Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettab...Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.展开更多
The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements (n=52)performed with an ASD FieldSpec-Ⅱspectroradiometer.For parameter prediction,empirical models base...The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements (n=52)performed with an ASD FieldSpec-Ⅱspectroradiometer.For parameter prediction,empirical models based on partial least squares(PLS)regression were defined from the measured reflectance spectra(0.4 to 2.4μm).Here,reliable estimates were obtained for nitrogen content,but prediction accuracy was only moderate for organic carbon.For nitrogen, the real spatial pattern of within-field variability was reproduced with high accuracy.The results indicate the potential of this method as a quick screening tool for the spatial assessment of nitrogen and organic carbon,and therefore an appropriate alternative to time-and cost-intensive chemical analysis in the laboratory.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 spati...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 evaluate 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 variation of soil clay content with soil depth and had a significant linear relationship with soil porosity (r2 = 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 (r2 = 0.69, P < 0.01). These results suggested that soil strength induced by soil erosion and soil management varied 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
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 wit...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 reflectometry(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:1) 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
A well developed macropore network is advantageous in terms of transport processes regarding gas and water,as well as nutrient acquisition and root growth of crops.X-ray computed tomography provides a non-destructive ...A well developed macropore network is advantageous in terms of transport processes regarding gas and water,as well as nutrient acquisition and root growth of crops.X-ray computed tomography provides a non-destructive method to visualize and quantify three-dimensional pore networks.Geometrical and morphological parameters of the complex pore system such as connectivity,tortuosity,porosity and pore surface area would be very useful for modeling and simulation of transport and exchange processes by providing quantitative data on relevant soil structural features and their modification by soil management.The scope of this study was to analyze and quantify the development of soil structure in the subsoil depending on three different precrop species(alfalfa A,chicory C and fescue F),at three depths(45,60 and 75 cm)and cultivation periods(1,2 and 3 years).Furthermore,morphological(air-filled porosityθa,pore surface area)and geometrical(pore diameter,connectivity,continuity,tortuosityτ)parameters were gathered with X-ray CT and image analysis.From an experimental field trial(Germany)with a Haplic Luvisol as soil type samples were taken and investigated.Air-capacity(θa)was measured in the laboratory for the same cylinders and compared to the results derived by image analysis.Air-capacity was highest for alfalfa(3 years,75 cm).Tortuosity(τ)ranged between 1.3 and 4.38,while alfalfa(3 years)showed the highest value,which indicated structural development due to crack formation by enhanced root water uptake.Thus,an increase in accessible surface may improve water and nutrient supply for plants,whereas the highτvalues may assume that oxygen supply is limited.It was found that the interaction of gas-diffusivity and the calculated parameters should be further investigated in terms of limitations to plant growth.展开更多
Soil is one of the most critical life-supporting components of the biosphere. Soil provides many ecosystem services,such as a habitat for biodiversity, water and nutrients, food, feed, fiber and energy, but also serve...Soil is one of the most critical life-supporting components of the biosphere. Soil provides many ecosystem services,such as a habitat for biodiversity, water and nutrients, food, feed, fiber and energy, but also serves as archaeologicalrepositories. In addition to natural changes in pedological properties and functions over the course of time (soilgenesis), their properties also undergo intense and irreversible changes due to a non-site adjusted landmanagement and improper application of machinery, sealing and techniques as well as chemical impacts includingacidity from acid rain, heavy metals pollution and salinity.展开更多
