植被微气象的数值模拟

综合考虑梯度输送和阵性穿透作用，并对植被上方的过渡层作适当处理，提出了植被微气象的一阶闭合模型。它对温、湿、风等物理量垂直分布的模拟精度良好。引用系统优化理论和方法，对模型中参数作多维非线性搜索，结果客观可靠。由于植物本身的调节适应能力和反馈作用，大气与植被间的动量与水热交换机制和过程不尽相同。在动量输送过程中，梯度产生项和阵性穿透皆不可忽视，尤其在群体下部，更为重要；而在热量和水分输送过程中，阵性穿透作用在低矮密集植被中的贡献甚微，梯度产生项起主导作用。     

Large-Eddy Simulation of Coherent Turbulence Structures Associated with Scalar Ramps Over Plant Canopies

Large-eddy simulations were performed of a neutrally-stratified turbulent flow within and above an ideal, horizontally- and vertically-homogeneous plant canopy. Three simulations were performed for shear-driven flows in small and large computational domains, and a pressure-driven flow in a small domain, to enable the nature of canopy turbulence unaffected by external conditions to be captured. The simulations reproduced quite realistic canopy turbulence characteristics, including typical ramp structures appearing in time traces of the scalar concentration near the canopy top. Then, the spatial structure of the organised turbulence that caused the scalar ramps was examined using conditional sampling of three-dimensional instantaneous fields, triggered by the occurrence of ramp structures. A wavelet transform was used for the detection of ramp structures in the time traces. The ensemble-averaged results illustrate that the scalar ramps are associated with the microfrontal structure in the scalar, the ejection-sweep structure in the streamwise and vertical velocities, a laterally divergent flow just around the ramp-detection point, and a positive, vertically-coherent pressure perturbation. These vertical structures were consistent with previous measurements made in fields or wind tunnels. However, the most striking feature is that the horizontal slice of the same structure revealed a streamwise-elongated region of high-speed streamwise velocity impacting on another elongated region of low-speed velocity. These elongated structures resemble the so-called streak structures that are commonly observed in near-wall shear layers. Since elongated structures of essentially similar spatial scales were observed in all of the runs, these streak structures appear to be inherent in near-canopy turbulence. Presumably, strong wind shear formed just above the canopy is involved in their formation. By synthesis of the ensemble-averaged and instantaneous results, the following processes were inferred for the development of scalar microfronts and their associated flow structures: (1) a distinct scalar microfront develops where a coherent downdraft associated with a high-speed streak penetrates into the region of a low-speed streak; (2) a stagnation in flow between two streaks of different velocities builds up a vertically-coherent high-pressure region there; (3) the pressure gradients around the high-pressure region work to reduce the longitudinal variations in streamwise velocity and to enhance the laterally-divergent flow and lifted updrafts downstream of the microfront; (4) as the coherent mother downdraft impinges on the canopy, canopy-scale eddies are formed near the canopy top in a similar manner as observed in conventional mixing-layer turbulence.     

植物化感作用在血吸虫病防治中的应用

对抑螺植物的化感物质、化感作用、抑螺植物的标准进行了系统的阐述,对植物化感作用在血吸虫病防治中的研究情况进行了简要介绍,并重点对抑螺植物化感作用在血吸虫病防治上的应用技术进行了研讨,研究结果对植物化感作用在血吸虫病防治中的应用将具有积极的指导和推动作用。     

科尔沁沙地植物多样性对生产力的影响及分布格局

采用种丰富度和以Shannon-Wiener指数为计算方法的功能多样性和组成多样性为指标,探讨了植物多样性对科尔沁沙地草场生产力的影响以及其分布格局特征。结果表明,科尔沁沙地植被不同的物种多样性指数对系统生产力的影响以组成多样性最大,功能多样性次之,植物种丰富度最小。在小尺度上,组成多样性只存在一种格局且具有分形结构,其格局对干扰过程反应不明显;功能多样性有多种格局存在,对多种干扰过程反应敏感。从提高沙地草场生产力和增强系统的稳定性角度出发,草场改良的依据应建立在种的引进和引进种所产生的组成多样性上。     

植物碳同位素分馏作用与环境变化研究进展

在简述植物碳同位素与环境要素之间关系的基础上,介绍了植物碳同位素分馏机理和分馏模式,并综述了近年来利用植物碳同位素及其组成在研究环境变化方面的研究进展,同时对未来的研究作了展望。     

汤屯高速公路路堑边坡土质特征与生态防护植物配置研究

汤屯高速公路边坡土壤具有偏酸性、有机质低、磷缺乏、铜过量等土质特征。边坡生态防护具有边坡高陡、原生植被彻底破坏、土质贫瘠、缺水、缺肥、生物气候干热胁迫、水土流失严重等难点,遵循交通安全性、景观协调性、生态适应性、生物多样性、经济实用性的原则,提出了以草本植物为主,草、灌、藤有机结合的边坡生态防护植物配置方案,针对全岩质边坡、碎裂结构边坡、土质边坡及边坡的顶部、下沿、平台等部位提出了不同的植物群落配置原则及物种配比方案,对类似工程具有借鉴意义。     

