[Objective] The research aimed to analyze the disastrous weather of serious drought in Northwest Hunan in summer and autumn of 2009.[Method] According to the meteorological data in Zhangjiajie of Northwest Hunan durin...[Objective] The research aimed to analyze the disastrous weather of serious drought in Northwest Hunan in summer and autumn of 2009.[Method] According to the meteorological data in Zhangjiajie of Northwest Hunan during the drought period from June to September,2009,the disaster characteristics of continuous drought in summer and autumn were analyzed.Based on NCEP/NCAR 2.5°×2.5° reanalysis data,by using the climatic diagnostic method,the formation reason of serious drought was initially analyzed from the circulation characteristics in the middle and high latitudes,Western Pacific subtropical high,the abnormal characteristics of sea surface temperature in the equatorial Middle Eastern Pacific Ocean and the tropical system activity.[Result] The characteristics of serious drought in Northwest Hunan in summer and autumn of 2009 were the quick developed speed,wide influence range,long duration,big disaster loss and long high temperature time.The influence range,duration and harm degree were rare to see in the history.During the arid period(June-September),the atmospheric circulation was abnormal.The polar vortex in the northern hemisphere was weak,and the center was by north.It was two-trough-one-ridge type in the middle and high latitudes of Eurasia.The long-wave trough existed respectively near Balkhash Lake and from Sea of Okhotsk to the east coast in China.The long-wave ridge maintained from Lake Baikal to Central Asia and stabilized in 90°-110° E of Central Asia.From the middle dekad of June to the middle dekad of September,the westerly index increased.The zonal circulation was the main one in the middle and high latitudes of Eurasia.The cold air in the high-latitude frontal zone spread eastward with the small-amplitude fluctuation form along the latitude circle direction,and was difficult to pass the westerly barrier near 45° N to reach the low latitude.Meanwhile,Western Pacific subtropical high jumped northward to control Jiangnan and South China for a long time.The down airflow was prevalent.It was hot and rainless.The drought developed quickly.The sea surface temperature in the equatorial Middle Eastern Pacific Ocean started to rise in June,and it entered into El Nino state.When El Nino event of obvious temperature increasing started to appear in spring and summer,the plum rain amount was less in the middle and low reaches of Yangtze River in the year or next year.The probability was 80%.In El Nino year,the typhoon was less.In addition,for the influence of strong Western Pacific subtropical high,the landing pathway of typhoon was by east or south.The kind of typhoon had the small role for easing the drought in Northwest Hunan.[Conclusion] The research provided the theory basis for improving the prediction level of short-term climate and the understanding of extreme climate event.展开更多
Background:Fagus sylvatica forms the treeline across the Apennines mountain range,with an average elevation of 1589 ma.s.l.Previous studies evidenced that the current position of the treeline in the Apennines is heavi...Background:Fagus sylvatica forms the treeline across the Apennines mountain range,with an average elevation of 1589 ma.s.l.Previous studies evidenced that the current position of the treeline in the Apennines is heavily depressed as a result of a complex interaction between climatic factors and the past human pressure.In this study we correlated treeline elevation in the fifteen major mountain groups in the Apennines with selected climatic,geomorphological,and human disturbance variables in order to investigate in detail the site-specific features affecting the current treeline distribution.Results:Treeline elevation was lowest in the North Italy(Apuan Alps),while the highest treeline was found in Central Italy(Simbruini).An absolute maximum treeline elevation of F.sylvatica exceeding 2000ma.s.l.was found on 13 mountain peaks in Central and Southern Italy.Noteworthy,treeline elevation was largely lower on warmer south-facing slopes compared to northern slopes,with values several hundred meters lower in the Gran Sasso and Velino-Sirente.Although the causes of this pattern are still unknown,we argue that treeline elevation on southfacing slopes may be limited by the combination of climatic constraints(i.e.summer drought)and human disturbance.Evidence of a pervasive anthropogenic effect depressing treeline elevation was found in the North(Apuan Alps)Central(Gran Sasso,Velino-Sirente,Sibillini)and Southern part of Apennines(Pollino).By contrast,treeline elevation of the Laga,Simbruini,and Orsomarso mountain groups appears less affected by past anthropogenic disturbance.Finally,we recorded in the several mountain groups(i.e.Majella,Marsicani and Pollino)the coexistence of very depressed treelines just a few kilometers away from much higher treelines,among the highest ever recorded for F.sylvatica.Conclusions:Finally,we argue that F.sylvatica treeline across the Apennines is locally shaped both by the interaction of low temperatures experienced by the species in its earliest life stages in snow-free open spaces with summer soil water depletion and human disturbance.展开更多
