of the formulation effect on soil p H adjustment from G were more obvious than that from EC. Results showed that the environmental behaviors（distribution, degradation, residue） of phoxim in the bamboo forest were significantly influenced by the type of formulation. The prolongation effect from phoxim G might cause persistence and long-term environmental risk. However,bamboo shoot consumption could be considered relatively safe after applying the recommended dose of the two phoxim formulations.展开更多
Photolysis of some polycyclic aromatic hydrocarbons （PAHs） on soil surfaces may play an important role in the fate of PAHs in the environment.Photolysis of PAHs on soil surfaces under UV irradiation was investigated...Photolysis of some polycyclic aromatic hydrocarbons （PAHs） on soil surfaces may play an important role in the fate of PAHs in the environment.Photolysis of PAHs on soil surfaces under UV irradiation was investigated.The effects of oxygen,irradiation intensity and soil moisture on the degradation of the three PAHs were observed.The results showed that oxygen,soil moisture and irradiation intensity enhanced the photolysis of the three PAHs on soil surfaces.The degradation of the three PAHs on soil surfaces is related to their absorption spectra and the oxidation-half-wave potential.The photolysis of PAHs on soil surfaces in the presence of oxygen followed pseudo first-order kinetics.The photolysis half-lives ranged from 37.87 days for benzo[a]pyrene to 58.73 days for phenanthrene.The results indicate that photolysis is a successful way to remediate PAHs-contaminated soils.展开更多
Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October ...Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.展开更多
Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux （Rs）...Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux （Rs） in northern hardwood forests and to quantify the relationship among Rs, soil temperature, and moisture in these stands. The experiment was a randomized complete block design that included sludge-amended, fertilized, and control treatments in sugar maple （Acer saccharum Marsh） dominated hardwood forests in the Upper Peninsula of Michigan, USA. Results showed that Rs was positively correlated to soil temperature （R^2 = 0.80, p 〈 0.001）, but was poorly correlated to soil moisture. Soil moisture positively affected the Rs only in the sludge-amended treatment. The Rs was significantly greater in the sludge-amended treatment than in the fertilized （p = 0.033） and the control （p = 0.048） treatments. The maximum Rs in the sludge-amended treatment was 8.8 μmol CO2 · m^ 2. s^-1, 91% and 126% greater than those in the fertilized （4.6 μmol CO2 · m^-2· s^-1） and control （3.9 μmol CO2· m^- 2· s^-1） treatments, respectively. The Rs did not differ significantly between the fertilized and control treatments. The difference in Rs between sludge-amended and the other treatments decreased with time following treatment.展开更多
Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough s...Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium, the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the roughness surface parameters and the frequency of the incident wave on the blstatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the rms and the correlation length of the rough surface, and the frequency of the incident wave on the bistatic scattering coefficient is very complex.展开更多
Soil surface wetness is indispensable land surface parameter in agriculture, hydrology and environmental engineering. This paper explores the relationship between surface radiant temperature and fractional vegetation ...Soil surface wetness is indispensable land surface parameter in agriculture, hydrology and environmental engineering. This paper explores the relationship between surface radiant temperature and fractional vegetation cover derived from satellite imagery to estimate soil surface wetness (triangle method) in Allahabad district. The pixel distributions create triangular shapes because the range of surface radiant temperature decreases as the amount of vegetation cover increases and sufficient number of pixels exists. A very weak correlation is found between the simulated soil surface wetness and ground measured soil moisture at deeper soil layers (R<sup>2</sup> < 0.15) on all the dates under investigation. This is because the drying rates at the surface discontinue to be linearly correlated to that at lower levels (depths). The standing water pixels distort the shape of the triangle especially at lower left edge of the triangle. This distortion is removable. The spatial and temporal inhomogeneity of soil surface wetness is examined.展开更多
Spatiotemporal forecasting of surface soil moisture(SSM)is recognized as a critical scientific issue in precision agricultural irrigation,regional drought monitoring,and early warning systems for extreme precipitation...Spatiotemporal forecasting of surface soil moisture(SSM)is recognized as a critical scientific issue in precision agricultural irrigation,regional drought monitoring,and early warning systems for extreme precipitation.However,long-term forecasting continues to pose formidable challenges because of the complexity observed across both the spatial and temporal scales.In this study,we used a daily SSM dataset at a 0.05°×0.05°spatial resolution over the Qilian Mountains,China and proposed a hybrid Convolutional Long Short-Term Memory(ConvLSTM)-Nudging model,which combined deep neural networks with data assimilation to increase the accuracy of long-term SSM forecasting.We trained and evaluated the SSM predictive performance of four models(Convolutional Neural Network(CNN),Long Short-Term Memory(LSTM),ConvLSTM,and ConvLSTM with Squeeze-and-Excitation(SE)attention mechanism(ConvLSTM-SE))in both short-term and long-term scenarios.The results showed that all the models perform well under short-term predictions,but the accuracy decrease substantially in long-term predictions.Therefore,we integrated Nudging technique during the long-term prediction phase to assimilate observational information and rectify model biases.Comprehensive evaluations demonstrate that Nudging significantly improves all the models,with ConvLSTM-Nudging achieving the best performance under the 200-d forecasting scenario.Relative to those of the best-performing ConvLSTM model for long-term forecasts,when observation noiseδ=0.00 and observation fraction obs=50.0%,the coefficient of determination(R2)of ConvLSTM-Nudging increases by approximately 82.1%,while its mean absolute error(MAE)and root mean squared error(RMSE)decrease by approximately 84.8%and 77.3%,respectively;the average Pearson correlation coefficient(r)improves by approximately 23.6%,and Bias is reduced by 98.1%.These results demonstrated that although pure deep learning models achieve high accuracy in the short-term predictions,they are prone to error accumulation and systematic drift in long-term autoregressive predictions.Integrating data assimilation with deep learning and continuously correcting the state through observation can effectively suppress long-term biases,thereby achieving robust long-term SSM forecasting.展开更多
