In the past few decades, the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland, China, due to population growth and shift in the socio-economic system. Two sites...In the past few decades, the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland, China, due to population growth and shift in the socio-economic system. Two sites with different grazing intensities, continuous grazing site （CG） with 1.2 sheep ha-1 year-1 and heavy grazing site （HG） with 2.0 sheep ha-1 year-1, were investigated at the Inner Mongolia Grassland Ecosystem Research Station （43° 37′ 50″ N, 116° 42′ 18″ E） situated in the northern China to i） characterize the temporal distribution of soil water content along soil profile; and ii） quantify the water fluxes as affected by grazing intensity. Soil water content was monitored by time domain refiectometry （TDR） probes. Soil water retention curves were determined by pressure membrane extractor, furthermore processed by RETC （RETention Curve） software. Soil matric potential, plant available water and water flux were calculated using these data. Both sites showed an identical seasonal soil water dynamics within four defined hydraulic periods： i） wetting transition coincided with a dramatic water increase due to snow and frozen soil thawing from March to April; 2） wet summer, rainfall in accordance with plant growth from May to September; 3） drying transition, a decrease of soil water from October to November due to rainfall limit; and 4） dry winter, freezing from December to next February. Heavy grazing largely reduced soil water content by 43%-48% and plant available water by 46%-61% as compared to the CG site. During growing season net water flux was nearly similar between HG （242 mm） and CG （223 mm） sites between 5 and 20 cm depths. However, between 20 and 40 cm depths, the upward flux was more pronounced at HG site than at CG site, indicating that water was depleted by root uptake at HG site but stored at CG site. In semi-arid grassland ecosystem, grazing intensity can affect soil water regime and flux, particularly in the growing season.展开更多
Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving ...Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving crop growth are not well understood. The objectives of this study were i) to determine the crop responses to biochar addition and ii) to understand the effect of biochar addition on N use efficiency. Seven acidic red soils varying in texture, p H, and soil nutrient were taken from southern China and subjected to four treatments: zero biochar and fertilizer as a control(CK), 10 g kg-1biochar(BC), NPK fertilizers(NPK), and 10 g kg-1biochar plus NPK fertilizers(BC+NPK).15N-labeled fertilizer was used as a tracer to assess N use efficiency. After a 46-d pot experiment,biochar addition increased soil p H and available P, and decreased soil exchangable Al3+, but did not impact soil availabe N and cation exchange capacity(P > 0.05). The N use efficiency and N retained in the soil were not significantly affected by biochar application except for the soil with the lowest available P(3.81 mg kg-1) and highest exchanageable Al3+(4.54 cmol kg-1). Greater maize biomass was observed in all soils amended with biochar compared to soils without biochar(BC vs. CK, BC+NPK vs. NPK). This agronomic effect was negatively related to the concentration of soil exchangeable Al3+(P < 0.1). The results of this study implied that the liming effect of biochar improved plant growth through alleviating Al toxicity and P deficiency, especially in poor acidic red soils.展开更多
