This study was conducted to assess the current stock of soil organic carbon under different agricultural land uses, soil types and soil depths in the Noun plain in western Cameroon. Three sites were selected for the s...This study was conducted to assess the current stock of soil organic carbon under different agricultural land uses, soil types and soil depths in the Noun plain in western Cameroon. Three sites were selected for the study, namely Mangoum, Makeka and Fossang, representative of the three dominant soil types of the noun plain (Andosols, Acrisols and Ferralsols). Three land uses were selected per site including natural vegetation, agroforest and crop field. Soil was sampled at three depths;0 - 20 cm, 20 - 40 cm, and 40 - 60 cm. Analysis of variance showed that soil type did not significantly influence carbon storage, but rather land uses and soil depth. SOCS decreased significantly with depth in all the sites, with an average stock of 66.3 ± 15.8 tC/ha at 0 - 20 cm, compared to an average stock of 33.3 ± 7.4 tC/ha at 40 - 60 cm. SOCS was significantly highest in the natural formation with 57.2 ± 19.7 tC/ha, and lowest in cultivated fields, at 37.7 ± 10.6 tC/ha. Andosols, with their high content of coarse fragments, stored less organic carbon than Ferralsols and Acrisols.展开更多
The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts...The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts of monovalent cations. It was suggested that mono-valent cations had competition coordination with Na^+ for Dy(PPP)_2^(7-).展开更多
Agroforestry systems (AFSs) offer viable solutions to climate change because of the below-ground biomass (BGB) that is maintained by the soil. Therefore, spatially explicit estimation of their BGB is crucial to accoun...Agroforestry systems (AFSs) offer viable solutions to climate change because of the below-ground biomass (BGB) that is maintained by the soil. Therefore, spatially explicit estimation of their BGB is crucial to account for emission reduction efforts. A study to assess soil organic carbon (SOC) and nitrogen dynamics in Arabica coffee agroforests was conducted in two subdivisions (Foumbot and Kouoptamo) of the Noun Division in western Cameroon. The methodological approach involved the collection of 150 soil samples taken at different depths: 0 - 10, 10 - 20 and 20 - 30 cm. Depending on the depth, the SOC stock is 27.93 ± 1.13 tC/ha at 10 cm depth, 22.37 ± 1.47 tC/ha at 20 cm and 20.79 ± 0.31 tC/ha at 30 cm. According to the age classes of the Arabica coffee systems (ACA), the C/N ratio in our study area averaged 26.94 ± 13.60 for the (5 - 20) year old systems in Foumbot and 60.64 ± 48.80 for the (20 - 35) year old systems in Kouoptamo. Depending on the depth, at 10 cm this ratio is higher in Kouoptamo than in Foumbot with a maximum value of 57 and 38 respectively for the two subdivisions. In view of the results obtained, it would be important to analyse the types of microorganisms responsible for the decomposition of organic matter which is linked to soil organic carbon.展开更多
名词短语作为重要词语组合之一,在神经科学、心理学、计算机科学等领域受到广泛关注,在语言学研究领域更是持续的热点,国外相关研究从1945年以来形成了气候,但是却没有相关研究综述。因此,以Web of Science核心集为数据来源,运用文献计...名词短语作为重要词语组合之一,在神经科学、心理学、计算机科学等领域受到广泛关注,在语言学研究领域更是持续的热点,国外相关研究从1945年以来形成了气候,但是却没有相关研究综述。因此,以Web of Science核心集为数据来源,运用文献计量工具CiteSpace,从文献作者、研究机构、研究热点和前沿等方面,对1945-2022年期间关于名词短语研究的文献进行了可视化分析。研究表明:(1)国外名词短语研究广泛且分散,发文国家多,仅形成美国、英国和法国三个高中介中心型国家。中国起步晚,但发展迅速,已成为发文量前五国家之一;(2) Schriefers、Caramazza和Costa发文量多且已形成合作网络。中国作者中香港城市大学兰舸形成了一定的合作网络。Chomsky和Levelt文献影响力最大;(3)名词短语生成、词序、一致性、搭配、名词短语复杂性是名词短语研究的热门话题。高被引文献主题集中在名词短语生成和名词短语复杂性两个方面,代表名词短语研究前沿。展开更多
