The dynamics of rhizosphere microbial communities is important for plant health and productivity, and can be influenced by soil type, plant species or genotype, and plant growth stage. A pot experiment was carried out...The dynamics of rhizosphere microbial communities is important for plant health and productivity, and can be influenced by soil type, plant species or genotype, and plant growth stage. A pot experiment was carried out to examine the dynamics of microbial communities in the rhizosphere of two soybean genotypes grown in a black soil in Northeast China with a long history of soybean cultivation. The two soybean genotypes, Beifeng 11 and Hai 9731, differing in productivity were grown in a mixture of black soil and siliceous sand. The bacterial communities were compared at three zone locations including rhizoplane, rhizosphere, and bulk soil at the third node (V3), early flowering (R1), and early pod (R3) stages using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DCGE) of 16S rDNA. The results of principal component analyses (PCA) showed that the bacterial community structure changed with growth stage. Spatially, the bacterial communities in the rhizoplane and rhizosphere were significantly different from those in the bulk soil. Nevertheless, the bacterial communities in the rhizoplane were distinct from those in the rhizosphere at the V3 stage, while no obvious differences were found at the R1 and R3 stages. For the two genotypes, the bacterial community structure was similar at the V3 stage, but differed at the R1 and R3 stages. In other words, some bacterial populations became dominant and some others recessive at the two later stages, which contributed to the variation of the bacterial community between the two genotypes. These results suggest that soybean plants can modify the rhizosphere bacterial communities in the black soil, and there existed genotype-specific bacterial populations in the rhizospbere, which may be related to soybean productivity.展开更多
Shift-share analysis has been confirmed a useful approach in the study of regional economics and many kinds of extended shift-share models have been advanced and put into practice in economic studies, but few have hit...Shift-share analysis has been confirmed a useful approach in the study of regional economics and many kinds of extended shift-share models have been advanced and put into practice in economic studies, but few have hitherto been introduced and applied to the tourism research in China. Moreover understanding the spatially competitive relationship is of paramount importance for marketers, developers, and planners involved in tourism strategy development. Based on international tourism receipts from 1995 to 2004, this study aims at probing into the spatial competitiveness of interna- tional tourism in Jiangsu Province in comparison with its neighbors by applying a spatially extended shift-share model and a modified dynamic shift-share model. The empirical results illustrate that exceptional years may exist in the ap- plication of dynamic shift-share models. To solve this issue, modifications to dynamic shift-share model are put forward. The analytical results are not only presented but also explained by the comparison of background conditions of tourism development between Jiangsu and its key competitors. The conclusions can be drawn that the growth of international tourism receipts in Jiangsu mainly attributes to the national component and the competitive component and Zhejiang is the most important rival to Jiangsu during the period of 1995-2004. In order to upgrade the tourism competitiveness, it is indispensable for Jiangsu to take proper positioning, promoting and marketing strategies and to cooperate and integrate with its main rivals.展开更多
The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the sprin...The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.展开更多
The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handli...The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handling a large amount of waste. Boiling two-phase flow could become powerful means for this system because a boiling and condensation system is one of the most efficient modes of heat transfer due to phase change (liquid-vapor). However, gravity effects on boiling two-phase flow phenomena and the corresponding heat transfer characteristics are not clear. Therefore, we prepare the experiments of boiling two-phase flow utilizing a long-term microgravity environment onboard a Japanese Experimental Module "KIBO" in the International Space Station (ISS) as one of the JAXA official projects. In this paper, recent progress of the preparation for the project is reported.展开更多
Abstract Chinese air pollution has increased in this century along with the rapid socioeconomic development and resulting anthropogenic emissions. While recent emission control measures have shown encouraging re sults...Abstract Chinese air pollution has increased in this century along with the rapid socioeconomic development and resulting anthropogenic emissions. While recent emission control measures have shown encouraging re sults and have reduced the levels of sulfur dioxide and primary aerosols, the concentrations of other air pollutants continue to grow, particularly secondary pollutants in cluding ozone and secondary aerosols. Meanwhile, a va riety of intentional and unintentional socioeconomic events have temporarily changed the pace, and even the signs, of growth of air pollution. These events include the short-term emission restrictions imposed during the Sino-African Summit, the Beijing Olympics and Para lympics, the Shanghai World Exposition (Shanghai Expo), the Guangzhou Asian Olympics, and the Shenzhen Uni versiade, as well as the unintentional emission reductions associated with the recent economic recession and the annual Chinese New Year. This paper presents a brief overview of trends and temporary perturbations of Chi nese air pollution since 2000, summarizing studies on anthropogenic emission inventories, atmospheric meas urements, and inverse modeling. It concludes with rec ommendations for future research.展开更多
