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Leaf and Ecosystem Gas Exchange Responses of Buffel Grass-Dominated Grassland to Summer Precipitation

Pedosphere 2015年第1期25卷 112-123页

作者： Mir Zaman HUSSAIN Gnaana SARASWATHI Chhakchhuak LALRAMMAWIA dennis otieno Kailash PALIWAL John TENHUNEN Department of Plant Ecology University of Bayreuth Institute for Genomic Biology University of Illinois Department of Plant Sciences Madurai Kamaraj University

Sporadic rain events that occur during summer play an important role in the initiation of biological activity of semi-arid *** understand how ecosystem processes of a buffel grass(Cenchrus ciliaris L.)-dominated grassland respond to summer rain events,an LI 6 400 gas exchange system was used to measure the leaf gas exchange and plant canopy chambers were used to measure net ecosystem CO2exchange(NEE) and ecosystem respiration(Reco), which were made sequentially during periods before rain(dry) and after rain(wet). Gross ecosystem photosynthesis(GEP) was estimated from NEE and Reco fluxes, and light use efficiency parameters were estimated using a rectangular hyperbola model. Prior to the monsoon rain, grassland biomass was non-green and dry exhibiting positive NEE(carbon source) and low GEP values during which the soil water became increasingly scarce. An initial rain pulse(60 mm) increased the NEE from pre-monsoon levels to negative NEE(carbon gain) with markedly higher GEP and increased green biomass. The leaf photosynthesis and leaf stomatal conductance were also improved substantially. The maximum net CO2uptake(i.e.,negative NEE) was sustained in the subsequent period due to multiple rain events. As a result, the grassland acted as a net carbon sink for 20 d after first rain. With cessation of rain(drying cycle), net CO2 uptake was reduced to lower values. High sensitivity of this grassland to rain suggests that any decrease in precipitation in summer may likely affect the carbon sequestration of the semiarid ecosystem.

关键词： biomass CO2 exchange photosynthesis respiration soil moisture stomatal conductance

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Eco-Climatic Factors Influencing the Distribution of Black Ants (Carebara vidua) in Western Kenya

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Advances in Entomology 2022年第3期10卷 233-251页

作者： Davine Atieno Ondede dennis otieno Ochuodho Monica A. Ayieko Department of Plant Animal and Food Sciences Jaramogi Oginga Odinga University of Science and Technology Bondo Kenya Jaramogi Oginga Odinga University of Science and Technology Bondo Kenya

Black ant, Carebara vidua (Smith) is an edible insect of critical value in nutrition. The population abundance of black ants has reduced drastically and they have become scarce in all the agro ecological zones in Western Kenya. Understanding factors influencing the distribution and abundance of C. vidua remains a challenge as C. vidua is an endangered species in many parts of Country Kenya. The decline in the insect population is worrying since black ants are an important source of food across the world. Our study aimed at determining the eco-climatic conditions influencing the distribution of black ants. Several factors and conditions have contributed to the decline in the population of black ants. The study was carried out in different agro ecological zones of Kisumu, Siaya, and Homabay Counties. The research presumed a cross-sectional approach to community representation. The purposive sampling technique was used to select the population for the qualitative study. Data was collected through Focused Group Discussion and Key Informant Interviews to get in-depth knowledge on the factors contributing to the change in the distribution of back ants. Verbatim transcription was done to the audio recorded data then data was translated into English. Thematic analysis was done using *** software version 7.5. The results showed various factors that led to the change in distribution and reduction of the population of black ants emerging across the lower midland zones, the factors include;climate change, advancement in agricultural equipment, land degradation, and habitat destruction. These factors made the emergence of the insect unpredictable. Over the years across the Lower midland zones, there have been changes in the distribution of C. vidua and the population of insects emerging has reduced hence the insect is disappearing.

