By using soil erosion maps of four different time periods and a digital elevation model (DEM), in combination withthe remote sensing and GIS technologies, soil erosion dynamics in Xingguo County of Jiangxi Province in...By using soil erosion maps of four different time periods and a digital elevation model (DEM), in combination withthe remote sensing and GIS technologies, soil erosion dynamics in Xingguo County of Jiangxi Province in South Chinawere analyzed on both temporal and spatial scales in soils of different parent materials, altitudes and slopes. The resultsshowed that from 1958 to 2000 severe soil erosion was coming under control with a decreasing percentage of the land undersevere erosion. It was also found that the soils developed from Quaternary red clay, granite and purple shale were moresusceptible to soil erosion and that areas sitting between 200 to 500 m in altitude with a slope less than 3° or between7° to 20° where human activities were frequent remained to be zones where soil erosion was most likely to occur. Theseareas deserve special attention in monitoring and controlling.展开更多
Excess phosphorus (P) from agricultural soils contributes to eutrophication in water bodies.Samples (n=60) were taken from sites where rice paddies have been converted to vegetable fields for 0,< 10,10-20,and > ...Excess phosphorus (P) from agricultural soils contributes to eutrophication in water bodies.Samples (n=60) were taken from sites where rice paddies have been converted to vegetable fields for 0,< 10,10-20,and > 20 years and analyzed for five inorganic P (Pi) fractions,three organic P(Po) fractions,and several soil parameters to investigate how land use conversion affects Pi and Po fractions in a peri-urban area of China with soils characteristic of many agricultural areas of Asia.Significant increases of 33,281,293,and 438 mg kg 1 were found for soluble and loosely bound Pi (SL-Pi),aluminum-bound Pi (Al-Pi),calcium-bound P i (Ca-Pi),and iron-bound Pi (Fe-Pi),respectively,after conversion from rice paddies to vegetable fields.Most of the increase in Pi was in the form of Fe-Pi,which increased from 8% of total P (TP) on paddy soil to 31% on the soil with > 20-year vegetable cultivation,followed by Al-Pi,which increased from 2% to 19% of TP.For Po fractions,there was no significant change in P concentrations.The conversion of land use from paddy fields to high intensity vegetable fields was causing significant changes in soil P fractions.Management practices were causing a buildup of soil P,primarily in the Fe-Pi fraction,followed by Ca-Pi and Al-Pi fractions.If current trends continue,a 30%-70% increase in TP could be expected in the next 20 years.Farmers in the area should reduce P application and use to maximize P uptake.展开更多
目的比较股骨近端防旋髓内钉(proximal femoral nail anti-rotation,PFNA)与DHS动力髋螺钉(dynamic hip system,DHS)治疗股骨粗隆间骨折的疗效差异.方法抽选64例股骨粗隆间不稳定性骨折患者,患者入院后随机分为观察组和对照组,分别予以...目的比较股骨近端防旋髓内钉(proximal femoral nail anti-rotation,PFNA)与DHS动力髋螺钉(dynamic hip system,DHS)治疗股骨粗隆间骨折的疗效差异.方法抽选64例股骨粗隆间不稳定性骨折患者,患者入院后随机分为观察组和对照组,分别予以股骨近端防旋髓内钉和解剖钢板进行治疗,对2组患者术后疗效、并发症发生率以及髋关节功能进行调查.结果观察组一期愈合24例,对照组15例;观察组二期愈合10例,对照组二期愈合7例,2组愈合率比较存在明显差异P<0.05.观察组患者痊愈的24例,对照组患者痊愈的15例;对照组患者病情改善的7例,观察组患者病情改善的10例,2组比较存在明显差异,P<0.05.观察组患者髋关节功能评分为(90.5±6.7)分,对照组为(79.5±7.9)分,2组比较存在明显差异,P<0.05.观察组并发症发生率为3.1%,对照组患者并发症发生率为25.0%,比较存在明显差异P<0.05.结论股骨近端防旋髓内钉能够更好地改善患者病情,恢复髋关节功能.展开更多
Soil depth is critical for eco-hydrological modeling,carbon storage calculation and land evaluation.However,its spatial variation is poorly understood and rarely mapped.With a limited number of sparse samples,how to p...Soil depth is critical for eco-hydrological modeling,carbon storage calculation and land evaluation.However,its spatial variation is poorly understood and rarely mapped.With a limited number of sparse samples,how to predict soil depth in a large area of complex landscapes is still an issue.This study constructed an ensemble machine learning model,i.e.,quantile regression forest,to quantify the relationship between soil depth and environmental conditions.The model was then combined with a rich set of environmental covariates to predict spatial variation of soil depth and straightforwardly estimate the associated predictive uncertainty in the 140000 km^(2)Heihe River basin of northwestern China.A total of 275 soil depth observation points and 26 covariates were used.The results showed a model predictive accuracy with coefficient of determination(R)of 0.587 and root mean square error(RMSE)of 2.98 cm(square root scale),i.e.,almost 60% of soil depth variation explained.The resulting soil depth map clearly exhibited regional patterns as well as local details.Relatively deep soils occurred in low lying landscape positions such as valley bottoms and plains while shallow soils occurred in high and steep landscape positions such as hillslopes,ridges and terraces.The oases had much deeper soils than outside semi-desert areas,the middle of an alluvial plain had deeper soils than its margins,and the middle of a lacustrine plain had shallower soils than its margins.Large predictive uncertainty mainly occurred in areas with a lack of soil survey points.Both pedogenic and geomorphic processes contributed to the shaping of soil depth pattern of this basin but the latter was dominant.This findings may be applicable to other similar basins in cold and arid regions around the world.展开更多