Undisturbed soil cores were taken from different slope positions （upslope, backslope and footslope） and soil depths （0-15, 20-35 and 100-115 cm） in a soil catena derived from Quaternary red clay to determine the s...Undisturbed soil cores were taken from different slope positions （upslope, backslope and footslope） and soil depths （0-15, 20-35 and 100-115 cm） in a soil catena derived from Quaternary red clay to determine the spatial changes in soil strength along the eroded slope and to ewluate an indicator to determine soil strength during compaction. Precompression stress, as an indicator of soil strength, significantly increased from topsoil layer to subsoil layer （P 〈0.05） and was affected by slope position. In the subsoil layer （20-35 cm）, the precompression stress at the footslope position was significantly greater than at the backslope and upslope positions （P 〈0.05）, while there were no significant differences at 0-15 and 100-115 cm. Precompression stress followed the spatial wriation of soil clay content with soil depth and had a significant linear relationship with soil porosity （r^2 = 0.40, P 〈 0.01）. Also, soil cohesion increased with increasing soil clay content. The precompression stress was significantly related to the applied stress corresponding to the highest change of pore water pressure （r^2 = 0.69, P 〈 0.01）. These results suggested that soil strength induced by soil erosion and soil management wried spatially along the slope and the maximum change in pore water pressure during compaction could be an easy indicator to describe soil strength.展开更多
Pseudo-pure state(PPS)preparation is crucial in nuclear magnetic resonance quantum computation.There have been some methods in spin-1/2 systems and a few attempts in quadrupolar spin systems.As optimal control via gra...Pseudo-pure state(PPS)preparation is crucial in nuclear magnetic resonance quantum computation.There have been some methods in spin-1/2 systems and a few attempts in quadrupolar spin systems.As optimal control via gradient ascent pulses engineering(GRAPE)has been widely used in quantum information science,we apply this technique to PPS preparation in quadrupolar spin systems.This approach shows an effective and fast quantum control method for both the state preparation and the realization of quantum gates in quadrupolar systems.展开更多
【目的】砂姜黑土表现出湿时泥泞,干时僵硬的物理性质,探究砂姜黑土的抗压强度对于土壤结构保护和农机作业时间选择具有重要意义。【方法】以砂姜黑土为研究对象,设置5个不同的土壤含水量水平(田间持水量的100%、85%、70%、55%及40%),以...【目的】砂姜黑土表现出湿时泥泞,干时僵硬的物理性质,探究砂姜黑土的抗压强度对于土壤结构保护和农机作业时间选择具有重要意义。【方法】以砂姜黑土为研究对象,设置5个不同的土壤含水量水平(田间持水量的100%、85%、70%、55%及40%),以及3个土壤容重级别(1.2、1.4和1.6 g cm^(-3)),采用高压固结仪进行单轴压缩试验,分析土壤含水量(θ)和容重(ρ)对抗压强度(σ_(p))的耦合影响。【结果】Van Genuchten方程拟合土壤压实曲线效果良好(R^(2)>0.99)。砂姜黑土耕层土壤的抗压强度范围为15.2~150.6 kPa,且受到土壤含水量和容重以及二者交互作用的显著影响(P<0.05)。当土壤含水量≥70%田间持水量且初始容重≤1.4 g cm^(-3)时,农机装备的施加压力已经超过土壤抗压强度,压实风险较高。本研究采用MATLAB进行多元回归分析的方法,构建了土壤含水量、湿容重与抗压强度三者的土壤传递函数(σ_(p)=aexp(bθ+cρ),R^(2)=0.832,P<0.01)。【结论】土壤含水量与容重是调控砂姜黑土抗压强度的两个关键因素,建议选择土壤含水量较低且容重较大的时期进行农事操作。研究建立的土壤传递函数可以较好地预测砂姜黑土的抗压强度,研究结果可为农机具在田间作业时的压实风险评估及合理作业时机选择提供科学依据。展开更多
