Our analysis of fog and haze observations from the surface weather stations in China in recent 50 years （from 196l to 2011） shows that the number of fog days has experienced two-stage variations, with an increasing ...Our analysis of fog and haze observations from the surface weather stations in China in recent 50 years （from 196l to 2011） shows that the number of fog days has experienced two-stage variations, with an increasing trend before 1980 and a decreasing trend after 1990. Especially, an obvious decreasing trend after 1990 can be clearly seen, which is consistent with the decreas- ing trend of the surface relative humidity. However, the number of haze days has demonstrated an increasing trend. As such, the role of reduction of atmospheric relative humidity in the transition process from fog into haze has been further investigated. It is estimated that the mean relative humidity of haze days is about 69%, lower than previously estimated, which implies that it is more difficult for the haze particles to transform into fog drops. This is possibly one of the major environmental factors leading to the reduction of number of fog days. The threshold of the relative humidity for transition from fog into haze is about 82%, also lower than previously estimated. Thus, the reduction of the surface relative humidity in China mainly due to the in- crease of the surface temperature and the saturation specific humidity may exert an obvious impact on the environmental con- ditions for the formations of fog and haze. In addition, our investigation of the relationship between haze and visibility reveals that with the increase of haze days, the visibility has declined markedly. Since 1961, the mean visibility has dropped from 4-10 to 2-4 kin, about a half of the previous horizontal distance of visibility.展开更多
Long-term changes in soil pH, the current status of soil acidification, and the response of bulk soil and soil water pH to experimental nitrogen addition under three subtropical forests were investigated in Dinghushan...Long-term changes in soil pH, the current status of soil acidification, and the response of bulk soil and soil water pH to experimental nitrogen addition under three subtropical forests were investigated in Dinghushan Biosphere Reserve of subtropical China. The results showed that the mineral soil pH at 0-20 cm depth declined significantly from 4.60-4.75 in 1980s to 3.84-4.02 in 2005. Nitrogen addition resulted in the decrease of pH in both bulk soil and soil water collected at 20-cm depth. The rapid decline of soil pH was attributed to long-term high atmospheric acid deposition (nitrogen and sulphur) therein. The forest at earlier succession stage with originally higher soil pH appeared to be more vulnerable to acid deposition than that at later succession stage with originally low soil pH.展开更多
Laizhou Bay provides a critical spawning and nursery habitat for many fishery species, including commercially important spe- cies, such as Fenneropenaeus chinensis and Larimichthys polyactis. The bay is severely stres...Laizhou Bay provides a critical spawning and nursery habitat for many fishery species, including commercially important spe- cies, such as Fenneropenaeus chinensis and Larimichthys polyactis. The bay is severely stressed due to high fishing pressure and environmental changes. Based on the long-term ecosystem surveys in Laizhou Bay during the main spawning period （May） of most fishery species from 1959 to 2008, the responses of the Laizhou Bay fishery ecosystem were analyzed here, including regime shifts in species composition, biomass, species diversity, zooplankton, phytoplankton, and environmental variables. The dominant species of large-size and high economic value （e.g. Trichiurus haumela, L. polyactis） have been replaced by the short-lived, low-trophic-level planktivorous pelagic species （e.g. Setipinna taty, Engraulisjaponicus） since the 1980s, and it is probable that the small-sized pelagic fishes have been recently replaced by invertebrates （e.g. Oratosquilla oratoria, Crangon affinis）. The biomass of fishery resources declined continuously from 423.6 kg haul 1 h-1 in 1959 to 164.6 kg haul-l h i in 1982, 37.7 kg haul-1 h-1 in 1993, and less than 8 kg haul 1 h-a in 1998-2008. Moreover, the biomass of zooplankton showed an increasing trend during 1959-2006, but showed a slight decline in 2008. The abundance of phytoplankton increased from 1959 through 1982, decreased substantially in 1993, and increased again until 2004. More recently, however, the phytoplankton abundance was very low. The sea surface temperature （SST） and sea bottom temperature （SBT） in May increased by 0.23~C a-~ and 0.16~C a-~, respectively, during 1982-2008. The salinity in May showed large fluctuations and reached its lowest val- ues in 2004 and 2006. The ratio of dissolved inorganic nitrogen （DIN） to dissolved inorganic phosphate （DIP） increased. However, the dissolved silicon （DSi）：DIP and DSi：DIN ratios decreased to a low level during 1959-2008. These changes seri- ously impacted primary produ展开更多
基金supported by National Key Basic Research Program of China(Grant Nos.2012CB417205 and 2013CB430202)the National Natural Science Foundation of China(Grant No.41130960)National Science and Technology Support Program of China(Grant No.2009BAC51B02)
文摘Our analysis of fog and haze observations from the surface weather stations in China in recent 50 years （from 196l to 2011） shows that the number of fog days has experienced two-stage variations, with an increasing trend before 1980 and a decreasing trend after 1990. Especially, an obvious decreasing trend after 1990 can be clearly seen, which is consistent with the decreas- ing trend of the surface relative humidity. However, the number of haze days has demonstrated an increasing trend. As such, the role of reduction of atmospheric relative humidity in the transition process from fog into haze has been further investigated. It is estimated that the mean relative humidity of haze days is about 69%, lower than previously estimated, which implies that it is more difficult for the haze particles to transform into fog drops. This is possibly one of the major environmental factors leading to the reduction of number of fog days. The threshold of the relative humidity for transition from fog into haze is about 82%, also lower than previously estimated. Thus, the reduction of the surface relative humidity in China mainly due to the in- crease of the surface temperature and the saturation specific humidity may exert an obvious impact on the environmental con- ditions for the formations of fog and haze. In addition, our investigation of the relationship between haze and visibility reveals that with the increase of haze days, the visibility has declined markedly. Since 1961, the mean visibility has dropped from 4-10 to 2-4 kin, about a half of the previous horizontal distance of visibility.
