The ecological systems services or multi-functionality of paddy rice cultivation are critical to the functioning of the Earth’s life-support system.We estimated the ecosystem services value(ESV)of paddy rice during 1...The ecological systems services or multi-functionality of paddy rice cultivation are critical to the functioning of the Earth’s life-support system.We estimated the ecosystem services value(ESV)of paddy rice during 1980-2014 across China.The results indicated that the ESV of the paddy field in China showed an upward trend during this period.The share of ESV on CO_(2)sequestration was the highest,followed by ESV on temperature cooling and greenhouse gas(GHG)emission.The yield-scaled ESVs of ZonesⅡ(southern rice-upland crops rotation regions)andⅢ(southern double rice production regions)were similar and significantly higher than the ESVs of ZonesⅠ(northeastern single rice production regions)and IV(Southwest rice-upland crops rotation regions).Between 1980 and 2014,the ESV of each region increased to varying degrees,except for the ESVs of Guangxi,Zhejiang,Fujian,and Guangdong.Such effects suggest the existence of a significant spatial-temporal variation in the total amount,structure,and density of ESV of paddy fields in China,which can further guide the development of future options for the adaptation of healthy rice production in China.展开更多
The Mekong Delta in Vietnam is a region that produces rice and emits methane,a potent greenhouse gas.Vietnam’s rice exports,which rank among the top four globally,have a significant impact on the world’s food suppy....The Mekong Delta in Vietnam is a region that produces rice and emits methane,a potent greenhouse gas.Vietnam’s rice exports,which rank among the top four globally,have a significant impact on the world’s food suppy.The Eddy Covariance system,positioned in the rice field,has been recording methane emission rates and bio-meteorological factors.This study presents the findings of three crop seasons(Summer-Autumn 2020(S-A20),Winter-Spring 2021(W-S21),and Spring-Summer 2021(S-S21))from the year 2020 to 2021.The highest CH4 emission value was observed in the S-S21 crop,reaching 4.14μmol s^(-1 )m^(-2).Elevated CH_(4) emission rates were predominantly recorded during the vegetative stage within first 21 days after planting,while lower CH_(4) emissions were observed during the reproductive and ripening stages.This pattern clearly indicates higher methane emissions at the vegetative stage of the growing rice,likely due to the abundance of organic matter in the rice fields.The average CH4 emission rate was 0.1μmol m^(-2) s^(-1).Notably,high methane emissions were recorded when the soil surface temperature was below 33℃.As a results,the S-S21 exhibits the highest methane emission rates compared to other seasons.展开更多
Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we condu...Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane（CH4） emission compared with continuous flooding, however,the decrement was far lower than the global average level. The N2O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH4 emissions at low level（75 kg N/ha）. But both CH4 and N2O emissions were uninfluenced at the levels of 150 kg N/ha and 225 kg N/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150 kg N/ha. From our results, we recommended that the intermittent irrigation and 150 kg N/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.展开更多
The ecosystem services value （ESV） of rice system has received increasing attention in agricultural policy decision. Over the last three decades, China＇s rice production presented an obviously trend that moving tow...The ecosystem services value （ESV） of rice system has received increasing attention in agricultural policy decision. Over the last three decades, China＇s rice production presented an obviously trend that moving towards north locations. However, the impacts of this migration on the ESV of rice production have not been well documented. In this paper, we analyzed the change of the ESV of rice production in China under ＂north migration＂ and ＂no migration＂ scenarios during 1980-2014 based on long-term historical data. The results showed that both the positive and negative ESVs of rice production were lower under ＂north migration＂ than under ＂no migration＂ scenarios. The total ESV during 1980-2014 was reduced by 15.8%. ＂North migration＂ significantly reduced the area-scaled ESV since the early 1990s; while its impact on yield-scaled ESV was not significant. The effects of＂north migration＂ on ESV showed great spatial variation. The greatest reduction in total and area-scaled ESV was observed in south locations. While the yield-scaled ESVs of most south locations were enhanced under ＂north migration＂ scenario. These results indicated that ＂north migration＂ has generated adverse effects on the ESV of rice production. An adjustment in the spatial distribution is essential to protecting the non-production benefits of rice ecosystem.展开更多
