An acid sulfate soil sample was successively extracted with deionized water, 1 mol L-1 KCl and 0.000 5 mol L-l Ca(OH)2 solutions. The results showed that only very small amounts of acidity were extracted by deionized ...An acid sulfate soil sample was successively extracted with deionized water, 1 mol L-1 KCl and 0.000 5 mol L-l Ca(OH)2 solutions. The results showed that only very small amounts of acidity were extracted by deionized water, possibly through slow jarosite hydrolysis. Acid release through jarosite hydrolysis was greatly enhanced by Ca(OH)2 extraction at the expense of the added OH- being neutralized by the acid released. Successive extraction of the sample with KCl removed the largest amounts of acidity from the sample. However, it is likely that the major form of acidity released by KCl extraction was exchangeable acidity. The results also show the occurrence of low or non charged Al and Fe species in water and Ca(OH)2 extracts after first a few extractions. It appears that such a phenomenon was related to a decreasing EC value with increasing number of extractions.展开更多
AS geographic literacy training is an education, national geographical education is essential content for Chinese citizens＇ literacy one of the indispensable key aspects of that training. Because of China＇s vast lan...AS geographic literacy training is an education, national geographical education is essential content for Chinese citizens＇ literacy one of the indispensable key aspects of that training. Because of China＇s vast land area and the significance of the regional differences, it is difficult for students to receive a solid education regarding China＇s geography. In 1902, the government established the geography curriculum and began to incorporate the concept of geographical regionalization to facilitate the teaching of China＇s geography by publishing the first syllabi, which was modified later and put into use in 1904. Since 1904, numerous geog raphy textbooks have attempted to find an appropriate way to present China＇s geographical regionalization, as it is important for secondary students to have a clear understanding and appreciation for the different regional characteristics. Accordingly, the geographical region alization content is divided into four main phases： 1902 to 1927; 1928 to 1948; 1949 to 1986; and 1986 to the present. During these phases, the content related to China＇s geographical regionalization in secondary middle school geography textbooks has been gradually simplified and has adopted a more scientific foundation, thus leading to the present time where there are now four geographical regional areas. From this historical study, we find that while China＇s geographical regionalization has gradually matured, there are still some problems. For example, dividing the study into four regions to describe the panorama of China is too simplified, and the learning therefore becomes too scattered and haphazard, particularly qiven the new curriculum reform.展开更多
The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO...The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO4 solutions; 2) experimental acid sulfate conditions by addition of the same sequence of H2SO4solutions into two non-acid sulfate soil samples with known amounts of acid oxalate extractable Al; and3) actual acid sulfate soil conditions. The experiment using gibbsite as an Al-bearing mineral showed thatincrease in the concentration of H2SO4 solution increased the soluble Al concentration, accompanied bya decrease in the solution pH. Increasing amount of gibbsite added to the H2SO4 solutions also increasedsoluble Al concentration, but resulted in an increase in solution pH. Within the H2SO4 concentration rangeof 0.0005～0.5 mol L-1 and the Al(OH)3 range of 0.01～0.5g (in 25 mL of H2SO4 solutions), the input ofH2SO4 had the major control on soluble Al concentration and pH. The availability of Al(OH)3, however, wasresponsible for the spread of the various sample points, with a tendency that the samples containing moregibbsite had a higher soluble Al concentration than those containing less gibbsite at equivalent pH levels.The experimental results from treatment of soil samples with H2SO4 solutions and the analytical results ofacid sulfate soils also showed the similar trend.展开更多
Recent studies have demonstrated the application of vegetation indices from canopy reflectedspectrum for inversion of chlorophyll concentration. Some indices are both response tovariations of vegetation and environmen...Recent studies have demonstrated the application of vegetation indices from canopy reflectedspectrum for inversion of chlorophyll concentration. Some indices are both response tovariations of vegetation and environmental factors. Canopy chlorophyll concentration, anindicator of photosynthesis activity, is related to nitrogen concentration in green vegetationand serves as an indicator of the crop response to soil nitrogen fertilizer application. Thecombination of normalized difference vegetation index (NDVI) and photochemical reflectanceindex (PRI) can reduce the effect of leaf area index (LAI) and soil background. The canopychlorophyll inversion index (CCII) was proved to be sensitive to chlorophyll concentration andvery resistant to the other variations. This paper introduced the ratio of TCARI/OSAVI to makeaccurate predictions of winter wheat chlorophyll concentration under different cultivars. Itindicated that canopy chlorophyll concentration could be evaluated by some combined vegetationindices.展开更多
