物种或种群生态位宽度与生态位重叠的计测模型

提出生态位宽度和生态位重叠的新定义及其若干测度模型.对不同学者提出的许多测度生态位宽度和生态位重叠的模型进行分析和评述.迄今为止,在国内限于单一生态资源轴上的生态位参数计测研究很多,随着多维生态位计测方法的不断发展,物种或种群在多维生态空间内的生态位宽度和生态位重叠计测,将备受关注.     

Causes and typical control model of wind-drift sandy lands in abandoned channel of the Yellow River

The historical formation and development of the abandoned channel of the Yellow River is reviewed and its causes of formation and present condition of prevention and control are analyzed in this paper. Based on this analysis, some ideas about control, critical problems and countermeasures in the next period are proposed with two typical control models as examples. We suggest that in preventing and controlling the wind-drift sandy lands in the region, the emphasis should be to develop, with a greatly expanded effort, a recycling economy. This should realize a combination of two ideas, i.e. integrate combating desertification with a structural adjustment of agricultural and an increase in the income of farmers.     

Pseudodynamic tests and earthquake response analysis of timber structures II: two-level conventional wooden structures with plywood sheathed shear walls

Pseudodynamic (PSD) tests were conducted on two-level timber structures with plywood-sheathed shear walls, which each had an opening of different configuration, to study the effects of the mechanical properties of the first and second levels on the earthquake response of the structure. The specimens had two-level conventional post and beam frames that were 3 m wide, 3 m deep, and 6 m high with plywood sheathings nailed on one face of the structure. The first and second levels had different opening configurations of window, door, or slit. Lateral forces were applied at the top of the first and second levels, calculating step by step the next displacement based on the North-South (NS) components of the 1940 El Centro earthquake. The test results were compared with those of the time-history earthquake response analysis using the lumped mass model and hysteresis model presented in the companion article (part I). The experimental and simulated results showed that the simulation by means of the lumped mass time-history earthquake response analysis predicted quite well the response of the first level, but tended to underestimate the response of the second level, and that the PSD tests of an individual wall system with the mass supported by that particular wall generally show a conservative estimate of the response.     

Using model scenarios to predict and evaluate forest-management impacts on soil base saturation at landscape level

Silviculture, forest conversion and technical tools of ecosystem management, such as forest liming, display their effects at the landscape level. Therefore their planning and control should take place at the same scale. The primary objective of this work was to assess soil chemical properties and their changes in relationship to ecosystem management, especially forest conversion and forest liming. We calculated scenario models, based on regression analysis, which allow such an examination in the context of understanding landscape processes which can be expected to operate in the sampling region. Stepwise multiple linear regression analysis was used to predict soil chemical attributes (base saturation, pH, C/N content and stock, exchangeable stocks of Ca and Mg) as indicators of site stability or off-site effects of forest ecosystems such as effects on clean drinking water from forested watersheds. Because of space limitations, in this paper only the modelling results of base saturation are presented. Base saturation was used as an integrative example for other soil chemical properties. The transformation of measurements to the regional scale, i.e., the regionalization, was calculated for the forested parts of two test regions in the Black Forest on the basis of measured chemical properties of 90–150 soil profiles per test region. The models have a spatial resolution of 50×50 m, which is a spatial scale relevant for forestry practice and forest management. Topographic variables (e.g., elevation, aspect, slope gradient, and slope length), the stratigraphic classification of the geologic substrate, stand characteristics from forest inventory data, and finally technical information about forest liming were the auxiliary variables (secondary site properties) that provided indirect information about base saturation and were available for the whole forested area of the test regions. Base saturation could be predicted with an accuracy of ~50–70% (in terms of the multiple R²) by using these properties as predictor variables in multiple linear regression analyses. The explained proportion of variance was unexpectedly high considering the high geomorphological heterogeneity of the two test regions. Based upon the regionalization models, it was possible to establish scenarios showing the landscape-related effects on base saturation that may be achieved by forest conversion towards a higher proportion of forests with broad-leaved mixed stands and by forest liming. These scenarios allow the interactions between several influencing factors and management strategies and the impacts on the target variable to be synoptically judged. Thus the presented regionalization models achieve the role of decision support tools for the planning of forest management at the landscape level. They allow an assessment of the environmental effects of forest management strategies in terms of site sustainability or preservation of water resources in forested catchments.     

Fire protection of a laminated veneer lumber joint by wood carbon phenolic spheres sheeting

Laminated veneer lumber joints made with metal plate connectors were protected with wood carbon phenolic spheres (CPS) sheeting and tested for creep under fire. The effects of the carbonizing temperature of charcoal, used as raw material for the CPS sheets, the thickness, and the location of the sheet on the joint regarding the fire-resistance performance of the joint were studied. The time to rupture of the joints covered with CPS sheets made from charcoal carbonized at 800°C (CPS800) was slightly prolonged compared with that of uncovered joints. On the other hand, the time to rupture of CPS sheets made from charcoal carbonized at 1600°C (CPS1600) was markedly extended. The changes in the charcoal properties due to increasing the carbonizing temperature might be the main reason the CPS1600 sheets had higher fire-resistance performance. The thickness and location of CPS1600 sheets have significant effects on the fire resistance of the joint. A highly fire-resistant laminated veneer lumber joint was obtained using a CPS1600 sheet. The CPS1600 sheet with a thickness of 3mm covering three sides of the joint prolonged the time to rupture 16-fold compared with that of unprotected joints.Part of this paper was presented at the 4th International Wood Science Symposium, Serpong, Indonesia, September 2002     