Rice-duck （RD） and rice-fish （RF） ecological systems are major complex planting and breeding models of rice paddy fields in southern China. Studying the methane （CH4） and nitrous oxide （N2O） emissions and thei...Rice-duck （RD） and rice-fish （RF） ecological systems are major complex planting and breeding models of rice paddy fields in southern China. Studying the methane （CH4） and nitrous oxide （N2O） emissions and their economic value from these two ecosystems can provide theoretical and practical basis for further development and utilization of these classical agricultural techniques. CH4 and N2O emissions from RD and RF ecological systems were measured in situ by using static chambers technique. Using global warming potentials （GWPs）, we assessed the greenhouse effect of CH4 and N2O and their economic value. Results showed that the peaks of CH4 emission fluxes from RD and RF appeared at full tillering stage and at heading stage, and the average emission fluxes were significantly （P〈 0.05） lower than that from CK. N2O fluxes remained low when the field is flooded and high after draining the water. Compared with CK, the total amount of N2O emissions was significantly （P〈0.05） higher and slightly lower than those from RD and RF, respectively. In 2006 and 2007, the total greenhouse effect of CH4 and N20 from RD and RF were 4 728.3 and 4 611 kg CO2 ha^-1, 4 545 and 4 754.3 kg CO2 ha^-1, respectively. The costs of greenhouse effect were 970.89 and 946.81 RMB yuan ha^-1, and 933.25 and 976.23 RMB yuan ha^-1, respectively, which were significant lower than those from CK （5 997.6 and 5 391.5 RMB yuan ha^-1）. Except for the environment cost of CH4 and N2O, the economic benefits from RD and RF were 2 210.64 and 4 881.92 RMB yuan ha^-1; 3 798.37 and 5 310.64 RMB yuan ha^-1, respectively, higher than those from CK. Therefore, RD and RF complex ecological planting and breeding models can effectively decrease and control CH4 and N2O emissions, and they are two of the effective strategies to reduce greenhouse gases from rice paddy fields and contribute in alleviating global warming. Thus, their adoption is important to the environment together with their economy benefits.展开更多
Residues of 14C- carbofuran were studied in model late- rice ecosystem (LRE) and early- rice ecosystem (ERE). The treatment consisted of two rates of the pesticide (1x) and 2.5x). At day 56 after application, 7.3% (1x...Residues of 14C- carbofuran were studied in model late- rice ecosystem (LRE) and early- rice ecosystem (ERE). The treatment consisted of two rates of the pesticide (1x) and 2.5x). At day 56 after application, 7.3% (1x) and 2.9% (2.5x) of the pesticide and its degradative products remained in the water of the LRE, and 1.8% (1x) and 2.4% (2.5x) of them remained in the water of the ERE. At harvest, 37.5% (LRE) and 24.0% (ERE) of the pesticide applied were detected in the upper layer of the soil; and 40.6% (LRE) and 26.9% (ERE) remained in the lower layer of the soil. The residues in the rice plants increased at the first stage, reached maximum levels during day 14 to 28 after application, and decreased thereafter. At harvest, residues in the stems and leaves in the two treatments (1x and 2.5x) were 3.91μ g/g and 7.78μ g/g (LRE) and 5.04 μg/g and 17.29 μ g/g (ERE) respectively. Residues in the ears were about 1/8 to 1/12 of that in the other parts of the plants. The pesticide residues in fish bodies in both experiments were also determined.展开更多
The fate of fenitrothion in rice- fish ecosystem was studied using C- fenitrothion (14C- F) labelled at methoxyl and two application rates. The fenitrothion in water disappeared quickly, only 8 and 11 ppb in two treat...The fate of fenitrothion in rice- fish ecosystem was studied using C- fenitrothion (14C- F) labelled at methoxyl and two application rates. The fenitrothion in water disappeared quickly, only 8 and 11 ppb in two treatments at harvest were detected respectively. Most of 14C-F in soil existed in upper layer and that in plants appeared in shoots. The extractable residues in cargo rice were 0.36 and 0.58 ppm in two treatments respectively. 14C- residues (14C- R) were concentrated in bones, next viscera, meat and scales. Total 14C-R in meat were 0.92 and 1.77 ppm at harvest. Comparing two treatments, the residue dynamics of fenitrothion in water, soil, plants and fish were similar. 14C- R in water and soil after harvest affected the rice- fish ecosystem in the next season. However, the extractable 14C- R in cargo rice, soil and water were very low. Fenitrothion 14C- fenitrothion Rice- fish Model展开更多