Based on the daily data of temperature and precipitation of 108 meteorological stations in Southwest China from 1960 to 2009, we calculate the monthly and yearly surface humid indexes, as well as the extreme drought f...Based on the daily data of temperature and precipitation of 108 meteorological stations in Southwest China from 1960 to 2009, we calculate the monthly and yearly surface humid indexes, as well as the extreme drought frequency. According to the data, the temporal and spatial characteristics of the extreme drought frequency in inter-annual, inter-decadal, summer monsoon period and winter monsoon period are analyzed. The results are indicated as follows. （1） In general, the southwestern Sichuan Basin, southern Hengduan Mountains, southern coast of Guangxi and northern Guizhou are the areas where the extreme drought frequency has significantly increased in the past 50 years. As for the decadal change, from the 1960s to the 1980s the extreme drought frequency has presented a decreasing trend, while the 1990s is the wettest decade and the whole area is turning wet. In the 2000s, the extreme drought frequency rises quickly, but the regional differences reduce. （2） During summer monsoon period, the extreme drought frequency is growing, which generally occurs in the high mountains around the Sichuan Basin, most parts of Guangxi and ＂the broom-shaped mountains＂ in Yunnan. It is distinct that the altitude has impacts on the ex- treme drought frequency; during winter monsoon period, the area is relatively wet and the extreme drought frequency is decreasing. （3） During summer monsoon period, the abrupt change is observed in 2003, whereas the abrupt change during winter monsoon period is in 1989. The annual extreme drought frequency variation is a superposition of abrupt changes during summer monsoon and winter monsoon periods. The departure sequence vibration of annual extreme drought frequency is quasi-5 years and quasi-12 years.展开更多
【目的】保护性耕作有利于水土保持和提高土壤有机碳库,而对氮素氨挥发的影响并不是很清楚。研究长期定位试验下华北农田施肥后氨挥发发生规律,探索保护性耕作条件下的氮素利用率。【方法】采用间歇动态箱式法对翻耕、旋耕和免耕3种耕...【目的】保护性耕作有利于水土保持和提高土壤有机碳库,而对氮素氨挥发的影响并不是很清楚。研究长期定位试验下华北农田施肥后氨挥发发生规律,探索保护性耕作条件下的氮素利用率。【方法】采用间歇动态箱式法对翻耕、旋耕和免耕3种耕作方式下冬小麦-夏玉米农田氨挥发通量及其影响因素进行比较研究。【结果】相对于翻耕和旋耕处理,免耕显著促进了小麦季和玉米季地表追肥的氨挥发,但显著降低了小麦基肥期的氨挥发速率。翻耕、旋耕和免耕下小麦-玉米全生育期氨挥发损失量为15.8、18.4和28.6 kg hm-2 a-1,分别占施肥量的4.9%、5.7%和8.8%。实验室培养分析表明,免耕和旋耕显著提高了表层(0—5 cm)土壤脲酶活性,加速尿素水解为NH4+,从而促进氨挥发。【结论】免耕条件下,肥料表施易发生氨挥发,采用一次性深施是减少免耕氨挥发的有效途径之一。展开更多
文摘[Objective] The research aimed to analyze the disastrous weather of serious drought in Northwest Hunan in summer and autumn of 2009.[Method] According to the meteorological data in Zhangjiajie of Northwest Hunan during the drought period from June to September,2009,the disaster characteristics of continuous drought in summer and autumn were analyzed.Based on NCEP/NCAR 2.5°×2.5° reanalysis data,by using the climatic diagnostic method,the formation reason of serious drought was initially analyzed from the circulation characteristics in the middle and high latitudes,Western Pacific subtropical high,the abnormal characteristics of sea surface temperature in the equatorial Middle Eastern Pacific Ocean and the tropical system activity.[Result] The characteristics of serious drought in Northwest Hunan in summer and autumn of 2009 were the quick developed speed,wide influence range,long duration,big disaster loss and long high temperature time.The influence range,duration and harm degree were rare to see in the history.During the arid period(June-September),the atmospheric circulation was abnormal.The polar vortex in the northern hemisphere was weak,and the center was by north.It was two-trough-one-ridge type in the middle and high latitudes of Eurasia.The long-wave trough existed respectively near Balkhash Lake and from Sea of Okhotsk to the east coast in China.The long-wave ridge maintained from Lake Baikal to Central Asia and stabilized in 90°-110° E of Central Asia.From the middle dekad of June to the middle dekad of September,the westerly index increased.The zonal circulation was the main one in the middle and high latitudes of Eurasia.The cold air in the high-latitude frontal zone spread eastward with the small-amplitude fluctuation form along the latitude circle direction,and was difficult to pass the westerly barrier near 45° N to reach the low latitude.Meanwhile,Western Pacific subtropical high jumped northward to control Jiangnan and South China for a long time.The down airflow was prevalent.It was hot and rainless.The drought developed quickly.The sea surface temperature in the equatorial Middle Eastern Pacific Ocean started to rise in June,and it entered into El Nino state.When El Nino event of obvious temperature increasing started to appear in spring and summer,the plum rain amount was less in the middle and low reaches of Yangtze River in the year or next year.The probability was 80%.In El Nino year,the typhoon was less.In addition,for the influence of strong Western Pacific subtropical high,the landing pathway of typhoon was by east or south.The kind of typhoon had the small role for easing the drought in Northwest Hunan.[Conclusion] The research provided the theory basis for improving the prediction level of short-term climate and the understanding of extreme climate event.
