共查询到20条相似文献，搜索用时 69 毫秒
1.
2.
W. Michael Aust Stephen H. Schoenholtz Thomas W. Zaebst Beth A. Szabo 《Forest Ecology and Management》1997,90(2-3):161-169
Three disturbance treatments were imposed on a palustrine forested wetland (Nyssa aquatica-Taxodium distichum) located in southwestern Alabama in 1986: (i) clearcutting with helicopter log removal (HELI), (ii) HELI followed by rubber-tired skidder traffic simulation (SKID) and (iii) HELI followed by removal of all vegetation during the first two growing seasons via glyphosate herbicide application (GLYPH). After two growing seasons, it was hypothesized that eventual woody plant growth would be best in the HELI-treated areas, because SKID plots had reduced rates of water movement and soil aeration. However, measurements at stand age seven years indicate that SKID actually has greater total above-ground biomass (65979 kg/ha) than HELI (46748 kg/ha) and SKID plots have a higher proportion of the most desirable timber species (Nyssa aquatica). GLYPH areas resemble freshwater marshes, although the areas are being invaded by Salix nigra seedlings. All disturbance treatments have significant groundflora components that have increased sediment accumulation 70–175% relative to an undisturbed reference area. By age seven years, regrowth of vegetation has lowered the water table during the growing season but has had little effect on soil redox potential and pH. Our observations suggest that this wetland system is rapidly recovering from logging disturbance seven years ago. 相似文献
3.
Motoshi Hiratsuka Takeshi Toma Nina Mindawati Ika Heriansyah Yasushi Morikawa 《Journal of Forest Research》2005,10(6):487-491
Biomass of a mature man-made forest in West Java, Indonesia, was estimated to evaluate the carbon sequestration potential
of plantation forest in the humid tropics. Twenty plots, each 0.25 ha in area and containing one to six planted species over
40 years of age and with closed canopies, were selected. Trunk dry mass was estimated from trunk diameter, tree height, and
bulk density. Maximum trunk diameter (122 cm) was observed in a 46-year-old Khaya grandifoliola C. DC. tree, and the tallest tree (51 m) was a 46-year-old Shorea selanica (DC.) Blume. The largest trunk biomass (911 Mg ha−1) was achieved in the plot composed of two Khaya spp. Among the plots composed of indigeneous Dipterocarpaceae species, the largest trunk biomass was 635 Mg ha−1. These trunk biomasses were larger than those reported from primary rainforests in Southeast Asia (e.g., 403 Mg ha−1 in East Kalimantan, 522 and 368 Mg ha−1 in Peninsular Malaysia). The large biomass in this forest suggests that, given favorable conditions, man-made forests can
accumulate the quantities of atmospheric carbon that were lost by the logging of primary forests in the humid tropics. 相似文献
4.
Over the last three decades the exportation rate of raw sawlogs from Illinois to neighboring states for processing has nearly doubled. While the exportation of sawlogs has adverse impacts on the Illinois wood products manufacturing sector and local forest landowners, little research has been conducted to understand how the spatial arrangement of timber mills affects sawlog exportation. This research models, in a spatial environment, timber mill procurement influence within southern Illinois and the surrounding region in an attempt to understand how the location of mills is a partial explanation of the increase in sawlog exportation. Assuming equal market power, timber mills within the study area were found to be arranged in a manner that results in low competition for sawlogs within Illinois and high competition in neighboring states. Spatial models incorporating differential market power based on mill size characteristics suggest that Illinois experiences little procurement pressure from high production mills operating within the State but is under procurement pressure from high production timber mills operating in neighboring states. 相似文献
5.
随着"一带一路"倡议的提出,我国越来越多的企业加入到跨境发展当中,对全球经济和社会发展产生了深刻影响。由于我国木材加工企业跨境发展的时间较短,在很多方面缺少足够的经验,对风险的实际应对能力有待提高。针对当前我国木材加工企业跨境发展的现状和存在的问题进行了分析,进而针对性地提出了相关策略,这对于提升我国木材加工企业的整体跨境发展水平和跨境竞争力等具有重要意义。 相似文献
6.
在木家具结构设计中,特别是具有中国传统家具风格的实木家具结构设计中,木框角部斜角榫接合强度是人们既关注又无法回避的问题。抗拉强度和抗弯强度是衡量木框斜角榫接合性能高低的两个重要指标。笔者对三种常用的、易于机械加工的斜角榫接合试件的强度(抗拉强度,抗弯强度)进行了实验测定,并从各个方面对其进行比较、分析。研究结果表明:斜角榫接合形式,胶黏剂种类,加压时间等各个因子都不同程度地影响着木框角部接合的整体结构性能。单肩斜角明榫接合效果最好。 相似文献
7.
家具生产企业是我国制造业的重要组成部分。随着我国家具进出口贸易的不断发展,国际木材价格波动对我国家具生产企业的发展造成了严峻挑战。基于国际木材价格波动现状,分析国外木材原料的价格波动特征对国内木材原料市场异常价格波动带来的影响,以规避潜在的市场风险,促进国内家具企业的发展,在此基础上,有针对性地提出对策建议。 相似文献
8.