为探究不同种养模式稻田生态系统的服务价值功能差异,通过田间试验,以水稻单作模式(monoculture,CK)、稻-虾模式(rice-crayfish coculture model,RC)、稻-鸭-虾单元格投放模式(rice-duck-crayfish unit release model,CRXD)、稻-鸭-虾...为探究不同种养模式稻田生态系统的服务价值功能差异,通过田间试验,以水稻单作模式(monoculture,CK)、稻-虾模式(rice-crayfish coculture model,RC)、稻-鸭-虾单元格投放模式(rice-duck-crayfish unit release model,CRXD)、稻-鸭-虾“游牧鸭”模式(rice-duck-crayfish“nomadic duck”model,NRXD)、稻-鸭-虾大田块模式(rice-duck-crayfish large field block model,BRXD)5种稻田生态系统为研究对象,进行生态服务价值评估。结果显示,CK、RC、NRXD、CRXD和BRXD稻田生态系统服务总价值分别为10.43万、13.60万、13.76万、14.06万、13.97万元/hm2,与CK相比,稻田种养模式生态系统服务价值平均增加32.8%。5种稻田模式生态系统中生态价值占总价值的70.3%~81.0%,其中以气候调节功能价值最高,RC、NRXD、CRXD和BRXD的固碳释氧价值分别为6527.48、6609.40、6593.01和6519.91元/hm2。综合分析13项稻田生态系统服务功能和4种稻田种养模式生态系统服务价值,以稻-鸭-虾单元格投放模式生态系统服务价值最高,为14.06万元/hm2。展开更多
Rice-wheat （R-W） rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding th...Rice-wheat （R-W） rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding the seasonal and interannual variation of the carbon budget over R-W rotation systems. In this study, measurements of CO2 fluxes and meteorological variables over an R-W rotation system on the North China Plain from 2007 to 2010 were analyzed. To analyze the abiotic factors regulating Net Ecosystem Exchange （NEE）, NEE was partitioned into gross primary production （GPP） and ecosystem respiration. Nighttime NEE or ecosystem respiration was controlled primarily by soil temperature, while daytime NEE was mainly determined by photosythetically active radiation （PAR）. The responses of nighttime NEE to soil temperature and daytime NEE to light were closely associated with crop development and photosynthetic activity, respectively. Moreover, the interannual variation in GPP and NEE mainly depended on precipitation and PAR. Overall, NEE was negative on the annual scale and the rotation system behaved as a carbon sink of 982 g C m 2 per year over the three years. The winter wheat field took up more CO2 than the rice paddy during the longer growing season, while the daily NEE for wheat and rice were -2.35 and -3.96 g C m-2, respectively. After the grain harvest was subtracted from the NEE, the winter wheat field became a moderately strong carbon sink of 251-334 g C m-2 per season, whereas the rice paddy switched to a weak carbon sink of 107-132 per season.展开更多
Cultivated rice (Oryza sativa L. and Oryza. glaberrima) is one of the most important food crops in the world. World rice production has increased three times since the green revolution. However, climate change and glo...Cultivated rice (Oryza sativa L. and Oryza. glaberrima) is one of the most important food crops in the world. World rice production has increased three times since the green revolution. However, climate change and global warming effects as well as ever increasing world population will require the world to produce more rice without increasing area under rice production in order to meet those demands. The best option to overcome these challenges includes adoption of climate-smart technologies and sustainable solutions to rice production. Rice was probably introduced in Tanzania over 1000 years ago by Asian traders during trade contacts between Asia and East Africa Coast through Indian Ocean. Rice cultivation had been restricted to coastal area until 19th century when it started spreading to interior areas of Tanzania. During colonial period (1880s-1960s), the emphasis was to produce cash crops as raw materials for industrialized world. After independence production of rice increased significantly. Currently, rice is the second most important food crop in Tanzania after maize and Tanzania is the leading producer of rice in East African countries. It ranks 4th and 22nd in Africa and World respectively in terms of rice production. In this paper, the rice history, ecosystems, challenges and future perspective for sustaining rice production in Tanzania is reviewed.展开更多
基金supported by the Natural Science Foundation of Zhejiang,China(Q21C130007)the National Key Research and Development Program of China(2016YFD0300210)。
文摘The ecological systems services or multi-functionality of paddy rice cultivation are critical to the functioning of the Earth’s life-support system.We estimated the ecosystem services value(ESV)of paddy rice during 1980-2014 across China.The results indicated that the ESV of the paddy field in China showed an upward trend during this period.The share of ESV on CO_(2)sequestration was the highest,followed by ESV on temperature cooling and greenhouse gas(GHG)emission.The yield-scaled ESVs of ZonesⅡ(southern rice-upland crops rotation regions)andⅢ(southern double rice production regions)were similar and significantly higher than the ESVs of ZonesⅠ(northeastern single rice production regions)and IV(Southwest rice-upland crops rotation regions).Between 1980 and 2014,the ESV of each region increased to varying degrees,except for the ESVs of Guangxi,Zhejiang,Fujian,and Guangdong.Such effects suggest the existence of a significant spatial-temporal variation in the total amount,structure,and density of ESV of paddy fields in China,which can further guide the development of future options for the adaptation of healthy rice production in China.