Field experiments were conducted to examine the influence factors of cultivar, nitrogen application and irrigation on grain protein content, gluten content and grain hardness in three winter wheat cultivars under fo...Field experiments were conducted to examine the influence factors of cultivar, nitrogen application and irrigation on grain protein content, gluten content and grain hardness in three winter wheat cultivars under four levels of nitrogen and irrigation treatments. Firstly, the influence of cultivars and environment factors on grain quality were studied, the effective factors were cultivars, irrigation, fertilization, etc. Secondly, total nitrogen content around winter wheat anthesis stage was proved to be significantly correlative with grain protein content, and spectral vegetation index significantly correlated to total nitrogen content around anthesis stage were the potential indicators for grain protein content. Accumulation of total nitrogen content and its transfer to grain is the physical link to produce the final grain protein, and total nitrogen content at anthesis stage was proved to be an indicator of final grain protein content. The selected normalized photochemical reflectance index (NPRI) was proved to be able to predict grain protein content on the close correlation between the ratio of total carotenoid to chlorophyll a and total nitrogen content. The method contributes towards developing optimal procedures for predicting wheat grain quality through analysis of their canopy reflected spectrum at anthesis stage. Regression equations were established to forecast grain protein and dry gluten content by total nitrogen content at anthesis stage, so it is feasible for forecasting grain quality by establishing correlation equations between biochemical constitutes and canopy reflected spectrum.展开更多
Soil erosion caused by water is an increasing global problem. In order to relieve this problem, several erosion models have been developed to measure the rate of erosion for soil conservation planning. This study take...Soil erosion caused by water is an increasing global problem. In order to relieve this problem, several erosion models have been developed to measure the rate of erosion for soil conservation planning. This study takes Lee County, South Carolina, USA as an example to map soil erosion within ArcGIS environment by using the RUSLE with erosion indexes retrieved from DEM. This study proves that the integration of soil erosion models with GIS is a very simple but efficient tool for soil conservation.展开更多
文摘An acid sulfate soil sample was successively extracted with deionized water, 1 mol L-1 KCl and 0.000 5 mol L-l Ca(OH)2 solutions. The results showed that only very small amounts of acidity were extracted by deionized water, possibly through slow jarosite hydrolysis. Acid release through jarosite hydrolysis was greatly enhanced by Ca(OH)2 extraction at the expense of the added OH- being neutralized by the acid released. Successive extraction of the sample with KCl removed the largest amounts of acidity from the sample. However, it is likely that the major form of acidity released by KCl extraction was exchangeable acidity. The results also show the occurrence of low or non charged Al and Fe species in water and Ca(OH)2 extracts after first a few extractions. It appears that such a phenomenon was related to a decreasing EC value with increasing number of extractions.
基金National Social Science Foundation of China, No.AHA120008
文摘AS geographic literacy training is an education, national geographical education is essential content for Chinese citizens＇ literacy one of the indispensable key aspects of that training. Because of China＇s vast land area and the significance of the regional differences, it is difficult for students to receive a solid education regarding China＇s geography. In 1902, the government established the geography curriculum and began to incorporate the concept of geographical regionalization to facilitate the teaching of China＇s geography by publishing the first syllabi, which was modified later and put into use in 1904. Since 1904, numerous geog raphy textbooks have attempted to find an appropriate way to present China＇s geographical regionalization, as it is important for secondary students to have a clear understanding and appreciation for the different regional characteristics. Accordingly, the geographical region alization content is divided into four main phases： 1902 to 1927; 1928 to 1948; 1949 to 1986; and 1986 to the present. During these phases, the content related to China＇s geographical regionalization in secondary middle school geography textbooks has been gradually simplified and has adopted a more scientific foundation, thus leading to the present time where there are now four geographical regional areas. From this historical study, we find that while China＇s geographical regionalization has gradually matured, there are still some problems. For example, dividing the study into four regions to describe the panorama of China is too simplified, and the learning therefore becomes too scattered and haphazard, particularly qiven the new curriculum reform.