Intense evaporation in areas with loess-like sulfate saline soils has resulted in significant ecological challenges that include water shortages and soil salinization.Investigating evaporation rate in loess-like sulfa...Intense evaporation in areas with loess-like sulfate saline soils has resulted in significant ecological challenges that include water shortages and soil salinization.Investigating evaporation rate in loess-like sulfate saline soils under varying salt contents carries crucial implications for understanding regional water loss processes,predicting soil salinization advancement,and formulating effective ecological management strategies.Therefore,this study sampled the loess-like sulfate saline soil that is widely distributed in western China as experimental materials and investigated the impact of different initial salt contents(0.00%,0.50%,1.50%,3.00%,and 5.00%)on the evaporation rate,water content,and temperature of soil.The results showed that the evaporation rate decreased with increasing initial salt content.After a salt accumulation layer formed on the soil surface,the water content of the surface soil fluctuated.An increase in the initial salt content resulted in a corresponding increase in the surface temperature.Considering the evaporation characteristics of loess-like sulfate saline soil and the impact of an anomalous increase in surface soil water content on soil surface resistance,this study proposed a modified evaporation model on the basis of Fujimaki's evaporation model of saline soil by introducing a correction coefficientβto modify the soil surface resistance.A comparison of the calculated evaporation rates before and after the modification with the measured evaporation rates revealed a significant improvement in the calculation accuracy of the modified model,indicating that the modified model is capable of more accurately simulating the evaporation rate of sulfate saline soil with different initial salt contents.This paper proposes an effective method for calculating the evaporation rate of loess-like sulfate saline soils,providing a theoretical basis for evaporation research in saline soil.展开更多
Understanding water dynamics under the effect of climatic conditions is important to improve water sustainability over the medium-and long-term.Clay content can affect soil hydrothermal properties,and hence modify wat...Understanding water dynamics under the effect of climatic conditions is important to improve water sustainability over the medium-and long-term.Clay content can affect soil hydrothermal properties,and hence modify water and heat exchange between soil and atmosphere,e.g.evapotranspiration and infiltration.This work aims to develop a numerical approach to explore the influence of clay content on soil hydrothermal response to the timely climatic conditions in the Lake Chad region,Sahel Region of west-central Africa.The meteorological information at the studied points,i.e.points A and B with a clay content of 8.3%and 25%,during the year 2008 is collected from ERA5-Land hourly data.The numerical results allow for understanding the effect of clay content on the hydrothermal response of the surface soil layer.Specifically,the soil surface temperature under point A is lower than that under point B during the dry season due to the dominant effect of heat conduction.However,the converse tendency is observed during the wet season because of the combined effect of heat conduction and latent heat.The variations of soil volumetric water content are closely related to the timely interaction between the soil and atmosphere,in addition to the hydrothermal properties of soil.Moreover,the outcomes of this work improve the understanding of the heat and water dynamics under the effect of climatic conditions and clay content,and provide further insights into the potential water protection in arid and semi-arid regions in the future.展开更多
Root zone soil moisture(RZSM)plays a critical role in land-atmosphere hydrological cycles and serves as the primary water source for vegetation growth.However,the correlations between RZSM and its associated variables...Root zone soil moisture(RZSM)plays a critical role in land-atmosphere hydrological cycles and serves as the primary water source for vegetation growth.However,the correlations between RZSM and its associated variables,including surface soil moisture(SSM),often exhibit nonlinearities that are challenging to identify and quantify using conventional statistical techniques.Therefore,this study presents a hybrid convolutional neural network(CNN)-long short-term memory neural network(LSTM)-attention(CLA)model for predicting RZSM.Owing to the scarcity of soil moisture(SM)observation data,the physical model Hydrus-1D was employed to simulate a comprehensive dataset of spatial-temporal SM.Meteorological data and moderate resolution imaging spectroradiometer vegetation characterization parameters were used as predictor variables for the training and validation of the CLA model.The results of the CLA model for SM prediction in the root zone were significantly enhanced compared with those of the traditional LSTM and CNN-LSTM models.This was particularly notable at the depth of 80–100 cm,where the fitness(R^(2))reached nearly 0.9298.Moreover,the root mean square error of the CLA model was reduced by 49%and 57%compared with those of the LSTM and CNN-LSTM models,respectively.This study demonstrates that the integration of physical modeling and deep learning methods provides a more comprehensive and accurate understanding of spatial-temporal SM variations in the root zone.展开更多
Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water soluble ...Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water soluble and exchangeable(SE), weakly specific adsorbed(WSA), Fe and Mn oxides bound(OX) and organic bound(ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH 4Cl, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.展开更多
