Due to the lack of accurate data and complex parameterization,the prediction of groundwater depth is a chal-lenge for numerical models.Machine learning can effectively solve this issue and has been proven useful in th...Due to the lack of accurate data and complex parameterization,the prediction of groundwater depth is a chal-lenge for numerical models.Machine learning can effectively solve this issue and has been proven useful in the prediction of groundwater depth in many areas.In this study,two new models are applied to the prediction of groundwater depth in the Ningxia area,China.The two models combine the improved dung beetle optimizer(DBO)algorithm with two deep learning models:The Multi-head Attention-Convolution Neural Network-Long Short Term Memory networks(MH-CNN-LSTM)and the Multi-head Attention-Convolution Neural Network-Gated Recurrent Unit(MH-CNN-GRU).The models with DBO show better prediction performance,with larger R(correlation coefficient),RPD(residual prediction deviation),and lower RMSE(root-mean-square error).Com-pared with the models with the original DBO,the R and RPD of models with the improved DBO increase by over 1.5%,and the RMSE decreases by over 1.8%,indicating better prediction results.In addition,compared with the multiple linear regression model,a traditional statistical model,deep learning models have better prediction performance.展开更多
As China’s first new energy comprehensive demonstration zone,Ningxia’s solar photovoltaic(PV)industry has developed rapidly,but it still faces shortcomings in terms of intelligence and digitalization.This study focu...As China’s first new energy comprehensive demonstration zone,Ningxia’s solar photovoltaic(PV)industry has developed rapidly,but it still faces shortcomings in terms of intelligence and digitalization.This study focuses on the application and construction of an intelligent big data platform based on Narrowband Internet of Things(NB-IoT)technology within Ningxia’s solar PV industry.It explores the application trends of digital technology in the energy sector,particularly in the PV industry under the backdrop of energy reform,analyzes the technological development status of the smart energy field both domestically and internationally,and details the research methods and design components of the platform(including the photovoltaic base data platform,outdoor mobile application,remote data system,and back-office management system).The study discusses the opportunities and challenges Ningxia’s PV industry faces and proposes a construction pathway.It provides a theoretical foundation and technical support for the digital transformation of Ningxia’s PV industry,facilitating industrial upgrading and sustainable development.Although the current research is limited to the proposed design scheme,it establishes a basis for future empirical research and platform development.展开更多
Based on TM image data in 1989, 1995, 1999, 2003, 2006 and 2009 of Yanchi County of Ningxia, the land use date of Yanchi County in each year were extracted supported by RS and GIS technology, and used to analyze the d...Based on TM image data in 1989, 1995, 1999, 2003, 2006 and 2009 of Yanchi County of Ningxia, the land use date of Yanchi County in each year were extracted supported by RS and GIS technology, and used to analyze the dynamic change of land use. The land use data were studied for estimating the change of ecosystem services value caused by the land use change of Yanchi County, using the evaluation method of China terrestrial ecosystem services value. The results showed that the changes of land use were obvious during 1989 to 2009. The area of woodland and construction land had an increasing tendency; grassland area changed from decreasing to increasing, which was in contrary to farmland and un-used land areas （from increasing to decreasing）; water area fluctuated slightly. The ecosystem services value of Yanchi County had an increasing tendency during 1989 to 1995, because the increasing woodland area had took the major role in raising the total ecosystem services value. The grassland accounted for a large proportion of the total ecosystem service value of Yanchi County, with its contribution rate from 49.8% to 60.4%. And the composition of the ecosystem services value of Yanchi County happened benign change for the increasing contribution rate of woodland. The ecosystem services value sensitivity index of each land use type was less than 1, indicating that the ecosystem services value of Yanchi County lacks flexibility on its service value index, and the research results are reliable.展开更多
