福建林区运材汽车评价模式的探讨

根据福建林区道路状况，结合农用货车性能特点，建立运材汽车评价模式，对福建林区四种有代表性的运材汽车进行了评价、并按综合性能优劣进行排序。研究结果发现：HFC1060为最优车型，NJ1060为次优型。     

拖拉机集材对迹地土壤条件及苗木生长影响的研究(Ⅱ)——拖拉机对集材道苗木生长影响的灰色动态分析

履带式拖拉机和轮式拖拉机由于其走行机构的不同,其集材道土壤压实也存在差异,特别衡量土壤压实的两个重要指标——土壤硬度和孔隙度——两种机型不一致。通过对调查测定数据进行计算处理以及用灰色系统理论进行动态分析,结果表明:与轮式拖拉机相比,履带式拖拉机对苗木生长是有利的。     

Logging pattern and landscape changes over the last century at the boreal and deciduous forest transition in Eastern Canada

Forestry practices associated with the industrial era (since ~1900) have altered the natural disturbance regimes and greatly impacted the world’s forests. We quantified twentieth century logging patterns and regional scale consequences in three sub-boreal forest landscapes of Eastern Canada (117,000, 49,400 and 92,300 ha), comparing forestry maps depicting age and forest cover types for early industrial (1930) and present-day (2000) conditions. Results were similar for the three landscapes, indicating large-scale forest change during the twentieth century. In 1930, previous logging activities had been concentrated in the lowlands and along the main hydrographical network, as compared to a more even distribution over the landscapes in 2000, reflecting a decreasing influence of the environmental constraints on forest harvesting. In 1930, old-aged forests (>100 years) accounted for more than 75% of the unlogged areas of the three landscapes, as compared to less than 15% for the present-day conditions. Logging practices have thus inverted the stand age distribution of the landscapes that are currently dominated by young and regenerating stands. The 1930 forest cover types showed a clear relationship with elevation, with conifers located in the lowlands and mixed and deciduous stands restricted to the upper slopes. Between 1930 and 2000, 58–64% of the conifer areas transformed to mixed and deciduous forests, such that no clear altitudinal relationships remained in 2000. We conclude that twentieth century logging practices have strongly altered the preindustrial vegetation patterns in our study area, to the point that ecosystem-based management strategies should be developed to restore conifer dominance, altitudinal gradients, as well as the irregular structure inspired from old forest stands.     

车外综合温度条件下典型冷藏车厢内热稳定性研究

综合考虑太阳直射辐射、天空散射辐射、地面反射辐射、室外空气温度及车辆运行速度多个因素,采用2阶谐波傅氏级数表达的车外壁面温度函数作为车厢外侧的边界条件,利用热工理论分析与试验验证相结合的方法,分析4种典型冷藏车隔热车厢对温度的衰减与延迟作用,以及厢内热稳定性的影响。结果表明:车厢的隔热材料不同,对车外综合温度的延迟时间与衰减倍数不同,厢体热惰性指标、热阻越大,延迟时间与衰减倍数相应越大;车辆行驶方向、隔热材料不同,车厢体内壁面温度也不同,但都按照正弦规律波动变化,且厢体内壁面温度逐时变化值接近厢内设定空气温度。车厢内的热稳定性主要由厢体隔热材料的热阻与热惰性指标决定,由好到差依次为真空绝热材料厢体、挤塑聚苯乙烯厢体、聚氨酯隔热厢体、聚苯乙烯隔热厢体。     

采伐迹地的火烧清理对土壤理化性质的影响

本文讨论了火烧清理采伐迹地剩余物对土壤理化性质产业的影响，并提出了相应的建议。     

采伐林隙及施肥对林下更新层闽楠生长的影响

为提高林下闽楠更新层营建成效,在福建明溪进行采伐林隙和施肥试验。结果表明,不同采伐林隙对更新层闽楠的树高、地径、冠幅和高径比有着显著性以上的影响。在促进更新层闽楠生长方面,带状间伐林隙更新效果最好,均匀间伐林隙更新次之,直接套种最差。不同施肥处理对更新层闽楠的树高、地径、冠幅和高径比有着显著性以上的影响。在促进更新层闽楠生长方面,带肥造林最好,追肥次之,不施肥(空白对照)最差。研究表明选择带状间伐林隙更新,采用大容器苗造林和带肥造林是林下闽楠更新层培育的关键技术措施。     

