More asymmetric tree competition brings about more evapotranspiration and less runoff from the forest ecosystems: A simulation study

The present paper reports how stand size-structure dynamics due to competition between different-sized trees affect long-term forested water balance in Japanese cool-temperate planted stands (evergreen coniferous Cryptomeria japonica and deciduous coniferous Larix kaempferi stands) using a fully coupled multi-layered meteorological surface physics—terrestrial ecosystems model. The simulation captured the well-known annual variation in leaf area index (LAI) accurately with stand age in monocultured and even-aged stands; the occurrence of maximum LAI during the early growth stage and then a gradual decline followed by a steady state after the maximum LAI. The simulations also detected a high dependency of annual evapotranspiration (AETr) on LAI with stand age that is well known by prior observational researches. In the C. japonica (shade-tolerant late-successional species) stand, the relationship between annual net primary productivity of an individual tree (NPP_ind) and individual tree mass (w) changed from linear to a convex curve during self-thinning, indicating that the degree of asymmetric tree competition intensified with forest stand development. The higher degree of competitive asymmetry characterized by the convex-shaped NPPind-w relationship produced greater size inequality, i.e., the formation of trees stratified by height. Under such conditions, AETr and annual transpiration (ATr) were mainly regulated by larger trees. On the other hand, the NPPind-w relationships in the L. kaempferi (shade-intolerant early-successional species) stand were linear throughout the simulated period, indicating the lower degree of competitive asymmetry. Under such conditions, the growth of intermediate-sized trees was enhanced and these trees became a dominant source of AETr (and also ATr) during self-thinning. Furthermore, the sensitivity analysis of the effects of ecophysiological parameters such as foliage profile (i.e., vertical distribution of leaf area density) of an individual tree (distribution pattern is described by the parameter η), the maximum carboxylation velocity (V_cmax0) and biomass allocation pattern of individual plant growth (μ₁) on AETr, ATr and annual runoff (AR_off) showed that the temporal trends of AETr, ATr, AR_off and NPPind-w relationships were completely the same as those in the control simulations. However, the NPPind-w relationship during self-thinning indicated higher degrees of competitive asymmetry when η or V_cmax0 were greater than those in the control simulation and generated greater AETr and ATr and thus smaller AR_off. We found that more asymmetric tree competition brings about greater size inequality between different-sized trees and thus more evapotranspiration and less runoff in a forest stand. Overall, our simulation approach revealed that not only LAI dynamics but also plant competition, and thus size-structure dynamics, in a forest ecosystem are essential to long-term future projections of forested water balance.     

Allometric scaling of resource acquisition by ruminants in dynamic and heterogeneous environments

We present a mechanistic formulation of the intake response of ruminants to vegetation biomass based solely on physiological and morphological parameters that scale allometrically with the animal's body mass. The model is applied to describe herbivore-vegetation interactions in dynamic and heterogeneous landscapes with low quality but abundant “tall grass” and high quality but sparsely available “short grass”, under two conditions: “uncoupled” (such that the effect of food intake on vegetation biomass can be neglected), or “coupled” (such that the vegetation biomass is determined by herbivore feeding). The results show that under uncoupled conditions, the minimum acceptance (proportion of vegetation consumed by the herbivore) at which the herbivore can leave its current patch without reducing its intake rate is when it has depleted the current patch by the energetic cost required to travel to another patch. The maximum acceptance at which the herbivore should leave its patch is when it has depleted the current patch by the cumulative energetic cost of traveling, handling, cropping, and digesting. Under coupled conditions, the optimal acceptance equals half the relative growth rate of the vegetation. Analytical solutions are obtained for equilibrium values for utilization of the vegetation, and for the densities of vegetation and ruminants, expressed in physiological and morphological herbivore parameters.     

电化学方法研究小分子与核酸相互作用的进展(Recent Electrochemical Investigation on the Interaction of Small Molecules with Nucleic Acids)

研究小分子与核酸的相互作用,对了解分子对DNA体内复制和转录的影响、探索疾病的发病机理和寻找新型药物设计等具有重要意义.电化学方法是一种重要的研究小分子与核酸相互作用的方法,而这方面的综述较少.论文首先论述了小分子与核酸相互作用的结合方式,并对采用电化学方法考察无机金属离子、金属配合物、有机药物分子、有机环境污染物与DNA相互作用的研究进展进行了归纳和评述,其中对有机小分子与核酸的相互作用进行了较详细介绍.最后,对该领域研究趋势进行了讨论.     

虚拟现实技术及其在环境科学中的应用

本文简要介绍了虚拟现实的基本概念和基本特征,重点探讨虚拟现实技术在环境科学领域的应用前景,并结合实例,论述了虚拟现实技术在环境管理、水环境和水资源、大气环境和预报、环境科学研究和教育等方面的应用。     

水岩化学作用对斜坡水文地质及滑坡的影响

在温湿气候区，水岩化学作用对岩质斜坡的水文地质演化及失稳一夷平进程具有重要的控制作用。从地表到新鲜岩体，随着水岩化学作用程度的逐渐减弱，斜坡剖面可依次划分为土层、腐岩带和风化岩带，各带之间多是渐变过渡的。土层多由枯枝落叶层和土壤层组成，有时底部含有残坡积物；腐岩是由岩浆岩、沉积岩或变质岩经等容风化形成的风化软岩；风化岩带是腐岩带的前身，其特征是含有较高数量的核心石。斜坡垂向分带主要是地下水引起的，而这种分带反过来又会强烈影响地下水自身的埋藏与分布。土层可贮存上层滞水，风化岩带则可赋存潜水或承压水。上层滞水是浅层滑坡的主要控制因素。由于形成条件宽松，但规模不大，上层滞水控制的滑坡灾害多具群发性特点，同时，由于其含水介质为松散土体，失稳含水层很容易转化为泥石流。降雨期间，风化岩带内潜水水位上升甚至承压，导致岩体抗剪强度降低并诱发深层滑坡。     