关键词： Black Ant Ecological Zones Distribution Population

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鼎湖山森林演替初期优势种马尾松的树干液流特征

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应用与环境生物学报 2022年第5期28卷 1167-1174页

作者：许天云黄健强曾小平张宜辉孟泽 dennis otieno 李跃林中国科学院华南植物园广州510650 厦门大学环境与生态学院厦门361005 中国科学院大学北京100049 肯尼亚奥丁加科技大学邦多210-40601

采用Granier热消散探针法(thermal dissipation probes,TDP),对鼎湖山南亚热带森林演替初期优势树种马尾松(Pinus massoniana)的树干液流变化进行连续监测,同时监测林分光合有效辐射、空气相对湿度、空气温度等环境因子,以探究演替初期... 详细信息

采用Granier热消散探针法(thermal dissipation probes,TDP),对鼎湖山南亚热带森林演替初期优势树种马尾松(Pinus massoniana)的树干液流变化进行连续监测,同时监测林分光合有效辐射、空气相对湿度、空气温度等环境因子,以探究演替初期马尾松树干液流特征、耗水量与其对环境的响应.结果表明:(1)日尺度上针叶林马尾松不同个体树干液流日变化趋势一致,晴天日变化为典型昼高夜低的单峰型曲线,峰值一般出现在中午12:00-14:00;雨天树干液流日变化呈单峰或多峰趋势,液流速率显著低于晴天,峰值出现在降雨后1-2 h内.在干季与湿季,马尾松的液流速率在各方面存在显著差异,干季(10月)马尾松的夜间液流速率显著小于湿季(8月)(P 0.05).日尺度上针叶林马尾松晴天树干液流主要受光合有效辐射、水汽压亏缺的影响(P <0.01);雨天主要受水汽压亏缺、相对湿度、温度的影响.在湿季(8月)与干季(10月)日尺度上马尾松的树干液流特征均首要受到水汽压亏缺的调控.本研究的马尾松林处于演替初期,其优势种马尾松蒸腾量高于同地带演替中期的马尾松,但相比其他地区针叶林,该演替初期马尾松蒸腾量处于较低水平,这有利于其适应季节性干旱环境.

关键词：马尾松针叶林演替初期树干液流鼎湖山

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鼎湖山南亚热带天然针阔叶混交林臭氧吸收特征

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生态学报 2018年第17期38卷 6092-6100页

作者：王立景胡彦婷张德强刘世忠孟泽 otieno dennis 李跃林中国科学院华南植物园广州510650 中国科学院大学北京100049 JaramogiOgingaOdinga University of Sciences&Technology BondoKenya 210-40601

针阔叶混交林是我国南亚热带针叶林向地带性常绿阔叶林演替的中间林分类型,为我国南亚地区主要森林类型,发挥着重要的生态系统服务功能。基于树干液流技术和对臭氧浓度的连续监测,评价该森林类型的臭氧吸收特征和能力有着重要的环境生... 详细信息

针阔叶混交林是我国南亚热带针叶林向地带性常绿阔叶林演替的中间林分类型,为我国南亚地区主要森林类型,发挥着重要的生态系统服务功能。基于树干液流技术和对臭氧浓度的连续监测,评价该森林类型的臭氧吸收特征和能力有着重要的环境生态学意义。对鼎湖山天然针阔叶混交林优势种马尾松(Pinus manssoniana)、锥栗(Castanopsis chinensis)、木荷(Schima superba)和华润楠(Machilus chinensis)在自然环境条件下的臭氧吸收能力进行了分析研究。结果表明:在日尺度上,4个优势树种的冠层气孔对臭氧导度(GO_3)和臭氧吸收通量(FO_3)均呈单峰型曲线,其最大值的时间在干季(10月至竖年3月)比湿季(4月至9月)滞后;季节尺度上,臭氧浓度在湿季达到最大值48.94 n L/L,湿季GO_3、FO_3和年臭氧吸收累积量(accumulative stomatal O_3flux,AFst)均显著高于干季(P <0.01),华润楠的臭氧吸收能力最强,在干季和湿季可分别达1.11 nmol m^(-2)s^(-1)和1.71nmol m^(-2)s^(-1)。随着水汽压亏缺(VPD)增大,优势种GO_3降低。光合有效辐射(PAR)超过1500 umol m^(-2)s^(-1)时,优势树种GO_3和FO_3呈下降趋势。针阔叶混交林的年臭氧吸收累积量超过了保护森林树木所采用的临界阈值,可认为鼎湖山针阔叶混交林受臭氧危害的潜在风险较高。