Based on the data from gauging stations, the changes in water discharge and sediment load of the Huanghe (Yellow) River were analyzed by using the empirical mode decomposition (EMD) method. The results show that t...Based on the data from gauging stations, the changes in water discharge and sediment load of the Huanghe (Yellow) River were analyzed by using the empirical mode decomposition (EMD) method. The results show that the periodic oscillation of water discharge and sediment load of the Huanghe River occurs at the interannual, decadal, and multi-decadal scales, caused by the periodic oscillations of precipitation, and E1 Nifio/Southern Oscillation (ENSO) af- fects water discharge by influencing precipitation distribution and contributes to periodic varations in precipitation and water discharge at interannual timescale. The water discharge and sediment load of the Huanghe River have decreased since the 1960s under the influence of precipitation and huamn activities, and human activities attribute more than precipitation to the reduction in the water discharge and sediment load, furthermore, water abstraction and water-soil conservation practices are the main causes of the decrease in water discharge and sediment load, respectively. The reduction in sediment load has directly impacted on the lower reaches of the Huanghe River and the river delta, causing considerable erosion of the river channel in the lower reaches since the 1970s along with River Delta changing siltation into erosion around 2000.展开更多
Nutrition plays an essential role in normal linear growth in children. Knowledge of the eating styles and dietary consumption of healthy short children from developed countries is scarce. The aim of this study was to ...Nutrition plays an essential role in normal linear growth in children. Knowledge of the eating styles and dietary consumption of healthy short children from developed countries is scarce. The aim of this study was to investigate the dietary patterns in idiopathic short stature (ISS) and relatively low weight children compared to children with normal stature and weight. This research is a case-control study of 86 pre-pubertal healthy children, mean age 5.9 ± 1.5 years. The study group comprised 43 ISS children; 43 age-matched children with normal stature and weight served as controls. Outcome measures included: dietary patterns and physical activity. The absolute daily average energy, protein and carbohydrate intake was significantly lower in the ISS children (P 〈 0.05); after correcting for body surface area, no significant differences were found between groups. Intake of micronutrients calcium, iron, zinc, vitamin A and vitamin C, expressed as percentage from Recommended Dietary Allowance, was significantly lower in the ISS children (P 〈 0.05), who had lower food responsiveness, higher satiety responsiveness, lesser enjoyment of food and were slower eaters (P 〈 0.001). Physical activity was sedentary in both the ISS cases and controls. Our findings in healthy, pre-pubertal, relatively lean ISS children point to a distinct eating pattern with no alteration in physical activity. Understanding the differences in dietary intake and eating behaviors may be beneficial in the development of targeted nutritional intervention for lean ISS children.展开更多
From a strategic perspective,the paper presents a forward-looking thinking supported by interdisciplinary of modern logistics,estuary and coast,environment and ecology,economic management and mathematical statistics. ...From a strategic perspective,the paper presents a forward-looking thinking supported by interdisciplinary of modern logistics,estuary and coast,environment and ecology,economic management and mathematical statistics. It leads to a reasonable solution to space expansion by reclamation. Construction of new deepwater terminal is the best usage of land resources and can strengthen the status of Shanghai as an international shipping center,thus support the preparation and strategic decision of future urban development of Shanghai.展开更多
In this paper, we propose a new input-to-state stable (ISS) synchronization method for chaotic behavior in nonlinear Bloch equations with external disturbance. Based on Lyapunov theory and linear matrix inequality ...In this paper, we propose a new input-to-state stable (ISS) synchronization method for chaotic behavior in nonlinear Bloch equations with external disturbance. Based on Lyapunov theory and linear matrix inequality (LMI) approach, for the first time, the ISS synchronization controller is presented to not only guarantee the asymptotic synchronization but also achieve the bounded synchronization error for any bounded disturbance. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation study is presented to demonstrate the effectiveness of the proposed synchronization scheme.展开更多
If one aims at choosing a fundamental rule of international aviation law, doubtlessly the one selected would be principle of air sovereignty. And although having been respected by international community for decades, ...If one aims at choosing a fundamental rule of international aviation law, doubtlessly the one selected would be principle of air sovereignty. And although having been respected by international community for decades, its strict observance may paradoxically pose danger for civil aviation-a mean of transport universally concerned to be the safest in the world, Of course, States make best efforts to secure civil airplanes from attacks-beginning with prohibition of use of force arising from Charter of the United Nations finishing with provisions of Montreal Convention. Nevertheless, history of aviation has given multiple cases of shooting down aircraft, many due to conviction by States that their airspace was infringed. This paper aims at presenting an overview of principle of air sovereignty and analysis of selected aviation incidents and accidents caused by shooting down from the perspective of international law.展开更多