Modification of Soil Solid Aluminium Phases During an Extreme Experimental Acidification of A Horizons of Forest Soils from Southwest Europe

Four umbric A horizons from acid forest soils were acidified in a batch type experiment and its effect in the Al pools of the solid phase analysed by means of selective dissolution methods. The results showed that Al release accounted for the consumption of 85–99% of the added protons, and causes a decrease of 2–33% of the ‘reactive’ Al pool of the soil solid phase. In these A horizons, inorganic non-crystalline Al and high stability Al-humus complexes are the main sources of the dissolved Al. The contribution of the complexes with intermediate stability only was relevant in the more acid horizon developed from phyllites (P18-A). The increase of equilibration time from 96 to 720 h did not caused significant differences in the decrease of the ‘reactive’ Al pool suggesting the acid neutralising reactions occurred in less than 96 h. In most cases the quantity of released Al is in agreement with the decrease of the different reactive Al pools of the solid phase.     

Tapping the leakages: Methane losses, mitigation options and policy issues for Russian long distance gas transmission pipelines

The Russian natural gas industry is the world's largest producer and transporter of natural gas. This paper aims to characterize the methane emissions from Russian natural gas transmission operations, to explain projects to reduce these emissions, and to characterize the role of emissions reduction within the context of current GHG policy. It draws on the most recent independent measurements at all parts of the Russian long distance transport system made by the Wuppertal Institute in 2003 and combines these results with the findings from the US Natural Gas STAR Program on GHG mitigation options and economics.With this background the paper concludes that the methane emissions from the Russian natural gas long distance network are approximately 0.6% of the natural gas delivered. Mitigating these emissions can create new revenue streams for the operator in the form of reduced costs, increased gas throughput and sales, and earned carbon credits. Specific emissions sources that have cost-effective mitigation solutions are also opportunities for outside investment for the Joint Implementation Kyoto Protocol flexibility mechanism or other carbon markets.     

GUIDELINES FOR INTERACTIVE COMPUTER SOFTWARE IN WATER RESOURCES ENGINEERING1

ABSTRACT: A case study in the development of interactive computer software for water resources related engineering problems in presented. Guidelines for the preparation of a uniform set of interactive program requirements are discussed. Use of the developed guidelines will reduce computer usage expenditures by minimizing program learning time and data entry errors.     

外源锌对不同番茄品种抗氧化酶活性、镉积累及化学形态的影响

采用盆栽试验研究了重金属Cd(10 mg·kg-1)污染下,叶面喷施不同浓度Zn(0、50、100、200和400μmol·L-1)对2个番茄品种‘4641’和‘渝粉109’生长、抗氧化酶活性及番茄果实Cd形态和积累量的影响.结果表明,喷施Zn后,番茄根、茎、果实干质量和植株总干质量以及体内Cd含量和积累量在2个品种之间的差异达到了显著水平(p0.05).外源Zn(≤200μmol·L-1)提高了2个番茄品种的果实、根、茎、叶及总干质量.随Zn浓度的增加,2个品种根CAT活性以及‘渝粉109’根POD活性先增加然后降低;2个品种根SOD活性则呈先降后升再降趋势.番茄果实中各形态Cd含量的顺序为:残渣态Cd(FR)盐酸提取态Cd(FHCl)氯化钠提取态Cd(FNaCl)乙醇提取态Cd(FE)醋酸提取态Cd(FHA c)去离子水提取态(FW).适量的Zn(≤200μmol·L-1)减少了2个番茄品种果实中各形态Cd含量,但高量Zn(400μmol·L-1)增加了‘渝粉109’果实中的FE、FR和‘4641’果实中FHCl及FR含量.Cd积累量为叶茎根或果实.叶面喷施Zn使番茄根、茎、叶和果实中的Cd含量分别降低了18.6%~41.7%、10.6%~36.7%、5.8%~21.5%和2.3%~12.7%.供试2个番茄品种,无论喷Zn与否,果实Cd含量和果实Cd积累量均为‘4641’‘渝粉109’,植株Cd总积累量则为‘4641’‘渝粉109’.     

Removal of ammonium ion from water by Na-rich birnessite: Performance and mechanisms

Na-rich birnessite (NRB) was synthesized by a simple synthesis method and used as a high-efficiency adsorbent for the removal of ammonium ion (NH₄⁺) from aqueous solution. In order to demonstrate the adsorption performance of the synthesized material, the effects of contact time, pH, initial ammonium ion concentration, and temperature were investigated. Adsorption kinetics showed that the adsorption behavior followed the pseudo second-order kinetic model. The equilibrium adsorption data were fitted to Langmuir and Freundlich adsorption models and the model parameters were evaluated. The monolayer adsorption capacity of the adsorbent, as obtained from the Langmuir isotherm, was 22.61 mg NH₄⁺-N/g at 283 K. Thermodynamic analyses showed that the adsorption was spontaneous and that it was also a physisorption process. Our data revealed that the higher NH₄⁺ adsorption capacity could be primarily attributed to the water absorption process and electrostatic interaction. Particularly, the high surface hydroxyl-content of NRB enables strong interactions with ammonium ion. The results obtained in this study illustrate that the NRB is expected to be an effective and economically viable adsorbent for ammonium ion removal from aqueous system.