The emergence rate and vitality of maize are directly affected by the sowing depth,and the uniformity of this depth is an important performance indicator of a planter,while the effective soil surface height informatio...The emergence rate and vitality of maize are directly affected by the sowing depth,and the uniformity of this depth is an important performance indicator of a planter,while the effective soil surface height information acquisition is the prerequisite for ensuring the accuracy of sowing depth control.The soil surface height variation acquisition system of a precision corn planter often produces profiling errors when performing active profiling due to interference from ground debris.In this study,a multipoint soil surface height variation information acquisition system was investigated,which consists of a ranging sensor group and a microcontroller unit(MCU)using a data comparison and screening method.The structure and specifications of the ranging sensors were determined according to the soil surface height variation and debris size,and a nonessential profiling control program was developed.Performed tests on the information acquisition system indicated that the measurement accuracy of the system was 3 mm,and when advancing at a speed of 8 km/h,the accuracy of the profiling decision and the system stability were 97.1%and 94.1%,respectively,indicating that the system was capable of nonessential profile control.The designed ranging system could provide a reference for the design of a ground information acquisition system of precision planters with an active profiling mechanism.展开更多
Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spec...Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.展开更多
The quality of seedbed after sowing such as soil surface roughness is one of the key factors affecting the seedling emergence of rapeseed,which ultimately affected crop yield.However,the effect of soil surface roughne...The quality of seedbed after sowing such as soil surface roughness is one of the key factors affecting the seedling emergence of rapeseed,which ultimately affected crop yield.However,the effect of soil surface roughness on seedling emergence and yield of rapeseed is still unclear.In this study,field experiments at the experimental site of Jianli and Shayang were carried out.Three treatments were designed:relative slow(M1),medium(M2),and fast(M3)forward speed of the unit.Soil surface roughness measured by a 3D laser scanner,seed quantity of the seeder,emergence rate and yield of rapeseed were determined to investigate the soil surface roughness effect on emergence rate and yield of rapeseed.The results showed that as the forward speed of the unit increased,the compartment surface became rougher.Compared with the M1 and M2 treatments,soil surface roughness under the M3 treatment increased by 36.5%and 9.8%,respectively.The actual seed quantity of the seeder under different treatments ranged from 3806.56 to 4158.18 g/hm2.The average error rate of the actual and theoretical seed quantity was less than 5%,which met the operational quality requirements for seeding rapeseed crops.As the forward speed of the unit increased,the actual seed quantity of the seeder gradually increased while the emergence rate and yield of rapeseed decreased.The seed quantity under the M3 treatment increased by 6.9%and 4.7%,while the emergence rate of rapeseed decreased by 3.3%and 2.0%,and the yield decreased by 23.2%and 13.1%,compared with the M1 and M2 treatments,respectively.Correlation analysis indicated that emergence rate and yield of rapeseed were negatively influenced by soil surface roughness.Considering rapeseed emergence rate,seed yield,and economic benefits,the M1 treatment was recommended.But considering the factor that the M1 treatment may reduce the unit operation efficiency,and thus resulting in lower cost of production,M2 could be recommended in actual farming.The results of this study laid a theoretical foundation for analyzing the relationship between the seedbed surface quality and seedling emergence and yield.展开更多
e penetrative depth in undisturbed surface soil is within 4 mm.7￣Be activity shows exponential decrease with soil depth, which is expressed as a diffusion process.7￣Be penetrative depth in undisturbed surface soil i...e penetrative depth in undisturbed surface soil is within 4 mm.7￣Be activity shows exponential decrease with soil depth, which is expressed as a diffusion process.7￣Be penetrative depth in undisturbed surface soil is apparently deeper in the fall (0.22-0.37 g cm￣(-2) than in the spring (0.11-0.28 g cm￣(-2) at the same site; Whereas, ￣7Be apparent activity at the top of surface soil is higher in the spring (0.3-2.2 Bq g￣(-1_) than in the fall (0.2-0.5 Bq g￣(-1) at the same site. The ￣7Be inventory (189-544 Bq m￣(-2) changes with both locations and seasons. Although the ￣7Be flux to the earth's surface increases with amount of precipitation, its maximum inventory in the soil profiles decreases to 30%-40% after the rainy period. Calculated by the diffusion equation, the erosion and accumulation rates of soil particles are agreeable with the observation in situ., which shows that the rates in fall are 1.5 times those in spring. The eroded soil particles almost all have been removed on the tablelands rather than transported into the drainage system. This indicstes that the soil erosion process in the karst region is only partial transportation within a short distance.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
Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and th...Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and the underlying mechanisms that stabilize SOC.In this study,density fractionation and acid hydrolysis were used to assess the spatial variation in SOC,the heavy fraction of organic carbon(HFOC),and the resistant organic carbon(ROC)in soils of the southern Hulun Buir region,northeastern China,and to identify the major factors that contribute to this variation.The results showed that as the contents of clay and silt particles(0–50μm)increased,both methylene blue(MB)adsorption by soil minerals and microaggregate contents increased in the 0–20 and 20–40 cm soil layers(P<0.05).Although varying with vegetation types,SOC,HFOC,and ROC contents increased significantly with the content of clay and silt particles, MB adsorption by soil minerals,and microaggregate content(P<0.05),suggesting that soil texture,the MB adsorption by soil minerals,and microaggregate abundance might be important factors influencing the spatial heterogeneity of carbon contents in soils of the southern Hulun Buir region.展开更多