目的砂姜黑土湿时泥泞,干时僵硬,难耕难耙,适耕期短,研究砂姜黑土抗剪强度对于确定土壤适耕性具有重要意义。方法以砂姜黑土为研究对象,土壤容重设置1.2、1.4和1.6 g m^(-3)共3个水平,土壤含水量设置田间持水量的100%、85%、70%、55%和...目的砂姜黑土湿时泥泞,干时僵硬,难耕难耙,适耕期短,研究砂姜黑土抗剪强度对于确定土壤适耕性具有重要意义。方法以砂姜黑土为研究对象,土壤容重设置1.2、1.4和1.6 g m^(-3)共3个水平,土壤含水量设置田间持水量的100%、85%、70%、55%和40%共5个水平,采用直剪仪测定土壤抗剪强度参数(黏聚力,c;内摩擦角,ϕ),分析土壤剪切特性随土壤含水量(θ)和容重(ρ)的变化规律,并利用多元回归拟合建立土壤抗剪强度(τ)的传递函数。结果砂姜黑土黏聚力随土壤含水量增加呈现指数减小趋势,随土壤湿容重(ρ')增加呈线性增加趋势,三者关系能够用回归方程c=a1e(b1ρ´−c1θ)表示(R^(2)=0.984,P<0.001)。内摩擦角随土壤含水量增加先减小之后趋于稳定,随土壤湿容重增加而增加,表现出φ=a2e(b2ρ´/θ)(R^(2)=0.856,P<0.001)的规律性变化。参照Mohr-Coulomb抗剪强度公式,建立砂姜黑土的抗剪强度传递函数τ=a1e(b1ρ′+c1θ)+σtan(a2e(b2ρ′(θ)),该函数能够很好地表示砂姜黑土的抗剪强度变化规律(R^(2)=0.870,P<0.001)。结论土壤含水量和容重是砂姜黑土抗剪强度的两个重要影响因素,在此基础上构建了以土壤含水量和湿容重为自变量的砂姜黑土抗剪强度传递函数。本研究结果可为砂姜黑土结构和耕性改良提供科学依据。展开更多
【目的】近年来黑土地变硬的问题日益突出,已成为黑土退化的主要特征之一。明确土壤穿透阻力与水分状况之间的关系,以期为黑土地变硬的本底调查与诊断评价提供依据。【方法】以典型黑土为研究对象,选择白浆土作为对照,研究不同容重下土...【目的】近年来黑土地变硬的问题日益突出,已成为黑土退化的主要特征之一。明确土壤穿透阻力与水分状况之间的关系,以期为黑土地变硬的本底调查与诊断评价提供依据。【方法】以典型黑土为研究对象,选择白浆土作为对照,研究不同容重下土壤穿透阻力与水分含量的关系,构建土壤穿透阻力与水分含量和容重的传递函数,实现穿透阻力在不同土壤水分含量间的转换。为此,黑土的容重从1.0~1.5 g cm-3设置6个水平,白浆土从1.2~1.6g cm-3设置5个水平,土壤含水量按照田间持水量的40%~100%设置7个水平,测定不同组合下的土壤穿透阻力。【结果】土壤穿透阻力随土壤容重增大线性增加,随土壤含水量降低指数增加(P<0.01),白浆土的增加速率大于黑土。土壤容重和水分含量对穿透阻力存在显著的交互影响,低水分条件会加剧土壤容重对穿透阻力的影响,高土壤容重会增强土壤水分对穿透阻力的作用,土壤穿透阻力对土壤水分的敏感度显著高于容重,白浆土对两个因素的敏感度高于黑土,黑土容重和土壤水分含量的参数敏感性最大值分别为4.5和11.1,而白浆土则分别为7.0和15.1,白浆土变硬的风险高于黑土。土壤穿透阻力与容重和水分含量的关系可以用二元幂函数SPR=a×ρb×θc表达,该拟合函数下白浆土和黑土的决定系数均在0.95以上。【结论】利用构建的传递函数,实现了土壤穿透阻力在不同水分状况下的转换:同一种土壤平均容重下的转换系数可适用于其他容重条件;在不同土壤类型间,黑土某一容重下的转换系数,可用于相同容重下的白浆土,反之亦然。展开更多
基金Supported by the German Research Foundation(DFG)(No.Forschergruppe 536)the Hundred Talents Program of the Chinese Academy of Sciences
文摘In the past few decades, the increase in grazing intensity has led to soil degradation and desertification in Inner Mongolia grassland, China, due to population growth and shift in the socio-economic system. Two sites with different grazing intensities, continuous grazing site （CG） with 1.2 sheep ha-1 year-1 and heavy grazing site （HG） with 2.0 sheep ha-1 year-1, were investigated at the Inner Mongolia Grassland Ecosystem Research Station （43° 37′ 50″ N, 116° 42′ 18″ E） situated in the northern China to i） characterize the temporal distribution of soil water content along soil profile; and ii） quantify the water fluxes as affected by grazing intensity. Soil water content was monitored by time domain refiectometry （TDR） probes. Soil water retention curves were determined by pressure membrane extractor, furthermore processed by RETC （RETention Curve） software. Soil matric potential, plant available water and water flux were calculated using these data. Both sites showed an identical seasonal soil water dynamics within four defined hydraulic periods： i） wetting transition coincided with a dramatic water increase due to snow and frozen soil thawing from March to April; 2） wet summer, rainfall in accordance with plant growth from May to September; 3） drying transition, a decrease of soil water from October to November due to rainfall limit; and 4） dry winter, freezing from December to next February. Heavy grazing largely reduced soil water content by 43%-48% and plant available water by 46%-61% as compared to the CG site. During growing season net water flux was nearly similar between HG （242 mm） and CG （223 mm） sites between 5 and 20 cm depths. However, between 20 and 40 cm depths, the upward flux was more pronounced at HG site than at CG site, indicating that water was depleted by root uptake at HG site but stored at CG site. In semi-arid grassland ecosystem, grazing intensity can affect soil water regime and flux, particularly in the growing season.