LiNi0.5Mn1.504 prepared by a spray drying method was re-treated in N2 at 500, 600 and 700℃, respec- tively. Their structural and electrochemical properties were studied by means of Fourier transform infrared（FTIR）,...LiNi0.5Mn1.504 prepared by a spray drying method was re-treated in N2 at 500, 600 and 700℃, respec- tively. Their structural and electrochemical properties were studied by means of Fourier transform infrared（FTIR）, X-ray diffraction（XRD）, and charge-discharge tests. The space group of the LiNi0.sMnl.504 transforms from P4332 to Fd3m at an annealing temperature of 700℃. The electrochemical characteristics of the treated samples are closely related to the annealing temperature. The sample treated in N2 at 500℃ shows both an improved rate capability and cyclic performance at a high temperature compared with the as-prepared sample, while the sample treated in N2 at 700℃ shows dramatically decrease in its reversible capacity.展开更多
Alfalfa cropping has been considered an efficient method of increasing soil fertility.Usually nitrogen increase in root nodules is considered to be the major beneficial effect.A 21-year time series (five sampling peri...Alfalfa cropping has been considered an efficient method of increasing soil fertility.Usually nitrogen increase in root nodules is considered to be the major beneficial effect.A 21-year time series (five sampling periods) of alfalfa cultivation plots on a loess soil,initially containing illite and chlorite,in Lanzhou of northwestern China was selected to investigate the relationships among alfalfa cropping,soil potassium (K) content and soil clay minerals.The results indicated that soil K significantly accumulated after cropping,with a peak value at about 15 years,and decreased afterwards.The accumulated K was associated with the K increase in the well-crystallized illite,which was not extracted by the traditional laboratory K extraction methods in assessing bioavailability.The steep decline in soil K content after 15-year cropping was in accord with the observed fertility loss in the alfalfa soil.Plant biomass productivity peaked at near 9 years of culture,whereas soil K and clay minerals continued to increase until cropping for 15 years.This suggested that K increased in the topsoil came from the deep root zone.Thus alfalfa continued to store K in clays even after peak production occurred.Nitrogen did not follow these trends,showing a general decline compared with the native prairie soils that had not been cropped.Therefore,the traditional alfalfa cropping can increase K content in the topsoil.展开更多
基金the National Natural Science Foundation of China (No. 40471081), the Innovation Programme ofChinese Academy of Sciences (No. KZCX3-SW-422), and the Canadian International Development Agency, Canada.
文摘By using soil erosion maps of four different time periods and a digital elevation model (DEM), in combination withthe remote sensing and GIS technologies, soil erosion dynamics in Xingguo County of Jiangxi Province in South Chinawere analyzed on both temporal and spatial scales in soils of different parent materials, altitudes and slopes. The resultsshowed that from 1958 to 2000 severe soil erosion was coming under control with a decreasing percentage of the land undersevere erosion. It was also found that the soils developed from Quaternary red clay, granite and purple shale were moresusceptible to soil erosion and that areas sitting between 200 to 500 m in altitude with a slope less than 3° or between7° to 20° where human activities were frequent remained to be zones where soil erosion was most likely to occur. Theseareas deserve special attention in monitoring and controlling.
基金Project supported by the National Science & Technology Pillar Program of China during the Eleventh Five-Year Plan Period (No. 2008BADA7B02)the National Natural Science Foundation of China (No. 40773075)the Natural Science Foundation of Jiangsu Province,China (No. BK2007262)
文摘Excess phosphorus (P) from agricultural soils contributes to eutrophication in water bodies.Samples (n=60) were taken from sites where rice paddies have been converted to vegetable fields for 0,< 10,10-20,and > 20 years and analyzed for five inorganic P (Pi) fractions,three organic P(Po) fractions,and several soil parameters to investigate how land use conversion affects Pi and Po fractions in a peri-urban area of China with soils characteristic of many agricultural areas of Asia.Significant increases of 33,281,293,and 438 mg kg 1 were found for soluble and loosely bound Pi (SL-Pi),aluminum-bound Pi (Al-Pi),calcium-bound P i (Ca-Pi),and iron-bound Pi (Fe-Pi),respectively,after conversion from rice paddies to vegetable fields.Most of the increase in Pi was in the form of Fe-Pi,which increased from 8% of total P (TP) on paddy soil to 31% on the soil with > 20-year vegetable cultivation,followed by Al-Pi,which increased from 2% to 19% of TP.For Po fractions,there was no significant change in P concentrations.The conversion of land use from paddy fields to high intensity vegetable fields was causing significant changes in soil P fractions.Management practices were causing a buildup of soil P,primarily in the Fe-Pi fraction,followed by Ca-Pi and Al-Pi fractions.If current trends continue,a 30%-70% increase in TP could be expected in the next 20 years.Farmers in the area should reduce P application and use to maximize P uptake.