This paper compares the differences of information presentation in the straight news reports about international air disasters in ChD (China Daily) and NYT (The New York Times). The type of straight news report is...This paper compares the differences of information presentation in the straight news reports about international air disasters in ChD (China Daily) and NYT (The New York Times). The type of straight news report is regarded as the most objective news report in the journalistic field. The purpose of this research is to find out the different journalistic cultures or orientations between Chinese and American newspapers when they report the same world event. This paper finds that ChD prefers to provide more information for the consequences of the event and reactions to it usually by making general and static statements. NYT attaches more importance to background introduction and is more liable to use detailed and dynamic description展开更多
The International Civil Aviation Organization (ICAO) is a specialized agency of the United Nations. Functionally, it has emerged as the organizational necessity of both the universal complex structure and the import...The International Civil Aviation Organization (ICAO) is a specialized agency of the United Nations. Functionally, it has emerged as the organizational necessity of both the universal complex structure and the importance of its overall activity. It was created on the basis of Article 57 of the United Nations Charter, stipulating that the specialized UN agencies are autonomous international organizations. They enjoy their autonomy on the basis of the contract they were established by, being engaged in activities within the United Nations system. On the territories the organization member states comprise, they enjoy privileges and immunities, having the international legal capacity to carry out their activities in accordance to the Statute. The 1944 Multilateral Convention was to establish both protection and efficient development of international civil aviation. In accordance to that rights and obligations of member states were established. It is of a special importance to emphasize obligation of parties to take their parts in both co-operation and programs aimed at improvement of international transport, navigational equipment, and installations. In the globalized world of today, air traffic is an irreplaceable part of the system of communication. It enables fast and timely business contacts between the people from various continents, as well as transport of goods.展开更多
There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We e...There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We evaluated the sediment delivery from plots to watersheds at the event or intra-annual, annual, and inter-annual timescales within the Wudinghe river basin, a 30,261 km2 basin in the Loess Plateau. We calculated the ratio of sediment output to sediment input and presented the temporal change of the channel morphology to determine whether sediment deposition occurs.Although a single flood event frequently has a sediment yield exceeding 10,000 t km-2, sediment deposition rarely occurs except during some small runoff events(sediment yield < 5000 t km-2) or dry years(sediment yield < 10,000 t km-2) when moving from slopes up to the main channels of the Wudinghe River. This observation suggests a sediment delivery ratio close to 1 even at the event or intra-annual and the annual timescales, but not necessarily at the interannual timescale. Such a high sediment delivery ratio can be related to hyper-concentrated flows, which have very strong sediment transport capacity even at low flow strength. Because hyper-concentrated flows are well-developed in the whole Loess Plateau, a sediment delivery ratio close to 1 below the interannual timescale possibly remains true for other rivers in the Loess Plateau.展开更多
基金Project supported by the National Natural Science Foundation of China (Nos. 40671099 and 40701084)the Director Program of the Key Laboratory of Soybean Biology of Ministry of Education, China (No. SB05B02)
文摘The dynamics of rhizosphere microbial communities is important for plant health and productivity, and can be influenced by soil type, plant species or genotype, and plant growth stage. A pot experiment was carried out to examine the dynamics of microbial communities in the rhizosphere of two soybean genotypes grown in a black soil in Northeast China with a long history of soybean cultivation. The two soybean genotypes, Beifeng 11 and Hai 9731, differing in productivity were grown in a mixture of black soil and siliceous sand. The bacterial communities were compared at three zone locations including rhizoplane, rhizosphere, and bulk soil at the third node (V3), early flowering (R1), and early pod (R3) stages using polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DCGE) of 16S rDNA. The results of principal component analyses (PCA) showed that the bacterial community structure changed with growth stage. Spatially, the bacterial communities in the rhizoplane and rhizosphere were significantly different from those in the bulk soil. Nevertheless, the bacterial communities in the rhizoplane were distinct from those in the rhizosphere at the V3 stage, while no obvious differences were found at the R1 and R3 stages. For the two genotypes, the bacterial community structure was similar at the V3 stage, but differed at the R1 and R3 stages. In other words, some bacterial populations became dominant and some others recessive at the two later stages, which contributed to the variation of the bacterial community between the two genotypes. These results suggest that soybean plants can modify the rhizosphere bacterial communities in the black soil, and there existed genotype-specific bacterial populations in the rhizospbere, which may be related to soybean productivity.