Ali Awaludin Takuro Hirai Toshiro Hayashikawa Yoshihisa Sasaki 《Journal of Wood Science》2008,54(5):362-368
Previous experimental studies reported that bolt pretensioning greatly increases the initial stiffness and load-carrying capacity
of bolted joints. It is also a matter of great importance to structural designers to understand the effect of pretension on
the load-carrying capacities of bolted joints, and this study presents an extended yield model that considers the fastener’s
pretension force. In the extended yield model, the load-carrying capacity was defined as the load at a slip of 15 mm. The
ultimate fastener bending angle at the yielded cross section equivalent to this joint slip, which was affected by the fastener’s
axial force, was iteratively evaluated in numerical analyses. The introduction of bolt pretensioning largely increased the
joint slip resistance at initial loading, but it decreased the ultimate fastener bending angle. This decrease of fastener
bending angle resulted in a relatively low stiffness hardening (or secondary stiffness), which is caused by secondary axial
forces associated with embedment of steel plates into the wood member. Prediction was verified by the tests of 36 steel-to-timber
joints under three different pretension forces and two loading directions relative to the grain. Some of the observed load-carrying
capacities of the joints, particularly in loading perpendicular to the grain, however, were not as high as those expected
by the numerical analyses considering the given pretension forces. 相似文献
9.
杉木生长,材性兼优种源选择的研究 总被引：4，自引：1，他引：3
经对杉木中心产区优良种源的中间试验研究表明,种源间生长与木材基本密度性状有一定差异,根据对１２年木材基本密度性状和９年材积生长性状的测定结果,初步选出广西那坡,贵州锦屏,贵州榕江等生长,材性兼优的种源。其木材基本密度与广西融水优良种源相近,材积生长比融水种源增加４７．０％￣８３．６％,遗传增益达１３．４１％￣２３．８６％。 相似文献
10.
The development of mixed broadleaved-Korean pine (Pinus koraiensis Sieb. et Zucc.) forests in the Changbaishan Biosphere Reserve, located on the border with North Korea, was simulated using the gap model KOPIDE. Forest succession was simulated under three initial conditions from: (1) bare ground after clearcutting; (2) secondary forest; (3) old-growth forest. The simulations from the different initial conditions converged and support earlier successional theory that Korean pine is the climax species on the highlands of northeast China even under disturbed conditions. In addition to clear-cutting, the resilience of the forest to different levels of other human impacts, pine seed harvesting and selective cutting, was examined. These results further demonstrate that these forests possess a relatively stable structure characterized by the dominance of Korean pine. However, the model showed successional processes of the forest to be susceptible to high levels of pine seed harvesting. To predict forest dynamics at landscape scales, KOPIDE was linked with a Geographic Information System containing site and stand data sets. Running this model to simulate a forested area initially comprising several successional stages suggests that, in the absence of disturbance, Korean pine is likely to become increasingly dominant on the area over the next century. 相似文献
11.
M.H. Wishnie D.H. Dent E. Mariscal J. Deago N. Cedeño D. Ibarra R. Condit P.M.S. Ashton 《Forest Ecology and Management》2007
Decades of deforestation and unsustainable land use have created large expanses of degraded lands across Central America. Reforestation may offer one means of mitigating these processes of degradation while sustaining resident human communities. However, a lack of information regarding tree species performance has been identified as an important limitation on the success and adoption of diversified reforestation strategies. We analyzed the initial growth of 22 native and 2 exotic tree species planted at three sites across a precipitation gradient in the Republic of Panama (1100–2200 mm year−1), and identify promising species for use in forest restoration, timber production and on-farm systems. 相似文献
12.
林分材积计算的标准木方法的误差分析及校正 总被引：1，自引：0，他引：1
在指出了森林林分材积计算的标准本方法偏低估计实际材积的系统误差的基础上，提出了两种校正方案。校正系数可以从在林分内选择标准木的采样样本的数据中方便地算出。模拟举例计算说明两种校正方案基本消除了原公式的系统偏差。校正后的公式为：其中：为林分材积估计值；ＶＢＫ和ＡＢＫ分别是第Ｋ株标准木的测量材积和胸高断面面积；ＡＴ是林分的总胸高断面面积：ｈＢ，和ｄＢ是抽样算得的具有平均胸高断面面积的树的高度和胸径；ｄＷ是抽样算得的以胸高断面面积为权重的加权平均胸径；ｂ是树高曲线在ｄ＝ｄＢ处的斜率。校正的第２方案具有与上式完全相同的形式，只是标准木的是具有平均胸径的树木。 相似文献
13.
小议提高用材林森林生产力的途径 总被引：1，自引：0，他引：1
通过选用适当的培育方式、遗传改良、林分结构的配置、立地的选择和调控等4个方面的分析论证,论述了寻求提高用材林的森林生产力的途径。 相似文献
14.
本文应用模糊综合评判理论,通过对影响森工企业木材运输经济效益的各种因素进行综合分析,确定出木材运输经济效益的主要影响因素,建立评价木材运输经济效益的数学模型,最后进行实例验证以得其模型可行性。 相似文献
15.
Zhang Shirun Bian Liping Northeast Forestry University 《林业研究》1993,4(1):53-59
The amount of CCA fixed in the southern pine treated with CCA have been eval-uated.The conclusions from these experiments are:with the timber density increases,the reten-tion based on weight/weight will decrease,but the retention based on weight/volume will bealmost constant.Retention by weight would be more influential than by volume. 相似文献
16.
论述贵州现用一元立木材积表存在的问题和误差来源，对原材积式与新材积式进行误差对比及适用性检验。提出立木材积式的选择、误差修正的方法与应用和重编材积表的紧迫性。 相似文献
17.
18.
19.
结合海南木材经营加工的现状,分析木材经营加工和管理中存在的问题,针对性的提出推进全省木材经营加工和管理的基本对策。 相似文献
20.
本文对福建省贮木场的发展历史进行扼要回顾,分析和评述了木材市场开放后福建省贮木场的现状,针对发展中存在的问题,并紧紧围绕经济发展的两个根本转变,对贮木场的发展出路提出看法。 相似文献