基金funded by Vietnam National University,Ho Chi Minh City(VNU-HCM)under grant number C2022-18-15.
文摘The Mekong Delta in Vietnam is a region that produces rice and emits methane,a potent greenhouse gas.Vietnam’s rice exports,which rank among the top four globally,have a significant impact on the world’s food suppy.The Eddy Covariance system,positioned in the rice field,has been recording methane emission rates and bio-meteorological factors.This study presents the findings of three crop seasons(Summer-Autumn 2020(S-A20),Winter-Spring 2021(W-S21),and Spring-Summer 2021(S-S21))from the year 2020 to 2021.The highest CH4 emission value was observed in the S-S21 crop,reaching 4.14μmol s^(-1 )m^(-2).Elevated CH_(4) emission rates were predominantly recorded during the vegetative stage within first 21 days after planting,while lower CH_(4) emissions were observed during the reproductive and ripening stages.This pattern clearly indicates higher methane emissions at the vegetative stage of the growing rice,likely due to the abundance of organic matter in the rice fields.The average CH4 emission rate was 0.1μmol m^(-2) s^(-1).Notably,high methane emissions were recorded when the soil surface temperature was below 33℃.As a results,the S-S21 exhibits the highest methane emission rates compared to other seasons.
基金supported by the China Postdoctoral Science Foundation(No.2012M511005)National Key Technology Support Program of China(No.2015BAC02B02)+6 种基金the Agro-scientific Research Programs in Public Interest(No.201303102)National Natural Science Foundation of China(No.31501263)the Postdoctoral Financial Assistance of Heilongjiang Province(No.LBH-Z12232)the Scientific Research Initiation Fund for Introduction of Ph.D Talent of Heilongjiang Academy of Agricultural Sciences(No.201507-14)the State Key Program of China(No.2016YFD0300900)the Major Project of Research and Development of Applied Technology of Heilongjiang Province(No.GA15B101)the Provincial Matching Funds to the National Foundation of Applied Technology Research and Development Program in Heilongjiang Province(No.GX16B002)
文摘Water regime and nitrogen（N） fertilizer are two important factors impacting greenhouse gases（GHG） emission from paddy field, whereas their effects have not been well studied in cold region. In this study, we conducted a two-year field experiment to study the impacts of water regime and N fertilizer on rice yields and GHG emissions in Harbin, China, a cold region located in high latitudes. Our results showed that intermittent irrigation significantly decreased methane（CH4） emission compared with continuous flooding, however,the decrement was far lower than the global average level. The N2O emissions were very small when flooded but peaked at the beginning of the disappearance of floodwater. The N fertilizer treatments increased CH4 emissions at low level（75 kg N/ha）. But both CH4 and N2O emissions were uninfluenced at the levels of 150 kg N/ha and 225 kg N/ha. Rice yields increased under intermittent irrigation and were highest at the level of 150 kg N/ha. From our results, we recommended that the intermittent irrigation and 150 kg N/ha as the ideal water regime-nitrogen fertilizer incorporation for this area to achieve low GHG emissions without impacting rice yields.
基金supported by the Innovation Program of Chinese Academy of Agricultural Sciences
文摘The ecosystem services value （ESV） of rice system has received increasing attention in agricultural policy decision. Over the last three decades, China＇s rice production presented an obviously trend that moving towards north locations. However, the impacts of this migration on the ESV of rice production have not been well documented. In this paper, we analyzed the change of the ESV of rice production in China under ＂north migration＂ and ＂no migration＂ scenarios during 1980-2014 based on long-term historical data. The results showed that both the positive and negative ESVs of rice production were lower under ＂north migration＂ than under ＂no migration＂ scenarios. The total ESV during 1980-2014 was reduced by 15.8%. ＂North migration＂ significantly reduced the area-scaled ESV since the early 1990s; while its impact on yield-scaled ESV was not significant. The effects of＂north migration＂ on ESV showed great spatial variation. The greatest reduction in total and area-scaled ESV was observed in south locations. While the yield-scaled ESVs of most south locations were enhanced under ＂north migration＂ scenario. These results indicated that ＂north migration＂ has generated adverse effects on the ESV of rice production. An adjustment in the spatial distribution is essential to protecting the non-production benefits of rice ecosystem.