文摘This study was conducted to assess the current stock of soil organic carbon under different agricultural land uses, soil types and soil depths in the Noun plain in western Cameroon. Three sites were selected for the study, namely Mangoum, Makeka and Fossang, representative of the three dominant soil types of the noun plain (Andosols, Acrisols and Ferralsols). Three land uses were selected per site including natural vegetation, agroforest and crop field. Soil was sampled at three depths;0 - 20 cm, 20 - 40 cm, and 40 - 60 cm. Analysis of variance showed that soil type did not significantly influence carbon storage, but rather land uses and soil depth. SOCS decreased significantly with depth in all the sites, with an average stock of 66.3 ± 15.8 tC/ha at 0 - 20 cm, compared to an average stock of 33.3 ± 7.4 tC/ha at 40 - 60 cm. SOCS was significantly highest in the natural formation with 57.2 ± 19.7 tC/ha, and lowest in cultivated fields, at 37.7 ± 10.6 tC/ha. Andosols, with their high content of coarse fragments, stored less organic carbon than Ferralsols and Acrisols.
文摘The effects of mono-valent cations, Li^+, K^+, Rb^+, Cs^+ and NH_4^+, on ^(23)Na NMR were investigated. It was found that the chemical shifts for Na^+ signal shifted downfield with the increase in the relative amounts of monovalent cations. It was suggested that mono-valent cations had competition coordination with Na^+ for Dy(PPP)_2^(7-).
文摘Agroforestry systems (AFSs) offer viable solutions to climate change because of the below-ground biomass (BGB) that is maintained by the soil. Therefore, spatially explicit estimation of their BGB is crucial to account for emission reduction efforts. A study to assess soil organic carbon (SOC) and nitrogen dynamics in Arabica coffee agroforests was conducted in two subdivisions (Foumbot and Kouoptamo) of the Noun Division in western Cameroon. The methodological approach involved the collection of 150 soil samples taken at different depths: 0 - 10, 10 - 20 and 20 - 30 cm. Depending on the depth, the SOC stock is 27.93 ± 1.13 tC/ha at 10 cm depth, 22.37 ± 1.47 tC/ha at 20 cm and 20.79 ± 0.31 tC/ha at 30 cm. According to the age classes of the Arabica coffee systems (ACA), the C/N ratio in our study area averaged 26.94 ± 13.60 for the (5 - 20) year old systems in Foumbot and 60.64 ± 48.80 for the (20 - 35) year old systems in Kouoptamo. Depending on the depth, at 10 cm this ratio is higher in Kouoptamo than in Foumbot with a maximum value of 57 and 38 respectively for the two subdivisions. In view of the results obtained, it would be important to analyse the types of microorganisms responsible for the decomposition of organic matter which is linked to soil organic carbon.
文摘名词短语作为重要词语组合之一,在神经科学、心理学、计算机科学等领域受到广泛关注,在语言学研究领域更是持续的热点,国外相关研究从1945年以来形成了气候,但是却没有相关研究综述。因此,以Web of Science核心集为数据来源,运用文献计量工具CiteSpace,从文献作者、研究机构、研究热点和前沿等方面,对1945-2022年期间关于名词短语研究的文献进行了可视化分析。研究表明:(1)国外名词短语研究广泛且分散,发文国家多,仅形成美国、英国和法国三个高中介中心型国家。中国起步晚,但发展迅速,已成为发文量前五国家之一;(2) Schriefers、Caramazza和Costa发文量多且已形成合作网络。中国作者中香港城市大学兰舸形成了一定的合作网络。Chomsky和Levelt文献影响力最大;(3)名词短语生成、词序、一致性、搭配、名词短语复杂性是名词短语研究的热门话题。高被引文献主题集中在名词短语生成和名词短语复杂性两个方面,代表名词短语研究前沿。
