Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we cl...Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we clarify P.forrestii community types,structure,species diversity,seedling recruitments and growth trends.We identified four P.forrestii community types:(1)Pseudotsuga forrestii-Quercus guyavifolia-Acer davidii evergreen coniferous and broad-leaved mixed forest;(2)Pseudotsuga forrestii-Pinus yunnanensis-Quercus guyavifolia evergreen coniferous and broad-leaved mixed forest;(3)Pseudotsuga forrestii evergreen coniferous forest;(4)Pseudotsuga forrestii-Abies georgei var.smithii evergreen coniferous forest.P.forrestii forests are characterized by both warm temperate and temperate affinities.Simpson diversity,Pielou evenness,Shannon-Wiener diversity indices ranged from 0.75 to 0.76,0.74-0.81,and 1.62-1.93,respectively,with no significant differences among the four forest types.The forest stratification was multilayered.The canopy layer was generally 10-25 m tall,with the emergent layer reached 25-42 m.DBH and age structures of P.forrestii showed multimodal distributions.Its maximum age P.forrestii was 570 years with a DBH of 143 cm.The growth of annual ring width of P.forrestii was slow,and generally decreased with age,whereas the basal area at the breast height increased with age.Established seedlings/saplings were mainly found in unstable micro-habitats.Regeneration of P.forrestii depends on moderate natural disturbances.Finally,we provide recommendations for P.forrestii conservation.展开更多
In mountain ecosystems,plants are sensitive to climate changes,and an entire range of species distribution can be observed in a small area.Therefore,mountains are of great interest for climate–growth relationship ana...In mountain ecosystems,plants are sensitive to climate changes,and an entire range of species distribution can be observed in a small area.Therefore,mountains are of great interest for climate–growth relationship analysis.In this study,the Siberian spruce’s(Picea obovata Ledeb.)radial growth and its climatic response were investigated in the Western Sayan Mountains,near the SayanoShushenskoe Reservoir.Sampling was performed at three sites along an elevational gradient:at the lower border of the species range,in the middle,and at the treeline.Divergence of growth trends between individual trees was observed at each site,with microsite landscape-soil conditions as the most probable driver of this phenomenon.Cluster analysis of individual tree-ring width series based on inter-serial correlation was carried out,resulting in two sub-set chronologies being developed for each site.These chronologies appear to have substantial differences in their climatic responses,mainly during the cold season.This response was not constant due to regional climatic change and the local influence of the nearby Sayano-Shushenskoe Reservoir.The main response of spruce to growing season conditions has a typical elevational pattern expected in mountains:impact of temperature shifts with elevation from positive to negative,and impact of precipitation shifts in the opposite direction.Chronologies of trees,growing under more severe micro-conditions,are very sensitive to temperature during September–April and to precipitation during October–December,and they record both inter-annual and long-term climatic variation.Consequently,it would be interesting to test if they indicate the Siberian High anticyclone,which is the main driver of these climatic factors.展开更多
The paper analyzed the growth level and velocity to find the growth trend with the data collected in 8 investigations on growth of children aged 7～17 years in 1958～1995 in Xi′an. The results showed that child′s gr...The paper analyzed the growth level and velocity to find the growth trend with the data collected in 8 investigations on growth of children aged 7～17 years in 1958～1995 in Xi′an. The results showed that child′s growth level was elevated with the passage of years and was the lowest in 1962, the highest in 1995 during the 38 years. The height of boy of the same age in 1995 has average increased by 9 59 cm over 1958 and girl 8 38 cm. The weight of boy of the same age in 1995 has averagely increased by 8 35 kg over 1958 and girl 5 90 kg. The chest girth of boy of the same age in 1995 has average increased by 5 69 cm over 1958 and girl 4 66 cm. The growth level of children aged 9～15 years had greater increase than others in 7～17 years of age. The average increment per 10 years of boy's height was 2 57 cm and girl's 2 26 cm. The average increment of per 10 years of boy's weight was 2 17 kg and girl's 1 56 kg. The average increment of per 10 years of boy's chest girth was 1 50 cm and girl's 1 23 cm. The analysis of the growth velocity in different period during 38 years showed the velocity in 1958～1962 was a negative value and indicated a growth retard, but the velocity in 1962～1964 was the fastest and indicated a catch up growth. And then, growth velocities of height, weight and chest girth were different in different period. The analysis of the growth curves of height, weight and chest girth showed that the 2 cross ages were 1～3 years of age ahead of time and menarche and emission also were ahead of time that during the 38 years indicated there is a child's growth acceleration in Xi′an and the trend of child's growth acceleration could continue if there are more and better nourishment, sports requisites, health care and housing conditions.展开更多