基金supported by Important National Science&Technoligy Specific Projects, China (2004BA520A02)
文摘Rice-duck （RD） and rice-fish （RF） ecological systems are major complex planting and breeding models of rice paddy fields in southern China. Studying the methane （CH4） and nitrous oxide （N2O） emissions and their economic value from these two ecosystems can provide theoretical and practical basis for further development and utilization of these classical agricultural techniques. CH4 and N2O emissions from RD and RF ecological systems were measured in situ by using static chambers technique. Using global warming potentials （GWPs）, we assessed the greenhouse effect of CH4 and N2O and their economic value. Results showed that the peaks of CH4 emission fluxes from RD and RF appeared at full tillering stage and at heading stage, and the average emission fluxes were significantly （P〈 0.05） lower than that from CK. N2O fluxes remained low when the field is flooded and high after draining the water. Compared with CK, the total amount of N2O emissions was significantly （P〈0.05） higher and slightly lower than those from RD and RF, respectively. In 2006 and 2007, the total greenhouse effect of CH4 and N20 from RD and RF were 4 728.3 and 4 611 kg CO2 ha^-1, 4 545 and 4 754.3 kg CO2 ha^-1, respectively. The costs of greenhouse effect were 970.89 and 946.81 RMB yuan ha^-1, and 933.25 and 976.23 RMB yuan ha^-1, respectively, which were significant lower than those from CK （5 997.6 and 5 391.5 RMB yuan ha^-1）. Except for the environment cost of CH4 and N2O, the economic benefits from RD and RF were 2 210.64 and 4 881.92 RMB yuan ha^-1; 3 798.37 and 5 310.64 RMB yuan ha^-1, respectively, higher than those from CK. Therefore, RD and RF complex ecological planting and breeding models can effectively decrease and control CH4 and N2O emissions, and they are two of the effective strategies to reduce greenhouse gases from rice paddy fields and contribute in alleviating global warming. Thus, their adoption is important to the environment together with their economy benefits.
基金Research carried out with the support of IAEA under Research Contract No. 4233/RB
文摘Residues of 14C- carbofuran were studied in model late- rice ecosystem (LRE) and early- rice ecosystem (ERE). The treatment consisted of two rates of the pesticide (1x) and 2.5x). At day 56 after application, 7.3% (1x) and 2.9% (2.5x) of the pesticide and its degradative products remained in the water of the LRE, and 1.8% (1x) and 2.4% (2.5x) of them remained in the water of the ERE. At harvest, 37.5% (LRE) and 24.0% (ERE) of the pesticide applied were detected in the upper layer of the soil; and 40.6% (LRE) and 26.9% (ERE) remained in the lower layer of the soil. The residues in the rice plants increased at the first stage, reached maximum levels during day 14 to 28 after application, and decreased thereafter. At harvest, residues in the stems and leaves in the two treatments (1x and 2.5x) were 3.91μ g/g and 7.78μ g/g (LRE) and 5.04 μg/g and 17.29 μ g/g (ERE) respectively. Residues in the ears were about 1/8 to 1/12 of that in the other parts of the plants. The pesticide residues in fish bodies in both experiments were also determined.