关键词：树干液流冠层气孔导度臭氧吸收针阔叶混交林

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鼎湖山天然针阔叶混交林优势树种对大气SO2的气孔吸收特征

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生态与农村环境学报 2020年第3期36卷 382-389页

作者：邓永红王立景黄健强孟泽刘世忠 otieno dennis 李跃林中国科学院华南植物园广东广州510650 中国科学院大学北京100049 中国科学院生态环境研究中心北京100085 Jaramogi Oginga Odinga University of Science and Technology BondoKenya 210-40601

利用树干液流技术、二氧化硫(sulfur dioxide,SO2)测定技术和气象观测手段,同步获取了鼎湖山天然针阔叶混交林群落优势树种水分利用、生物特征、环境SO2浓度及相关气象因子。根据水汽与痕量气体通过气孔双向交换的耦合关系,定量计算鼎... 详细信息

利用树干液流技术、二氧化硫(sulfur dioxide,SO2)测定技术和气象观测手段,同步获取了鼎湖山天然针阔叶混交林群落优势树种水分利用、生物特征、环境SO2浓度及相关气象因子。根据水汽与痕量气体通过气孔双向交换的耦合关系,定量计算鼎湖山针阔叶混交林中针叶树种马尾松(Pinus massoniana,Pm)及阔叶树种锥栗(Castanopsis chinensis,Cc)、木荷(Schima superba,Ss)、华润楠(Machilus chinensis,Mc)4种优势树种的冠层气孔SO2导度(GSO2)、SO2吸收通量(FSO2)及累积吸收量(F SO2,st),并分析其特征。结果表明,在日尺度上,日间SO2浓度和GSO2最大值时间基本重叠,各树种在正午前后出现最大吸收;在季节尺度上,SO2浓度干季(10—翌年3月)平均浓度为10.11 nL·L^-1,高于湿季(4—9月)的5.45 nL·L^-1。4个树种G SO2在湿季显著高于干季(P<0.001),F SO2在干季高于湿季(P<0.001)。锥栗和华润楠的F SO2,st分别为2.16和2.50 mmol·m^-2,高于马尾松(1.70 mmol·m^-2)和木荷(1.91 mmol·m^-2)。优势树种对大气SO2的气孔吸收行为主要受水汽压亏缺(vapor pressure deficit,VPD)、光合有效辐射(photosynthetically active radiation,PAR)和SO2浓度等因素影响。该研究可为评估珠三角地区针阔叶混交林乃至粤港澳大湾区森林的SO2吸收通量提供参考,为定量计算该地区环境的变化奠定基础。

关键词：树干液流针阔叶混交林冠层气孔导度二氧化硫痕量气体

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鼎湖山针阔叶混交林优势种树干液流特征及其与环境因子的关系

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应用生态学报 2012年第5期23卷 1159-1166页

作者：黄德卫张德强周国逸刘世忠 otieno dennis 李跃林中国科学院华南植物园广州510650 中国科学院研究生院北京100049

运用Granier热扩散式探针法,于2010年干湿季对鼎湖山自然保护区针阔混交林4种优势树种马尾松、锥栗、木荷和广东润楠的树干液流密度进行连续监测,并同步观测气温、相对湿度和光合有效辐射等环境因子的变化,研究其树干液流特征及其对环... 详细信息