基金Supported by the National Natural Science Foundation of China (Nos.30270282 and 40703030)the Key Project of the Chinese Ministry of Education (No.704037)+1 种基金the Doctoral Scientific Research Foundation of Guilin University of Electronic Technology,China (No.Z20718)the Guangxi Provincial Department of Education,China (No.200707MS048)
文摘Long-term changes in soil pH, the current status of soil acidification, and the response of bulk soil and soil water pH to experimental nitrogen addition under three subtropical forests were investigated in Dinghushan Biosphere Reserve of subtropical China. The results showed that the mineral soil pH at 0-20 cm depth declined significantly from 4.60-4.75 in 1980s to 3.84-4.02 in 2005. Nitrogen addition resulted in the decrease of pH in both bulk soil and soil water collected at 20-cm depth. The rapid decline of soil pH was attributed to long-term high atmospheric acid deposition (nitrogen and sulphur) therein. The forest at earlier succession stage with originally higher soil pH appeared to be more vulnerable to acid deposition than that at later succession stage with originally low soil pH.
基金supported by Special Fund for Agro-scientific Research in the Public Interest(Grant No.200903005)National Basic Research Program of China(Grant Nos.2011CB409805 and 2010CB951204)Taishan Scholar Program of Shandong Province
文摘Laizhou Bay provides a critical spawning and nursery habitat for many fishery species, including commercially important spe- cies, such as Fenneropenaeus chinensis and Larimichthys polyactis. The bay is severely stressed due to high fishing pressure and environmental changes. Based on the long-term ecosystem surveys in Laizhou Bay during the main spawning period （May） of most fishery species from 1959 to 2008, the responses of the Laizhou Bay fishery ecosystem were analyzed here, including regime shifts in species composition, biomass, species diversity, zooplankton, phytoplankton, and environmental variables. The dominant species of large-size and high economic value （e.g. Trichiurus haumela, L. polyactis） have been replaced by the short-lived, low-trophic-level planktivorous pelagic species （e.g. Setipinna taty, Engraulisjaponicus） since the 1980s, and it is probable that the small-sized pelagic fishes have been recently replaced by invertebrates （e.g. Oratosquilla oratoria, Crangon affinis）. The biomass of fishery resources declined continuously from 423.6 kg haul 1 h-1 in 1959 to 164.6 kg haul-l h i in 1982, 37.7 kg haul-1 h-1 in 1993, and less than 8 kg haul 1 h-a in 1998-2008. Moreover, the biomass of zooplankton showed an increasing trend during 1959-2006, but showed a slight decline in 2008. The abundance of phytoplankton increased from 1959 through 1982, decreased substantially in 1993, and increased again until 2004. More recently, however, the phytoplankton abundance was very low. The sea surface temperature （SST） and sea bottom temperature （SBT） in May increased by 0.23~C a-~ and 0.16~C a-~, respectively, during 1982-2008. The salinity in May showed large fluctuations and reached its lowest val- ues in 2004 and 2006. The ratio of dissolved inorganic nitrogen （DIN） to dissolved inorganic phosphate （DIP） increased. However, the dissolved silicon （DSi）：DIP and DSi：DIN ratios decreased to a low level during 1959-2008. These changes seri- ously impacted primary produ
