Fractal geometry is a potential new approach to analyze the root architecture, which may offer improved ways to quantify and summarize root system complexity as well as yield ecological and physiological insights into...Fractal geometry is a potential new approach to analyze the root architecture, which may offer improved ways to quantify and summarize root system complexity as well as yield ecological and physiological insights into the functional relevance of specific architectural patterns. Fractal analysis is a sensitive measure of root branching intensity and fractal dimension expresses the ＂space filling＂ properties of a structure. The objective of this study was to find out the fractal characteristics of root systems in a remote area of the Taklimakan desert in China. The entire root system of two naturally occurring species were excavated and exposed with shov- els in 2007. The species were Tamarix taklamakanensis and Calligonum roborovskii. A one-factorial ANOVA with species as factor showed statistically a highly significant difference in fractal dimensions, indicating differences in their pattern of root branching. There was no relationship between root diameter and two parameters of fractal root models a and q, representing general characteris- tics of root systems, for either species （a： the ratio of the sum of root cross-sectional areas after a branching to the cross-sectional area before root division; q： the distribution of the cross-sectional areas after branching）. We have found significant linear relation- ships between the diameter after branching and root length and biomass respectively, because of the self-similarity of root branching. Branching rules are the same for roots of all sizes and lengths. Root biomass for the root systems of entire trees can be estimated by measuring the diameter of each root at the base of the trunk or the diameter after branching. We have shown that the diameter of each root at the base of the trunk and the diameter after branching are effective indices that can be measured easily in order to estimate the root lengths, biomass and other parameters of root architecture.展开更多
基于西南地区油菜收获后大豆-玉米带状间作种植存在的弱光环境、品种和密度筛选等问题,选择2个不同熟期的品种南夏豆25号(ND25,中晚熟,多分枝)、齐黄34(QH34,早熟,少分枝),分析播期(2021年,S1:5月17日,S2:5月27日,S3:6月6日;2022年,S1:5...基于西南地区油菜收获后大豆-玉米带状间作种植存在的弱光环境、品种和密度筛选等问题,选择2个不同熟期的品种南夏豆25号(ND25,中晚熟,多分枝)、齐黄34(QH34,早熟,少分枝),分析播期(2021年,S1:5月17日,S2:5月27日,S3:6月6日;2022年,S1:5月10日,S2:5月25日,S3:6月9日)及密度(D1:81,000株hm^(–2),D2:101,000株hm^(–2),D3:140,000株hm^(–2),D4:171,000株hm^(–2))对带状间作大豆茎叶生长及产量形成的影响。结果表明:同一密度,随着播期的推迟,2个品种始粒期的叶面积指数逐渐减小,冠层内部透光率逐渐增加,ND25对荚的分配比率逐渐增加,倒伏率逐渐降低,QH34对荚的分配比率逐渐减少,倒伏率逐渐增加;同一播期,随着密度的增加,2个品种始粒期的叶面积指数逐渐增加,透光率逐渐减小,对荚的干物质分配比率逐渐减少,倒伏率逐渐上升。光环境及干物质分配差异对不同品种的产量影响不同,ND25同一密度不同播期间,S3>S2>S1,同一播期不同密度间,D1>D2>D3>D4,ND25品种S3播期D1密度产量最优,为1752.89 kg hm^(–2);QH34同一密度不同播期间,S1>S2>S3,同一播期不同密度间,D3>D2>D1>D4,QH34品种S1播期D3密度产量最优,为1538.64 kg hm^(–2)。因此,中晚熟品种应适当晚播,早熟品种应适当早播,多分枝品种适度稀植,少分枝品种适度密植,各品种通过播期、密度协同可提高大豆产量。展开更多
Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling,precision agriculture,and natural resources management.The spatio-temporal variations of soil nitrogen und...Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling,precision agriculture,and natural resources management.The spatio-temporal variations of soil nitrogen under different land uses in a small watershed(12.10 km 2) in the hilly area of purple soil at the upper reaches of the Yangtze River in southwestern China were investigated by using conventional statistics,geostatistics,and a geographical information system in order to provide information for land management and control of environmental issues.A total of 552 soil samples(0 to 15 cm) from 276 sites within the watershed were collected in April and August of 2011,and analyzed for soil total nitrogen(STN) and nitrate nitrogen(NO3-N).We compared spatial variations of STN and NO3-N under different land uses as well as the temporal variations in April(dry season) and August(rainy