基金Under the auspices of the National Natural Science Foundation of China (No. 40371030)
文摘Shift-share analysis has been confirmed a useful approach in the study of regional economics and many kinds of extended shift-share models have been advanced and put into practice in economic studies, but few have hitherto been introduced and applied to the tourism research in China. Moreover understanding the spatially competitive relationship is of paramount importance for marketers, developers, and planners involved in tourism strategy development. Based on international tourism receipts from 1995 to 2004, this study aims at probing into the spatial competitiveness of interna- tional tourism in Jiangsu Province in comparison with its neighbors by applying a spatially extended shift-share model and a modified dynamic shift-share model. The empirical results illustrate that exceptional years may exist in the ap- plication of dynamic shift-share models. To solve this issue, modifications to dynamic shift-share model are put forward. The analytical results are not only presented but also explained by the comparison of background conditions of tourism development between Jiangsu and its key competitors. The conclusions can be drawn that the growth of international tourism receipts in Jiangsu mainly attributes to the national component and the competitive component and Zhejiang is the most important rival to Jiangsu during the period of 1995-2004. In order to upgrade the tourism competitiveness, it is indispensable for Jiangsu to take proper positioning, promoting and marketing strategies and to cooperate and integrate with its main rivals.
基金supported by the National Natural Science Foundation of China (Grant No. 40730952)the National Basic Research Program of China (Grant No. 2009CB421405)the Program of Knowledge Innovation for the third period, the Chinese Academy of Sciences (Grant No. KZCX2-YW-220), and IAP07414
文摘The present study investigates the difference in interdecadal variability of the spring and summer sensible heat fluxes over Northwest China by using station observations from 1960 to 2000. It was found that the spring sensible heat flux over Northwest China was greater during the period from the late 1970s to the 1990s than during the period from the 1960s to the mid-1970s. The summer sensible heat flux was smaller in the late 1980s through the 1990s than it was in the 1970s through the early 1980s. Both the spring and summer land-air temperature differences over Northwest China displayed an obvious interdecadal increase in the late 1970s. Both the spring and summer surface wind speeds experienced an obvious interdecadal weakening in the late 1970s. The change in the surface wind speed played a more important role in the interdecadal variations in sensible heat flux during the summer, whereas the change in the land-air temperature difference was more important for the interdecadal variations in sensible heat flux in the spring. This difference was related to seasonal changes in the mean land-air temperature difference and the surface wind speed. Further analysis indicated that the increase in the spring land surface temperature in Northwest China was related to an increase in surface net radiation.
文摘The amount of waste heat in a space facility became larger, because of increase in the space platform size and its power consumption. It requires development of high-performance space thermal management systems handling a large amount of waste. Boiling two-phase flow could become powerful means for this system because a boiling and condensation system is one of the most efficient modes of heat transfer due to phase change (liquid-vapor). However, gravity effects on boiling two-phase flow phenomena and the corresponding heat transfer characteristics are not clear. Therefore, we prepare the experiments of boiling two-phase flow utilizing a long-term microgravity environment onboard a Japanese Experimental Module "KIBO" in the International Space Station (ISS) as one of the JAXA official projects. In this paper, recent progress of the preparation for the project is reported.