The growth of the world economy in 2001 featured significant slowdowns, with various developed countries plunging into economic recessions or economic downturns synchronously. Against this context, China was able to m...The growth of the world economy in 2001 featured significant slowdowns, with various developed countries plunging into economic recessions or economic downturns synchronously. Against this context, China was able to maintain a 7.3 percent growth. A simple direct comparison of economic growth of all countries shows that China outshone all the others.展开更多
China＇s cormaaunications industry is an important part of the electronic information industry, and plays a significant role in the national informatization process. In 2006, China issued its National Plans for Medium...China＇s cormaaunications industry is an important part of the electronic information industry, and plays a significant role in the national informatization process. In 2006, China issued its National Plans for Medium and Long-term Development of Science and Technology （2006-2020） （NPMLDST）. Since 2006, there has been a rapid increase in the number of citations of China＇s interna- tional papers in the field of communications. In accordance with the goals listed in the NPMLDST, China needs to over- take several competitors by 2020 to be among the top five countries in the field of natural science field. By comparing two Essential Science Indicators （ESI） （i.e., the total number of citations and the number of citations per paper） for China and other countries, China＇s annual growth rate is found to exceed that of other influential countries in the field of sci- ence and technology, and exhibits evident growth-type characteristics. Besides, our study also shows that the short- age of high-quality academic papers in China is the main obstacle to improving the impact of China＇s academic publications.展开更多
2025 has seen impressive growth in new business jet deliveries to date;is this trend likely to continue?In terms of new production,the helicopter and business sectors look to be entering growth mode once again,leaving...2025 has seen impressive growth in new business jet deliveries to date;is this trend likely to continue?In terms of new production,the helicopter and business sectors look to be entering growth mode once again,leaving supply chain woes behind us.For business jets,we believe some 8,700 new aircraft will be handed over in the following 10 years(2025-2034).This is driven by an 11%climb this year alone,driven by new types and product ramp-ups.The following analysis discusses this,and concludes with some thoughts on forecast risks.展开更多
We assessed growth traits and wood properties ofDH32-29, a clone of Eucalyptus urophylla x E. grandis, at age of two to six years in Guangdong in China. Analysis of variance of studied traits showed that there were si...We assessed growth traits and wood properties ofDH32-29, a clone of Eucalyptus urophylla x E. grandis, at age of two to six years in Guangdong in China. Analysis of variance of studied traits showed that there were significant differences （1% level） on all studied traits among ages except for wood basic density. Analysis of age trends of growth traits and wood properties revealed that rotation length of DH32-29 should be more than six years or longer. Phenotypic correlations among traits at individual ages indicated that correlations between growth traits were strongly positive. There was significant change in relationship between growth and wood basic density with increasing age, ranging from -0.03 to -0.54 at 2 and 5 year and 0.003 to 0.3 at 3, 4 and 6 year. Correlations between Pilodyn pin penetration and basic density measured on increment cores showed that Pilodyn could rank or group genotypes or sites into density classes, but failure to predict individual tree and individual clone.展开更多
