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我国木材干燥技术与发展探讨 总被引：7，自引：3，他引：4
详细论述了目前我国各种木材干燥方法的特点、技术水平及生产应用情况。从计算机技术,节能和环保、新技术材料的应用等角度,提出了我国木材干燥技术的发展方向。 相似文献
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<正> 我县硬杂木资源丰富、用途广泛、分类复杂,因此根据产品含水率的需要,对硬杂木混合干燥进行了干燥试验,并达到了工艺技术的要求,最终技术指标完全达到了产品的要求,炉次干燥合格率达到了95%左右。对于硬杂木混合干燥工艺技术来讲,是采用侧向通风,在室内强制干燥进行的技术手段,并按如下三个阶段进行测试的: 相似文献
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南方阔叶树材干燥初期应变特点的研究 总被引：6，自引：2，他引：6
在不同温度和平衡含水率条件下研究南方阔叶树材干燥初期应变特点。试验结果表明，干燥初期表层呈现伸张弹性应变和塑性应变，内层为压缩应变。伸张弹性应变的最大值是产生表裂的主要原因，塑性应变而引起的表层固定变形是产生内裂的原因。 相似文献
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本文研究木材真空干燥。内容包括木材真空干燥机的研制和木材真空干燥工艺的研究。试验结果表明,干燥机设计合理,技术性能良好,能够满足科学研究和小型生产的需要。通过实验,提出榆木、水曲柳、桦木和椴木的干燥基准,证明用真空干燥法干燥厚阔叶树材,具有干燥时间短、干燥质量好的优点。真空干燥具有研究价值,值得在一定范围内推广应用。 相似文献
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根据各种木材的干燥特点，研究设计木材干燥装置，以满足各种树种、规格木材的干燥要求。通过木材干燥装置的应用研究，分析了各种装置的干燥特点，以提高木材干燥质量。降低干燥能耗。 相似文献
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简述了传统热泵木才干燥技术的特性，详细论述了现代热示木材干燥技术的新发展。现代热泵木材干燥技术吸取了常规木材干燥技术的某些优点，具有木材干燥周期越来越短、被干木材质量好和效果明显等特点。 相似文献
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木材干燥应力的研究对丰富和完善木材干燥理论、建立和完善干燥工艺、提高干燥质量和经济效益具有重要意义,许多研究者从不同角度对木材干燥应力应变进行了试验测定及数值计算.本文对其中的主要研究方法进行了较详细的归纳,并对今后的研究提出了看法和建议. 相似文献
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Intr0ducti0nKupicllal1asll1adearevisiol1ofFlciaL.i11tI1ettorldsincel976.Sect.Hcillai11cludcsaboutfiftcensPCcics.Tllel1losttaxaintl1issectionbelOI1gtoAsiansPCcics,wllichdistfibuteinSibcriainRussia,N0rtl1east,NortI1andWestofChina,Mongolia,Japa11andKorca,sucI1asVamoena,VamurensisandV.laI,onicaetc..Tl1rcetaxaal110ngtl1en1,VpiSghrlnis,V'hIm0It)ruInal1dVmpIicamainIydistributeinEuroPe.Vsyh,aIic0aIsodistributesintI1eNortl1ofAsia.Climmosol11enul11bersandkaryotyPes0fAsial1scct.Vicilla… 相似文献
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森林采伐是森林经营中的一个关键环节。采伐对树木天然更新的影响直接关系到森林的结构、组成及森林的可持续经营。本文以长白山阔叶红松林为研究对象,对择伐5 年后不同作业迹地(集材道、楞场和采伐后林窗)的幼苗更新及灌木、草本的多样性进行研究,并以没有进行采伐干扰的林地作为对照。共设计样地23 块,在各个小样地内调查幼树的种类、树木、高度;灌木和草本植物的种类、树木、高度和盖度,应用SPSS 软件进行一元方差分析。结果表明,择伐作业影响幼苗的更新,灌木和草本的多样性在作业迹地增加,尤其在林隙处的多样性最高。适当采伐能促进幼苗的更新,特别是阔叶树种的更新。集材道对幼苗密度的影响比对幼苗高度的影响大,幼苗密度在集材道上密度最高;采伐作业对针叶树种有严重的影响,在三种作业迹地上针叶树种的密度都比对照低。为了维持森林的结构和组成,在森林收获和楞场的建立时,必须采取科学措施保护针叶树种。此外,采伐林窗和楞场的面积都应该减小。为了确保采伐迹地建群树种的更新,经营中应该在保护生物多样性的前提下,适当控制过于旺盛的灌木和草本层的生长。本研究结果将为采伐后作业迹地的恢复和森林的可持续经营提供科学的依据。图1 表4 参14。 相似文献
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IntroductionMaskedciVet(Paguma18vata),Mammalia,Viverridae,ismainlydiStributedinShanxi,Sichuan,Tibet,Yunnanprovinces,etc..Itsmeatisdeliciousandhasspecialflavor.Itiseasytoberaisedartificially,withhighproduCtivity.Nutria(MyocasterCOypus),Rodentia,Capromyidae,originatedinArgentina,Chili,etc.insouthAmerica.Itisakindofherbivoresfur-bearer.itsartificialraisinghassuchmeritsasdurablefurandlowcostandhighproduCtivity.MaskedcivetandnutriahavehigheconomicvalueandwideprospeCtofutilization.Atpresen… 相似文献
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This paper summarises the results from 35 years-observed thinning experiments on 256 permanent sample plots in 10–60 year-old
stands of ash, aspen, birch, oak, pine and spruce in Lithuania. Thinning enhanced crown projection area increment of residual
trees. The largest effect was observed in stands of aspen and birch (growth increase by 200%), followed by ash and oak (over
100%), and spruce and pine (about 80%). Thinning also promoted dbh increment, especially in younger stands, and the increase
of dbh increment was positively correlated with the thinning intensity. The strongest reaction was exhibited by oak and aspen,
while ash, birch and conifers reacted to a lower extent. Low and moderate intensities of thinning stimulated volume production
in younger stands while the opposite was observed in older stands with increasing removals. Spruce stands exhibited relatively