season).Results showed that STN contents were deeply affected by land-use types;median STN values ranged from 0.94 to 1.27 g.kg-1,and STN contents decreased in the following order:paddy field > forestland > sloping cropland.No significant difference was found for STN contents between April and August under the same land use.However,NO3N contents were 23.26,10.58,and 26.19 mg.kg-1 in April,and 1.34,8.51,and 3.00 mg.kg-1 in August for the paddy field,sloping cropland and forestland,respectively.Nugget ratios for STN indicated moderate spatial dependence in the paddy field and sloping cropland,and a strong spatial dependence in forestland.The processes of nitrogen movement,transformation,absorption of plant were deeply influenced by land use types;as a result,great changes of soil nitrogen levels at spatial and temporal scales were demonstrated in the studied watershed.展开更多
An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction （MAT-MI） is pro- posed, based on the analyses of one-dimensional tissue vibration, three-dimensional acoustic dipole radiatio...An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction （MAT-MI） is pro- posed, based on the analyses of one-dimensional tissue vibration, three-dimensional acoustic dipole radiation and acoustic waveform detection with a planar piston transducer. The collected waveforms provide information about the conductiv- ity boundaries in various vibration intensities and phases due to the acoustic dipole radiation pattern. Combined with the simplified back projection algorithm, the conductivity configuration of the measured layer in terms of shape and size can be reconstructed with obvious border stripes. The numerical simulation is performed for a two-layer cylindrical phantom model and it is also verified by the experimental results of MAT-MI for a tissue-like sample phantom. The proposed model suggests a potential application of conductivity differentiation and provides a universal basis for the further study of conductivity reconstruction for MAT-MI.展开更多
文摘Fractal geometry is a potential new approach to analyze the root architecture, which may offer improved ways to quantify and summarize root system complexity as well as yield ecological and physiological insights into the functional relevance of specific architectural patterns. Fractal analysis is a sensitive measure of root branching intensity and fractal dimension expresses the ＂space filling＂ properties of a structure. The objective of this study was to find out the fractal characteristics of root systems in a remote area of the Taklimakan desert in China. The entire root system of two naturally occurring species were excavated and exposed with shov- els in 2007. The species were Tamarix taklamakanensis and Calligonum roborovskii. A one-factorial ANOVA with species as factor showed statistically a highly significant difference in fractal dimensions, indicating differences in their pattern of root branching. There was no relationship between root diameter and two parameters of fractal root models a and q, representing general characteris- tics of root systems, for either species （a： the ratio of the sum of root cross-sectional areas after a branching to the cross-sectional area before root division; q： the distribution of the cross-sectional areas after branching）. We have found significant linear relation- ships between the diameter after branching and root length and biomass respectively, because of the self-similarity of root branching. Branching rules are the same for roots of all sizes and lengths. Root biomass for the root systems of entire trees can be estimated by measuring the diameter of each root at the base of the trunk or the diameter after branching. We have shown that the diameter of each root at the base of the trunk and the diameter after branching are effective indices that can be measured easily in order to estimate the root lengths, biomass and other parameters of root architecture.
