Population dynamics of tree species in southern Quebec,Canada: 1970–2005

Over the last few decades, several phenomena contributed to modify the structure and composition of the eastern North American forests. Along with forest management, disturbances such as insect defoliation, global environmental changes, acid deposition, and rising atmospheric CO₂ concentrations, have been identified as phenomena that could affect forest structure and composition. Currently, there is very little quantitative information on the resulting effect of multiple disturbances on the main parameters of forest dynamics (growth, mortality, and recruitment). Using available data from the Quebec permanent sample plots network, we analyzed the ecological response of tree species populations to the combined effect of contemporary global environmental changes, disturbance regimes, and forest management practices over the last 30 years in southern Quebec. The results indicate that the main parameters of forest dynamics changed considerably over the last three decades. The last spruce budworm outbreak initiated a successional change in coniferous stands. The basal area of Abies balsamea and Picea glauca, the most abundant coniferous species, decreased by 29.7%, while pioneer species abundance increased. For late successional deciduous species, observed changes in forest dynamics appear to be mainly associated with global environmental changes rather than with natural disturbances or forest harvesting. The results indicate that inferring responses of tree population dynamics to global environmental changes can be very complex or even misleading considering the confounding effects of other disturbance agents. The results also suggest that the ecosystem-based management approach promoted by forest ecologists, aimed at maintaining landscape stand composition and structures similar to those characterizing natural environments, will not be easily achieved. Forest ecosystems are highly dynamic and disturbances other than tree harvesting appear to have been the major factors affecting their pattern of change over the last three decades. Forest managers should consider adaptive management approaches that will consider the contemporary evolution of forest ecosystems in a changing environment.     

天津蓟州独乐寺古建筑群昆虫多样性及关键害虫防治

对天津蓟州区独乐寺古建筑群昆虫多样性进行系统调查，并对危害建筑、设施、重要文物和古树的害虫进行了综合防治研究。结果表明，寺内发生的昆虫共计12目37科66种，其中有害昆虫5目10科17种。危害古建筑木质构件和泥塑雕像等文物的主要是花斑皮蠹(Trogoderma variabile)，危害古建筑室外木构件的主要为黑颚条蜂(Anthophora melanognatha)和黄胸木蜂(Xylocopa appendiculata)，黑颚条蜂及十二斑毛斑蜂(Melecta duodecimmaculata)也在壁画和泥塑上筑巢危害；危害古树的主要为白蜡脊虎天牛(Xylotrechus rufilius)等害虫。另外，山斑大头泥蜂(Philanthus triangulum)在山门等处掘土筑巢，造成的危害比较严重。在相关害虫发生期、危害部位和习性调查基础上，综合采用色板、黑光灯、糖醋液诱杀和药物喷洒、注杆、滴孔、药棉填塞、熏蒸等方法，对各类害虫进行了防治，取得良好效果。     

微电脑在二片式对拖网设计上的应用及捕捞效果分析

本文分析了二片式对拖网设计软件设计的基本原理及渔获效果的对比。结果表明,本软件设计先进、科学,具有良好的适用性、精确性、高度灵活性和快速简便性等优点;利用本软件设计的网具,具有良好的渔获效果。     

校园网ARP病毒的应对与防范

如何防范与应对ARP病毒现已成为摆在各校园网网络管理者面前的一个厄待解决的技术难题。本文阐述了ARP协议工作的原理，分析了ARP病毒攻击过程，剖析了ARP病毒对网络的危害，并结合校园网络的架构特点给出了ARP病毒防范与应对的方法。     

一种MELSEC—NOVELL网关的设计与实现

在分析了ＮＯＶＥＬＬ网和ＭＥＬＳＥＣ网的基础，提出一种ＭＥＬＳＥＣ－ＮＯＶＥＬＬ网关的硬件设计实现方法。     

集中供热热网系统节能分析

首先分析了集中供热热网系统能源浪费的表现和程度，进而提出了改造和完善的节能措施。     

Development of an international standard set of barley differential genotypes for Pyrenophora teres f. teres

International comparison of virulence profiles of Pyrenophora teres f . teres (Ptt), the cause of barley net blotch, is seriously restricted by inconsistencies in differential testers used among researchers. This paper reports an attempt to develop an appropriate set of differentials to standardize characterization of Ptt populations globally. Fourteen barley genotypes (Canadian Lake Shore (CLS), Harbin, c-8755, c-20019, Manchurian, Tifang, CI 9825, CI 5791, CI 9819, Beecher, CI 9214, Skiff, Prior and Corvette) were selected from among genotypes previously used as Ptt differentials. Three cultivars (Pirkka, Haruna Nijo and Harrington) were included to identify a universally susceptible control. Genotypes were inoculated with approximately 1000 Ptt isolates from Russia, Europe, Australia and Canada. The mean reaction frequency of genotypes ranged from highly resistant (CI 9819, CI 5791, c-8755 and CI 9825) to highly susceptible (Harrington, Haruna Nijo and Pirkka). The best differential abilities were demonstrated by Harbin, CLS, c-20019, Manchurian and Prior. Application of cluster analyses identified genotypes with similar reaction patterns, which supported a reduction of genotypes in the set. When combined with an algorithm comparing the ability of individual genotypes to discriminate among Ptt isolates, a further reduction of genotypes was justified. A new, concise set of barley genotypes for differentiating virulences in Ptt was formulated. It is proposed that these genotypes be adopted as the standard, international differential set to characterize and identify the virulence properties of Ptt populations across environments. The new Ptt differential set consists of the genotypes c-8755, c-20019, CI 5791, CI 9825, CLS, Harbin, Prior, Skiff and Harrington.     

现代技术在昆虫分类中的应用

介绍形态学、行为学、遗传学、生物化学及分子生物学等几种分类方法在昆虫分类中的应用。     

中国木材市场供给结构分析

文内首先对我国木材市场的变化进行了简单回顾，并从计划内产量、计划外产量、非单板型人造板产量以及木材净进口量四个方面，对我国木材市场供给结构进行了分析；最后，针对我国木材市场供给结构的现状，对其进行了发展趋势分析。     

Productivity and profitability of multistrata organic versus conventional coffee farms in Costa Rica

In areas where traditional multistrata coffee systems have been transformed to systems with patchy or no shade at all, often dependent on high chemical inputs, ecological and socioeconomic degradation has become an increasing issue. During the 1990s, rising environmental and health concerns have promoted the interest in organic production systems and their environmental services for natural resource conservation. This study compared productivity, profitability, producer-defined constraints, and goals and research priorities between ten individually paired organic and conventional coffee farms in Costa Rica. Although five of the organic farms matched or exceeded the production of their conventional counterparts, the three-year mean yield of the organic farms as a group was 22% lower than that of the conventional farms. However, excluding organic certification costs, mean variable costs and net income (NI) were similar for both groups, mainly because organic price premiums received by the farmers compensated for lower yields. If current organic certification costs are included, the price premiums paid to organic producers would have to increase to 38% in order to equal the NI from conventional coffee. Conventional farmers indentified low and unstable prices as the main constraints to sustained production and stated further intensification of production as their main goal. In contrast, the key issues for future development of the organic group centered on farm diversification, agroecological self-sufficiency, and agronomic practices that permit organic farm management. This revised version was published online in June 2006 with corrections to the Cover Date.