基金supported by the National Natural Science Foundation of China (41271288, 41371273)
文摘As an important parameter in the soil erosion model, soil surface roughness（SSR） is used to quantitatively describe the micro-relief on agricultural land. SSR has been extensively studied both experimentally and theoretically; however, no studies have focused on understanding SSR on the Loess Plateau of China. This study investigated changes in SSR for three different tillage practices on the Loess Plateau of China and the effects of SSR on runoff and erosion yield during simulated rainfall. The tillage practices used were zero tillage（ZT）, shallow hoeing（SH） and contour ploughing（CP）. Two rainfall intensities were applied, and three stages of water erosion processes（splash erosion（I）, sheet erosion（II） and rill erosion（III）） were analyzed for each rainfall intensity. The chain method was used to measure changes in SSR both initially and after each stage of rainfall. A splash board was used to measure the splash erosion at stage I. Runoff and sediment data were collected continuously at 2-min intervals during rainfall erosion stages II and III. We found that SSR of the tilled surfaces ranged from 1.0% to 21.9% under the three tillage practices, and the order of the initial SSR for the three treatments was ZT〈SH〈CP. For the ZT treatment, SSR increased slightly from stage I to III, whereas for the SH and CP treatments, SSR decreased by 44.5% and 61.5% after the three water erosion stages, respectively, and the greatest reduction in SSR occurred in stage I. Regression analysis showed that the changes in SSR with increasing cumulative rainfall could be described by a power function（R2〉0.49） for the ZT, SH and CP treatments. The runoff initiation time was longer in the SH and CP treatments than in the ZT treatment. There were no significant differences in the total runoff yields among the ZT, SH and CP treatments. Sediment loss was significantly smaller（P〈0.05） in the SH and CP treatments than in the ZT treatment.
基金supported by the Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering (No. KLIEEE-09-04)the Liaoning Doctoral Funds (No. 20111076)
文摘The effect of nanometer anatase TiO2 was investigated on the photocatalytic degradation of phenanthrene on soil surfaces under a variety of conditions. After being spiked with phenanthrene, soil samples loaded with different amounts of TiO2 （0 wt.%, 1 wt.%, 2 wt.%, 3 wt.%, and 4 wt.%） were exposed to UV-light irradiation for 25 hr. The results indicated that the photocatalytic degradation of phenanthrene followed the pseudo first-order kinetics. TiO2 significantly accelerated the degradation of phenanthrene with the half-life reduced from 45.90 to 31.36 hr for TiO2 loading of 0 wt.% and 4 wt.%, respectively. In addition, the effects of H202, light intensity and humic acid on the degradation of phenanthrene were investigated. The degradation of phenanthrene increased with the concentration of H202, light intensity and the concentration of humic acids. It has been demonstrated that the photocatalytic method in the presence of nanometer anatase TiO2 was a very promising technology for the treatments of soil polluted with organic substances in the future.
基金supported by the National Natural Science Foundation of China(Grant No40901138)the Project of the State Key Laboratory of Earth Surface Processes and Resource Ecology(Grant No 2008-KF-05)the Project of the State Key Laboratory of Soil Erosion and Dryland Farming on the Loess Plateau(Grant No10501-283)
文摘The soil surface roughness and hydraulic roughness coefficient are important hydraulic resistance characteristic parameters. Precisely estimating the hydraulic roughness coefficient is important to understanding mechanisms of overland flow. Four tillage practices, including cropland raking, artificial hoeing, artificial digging, and straight slopes, were considered based on the local agricultural conditions to simulate different values of soil surface roughness in the Loess Plateau. The objective of this study was to investigate the relationship between the soil surface roughness and hydraulic roughness coefficient on sloping farmland using artificial rainfall simulation. On a slope with a gradient of 10°, a significant logarithmic function was developed between the soil surface roughness and Manning＇s roughness coefficient, and an exponential function was derived to describe the relationship between the soil surface roughness and Reynolds number. On the slope with a gradient of 15°, a significant power function was developed to reflect the relationship between the soil surface roughness and Manning＇s roughness coefficient, and a linear function was derived to relate the soil surface roughness to the Reynolds number. These findings can provide alternative ways to estimate the hydraulic roughness coefficient for different types of soil surface roughness.
基金financial support from the Applied Research Project in the Public Interest of Zhejiang Province (Nos: 2013C32106, 2015C32071)the Fundamental Research Funds for the Central Non-profit Research Institution of CAF (No. RISF61252)the Special Fund for Forestry Scientific Research in the Public Interest (No. 201304705)
文摘Phoxim（emulsifiable concentrate（EC） and granules（G）） has been widely used in bamboo forests. The persistence and magnitude of phoxim residues in the crop and soil must be investigated to ensure human and environmental safety. The environmental behaviors of the two formulations were investigated in a bamboo forest under soil surface mulching conditions（CP） and non-covered cultivation conditions（NCP）. The half-lives of phoxim in soil under the two conditions in soil were 4.1–6.2 days（EC） and 31.5–49.5 days（G）,respectively. Phoxim in EC could be leached from the topsoil into the subsoil. A minimized leaching effect was observed for G under NCP. Inversely, an enhanced leaching effect was observed for G under CP. The G formulation resulted in more parent compound（in bamboo shoots） and metabolite（in soil） residues of phoxim than in the case of EC, especially under CP conditions. In addition, the intensity and duration of the formulation effect on soil p H adjustment from G were more obvious than that from EC. Results showed that the environmental behaviors（distribution, degradation, residue） of phoxim in the bamboo forest were significantly influenced by the type of formulation. The prolongation effect from phoxim G might cause persistence and long-term environmental risk. However,bamboo shoot consumption could be considered relatively safe after applying the recommended dose of the two phoxim formulations.