[Objective] The aim was to quantitatively predict the variation trend of maize yield in Yellow River irrigation area of Ningxia under future climate change scenarios.[Method] Based on the data of daily temperature,pre...[Objective] The aim was to quantitatively predict the variation trend of maize yield in Yellow River irrigation area of Ningxia under future climate change scenarios.[Method] Based on the data of daily temperature,precipitation and radiation in 25 km × 25 km grid in Ningxia from 2010 to 2100 obtained by regional climate model,maize yield in Yellow River irrigation area of Ningxia in the 21st century was studied by means of corrected CERES-Maize model.[Result] With climate warming,maize yield in Yellow River irrigation area of Ningxia in 2020s and 2050s showed increase trend compared with base years（average in 1961-1990）when current adaptive maize variety and optimum production management measures were adopted,while maize yield went down in 2080s with the further increase of temperature.The grain number per spike and spike grain weight as the yield components of maize also showed the same trend with maize yield.In 2020s and 2050s,the increase of maize yield under B2 scenario was higher than that under A2 scenario,while the decrease of maize yield under B2 scenario was lower than that under A2 scenario in 2080s.[Conclusion] With the increase of temperature,maize yield in Yellow River irrigation area of Ningxia went up firstly and then went down.展开更多
Based on seasonal and annual observed precipitation data at 19 meteorological stations in Ningxia Hui Autonomous Region,the temporal and spatial distribution characteristic is analyzed by EOF method.And spatial charac...Based on seasonal and annual observed precipitation data at 19 meteorological stations in Ningxia Hui Autonomous Region,the temporal and spatial distribution characteristic is analyzed by EOF method.And spatial characteristics and temporal changes trends of EOF of seasonal and annual precipitation have been showed.The main period and sudden changes point of EOF of annual precipitation have been studied by Mann-Kendall and spectrum analysis method.展开更多
[Objective] This study aimed to analyze the sustainability of cropland use in cropping-pastoral ecotone before and after the Grain-for-Green Policy. [Method] Using Yanchi County in Ningxia Hui Autonomous Region as a c...[Objective] This study aimed to analyze the sustainability of cropland use in cropping-pastoral ecotone before and after the Grain-for-Green Policy. [Method] Using Yanchi County in Ningxia Hui Autonomous Region as a case study area, this investigation used the annual transfer rate of land use types, cropland suitability and emergy analysis to examine the major pressures affecting the sustainable use of cropland before and after the Grain-for-Green Policy. [Result] The expansion of con- struction land onto cropland was significant; the annual cropland area was still larger than the land area suitable for cropping after the policy; agrochemical inputs used for crop production gradually increased and unit crop outputs required more agro- chemical inputs. Cropland use sustainability showed a fluctuating downward trend. [Conclusion] The results imply that the protection of high quality cropland, further im- plementation of the policy and control of agrochemical inputs according to precipita- tion are the main measures needed for sustainable cropland use in cropping-pastoral ecotone.展开更多
[Objective] The aim was to study the characteristics of the changes of extreme weather climate incidents such as severe drought in northwest and rainstorm in Xiji County of Ningxia. [Method] Precipitation anomaly perc...[Objective] The aim was to study the characteristics of the changes of extreme weather climate incidents such as severe drought in northwest and rainstorm in Xiji County of Ningxia. [Method] Precipitation anomaly percentage was applied to divide drought level and for statistics analysis. Seasonal index, linear tendency, and 5-years gliding average were used to reflect the trend of drought changes. The circulation wave of temporal sequence used polynomial expression to simulate the interannual variation scale. The positive part of the polynomial expression used bar chart to simulate interannual variation scale. [Result] The index of drought season from November to June was large. The general trend of annual drought was increasing. The drought of interannual scale was most serious around 1977, about 15 and 20 years. The drought in recent years went up. The general situation of drought, interannual scale and changes of interannual scales from March to May and from September to October were discussed. Based on the weather at 500 hPa, the first rain in Xiji and the drought-turning-into-rain situation were classified. [Conclusion]These may provide reference value to the prevention and mitigation of drought.展开更多
Targeted at the residence status in rural settlements of Hui people in central Ningxia Hui Nationality Autonomous Region, this research revealed that the construction of new countryside and the transformation of old c...Targeted at the residence status in rural settlements of Hui people in central Ningxia Hui Nationality Autonomous Region, this research revealed that the construction of new countryside and the transformation of old countryside all have to be on the basis of present topography, landform, environment, social-economic level, education, religion, customs, living habits and so on. The primary goal of this research was to find a method of ecology, low energy consumption and sustainable development to bring the green planning implementation strategies, to provide guidance for sustainable planning in the rural settlements of Hui Nationality in central Ningxia.展开更多
