Shallow water flow in a deeply weathered granite aquifer and implications for hydrochemical models

Starting in 1987, comprehensive investigations in the 4.2 km² Lehstenbach catchment in the Fichtelgebirge (South Germany) were performed to determine water and matter fluxes. The catchment is nearly totally covered by Norway Spruce stands. The measurements indicate that the vertical profile of groundwater flow is strongly heterogeneous: lateral flow in the upper aquifer layers seems to prevail. As the upper layers show marked acidification, only a small portion of precipitation water infiltrating during storm events can be buffered here, resulting in acidic catchment runoff. On the other hand, this implies a remarkable retardation of acidification of the deeper layers. The purpose of this paper is to investigate the hydrological specifics of the catchment, especially to identify and characterize the flowpaths. To that end, we use two different modelling approaches. Results of these model runs can be used to assess the impacts on hydrochemical models.     

Nikolay I. Makkaveev and the development of Fluvial Geomorphology in Russia and the former Soviet Union

2008 marks the centenary of the birth of Professor Nikolay Ivanovich Makkaveev (1908–1983), a former Professor in the Faculty of Geography at Moscow State University and the founder of the Laboratory of Soil Erosion and Fluvial Processes in the Faculty of Geography.     

Identification of Value-adding Strategies in the Swedish Sawn Wood Industry

Swedish sawmills are increasing their application of value-adding processes in sawn wood production. This study identified the most common value-adding combinations used by the Swedish sawmills. Data were obtained from a survey of Swedish sawmills in 1995 and from industry statistics. Nine different groupings of sawmills with regard to the level and types of value-adding technologies were identified by cluster analysis. The largest group added value only to marginal quantities of their production. Eight other groups that applied different combinations of value-adding processes were identified. Drying and planing were important elements in several strategies. Adding value to the sawn wood is not a homogeneous strategy; instead it includes several ways to focus production on different products and customer groups. Advanced value-adding processes often generated a higher unit profit margin than the production of commodity sawn wood.     

三农音频资源管理系统-1

随着农业信息化的发展,广泛地传播三农知识、推进先进技术实现资源共享已成为中国农业发展的一个重要课题。音频是三农信息的一种展现形式,是通过声音的方式记录、传播三农相关的科技知识,可以扩展传播方式,增加接受人群,用户可以通过下载和在线的方式使用音频资料。基于此,笔者设计开发了一种可以收集整理并分类发布音频资源的管理系统,简述了该系统的设计路线,系统开发的相关技术,并详细介绍了该系统的数据库设计、系统流程,以及主要功能模块等。该系统的应用对于提高三农音频资源利用率、提升三农信息服务水平发挥了重要作用,使得先进技术及知识经验实现了资源的共享,同时也为广大农民提供了一条查找三农信息资源的捷径。     

糜子花粉粒和胚囊发育的步调比较

本文对糜子的花粉和胚囊发育的步调进行了比较,并对花粉败育进行了形态学观察。小孢子母细胞在花药长度为0.5mm时进入减数分裂,早于大孢母细胞,进程较大孢母细胞的减数分裂慢,四分孢子时期持续时间短,单核花粉时期持续时间长(约72h),从小孢母细胞减数分裂开始到花粉粒成熟约需8d。大孢母细胞的减数分裂迟于小孢母细胞,减数分裂进程速度较快,从单核胚囊开始,稍微加快了发育速度,以此与花粉的成熟取得一致。败育花粉的母细胞能进行正常的减数分裂,但在单核花粉时,由于绒毡层不解体,使其得不到养料,从而停止发育。     

旱地土壤中的硝化-反硝化作用

本文综述了国内外旱地土壤硝化 -反硝化作用的过程及其影响因数和硝化 -反硝化作用产生的N2 O量及其影响因素以及旱地土壤上氮肥硝化 -反硝化损失量等方面的研究进展     

平稳集值随机过程的平稳选择存在定理

采用［2］中平稳集值随机过程的定义，证明了在可逆的保测变换下，平稳集值随机过程存在平稳选择。     

含变气压非刚性联接件机械动力过程数值模拟

介绍了对含变气压非刚性联接件机械计算机数值模拟方面的研究进展，着重讨论了其动力过程计算机数值模拟的基本方程、实用方程、计算原理及计算结果。动力过程所做功的计算值与实测值的误差均小于5％。动力过程计算机数值模拟为该机械的性能预测和参数优化提供了新的方法。     

Simulation of the vegetation structure and function in a Malaysian tropical rain forest using the individual-based dynamic vegetation model SEIB-DGVM

An individual-based Dynamic Global Vegetation Model, the SEIB-DGVM, was adapted to a Malaysian tropical rain forest by incorporating formulas and parameters from a gap dynamics model, FORMIX3. After calibration, the model reconstructed forest structure (i.e., size structure, leaf area index, and woody biomass) and carbon fluxes (i.e., gross and net primary productivity) of a dipterocarp forest in Pasoh, Peninsular Malaysia. Sensitivity analysis demonstrated that the model was robust; forest structure and ecosystem functions moderately fluctuated due to changes in parameters and climatic environments. Sensitivity analysis also indicated that the success and decay of a dominant species group that monopolized the canopy layer greatly affected those of a less abundant, shade-intolerant group. This result indicates that even if environmental changes do not exhibit clear effects on dominant canopy species and/or whole forest structure, such changes may still substantially impact the biodiversity of subdominant species. In simulations without gap formation, woody biomass was overestimated and a shade-intolerant species group was eliminated. This finding indicates that incorporating gap formation into the individual-based model is essential for the appropriate simulation of forest biomass and biodiversity in this Malaysian tropical rain forest.     

土壤垂向分层和均匀处理下水分差异的数值探讨

在现有众多的陆面过程模型中,对土壤水分的定量描述一般是假设垂向分布均匀,取表层土壤质地来表示整个垂向土壤质地。垂向分层和均匀处理下的土壤水分是存在差异的,这种差异有多大目前少有研究。设置3组不同饱和导水率组合的层状土壤代表不同区域的非均匀土壤,取3组层状土壤的上层土壤代表整个均匀土壤,通过建立一维土壤水分运动模型分析这种差异,同时分析饱和导水率、饱和含水量、残余含水率、孔隙大小分布参数和形状参数对层状土壤和均匀土壤的渗透量和储水量差异的敏感性,探讨垂向层状和均匀处理下土壤水分运动的差异。研究结果表明:1)建立的一维土壤水分运动模型模拟的土壤水分剖面与Yeh解析解和室内五水转化试验的土壤水分剖面一致,表明模型无论是考虑还是不考虑根系吸水都具有可靠性。2)采用垂向均匀方式处理,上下层饱和导水率相差越大的层状土壤,各水文变量的差异越大。当层状土壤上下层饱和导水率相差1.5倍时,层状土壤和均匀土壤的水分分布差别小于0.05 cm~3×cm~(-3);而当层状土壤上下层饱和导水率相差达3.3倍时,层状土壤和均匀土壤的水分分布差别达0.15 cm~3×cm~(-3),渗漏量相差20 cm以上,储水量相差5 cm左右。3)相对于层状土壤下层,均匀土壤下层的持水能力更差,水流速度更快,导致下层水分分布减小,渗漏量增加,储水量减小。4)形状参数n对渗透量的敏感性最强,土壤孔隙大小分布参数对储水量的敏感性最强,形状参数n其次。在实际应用中,如果一个区域的土壤上下层饱和导水率相差较大,那么垂向均匀处理可能会导致很大的误差,和实际土壤的水分分布相差很大,这会严重影响土壤水分的准确估计,在实际处理中需要认真考虑。