基金supported by the National Science Foundation for Young Scholars of China(No.41101474)the Open Foundation of Key Laboratory of Industrial Ecology and Environmental Engineering(No.KLIEEE-09-04)+1 种基金the Liaoning Doctoral Funds(No.20111076)Liaoning University Environment Institute Key Discipline Project(No.2012J-001)
文摘Photolysis of some polycyclic aromatic hydrocarbons （PAHs） on soil surfaces may play an important role in the fate of PAHs in the environment.Photolysis of PAHs on soil surfaces under UV irradiation was investigated.The effects of oxygen,irradiation intensity and soil moisture on the degradation of the three PAHs were observed.The results showed that oxygen,soil moisture and irradiation intensity enhanced the photolysis of the three PAHs on soil surfaces.The degradation of the three PAHs on soil surfaces is related to their absorption spectra and the oxidation-half-wave potential.The photolysis of PAHs on soil surfaces in the presence of oxygen followed pseudo first-order kinetics.The photolysis half-lives ranged from 37.87 days for benzo[a]pyrene to 58.73 days for phenanthrene.The results indicate that photolysis is a successful way to remediate PAHs-contaminated soils.
基金supported by National Natural Science Foundation of China (40801001,40671010,40701054)National Key Technologies R&D Program of China during the 11th Five-Year Plan Period (2007BAD46B01)
文摘Spatial variation in soil surface CO2 efflux was measured in a stand of Populus euphratica in the Ejina Oasis of desert riparian forest in the extreme arid region in northwestern China from April 2007 through October 2007.Measurements were taken with a gas-exchange analyzer linked to a soil-respiration chamber.The mean soil CO2 efflux in the stand was 2.71 μmol/(m2·s) during the growing season and 1.38 μmol/(m2·s) in the nongrowing season.The seasonal maximum (end of May through early June) andminimum (October) CO2 efflux were 3.38 and 0.69 μmol/(m2·s),respectively.The diurnal fluctuation of CO2 efflux was relatively small (< 20 percent),with theminimum appearing around 05:00 and the maximum around 15:00.Linear regression analysis showed soil-surface CO2 efflux to be most highly correlated with soil temperature (R2=0.435) and soil moisture (R2=0.213).When all variables were considered simultaneously,only soil temperature (R2=0.378),soil moisture (R2=0.147),and root volume density (R2=0.021) explained a significant amount of variance in soil surface CO2 efflux.Stand volumes were not correlated with soil CO2 efflux on our sites.
基金The research was funded by a NCASI grant to S.T. Gower. Wang CK was supported by Innovated Talent Program of Northeast Forestry University (2004-07)
文摘Safe and economical disposal of paper mill sludge is a key consideration for forest products industry. A study was conducted to examine the effects of amendments of sludge and nutrients on soil surface CO2 flux （Rs） in northern hardwood forests and to quantify the relationship among Rs, soil temperature, and moisture in these stands. The experiment was a randomized complete block design that included sludge-amended, fertilized, and control treatments in sugar maple （Acer saccharum Marsh） dominated hardwood forests in the Upper Peninsula of Michigan, USA. Results showed that Rs was positively correlated to soil temperature （R^2 = 0.80, p 〈 0.001）, but was poorly correlated to soil moisture. Soil moisture positively affected the Rs only in the sludge-amended treatment. The Rs was significantly greater in the sludge-amended treatment than in the fertilized （p = 0.033） and the control （p = 0.048） treatments. The maximum Rs in the sludge-amended treatment was 8.8 μmol CO2 · m^ 2. s^-1, 91% and 126% greater than those in the fertilized （4.6 μmol CO2 · m^-2· s^-1） and control （3.9 μmol CO2· m^- 2· s^-1） treatments, respectively. The Rs did not differ significantly between the fertilized and control treatments. The difference in Rs between sludge-amended and the other treatments decreased with time following treatment.
基金supported by the National Natural Science Foundation of China (Grant No 60571058)the Specialized Research Fund for the Doctoral Program of Higher Education Institutions of China (Grant No 20070701010)
文摘Electromagnetic scattering from a rough surface of layered medium is investigated, and the formulae of the scattering coefficients for different polarizations are derived using the small perturbation method. A rough surface with exponential correlation function is presented for describing a rough soil surface of layered medium, the formula of its scattering coefficient is derived by considering the spectrum of the rough surface with exponential correlation function; the curves of the bistatic scattering coefficient of HH polarization with variation of the scattering angle are obtained by numerical calculation. The influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the roughness surface parameters and the frequency of the incident wave on the blstatic scattering coefficient is discussed. Numerical results show that the influence of the permittivity of layered medium, the mean layer thickness of intermediate medium, the rms and the correlation length of the rough surface, and the frequency of the incident wave on the bistatic scattering coefficient is very complex.
