The spatial distribution and seasonal variations of the hypoxic zone in the eastern equatorial Indian Ocean were investigated using survey data collected from four cruises from 2013 to 2018.Results showed that hypoxic...The spatial distribution and seasonal variations of the hypoxic zone in the eastern equatorial Indian Ocean were investigated using survey data collected from four cruises from 2013 to 2018.Results showed that hypoxic zone occurred all year round in the eastern equatorial Indian Ocean,and it spread southward in the shape of a double tongue at two depths with one at subsurface centered at a depth of 150 m and the other in intermediate water centered at a depth of 800 m.The southward expansion and maximum thickness of the hypoxic zone were greatest in the spring inter-monsoon and least in the summer monsoon.The hypoxic zone originated from the southward expansion of the hypoxic water in the Bay of Bengal and its spatial distribution was driven by southward output flux of mid-deep(100–1000 m)hypoxic water from the Bay of Bengal.The hypoxia southward expansion was blocked near the equator in the subsurface layer,because of mixing with multiple zonal circulations(e.g.,Wyrtki Jets and the equatorial undercurrent),which meant that the hypoxic zone extended over a smaller area than in the intermediate water.These new findings will contribute to an improved understanding of the hypoxic zone and will contribute to circulation research,particularly about intermediate circulation in the eastern equatorial Indian Ocean.展开更多
Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone （ATE） of Taihu Lake were investigated, and the relations among N, P, ORP （oxidation reduction potential）, TOC, root sy...Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone （ATE） of Taihu Lake were investigated, and the relations among N, P, ORP （oxidation reduction potential）, TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON （dissolved organic nitrogen） and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^＋-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^＋-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.展开更多
山地植被垂直变化和分布历来是山地生态学研究的重点内容。本文从文献计量统计和文献分析两个方面,对山地植被的垂直分布格局研究进展进行了述评。文献统计分析主要基于CNKI和Web of Science数据库平台,检索了该研究领域1915年1月至2020...山地植被垂直变化和分布历来是山地生态学研究的重点内容。本文从文献计量统计和文献分析两个方面,对山地植被的垂直分布格局研究进展进行了述评。文献统计分析主要基于CNKI和Web of Science数据库平台,检索了该研究领域1915年1月至2020年12月的国内外期刊论文,分析了山地植被垂直格局的研究历程、现状、进展和趋势。结果表明:国内外研究的文献、作者、国家和机构数量均呈增长趋势,全球范围的研究主要涵盖了美国、德国、中国、西班牙和法国等85个国家,共计34.7%的文献集中在25个主要期刊。基于CiteSpace进行文献关键词共现聚类,分析了国内外山地植被垂直分布的热点领域,并对理论与假说、研究方法和主要研究领域等进行了述评。山地植被垂直格局历经了从单因子描述、多因子分析到机理和假说的求证,代表性理论包括:时间学说、空间异质性学说、竞争共存理论、中性理论及生态位理论等;从传统研究方法、数量分类与环境解释、遥感影像信息技术、模型及数字信息技术等进行了研究方法概述;并对热点研究领域进行了分析和述评,主要包括:山地植被垂直分布与驱动因素、山地植被生产力垂直变化、植物群落的谱系结构、基于生态位理论的植被分布预测等。总之,在全球气候变化背景下,山地植被及生态系统响应敏感且变化剧烈,山地植被对气候变化的响应、植被垂直带谱的数字信息化、水土耦合下的山地生态循环与生态系统服务等领域受到更广泛的重视;多尺度、多学科融合是本领域研究的发展趋势。展开更多
基金supported by the National Natural Science Foundation of China(No.41806099)the Global Change and Air-Sea Interaction Project of China(No.GASI-04-HYST-06).
