The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carrie...The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.展开更多
基于LiDAR和SLAM(simultaneous localization and mapping)的LeGO-LOAM算法在低分辨率的LiDAR设备上,由于LiDAR数据的运动畸变、采样的地面数据稀疏等问题,存在重力矢量漂移现象和严重的高程估计误差。为了改善这一点,LeGO-LOAM改进算...基于LiDAR和SLAM(simultaneous localization and mapping)的LeGO-LOAM算法在低分辨率的LiDAR设备上,由于LiDAR数据的运动畸变、采样的地面数据稀疏等问题,存在重力矢量漂移现象和严重的高程估计误差。为了改善这一点,LeGO-LOAM改进算法引入了一种LiDAR和IMU(inertial measurement unit)紧耦合的方式。通过IMU估计运动状态,消除LiDAR数据的运动畸变,并使用IMU数据构建联合优化函数,约束位置姿态估计的重力方向。实验结果表明,这种方法有效抑制了LeGO-LOAM算法的重力矢量漂移,高程估计精度和高速状态下的定位精度均有显著提升。展开更多
Wind erosion is a geomorphic process in arid and semi-arid areas and has substantial implications for regional climate and desertification.In the Columbia Plateau of northwestern United States,the emissions from fine ...Wind erosion is a geomorphic process in arid and semi-arid areas and has substantial implications for regional climate and desertification.In the Columbia Plateau of northwestern United States,the emissions from fine particles of loessial soils often contribute to the exceedance of inhalable particulate matter(PM)with an aerodynamic diameter of 10μm or less(PM10)according to the air quality standards.However,little is known about the threshold friction velocity(TFV)for particles of different sizes that comprise these soils.In this study,soil samples of two representative soil types(Warden sandy loam and Ritzville silt loam)collected from the Columbia Plateau were sieved to seven particle size fractions,and an experiment was then conducted to determine the relationship between TFV and particle size fraction.The results revealed that soil particle size significantly affected the initiation of soil movement and TFV;TFV ranged 0.304-0.844 and 0.249-0.739 m/s for different particle size fractions of Ritzville silt loam and Warden sandy loam,respectively.PM10 and total suspended particulates(TSP)emissions from a bed of 63-90μm soil particles were markedly higher for Warden sandy loam than for Ritzville silt loam.Together with the lower TFV of Warden sandy loam,dust emissions from fine particles(<100μm in diameter)of Warden sandy loam thus may be a main contributor to dust in the region's atmosphere,since the PM10 emissions from the soil erosion surfaces and its ensuing suspension within the atmosphere constitute an essential process of soil erosion in the Columbia Plateau.Developing and implementing strategic land management practices on sandy loam soils is therefore necessary to control dust emissions in the Columbia Plateau.展开更多
Low quality water has been widely used for irrigation all over the world due to water shortage.However,the use of low quality water may cause accumulation of salt in root-zone soils,resulting in poor nitrogen utilizat...Low quality water has been widely used for irrigation all over the world due to water shortage.However,the use of low quality water may cause accumulation of salt in root-zone soils,resulting in poor nitrogen utilization by crops.The objective of the present study was to investigate the effects of sodium chloride(NaCl)on mineralization and nitrification of soils in the North China Plain(NCP).The experiments were conducted with laboratory incubators at 30℃.Five levels of NaCl-salt concentrations 0%,2%,3%,5%and 8%in the added solutions were used in the soil samples collected from NCP.The mineralization at NaCl-salt concentration lower than 3%was not significantly different from that of the control,whereas,significant inhibition of mineralization was found in the treatments with NaCl-salt concentration higher than 3%.The inhibition of mineralization was attributed to the retardation of nitrification in relatively high salt content because ammonification was not depressed by the added NaCl salt.The gas losses and nitrification were found decreasing with the increase in salinity.It was also found that the nitrification was more sensitive to salinity than the mineralization.Nitrification of soil samples was inhibited by 44.72%,57.87%,and 83.64%compared with the control after 38 days of incubation at NaCl-salt concentrations of 3%,5%and 8%,respectively.The time dependence of both the mineralization and nitrification can be fitted into a first-order kinetic model.The rate constant of mineralization and nitrification decreased exponentially with the salt content in the soils.The results of the present research may provide some scientific implications for the use of saline water or treated sewage water in the farming regions of the NCP.展开更多
基金financed by the National Natural Science Foundation of China(41301345,41101284)。
文摘The soil type is a key factor influencing N(nitrogen)cycling in soil;however,gross N transformations and N_(2)O emission sources are still poorly understood.In this study,a laboratory 15N tracing experiment was carried out at 60%WHC(water holding capacity)and 25℃to evaluate the gross N transformation rates and N_(2)O emission pathways in sandy loam and silt loam soils in a semi-arid region of Heilongjiang Province,China.The results showed that the gross rates of N mineralization,immobilization,and nitrification were 3.60,1.90,and 5.63 mg N/(kg·d)in silt loam soil,respectively,which were 3.62,4.26,and 3.13 times those in sandy loam soil,respectively.The ratios of the gross nitrification rate to the ammonium immobilization rate(n/ia)in sandy loam soil and silt loam soil were all higher than 1.00,whereas the n/ia in sandy loam soil(4.36)was significantly higher than that in silt loam soil(3.08).This result indicated that the ability of sandy loam soil to release and conserve the available N was relatively poor in comparison with silt loam soil,and the relatively strong nitrification rate compared to the immobilization rate may lead to N loss through NO_(3)–leaching.Under aerobic conditions,both nitrification and denitrification made contributions to N_(2)O emissions.Nitrification was the dominant pathway leading to N_(2)O production in soils and was responsible for 82.0%of the total emitted N_(2)O in sandy loam soil,which was significantly higher than that in silt loam soil(71.7%).However,the average contribution of denitrification to total N_(2)O production in sandy loam soil was 17.9%,which was significantly lower than that in silt loam soil(28.3%).These results are valuable for developing reasonable fertilization management and proposing effective greenhouse gas mitigation strategies in different soil types in semiarid regions.
