The Sanjiang Plain, formed with confluence of the Amur River, Ussuri River and Songhua River, is one of the three major stretches of wetland in the world. The large-scale agricultural development on the Sanjiang Plain...The Sanjiang Plain, formed with confluence of the Amur River, Ussuri River and Songhua River, is one of the three major stretches of wetland in the world. The large-scale agricultural development on the Sanjiang Plain started at the end of the 40s of the 20th century. The low-lying terrain and frequent floods caused a lot of difficulties to the agricultural development in the area. Water conservancy program has always been the kernel in agricultural development on the Sanjiang Plain in its history. The entities involved in its development project from different levels, including the state, state farms and farmers. Thus far, we have used the findings of their analysis of the paddy field development process at one state farm to take a microscopic approach to shed light on the development of paddy fields by farms and farmers and their roles in subsequent rice production. Because paddy field management on the Sanjiang Plain is very broad, but its rice producing techniques and economic structure have a certain definite form, the microscopic approach to understanding the paddy field development process and rice fanning management structure on the level of farmers could be considered a success. This paper is intended to elucidate from a macroscopic perspective the characteristics of the rapid development of irrigation and drainage systems and paddy fields on the Sanjiang Plain. Sanjiang Plain is a flood plain, and so major infrastructure development was required, thereby necessitating this national project for flood control. As politics and an economic integrated body, state farms also contributed to the promotion of agricultural development. As principals for the development, the state and state farms are taken by this paper as the main objects of our analysis.展开更多
Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Se...Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Sea of Okhotsk and limited the primary productivity in the North Pacific Ocean.This study was conducted to investigate the chemical forms of iron in different aquatic environments(agricultural water including groundwater,paddy water,and canal water;wetland water including marsh water,marsh streams,and main streams) with the cross-flow filtration method to reveal the transportation and transformation characteristics of iron in response to major land use changes.In addition,the factors affecting iron behavior in different water bodies were reviewed.In marsh water and streams,the concentrations of dissolved iron were higher due to the high organic matter contents and marsh water becoming the main iron source for river water.The conversion of dissolved iron into acid-labile iron occurred during the discharge of wetland water into marsh rivers.Iron primarily existed in both the >0.7 and <0.01 μm size fractions,accounting for about 58.3% and 26.4% of the total dissolved iron,respectively.In agricultural irrigation systems,ferrous ion entered the paddy fields from groundwater,and a fraction of this ferrous iron was subsequently converted into high molecular weight and medium molecular weight iron(colloid iron) in paddy and canal water.However,the concentrations of total dissolved iron decreased by 62.5% from underground to the surface due to the formation of precipitates.Despite this,water discharge in agriculture is still an important iron source for rivers and has the potential to supplement iron due to its higher acid-labile iron concentrations.Land use and cover change and agricultural irrigation increased the iron content of surface soil,but reduced the output of iron in water systems.Overall,the concentration of total dissolved iron in water systems has been reduced to 42.6% by wetland reclamation.展开更多
文摘The Sanjiang Plain, formed with confluence of the Amur River, Ussuri River and Songhua River, is one of the three major stretches of wetland in the world. The large-scale agricultural development on the Sanjiang Plain started at the end of the 40s of the 20th century. The low-lying terrain and frequent floods caused a lot of difficulties to the agricultural development in the area. Water conservancy program has always been the kernel in agricultural development on the Sanjiang Plain in its history. The entities involved in its development project from different levels, including the state, state farms and farmers. Thus far, we have used the findings of their analysis of the paddy field development process at one state farm to take a microscopic approach to shed light on the development of paddy fields by farms and farmers and their roles in subsequent rice production. Because paddy field management on the Sanjiang Plain is very broad, but its rice producing techniques and economic structure have a certain definite form, the microscopic approach to understanding the paddy field development process and rice fanning management structure on the level of farmers could be considered a success. This paper is intended to elucidate from a macroscopic perspective the characteristics of the rapid development of irrigation and drainage systems and paddy fields on the Sanjiang Plain. Sanjiang Plain is a flood plain, and so major infrastructure development was required, thereby necessitating this national project for flood control. As politics and an economic integrated body, state farms also contributed to the promotion of agricultural development. As principals for the development, the state and state farms are taken by this paper as the main objects of our analysis.
基金supported by National Basic Research Program of China (Grant No. 2004CB418502)
文摘Wetland reclamation has been ongoing in the Sanjiang Plain since the mid-1950s,which has resulted in major changes in wetlands and the agriculture ecosystem in the region that have influenced the iron output to the Sea of Okhotsk and limited the primary productivity in the North Pacific Ocean.This study was conducted to investigate the chemical forms of iron in different aquatic environments(agricultural water including groundwater,paddy water,and canal water;wetland water including marsh water,marsh streams,and main streams) with the cross-flow filtration method to reveal the transportation and transformation characteristics of iron in response to major land use changes.In addition,the factors affecting iron behavior in different water bodies were reviewed.In marsh water and streams,the concentrations of dissolved iron were higher due to the high organic matter contents and marsh water becoming the main iron source for river water.The conversion of dissolved iron into acid-labile iron occurred during the discharge of wetland water into marsh rivers.Iron primarily existed in both the >0.7 and <0.01 μm size fractions,accounting for about 58.3% and 26.4% of the total dissolved iron,respectively.In agricultural irrigation systems,ferrous ion entered the paddy fields from groundwater,and a fraction of this ferrous iron was subsequently converted into high molecular weight and medium molecular weight iron(colloid iron) in paddy and canal water.However,the concentrations of total dissolved iron decreased by 62.5% from underground to the surface due to the formation of precipitates.Despite this,water discharge in agriculture is still an important iron source for rivers and has the potential to supplement iron due to its higher acid-labile iron concentrations.Land use and cover change and agricultural irrigation increased the iron content of surface soil,but reduced the output of iron in water systems.Overall,the concentration of total dissolved iron in water systems has been reduced to 42.6% by wetland reclamation.