基金Supported by the National Key Technology R&D Program of China(No.2011BAD31B04)the National Natural Science Foundation of China(Nos.41371235 and 41171191)
文摘Biochar added to soil can improve crop growth through both direct and indirect effects, particularly in acidic, highly weathered soils in subtropical and tropical regions. However, the mechanisms of biochar improving crop growth are not well understood. The objectives of this study were i) to determine the crop responses to biochar addition and ii) to understand the effect of biochar addition on N use efficiency. Seven acidic red soils varying in texture, p H, and soil nutrient were taken from southern China and subjected to four treatments: zero biochar and fertilizer as a control(CK), 10 g kg-1biochar(BC), NPK fertilizers(NPK), and 10 g kg-1biochar plus NPK fertilizers(BC+NPK).15N-labeled fertilizer was used as a tracer to assess N use efficiency. After a 46-d pot experiment,biochar addition increased soil p H and available P, and decreased soil exchangable Al3+, but did not impact soil availabe N and cation exchange capacity(P > 0.05). The N use efficiency and N retained in the soil were not significantly affected by biochar application except for the soil with the lowest available P(3.81 mg kg-1) and highest exchanageable Al3+(4.54 cmol kg-1). Greater maize biomass was observed in all soils amended with biochar compared to soils without biochar(BC vs. CK, BC+NPK vs. NPK). This agronomic effect was negatively related to the concentration of soil exchangeable Al3+(P < 0.1). The results of this study implied that the liming effect of biochar improved plant growth through alleviating Al toxicity and P deficiency, especially in poor acidic red soils.
基金Project supported by the Chinese Academy of Sciences and Max-Planck Foundation (No. 40071055) and the National Natural Science Foundation of China (No. 40071044)
文摘Undisturbed soil cores were taken from different slope positions （upslope, backslope and footslope） and soil depths （0-15, 20-35 and 100-115 cm） in a soil catena derived from Quaternary red clay to determine the spatial changes in soil strength along the eroded slope and to ewluate an indicator to determine soil strength during compaction. Precompression stress, as an indicator of soil strength, significantly increased from topsoil layer to subsoil layer （P 〈0.05） and was affected by slope position. In the subsoil layer （20-35 cm）, the precompression stress at the footslope position was significantly greater than at the backslope and upslope positions （P 〈0.05）, while there were no significant differences at 0-15 and 100-115 cm. Precompression stress followed the spatial wriation of soil clay content with soil depth and had a significant linear relationship with soil porosity （r^2 = 0.40, P 〈 0.01）. Also, soil cohesion increased with increasing soil clay content. The precompression stress was significantly related to the applied stress corresponding to the highest change of pore water pressure （r^2 = 0.69, P 〈 0.01）. These results suggested that soil strength induced by soil erosion and soil management wried spatially along the slope and the maximum change in pore water pressure during compaction could be an easy indicator to describe soil strength.
基金Supported by the Chinese Academy of Sciences,and the National Natural Science Foundation of China under Grant Nos 10975124,10834005,91021005.
文摘Pseudo-pure state(PPS)preparation is crucial in nuclear magnetic resonance quantum computation.There have been some methods in spin-1/2 systems and a few attempts in quadrupolar spin systems.As optimal control via gradient ascent pulses engineering(GRAPE)has been widely used in quantum information science,we apply this technique to PPS preparation in quadrupolar spin systems.This approach shows an effective and fast quantum control method for both the state preparation and the realization of quantum gates in quadrupolar systems.