The growing conditions of urban trees differ substantially from forest sites and are mainly characterized by small planting pits with less water, nutrient and aeration availability, high temperatures and radiation inp...The growing conditions of urban trees differ substantially from forest sites and are mainly characterized by small planting pits with less water, nutrient and aeration availability, high temperatures and radiation inputs as well as pollution and soil compaction. Especially, global warming can amplify the negative effects of urban microclimates on tree growth, health and well-being of citizens. To quantify the growth of urban trees influenced by the urban climate, ten urban tree species in four climate zones were assessed in an overarching worldwide dendrochronological study. The focus of this analysis was the species water oak (Quercus nigra L.) in Houston, Texas, USA. Similar to the overall growth trend, we found in urban trees, water oaks displayed an accelerated growth during the last decades. Moreover, water oaks in the city center grew better than the water oaks growing in the rural surroundings of Houston, though this trend was reversed with high age. Growth habitat (urban, suburban, rural and forest) significantly affected tree growth (p < 0.001) with urban trees growing faster than rural growing trees and forest trees, though a younger age of urban trees might influence the found growth patterns. Growing site in terms of cardinal direction did not markedly influence tree growth, which was more influenced by the prevalent climatic conditions of Houston and the urban climate. Higher temperatures, an extended growing season and eutrophication can cause an accelerated growth of trees in urban regions across, across all climatic zones. However, an accelerated growth rate can have negative consequences like quicker ageing and tree death resulting in higher costs for new plantings and tree management as well as the decrease in ecosystem services due to a lack of old trees providing greatest benefits for mitigating the negative effects of the urban climate.展开更多
Objective To describe secular trends on physical growth of children in China during the year of 1985‐2005 and to analyze the urban‐suburban‐rural difference and its change. Methods The measurements of height, weigh...Objective To describe secular trends on physical growth of children in China during the year of 1985‐2005 and to analyze the urban‐suburban‐rural difference and its change. Methods The measurements of height, weight and chest circumference obtained from two serial national cross‐sectional surveys for children aged 0 to 7 years in China were used to analyze the secular trends, and the growth differences among urban, suburban and rural children were compared. Results The average weight and height for both boys and girls from urban, suburban and rural areas have significantly increased in most age groups during the past 20 years; The average chest circumference increased slightly, ranging from 0.0 to 2.0 cm. From 1985 to 2005, the urban‐suburban difference in height had become smaller, and that in weight showed similar trend for children under 3 years old but became larger after 3 years old; the suburban‐rural difference both in height and weight became larger after 6 months old. The increment per decade in height was the greatest in the suburban group while the greatest increment in weight was the urban group. Conclusion Positive secular trends were observed among urban, suburban and rural areas in Chinese children under 7 years old during the 1980s and the 2000s, reflecting a rapid socio‐economic development in China.展开更多
[Objective] The aim was to study change tendency of the precipitation resource during growth period of the conventional crops in plain area before Taihang Mountains. [ Method] Based on daily precipitation data at Shij...[Objective] The aim was to study change tendency of the precipitation resource during growth period of the conventional crops in plain area before Taihang Mountains. [ Method] Based on daily precipitation data at Shijiazhuang meteorological station in recent 51 years, average rainfall dudng growth periods of the 9 kinds of conventional crops was obtained. Precipitation tendency dudng growth periods of the 9 kinds of conventional crops in plain area before Taihang Mountains was analyzed by Mann-Kendall nonparametric test. [ Result] Seen from rainfall during growth pedods of the different crops, rainfall was the least during the growth period of winter wheat, followed by summer corn. Rainfall during growth peri- ods of the cotton, oil plant, vegetable, fruit tree, potato, rice and legumes was more. Under different guaranteed rates, precipitation change also had difference. Rainfall change during growth periods of the wheat and corn was bigger, and rainfall change during growth period of the rice was smaller. Change degree of the precipitation during growth periods of the cotton, oil plant, vegetable, fruit tree and legumes was equivalent, while precipitation change during growth period of the potato was the biggest. Seen from change tendency of the precipitation during growth periods of the different crops, precipitation in the growth period of winter wheat was increasing at a speed of 0.62 mm/a. However, precipitation in growth periods of the other crops had a decreasing tendency. Precipitation in the growth periods of summer corn and legumes decreased at the same speed which was 2.11 mm/a, while precipitation in growth periods of the cotton, oil plant, vegetable, fruit tree, potato and rice decreased insignificantly. [ Con dusion] The study laid foundation for determination of the agricultural irrigation water and provided theoretical reference for regional agricultural water-saving.展开更多