文摘The spatial distribution and seasonal variations of the hypoxic zone in the eastern equatorial Indian Ocean were investigated using survey data collected from four cruises from 2013 to 2018.Results showed that hypoxic zone occurred all year round in the eastern equatorial Indian Ocean,and it spread southward in the shape of a double tongue at two depths with one at subsurface centered at a depth of 150 m and the other in intermediate water centered at a depth of 800 m.The southward expansion and maximum thickness of the hypoxic zone were greatest in the spring inter-monsoon and least in the summer monsoon.The hypoxic zone originated from the southward expansion of the hypoxic water in the Bay of Bengal and its spatial distribution was driven by southward output flux of mid-deep(100–1000 m)hypoxic water from the Bay of Bengal.The hypoxia southward expansion was blocked near the equator in the subsurface layer,because of mixing with multiple zonal circulations(e.g.,Wyrtki Jets and the equatorial undercurrent),which meant that the hypoxic zone extended over a smaller area than in the intermediate water.These new findings will contribute to an improved understanding of the hypoxic zone and will contribute to circulation research,particularly about intermediate circulation in the eastern equatorial Indian Ocean.
基金Project supported by the Hi-Tech Research and Development Program (863) of China(No.2002AA601013).
文摘Vertical and temporal distributions of N and P in soil solution in aquatic-terrestrial ecotone （ATE） of Taihu Lake were investigated, and the relations among N, P, ORP （oxidation reduction potential）, TOC, root system biomass and microorganism were studied. As a whole, significant declines in TN, NO3^--N, DON （dissolved organic nitrogen） and TP concentration in soil solution have occurred with increase of the depth, and reached their minima at 60 cm depth, except for NH4^＋-N, which increased with depth. The concentration of TP increased gradually from spring to winter in the topsoil, the maximum 0.08 mg/L presented in the winter while the minimum 0.03 mg/L in spring. In the deeper layer, the concentration value of TP fluctuated little. As for the NO3^--N, its seasonal variation was significant at 20 cm depth, its concentration increased gradually from spring to autumn, and decreased markedly in winter. Vertical and temporal distribution of DON is contrary to that of NO3^--N. The results also show that the variation of N and P in the percolate between adjacent layers is obviously different. The vertical variation ofTN, TP, NO3^--N, NH4^＋-N and DON is significant, of which the variation coefficient of NO3^--N along the depth reaches 100.23%, the highest; while the variation coefficient of DON is 41.14%, the smallest. The results of correlation analysis show that the concentration of nitrogen and phosphorus correlate significantly with TOC, ORP, root biomass and counts of nitrifying bacteria. Most nutrients altered much from 20 to 40 cm along the depth. However, DON changed more between 60 and 80 cm. Results show that soil of 0-60 cm depth is active rhizoplane, with strong capability to remove the nitrogen and phosphorus in ATE. It may suggest that there exists the optimum ecological efficiency in the depth of above 60 cm in reed wetland. This will be very significant for ecological restoration and reestablishment.
文摘山地植被垂直变化和分布历来是山地生态学研究的重点内容。本文从文献计量统计和文献分析两个方面,对山地植被的垂直分布格局研究进展进行了述评。文献统计分析主要基于CNKI和Web of Science数据库平台,检索了该研究领域1915年1月至2020年12月的国内外期刊论文,分析了山地植被垂直格局的研究历程、现状、进展和趋势。结果表明:国内外研究的文献、作者、国家和机构数量均呈增长趋势,全球范围的研究主要涵盖了美国、德国、中国、西班牙和法国等85个国家,共计34.7%的文献集中在25个主要期刊。基于CiteSpace进行文献关键词共现聚类,分析了国内外山地植被垂直分布的热点领域,并对理论与假说、研究方法和主要研究领域等进行了述评。山地植被垂直格局历经了从单因子描述、多因子分析到机理和假说的求证,代表性理论包括:时间学说、空间异质性学说、竞争共存理论、中性理论及生态位理论等;从传统研究方法、数量分类与环境解释、遥感影像信息技术、模型及数字信息技术等进行了研究方法概述;并对热点研究领域进行了分析和述评,主要包括:山地植被垂直分布与驱动因素、山地植被生产力垂直变化、植物群落的谱系结构、基于生态位理论的植被分布预测等。总之,在全球气候变化背景下,山地植被及生态系统响应敏感且变化剧烈,山地植被对气候变化的响应、植被垂直带谱的数字信息化、水土耦合下的山地生态循环与生态系统服务等领域受到更广泛的重视;多尺度、多学科融合是本领域研究的发展趋势。
