The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand b...The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion,particularly from the perspective of surface sediment grain size,are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities.This study focused on the surface sediments(topsoil of 0–3 cm depth)of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size.In March 2023,six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations(1,5,10,20,40,and 60 a)were selected as experimental plots,and one control sampling plot was set in an adjacent mobile sandy area without sand barriers.Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed.Results indicated a predominance of fine and medium sands in the surface sediments of the study area.The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments,increasing the average contents of very fine sand,silt,and clay by 30.82%,417.38%,and 381.52%,respectively.This trend became markedly pronounced a decade after the deployment of clay–sand barriers.The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity,the interception of sand flow,and the promotion of fine surface sediment particles.Coarser particles such as medium,coarse,and very coarse sands predominantly accumulated on the external side of the barriers,while finer particles such as fine and very fine sands concentrated in the upwind(northwest)region of the barriers.By contrast,the contents of finest particles such as silt and clay were higher in the downwind(southeast)region of the sampling plots.For the study area,the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control,with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification.The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.展开更多
格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提...格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提供的近20年的月时变重力场数据,以及EuropeanRemote Sensing(ERS-2)、Envisat和CryoSat-2等卫星测高数据,本文对比分析了2002年4月-2020年12月格陵兰冰盖质量变化特征。研究结果表明:(1)卫星重力点质量模型与卫星测高产品估计的质量变化趋势空间分布较为一致,均表明格陵兰冰盖边缘低海拔区域质量亏损严重而内部高原存在质量累积。(2) 2002-2020年格陵兰质量损失对全球平均海平面变化贡献为0.73±0.01mm·a^(-1)。(3)格陵兰冰盖西南部和西北部对海平面变化的贡献占格陵兰总贡献量的43.69%,为主要的海平面上升贡献区。(4)格陵兰冰盖流域尺度的分析表明,Goddard Space Flight Center(GSFC)点质量模型与卫星测高估计的结果更为一致。展开更多
The low biomass in environmental samples is a major challenge for microbial metagenomic studies. The amplification of a genomic DNA was frequently applied to meeting the minimum requirement of the DNA for a high-throu...The low biomass in environmental samples is a major challenge for microbial metagenomic studies. The amplification of a genomic DNA was frequently applied to meeting the minimum requirement of the DNA for a high-throughput next-generation-sequencing technology. Using a synthetic bacterial community, the amplification efficiency of the Multiple Annealing and Looping Based Amplification Cycles（MALBAC） kit that is originally developed to amplify the single-cell genomic DNA of mammalian organisms is examined. The DNA template of 10 pg in each reaction of the MALBAC amplification may generate enough DNA for Illumina sequencing. Using 10 pg and 100 pg templates for each reaction set, the MALBAC kit shows a stable and homogeneous amplification as indicated by the highly consistent coverage of the reads from the two amplified samples on the contigs assembled by the original unamplified sample. Although Genome Plex whole genome amplification kit allows one to generate enough DNA using 100 pg of template in each reaction, the minority of the mixed bacterial species is not linearly amplified. For both of the kits, the GC-rich regions of the genomic DNA are not efficiently amplified as suggested by the low coverage of the contigs with the high GC content. The high efficiency of the MALBAC kit is supported for the amplification of environmental microbial DNA samples, and the concerns on its application are also raised to bacterial species with the high GC content.展开更多
基金the National Natural Science Foundation of China(42230720,32160410,42167069)the Gansu Key Research and Development Program(22YF7FA078,GZTZ20240415)Gansu Province Forestry and Grassland Science and Technology Innovation Project(LCCX202303).