研究了硫营养对绿茶产量和品质的影响及其可能的机理。试验设2个硫处理(0,50 kg S.ha-1.a-1),每个处理重复4次,完全随机区组设计。结果表明:施硫能够提高产量、增加氨基酸和抗坏血酸(AsA和DAsA)含量,降低茶多酚和酚氨比(TP/AA)。施硫对...研究了硫营养对绿茶产量和品质的影响及其可能的机理。试验设2个硫处理(0,50 kg S.ha-1.a-1),每个处理重复4次,完全随机区组设计。结果表明:施硫能够提高产量、增加氨基酸和抗坏血酸(AsA和DAsA)含量,降低茶多酚和酚氨比(TP/AA)。施硫对茶叶品质的改善与降低多酚氧化酶(PPO)的活性、提高硝酸还原酶(NR)和苯丙氨酸解氨酶(PAL)活性有关。展开更多
To study the effects of local nitrogen supply on water and nutrient absorption, French bean （Phaseolus vulgaris L.） plants were grown in a split root system. Five treatments supplied with different nitrogen forms we...To study the effects of local nitrogen supply on water and nutrient absorption, French bean （Phaseolus vulgaris L.） plants were grown in a split root system. Five treatments supplied with different nitrogen forms were compared： homogeneous nitrate （NN） and homogenous ammonium （AA） supply, spatially separated supply of nitrate and ammonium （NA）, half of the root system supplied with N-free nutrient solution, the other half with either nitrate （NO） or ammonium （AO）. The results showed that 10 d after onset of treatments, root dry matter （DM） in the nitratesupplied vessels treated with NA was more than two times higher than that in the ammonium-supplied vessels. Water uptake from the nitrate-supplied vessels treated with NA was 281% higher than under ammonium supply. In treatments NO and AO, the local supply of N resulted in clearly higher root DM, and water uptake from the nitratesupplied vessels was 82% higher than in the -N vessels. However, in AO plants, water uptake from the -N nutrient solution was 129% higher than from the ammonium-supplied vessels. This indicates a compensatory effect, which resulted in almost identical rates of total water uptake of treatments AA and AO, which had comparable shoot DM and leaf area. Ammonium supply reduced potassium and magnesium absorption. Water uptake was positively correlated with N, Mg and K uptake.展开更多
基金Project supported by the Max-Planck Foundation, Germany
文摘Depth distribution of soil wettability and its correlations with vegetation type, soil texture, and pH were investigated under various land use (cropland, grassland, and forestland) and soil management systems. Wettability was evaluated by contact angle with the Wilhelmy plate method. Water repellency was likely to be present under permanently vegetated land, but less common on tilled agricultural land. It was mostly prevalent in the topsoil, especially in coarse-textured soils, and decreased in the subsoil. However, the depth dependency of wettability could not be derived from the investigated wide range of soils. The correlation and multiple regression analysis revealed that the wettability in repellent soils was affected more by soil organic carbon (SOC) than by soil texture and pH, whereas in wettable soils, soil texture and pH were more effective than SOC. Furthermore, the quality of SOC seemed to be more important in determining wettability than its quantity, as proofed by stronger hydrophobicity under coniferous than under deciduous forestland. Soil management had a minor effect on wettability if conventional and conservation tillage or different grazing intensities were considered.
文摘The contents of nitrogen and organic carbon in an agricultural soil were analyzed using reflectance measurements (n=52)performed with an ASD FieldSpec-Ⅱspectroradiometer.For parameter prediction,empirical models based on partial least squares(PLS)regression were defined from the measured reflectance spectra(0.4 to 2.4μm).Here,reliable estimates were obtained for nitrogen content,but prediction accuracy was only moderate for organic carbon.For nitrogen, the real spatial pattern of within-field variability was reproduced with high accuracy.The results indicate the potential of this method as a quick screening tool for the spatial assessment of nitrogen and organic carbon,and therefore an appropriate alternative to time-and cost-intensive chemical analysis in the laboratory.
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 evaluate 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 variation of soil clay content with soil depth and had a significant linear relationship with soil porosity (r2 = 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 (r2 = 0.69, P < 0.01). These results suggested that soil strength induced by soil erosion and soil management varied 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 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 reflectometry(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:1) 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 German Research Foundation(Deutsche Forschungsgemeinschaft DFG)within the framework of the research unit DFG‐FOR 1320.