基金partially supported by the Ph D programme at the ‘School of Agricultural and Food Sciences’ granted to VM and MZ, in the Department of Agricultural Sciences, University of Naples Federico Ⅱ.
文摘Background:Fagus sylvatica forms the treeline across the Apennines mountain range,with an average elevation of 1589 ma.s.l.Previous studies evidenced that the current position of the treeline in the Apennines is heavily depressed as a result of a complex interaction between climatic factors and the past human pressure.In this study we correlated treeline elevation in the fifteen major mountain groups in the Apennines with selected climatic,geomorphological,and human disturbance variables in order to investigate in detail the site-specific features affecting the current treeline distribution.Results:Treeline elevation was lowest in the North Italy(Apuan Alps),while the highest treeline was found in Central Italy(Simbruini).An absolute maximum treeline elevation of F.sylvatica exceeding 2000ma.s.l.was found on 13 mountain peaks in Central and Southern Italy.Noteworthy,treeline elevation was largely lower on warmer south-facing slopes compared to northern slopes,with values several hundred meters lower in the Gran Sasso and Velino-Sirente.Although the causes of this pattern are still unknown,we argue that treeline elevation on southfacing slopes may be limited by the combination of climatic constraints(i.e.summer drought)and human disturbance.Evidence of a pervasive anthropogenic effect depressing treeline elevation was found in the North(Apuan Alps)Central(Gran Sasso,Velino-Sirente,Sibillini)and Southern part of Apennines(Pollino).By contrast,treeline elevation of the Laga,Simbruini,and Orsomarso mountain groups appears less affected by past anthropogenic disturbance.Finally,we recorded in the several mountain groups(i.e.Majella,Marsicani and Pollino)the coexistence of very depressed treelines just a few kilometers away from much higher treelines,among the highest ever recorded for F.sylvatica.Conclusions:Finally,we argue that F.sylvatica treeline across the Apennines is locally shaped both by the interaction of low temperatures experienced by the species in its earliest life stages in snow-free open spaces with summer soil water depletion and human disturbance.
基金National Natural Science Foundation of China,No.41161012，Program for New Century Excellent Talents in University from the Ministry of Education of China,No.NCET-10-0019，Basic Scientific Research Foundation in University of Gansu Province
文摘Based on the daily data of temperature and precipitation of 108 meteorological stations in Southwest China from 1960 to 2009, we calculate the monthly and yearly surface humid indexes, as well as the extreme drought frequency. According to the data, the temporal and spatial characteristics of the extreme drought frequency in inter-annual, inter-decadal, summer monsoon period and winter monsoon period are analyzed. The results are indicated as follows. （1） In general, the southwestern Sichuan Basin, southern Hengduan Mountains, southern coast of Guangxi and northern Guizhou are the areas where the extreme drought frequency has significantly increased in the past 50 years. As for the decadal change, from the 1960s to the 1980s the extreme drought frequency has presented a decreasing trend, while the 1990s is the wettest decade and the whole area is turning wet. In the 2000s, the extreme drought frequency rises quickly, but the regional differences reduce. （2） During summer monsoon period, the extreme drought frequency is growing, which generally occurs in the high mountains around the Sichuan Basin, most parts of Guangxi and ＂the broom-shaped mountains＂ in Yunnan. It is distinct that the altitude has impacts on the ex- treme drought frequency; during winter monsoon period, the area is relatively wet and the extreme drought frequency is decreasing. （3） During summer monsoon period, the abrupt change is observed in 2003, whereas the abrupt change during winter monsoon period is in 1989. The annual extreme drought frequency variation is a superposition of abrupt changes during summer monsoon and winter monsoon periods. The departure sequence vibration of annual extreme drought frequency is quasi-5 years and quasi-12 years.
文摘【目的】保护性耕作有利于水土保持和提高土壤有机碳库,而对氮素氨挥发的影响并不是很清楚。研究长期定位试验下华北农田施肥后氨挥发发生规律,探索保护性耕作条件下的氮素利用率。【方法】采用间歇动态箱式法对翻耕、旋耕和免耕3种耕作方式下冬小麦-夏玉米农田氨挥发通量及其影响因素进行比较研究。【结果】相对于翻耕和旋耕处理,免耕显著促进了小麦季和玉米季地表追肥的氨挥发,但显著降低了小麦基肥期的氨挥发速率。翻耕、旋耕和免耕下小麦-玉米全生育期氨挥发损失量为15.8、18.4和28.6 kg hm-2 a-1,分别占施肥量的4.9%、5.7%和8.8%。实验室培养分析表明,免耕和旋耕显著提高了表层(0—5 cm)土壤脲酶活性,加速尿素水解为NH4+,从而促进氨挥发。【结论】免耕条件下,肥料表施易发生氨挥发,采用一次性深施是减少免耕氨挥发的有效途径之一。