文摘基于西南地区油菜收获后大豆-玉米带状间作种植存在的弱光环境、品种和密度筛选等问题,选择2个不同熟期的品种南夏豆25号(ND25,中晚熟,多分枝)、齐黄34(QH34,早熟,少分枝),分析播期(2021年,S1:5月17日,S2:5月27日,S3:6月6日;2022年,S1:5月10日,S2:5月25日,S3:6月9日)及密度(D1:81,000株hm^(–2),D2:101,000株hm^(–2),D3:140,000株hm^(–2),D4:171,000株hm^(–2))对带状间作大豆茎叶生长及产量形成的影响。结果表明:同一密度,随着播期的推迟,2个品种始粒期的叶面积指数逐渐减小,冠层内部透光率逐渐增加,ND25对荚的分配比率逐渐增加,倒伏率逐渐降低,QH34对荚的分配比率逐渐减少,倒伏率逐渐增加;同一播期,随着密度的增加,2个品种始粒期的叶面积指数逐渐增加,透光率逐渐减小,对荚的干物质分配比率逐渐减少,倒伏率逐渐上升。光环境及干物质分配差异对不同品种的产量影响不同,ND25同一密度不同播期间,S3>S2>S1,同一播期不同密度间,D1>D2>D3>D4,ND25品种S3播期D1密度产量最优,为1752.89 kg hm^(–2);QH34同一密度不同播期间,S1>S2>S3,同一播期不同密度间,D3>D2>D1>D4,QH34品种S1播期D3密度产量最优,为1538.64 kg hm^(–2)。因此,中晚熟品种应适当晚播,早熟品种应适当早播,多分枝品种适度稀植,少分枝品种适度密植,各品种通过播期、密度协同可提高大豆产量。
基金this project was provided by the Natural Science Foundation of China (Grant No.41271321)the National Key Basic Research Program of China (Grant no. 2012CB417101)
文摘Quantification of soil spatial and temporal variability at watershed scale is important in ecological modeling,precision agriculture,and natural resources management.The spatio-temporal variations of soil nitrogen under different land uses in a small watershed(12.10 km 2) in the hilly area of purple soil at the upper reaches of the Yangtze River in southwestern China were investigated by using conventional statistics,geostatistics,and a geographical information system in order to provide information for land management and control of environmental issues.A total of 552 soil samples(0 to 15 cm) from 276 sites within the watershed were collected in April and August of 2011,and analyzed for soil total nitrogen(STN) and nitrate nitrogen(NO3-N).We compared spatial variations of STN and NO3-N under different land uses as well as the temporal variations in April(dry season) and August(rainy season).Results showed that STN contents were deeply affected by land-use types;median STN values ranged from 0.94 to 1.27 g.kg-1,and STN contents decreased in the following order:paddy field > forestland > sloping cropland.No significant difference was found for STN contents between April and August under the same land use.However,NO3N contents were 23.26,10.58,and 26.19 mg.kg-1 in April,and 1.34,8.51,and 3.00 mg.kg-1 in August for the paddy field,sloping cropland and forestland,respectively.Nugget ratios for STN indicated moderate spatial dependence in the paddy field and sloping cropland,and a strong spatial dependence in forestland.The processes of nitrogen movement,transformation,absorption of plant were deeply influenced by land use types;as a result,great changes of soil nitrogen levels at spatial and temporal scales were demonstrated in the studied watershed.
基金Project supported by the National Basic Research Program of China （Grant No. 2011CB707900）, the National Natural Science Foundation of China （Grant No. 10974098）, the Natural Science Foundation of Jiangsu Province, China （Grant No. BK2009407）, and the Specialized Research Fund for Doctoral Program of High Education of China （Grant No. 20093207120003）.
文摘An acoustic dipole radiation model for magnetoacoustic tomography with magnetic induction （MAT-MI） is pro- posed, based on the analyses of one-dimensional tissue vibration, three-dimensional acoustic dipole radiation and acoustic waveform detection with a planar piston transducer. The collected waveforms provide information about the conductiv- ity boundaries in various vibration intensities and phases due to the acoustic dipole radiation pattern. Combined with the simplified back projection algorithm, the conductivity configuration of the measured layer in terms of shape and size can be reconstructed with obvious border stripes. The numerical simulation is performed for a two-layer cylindrical phantom model and it is also verified by the experimental results of MAT-MI for a tissue-like sample phantom. The proposed model suggests a potential application of conductivity differentiation and provides a universal basis for the further study of conductivity reconstruction for MAT-MI.