基金Basic Research Funds for Colleges and Universities directly under the Inner Mongolia Autonomous Region:Desert Ecosystem Protection and Restoration Innovation Team(BR 22-13-03).
文摘Wind erosion is a geomorphic process in arid and semi-arid areas and has substantial implications for regional climate and desertification.In the Columbia Plateau of northwestern United States,the emissions from fine particles of loessial soils often contribute to the exceedance of inhalable particulate matter(PM)with an aerodynamic diameter of 10μm or less(PM10)according to the air quality standards.However,little is known about the threshold friction velocity(TFV)for particles of different sizes that comprise these soils.In this study,soil samples of two representative soil types(Warden sandy loam and Ritzville silt loam)collected from the Columbia Plateau were sieved to seven particle size fractions,and an experiment was then conducted to determine the relationship between TFV and particle size fraction.The results revealed that soil particle size significantly affected the initiation of soil movement and TFV;TFV ranged 0.304-0.844 and 0.249-0.739 m/s for different particle size fractions of Ritzville silt loam and Warden sandy loam,respectively.PM10 and total suspended particulates(TSP)emissions from a bed of 63-90μm soil particles were markedly higher for Warden sandy loam than for Ritzville silt loam.Together with the lower TFV of Warden sandy loam,dust emissions from fine particles(<100μm in diameter)of Warden sandy loam thus may be a main contributor to dust in the region's atmosphere,since the PM10 emissions from the soil erosion surfaces and its ensuing suspension within the atmosphere constitute an essential process of soil erosion in the Columbia Plateau.Developing and implementing strategic land management practices on sandy loam soils is therefore necessary to control dust emissions in the Columbia Plateau.
基金The project was supported by the National Natural Science Foundation of China(grant numbers:50639040,50779067)the Chinese State High-Tech“863”Program(grant number:2006AA100207)the Program for New Century Excellent Talents in University(grant number:NCET-05-0125).
文摘Low quality water has been widely used for irrigation all over the world due to water shortage.However,the use of low quality water may cause accumulation of salt in root-zone soils,resulting in poor nitrogen utilization by crops.The objective of the present study was to investigate the effects of sodium chloride(NaCl)on mineralization and nitrification of soils in the North China Plain(NCP).The experiments were conducted with laboratory incubators at 30℃.Five levels of NaCl-salt concentrations 0%,2%,3%,5%and 8%in the added solutions were used in the soil samples collected from NCP.The mineralization at NaCl-salt concentration lower than 3%was not significantly different from that of the control,whereas,significant inhibition of mineralization was found in the treatments with NaCl-salt concentration higher than 3%.The inhibition of mineralization was attributed to the retardation of nitrification in relatively high salt content because ammonification was not depressed by the added NaCl salt.The gas losses and nitrification were found decreasing with the increase in salinity.It was also found that the nitrification was more sensitive to salinity than the mineralization.Nitrification of soil samples was inhibited by 44.72%,57.87%,and 83.64%compared with the control after 38 days of incubation at NaCl-salt concentrations of 3%,5%and 8%,respectively.The time dependence of both the mineralization and nitrification can be fitted into a first-order kinetic model.The rate constant of mineralization and nitrification decreased exponentially with the salt content in the soils.The results of the present research may provide some scientific implications for the use of saline water or treated sewage water in the farming regions of the NCP.