文摘The controls of soluble Al concentration were examined in three situations of acid sulfate conditions: 1)experimental acid sulfate conditions by addition of varying amounts of Al(OH)3 (gibbsite) into a sequenceof H2SO4 solutions; 2) experimental acid sulfate conditions by addition of the same sequence of H2SO4solutions into two non-acid sulfate soil samples with known amounts of acid oxalate extractable Al; and3) actual acid sulfate soil conditions. The experiment using gibbsite as an Al-bearing mineral showed thatincrease in the concentration of H2SO4 solution increased the soluble Al concentration, accompanied bya decrease in the solution pH. Increasing amount of gibbsite added to the H2SO4 solutions also increasedsoluble Al concentration, but resulted in an increase in solution pH. Within the H2SO4 concentration rangeof 0.0005～0.5 mol L-1 and the Al(OH)3 range of 0.01～0.5g (in 25 mL of H2SO4 solutions), the input ofH2SO4 had the major control on soluble Al concentration and pH. The availability of Al(OH)3, however, wasresponsible for the spread of the various sample points, with a tendency that the samples containing moregibbsite had a higher soluble Al concentration than those containing less gibbsite at equivalent pH levels.The experimental results from treatment of soil samples with H2SO4 solutions and the analytical results ofacid sulfate soils also showed the similar trend.
基金support provided for this research by the Special Funds for Major State Basic Research Project(G20000779)the 863 National Project(2002AA243011,2003AA209010 and H020821020130)
文摘Recent studies have demonstrated the application of vegetation indices from canopy reflectedspectrum for inversion of chlorophyll concentration. Some indices are both response tovariations of vegetation and environmental factors. Canopy chlorophyll concentration, anindicator of photosynthesis activity, is related to nitrogen concentration in green vegetationand serves as an indicator of the crop response to soil nitrogen fertilizer application. Thecombination of normalized difference vegetation index (NDVI) and photochemical reflectanceindex (PRI) can reduce the effect of leaf area index (LAI) and soil background. The canopychlorophyll inversion index (CCII) was proved to be sensitive to chlorophyll concentration andvery resistant to the other variations. This paper introduced the ratio of TCARI/OSAVI to makeaccurate predictions of winter wheat chlorophyll concentration under different cultivars. Itindicated that canopy chlorophyll concentration could be evaluated by some combined vegetationindices.
基金financially supported by the Special Funds for Major State Basic Research Project,China(G20000779)the China National High Tech R&D Program(2002AA243011,2003AA209010,H020821020130).
文摘Field experiments were conducted to examine the influence factors of cultivar, nitrogen application and irrigation on grain protein content, gluten content and grain hardness in three winter wheat cultivars under four levels of nitrogen and irrigation treatments. Firstly, the influence of cultivars and environment factors on grain quality were studied, the effective factors were cultivars, irrigation, fertilization, etc. Secondly, total nitrogen content around winter wheat anthesis stage was proved to be significantly correlative with grain protein content, and spectral vegetation index significantly correlated to total nitrogen content around anthesis stage were the potential indicators for grain protein content. Accumulation of total nitrogen content and its transfer to grain is the physical link to produce the final grain protein, and total nitrogen content at anthesis stage was proved to be an indicator of final grain protein content. The selected normalized photochemical reflectance index (NPRI) was proved to be able to predict grain protein content on the close correlation between the ratio of total carotenoid to chlorophyll a and total nitrogen content. The method contributes towards developing optimal procedures for predicting wheat grain quality through analysis of their canopy reflected spectrum at anthesis stage. Regression equations were established to forecast grain protein and dry gluten content by total nitrogen content at anthesis stage, so it is feasible for forecasting grain quality by establishing correlation equations between biochemical constitutes and canopy reflected spectrum.
文摘Soil erosion caused by water is an increasing global problem. In order to relieve this problem, several erosion models have been developed to measure the rate of erosion for soil conservation planning. This study takes Lee County, South Carolina, USA as an example to map soil erosion within ArcGIS environment by using the RUSLE with erosion indexes retrieved from DEM. This study proves that the integration of soil erosion models with GIS is a very simple but efficient tool for soil conservation.