文摘Soil surface wetness is indispensable land surface parameter in agriculture, hydrology and environmental engineering. This paper explores the relationship between surface radiant temperature and fractional vegetation cover derived from satellite imagery to estimate soil surface wetness (triangle method) in Allahabad district. The pixel distributions create triangular shapes because the range of surface radiant temperature decreases as the amount of vegetation cover increases and sufficient number of pixels exists. A very weak correlation is found between the simulated soil surface wetness and ground measured soil moisture at deeper soil layers (R<sup>2</sup> < 0.15) on all the dates under investigation. This is because the drying rates at the surface discontinue to be linearly correlated to that at lower levels (depths). The standing water pixels distort the shape of the triangle especially at lower left edge of the triangle. This distortion is removable. The spatial and temporal inhomogeneity of soil surface wetness is examined.
基金funded by the National Natural Science Foundation of China(42461053)the Department of Education of Gansu Province:Higher Education Innovation Fund Project(2023B-064)+1 种基金the Youth Doctoral Fund Project(2024QB-014)the Natural Science Foundation of Gansu Province(25JRRA012).
文摘Spatiotemporal forecasting of surface soil moisture(SSM)is recognized as a critical scientific issue in precision agricultural irrigation,regional drought monitoring,and early warning systems for extreme precipitation.However,long-term forecasting continues to pose formidable challenges because of the complexity observed across both the spatial and temporal scales.In this study,we used a daily SSM dataset at a 0.05°×0.05°spatial resolution over the Qilian Mountains,China and proposed a hybrid Convolutional Long Short-Term Memory(ConvLSTM)-Nudging model,which combined deep neural networks with data assimilation to increase the accuracy of long-term SSM forecasting.We trained and evaluated the SSM predictive performance of four models(Convolutional Neural Network(CNN),Long Short-Term Memory(LSTM),ConvLSTM,and ConvLSTM with Squeeze-and-Excitation(SE)attention mechanism(ConvLSTM-SE))in both short-term and long-term scenarios.The results showed that all the models perform well under short-term predictions,but the accuracy decrease substantially in long-term predictions.Therefore,we integrated Nudging technique during the long-term prediction phase to assimilate observational information and rectify model biases.Comprehensive evaluations demonstrate that Nudging significantly improves all the models,with ConvLSTM-Nudging achieving the best performance under the 200-d forecasting scenario.Relative to those of the best-performing ConvLSTM model for long-term forecasts,when observation noiseδ=0.00 and observation fraction obs=50.0%,the coefficient of determination(R2)of ConvLSTM-Nudging increases by approximately 82.1%,while its mean absolute error(MAE)and root mean squared error(RMSE)decrease by approximately 84.8%and 77.3%,respectively;the average Pearson correlation coefficient(r)improves by approximately 23.6%,and Bias is reduced by 98.1%.These results demonstrated that although pure deep learning models achieve high accuracy in the short-term predictions,they are prone to error accumulation and systematic drift in long-term autoregressive predictions.Integrating data assimilation with deep learning and continuously correcting the state through observation can effectively suppress long-term biases,thereby achieving robust long-term SSM forecasting.
基金supported by the National Natural Science Foundation of China(51769013,52168052)。
文摘Intense evaporation in areas with loess-like sulfate saline soils has resulted in significant ecological challenges that include water shortages and soil salinization.Investigating evaporation rate in loess-like sulfate saline soils under varying salt contents carries crucial implications for understanding regional water loss processes,predicting soil salinization advancement,and formulating effective ecological management strategies.Therefore,this study sampled the loess-like sulfate saline soil that is widely distributed in western China as experimental materials and investigated the impact of different initial salt contents(0.00%,0.50%,1.50%,3.00%,and 5.00%)on the evaporation rate,water content,and temperature of soil.The results showed that the evaporation rate decreased with increasing initial salt content.After a salt accumulation layer formed on the soil surface,the water content of the surface soil fluctuated.An increase in the initial salt content resulted in a corresponding increase in the surface temperature.Considering the evaporation characteristics of loess-like sulfate saline soil and the impact of an anomalous increase in surface soil water content on soil surface resistance,this study proposed a modified evaporation model on the basis of Fujimaki's evaporation model of saline soil by introducing a correction coefficientβto modify the soil surface resistance.A comparison of the calculated evaporation rates before and after the modification with the measured evaporation rates revealed a significant improvement in the calculation accuracy of the modified model,indicating that the modified model is capable of more accurately simulating the evaporation rate of sulfate saline soil with different initial salt contents.This paper proposes an effective method for calculating the evaporation rate of loess-like sulfate saline soils,providing a theoretical basis for evaporation research in saline soil.
基金the National Natural Science Foundation of China(Grant No.42207171).
文摘Understanding water dynamics under the effect of climatic conditions is important to improve water sustainability over the medium-and long-term.Clay content can affect soil hydrothermal properties,and hence modify water and heat exchange between soil and atmosphere,e.g.evapotranspiration and infiltration.This work aims to develop a numerical approach to explore the influence of clay content on soil hydrothermal response to the timely climatic conditions in the Lake Chad region,Sahel Region of west-central Africa.The meteorological information at the studied points,i.e.points A and B with a clay content of 8.3%and 25%,during the year 2008 is collected from ERA5-Land hourly data.The numerical results allow for understanding the effect of clay content on the hydrothermal response of the surface soil layer.Specifically,the soil surface temperature under point A is lower than that under point B during the dry season due to the dominant effect of heat conduction.However,the converse tendency is observed during the wet season because of the combined effect of heat conduction and latent heat.The variations of soil volumetric water content are closely related to the timely interaction between the soil and atmosphere,in addition to the hydrothermal properties of soil.Moreover,the outcomes of this work improve the understanding of the heat and water dynamics under the effect of climatic conditions and clay content,and provide further insights into the potential water protection in arid and semi-arid regions in the future.