Reconstructing 100-150 years of logging history in coastal spruce forest (Picea abies) with special conservation values in central Norway

Coastal spruce forests of central Norway harbour a unique assemblage of epiphytic lichens and are given high priority with respect to conservation of biodiversity. To assess the historical impact of logging during the last 100-150 yrs, 31 remnant stands were studied by means of tree-ring analysis of 2199 trees and the decay stage of 1605 stumps. No stands had been clear-cut, but all had been selectively logged at least twice during the last 150 yrs. Total harvested timber volume ranged from 65 to 409 m³ha-¹ (31-124% of present-day standing volume) and the selective logging kept standing volume low (40-200 m³ha-¹) during 1890-1930. Present-day stand characteristics were strongly correlated with site productivity and topographic position within the ravine valleys. Low amounts of dead wood at sites with high historical logging activity was the only consistent relationship found after covariance of site productivity, topographic position and deciduous trees were taken into account. The results indicate that old-growth stand characteristics, such as reversed J-shaped age distributions and dead wood in advanced decay classes, can be obtained 100-150 yrs after intensive selective logging.     

Analysis of sawn lumber production from logging residues of branchwood of <Emphasis Type="Italic">Aningeria robusta</Emphasis> and <Emphasis Type="Italic">Terminalia ivorensis</Emphasis>

One way of meeting the supply demands of the wood industry is through the reduction of waste in timber processing. It has been estimated in Ghana that for every tree felled, nearly 50% of the tree volume is left in the forest in the form of branches, crownwood, and stumps. In this study, the potential of utilizing branchwood as raw material from logging residues to help meet the timber demands of the downstream processing sector was analyzed experimentally. The sawing characteristics of the branchwood of Aningeria robusta and Terminalia ivorensis with diameters in the range 10–25 cm using live sawing and cant sawing methods were determined using a randomized complete block design, 2 × 4 factorial with three replications. Experimental results indicate that, the relative lumber value yields for first and second grade boards of A. robusta and T. ivorensis branches were 25 and 20%, respectively, while the green lumber volume yields were 40 and 32%, respectively. A high proportion of sapwood and the occurrence of washboarding in T. ivorensis contributed to that species’ relatively low lumber value and volume yield. The experimental results further indicate that the sawing technique used had no significant influence on lumber yields. However, at 5% level of significance, significant differences in lumber yield existed between some of the diameter classes.     

Sedimentation associated with forest road surfacing in a bottomland hardwood ecosystem

Access systems are a necessary element of resource production in bottomland hardwood sites. However, road building may have a detrimental effect on hydrologic function of the site. This report describes initial results of a study designed to examine the effect of different road surfacing treatments on water quality.

Four surfacing treatments installed on two test roads included native soil, native soil with vegetative stabilization, 6 cm of gravel, and 15 cm of gravel over geotextile. During the first flooding season periodic sampling measured floodwater suspended sediments and location of erosion and sediment deposition within the road prism. Initial results suggest that sediment movement was confined to the road right-of-way, with no statistically significant sedimentation effects detected beyond the clearing limits of the road. The study is continuing for another field season.     

Energy and carbon dioxide (CO2) balance of logging residues as alternative energy resources: system analysis based on the method of a life cycle inventory (LCI) analysis

Using the method of a life cycle inventory (LCI) analysis, the energy balance and the carbon dioxide (CO₂) emission of logging residues from Japanese conventional forestry as alternative energy resources were analyzed over the entire life cycle of the residues. The fuel consumption for forestry machines was measured in field experiments for harvesting and transporting logging residues at forestry operating sites in Japan. In addition, a total audit of energy consumption was undertaken. It involved an assessment of materials, construction, and the repair and maintenance of forestry machines as well as the costs associated with an energy-conversion plant. As a result, the ratio of energy output to input was calculated to be 5.69, indicating that the system examined in this study could be feasible as an energy production system. The CO₂ emission per MWh_e (e: electricity) of the biomass-fired power generation plant was calculated to be 61.8kgCO₂/MWh_e, while that of coal-fired power generation plants in Japan is 960kgCO₂/MWh_e. Therefore, the reduction in the amount of CO₂ emission that would result from replacing coal with biomass for power generation by as much as 3.0 million dry-t/year of logging residues in Japan was estimated to be 1.66 million tCO₂/year, corresponding to 0.142% of the national CO₂ emission. This study provides evidence that Japan could reduce its domestic CO₂ emission by using logging residues as alternative energy resources.