文摘The clay–sand barriers in Minqin desert area,China,represent a pioneering windbreak and sand fixation project with a venerable history of 60 a.However,studies on evaluating the long-term effectiveness of clay–sand barriers against aeolian erosion,particularly from the perspective of surface sediment grain size,are limited and thus insufficient to ascertain the protective impact of these barriers on regional aeolian activities.This study focused on the surface sediments(topsoil of 0–3 cm depth)of clay–sand barriers in Minqin desert area to explain their erosion resistance from the perspective of surface sediment grain size.In March 2023,six clay–sand barrier sampling plots with clay–sand barriers of different deployment durations(1,5,10,20,40,and 60 a)were selected as experimental plots,and one control sampling plot was set in an adjacent mobile sandy area without sand barriers.Surface sediment samples were collected from the topsoil of each sampling plot in the study area in April 2023 and sediment grain size characteristics were analyzed.Results indicated a predominance of fine and medium sands in the surface sediments of the study area.The deployment of clay–sand barriers cultivated a fine quality in grain size composition of the regional surface sediments,increasing the average contents of very fine sand,silt,and clay by 30.82%,417.38%,and 381.52%,respectively.This trend became markedly pronounced a decade after the deployment of clay–sand barriers.The effectiveness of clay–sand barriers in erosion resistance was manifested through reduced wind velocity,the interception of sand flow,and the promotion of fine surface sediment particles.Coarser particles such as medium,coarse,and very coarse sands predominantly accumulated on the external side of the barriers,while finer particles such as fine and very fine sands concentrated in the upwind(northwest)region of the barriers.By contrast,the contents of finest particles such as silt and clay were higher in the downwind(southeast)region of the sampling plots.For the study area,the deployment of clay–sand barriers remains one of the most cost-effective engineering solutions for aeolian erosion control,with sediment grain size parameters serving as quantitative indicators for the assessment of these barriers in combating desertification.The results of this study provide a theoretical foundation for the construction of windbreak and sand fixation systems and the optimization of artificial sand control projects in arid desert areas.
文摘格陵兰冰盖全部融化将导致全球海平面上升7m,因此准确估计格陵兰冰盖质量变化过程对理解其对全球气候变化响应和反馈作用具有重要意义。基于Gravity Recovery and Climate Experiment(GRACE)卫星及后继卫星GRACE-FollowOn(GRACE-FO)提供的近20年的月时变重力场数据,以及EuropeanRemote Sensing(ERS-2)、Envisat和CryoSat-2等卫星测高数据,本文对比分析了2002年4月-2020年12月格陵兰冰盖质量变化特征。研究结果表明:(1)卫星重力点质量模型与卫星测高产品估计的质量变化趋势空间分布较为一致,均表明格陵兰冰盖边缘低海拔区域质量亏损严重而内部高原存在质量累积。(2) 2002-2020年格陵兰质量损失对全球平均海平面变化贡献为0.73±0.01mm·a^(-1)。(3)格陵兰冰盖西南部和西北部对海平面变化的贡献占格陵兰总贡献量的43.69%,为主要的海平面上升贡献区。(4)格陵兰冰盖流域尺度的分析表明,Goddard Space Flight Center(GSFC)点质量模型与卫星测高估计的结果更为一致。
基金The Strategic Priority Research Program of the Chinese Academy of Sciences (CAS) under contract Nos XDB06010100 and XDB06010200the National Basic Research Program (973 Program) of China under contract No.2012CB417304+2 种基金the National Natural Science Foundation of China under contract No.U1301232the Sanya Institute of Deep Sea Science and Engineering under contract Nos SIDSSE-201206,SIDSSE-BR-201303 and SIDSSE-201305the award from King Abdullah University of Science and Technology under contract No.SAC0040/UK-C0016
文摘The low biomass in environmental samples is a major challenge for microbial metagenomic studies. The amplification of a genomic DNA was frequently applied to meeting the minimum requirement of the DNA for a high-throughput next-generation-sequencing technology. Using a synthetic bacterial community, the amplification efficiency of the Multiple Annealing and Looping Based Amplification Cycles（MALBAC） kit that is originally developed to amplify the single-cell genomic DNA of mammalian organisms is examined. The DNA template of 10 pg in each reaction of the MALBAC amplification may generate enough DNA for Illumina sequencing. Using 10 pg and 100 pg templates for each reaction set, the MALBAC kit shows a stable and homogeneous amplification as indicated by the highly consistent coverage of the reads from the two amplified samples on the contigs assembled by the original unamplified sample. Although Genome Plex whole genome amplification kit allows one to generate enough DNA using 100 pg of template in each reaction, the minority of the mixed bacterial species is not linearly amplified. For both of the kits, the GC-rich regions of the genomic DNA are not efficiently amplified as suggested by the low coverage of the contigs with the high GC content. The high efficiency of the MALBAC kit is supported for the amplification of environmental microbial DNA samples, and the concerns on its application are also raised to bacterial species with the high GC content.