内蒙古乌达早二叠世含植物化石凝灰岩及其地质意义

本文通过对乌达地区山西组下部含树干化石凝灰岩岩性的观察,结合区域构造背景及前入研究成果,与邻区同-火山事件层进行对比,推测凝灰岩层的火山物质可能来源于乌达以北地区,即古亚洲洋向华北板块俯冲引起的弧火山喷发。凝灰岩层中下部和上部所含植物化石差异明显,表明该期火山事件对研究区的地理环境影响显著。另外,古亚洲大洋向华北板块俯冲及其后碰撞作用,可能是贺兰拗拉槽再次活动接受沉积的重要的动力学条件,特别是在晚石炭世-早二叠世时期。     

如何对濒危物种进行评估与拯救？

物种的灭绝本是一个自然过程,但人类的繁荣使数以百万计的生物物种的栖息地被蚕食,很多物种以惊人的速度灭绝了(如长江中的白鱀豚和白鲟)或正在绝灭之中(中华鲟),但却未伴随新物种的自然产生世界自然保护联盟虽然确定了物种濒危的等级标准,但定量划分标准的象征意义大于实际意义,因为不可能所有生物物种都能通过同一种种群动态模式去预测它们未来的命运关于物种的濒危机制,人们提出了许多基于种群数量变动的理论概念(如最小生存种群、有效种群大小、种群瓶颈、奠基者效应、"阿利"效应、灭绝漩涡等),但可操作性不强,对保护生物学的实际指导意义不大本文提出了物种生存状态转化的概念模型,物种生存状态主要取决于物种对外在环境的综合生存适合度f(s)和灭绝风险R,受到①物种生存空间的完整性、②生态过程的适宜性、③食物的可得性、④对人为致死或自然灾害的抵抗力等的影响f(s)由物种对若干决定性生存因子s1、s2、s3…的适合度之乘积所决定:f(s)=f(s1)f(s2)f(s3)……,f(s)取值0～1,1表示最大的适合度(理想生存状态),0表示彻底丧失了适合度,因此,任何一个决定性生存因子的趋零,都会导致该物种的灭绝(木桶效应)物种的生存状态指数H(f,R)由f(s)和R联合决定可用f(s)来评估与预测物种的灭绝风险(譬如,可区分为3～4个风险等级),突变临界点之前的动态过程可作为物种濒危的早期预警信号,物种拯救临界点可作为保护性干预的最低目标当然,这里只是提出了一个概念模型,各个决定性生存因子的适合度函数f(s)有待确定,并需要以真实的物种为对象进行验证.     

Screening Indian Mustard Genotypes for Phytoremediating Arsenic‐Contaminated Soils

Ten Indian mustard (Brassica juncea L.) genotypes were screened for their phytoremediation potential for arsenic (As) contaminated water under laboratory‐controlled conditions. The genotypes were grown in a hydroponic chamber for 20 days in 250‐mL beakers containing As‐contaminated water. During plant development, changes in plant growth, biomass, and total As were evaluated. Of the 10 genotypes (Pusa Agrani, BTO, Pusa Kranti, Pusa Bahar, Pusa Bold, Pusa Basant, Pusa Jai Kisan, Arka Vardhan, Varuna, and Vaibhav) Pusa Jai Kisan was the most effective in phytoremediating As‐contaminated water under hydroponic conditions. This will provide new information for Indian mustard genotypes for phytoremediating As‐contaminated soils.     

Bioavailability and toxicity of antimony

Antimony (Sb) is a toxic trace element widely distributed in the lithosphere and mainly associated with arsenic. Sb compounds are considered to be pollutants of high interest, however, the biogeochemical behaviour of Sb is still largely unknown, especially compared to other well-known toxic elements. In particular, questions remain about the availability of Sb to vascular plants. In this work, we focused on the following problems: (i) Sb uptake by plants; (ii) the availability of Sb to plants and (iii) variations in uptake and distribution of essential plant nutrients and trace elements resulting from bioaccumulation of Sb in Triticum aestivum (wheat) seedlings. The seedlings were either germinated or grown in media enriched with Sb. By the end of germination, concentrations of Sb in the seedlings germinated in Sb-amended media increased significantly. Sb content was highest in the roots and lowest in the leaves of the seedlings. After transfer of the seedlings germinated in an Sb-free medium to Sb-enriched media, Sb concentration in the seedlings increased with time, especially in the roots. Bioaccumulation of Sb influenced concentrations of different macro- and trace elements in all parts of the plants. The least variations were observed in the leaves, probably because the increase of Sb concentration in leaves was not as significant as in the seeds and roots.