运用Granier热扩散式探针法,于2010年干湿季对鼎湖山自然保护区针阔混交林4种优势树种马尾松、锥栗、木荷和广东润楠的树干液流密度进行连续监测,并同步观测气温、相对湿度和光合有效辐射等环境因子的变化,研究其树干液流特征及其对环境因子的响应.结果表明:在干湿季,4种优势树种的树干液流速率日变化均呈"昼高夜低"的典型单峰曲线,阔叶树锥栗、木荷和广东润楠的平均液流速率和峰值以及日液流量均显著大于针叶树马尾松;马尾松、锥栗、木荷和广东润楠的最大树干液流密度分别为29.48、38.54、51.67、58.32gH2O.m-2.s-1.优势树种树干液流速率的变化与环境因子的昼夜变化存在时滞;液流速率变化与光合有效辐射、水汽压亏缺和气温等环境因子的变化呈显著正相关,其中湿季以光合有效辐射为主导因子,干季以气温为主导因子.

关键词：针阔叶混交林树干液流环境因子干湿季鼎湖山

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季节性干旱驱动亚热带森林的碳积累

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Journal of Plant Ecology 2023年第1期16卷 241-256页

作者： Brian Njoroge Yuelin Li dennis otieno Shizhong Liu Simin Wei Ze Meng Qianmei Zhang Deqiang Zhang Juxiu Liu Guowei Chu Fasih Ullah Haider John Tenhunen Key Laboratory of Vegetation Restoration and Management of Degraded Ecosystems South China Botanical GardenChinese Academy of SciencesGuangzhou 510650China Guangdong Provincial Key Laboratory of Applied Botany South China Botanical GardenChinese Academy of SciencesGuangzhou 510650China University of Chinese Academy of Sciences Beijing 100039China Department of Botany Jaramogi Oginga Odinga University of Science and TechnologyBondo 210-40601Kenya Department of Plant Ecology University of Bayreuth95440 BayreuthGermany

本研究旨在表明处于南亚热带的鼎湖山生物圈保护区的干旱频率和强度正在增加,并说明季节性干旱对亚热带森林碳积累的影响。这是为了应对全球气候变化导致的干旱加剧所带来的威胁开展的一项研究。我们使干旱指数(标准化降水指数、标准降... 详细信息

本研究旨在表明处于南亚热带的鼎湖山生物圈保护区的干旱频率和强度正在增加,并说明季节性干旱对亚热带森林碳积累的影响。这是为了应对全球气候变化导致的干旱加剧所带来的威胁开展的一项研究。我们使干旱指数(标准化降水指数、标准降水蒸散发指数、降水距平百分率及自校准帕尔默干旱指数)准确确定干旱期和降水量增加期。此后,将2003至2014年(12年)监测采集的实测涡动通量和土壤含水量数据在干旱期和湿润期之间进行比较,以确定干旱对生态系统碳积累的影响。在本研究所选择的12年期间,干旱的发生时间约占比20%,最强干旱事件和严重程度发生于2012至2013年。研究期间的年平均降水量和气温分别为1404.57±43.2 mm和22.65±0.1°C,与30年记录(1990–2020)相比较,年降水量减少量可达523 mm,而气温则增加了2.55°C。与全球针对大多数森林生态系统研究所发表的数据呈相反趋势,处于中国南亚热带区域的鼎湖山生物圈保护区在60%的干旱期内所监测的森林生态系统记录到显著的碳积累趋势,说明季节性干旱驱动了森林的碳积累。

关键词：干旱气候变化碳积累鼎湖山生物圈保护区涡动通量

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Wavelength Dependent Nonlinear Spectroscopic Study of Third Harmonic Generation Probed by Rotational Maker Fringes Method

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Open Journal of Microphysics 2024年第2期14卷 13-23页

作者： Calford Odhiambo otieno Department of Physics Kisii University Kisii Kenya

Efficient third-order nonlinearities of the Zinc Oxide and Al-doped Zinc Oxide were studied by Third Harmonic Generation (Third Harmonic Generation) Maker fringes to establish the effect Aluminum of Aluminum doping (Al-doping) on the cubic nonlinearities. Adding the Al-dopant to the Zinc Oxide crystal structure results in changes that affect the optical and nonlinear characteristics. Presented results indicate that the magnitude of X(3) was enhanced at single experimental wavelengths;however, across the broadband experimental spectrum, the effect of Al-doping remained relatively constant. The observed enhancement of third-order nonlinearity was purely from the bound electronic response. The observation is attributed to increased charge carriers and spontaneous polarization in the Zinc Oxide and Al-doped Zinc Oxide crystal structure.

