探索低成本连续生产中、高密度纤维薄板和异型板的方式

连续生产中、高密度薄板的方式是采用连续双钢带冷热压机,而国内人造板设备制造行业尚无制造连续双钢带冷热压机的能力。本文依据木纤维薄板矫直原理,提出采用简易连续热辊压压机加矫直机的方案,探索低成本连续生产中、高密度纤维薄板和异型板的方式,以解决实际生产问题。     

国家森林资源连续清查的新进展——关于国家森林资源连续清查技术规定的修订

介绍了对1994年颁布实施的《国家森林资源连续清查主要技术规定》进行修订的背景、指导思想和原则,并对有关修订内容进行了详细说明。     

健康黑松幼苗中的电波传递

以健康黑松(Pinus thunbergii)幼苗为材料,用非伤害性刺激,如冷冻和伤害性刺激,如：烧伤、刺伤、化学伤害等引发了植物体内的波形的变化,研究表明,非伤害性刺激能在幼苗体内引起动作电波的传递,伤害性刺激除了能引起动作电波的传递外,还能引起较为复杂的变异电波的传递并对这种现象进行了讨论。图4参28。     

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.     

输电线路沿线林火监测技术综述

文章阐述了输电线路沿线林火监测的必要性,梳理了林火导致输电线路跳闸的机理,分析了 输电线路沿线林火监测可见光监测技术、红外监测技术、卫星遥感监测技术、激光雷达监测技术、气体 监测技术、燃烧音监测技术的原理、优缺点及其应用,分析认为采用现有单一林火监测技术容易造成沿 线火点的迟测误测漏测;通过两种或多种技术耦合、优化现有监测设备及监测算法等方式能达到及时、 准确地监测林火,展望了输电线路沿线林火监测技术的发展趋势。     

杉木连栽幼林生长量、营养元素和土壤肥力的比较

结果表明：杉木连栽引起林地肥力减退，土壤地力衰退程度与前茬林生长周期有关。头茬杉木林周期短（14a）的二耕土上连栽的杉木长势较好，头茬杉木林周期长（24a）的二耕土上连栽的杉木幼树长势极差。林地施肥后并没有促进杉木幼树恢复生长。原因在于杉木幼树根系受到土壤中有毒物质毒害，根系腐烂，不能从土壤中吸收养分。建议采取生物工程措施解决杉木连裁地力减退问题。     

几个杨树品种低温与变温胁迫对比试验

以几种常见杨树品种为试材,在不同时期进行了低温胁迫试验,通过相对电导率测试及生长恢复情况调查,分析了不同时期低温对杨树发生冻害的影响,结果显示：在冬季树木深休眠期持续的低温对杨树具有一定的伤害,但伤害程度不大;初春树木萌动期低温对杨树伤害较大。根据此结论,进一步开展变温胁迫试验,结果显示：高温和低温的变温对不同杨树伤害较大,而且变化幅度越剧烈,造成伤害越严重。     

基于MATLAB的数字信号基带传输系统仿真

SIMULINK是MATLAB中动态系统建模、仿真和分析的一个集成环境 ,文中按照仿真过程基本步骤用MATLAB的仿真工具SIMULINK实现了数字信号基带传输系统的仿真过程 ,对系统性能进行了分析     

Explaining conifer dominance in Afrotemperate forests: Shade tolerance favours Podocarpus latifolius over angiosperm species

We contrasted the regeneration success of angiosperm canopy species with that of Podocarpus latifolius to test whether this conifer was sufficiently shade tolerant to be favoured on infrequently disturbed and well-shaded sites. Seedling and sapling population structures were measured in several habitats representing a light gradient in warm temperate forest in the Drakenberg mountains of South Africa. The angiosperm-dominated forest was well-shaded (∼5.5% PAR) and lacked ground vegetation. Seedlings of angiosperm canopy species were abundant but the absence of saplings indicated regeneration failure. In contrast, P. latifolius was represented by all size classes beneath the intact canopy indicating continuous regeneration in angiosperm-dominated forest. Angiosperm regeneration was similarly poor in forest gaps, which were dominated by grasses, ferns and vines. P. latifolius entered the advanced regeneration in gaps by establishing in shade before gap formation. The floor of the Podocarpus-dominated forest was less shaded (∼7.5% PAR) than angiosperm-dominated forest and dominated by grass, which suppressed most conifer regeneration. Gaps in Podocarpus forest were more than double the size of gaps in angiosperm forest and dominated by vines and understorey shrubs. There was no clear winner of the angiosperm–conifer contest in Podocarpus forest gaps. Consequently, gaps maintain limited angiosperm diversity in Podocarpus forest. Angiosperm canopy species regenerated continuously in the high light (∼11.5% PAR) thicket environment. Few seedlings of P. latifolius were recorded in the thicket environment. Our findings are consistent with the hypothesis that shaded and infrequently disturbed forest sites favour shade-tolerant conifers over relatively light-demanding angiosperm species. The outcome of the competitive interaction between angiosperm and conifer at the regeneration phase depends on the relative shade-tolerance of associated species.     

森林资源二类调查中小班区划方法研究

通过对森林资源二类调查中小班区划方法进行改进得到连续小班区划方法 ,试验证明这种方法可以节省大量野外调查时间 ,大幅度提高小班界线区划的准确性 ,使小班界线相对稳定 ,调查成果可提供落实到山头地块的森林资源现状和动态变化数据及图面材料