The fate of the terrestrial sediment supplied by rivers is a critical issue for understanding the patterns of Holocene environmental change on continental shelves. The East China Sea is a typical broad continental she...The fate of the terrestrial sediment supplied by rivers is a critical issue for understanding the patterns of Holocene environmental change on continental shelves. The East China Sea is a typical broad continental shelf with abundant sediment supply from large rivers. Here, a variety of sedimentary records were formed during the Holocene period. The sedimentary systems associated with these records have unique charac- teristics in terms of spatial distribution, material composition, deposition rate and the timing of deposition, which are related to active sediment transport processes induced by tides and waves, shelf circulations and sediment gravity flows. The sedimentary records thus formed are high resolution slices, i.e., each record has a temporal resolution of up to 10^-10-1 a, but only covers a limited part of the Holocene time. In terms of the spatial distribution, these records are scattered over a large area on the shelf. Further studies of these systems are required to understand the underlying process-product relationships. In particular, the mid- Holocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, as well as the Holocene mud deposits off the Zhejiang-Fujian coasts, should be investigated in terms of the material supply （from both seabed reworking during the sea level rise event and river discharges）, transport-accumulation processes, the sediment sequences and the future evolution of the sedimentary systems. Advanced numerical modeling techniques should be developed to meet the needs of these studies.展开更多
【目的】探究种植密度对菊芋块茎产量、植株光能截获及养分吸收转运特性的影响,确定适宜种植密度,为菊芋优化栽培种植及高产稳产提供理论依据。【方法】2019—2020年分别于河南省新乡市和南阳市布置菊芋密度效应田间试验。以“南芋1号...【目的】探究种植密度对菊芋块茎产量、植株光能截获及养分吸收转运特性的影响,确定适宜种植密度,为菊芋优化栽培种植及高产稳产提供理论依据。【方法】2019—2020年分别于河南省新乡市和南阳市布置菊芋密度效应田间试验。以“南芋1号”为供试材料,设置5个种植密度,分别为:D1(1.80×10^(4)株·hm^(-2))、D2(2.25×10^(4)株·hm^(-2))、D3(2.70×10^(4)株·hm^(-2))、D4(3.15×10^(4)株·hm^(-2))和D5(3.60×10^(4)株·hm^(-2))。于菊芋成熟期(mature period,MP)测试块茎产量,并分别于营养生长中期(medium the vegetative period,MVP)、营养生长末期(late the vegetative period,LVP)和开花期(flowering period,FP)测试地上部植株生物量和氮磷钾养分含量,分析计算菊芋植株养分积累与开花期、花后养分转运特性。同时于上述生育期测定菊芋不同叶层叶片SPAD值和冠层光分布。【结果】种植密度可显著影响菊芋块茎产量,2019和2020年两者间关系可分别用“线性+平台”和“一元二次方程”拟合,2 a适宜种植密度分别为3.15×10^(4)和3.24×10^(4)株·hm^(-2)。随种植密度增加,菊芋上层叶片SPAD值无明显差异,但随叶层下移,密度间叶片SPAD值差异性则显著增加,即密度越小,中、下层叶片SPAD值越高。菊芋冠层吸收性光合有效辐射量(APAR)和吸收系数(FPAR)则随密度增加而显著提高。试验点和密度处理双因素交互效应分析表明,试验点对菊芋块茎产量、叶片SPAD值、FPAR和APAR均有显著影响,试验处理对以上指标影响均达到显著效应;两因素交互作用仅对FPAR影响显著,对其他指标均无明显影响。此外,随种植密度增加,菊芋各生育期氮磷钾养分积累量则显著升高;开花期养分转运量逐步增加,转运率则逐步下降;花后养分转运量和养分转运率总体均呈升高趋势。【结论】适度种植可显著提高菊芋块茎产量,增强植株冠层光能截获与利用性能,提�展开更多
This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectr...This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectral indices (SI), and principal component analysis (PCA). To achieve our objectives, topographic attributes and profiles were retrieved from ASTER-V2 DEM. PCA and nine SI were derived from two Landsat-OLI images acquired before and after the flood-storm. The images data were atmospherically corrected, sensor radiometric drift calibrated, and geometric and topographic distortions rectified. For validation purposes, the acquired photos during the flood-storm, lithological and geological maps were used. The analysis of approximately 100 colour composite combinations in the RGB system permitted the selection of two combinations due to their potential for characterizing soil erosion classes and sediment accumulation. The first considers the “Intensity, NDWI and NMDI”, while the second associates form index (FI), brightness index (BI) and NDWI. These two combinations provide very good separating power between different levels of soil erosion and degradation. Moreover, the derived erosion risk and sediment accumulation map based on the selected spectral indices segmentation and topographic attributes and profiles illustrated the tendency of water accumulation in the landscape, and highlighted areas prone to both fast moving and pooling water. In addition, it demonstrated that the rainfall, the topographic morphology and the lithology are the major contributing factors for flash flooding, catastrophic inundation, and erosion risk in the study area. The runoff-water power delivers vulnerable topsoil and contributes strongly to the erosion process, and then transports soil material and sediment to the plain areas through waterpower and gravity. The originality of this research resides in its simplicity and rapidity to provide a solid basis strategy for regional policies to address the real causes of problem展开更多
基金a project of the Mega-Science Program supported by the Ministry of Science and Technology of China:"Land-ocean boundary processes and their impacts on the formation of the Yangtze deposition system" under contract No.2013CB956500
文摘The fate of the terrestrial sediment supplied by rivers is a critical issue for understanding the patterns of Holocene environmental change on continental shelves. The East China Sea is a typical broad continental shelf with abundant sediment supply from large rivers. Here, a variety of sedimentary records were formed during the Holocene period. The sedimentary systems associated with these records have unique charac- teristics in terms of spatial distribution, material composition, deposition rate and the timing of deposition, which are related to active sediment transport processes induced by tides and waves, shelf circulations and sediment gravity flows. The sedimentary records thus formed are high resolution slices, i.e., each record has a temporal resolution of up to 10^-10-1 a, but only covers a limited part of the Holocene time. In terms of the spatial distribution, these records are scattered over a large area on the shelf. Further studies of these systems are required to understand the underlying process-product relationships. In particular, the mid- Holocene coastal deposits on the Jiangsu coast, the early to middle Holocene sequences of the Hangzhou Bay, as well as the Holocene mud deposits off the Zhejiang-Fujian coasts, should be investigated in terms of the material supply （from both seabed reworking during the sea level rise event and river discharges）, transport-accumulation processes, the sediment sequences and the future evolution of the sedimentary systems. Advanced numerical modeling techniques should be developed to meet the needs of these studies.
