The coastal lowlands in northern Jiangsu Province, China, is characterized by low relief and low water surface gradient in streams. The flooding stages are commonly lower than the high-tide level and the tidal range i...The coastal lowlands in northern Jiangsu Province, China, is characterized by low relief and low water surface gradient in streams. The flooding stages are commonly lower than the high-tide level and the tidal range is relatively small. All these factors prohibit rapid discharge of floodwater and make the flood regimes here extremely sensitive to the sea level rise. The 1991 Plum Rain was examined, when precipitation was significantly higher than normal. The one-dimensional open-channel non-conservative flow model was used to simulate the stream flow in the channel network of studied area. GIS technology was used to delineate the maximum in undated area by analyzing the DEMs.展开更多
Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction a...Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction and peat fraction) of the bulk peat samples were investigated by AMS-dating and which fraction is better to help construct an age framework for the boreholes were compared and discussed. The results indicated that the peat fraction give a good dating results sequence in the boreholes, compared with the corresponding organic sediment fraction. And the dating results of organic sediment fraction show 161-6 702 years older than corresponding peat fraction, which was caused by marine influence. Then, we suggest an experience formula as y =0.99 x-466.5 by the correlation analysis for correcting the marine influenced organic sediment ages within the conventional ages between 4 000 to 9 000 yrs BP, and more study should be carried out for the AMS ^(14)C dating of the bulk organic sediments.展开更多
Tropical Asia is a region comprising South and Southeast Asia and under strong influence of the Asianmonsoon climate. It is characterized by an extremely high population density and by high land use intensity.Paddy ri...Tropical Asia is a region comprising South and Southeast Asia and under strong influence of the Asianmonsoon climate. It is characterized by an extremely high population density and by high land use intensity.Paddy rice cultivation is the most important form of agriculture in the greater part of the region. Soilresources of tropical Asia have a specific feature in comparison with tropical Africa and America. Ultisolsdominate in uplands, and lowland soils like Inceptisols and Histosols are relatively abundant. The latterpoint is made clearer if we take the landforms of the region with a vast extent of lowlands into consideration.Geologically, tropical Asia with the Himalayan orogeny and active volcanism exhibits a conspicuous contrastto tropical Africa and America with the dominance of the shield structure. This along with the monsoonclimate should have determined the basic features of landforms and soil, and accordingly all the agriculturaland social characteristics of tropical Asia today. Although paddy rice cultivation in the lowland is highlysustainable, upland cultivation in extensive Ultisol areas tends to be handicapped by low fertility and higherodibility of the soil, resulting in low sustainability. Land shortage is compelling people to exploit slopelandsin hills and mountains, on the one hand, and thus far unutilized coastal lowlands, on the other. Both ofthese new reclamations are facing to serious land degradation problems today. Tropical Asia will continueto be the most densely populated region of the world with ever-increasing population. In order to meet theincreasing food demand lowland rice cultivation should be intensified by the infrastructure development toease the stresses on slopelands and vulnerable coastal lowlands. At the same time, upland crop productionin Ultisol areas should be stabilized and enhanced, providing integrated nutrient management and measuresfor soil conservation.展开更多
基金Project supported by the SUS-DSD Cooperative Foundation between the Netherlands and China
文摘The coastal lowlands in northern Jiangsu Province, China, is characterized by low relief and low water surface gradient in streams. The flooding stages are commonly lower than the high-tide level and the tidal range is relatively small. All these factors prohibit rapid discharge of floodwater and make the flood regimes here extremely sensitive to the sea level rise. The 1991 Plum Rain was examined, when precipitation was significantly higher than normal. The one-dimensional open-channel non-conservative flow model was used to simulate the stream flow in the channel network of studied area. GIS technology was used to delineate the maximum in undated area by analyzing the DEMs.
基金Supported by the China Geological Survey(No.121201006000182401)the National Natural Science Foundation of China(Nos.41476074,41372173)
文摘Peat in boreholes is the most important ^(14)C dating material used for constructing age framework. 20 bulk peat samples were collected from five boreholes, the ^(14)C ages of two fractions(organic sediment fraction and peat fraction) of the bulk peat samples were investigated by AMS-dating and which fraction is better to help construct an age framework for the boreholes were compared and discussed. The results indicated that the peat fraction give a good dating results sequence in the boreholes, compared with the corresponding organic sediment fraction. And the dating results of organic sediment fraction show 161-6 702 years older than corresponding peat fraction, which was caused by marine influence. Then, we suggest an experience formula as y =0.99 x-466.5 by the correlation analysis for correcting the marine influenced organic sediment ages within the conventional ages between 4 000 to 9 000 yrs BP, and more study should be carried out for the AMS ^(14)C dating of the bulk organic sediments.
文摘Tropical Asia is a region comprising South and Southeast Asia and under strong influence of the Asianmonsoon climate. It is characterized by an extremely high population density and by high land use intensity.Paddy rice cultivation is the most important form of agriculture in the greater part of the region. Soilresources of tropical Asia have a specific feature in comparison with tropical Africa and America. Ultisolsdominate in uplands, and lowland soils like Inceptisols and Histosols are relatively abundant. The latterpoint is made clearer if we take the landforms of the region with a vast extent of lowlands into consideration.Geologically, tropical Asia with the Himalayan orogeny and active volcanism exhibits a conspicuous contrastto tropical Africa and America with the dominance of the shield structure. This along with the monsoonclimate should have determined the basic features of landforms and soil, and accordingly all the agriculturaland social characteristics of tropical Asia today. Although paddy rice cultivation in the lowland is highlysustainable, upland cultivation in extensive Ultisol areas tends to be handicapped by low fertility and higherodibility of the soil, resulting in low sustainability. Land shortage is compelling people to exploit slopelandsin hills and mountains, on the one hand, and thus far unutilized coastal lowlands, on the other. Both ofthese new reclamations are facing to serious land degradation problems today. Tropical Asia will continueto be the most densely populated region of the world with ever-increasing population. In order to meet theincreasing food demand lowland rice cultivation should be intensified by the infrastructure development toease the stresses on slopelands and vulnerable coastal lowlands. At the same time, upland crop productionin Ultisol areas should be stabilized and enhanced, providing integrated nutrient management and measuresfor soil conservation.