A quantitative model is built and the historical variation of natural disasters is analyzed in this paper,by using materials as affected area(damaged area),affected population(dead and injured),casualty of livestock,c...A quantitative model is built and the historical variation of natural disasters is analyzed in this paper,by using materials as affected area(damaged area),affected population(dead and injured),casualty of livestock,collapsed houses(damaged houses),decrease of crops yield,economic loss(direct and indirect) and price index over the same period of Ningxia natural disasters(include drought,flood,gale and hail,frost,pest disasters and other disasters) during 1978-2007,and applying gray correlation analysis method.The long-term changes trend of natural disasters is analyzed by the application of the least squares method for linear trend,and the oscillation period is analyzed by using the maximum entropy statistical method.It is found that natural disasters have basically 2 to 3 years of variation period either in the whole region or in the individual regions;from the mid 1980s to the late 1990s,Ningxia is in an oscillation period with disasters attacked frequently in decadal and interannual scale under the background of climate;the increase of damage intensity of natural disasters slow down and tends to decrease since 2000.展开更多
Frequent periods of drought conditions are known to limit plant performance,primary production,and ecosystem stability in arid and semi-arid desert steppe environments.Plants often avoid competition by shifting their ...Frequent periods of drought conditions are known to limit plant performance,primary production,and ecosystem stability in arid and semi-arid desert steppe environments.Plants often avoid competition by shifting their water use seasonally,which affects the water-use patterns of dominant species as well as the composition and structure of plant communities.However,the water-use strategies of dominant herbaceous species,which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region,China,are poorly known.Here,we explored the possible sources of water uptake and water-use efficiency(WUE)of three dominant herbaceous plant species(Stipa breviflora,Agropyron mongolicum,and Glycyrrhiza uralensis)in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters,including(1)the stable isotopic oxygen and hydrogen(δ18O andδ2H)compositions of precipitation,soil water,and stem water,(2)the carbon isotope(13C)composition of leaves,and(3)the soil water contents,based on field sampling across varying water conditions from June to September,2017.Frequent small precipitation events replenished shallow soil water,whereas large events only percolated down to the deep soil layers.Changes in soil water availability affected the water-use patterns of plants.Generally,during light precipitation periods,the deep root system of G.uralensis accessed deeper(>80 cm)soil water,whereas S.breviflora and A.mongolicum,which only have shallow roots,primarily absorbed water from the shallow and middle soil layers.As precipitation increased,all three plant species primarily obtained water from the shallow soil layers.Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water.In addition,theδ13C values of G.uralensis and S.breviflora were higher than those of A.mongolicum.Theδ13C values of the three plant species were significantly negatively correlated with soil water content.Therefore,G.uralensis and S.breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season.In contrast,A.mongolicum,with a relatively low WUE in the wet season but a high WUE in the dry season,exhibited a more flexible water-use strategy.The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.展开更多
Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studi...Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. （alfalfa） grassland biomass carbon and soil organic carbon density （SOCD） in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period （viz. 0-10 year）. Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for l0 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.展开更多
Based on daily rainfall data from 26 station records,spatial and temporal variations in annual and seasonal precipitation of different rainfall intensities from 1961 to 2018 in Ningxia,China are investigated using the...Based on daily rainfall data from 26 station records,spatial and temporal variations in annual and seasonal precipitation of different rainfall intensities from 1961 to 2018 in Ningxia,China are investigated using the innovative trend analysis(ITA)method.The results show that annual precipitation increases on the northern plain but decreases in the southern mountainous area.The increase in regional annual precipitation is mainly due to an increase in weak precipitation,while the decrease in regional annual rainfall is a result of a reduction in heavy precipitation.Lowintensity precipitation shows an upward trend,while high-intensity precipitation shows a downward trend.The variation trend of extreme precipitation is more obvious.The contributions of different types of extreme precipitation vary by season.During spring,the increase in regional rainfall is mainly caused by the increase in heavy precipitation,while the decrease in regional precipitation is mainly caused by the decrease in weak precipitation.During summer and autumn,the increase in regional precipitation is caused by the increase in light precipitation,while the reduction in regional rainfall is caused by the decrease in heavy precipitation.This study provides support for water resources planning and addressing droughts and floods.展开更多
Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation a...Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.展开更多
基金supported by the National Natural Science Foundation of China [grant numbers 42088101 and 42375048]。
文摘Due to the lack of accurate data and complex parameterization,the prediction of groundwater depth is a chal-lenge for numerical models.Machine learning can effectively solve this issue and has been proven useful in the prediction of groundwater depth in many areas.In this study,two new models are applied to the prediction of groundwater depth in the Ningxia area,China.The two models combine the improved dung beetle optimizer(DBO)algorithm with two deep learning models:The Multi-head Attention-Convolution Neural Network-Long Short Term Memory networks(MH-CNN-LSTM)and the Multi-head Attention-Convolution Neural Network-Gated Recurrent Unit(MH-CNN-GRU).The models with DBO show better prediction performance,with larger R(correlation coefficient),RPD(residual prediction deviation),and lower RMSE(root-mean-square error).Com-pared with the models with the original DBO,the R and RPD of models with the improved DBO increase by over 1.5%,and the RMSE decreases by over 1.8%,indicating better prediction results.In addition,compared with the multiple linear regression model,a traditional statistical model,deep learning models have better prediction performance.
基金supported by the Scientific Research Foundation of Xinhua College,Ningxia University,ChinaProject name:Preliminary Exploration of Ningxia Solar Photovoltaic Industry Intelligent Big Data Platform Construction Based on NB-IoT(Project No.23XHKY07).
文摘As China’s first new energy comprehensive demonstration zone,Ningxia’s solar photovoltaic(PV)industry has developed rapidly,but it still faces shortcomings in terms of intelligence and digitalization.This study focuses on the application and construction of an intelligent big data platform based on Narrowband Internet of Things(NB-IoT)technology within Ningxia’s solar PV industry.It explores the application trends of digital technology in the energy sector,particularly in the PV industry under the backdrop of energy reform,analyzes the technological development status of the smart energy field both domestically and internationally,and details the research methods and design components of the platform(including the photovoltaic base data platform,outdoor mobile application,remote data system,and back-office management system).The study discusses the opportunities and challenges Ningxia’s PV industry faces and proposes a construction pathway.It provides a theoretical foundation and technical support for the digital transformation of Ningxia’s PV industry,facilitating industrial upgrading and sustainable development.Although the current research is limited to the proposed design scheme,it establishes a basis for future empirical research and platform development.
基金supported by the National Key Technology R&D Program of China(2012BAD16B02)National Forestry Public Welfare Industry Research of China(201004018)~~
文摘Based on TM image data in 1989, 1995, 1999, 2003, 2006 and 2009 of Yanchi County of Ningxia, the land use date of Yanchi County in each year were extracted supported by RS and GIS technology, and used to analyze the dynamic change of land use. The land use data were studied for estimating the change of ecosystem services value caused by the land use change of Yanchi County, using the evaluation method of China terrestrial ecosystem services value. The results showed that the changes of land use were obvious during 1989 to 2009. The area of woodland and construction land had an increasing tendency; grassland area changed from decreasing to increasing, which was in contrary to farmland and un-used land areas （from increasing to decreasing）; water area fluctuated slightly. The ecosystem services value of Yanchi County had an increasing tendency during 1989 to 1995, because the increasing woodland area had took the major role in raising the total ecosystem services value. The grassland accounted for a large proportion of the total ecosystem service value of Yanchi County, with its contribution rate from 49.8% to 60.4%. And the composition of the ecosystem services value of Yanchi County happened benign change for the increasing contribution rate of woodland. The ecosystem services value sensitivity index of each land use type was less than 1, indicating that the ecosystem services value of Yanchi County lacks flexibility on its service value index, and the research results are reliable.