文摘【目的】砂姜黑土表现出湿时泥泞,干时僵硬的物理性质,探究砂姜黑土的抗压强度对于土壤结构保护和农机作业时间选择具有重要意义。【方法】以砂姜黑土为研究对象,设置5个不同的土壤含水量水平(田间持水量的100%、85%、70%、55%及40%),以及3个土壤容重级别(1.2、1.4和1.6 g cm^(-3)),采用高压固结仪进行单轴压缩试验,分析土壤含水量(θ)和容重(ρ)对抗压强度(σ_(p))的耦合影响。【结果】Van Genuchten方程拟合土壤压实曲线效果良好(R^(2)>0.99)。砂姜黑土耕层土壤的抗压强度范围为15.2~150.6 kPa,且受到土壤含水量和容重以及二者交互作用的显著影响(P<0.05)。当土壤含水量≥70%田间持水量且初始容重≤1.4 g cm^(-3)时,农机装备的施加压力已经超过土壤抗压强度,压实风险较高。本研究采用MATLAB进行多元回归分析的方法,构建了土壤含水量、湿容重与抗压强度三者的土壤传递函数(σ_(p)=aexp(bθ+cρ),R^(2)=0.832,P<0.01)。【结论】土壤含水量与容重是调控砂姜黑土抗压强度的两个关键因素,建议选择土壤含水量较低且容重较大的时期进行农事操作。研究建立的土壤传递函数可以较好地预测砂姜黑土的抗压强度,研究结果可为农机具在田间作业时的压实风险评估及合理作业时机选择提供科学依据。
文摘目的砂姜黑土湿时泥泞,干时僵硬,难耕难耙,适耕期短,研究砂姜黑土抗剪强度对于确定土壤适耕性具有重要意义。方法以砂姜黑土为研究对象,土壤容重设置1.2、1.4和1.6 g m^(-3)共3个水平,土壤含水量设置田间持水量的100%、85%、70%、55%和40%共5个水平,采用直剪仪测定土壤抗剪强度参数(黏聚力,c;内摩擦角,ϕ),分析土壤剪切特性随土壤含水量(θ)和容重(ρ)的变化规律,并利用多元回归拟合建立土壤抗剪强度(τ)的传递函数。结果砂姜黑土黏聚力随土壤含水量增加呈现指数减小趋势,随土壤湿容重(ρ')增加呈线性增加趋势,三者关系能够用回归方程c=a1e(b1ρ´−c1θ)表示(R^(2)=0.984,P<0.001)。内摩擦角随土壤含水量增加先减小之后趋于稳定,随土壤湿容重增加而增加,表现出φ=a2e(b2ρ´/θ)(R^(2)=0.856,P<0.001)的规律性变化。参照Mohr-Coulomb抗剪强度公式,建立砂姜黑土的抗剪强度传递函数τ=a1e(b1ρ′+c1θ)+σtan(a2e(b2ρ′(θ)),该函数能够很好地表示砂姜黑土的抗剪强度变化规律(R^(2)=0.870,P<0.001)。结论土壤含水量和容重是砂姜黑土抗剪强度的两个重要影响因素,在此基础上构建了以土壤含水量和湿容重为自变量的砂姜黑土抗剪强度传递函数。本研究结果可为砂姜黑土结构和耕性改良提供科学依据。
文摘【目的】近年来黑土地变硬的问题日益突出,已成为黑土退化的主要特征之一。明确土壤穿透阻力与水分状况之间的关系,以期为黑土地变硬的本底调查与诊断评价提供依据。【方法】以典型黑土为研究对象,选择白浆土作为对照,研究不同容重下土壤穿透阻力与水分含量的关系,构建土壤穿透阻力与水分含量和容重的传递函数,实现穿透阻力在不同土壤水分含量间的转换。为此,黑土的容重从1.0~1.5 g cm-3设置6个水平,白浆土从1.2~1.6g cm-3设置5个水平,土壤含水量按照田间持水量的40%~100%设置7个水平,测定不同组合下的土壤穿透阻力。【结果】土壤穿透阻力随土壤容重增大线性增加,随土壤含水量降低指数增加(P<0.01),白浆土的增加速率大于黑土。土壤容重和水分含量对穿透阻力存在显著的交互影响,低水分条件会加剧土壤容重对穿透阻力的影响,高土壤容重会增强土壤水分对穿透阻力的作用,土壤穿透阻力对土壤水分的敏感度显著高于容重,白浆土对两个因素的敏感度高于黑土,黑土容重和土壤水分含量的参数敏感性最大值分别为4.5和11.1,而白浆土则分别为7.0和15.1,白浆土变硬的风险高于黑土。土壤穿透阻力与容重和水分含量的关系可以用二元幂函数SPR=a×ρb×θc表达,该拟合函数下白浆土和黑土的决定系数均在0.95以上。【结论】利用构建的传递函数,实现了土壤穿透阻力在不同水分状况下的转换:同一种土壤平均容重下的转换系数可适用于其他容重条件;在不同土壤类型间,黑土某一容重下的转换系数,可用于相同容重下的白浆土,反之亦然。
