Soil Conservation Service (SCS) model, developed by U. S. Soil Conservation Service in 1972, has been widely applied in the estimation of runoff from an small watershed. In this paper, based on the remote sensing geo-...Soil Conservation Service (SCS) model, developed by U. S. Soil Conservation Service in 1972, has been widely applied in the estimation of runoff from an small watershed. In this paper, based on the remote sensing geo-information data of land use and soil classification all obtained from Landsat images in 1996 and 1997 and con-ventional data of hydrology and meteorology, the SCS model was investigated for simulating the surface runoff for single rainstorm in Wangdonggou watershed, a typical small watershed in the Loess Plateau, located in Changwu County of Shaanxi Province of China. Wangdonggou watershed was compartmentalized into 28 sub-units according to natural draining division,and the table of curve number (CN) values fitting for Wangdonggou watershed was also presented. During the flood period from 1996 to 1997, the hydrograph of calculated runoff process using the SCS model and the hydrograph of observed runoff process coincided very well in height as well as shape, and the model was of high precision above 75%. It is indicated that the SCS model is legitimate and can be successfully used to simulate the runoff generation and the runoff process of typical small watershed based on the remote sensing geo-information in the Loess Plateau.展开更多
Through the systematic investigation of nitrogen isotope composition (δ15N) in modern plants in Dongling Mountain in Beijing,the characteristics of δ15N in plants,the differences of δ15N among plants with different...Through the systematic investigation of nitrogen isotope composition (δ15N) in modern plants in Dongling Mountain in Beijing,the characteristics of δ15N in plants,the differences of δ15N among plants with different functional types,and the altitudinal trends of plant δ15N values revealed the environmental effects on δ15N.Our results are:(1) the values of δ15N of plants in Dongling Mountain range between -8.0‰ and 14.0‰,with an average value of -1.03‰;(2) δ15N values are variant among different plant functional types.Generally,the δ15N of shrubs are smaller than that of trees,and larger than that of herbaceous plants.The main reason may be the selective absorption of variant nitrogen resource with different δ15N values in soil;(3) there is a second-order polynomials relationship between the altitudes and the average δ15N values of plants,which shows a negative and positive correlation below and above 1350 m a.s.l.,respectively.This indicates that the precipitation is a main controlling factor of plant 15N fractionation for the former,and the temperature for the latter;(4) three different,i.e.,positive,negative,and no significant,correlations are performed between δ15N of individual species and altitudes.This may be related to different inherited characteristics and the process of nitrogen metabolize;and (5) variant altitudinal trends of plant δ15N are associated with different 15N composition of soil at different altitude,for which the key influencing factors are the changing temperature and precipitation with altitude rather than nitrogen content in leaf.展开更多
为了拓展叶绿素类二氢卟吩的研究和应用,以焦脱镁叶绿酸-a甲酯为起始原料,通过氧化和缩合反应,对其N^(21)-N^(23)轴向两端的取代基团进行化学修饰和结构转换,在四吡咯大环分子的周环上构建了醛、邻位二酮、烯腈和烯酮等活性受电子官能结...为了拓展叶绿素类二氢卟吩的研究和应用,以焦脱镁叶绿酸-a甲酯为起始原料,通过氧化和缩合反应,对其N^(21)-N^(23)轴向两端的取代基团进行化学修饰和结构转换,在四吡咯大环分子的周环上构建了醛、邻位二酮、烯腈和烯酮等活性受电子官能结构,再与不同的富电子体系实施关环,合成了一系列未见报道的含有多种杂环结构的焦脱镁叶绿酸衍生物,其化学结构均经UV-Vis, IR, ~1H NMR, MS及元素分析予以证实.同时,对相应杂环的形成过程、立体化学选择性以及电子光谱变化进行了讨论.展开更多
基金Under the auspices of National Natural Science Foundation of China (No 40101005)
文摘Soil Conservation Service (SCS) model, developed by U. S. Soil Conservation Service in 1972, has been widely applied in the estimation of runoff from an small watershed. In this paper, based on the remote sensing geo-information data of land use and soil classification all obtained from Landsat images in 1996 and 1997 and con-ventional data of hydrology and meteorology, the SCS model was investigated for simulating the surface runoff for single rainstorm in Wangdonggou watershed, a typical small watershed in the Loess Plateau, located in Changwu County of Shaanxi Province of China. Wangdonggou watershed was compartmentalized into 28 sub-units according to natural draining division,and the table of curve number (CN) values fitting for Wangdonggou watershed was also presented. During the flood period from 1996 to 1997, the hydrograph of calculated runoff process using the SCS model and the hydrograph of observed runoff process coincided very well in height as well as shape, and the model was of high precision above 75%. It is indicated that the SCS model is legitimate and can be successfully used to simulate the runoff generation and the runoff process of typical small watershed based on the remote sensing geo-information in the Loess Plateau.
基金supported by National Natural Science Foundation of China (Grant No.40673017)Discipline Construction Founds of Ludong University
文摘Through the systematic investigation of nitrogen isotope composition (δ15N) in modern plants in Dongling Mountain in Beijing,the characteristics of δ15N in plants,the differences of δ15N among plants with different functional types,and the altitudinal trends of plant δ15N values revealed the environmental effects on δ15N.Our results are:(1) the values of δ15N of plants in Dongling Mountain range between -8.0‰ and 14.0‰,with an average value of -1.03‰;(2) δ15N values are variant among different plant functional types.Generally,the δ15N of shrubs are smaller than that of trees,and larger than that of herbaceous plants.The main reason may be the selective absorption of variant nitrogen resource with different δ15N values in soil;(3) there is a second-order polynomials relationship between the altitudes and the average δ15N values of plants,which shows a negative and positive correlation below and above 1350 m a.s.l.,respectively.This indicates that the precipitation is a main controlling factor of plant 15N fractionation for the former,and the temperature for the latter;(4) three different,i.e.,positive,negative,and no significant,correlations are performed between δ15N of individual species and altitudes.This may be related to different inherited characteristics and the process of nitrogen metabolize;and (5) variant altitudinal trends of plant δ15N are associated with different 15N composition of soil at different altitude,for which the key influencing factors are the changing temperature and precipitation with altitude rather than nitrogen content in leaf.
文摘为了拓展叶绿素类二氢卟吩的研究和应用,以焦脱镁叶绿酸-a甲酯为起始原料,通过氧化和缩合反应,对其N^(21)-N^(23)轴向两端的取代基团进行化学修饰和结构转换,在四吡咯大环分子的周环上构建了醛、邻位二酮、烯腈和烯酮等活性受电子官能结构,再与不同的富电子体系实施关环,合成了一系列未见报道的含有多种杂环结构的焦脱镁叶绿酸衍生物,其化学结构均经UV-Vis, IR, ~1H NMR, MS及元素分析予以证实.同时,对相应杂环的形成过程、立体化学选择性以及电子光谱变化进行了讨论.