基金Supported by Project of Ministry of Science and Technology of China"Response of Ningxia Climate to Global Climate Change and Its Mechanism"(2004DIB3J121)Climate Change Project of China Meteorological Administration(CCSF2007-27)Climate Change Bilateral Cooperation Project of China and Britain(2001-BA611B-04-06-01)~~
文摘[Objective] The aim was to quantitatively predict the variation trend of maize yield in Yellow River irrigation area of Ningxia under future climate change scenarios.[Method] Based on the data of daily temperature,precipitation and radiation in 25 km × 25 km grid in Ningxia from 2010 to 2100 obtained by regional climate model,maize yield in Yellow River irrigation area of Ningxia in the 21st century was studied by means of corrected CERES-Maize model.[Result] With climate warming,maize yield in Yellow River irrigation area of Ningxia in 2020s and 2050s showed increase trend compared with base years（average in 1961-1990）when current adaptive maize variety and optimum production management measures were adopted,while maize yield went down in 2080s with the further increase of temperature.The grain number per spike and spike grain weight as the yield components of maize also showed the same trend with maize yield.In 2020s and 2050s,the increase of maize yield under B2 scenario was higher than that under A2 scenario,while the decrease of maize yield under B2 scenario was lower than that under A2 scenario in 2080s.[Conclusion] With the increase of temperature,maize yield in Yellow River irrigation area of Ningxia went up firstly and then went down.
文摘Based on seasonal and annual observed precipitation data at 19 meteorological stations in Ningxia Hui Autonomous Region,the temporal and spatial distribution characteristic is analyzed by EOF method.And spatial characteristics and temporal changes trends of EOF of seasonal and annual precipitation have been showed.The main period and sudden changes point of EOF of annual precipitation have been studied by Mann-Kendall and spectrum analysis method.
基金Supported by the National Basic Research Program of China [2009CB421307 (2009-2013)]the Natural Science Foundation of China [40971282(2010-2012)]~~
文摘[Objective] This study aimed to analyze the sustainability of cropland use in cropping-pastoral ecotone before and after the Grain-for-Green Policy. [Method] Using Yanchi County in Ningxia Hui Autonomous Region as a case study area, this investigation used the annual transfer rate of land use types, cropland suitability and emergy analysis to examine the major pressures affecting the sustainable use of cropland before and after the Grain-for-Green Policy. [Result] The expansion of con- struction land onto cropland was significant; the annual cropland area was still larger than the land area suitable for cropping after the policy; agrochemical inputs used for crop production gradually increased and unit crop outputs required more agro- chemical inputs. Cropland use sustainability showed a fluctuating downward trend. [Conclusion] The results imply that the protection of high quality cropland, further im- plementation of the policy and control of agrochemical inputs according to precipita- tion are the main measures needed for sustainable cropland use in cropping-pastoral ecotone.
基金Supported by National Natural Science Foundation of China(40765003)Guyuan Meteorological Bureau Science and Technology Program in Ningxia~~
文摘[Objective] The aim was to study the characteristics of the changes of extreme weather climate incidents such as severe drought in northwest and rainstorm in Xiji County of Ningxia. [Method] Precipitation anomaly percentage was applied to divide drought level and for statistics analysis. Seasonal index, linear tendency, and 5-years gliding average were used to reflect the trend of drought changes. The circulation wave of temporal sequence used polynomial expression to simulate the interannual variation scale. The positive part of the polynomial expression used bar chart to simulate interannual variation scale. [Result] The index of drought season from November to June was large. The general trend of annual drought was increasing. The drought of interannual scale was most serious around 1977, about 15 and 20 years. The drought in recent years went up. The general situation of drought, interannual scale and changes of interannual scales from March to May and from September to October were discussed. Based on the weather at 500 hPa, the first rain in Xiji and the drought-turning-into-rain situation were classified. [Conclusion]These may provide reference value to the prevention and mitigation of drought.
基金Supported by the Project of Natural Science Fund of Ningxia in 2009(NZ0943)the Project of College Science Research of Ningxia in 2008~~
文摘Targeted at the residence status in rural settlements of Hui people in central Ningxia Hui Nationality Autonomous Region, this research revealed that the construction of new countryside and the transformation of old countryside all have to be on the basis of present topography, landform, environment, social-economic level, education, religion, customs, living habits and so on. The primary goal of this research was to find a method of ecology, low energy consumption and sustainable development to bring the green planning implementation strategies, to provide guidance for sustainable planning in the rural settlements of Hui Nationality in central Ningxia.
