浅谈林区便道路基排水现状与养护对策

林区便道养护的关键是解决路基排水问题,根据林区便道路基的排水现状,分析了影响林区便道路基排水的主要因素,并提出相应的养护对策。     

对林区公路路基排水的探讨

本文阐述了路基排水的重要性和必要的措施,着重提出了林区公路基所遭到的各种破坏都是与水有着密切相关的作用。因此路基排水问题必须在实践中享有不可忽视的地位,才能确保林区公路畅通无阻。     

浅议要区公路路基养护

加强林区公路的路基养护是开发林区，加速林业生产建设，保护森林、繁荣山区经济的重要措施。本文对公路路基排水，对坍方地段，沿河地段路基的养护等进行了论述。     

浅议林区公路路基养护

加强林区公路的路基养护是开发林区，加速林业生产建设，保护森林，繁荣山区经济的重要措施。本文对公路路基排水，对坍方地段，沿河地段路基的养护等进行了论述。     

浅谈公路路基排水施工技术

按照公路路基排水的分类就其施工进行了详细的阐述。     

公路排水系统概论

公路建设质量与使用寿命的关键在于排水。路基路面结构内部的含水量必须控制在较低的、不影响其自身强度和稳定的范围内。公路上各种排水设施要相互联系,相辅相成,形成系统的、综合的排水网。     

半填半挖路基设计

半填半挖路基病害较多,在填方一侧又往往被设计者忽略,因此在路基稳定、沉降、排水及路面结构选择上应采取有效的措施。     

公路工程中路基施工技术

从路基的填压、排水、防护等方面入手,对当前广泛使用的施工技术进行总结。     

概论公路排水系统

公路建设的质量与使用寿命的关键在于排水。路基路面结构内部的含水量必须控制在干燥或中湿的状态、以不影响其自身强度和稳定性。     

小桥涵在林区公路中的作用及设计原则

灾后恢复重建林区公路建设工程项目,正在陕西省宝鸡市陈仓区林业系统紧锣密鼓地进行着。林业第一线的工作实践证明,林区公路有无小桥涵、设置是否合理、施工质量的优劣,直接关系和制约着林区公路的畅通以及安全使用。笔者认为,目前林区公路存在最主要、最关键的问题是,林区公路没有或者没有科学合理的排水构造物（小桥涵）。在这里,笔者就小桥涵在林区公路中的作用以及小桥涵设计的一般原则和要求简述如下：     

CAD与建筑设计的关系

本文分析了CAD在设计中引起的正面和负面影响,并进行了系统的阐述,从而使设计者在应用中能够保持客观的态度。     

森林冠层结构与功能及其时空变化研究进展*

林冠是森林与外界环境相互作用最直接和最活跃的界面层 ,同时 ,它本身又承载了森林生物多样性的主体部分。森林冠层研究的方法和技术在近些年取得了长足发展 ,从而促进了有关林冠结构与功能的研究。这些研究深化了人们对于林冠结构与光能截获以及群落干物质积累之间关系的认识 ,同时 ,对于森林冠层的物质循环和能量传输以及冠层内各营养级之间相互关系动态也有了更为深入的理解。考察森林冠层的结构与功能及其时空变化是深入理解整个森林生态系统的格局、过程及其运作机制的重要基础。     

Persistence of herbicides in forest nursery soils

The persistence of the four herbicides atrazine, hexazinone, lenacil and linuron was studied in forest nursery soils. The adsorption capacities of the soils for the chemicals were described by the distribution coefficients kj and k_oc. Due to the low content of organic matter in the soils the k_a‐values were low, in several cases being <1 for hexazinone. Hexazinone also had the lowest k _oc‐value (30) while the other substances had k_oc ‐values within the range 200–400. In some cases hexazinone showed great mobility under field conditions. The formula c=c_o‐kt^1/2 was used to describe the disappearance of the herbicides from the various soils. The rate of degradation of the four herbicides correlated well with the rate of respiration in the same soils in laboratory experiments, and for linuron reasonably well also in field experiments. In the field experiments the herbicides penetrated the top soil layer. In the subsoil the risk of further transport downward to the drainage system or ground water increased, especially for hexazinone. Linuron as well as the fungicides maneb and tolylfluanid suppressed the decomposition rate of hexazinone in laboratory experiments.     

竹大片刨花板对竹材生物学特性的适应性

以云南四种典型材用丛生竹（龙竹、甜龙竹、黄竹和油勒竹）宏观构造、组织结构、主要物理力学性质和化学组份等竹材主要生物学特性的研究分析结果为依据,提出了竹大片刨花板的结构、制板工艺和设备与原料竹材生物学特性之间应有的适应性关系。继而,通过实验室系列化试验和工厂试生产,确定了竹大片刨花板的应有性能和最佳工艺条件包括竹大片刨花的最佳质量指标及其最佳制备条件。     

浅议野生动物所有权

野生动物所有权是所有权的一种,它与其他所有权的区别在于客体的不同。文章阐述了野生动物的内涵,分析了野生动物的分类和野生动物与野生动物资源的区别。在明确野生动物含义的基础上,提出了野生动物所有权的概念,深入论述了野生动物所有权与野生动物资源所有权的差异和联系,并对野生动物所有权的主体、客体、内容进行了分析。     

Log sawing positioning optimization and log bucking of tropical hardwood species to increase the volume yield

