It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorolog...It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorological stations of the Pearl River Basin,the Standardized Precipitation Evapotranspiration Index（ SPEI） at different time scales was calculated. Based on the SPEIs of 1- 12 months,a newly proposed index for drought--Joint Drought Index（ JDI） was established under the multi-scale perspective through the copula function. Since short-term SPEIs are essential for the identification of emerging droughts and long-term SPEIs are useful for prolonged droughts,the JDI,which integrates all the usefull informations of drought and can thus form an overall judgement,is superior than the single SPEI in drought monitoring. By the forcast evaluation system and comparison to the actual drought,the accuracy and effectiveness of JDI in drought monitoring were verified. In general,JDI can be used as a new ideal index for future drought monitoring and assessment. Additionly,we analyzed the spatio-temperal characteristics of drought across the Pearl River Basin using the JDI. The results indicate that mild drought was the most frequent drought occurred in the Pearl River Basin over the past half century,and moderate drought followed. Severe drought and extreme drought would appear occasionally while exceptional drought could hardly be found. A dry-wet-dry interdecadal variation pattern had been found from the 1960 s to the 2000 s. Since the 21 stcentury,an obvious trend toward drought can be observed in the whole basin,especially in the Xijiang subbasin,which,consequently,poses an increasing challenge for the water resource planning and management.展开更多
Based on TM images,ArcGIS and landscape ecology,4 typical roads in the Pearl River Delta are taken for example to analyze infl uence range of highway,and study the laws of highway construction infl uencing landscape p...Based on TM images,ArcGIS and landscape ecology,4 typical roads in the Pearl River Delta are taken for example to analyze infl uence range of highway,and study the laws of highway construction infl uencing landscape patterns by reviewing landscape pattern changes in areas along the highways. According to the research,for Yuebei Section(north Guangdong) of Beijing–Zhuhai Highway,road construction has signifi cant infl uence on landscape patterns of the 300-m wide buffer zone(especially woodland and urban land); for Foshan–Kaiping Highway,road construction has significant influence on landscape patterns of the 1,000-m wide buffer zone(especially woodland and agricultural land); for Dongguan–Shenzhen Highway,road construction has signifi cant infl uence on landscape patterns of the 8,000-m wide buffer zone(especially woodland and urban land).展开更多
Ever since the introduction of the Open Door Policy, the Pearl River Delta (PRD) has enjoyed very phenomenal export and economic growth. As a result, many scholars have tried to associate the two phenomena and describ...Ever since the introduction of the Open Door Policy, the Pearl River Delta (PRD) has enjoyed very phenomenal export and economic growth. As a result, many scholars have tried to associate the two phenomena and described the region as an,'export-oriented economy'.However, these studies, mostly based on the rapid export growth of the PRD and its status as the most important exporting area of the country,have not paid any heed to the actual export-orientation of the regional economy and, hence, cannot prove that the PRD has been a 'truly'export-oriented economy. in view of these shortcomings. the present paper attempts to re-examine the issue from the viewpoint of the PRD's local economy, at both the regional and county levels. The study period is from 1981 to 1990. Judging from the export-dependency indices and the relative importance of exports in accounting for the economic growth and industrialization of the PRD, this paper concludes that the region, though having signs of increasing export-orientation, cannot be categorized as a 'truly' export-oriented economy. In addition, it also shows that most of the 'evidences' or 'common beliefs' behind the notion of an export-oriented economy in the RD are illusionary, if not erroneous. Finally, the paper explores into the reasons behind the low export-orientation of the PRD and tries to sugyst some ways for boosting the export-orientation of the PRD and tries to suggest some ways for boosting the export-orientation of the region.展开更多