文摘The fate of fenitrothion in rice- fish ecosystem was studied using C- fenitrothion (14C- F) labelled at methoxyl and two application rates. The fenitrothion in water disappeared quickly, only 8 and 11 ppb in two treatments at harvest were detected respectively. Most of 14C-F in soil existed in upper layer and that in plants appeared in shoots. The extractable residues in cargo rice were 0.36 and 0.58 ppm in two treatments respectively. 14C- residues (14C- R) were concentrated in bones, next viscera, meat and scales. Total 14C-R in meat were 0.92 and 1.77 ppm at harvest. Comparing two treatments, the residue dynamics of fenitrothion in water, soil, plants and fish were similar. 14C- R in water and soil after harvest affected the rice- fish ecosystem in the next season. However, the extractable 14C- R in cargo rice, soil and water were very low. Fenitrothion 14C- fenitrothion Rice- fish Model
文摘为探究不同种养模式稻田生态系统的服务价值功能差异,通过田间试验,以水稻单作模式(monoculture,CK)、稻-虾模式(rice-crayfish coculture model,RC)、稻-鸭-虾单元格投放模式(rice-duck-crayfish unit release model,CRXD)、稻-鸭-虾“游牧鸭”模式(rice-duck-crayfish“nomadic duck”model,NRXD)、稻-鸭-虾大田块模式(rice-duck-crayfish large field block model,BRXD)5种稻田生态系统为研究对象,进行生态服务价值评估。结果显示,CK、RC、NRXD、CRXD和BRXD稻田生态系统服务总价值分别为10.43万、13.60万、13.76万、14.06万、13.97万元/hm2,与CK相比,稻田种养模式生态系统服务价值平均增加32.8%。5种稻田模式生态系统中生态价值占总价值的70.3%~81.0%,其中以气候调节功能价值最高,RC、NRXD、CRXD和BRXD的固碳释氧价值分别为6527.48、6609.40、6593.01和6519.91元/hm2。综合分析13项稻田生态系统服务功能和4种稻田种养模式生态系统服务价值,以稻-鸭-虾单元格投放模式生态系统服务价值最高,为14.06万元/hm2。
基金supported by the China Meteorological Administration (Grant No.GYHY201006024)the National Key Basic Research Program (Grant Nos.2010CB428502 and 2012CB417203)+2 种基金the Chinese Academy of Sciences Strategic Priority Research Program (Grant No.XDA05110101)the National Natural Science Foundation of China (Grant Nos.40975009 and 41405018)the State Key Laboratory of Atmospheric Boundary Layer Physics and Atmospheric Chemistry,Institute of Atmospheric Physics,Chinese Academy of Sciences (Grant No.LAPC-KF-2009-02)
文摘Rice-wheat （R-W） rotation systems are ubiquitous in South and East Asia, and play an important role in modulating the carbon cycle and climate. Long-term, continuous flux measurements help in better understanding the seasonal and interannual variation of the carbon budget over R-W rotation systems. In this study, measurements of CO2 fluxes and meteorological variables over an R-W rotation system on the North China Plain from 2007 to 2010 were analyzed. To analyze the abiotic factors regulating Net Ecosystem Exchange （NEE）, NEE was partitioned into gross primary production （GPP） and ecosystem respiration. Nighttime NEE or ecosystem respiration was controlled primarily by soil temperature, while daytime NEE was mainly determined by photosythetically active radiation （PAR）. The responses of nighttime NEE to soil temperature and daytime NEE to light were closely associated with crop development and photosynthetic activity, respectively. Moreover, the interannual variation in GPP and NEE mainly depended on precipitation and PAR. Overall, NEE was negative on the annual scale and the rotation system behaved as a carbon sink of 982 g C m 2 per year over the three years. The winter wheat field took up more CO2 than the rice paddy during the longer growing season, while the daily NEE for wheat and rice were -2.35 and -3.96 g C m-2, respectively. After the grain harvest was subtracted from the NEE, the winter wheat field became a moderately strong carbon sink of 251-334 g C m-2 per season, whereas the rice paddy switched to a weak carbon sink of 107-132 per season.
文摘Cultivated rice (Oryza sativa L. and Oryza. glaberrima) is one of the most important food crops in the world. World rice production has increased three times since the green revolution. However, climate change and global warming effects as well as ever increasing world population will require the world to produce more rice without increasing area under rice production in order to meet those demands. The best option to overcome these challenges includes adoption of climate-smart technologies and sustainable solutions to rice production. Rice was probably introduced in Tanzania over 1000 years ago by Asian traders during trade contacts between Asia and East Africa Coast through Indian Ocean. Rice cultivation had been restricted to coastal area until 19th century when it started spreading to interior areas of Tanzania. During colonial period (1880s-1960s), the emphasis was to produce cash crops as raw materials for industrialized world. After independence production of rice increased significantly. Currently, rice is the second most important food crop in Tanzania after maize and Tanzania is the leading producer of rice in East African countries. It ranks 4th and 22nd in Africa and World respectively in terms of rice production. In this paper, the rice history, ecosystems, challenges and future perspective for sustaining rice production in Tanzania is reviewed.
