Plant biomass allocation strategies of the dominant species in an alpine meadow of northwestern Sichuan,China北大核心CSCD

Plant biomass partitioning is an important driver of whole-plant net carbon gain, as biomass allocation could directly affect plant's future growth and reproduction. Alpine meadow in the northwestern Sichuan was impressed by the abundant community structure and species diversity. This study on biomass allocation pattern of different functional types and lifeforms might help understand plant life-history strategy of alpine meadow plants. We investigated 72 dominant herbaceous species for their compartments, biomass, and morphological traits during 2012-2014. These plants were sampled from natural grassland, disturbed grassland, and wintergreen grassland; they belonged to three functional types (grass, sedge, and forb) and two lifeforms (annual and perennial). The scaling relationships between functional traits of these plants were analyzed using Model type II regression method to estimate the parameters of the allometric equations. (1) Biomass allocation proportion of components significantly differed among grasses, sedges, and forbs owing to phylogeny: grasses had the highest stem biomass percentage, sedges had higher root biomass percentage, and forbs had higher leaf biomass percentage, but the scaling relationships were not significantly different, and isometric scaling was noted between biomass components for the three functional types. (2) Moreover, plant lifeforms affected the biomass allocation proportion of components, owing to the shorter or longer turnover rate and investment strategy between annual and perennial species. Annuals allocated more biomass to the stem and reproduction organs, but perennials invested more biomass to the leaves and roots. (3) In addition, plants from different grassland types differed in both biomass and morphology traits. Moreover, forbs from natural grassland and wintergreen grassland had higher leaf and reproductive biomass, but those from disturbed grasslands had higher stem biomass. Our results suggest that the functional type and lifeform decide the inherent scaling relationships between components of plants, but anthropogenic disturbance significantly impacted the quantity of component biomass. This study has important theoretical and practical significance to understand the response of alpine plants to climate change and anthropogenic disturbance as well as to help in the scientific management of alpine meadow. © 2018 Science Press. All rights reserved.     

短链氯化石蜡(SCCPs)和多环芳烃(PAHs)联合暴露对HepG2细胞抗氧化系统的影响

环境污染物的低剂量、联合毒性效应已经成为毒理学研究中的热点问题。短链氯化石蜡(SCCPs)和多环芳烃(PAHs)都是典型的有机污染物且在人母乳和血液中都以较高的浓度水平存在。为探究PAHs和SCCPs的联合暴露毒性效应,选择了HepG2细胞作为受试模型,测定了PAHs、SCCPs和它们的混合物暴露后细胞增殖活性及抗氧化系统指标。结果表明,PAHs和SCCPs暴露都能引发ROS的产生,两者混合时更加剧了ROS的产生,表现为协同效应。另外,PAHs和SCCPs暴露都能引起过氧化物歧化酶(SOD)活性的降低,因此两者混合时共同抑制SOD酶活性,表现为协同效应。而PAHs引起过氧化氢酶(CAT)活性升高,SCCPs则显著抑制CAT酶活性,两者联合暴露时CAT酶活性仍降低,但表现为拮抗效应。另外,PAHs和SCCPs暴露都引起谷胱甘肽(GSH)含量的轻微下降,只有SCCPs暴露引起丙二醛(MDA)含量显著升高,而两者联合暴露对GSH含量和MDA含量的影响表现为拮抗效应。表明不管是PAHs和SCCPs单独暴露还是联合暴露都能够干扰HepG2细胞内部的抗氧化系统,破坏抗氧化系统和自由基之间的平衡,使细胞氧化性损伤,甚至造成细胞凋亡。     

Effects of phosphorus sources on volatile organic compound emissions from <Emphasis Type="Italic">Microcystis flos</Emphasis>-<Emphasis Type="Italic">aquae</Emphasis> and their toxic effects on <Emphasis Type="Italic">Chlamydomonas reinhardtii</Emphasis>

There is diverse phosphorus (P) in eutrophicated waters, but it is considered as a crucial nutrient for cyanobacteria growth due to its easy precipitation as insoluble salts. To uncover the effects of complex P nutrients on the emission of volatile organic compounds (VOCs) from cyanobacteria and their toxic effects on other algae, the VOCs from Microcystis flos-aquae supplied with different types and amount of P nutrients were analyzed, and the effects of VOCs and their two main compounds on Chlamydomonas reinhardtii growth were investigated. When M. flos-aquae cells were supplied with K₂HPO₄, sodium pyrophosphate and sodium hexametaphosphate as the sole P source, 27, 23 and 29 compounds were found, respectively, including furans, sulfocompounds, terpenoids, benzenes, aldehydes, hydrocarbons and esters. With K₂HPO₄ as the sole P source, the VOC emission increased with reducing P amount, and the maximum emission was found under Non-P condition. In the treatments of M. flos-aquae VOCs under Non-P condition and two main terpenoids (eucalyptol and limonene) in the VOCs, remarkable decreases were found in C. reinhardtii cell growth, photosynthetic pigment content and photosynthetic abilities. Therefore, we deduce that multiple P nutrients in eutrophicated waters induce different VOC emissions from cyanobacteria, and P amount reduction caused by natural precipitation and algal massive growth results in more VOC emissions. These VOCs play toxic roles in cyanobacteria becoming dominant species, and eucalyptol and limonene are two toxic agents.     