基金Supported by Ningxia Natural Science Fund Program(NZ08155)Program for Tackling Key Problems in Science and Technology in Ningxia(KGX-12-09-02)~~
文摘A quantitative model is built and the historical variation of natural disasters is analyzed in this paper,by using materials as affected area(damaged area),affected population(dead and injured),casualty of livestock,collapsed houses(damaged houses),decrease of crops yield,economic loss(direct and indirect) and price index over the same period of Ningxia natural disasters(include drought,flood,gale and hail,frost,pest disasters and other disasters) during 1978-2007,and applying gray correlation analysis method.The long-term changes trend of natural disasters is analyzed by the application of the least squares method for linear trend,and the oscillation period is analyzed by using the maximum entropy statistical method.It is found that natural disasters have basically 2 to 3 years of variation period either in the whole region or in the individual regions;from the mid 1980s to the late 1990s,Ningxia is in an oscillation period with disasters attacked frequently in decadal and interannual scale under the background of climate;the increase of damage intensity of natural disasters slow down and tends to decrease since 2000.
基金the Open Project Program of the Breeding Base for State Key Laboratory of Land Degradation and Ecological Restoration of Northwestern China/Key Laboratory for Restoration and Reconstruction of Degraded Ecosystem in Northwestern China of Ministry of Education(2017KF004)the Ningxia Natural Science Foundation of Ningxia Hui Autonomous Region,China(2018AAC03002)。
文摘Frequent periods of drought conditions are known to limit plant performance,primary production,and ecosystem stability in arid and semi-arid desert steppe environments.Plants often avoid competition by shifting their water use seasonally,which affects the water-use patterns of dominant species as well as the composition and structure of plant communities.However,the water-use strategies of dominant herbaceous species,which grow under natural field conditions in the desert steppe region of Ningxia Hui Autonomous Region,China,are poorly known.Here,we explored the possible sources of water uptake and water-use efficiency(WUE)of three dominant herbaceous plant species(Stipa breviflora,Agropyron mongolicum,and Glycyrrhiza uralensis)in a native desert steppe in the semi-arid area of Ningxia through an analysis of multiple parameters,including(1)the stable isotopic oxygen and hydrogen(δ18O andδ2H)compositions of precipitation,soil water,and stem water,(2)the carbon isotope(13C)composition of leaves,and(3)the soil water contents,based on field sampling across varying water conditions from June to September,2017.Frequent small precipitation events replenished shallow soil water,whereas large events only percolated down to the deep soil layers.Changes in soil water availability affected the water-use patterns of plants.Generally,during light precipitation periods,the deep root system of G.uralensis accessed deeper(>80 cm)soil water,whereas S.breviflora and A.mongolicum,which only have shallow roots,primarily absorbed water from the shallow and middle soil layers.As precipitation increased,all three plant species primarily obtained water from the shallow soil layers.Variation in soil water uptake between the dry and wet seasons enabled plants to make better use of existing satoil water.In addition,theδ13C values of G.uralensis and S.breviflora were higher than those of A.mongolicum.Theδ13C values of the three plant species were significantly negatively correlated with soil water content.Therefore,G.uralensis and S.breviflora maintained a higher WUE through their conservative and water-saving strategies across the entire growing season.In contrast,A.mongolicum,with a relatively low WUE in the wet season but a high WUE in the dry season,exhibited a more flexible water-use strategy.The different water-use strategies of these dominant plant species demonstrated the mechanisms by which plant communities can respond to drought.