文摘A well developed macropore network is advantageous in terms of transport processes regarding gas and water,as well as nutrient acquisition and root growth of crops.X-ray computed tomography provides a non-destructive method to visualize and quantify three-dimensional pore networks.Geometrical and morphological parameters of the complex pore system such as connectivity,tortuosity,porosity and pore surface area would be very useful for modeling and simulation of transport and exchange processes by providing quantitative data on relevant soil structural features and their modification by soil management.The scope of this study was to analyze and quantify the development of soil structure in the subsoil depending on three different precrop species(alfalfa A,chicory C and fescue F),at three depths(45,60 and 75 cm)and cultivation periods(1,2 and 3 years).Furthermore,morphological(air-filled porosityθa,pore surface area)and geometrical(pore diameter,connectivity,continuity,tortuosityτ)parameters were gathered with X-ray CT and image analysis.From an experimental field trial(Germany)with a Haplic Luvisol as soil type samples were taken and investigated.Air-capacity(θa)was measured in the laboratory for the same cylinders and compared to the results derived by image analysis.Air-capacity was highest for alfalfa(3 years,75 cm).Tortuosity(τ)ranged between 1.3 and 4.38,while alfalfa(3 years)showed the highest value,which indicated structural development due to crack formation by enhanced root water uptake.Thus,an increase in accessible surface may improve water and nutrient supply for plants,whereas the highτvalues may assume that oxygen supply is limited.It was found that the interaction of gas-diffusivity and the calculated parameters should be further investigated in terms of limitations to plant growth.
文摘Soil is one of the most critical life-supporting components of the biosphere. Soil provides many ecosystem services,such as a habitat for biodiversity, water and nutrients, food, feed, fiber and energy, but also serves as archaeologicalrepositories. In addition to natural changes in pedological properties and functions over the course of time (soilgenesis), their properties also undergo intense and irreversible changes due to a non-site adjusted landmanagement and improper application of machinery, sealing and techniques as well as chemical impacts includingacidity from acid rain, heavy metals pollution and salinity.
文摘研究了硫营养对绿茶产量和品质的影响及其可能的机理。试验设2个硫处理(0,50 kg S.ha-1.a-1),每个处理重复4次,完全随机区组设计。结果表明:施硫能够提高产量、增加氨基酸和抗坏血酸(AsA和DAsA)含量,降低茶多酚和酚氨比(TP/AA)。施硫对茶叶品质的改善与降低多酚氧化酶(PPO)的活性、提高硝酸还原酶(NR)和苯丙氨酸解氨酶(PAL)活性有关。
基金Supported by the Deutsche Forschungsgemeinschaft （Sa359/9） and the National Natural Science Foundation of China （30400279）.Acknowledgements We thank Barbel Biegler and Anne ThieBen （Institute of Plant Nutrition and Soil Science, Kiel University, Germany） for skilled technical help.
文摘To study the effects of local nitrogen supply on water and nutrient absorption, French bean （Phaseolus vulgaris L.） plants were grown in a split root system. Five treatments supplied with different nitrogen forms were compared： homogeneous nitrate （NN） and homogenous ammonium （AA） supply, spatially separated supply of nitrate and ammonium （NA）, half of the root system supplied with N-free nutrient solution, the other half with either nitrate （NO） or ammonium （AO）. The results showed that 10 d after onset of treatments, root dry matter （DM） in the nitratesupplied vessels treated with NA was more than two times higher than that in the ammonium-supplied vessels. Water uptake from the nitrate-supplied vessels treated with NA was 281% higher than under ammonium supply. In treatments NO and AO, the local supply of N resulted in clearly higher root DM, and water uptake from the nitratesupplied vessels was 82% higher than in the -N vessels. However, in AO plants, water uptake from the -N nutrient solution was 129% higher than from the ammonium-supplied vessels. This indicates a compensatory effect, which resulted in almost identical rates of total water uptake of treatments AA and AO, which had comparable shoot DM and leaf area. Ammonium supply reduced potassium and magnesium absorption. Water uptake was positively correlated with N, Mg and K uptake.