基金supported by the National Natural Science Foundation of China (Grant Nos. 41005078 and 41175127)
文摘Abstract Chinese air pollution has increased in this century along with the rapid socioeconomic development and resulting anthropogenic emissions. While recent emission control measures have shown encouraging re sults and have reduced the levels of sulfur dioxide and primary aerosols, the concentrations of other air pollutants continue to grow, particularly secondary pollutants in cluding ozone and secondary aerosols. Meanwhile, a va riety of intentional and unintentional socioeconomic events have temporarily changed the pace, and even the signs, of growth of air pollution. These events include the short-term emission restrictions imposed during the Sino-African Summit, the Beijing Olympics and Para lympics, the Shanghai World Exposition (Shanghai Expo), the Guangzhou Asian Olympics, and the Shenzhen Uni versiade, as well as the unintentional emission reductions associated with the recent economic recession and the annual Chinese New Year. This paper presents a brief overview of trends and temporary perturbations of Chi nese air pollution since 2000, summarizing studies on anthropogenic emission inventories, atmospheric meas urements, and inverse modeling. It concludes with rec ommendations for future research.
基金Under the auspices of Major State Basic Research Development Program of China(No.2010CB951202)Ocean Public Welfare Scientific Research Project,State Oceanic Administration of the People's Republic of China(No.200805063)
文摘Based on the data from gauging stations, the changes in water discharge and sediment load of the Huanghe (Yellow) River were analyzed by using the empirical mode decomposition (EMD) method. The results show that the periodic oscillation of water discharge and sediment load of the Huanghe River occurs at the interannual, decadal, and multi-decadal scales, caused by the periodic oscillations of precipitation, and E1 Nifio/Southern Oscillation (ENSO) af- fects water discharge by influencing precipitation distribution and contributes to periodic varations in precipitation and water discharge at interannual timescale. The water discharge and sediment load of the Huanghe River have decreased since the 1960s under the influence of precipitation and huamn activities, and human activities attribute more than precipitation to the reduction in the water discharge and sediment load, furthermore, water abstraction and water-soil conservation practices are the main causes of the decrease in water discharge and sediment load, respectively. The reduction in sediment load has directly impacted on the lower reaches of the Huanghe River and the river delta, causing considerable erosion of the river channel in the lower reaches since the 1970s along with River Delta changing siltation into erosion around 2000.
文摘Nutrition plays an essential role in normal linear growth in children. Knowledge of the eating styles and dietary consumption of healthy short children from developed countries is scarce. The aim of this study was to investigate the dietary patterns in idiopathic short stature (ISS) and relatively low weight children compared to children with normal stature and weight. This research is a case-control study of 86 pre-pubertal healthy children, mean age 5.9 ± 1.5 years. The study group comprised 43 ISS children; 43 age-matched children with normal stature and weight served as controls. Outcome measures included: dietary patterns and physical activity. The absolute daily average energy, protein and carbohydrate intake was significantly lower in the ISS children (P 〈 0.05); after correcting for body surface area, no significant differences were found between groups. Intake of micronutrients calcium, iron, zinc, vitamin A and vitamin C, expressed as percentage from Recommended Dietary Allowance, was significantly lower in the ISS children (P 〈 0.05), who had lower food responsiveness, higher satiety responsiveness, lesser enjoyment of food and were slower eaters (P 〈 0.001). Physical activity was sedentary in both the ISS cases and controls. Our findings in healthy, pre-pubertal, relatively lean ISS children point to a distinct eating pattern with no alteration in physical activity. Understanding the differences in dietary intake and eating behaviors may be beneficial in the development of targeted nutritional intervention for lean ISS children.
基金Shanghai Science and Technology Research Plan(No.13dz1204900)
文摘From a strategic perspective,the paper presents a forward-looking thinking supported by interdisciplinary of modern logistics,estuary and coast,environment and ecology,economic management and mathematical statistics. It leads to a reasonable solution to space expansion by reclamation. Construction of new deepwater terminal is the best usage of land resources and can strengthen the status of Shanghai as an international shipping center,thus support the preparation and strategic decision of future urban development of Shanghai.