This research assessed empirically the quantitative analysis of some selected food imports of Nigeria (rice, wheat and sugar). Time series data were used to examine the determinant of total food imports and the trend ...This research assessed empirically the quantitative analysis of some selected food imports of Nigeria (rice, wheat and sugar). Time series data were used to examine the determinant of total food imports and the trend in the quantity of the food imported. The secondary data were obtained from institutional and national database over 1981-2010. Descriptive statistics, regression and correlation analysis were used as analytical tools. Statistical analysis shows that food deficit began in the 1970’s, when Nigeria started the importation of food to feed the country. The result of the correlation analysis shows that the postulated determinants of food imports were positively correlated with the quantity of food import. The test for the individual variables shows that;national income explains 40%, external reserves explains 38%, food production index explains 46%, population explains 58% and exchange rate explains 74% of the total variation in the quantity of food import. The over-all goodness of fit of the regression analysis result shows that, the postulated regressors namely, relative price, national income, external reserves, lagged index of domestic food production, population estimate and exchange rate explained approximately 70% of the variability in the quantity of the selected food imports for the period of study. Consequently, there is the need for Nigeria to shift base from the ideology of nationalist orientation, as well as afro centric point of view and move towards unrestrained export-led growth that seeks to develop that market as the first option with corresponding development in international trade. This is however possible by limiting the importation of foods/raw materials that can be sourced for locally, increasing the domestic production of food generally and maintaining a healthy foreign investment with developed countries as a short term measure while in the long run, diversification of the economy, massive investment in agriculture and introduction of population control measures could serve as saviours to lower the rate of increase in food import demand.展开更多
基金This study received financial support from the Science and Technology Department of Yunnan University,China(2019YNU002)Major Program for Basic Research Project of Yunnan Province,China(202101BC070002)the Special Foundation for National Science and Technology Basic Resources Investigation of China(2019FY202300).
文摘Pseudotsuga forrestii is a relict evergreen coniferous tree species in Pinaceae endemic to China.P.forrestii tree numbers have greatly decreased due to deforestation,over-utilization and habitat degradation.Here we clarify P.forrestii community types,structure,species diversity,seedling recruitments and growth trends.We identified four P.forrestii community types:(1)Pseudotsuga forrestii-Quercus guyavifolia-Acer davidii evergreen coniferous and broad-leaved mixed forest;(2)Pseudotsuga forrestii-Pinus yunnanensis-Quercus guyavifolia evergreen coniferous and broad-leaved mixed forest;(3)Pseudotsuga forrestii evergreen coniferous forest;(4)Pseudotsuga forrestii-Abies georgei var.smithii evergreen coniferous forest.P.forrestii forests are characterized by both warm temperate and temperate affinities.Simpson diversity,Pielou evenness,Shannon-Wiener diversity indices ranged from 0.75 to 0.76,0.74-0.81,and 1.62-1.93,respectively,with no significant differences among the four forest types.The forest stratification was multilayered.The canopy layer was generally 10-25 m tall,with the emergent layer reached 25-42 m.DBH and age structures of P.forrestii showed multimodal distributions.Its maximum age P.forrestii was 570 years with a DBH of 143 cm.The growth of annual ring width of P.forrestii was slow,and generally decreased with age,whereas the basal area at the breast height increased with age.Established seedlings/saplings were mainly found in unstable micro-habitats.Regeneration of P.forrestii depends on moderate natural disturbances.Finally,we provide recommendations for P.forrestii conservation.
