A special kind of rice field exists in China that is flooded year-round. These rice fields have substantially large CH4 emissions during the rice-growing season and emit CH4 continuously in the non-rice growing season...A special kind of rice field exists in China that is flooded year-round. These rice fields have substantially large CH4 emissions during the rice-growing season and emit CH4 continuously in the non-rice growing season. CH4 emission factors were used to estimate the CH4 emissions from year-round flooded rice fields during the rice-growing season in China. The CH4 emissions for the year-round flooded rice fields in China for the rice growing season over a total area of 2.66 Mha were estimated to be 2.44 Tg CH…展开更多
The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and se...The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1.15~C increasing in annual mean surface air temperature over the past 50 years （0.23°C per decade）, the annual pan evaporation has steadily declined by an average rate of-7.65 mm per year. By comparison, this change is greater than those previously reported in China. Significant decreasing trends in annual pan evaporation have been observed at almost all stations. As a whole, seasonal pan evaporation decreased significantly, especially in summer, whereas seasonal temperature increased significantly, except in summer. Thus, the pan evaporation paradox exists in the lower Yellow River Basin. The trend analysis of other meteorological factors indicates significant decrease in sunshine duration and wind speed, but no significant variations in precipitation and relative humidity at annual and seasonal time scales. By examining the relationship between precipitation and pan evaporation, it did not show a concurrent decrease in pan evaporation and increase in precipitation. The partial correlation analysis discovered that the primary cause of decrease in annual and seasonal pan evaporation is the decrease in wind speed. A further examination using a stepwise regression shows that decrease in wind speed and sunshine duration, and increase in mean temperature axe likely to be the main meteorological factors affecting the annual and seasonal pan evaporation in the lower Yellow River Basin over the past 50 years.展开更多
We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population （M. aeruginosa） and their correlation with environmental factors in the water source area of Chaohu City, China ...We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population （M. aeruginosa） and their correlation with environmental factors in the water source area of Chaohu City, China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass, and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June, and the biomass of cyanobacteria reached a maximum in August. From February to March 2012, the main form of M. aeruginosa was the single-cell form; M. aeruginosa colonies began to appear from April, and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July, and then gradually decreased from August. The diameter range ofM. aeruginosa colonies was 18.37-237.77μm, and most of the colonies were distributed in the range 20-200μm, comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobaeterial growth was in the range of 15-30℃. In natural water bodies, photosynthetically active radiation had a significant positive influence on the colonial diameter of M. aeruginosa （P〈0.01）.展开更多
文摘A special kind of rice field exists in China that is flooded year-round. These rice fields have substantially large CH4 emissions during the rice-growing season and emit CH4 continuously in the non-rice growing season. CH4 emission factors were used to estimate the CH4 emissions from year-round flooded rice fields during the rice-growing season in China. The CH4 emissions for the year-round flooded rice fields in China for the rice growing season over a total area of 2.66 Mha were estimated to be 2.44 Tg CH…
基金supported by the Climate Change Science Foundation of China Meteorological Administration(No.CCSF2011-1)
文摘The annual and seasonal trends in pan evaporation in the lower Yellow River Basin based on quality-controlled data from 10 meteorological stations in 1961-2010 are analyzed. The causes for the changes in annual and seasonal pan evaporation are also discussed. The results suggest that, despite the 1.15~C increasing in annual mean surface air temperature over the past 50 years （0.23°C per decade）, the annual pan evaporation has steadily declined by an average rate of-7.65 mm per year. By comparison, this change is greater than those previously reported in China. Significant decreasing trends in annual pan evaporation have been observed at almost all stations. As a whole, seasonal pan evaporation decreased significantly, especially in summer, whereas seasonal temperature increased significantly, except in summer. Thus, the pan evaporation paradox exists in the lower Yellow River Basin. The trend analysis of other meteorological factors indicates significant decrease in sunshine duration and wind speed, but no significant variations in precipitation and relative humidity at annual and seasonal time scales. By examining the relationship between precipitation and pan evaporation, it did not show a concurrent decrease in pan evaporation and increase in precipitation. The partial correlation analysis discovered that the primary cause of decrease in annual and seasonal pan evaporation is the decrease in wind speed. A further examination using a stepwise regression shows that decrease in wind speed and sunshine duration, and increase in mean temperature axe likely to be the main meteorological factors affecting the annual and seasonal pan evaporation in the lower Yellow River Basin over the past 50 years.
基金Supported by the Major Science and Technology Program for Water Pollution Control and Treatment of China(Nos.2012ZX07103-005-01,2012ZX07103-004-02)the National Natural Science Foundation of China(Nos.41171366,41471075)the Science Foundation of Nanjing Institute of Geography and Limnology,Chinese Academy of Sciences(No.NIGLAS2012135013)
文摘We investigated seasonal variations in cyanobacterial biomass and the forms of its dominant population （M. aeruginosa） and their correlation with environmental factors in the water source area of Chaohu City, China from December 2011 to October 2012. The results show that species belonging to the phylum Cyanophyta occupied the maximum proportion of phytoplankton biomass, and that the dominant population in the water source area of Chaohu City was M. aeruginosa. The variation in cyanobacterial biomass from March to August 2012 was well fitted to the logistic growth model. The growth rate of cyanobacteria was the highest in June, and the biomass of cyanobacteria reached a maximum in August. From February to March 2012, the main form of M. aeruginosa was the single-cell form; M. aeruginosa colonies began to appear from April, and blooms appeared on the water surface in May. The maximum diameter of the colonies was recorded in July, and then gradually decreased from August. The diameter range ofM. aeruginosa colonies was 18.37-237.77μm, and most of the colonies were distributed in the range 20-200μm, comprising 95.5% of the total number of samples. Temperature and photosynthetically active radiation may be the most important factors that influenced the annual variation in M. aeruginosa biomass and forms. The suitable temperature for cyanobaeterial growth was in the range of 15-30℃. In natural water bodies, photosynthetically active radiation had a significant positive influence on the colonial diameter of M. aeruginosa （P〈0.01）.