The present investigation was aimed to understand the physiological and biochemical basis of water-deficit stress tolerance in pearl millet [Pennisetum glaucum (L.) R. Br.] hybrid ICMH 356 and its parents ICMR 356 (♂...The present investigation was aimed to understand the physiological and biochemical basis of water-deficit stress tolerance in pearl millet [Pennisetum glaucum (L.) R. Br.] hybrid ICMH 356 and its parents ICMR 356 (♂) and ICMB 88004 (♀) in response to and recovery from drought stress and also to comprehend crop adaptation under dryland conditions. A field experiment was conducted in a split plot design with moisture levels as the main plot and genotypes as the sub plots. A comparative analysis of hybrid and parents under well-watered and water-deficit stress conditions revealed that the hybrid was superior over the parents in terms of leaf water relations, excised leaf water retention capacity, accumulation of compatible solutes, photosynthesis, membrane stability index and antioxidative enzyme viz., superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) activities. ANOVA for these parameters was also found to be significant for genotypes, treatments and their interactions at 0.01% level. Maintenance of superiority in terms of these physiological and biochemical parameters coupled with better recovery ability upon stress relief are crucial physiological mechanisms contributing to water deficit stress tolerance in pearl millet. Simple correlation coefficient analysis revealed significant positive association of yield at 0.01% level with relative water content, leaf water potential, stomatal conductance, photosynthesis, proline, total soluble sugars, free amino acids, membrane stability index, leaf area index and total biomass, while a significant negative association with solute potential and malondialdehyde content, under water-deficit stress clearly indicated that such relationships can be positively attributed to drought tolerance.展开更多
A macro scale survey was performed to investigate the content of soil available nitrogen (N) and its spatial distribution in the main vegetable production areas of the Pearl River Delta.Preliminary enrichment-deficien...A macro scale survey was performed to investigate the content of soil available nitrogen (N) and its spatial distribution in the main vegetable production areas of the Pearl River Delta.Preliminary enrichment-deficient index of available N was then developed,which was a base for increasing fertilizer application efficiency and vegetable yield as well as for constructing soil testing and fertilizing formula.In general,most of the vegetable growth areas in Pearl River Delta were N-deficient or medium-N-deficient.There was 30%-62% increase in yield of Chinese cabbage on the N-deficient soil after application of N; when soil available N content was less than 145 mg/kg,the yield increased with application of N fertilizer at a rate of 60-70 kg/hm2.展开更多
基金Supported by National Natural Science Foundation,China(41371498)Comprehensive Process Observation and Test Platform Construction of Natural Geography in Marina Small Watershed,Sun Yat-sen University,China
文摘It is accepted that climate change has a great impact on water cycle and regional water balance,and thus it would change the formation and evolution conditions of drought in some degree. By using data at 42 meteorological stations of the Pearl River Basin,the Standardized Precipitation Evapotranspiration Index（ SPEI） at different time scales was calculated. Based on the SPEIs of 1- 12 months,a newly proposed index for drought--Joint Drought Index（ JDI） was established under the multi-scale perspective through the copula function. Since short-term SPEIs are essential for the identification of emerging droughts and long-term SPEIs are useful for prolonged droughts,the JDI,which integrates all the usefull informations of drought and can thus form an overall judgement,is superior than the single SPEI in drought monitoring. By the forcast evaluation system and comparison to the actual drought,the accuracy and effectiveness of JDI in drought monitoring were verified. In general,JDI can be used as a new ideal index for future drought monitoring and assessment. Additionly,we analyzed the spatio-temperal characteristics of drought across the Pearl River Basin using the JDI. The results indicate that mild drought was the most frequent drought occurred in the Pearl River Basin over the past half century,and moderate drought followed. Severe drought and extreme drought would appear occasionally while exceptional drought could hardly be found. A dry-wet-dry interdecadal variation pattern had been found from the 1960 s to the 2000 s. Since the 21 stcentury,an obvious trend toward drought can be observed in the whole basin,especially in the Xijiang subbasin,which,consequently,poses an increasing challenge for the water resource planning and management.
文摘Based on TM images,ArcGIS and landscape ecology,4 typical roads in the Pearl River Delta are taken for example to analyze infl uence range of highway,and study the laws of highway construction infl uencing landscape patterns by reviewing landscape pattern changes in areas along the highways. According to the research,for Yuebei Section(north Guangdong) of Beijing–Zhuhai Highway,road construction has signifi cant infl uence on landscape patterns of the 300-m wide buffer zone(especially woodland and urban land); for Foshan–Kaiping Highway,road construction has significant influence on landscape patterns of the 1,000-m wide buffer zone(especially woodland and agricultural land); for Dongguan–Shenzhen Highway,road construction has signifi cant infl uence on landscape patterns of the 8,000-m wide buffer zone(especially woodland and urban land).