基金supported by the National Natural Science Foundation of China(No.42061065)the Third Xinjiang Comprehensive Scientific Expedition,China(No.2022xjkk03010102).
文摘Root zone soil moisture(RZSM)plays a critical role in land-atmosphere hydrological cycles and serves as the primary water source for vegetation growth.However,the correlations between RZSM and its associated variables,including surface soil moisture(SSM),often exhibit nonlinearities that are challenging to identify and quantify using conventional statistical techniques.Therefore,this study presents a hybrid convolutional neural network(CNN)-long short-term memory neural network(LSTM)-attention(CLA)model for predicting RZSM.Owing to the scarcity of soil moisture(SM)observation data,the physical model Hydrus-1D was employed to simulate a comprehensive dataset of spatial-temporal SM.Meteorological data and moderate resolution imaging spectroradiometer vegetation characterization parameters were used as predictor variables for the training and validation of the CLA model.The results of the CLA model for SM prediction in the root zone were significantly enhanced compared with those of the traditional LSTM and CNN-LSTM models.This was particularly notable at the depth of 80–100 cm,where the fitness(R^(2))reached nearly 0.9298.Moreover,the root mean square error of the CLA model was reduced by 49%and 57%compared with those of the LSTM and CNN-LSTM models,respectively.This study demonstrates that the integration of physical modeling and deep learning methods provides a more comprehensive and accurate understanding of spatial-temporal SM variations in the root zone.
文摘Speciation and fractionation of heavy metals in soil subsamples experimentally loaded with Pb, Cd, Cu and Zn in orthogonal design was investigated by sequential extraction, and operationally defined as water soluble and exchangeable(SE), weakly specific adsorbed(WSA), Fe and Mn oxides bound(OX) and organic bound(ORG). The results showed that fractions of heavy metals in the soil subsamples depended on their speciation. About 90% of Cd and 75% of Zn existed in soil subsamples in the SE fraction. Lead and Cu existed in soil subsamples as SE, WSA and OX fractions simultaneously, although SE was still the major fraction. Organic bound heavy metals were not clearly apparent in all the soil subsamples. The concentration of some heavy metal fractions in soil subsamples showed the good correlation with ionic impulsion of soil, especially for the SE fraction. Continuous saturation of soil subsamples with 0.20 mol/L NH 4Cl, which is the first step for determination of the negative surface charge of soil by the ion retention method, resulted in desorption of certain heavy metals from the soil. It was found that the percentage desorption of heavy metals from soil subsamples depended greatly on pH, the composition and original heavy metal content of the soil subsamples. However, most of the heavy metals in the soil subsamples were still be retained after multiple saturation. Compared with the parent soil, the negative surface charge of soil subsamples loaded with heavy metals did not show difference significantly from that of the parent one by statistical analysis. Heavy metals existed in the soil subsamples mainly as exchangeable and precipitated simultaneously.
基金This study was financially supported by the Special Funding Project for Public Welfare Industries(Agriculture)Scientific Research:Research on Mechanized Cultivation Model in Maize Planting Area of State Farm(201503116-04-04)and conducted in the Conservation Tillage Technology Center of the Heilongjiang Provincial Education Department jointly established by both corporations and universities.
文摘The emergence rate and vitality of maize are directly affected by the sowing depth,and the uniformity of this depth is an important performance indicator of a planter,while the effective soil surface height information acquisition is the prerequisite for ensuring the accuracy of sowing depth control.The soil surface height variation acquisition system of a precision corn planter often produces profiling errors when performing active profiling due to interference from ground debris.In this study,a multipoint soil surface height variation information acquisition system was investigated,which consists of a ranging sensor group and a microcontroller unit(MCU)using a data comparison and screening method.The structure and specifications of the ranging sensors were determined according to the soil surface height variation and debris size,and a nonessential profiling control program was developed.Performed tests on the information acquisition system indicated that the measurement accuracy of the system was 3 mm,and when advancing at a speed of 8 km/h,the accuracy of the profiling decision and the system stability were 97.1%and 94.1%,respectively,indicating that the system was capable of nonessential profile control.The designed ranging system could provide a reference for the design of a ground information acquisition system of precision planters with an active profiling mechanism.
基金Under the auspices of the Excellent Youth Talent Project of Jilin Science and Technology Development Program(No.20170520078JH)Science and Technology Basic Work of Science and Technology(No.2014FY210800–4)National Natural Science Foundation of China(No.41601382)
文摘Soil surface roughness, denoted by the root mean square height(RMSH), and soil moisture(SM) are critical factors that affect the accuracy of quantitative remote sensing research due to their combined influence on spectral reflectance(SR). In regards to this issue, three SM levels and four RMSH levels were artificially designed in this study; a total of 12 plots was used, each plot had a size of 3 m × 3 m. Eight spectral observations were conducted from 14 to 30 October 2017 to investigate the correlation between RMSH, SM, and SR. On this basis, 6 commonly used bands of optical satellite sensors were selected in this study, which are red(675 nm), green(555 nm), blue(485 nm), near infrared(845 nm), shortwave infrared 1(1600 nm), and shortwave infrared 2(2200 nm). A negative correlation was found between SR and RMSH, and between SR and SM. The bands with higher coefficient of determination R^2 values were selected for stepwise multiple nonlinear regression analysis. Four characterized bands(i.e., blue, green, near infrared, and shortwave infrared 2) were chosen as the independent variables to estimate SM with R^2 and root mean square error(RMSE) values equal to 0.62 and 2.6%, respectively. Similarly, the four bands(green, red, near infrared, and shortwave infrared 1) were used to estimate RMSH with R^2 and RMSE values equal to 0.48 and 0.69 cm, respectively. These results indicate that the method used is not only suitable for estimating SM but can also be extended to the prediction of RMSH. Finally, the evaluation approach presented in this paper highly restores the real situation of the natural farmland surface on the one hand, and obtains high precision values of SM and RMSH on the other. The method can be further applied to the prediction of farmland SM and RMSH based on satellite and unmanned aerial vehicle(UAV) optical imagery.