基金funded by the Russian Foundation for Basic Research (project no.17-04-00315)
文摘In mountain ecosystems,plants are sensitive to climate changes,and an entire range of species distribution can be observed in a small area.Therefore,mountains are of great interest for climate–growth relationship analysis.In this study,the Siberian spruce’s(Picea obovata Ledeb.)radial growth and its climatic response were investigated in the Western Sayan Mountains,near the SayanoShushenskoe Reservoir.Sampling was performed at three sites along an elevational gradient:at the lower border of the species range,in the middle,and at the treeline.Divergence of growth trends between individual trees was observed at each site,with microsite landscape-soil conditions as the most probable driver of this phenomenon.Cluster analysis of individual tree-ring width series based on inter-serial correlation was carried out,resulting in two sub-set chronologies being developed for each site.These chronologies appear to have substantial differences in their climatic responses,mainly during the cold season.This response was not constant due to regional climatic change and the local influence of the nearby Sayano-Shushenskoe Reservoir.The main response of spruce to growing season conditions has a typical elevational pattern expected in mountains:impact of temperature shifts with elevation from positive to negative,and impact of precipitation shifts in the opposite direction.Chronologies of trees,growing under more severe micro-conditions,are very sensitive to temperature during September–April and to precipitation during October–December,and they record both inter-annual and long-term climatic variation.Consequently,it would be interesting to test if they indicate the Siberian High anticyclone,which is the main driver of these climatic factors.
文摘The paper analyzed the growth level and velocity to find the growth trend with the data collected in 8 investigations on growth of children aged 7～17 years in 1958～1995 in Xi′an. The results showed that child′s growth level was elevated with the passage of years and was the lowest in 1962, the highest in 1995 during the 38 years. The height of boy of the same age in 1995 has average increased by 9 59 cm over 1958 and girl 8 38 cm. The weight of boy of the same age in 1995 has averagely increased by 8 35 kg over 1958 and girl 5 90 kg. The chest girth of boy of the same age in 1995 has average increased by 5 69 cm over 1958 and girl 4 66 cm. The growth level of children aged 9～15 years had greater increase than others in 7～17 years of age. The average increment per 10 years of boy's height was 2 57 cm and girl's 2 26 cm. The average increment of per 10 years of boy's weight was 2 17 kg and girl's 1 56 kg. The average increment of per 10 years of boy's chest girth was 1 50 cm and girl's 1 23 cm. The analysis of the growth velocity in different period during 38 years showed the velocity in 1958～1962 was a negative value and indicated a growth retard, but the velocity in 1962～1964 was the fastest and indicated a catch up growth. And then, growth velocities of height, weight and chest girth were different in different period. The analysis of the growth curves of height, weight and chest girth showed that the 2 cross ages were 1～3 years of age ahead of time and menarche and emission also were ahead of time that during the 38 years indicated there is a child's growth acceleration in Xi′an and the trend of child's growth acceleration could continue if there are more and better nourishment, sports requisites, health care and housing conditions.
基金The paper was excerpied from the major CASS project "Frontier Tracing and Comparative Study of the Macroeconomic Theories and Policies at Home and Abroad".
文摘The growth of the world economy in 2001 featured significant slowdowns, with various developed countries plunging into economic recessions or economic downturns synchronously. Against this context, China was able to maintain a 7.3 percent growth. A simple direct comparison of economic growth of all countries shows that China outshone all the others.
基金supported by National High-tech R&D Program of China (863 Program) under Grant No.2011AA01A206
文摘China＇s cormaaunications industry is an important part of the electronic information industry, and plays a significant role in the national informatization process. In 2006, China issued its National Plans for Medium and Long-term Development of Science and Technology （2006-2020） （NPMLDST）. Since 2006, there has been a rapid increase in the number of citations of China＇s interna- tional papers in the field of communications. In accordance with the goals listed in the NPMLDST, China needs to over- take several competitors by 2020 to be among the top five countries in the field of natural science field. By comparing two Essential Science Indicators （ESI） （i.e., the total number of citations and the number of citations per paper） for China and other countries, China＇s annual growth rate is found to exceed that of other influential countries in the field of sci- ence and technology, and exhibits evident growth-type characteristics. Besides, our study also shows that the short- age of high-quality academic papers in China is the main obstacle to improving the impact of China＇s academic publications.