文摘In this paper, we propose a new input-to-state stable (ISS) synchronization method for chaotic behavior in nonlinear Bloch equations with external disturbance. Based on Lyapunov theory and linear matrix inequality (LMI) approach, for the first time, the ISS synchronization controller is presented to not only guarantee the asymptotic synchronization but also achieve the bounded synchronization error for any bounded disturbance. The proposed controller can be obtained by solving a convex optimization problem represented by the LMI. Simulation study is presented to demonstrate the effectiveness of the proposed synchronization scheme.
文摘If one aims at choosing a fundamental rule of international aviation law, doubtlessly the one selected would be principle of air sovereignty. And although having been respected by international community for decades, its strict observance may paradoxically pose danger for civil aviation-a mean of transport universally concerned to be the safest in the world, Of course, States make best efforts to secure civil airplanes from attacks-beginning with prohibition of use of force arising from Charter of the United Nations finishing with provisions of Montreal Convention. Nevertheless, history of aviation has given multiple cases of shooting down aircraft, many due to conviction by States that their airspace was infringed. This paper aims at presenting an overview of principle of air sovereignty and analysis of selected aviation incidents and accidents caused by shooting down from the perspective of international law.
文摘This paper compares the differences of information presentation in the straight news reports about international air disasters in ChD (China Daily) and NYT (The New York Times). The type of straight news report is regarded as the most objective news report in the journalistic field. The purpose of this research is to find out the different journalistic cultures or orientations between Chinese and American newspapers when they report the same world event. This paper finds that ChD prefers to provide more information for the consequences of the event and reactions to it usually by making general and static statements. NYT attaches more importance to background introduction and is more liable to use detailed and dynamic description
文摘The International Civil Aviation Organization (ICAO) is a specialized agency of the United Nations. Functionally, it has emerged as the organizational necessity of both the universal complex structure and the importance of its overall activity. It was created on the basis of Article 57 of the United Nations Charter, stipulating that the specialized UN agencies are autonomous international organizations. They enjoy their autonomy on the basis of the contract they were established by, being engaged in activities within the United Nations system. On the territories the organization member states comprise, they enjoy privileges and immunities, having the international legal capacity to carry out their activities in accordance to the Statute. The 1944 Multilateral Convention was to establish both protection and efficient development of international civil aviation. In accordance to that rights and obligations of member states were established. It is of a special importance to emphasize obligation of parties to take their parts in both co-operation and programs aimed at improvement of international transport, navigational equipment, and installations. In the globalized world of today, air traffic is an irreplaceable part of the system of communication. It enables fast and timely business contacts between the people from various continents, as well as transport of goods.
基金funded by National Natural Science Foundation of China (Grant Nos. 41230746, 41271306)the National Key Technology Research and Development Program (Grant No. 2012BAC09B03)the Open-fund Project of Jiangxi Provincial Key Laboratory of Soil Erosion and Prevention (Grant No. JXSB201301)
文摘There is a consensus that sediment delivery ratio in the Chinese Loess Plateau is close to 1at the inter-annual timescale. However, little information is available about the sediment delivery at finer timescales. We evaluated the sediment delivery from plots to watersheds at the event or intra-annual, annual, and inter-annual timescales within the Wudinghe river basin, a 30,261 km2 basin in the Loess Plateau. We calculated the ratio of sediment output to sediment input and presented the temporal change of the channel morphology to determine whether sediment deposition occurs.Although a single flood event frequently has a sediment yield exceeding 10,000 t km-2, sediment deposition rarely occurs except during some small runoff events(sediment yield < 5000 t km-2) or dry years(sediment yield < 10,000 t km-2) when moving from slopes up to the main channels of the Wudinghe River. This observation suggests a sediment delivery ratio close to 1 even at the event or intra-annual and the annual timescales, but not necessarily at the interannual timescale. Such a high sediment delivery ratio can be related to hyper-concentrated flows, which have very strong sediment transport capacity even at low flow strength. Because hyper-concentrated flows are well-developed in the whole Loess Plateau, a sediment delivery ratio close to 1 below the interannual timescale possibly remains true for other rivers in the Loess Plateau.