基金This work was financially supported by the China Postdoctoral Science Foundation(Grant No.2020M672371)the National Key Research and Development Program of China(Grant No.2018YFD0200901)+1 种基金the Postdoctoral Science and Technology Activities project of Hubei Provincethe Talent Introduction Project of Xihua University(Grant No.Z221029).
文摘The quality of seedbed after sowing such as soil surface roughness is one of the key factors affecting the seedling emergence of rapeseed,which ultimately affected crop yield.However,the effect of soil surface roughness on seedling emergence and yield of rapeseed is still unclear.In this study,field experiments at the experimental site of Jianli and Shayang were carried out.Three treatments were designed:relative slow(M1),medium(M2),and fast(M3)forward speed of the unit.Soil surface roughness measured by a 3D laser scanner,seed quantity of the seeder,emergence rate and yield of rapeseed were determined to investigate the soil surface roughness effect on emergence rate and yield of rapeseed.The results showed that as the forward speed of the unit increased,the compartment surface became rougher.Compared with the M1 and M2 treatments,soil surface roughness under the M3 treatment increased by 36.5%and 9.8%,respectively.The actual seed quantity of the seeder under different treatments ranged from 3806.56 to 4158.18 g/hm2.The average error rate of the actual and theoretical seed quantity was less than 5%,which met the operational quality requirements for seeding rapeseed crops.As the forward speed of the unit increased,the actual seed quantity of the seeder gradually increased while the emergence rate and yield of rapeseed decreased.The seed quantity under the M3 treatment increased by 6.9%and 4.7%,while the emergence rate of rapeseed decreased by 3.3%and 2.0%,and the yield decreased by 23.2%and 13.1%,compared with the M1 and M2 treatments,respectively.Correlation analysis indicated that emergence rate and yield of rapeseed were negatively influenced by soil surface roughness.Considering rapeseed emergence rate,seed yield,and economic benefits,the M1 treatment was recommended.But considering the factor that the M1 treatment may reduce the unit operation efficiency,and thus resulting in lower cost of production,M2 could be recommended in actual farming.The results of this study laid a theoretical foundation for analyzing the relationship between the seedbed surface quality and seedling emergence and yield.
文摘e penetrative depth in undisturbed surface soil is within 4 mm.7￣Be activity shows exponential decrease with soil depth, which is expressed as a diffusion process.7￣Be penetrative depth in undisturbed surface soil is apparently deeper in the fall (0.22-0.37 g cm￣(-2) than in the spring (0.11-0.28 g cm￣(-2) at the same site; Whereas, ￣7Be apparent activity at the top of surface soil is higher in the spring (0.3-2.2 Bq g￣(-1_) than in the fall (0.2-0.5 Bq g￣(-1) at the same site. The ￣7Be inventory (189-544 Bq m￣(-2) changes with both locations and seasons. Although the ￣7Be flux to the earth's surface increases with amount of precipitation, its maximum inventory in the soil profiles decreases to 30%-40% after the rainy period. Calculated by the diffusion equation, the erosion and accumulation rates of soil particles are agreeable with the observation in situ., which shows that the rates in fall are 1.5 times those in spring. The eroded soil particles almost all have been removed on the tablelands rather than transported into the drainage system. This indicstes that the soil erosion process in the karst region is only partial transportation within a short distance.
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Project supported by the National Natural Science Foundation of China(Nos.40321101 and 40071036)the Major State Basic Research Development Program of China(973 Program)(No.2002CB412503)
文摘Soil organic carbon(SOC)can act as a sink or source of atmospheric carbon dioxide;therefore,it is important to understand the amount and composition of SOC in terrestrial ecosystems,the spatial variation in SOC,and the underlying mechanisms that stabilize SOC.In this study,density fractionation and acid hydrolysis were used to assess the spatial variation in SOC,the heavy fraction of organic carbon(HFOC),and the resistant organic carbon(ROC)in soils of the southern Hulun Buir region,northeastern China,and to identify the major factors that contribute to this variation.The results showed that as the contents of clay and silt particles(0–50μm)increased,both methylene blue(MB)adsorption by soil minerals and microaggregate contents increased in the 0–20 and 20–40 cm soil layers(P<0.05).Although varying with vegetation types,SOC,HFOC,and ROC contents increased significantly with the content of clay and silt particles, MB adsorption by soil minerals,and microaggregate content(P<0.05),suggesting that soil texture,the MB adsorption by soil minerals,and microaggregate abundance might be important factors influencing the spatial heterogeneity of carbon contents in soils of the southern Hulun Buir region.