The sawmill industry is a very important link in the Mozambique forest products value chain, but the industry is characterized by undeveloped processing technology and high-volume export of almost unrefined logs. The low volume yield of sawn timber has been identified as a critical gap in the technological development of the industry. To improve the profitability of the industry, there is thus a need to develop methods and techniques that improve the yield. In this paper, different positioning of logs prior to sawing and the possibility of increasing the volume yield of crooked logs by bucking the logs before sawing have been studied. A computer simulation was used to study the cant-sawing and through-and-through sawing of the logs to determine the volume yield of sawn timber from the jambirre (Millettia stuhlmannii Taub.) and umbila (Pterocarpus angolensis DC.) species. The optimal position, i.e. the position of the log before sawing that gives the highest volume yield of sawn timber for a given sawing pattern when the positioning parameters, offset, skew and rotation, are considered gave a considerable higher volume yield than the horns-down position. By bucking very crooked logs and using the horns-down positioning before sawing, the volume yield can be of the same magnitude as that obtained by optimal positioning on full-length (un-bucked) logs. The bucking reduces the crook of the logs and hence increases the volume yield of sawn timber.     

Serological marking of <Emphasis Type="Italic">Pnigalio agraules</Emphasis> (Hymenoptera: Eulophidae) for field dispersal studies

The parasitoid wasp Pnigalio agraules (Wlk.) is a key natural enemy of the horsechestnut leafminer Cameraria ohridella Deschka and Dimić (Lepidoptera: Gracillariidae). As a basis for mark-release-recapture studies, aimed at investigating the dispersal of this parasitoid in the field, adults of P. agraules were marked using a vertebrate-specific immunoglobulin (IgG). The marker was later detected by double antibody sandwich enzyme-linked immunosorbent assay (DAS-ELISA). The IgG was either applied externally by spraying or internally by feeding an IgG-enriched diet. Different concentrations of the marker were used and the influence of abiotic (climatic conditions, time elapsed between marking and marker examination) and biotic factors (sex and age of the parasitoids) on the detection of the immunomarker was tested. External marking by spraying led to more homogeneous labelling than feeding the marker. Parasitoids labelled with 0.25 mg rabbit IgG per ten individuals contained enough immunomarker to be easily distinguished from unmarked ones. Neither the climatic conditions nor the sex or age of the insects had an influence on the detection of the marker. The IgG remained well detectable during the entire lifespan of the parasitoids, which was not negatively affected by the marking procedure. Serological marking can be used to investigate the dispersal behaviour of beneficial insects within mark-release-recapture studies.     

大兴安岭森林资源变化分析

阐述了人为破坏、过度采伐和自然森林火灾是引起大兴安岭森林资源变化的重要因子;通过对建国初到2002年大兴安岭森林资源在数量上和质量上的变化分析,得出了森林资源变化趋势。森林资源数量减少,且森林质量下降,大兴安岭的森林在经历着破碎化和年轻化的过程。     

Forests in the Time of Violence

Summary

Forest remnants in the Colombian Amazon, Andes, and Chocó are the last repositories of a highly diverse and endemic biota. Historical changes in the Colombian landscape have been dramatic, but the magnitude and rate of change has increased over the last half century, while conflict has consumed the capacity of Colombian society to respond to environmental threats. Academic experts in the study of the Colombian conflict have explored the social, political, and economic implications of the war. However, the environmental consequences of conflict are documented only when groups in conflict target salient economic resources. This paper presents the first analysis of the geographic distribution of forest remnants in relation to armed conflict in Colombia. Results show that guerrillas and/or paramilitaries range throughout areas of human encroachment into remnant forests. The policies promoted by Colombia's irregular armed forces range from “gunpoint conservation” rarely applied by guerrillas, to the rapid conversion of forests and crops to cattle ranches and coca (Erythroxylum sp.) plantations, following paramilitary occupation. Because the rates and extent of fragmentation are linked to such land use practices, armed groups may play a crucial role in determining the fate of Colombia's forests and their endemic biota.     

Native woody species regeneration in exotic tree plantations at Munessa-Shashemene Forest,southern Ethiopia

Regeneration of native woody species was studied in the plantations and the adjacent natural forest at Munessa-Shashemene Forest Project Area, Ethiopia. The aim of the study was to test the hypothesis that tree plantations foster regeneration of native woody species. A total of 60 plots, having 10 × 10 m area each, were studied in monoculture plantations of 4 exotic species (Cupressus lusitanica, Eucalyptus globulus, E. saligna, Pinus patula) and an adjacent natural forest. Ages of the plantations ranged between 9 and 28 years. Soil seed bank analysis was also undertaken from soil samples collected in each of the 60 plots to examine the similarity between the soil seed flora and aboveground vegetation. A total of 56 naturally regenerated woody species were recorded beneath all plantation stands with densities ranging between 2300 and 18650 individuals / ha in different stands. There was a significant difference among plantation stands with regard to understorey density (standard deviation: 4836 ± 1341). Vegetation diversity was assessed through analyses of floristic composition, species richness and abundance. Generally, seedling populations were the most abundant components of the regeneration in most of the plantation stands, forming 68 % of the total regeneration count in all stands. A total of 77 plant species represented by 44 herbs, 13 woody species, 8 grasses and 12 unidentified species were recorded in the soil seed bank from all stands. Similarity between the soil seed bank and aboveground flora was very low implying that the role of soil seed banks is negligible rather dispersal plays an important role in the process of regeneration. These results support the concept that forest plantations can foster the regeneration of native woody species, thereby increasing biological diversity, provided that there are seed sources in the vicinity of the plantations.