基于等效桁架模型的基坑双排桩结构计算模型研究

在基坑双排桩支护体系中,由于前、后排桩桩间土的存在,导致其受力及变形机理变得非常复杂,而当前规程及其它常见的双排桩计算模型中,仅采用水平构件等效桩间土的作用不够完善。通过引入等效桁架模型,将前、后排桩桩间土等效为平面桁架结构,进而提出一种基坑双排桩支护结构的改进计算模型。再利用MATLAB自行编制相应的计算程序包,将该计算程序包应用到1个典型的算例分析中,对提出的基坑双排桩改进计算模型的合理性及可行性进行验证。结果表明,引入桩间土等效桁架模型后,由于考虑了桩间土的剪切变形效应和桩侧摩阻力,基坑双排桩计算模型的计算精度和合理性有了进一步提高。     

用醌式染料的合成反应光度法测定水中NO_2~-

报道了以N、N－二甲基苯氨、对氨基苯乙酮为偶联、重氮试剂,利用醌式染料的合成反应测定NO2-的新方法。本法灵敏度高（ε=5．33×104）,选择性好,无试剂空白。NO2-在0～800μg／L内服从比耳定律。醌式染料及试剂均稳定,已用于环境水中NO2-的测定。     

顶空固相微萃取法测定饮用水中的氯仿

采用不同于传统涂层型纤维的体型活性碳纤维相微萃取测定饮用水中的氯仿,实验确定的萃取时间为６００ｓ,解吸时间为３ｍｉｎ,将萃取器针头完全插入气化室时的热解吸效果最佳,方法具有较好的重现性（４．１４％ＲＳＤ）,线性范围０－５０ｎｇ／ｍｌ,最低检测限为５ｎｇ／ｍｌ,用该方法和国家标准方法（ＧＢ５７５０－８５）对实际水样进行了分析比较,表明了顶空固相微萃取法检测结果与国标法相当,而灵敏度３．８倍于国标法,     

河道治理类工程环境影响评价——以北京市大兴区天堂河为例

本文以天堂河河道治理工程为例,综述了河道治理类工程施工期、运行期可能产生的各项环境影响,并提出相应的环境保护对策措施,旨在为以后的河道治理类工程环境影响评价提供参考。     

加拿大一枝黄花有性生殖特征研究

加拿大一枝黄花Solidago canadensis L.是分布于我国的危害性最为严重的入侵种之一,它既可以通过有性生殖又可以通过无性生殖进行繁殖.对加拿大一枝黄花有性生殖的相关特征,如花序和小花的生物学特性、结实率和传粉方式等进行了研究.结果表明,加拿大一枝黄花的性系统为雌全性系统,每花序总花数为(15.16±1.67)个,缘花/盘花值为3.07±0.64.对成熟果实透明后进行的结实率统计表明,其结实率较低.套纱布网袋后的结实率极显著低于开放性授粉的,表明其花序是需要昆虫传粉的类型.加拿大一枝黄花的花序结构特征和开放式样显示出有利于增加异交的特点.尽管其结实率相对较低,但整个植株结实量大,仍需要防止其通过有性生殖产生的种子进行远距离的扩散和在新分布地区建立种群. 花有性生殖的相关特征,如花序和小花的生物学特性、结实率和传粉方式等进行了研究.结果表明,加拿大一枝黄花的性系统为雌全性系统,每花序总花数为(15.16±1.67)个,缘花/盘花值为3.07±0.64.对成熟果实透明后进行的结实率统计表明,其结实率较低.套纱布网袋后的结实率极显著低于开放性授粉的,表明其花序是需要昆虫传粉的类型.加拿大一枝黄花的花序结 特征和开放式样显示出有利于增加异交的特点.尽管其结实率相对较低,但整个植株结实量大,仍需要防止其通过有性生殖产生的种子进行远距离的扩散和在新分布地区建立种群. 花有性生殖的相关特征,如花序和小花的生物学     

滚筒洗衣机箱体振动与噪声控制

为了减小滚筒洗衣机箱体的振动噪声,对滚筒洗衣机箱体进行了模态试验并识别出模态参数。然后建立了箱体的有限元模型,对其进行了计算模态分析。有限元分析结果与试验结果吻合较好,验证了有限元模型的正确性。依据模态分析结果,对洗衣机箱体进行改进,通过建立有限元模性进行谐响应分析,证明提高箱体刚度可以收到减振降噪效果。     

长株潭两型社会的生态市场培育研究

随着长株潭城市群两型社会建设的推进,培育生态市场经济已经成为必然要求。对长株潭两型社会生态市场发展面临的现状进行分析,研究了发展长株潭两型社会生态市场培育的要点与难点,最后借鉴国内外的相关经验,从法制保障、行政规制、经济手段、道德约束等方面,对长株潭两型社会的生态市场培育进行了分析与探讨。