基金Under the auspices of Strategic Priority Research Program of Chinese Academy of Sciences(No.XDA05000000)National Natural Science Foundation of China(No.41271518)Sci-technology Project of Shaanxi Province(No.2013kw19-01)
文摘Grassland is a major carbon sink in the terrestrial ecosystem. The dynamics of grassland carbon stock profoundly influence the global carbon cycle. In the published literatures so far, however, there are limited studies on the long-term dynamics and influential factors of grassland carbon stock, including soil organic carbon. In this study, spatial-temporal substitution method was applied to explore the characteristics of Medicago sativa L. （alfalfa） grassland biomass carbon and soil organic carbon density （SOCD） in a loess hilly region with different growing years and management patterns. The results demonstrated that alfalfa was the mono-dominant community during the cutting period （viz. 0-10 year）. Community succession began after the abandonment of alfalfa grassland and then the important value of alfalfa in the community declined. The artificial alfalfa community abandoned for 30 years was replaced by the S. bungeana community. Accordingly, the biomass carbon density of the clipped alfalfa showed a significant increase over the time during 0-10 year. During 0-30 year, the SOCD from 0-100 cm of the soil layer of all 5 management patterns increased over time with a range between 5.300 ± 0.981 kg/m2 and 12.578 ± 0.863 kg/m2. The sloping croplands had the lowest SOCD at 5.300 ± 0.981 kg/m2 which was quite different from the abandoned grasslands growing for 30 years which exhibited the highest SOCD with 12.578 ± 0.863 kg/m2. The ecosystem carbon density of the grassland clipped for 2 years increased 0.1 kg/m2 compared with the sloping cropland, while that of the grassland clipped for 10 years substantially increased to 10.30 ± 1.26 kg/m2. Moreover, the ecosystem carbon density for abandoned grassland became 12.62± 0.50 kg/m2 at 30 years. The carbon density of the grassland undisturbed for l0 years was similar to that of the sloping cropland and the grassland clipped for 2 years. Different management patterns imposed great different effects on the accumulation of biomass carbon on artificial grasslands, whereas the ecosystem carbon density of the grassland showed a slight increase from the clipping to abandonment of grassland in general.
基金This study was supported by the National Key Research and Development Plan of China[Grant No.2016YFE0201900-02]the National Natural Science Foundation of China[Grant Nos.41575037 and 41205099]+1 种基金the National Basic Research Program of China[973 Program,Grant No.2014CB441403]Guizhou Province Scientific Research Joint Project[Grant No.G[2013]4001].
文摘Based on daily rainfall data from 26 station records,spatial and temporal variations in annual and seasonal precipitation of different rainfall intensities from 1961 to 2018 in Ningxia,China are investigated using the innovative trend analysis(ITA)method.The results show that annual precipitation increases on the northern plain but decreases in the southern mountainous area.The increase in regional annual precipitation is mainly due to an increase in weak precipitation,while the decrease in regional annual rainfall is a result of a reduction in heavy precipitation.Lowintensity precipitation shows an upward trend,while high-intensity precipitation shows a downward trend.The variation trend of extreme precipitation is more obvious.The contributions of different types of extreme precipitation vary by season.During spring,the increase in regional rainfall is mainly caused by the increase in heavy precipitation,while the decrease in regional precipitation is mainly caused by the decrease in weak precipitation.During summer and autumn,the increase in regional precipitation is caused by the increase in light precipitation,while the reduction in regional rainfall is caused by the decrease in heavy precipitation.This study provides support for water resources planning and addressing droughts and floods.
基金supported by the National Natural Science Foundation of China (40801004, 40671184)the Research Fund for the Doctoral Program of Higher Education (20070027019)
文摘Based on the analysis of the correlation between the tree-ring width of Pinus tabulaeformis and the climate factors in the western Hedong sandy land of Ningxia, a conversion equation between the annual precipitation and the tree-ring width since 1899 was reconstructed. The results of cross verification indicated that the conversion equation is stable and the reconstructed results are reliable. The result of reconstructed annual precipitation showed the remarkable fluctuation of precipitation and dry-to-wet variation before the 1940s. The smaller fluctuation and high frequent changes of precipitation occurred during the period of 1940s-1980s and after the 1980s the change trend of the precipitation became high periodic extent and low frequent. The study found that there were some coincidences with the climate change in Changling Mountains, Helan Mountains and the east of Qilian Mountains. The relatively dry periods in the beginning of 20th century, 1920s to 1930s, the end of the 20th century and 2004 to 2006 in the western Hedong sandy land of Ningxia accelerated the desertification, while the relatively humid period during the periods of the 1910s-1920s, 1930s-1940s and 1990s is favorable to prevent and control the desertification, and to weaken the climate warming and drying. The periods of annual precipitation variation in the western Hedong sandy land of Ningxia since 1899 are approximately 2-4 years, 5-7 years and 10 years.