关键词： Nonlinear Optics Harmonic Generation Maker Fringes Zinc Oxide

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Density Functional Calculations of the Mechanical, Electronic and Dynamical Properties of Antiperovskite Ca₃BO (B = Pb, Ge, Sn)

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Open Journal of Microphysics 2024年第1期14卷 1-12页

作者： Phillip Wilfsen otieno Nyawere Department of Physical and Biological Sciences Kabarak University Nakuru Kenya

An analysis of mechanical, electronic and dynamical properties of antiperovskite Ca3BO (B = Pb, Ge, Sn) in cubic phase space group Pm-3m (221) has been studied using first principle density functional theory (DFT). Ground state energy computation was done using the Projector Augmented Wave (PAW) Pseudo Potentials and the Plane Wave (PW) basis set. The Generalized Gradient Approximation (GGA) was used for the exchange correlation. The open source code QUANTUM ESPRESSO (QE) was used in this study in which plane wave basis sets are applied for the expansion of the electronic structure wave function. Thermo_pw as a post-processing code was used for the computation of mechanical properties including bulk modulus and elastic constants with their derivatives. The lattice parameters are here calculated to be 4.87 Å, 4.86 Å and 4.84 Å for Ca3BO (B = Pb, Ge, Sn) respectively which compares well with other works. This also shows that the three crystals are similar in size and in most of their properties. In addition to this, projected density of states and band structure are also computed both showing that these materials are of semi-metallic nature and are stable in cubic phase. Phonon modes at gamma are also reported.

关键词： Antiperovskite Elastic Constants Generalized Gradient Approximation

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Optimization of Methylene Blue Dye Adsorption onto Coconut Husk Cellulose Using Response Surface Methodology: Adsorption Kinetics, Isotherms and Reusability Studies

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Journal of Materials Science and Chemical Engineering 2024年第2期12卷 1-18页

作者： Frank Ouru Omwoyo Geoffrey otieno School of Chemistry and Material Science Technical University of Kenya Nairobi Kenya

In this study, coconut husk cellulose was employed as a cost-effective and environmentally friendly adsorbent to eliminate methylene blue (MB) dye from aqueous solutions. The successful development of response surface methodology paired with a central composite design (RSM-CCD) enabled the optimization and modelling of the adsorption process. The study investigated the individual and combined effects of three variables (pH, contact time, and initial MB dye concentration) on the adsorption of MB dye onto coconut husk cellulose. The developed RSM-CCD model exhibited a remarkable degree of precision in predicting the removal efficiency of MB dye within the specified experimental parameters. This was demonstrated by the strong regression parameters, with an R2 value of 99.79% and an adjusted R2 value of 99.6%. The study depicted that the optimal parameters for attaining a 98.8827% removal of MB dye using coconut husk cellulose were as follows: an initial MB dye concentration of 30 mg∙L−1, contact time of 120 minutes, and pH 7 at a fixed adsorbent dose of 0.5 g. The Freundlich isotherm model provided the most satisfactory description of the equilibrium adsorption isotherms, suggesting that MB dye adsorption onto coconut husk cellulose occurs on a heterogeneous surface. The experimental results demonstrated a strong agreement with the pseudo-second-order kinetics model, indicating that the number of active sites present on the cellulose adsorbent predominantly influences the adsorption process of MB dye. Additionally, the adsorbent made from coconut husk cellulose exhibited the potential to be reused, as it retained its efficiency for a maximum of three cycles of adsorption of MB dye. The results of this study show that coconut husk cellulose has the potential to be an effective and sustainable adsorbent for removing MB dye from aqueous solutions.

关键词： Adsorption Kinetics Isotherms Optimization Response Surface Methodology Cellulose

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