文摘【目的】探究种植密度对菊芋块茎产量、植株光能截获及养分吸收转运特性的影响,确定适宜种植密度,为菊芋优化栽培种植及高产稳产提供理论依据。【方法】2019—2020年分别于河南省新乡市和南阳市布置菊芋密度效应田间试验。以“南芋1号”为供试材料,设置5个种植密度,分别为:D1(1.80×10^(4)株·hm^(-2))、D2(2.25×10^(4)株·hm^(-2))、D3(2.70×10^(4)株·hm^(-2))、D4(3.15×10^(4)株·hm^(-2))和D5(3.60×10^(4)株·hm^(-2))。于菊芋成熟期(mature period,MP)测试块茎产量,并分别于营养生长中期(medium the vegetative period,MVP)、营养生长末期(late the vegetative period,LVP)和开花期(flowering period,FP)测试地上部植株生物量和氮磷钾养分含量,分析计算菊芋植株养分积累与开花期、花后养分转运特性。同时于上述生育期测定菊芋不同叶层叶片SPAD值和冠层光分布。【结果】种植密度可显著影响菊芋块茎产量,2019和2020年两者间关系可分别用“线性+平台”和“一元二次方程”拟合,2 a适宜种植密度分别为3.15×10^(4)和3.24×10^(4)株·hm^(-2)。随种植密度增加,菊芋上层叶片SPAD值无明显差异,但随叶层下移,密度间叶片SPAD值差异性则显著增加,即密度越小,中、下层叶片SPAD值越高。菊芋冠层吸收性光合有效辐射量(APAR)和吸收系数(FPAR)则随密度增加而显著提高。试验点和密度处理双因素交互效应分析表明,试验点对菊芋块茎产量、叶片SPAD值、FPAR和APAR均有显著影响,试验处理对以上指标影响均达到显著效应;两因素交互作用仅对FPAR影响显著,对其他指标均无明显影响。此外,随种植密度增加,菊芋各生育期氮磷钾养分积累量则显著升高;开花期养分转运量逐步增加,转运率则逐步下降;花后养分转运量和养分转运率总体均呈升高趋势。【结论】适度种植可显著提高菊芋块茎产量,增强植株冠层光能截获与利用性能,提�
文摘This research deals with the characterization of areas associated with flash floods and erosion caused by severe rainfall storm and sediment transport and accumulation using topographic attributes and profiles, spectral indices (SI), and principal component analysis (PCA). To achieve our objectives, topographic attributes and profiles were retrieved from ASTER-V2 DEM. PCA and nine SI were derived from two Landsat-OLI images acquired before and after the flood-storm. The images data were atmospherically corrected, sensor radiometric drift calibrated, and geometric and topographic distortions rectified. For validation purposes, the acquired photos during the flood-storm, lithological and geological maps were used. The analysis of approximately 100 colour composite combinations in the RGB system permitted the selection of two combinations due to their potential for characterizing soil erosion classes and sediment accumulation. The first considers the “Intensity, NDWI and NMDI”, while the second associates form index (FI), brightness index (BI) and NDWI. These two combinations provide very good separating power between different levels of soil erosion and degradation. Moreover, the derived erosion risk and sediment accumulation map based on the selected spectral indices segmentation and topographic attributes and profiles illustrated the tendency of water accumulation in the landscape, and highlighted areas prone to both fast moving and pooling water. In addition, it demonstrated that the rainfall, the topographic morphology and the lithology are the major contributing factors for flash flooding, catastrophic inundation, and erosion risk in the study area. The runoff-water power delivers vulnerable topsoil and contributes strongly to the erosion process, and then transports soil material and sediment to the plain areas through waterpower and gravity. The originality of this research resides in its simplicity and rapidity to provide a solid basis strategy for regional policies to address the real causes of problem