文摘2025 has seen impressive growth in new business jet deliveries to date;is this trend likely to continue?In terms of new production,the helicopter and business sectors look to be entering growth mode once again,leaving supply chain woes behind us.For business jets,we believe some 8,700 new aircraft will be handed over in the following 10 years(2025-2034).This is driven by an 11%climb this year alone,driven by new types and product ramp-ups.The following analysis discusses this,and concludes with some thoughts on forecast risks.
基金This study was undertaken as a project for National Key Technology R&D Program for the 12th Five-year Plan(China) "Breeding and Selection of New Variety with High Yield and High Resistance of Eucalyptus"(2012BAD01B04-1)Special Fund for Forestry Industry Research in the Public Interest "Project of Veneer Variety Breeding and Cultivation Model Optimization for Eucalyptus"(201104003-07)
文摘We assessed growth traits and wood properties ofDH32-29, a clone of Eucalyptus urophylla x E. grandis, at age of two to six years in Guangdong in China. Analysis of variance of studied traits showed that there were significant differences （1% level） on all studied traits among ages except for wood basic density. Analysis of age trends of growth traits and wood properties revealed that rotation length of DH32-29 should be more than six years or longer. Phenotypic correlations among traits at individual ages indicated that correlations between growth traits were strongly positive. There was significant change in relationship between growth and wood basic density with increasing age, ranging from -0.03 to -0.54 at 2 and 5 year and 0.003 to 0.3 at 3, 4 and 6 year. Correlations between Pilodyn pin penetration and basic density measured on increment cores showed that Pilodyn could rank or group genotypes or sites into density classes, but failure to predict individual tree and individual clone.
基金the AUDI Environmental Foundation for funding this study(project 5101954:“Reaktionskinetik von Baumenunter Klimaveranderungen”—“Reaction kinetics of trees under climate change”).
文摘The growing conditions of urban trees differ substantially from forest sites and are mainly characterized by small planting pits with less water, nutrient and aeration availability, high temperatures and radiation inputs as well as pollution and soil compaction. Especially, global warming can amplify the negative effects of urban microclimates on tree growth, health and well-being of citizens. To quantify the growth of urban trees influenced by the urban climate, ten urban tree species in four climate zones were assessed in an overarching worldwide dendrochronological study. The focus of this analysis was the species water oak (Quercus nigra L.) in Houston, Texas, USA. Similar to the overall growth trend, we found in urban trees, water oaks displayed an accelerated growth during the last decades. Moreover, water oaks in the city center grew better than the water oaks growing in the rural surroundings of Houston, though this trend was reversed with high age. Growth habitat (urban, suburban, rural and forest) significantly affected tree growth (p < 0.001) with urban trees growing faster than rural growing trees and forest trees, though a younger age of urban trees might influence the found growth patterns. Growing site in terms of cardinal direction did not markedly influence tree growth, which was more influenced by the prevalent climatic conditions of Houston and the urban climate. Higher temperatures, an extended growing season and eutrophication can cause an accelerated growth of trees in urban regions across, across all climatic zones. However, an accelerated growth rate can have negative consequences like quicker ageing and tree death resulting in higher costs for new plantings and tree management as well as the decrease in ecosystem services due to a lack of old trees providing greatest benefits for mitigating the negative effects of the urban climate.