文摘目的比较股骨近端防旋髓内钉(proximal femoral nail anti-rotation,PFNA)与DHS动力髋螺钉(dynamic hip system,DHS)治疗股骨粗隆间骨折的疗效差异.方法抽选64例股骨粗隆间不稳定性骨折患者,患者入院后随机分为观察组和对照组,分别予以股骨近端防旋髓内钉和解剖钢板进行治疗,对2组患者术后疗效、并发症发生率以及髋关节功能进行调查.结果观察组一期愈合24例,对照组15例;观察组二期愈合10例,对照组二期愈合7例,2组愈合率比较存在明显差异P<0.05.观察组患者痊愈的24例,对照组患者痊愈的15例;对照组患者病情改善的7例,观察组患者病情改善的10例,2组比较存在明显差异,P<0.05.观察组患者髋关节功能评分为(90.5±6.7)分,对照组为(79.5±7.9)分,2组比较存在明显差异,P<0.05.观察组并发症发生率为3.1%,对照组患者并发症发生率为25.0%,比较存在明显差异P<0.05.结论股骨近端防旋髓内钉能够更好地改善患者病情,恢复髋关节功能.
基金supported by the National Natural Science Foundation of China(41130530,91325301 and 42071072)。
文摘Soil depth is critical for eco-hydrological modeling,carbon storage calculation and land evaluation.However,its spatial variation is poorly understood and rarely mapped.With a limited number of sparse samples,how to predict soil depth in a large area of complex landscapes is still an issue.This study constructed an ensemble machine learning model,i.e.,quantile regression forest,to quantify the relationship between soil depth and environmental conditions.The model was then combined with a rich set of environmental covariates to predict spatial variation of soil depth and straightforwardly estimate the associated predictive uncertainty in the 140000 km^(2)Heihe River basin of northwestern China.A total of 275 soil depth observation points and 26 covariates were used.The results showed a model predictive accuracy with coefficient of determination(R)of 0.587 and root mean square error(RMSE)of 2.98 cm(square root scale),i.e.,almost 60% of soil depth variation explained.The resulting soil depth map clearly exhibited regional patterns as well as local details.Relatively deep soils occurred in low lying landscape positions such as valley bottoms and plains while shallow soils occurred in high and steep landscape positions such as hillslopes,ridges and terraces.The oases had much deeper soils than outside semi-desert areas,the middle of an alluvial plain had deeper soils than its margins,and the middle of a lacustrine plain had shallower soils than its margins.Large predictive uncertainty mainly occurred in areas with a lack of soil survey points.Both pedogenic and geomorphic processes contributed to the shaping of soil depth pattern of this basin but the latter was dominant.This findings may be applicable to other similar basins in cold and arid regions around the world.
文摘LiNi0.5Mn1.504 prepared by a spray drying method was re-treated in N2 at 500, 600 and 700℃, respec- tively. Their structural and electrochemical properties were studied by means of Fourier transform infrared（FTIR）, X-ray diffraction（XRD）, and charge-discharge tests. The space group of the LiNi0.sMnl.504 transforms from P4332 to Fd3m at an annealing temperature of 700℃. The electrochemical characteristics of the treated samples are closely related to the annealing temperature. The sample treated in N2 at 500℃ shows both an improved rate capability and cyclic performance at a high temperature compared with the as-prepared sample, while the sample treated in N2 at 700℃ shows dramatically decrease in its reversible capacity.
基金Supported by the National Basic Research Program (973 Program) of China (No. 2007CB407206)the Knowledge Innovation Program of the Chinese Academy of Sciences (No. KZCX2-YW-409)the National Natural Science Foundation of China (No. 40771091)
文摘Alfalfa cropping has been considered an efficient method of increasing soil fertility.Usually nitrogen increase in root nodules is considered to be the major beneficial effect.A 21-year time series (five sampling periods) of alfalfa cultivation plots on a loess soil,initially containing illite and chlorite,in Lanzhou of northwestern China was selected to investigate the relationships among alfalfa cropping,soil potassium (K) content and soil clay minerals.The results indicated that soil K significantly accumulated after cropping,with a peak value at about 15 years,and decreased afterwards.The accumulated K was associated with the K increase in the well-crystallized illite,which was not extracted by the traditional laboratory K extraction methods in assessing bioavailability.The steep decline in soil K content after 15-year cropping was in accord with the observed fertility loss in the alfalfa soil.Plant biomass productivity peaked at near 9 years of culture,whereas soil K and clay minerals continued to increase until cropping for 15 years.This suggested that K increased in the topsoil came from the deep root zone.Thus alfalfa continued to store K in clays even after peak production occurred.Nitrogen did not follow these trends,showing a general decline compared with the native prairie soils that had not been cropped.Therefore,the traditional alfalfa cropping can increase K content in the topsoil.