Estimation of shear moduli of wood by quasi-simple shear tests

A quasi-simple shear test, which is the most direct method for examining the shear properties of sheet metals, has been applied to measure the shear moduli of wood. Buna (Fagus crenata Blume) with variously sized shear regions was used for the test specimens. Strain gauges were mounted in the center of the shear regions to measure the shear strains. The shear tests were carried out to determine the shear moduli in the radial and tangential planes. Apparent shear moduli obtained from the experimental results were corrected by finite element method (FEM) simulation of the shear region, where both shearing and bending are produced. It was found that the corrected shear moduli are roughly independent of test conditions, and their values are in good agreement with the data obtained from bending-shear tests. This suggests that the method employed here can effectively estimate the shear moduli of wood.Part of this research was presented at the 50th Annual Meeting of the Society of Materials Science, Osaka, May 2001     

Screening method for wood extractives: direct cellulose thin-layer chromatography plate

A method for screening wood extractives was developed using cellulose thin-layer chromatography plate (Cell-TLC) separation and was directly applied to bioassays. Wood meal (60 mesh) from nangka (Artocarpus heterophyllus Lamk) heartwood was extracted with hot methanol. The crude extract was separated using a Cell-TLC plate (50 × 50mm). Two broad bands with R_f values of 0.46 and 0.96 were found, and the bands showed completely different effects against the pest termite Coptotermes formosanus Shiraki and the decay fungus Fomitopsis palustris. The band with R_f 0.46 was preferentially consumed by workers of C. formosanus, and it did not show any growth inhibition against F. palustris when the Cell-TLC plate was directly exposed to the organism. In contrast, the band with R_f 0.96 appeared to repel strongly the feeding by C. formosanus and inhibited the growth of F. palustris. It was concluded that the Cell-TLC system was applicable for screening wood extracts consisting of many compounds.     

Bearing properties of engineered wood products I: effects of dowel diameter and loading direction

The embedment tests of laminated veneer lumber (LVL) with two moduli of elasticity (MOE; 7.8 GPa and 9.8GPa), parallel strand lumber (PSL), and laminated strand lumber (LSL) were conducted in accordance with ASTM-D 5764. The load-embedment relation for each of these engineered wood products (EWPs) was established. The directional characteristics of bearing strength (_e), initial stiffness (k _e), and effective elastic foundation depth were obtained from the tested results. The effective elastic foundation depth (=E/k _e,E = MOE), based on the theory of a beam on elastic foundation, was obtained from thek _e and MOE. An of 90° (perpendicular to the grain) was calculated by dividingE ₉₀ [MOE of 90° from the compression test, but MOE of 0° (E ₀), parallel to the grain, obtained from the bending test] byk _e90, the initial stiffness of 90°. This study aimed to obtain the bearing characteristics of each EWP, taking into consideration their anisotropic structures, for estimating the fastening strength of a dowel-type fastener. The relations between the bearing coefficients ( _e,k _e,) on the loading direction and dowel diameter were established from the load-embedment curves. Based on the results of the embedment test, tested EWPs showed different tendencies in all directions from wood and glued laminated timber.Part of this study was presented at the 49th Annual Meeting of the Japan Wood Research Society, Tokyo, April 1999     

STUDY ON THE TREE GROWTH, ARCHITECTURE AND STAND STRUCTURE OF KOREAN PINE PLANTATION

lNTRODUCTIONTherhythInofKorcanpinegrowingandtrpearchitectUreissubjectedtoitsownl1crcd-ityandforeststructUre.Tl1cil11portantefTcctsofgapdynamicsarethereasonsthatmaketl1cKoreanpinetrceformhighqualityoftimbcr.Whilecurrentn1anagemcntofKoreanpincforestmainlyfocusesonpurestand,thccco-logicalrelationshipsbetWcenKoreanpineandothcrsPecicsinaconununityareneglected,thcprimitivebiologicalconditionislost.TheKo-reanpinetrecsinplantationcasilydivergeonthctOpofmainsten1,thesescverelyaITectthcgrOedqu…     

长白落叶松地理变异与种源区的划分

通过长白落叶松种源试验的结果,揭示了长白落叶松的地理变异规律与模式。主要特点是:呈现纬向为主,经向为辅,经纬双重正向的渐变模式。影响长白落叶松地理变异的主导气候因子是温度,其次为水份。利用长白落叶松种源生长与其环境因子线性相关显著的性状,采用主分量分析方法,将长白落叶松划分成四大种源区,即白刀山种源区(编号Ⅰ)、小北湖种源区(编号Ⅱ)大石头种源区编号(Ⅲ)、和白河种源区(编号Ⅳ)。