基金supported by the Ministry of Health of the People's Republic of China(No.2005‐41)
文摘Objective To describe secular trends on physical growth of children in China during the year of 1985‐2005 and to analyze the urban‐suburban‐rural difference and its change. Methods The measurements of height, weight and chest circumference obtained from two serial national cross‐sectional surveys for children aged 0 to 7 years in China were used to analyze the secular trends, and the growth differences among urban, suburban and rural children were compared. Results The average weight and height for both boys and girls from urban, suburban and rural areas have significantly increased in most age groups during the past 20 years; The average chest circumference increased slightly, ranging from 0.0 to 2.0 cm. From 1985 to 2005, the urban‐suburban difference in height had become smaller, and that in weight showed similar trend for children under 3 years old but became larger after 3 years old; the suburban‐rural difference both in height and weight became larger after 6 months old. The increment per decade in height was the greatest in the suburban group while the greatest increment in weight was the urban group. Conclusion Positive secular trends were observed among urban, suburban and rural areas in Chinese children under 7 years old during the 1980s and the 2000s, reflecting a rapid socio‐economic development in China.
基金Supported by National Science and Technology Support Plan Item, China ( 2007BAD69B09)Soft Science Research Plan Project in Hebei Province,China (10457204D-30,114572124)
文摘[Objective] The aim was to study change tendency of the precipitation resource during growth period of the conventional crops in plain area before Taihang Mountains. [ Method] Based on daily precipitation data at Shijiazhuang meteorological station in recent 51 years, average rainfall dudng growth periods of the 9 kinds of conventional crops was obtained. Precipitation tendency dudng growth periods of the 9 kinds of conventional crops in plain area before Taihang Mountains was analyzed by Mann-Kendall nonparametric test. [ Result] Seen from rainfall during growth pedods of the different crops, rainfall was the least during the growth period of winter wheat, followed by summer corn. Rainfall during growth peri- ods of the cotton, oil plant, vegetable, fruit tree, potato, rice and legumes was more. Under different guaranteed rates, precipitation change also had difference. Rainfall change during growth periods of the wheat and corn was bigger, and rainfall change during growth period of the rice was smaller. Change degree of the precipitation during growth periods of the cotton, oil plant, vegetable, fruit tree and legumes was equivalent, while precipitation change during growth period of the potato was the biggest. Seen from change tendency of the precipitation during growth periods of the different crops, precipitation in the growth period of winter wheat was increasing at a speed of 0.62 mm/a. However, precipitation in growth periods of the other crops had a decreasing tendency. Precipitation in the growth periods of summer corn and legumes decreased at the same speed which was 2.11 mm/a, while precipitation in growth periods of the cotton, oil plant, vegetable, fruit tree, potato and rice decreased insignificantly. [ Con dusion] The study laid foundation for determination of the agricultural irrigation water and provided theoretical reference for regional agricultural water-saving.
文摘This research assessed empirically the quantitative analysis of some selected food imports of Nigeria (rice, wheat and sugar). Time series data were used to examine the determinant of total food imports and the trend in the quantity of the food imported. The secondary data were obtained from institutional and national database over 1981-2010. Descriptive statistics, regression and correlation analysis were used as analytical tools. Statistical analysis shows that food deficit began in the 1970’s, when Nigeria started the importation of food to feed the country. The result of the correlation analysis shows that the postulated determinants of food imports were positively correlated with the quantity of food import. The test for the individual variables shows that;national income explains 40%, external reserves explains 38%, food production index explains 46%, population explains 58% and exchange rate explains 74% of the total variation in the quantity of food import. The over-all goodness of fit of the regression analysis result shows that, the postulated regressors namely, relative price, national income, external reserves, lagged index of domestic food production, population estimate and exchange rate explained approximately 70% of the variability in the quantity of the selected food imports for the period of study. Consequently, there is the need for Nigeria to shift base from the ideology of nationalist orientation, as well as afro centric point of view and move towards unrestrained export-led growth that seeks to develop that market as the first option with corresponding development in international trade. This is however possible by limiting the importation of foods/raw materials that can be sourced for locally, increasing the domestic production of food generally and maintaining a healthy foreign investment with developed countries as a short term measure while in the long run, diversification of the economy, massive investment in agriculture and introduction of population control measures could serve as saviours to lower the rate of increase in food import demand.