文摘Ever since the introduction of the Open Door Policy, the Pearl River Delta (PRD) has enjoyed very phenomenal export and economic growth. As a result, many scholars have tried to associate the two phenomena and described the region as an,'export-oriented economy'.However, these studies, mostly based on the rapid export growth of the PRD and its status as the most important exporting area of the country,have not paid any heed to the actual export-orientation of the regional economy and, hence, cannot prove that the PRD has been a 'truly'export-oriented economy. in view of these shortcomings. the present paper attempts to re-examine the issue from the viewpoint of the PRD's local economy, at both the regional and county levels. The study period is from 1981 to 1990. Judging from the export-dependency indices and the relative importance of exports in accounting for the economic growth and industrialization of the PRD, this paper concludes that the region, though having signs of increasing export-orientation, cannot be categorized as a 'truly' export-oriented economy. In addition, it also shows that most of the 'evidences' or 'common beliefs' behind the notion of an export-oriented economy in the RD are illusionary, if not erroneous. Finally, the paper explores into the reasons behind the low export-orientation of the PRD and tries to sugyst some ways for boosting the export-orientation of the PRD and tries to suggest some ways for boosting the export-orientation of the region.
文摘The present investigation was aimed to understand the physiological and biochemical basis of water-deficit stress tolerance in pearl millet [Pennisetum glaucum (L.) R. Br.] hybrid ICMH 356 and its parents ICMR 356 (♂) and ICMB 88004 (♀) in response to and recovery from drought stress and also to comprehend crop adaptation under dryland conditions. A field experiment was conducted in a split plot design with moisture levels as the main plot and genotypes as the sub plots. A comparative analysis of hybrid and parents under well-watered and water-deficit stress conditions revealed that the hybrid was superior over the parents in terms of leaf water relations, excised leaf water retention capacity, accumulation of compatible solutes, photosynthesis, membrane stability index and antioxidative enzyme viz., superoxide dismutase (SOD), catalase (CAT), glutathione reductase (GR), ascorbate peroxidase (APX) and guaiacol peroxidase (GPOX) activities. ANOVA for these parameters was also found to be significant for genotypes, treatments and their interactions at 0.01% level. Maintenance of superiority in terms of these physiological and biochemical parameters coupled with better recovery ability upon stress relief are crucial physiological mechanisms contributing to water deficit stress tolerance in pearl millet. Simple correlation coefficient analysis revealed significant positive association of yield at 0.01% level with relative water content, leaf water potential, stomatal conductance, photosynthesis, proline, total soluble sugars, free amino acids, membrane stability index, leaf area index and total biomass, while a significant negative association with solute potential and malondialdehyde content, under water-deficit stress clearly indicated that such relationships can be positively attributed to drought tolerance.
基金supported by the Special Financial Support Program on Agriculture Research of Public Welfare Industry (Grant No. nyhyzx07-007-6)Special Fund for the Guangdong Modern Agriculture Industrial System Construction(Guangdong Agriculture 2009-380)+2 种基金Guangdong Agriculture Brainstorm Project ( Grant No. 2008B021000045, 2009B 020202003)the National Science and Technology Support Program (Grant No.2007BAD89B14)Agriculture Brainstorm Project of Panyu District, Guangzhou, Guangdong province(Grant No.2010-Z-82-1)
文摘A macro scale survey was performed to investigate the content of soil available nitrogen (N) and its spatial distribution in the main vegetable production areas of the Pearl River Delta.Preliminary enrichment-deficient index of available N was then developed,which was a base for increasing fertilizer application efficiency and vegetable yield as well as for constructing soil testing and fertilizing formula.In general,most of the vegetable growth areas in Pearl River Delta were N-deficient or medium-N-deficient.There was 30%-62% increase in yield of Chinese cabbage on the N-deficient soil after application of N; when soil available N content was less than 145 mg/kg,the yield increased with application of N fertilizer at a rate of 60-70 kg/hm2.