strongest increase of volume increment and pine, –the weakest, while the effect on deciduous species was intermediate. The
results demonstrate that significant increase in volume increment is achievable with thinning of only young forest stands,
e.g. 10–20 year-old pine, birch and ash, or 10–30 year-old oak, aspen and spruce. 相似文献
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Early performance of two dipterocarp species Anisoptera marginata and Shorea parvifolia, and a long-living pioneer species Peronema canescens (Verbenaceae) planted in artificial gaps (size 260 m2) and surrounding untreated stands was studied in a fast-growing plantation of Acacia mangium on an Imperata cylindrica grassland site in South Kalimantan, Indonesia. Forty seedlings of each species were planted at one-meter intervals in lines across each of the five gaps, starting and ending under closed stand. Survival, height and diameter (d0.05) increments were measured, and the effect of gap opening on the composition and abundance of understorey vegetation (grass, shrub and native tree seedlings and saplings) was studied. 19 months after planting, average survival rates were 97% for A. marginata, 94% for P. canescens and 71% for S. parvifolia, with no statistical differences between gap and closed stand. Substantial mortality and damage of dipterocarps were caused by wild boars; minor damage by dieback (for S. parvifolia) and insect pests (for A. marginata). Early growth was clearly influenced by distance from gap centre and light conditions; the growth of seedlings was greater the nearer the seedlings were situated to centre and the higher the level of daily photosynthetic photon flux density (PPFD) was. Gap opening increased the growth of shrub species Chromolaena odorata, but not that of Imperata grass. It also increased the density and height growth of saplings of native pioneer and secondary tree species. Seedling density increased both in closed stand and actual gaps, but was higher inside gaps.Results indicate good prospects for diversifying the composition of fast-growing forest plantations on severely degraded former forest lands and integrating slow-growing valuable species in plantation programs. Both in-depth ecophysiological studies on species-specific growth requirements, and practical oriented research on silvicultural options and economics need further studies. 相似文献
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PtLFY, a LEAFY （LFY） gene, was cloned from Populus tomentosa （LM50） by PCR. Sequencing analysis indicated that PtLFY was 2629 bp long, composed of three exons and two introns and encoded 378 amino acids. The splice donor sites and the splice acceptor sites were in identical positions to the LFY and its homologues. The amino acid sequence inferred was 68%-99% homologous to those of LFY and its homologues by blast analysis in GenBank. The Southern blot analysis indicated that there was a single copy of the PtLFY gene in genomic DNA of male and female P. tomentosa （LM50 and 5082）. The pBI121-Ptalfy （reverse）-intron-Ptlfy-GUS-nos was constructed using RNA interference （RNAi） technique and verified by PCR and digestion identification and transformed into tobacco. Some transgenic tobacco plants were obtained by PCR and PCR-Southern identification. The growth was generally repressed in transgenic tobacco plants compared with wild-type ones and some phenotypic differences were observed. 相似文献
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Guolei Li Yong Liu Lvyi Ma Ruiheng Lv Haiqun Yu Shulan Bai Yaoyao Kang 《Frontiers of Forestry in China》2009,4(3):283-290
Direct seeding is a less expensive practice than planting and has the potential to become a viable alternative to transplanting
for afforestation and regeneration purposes. As an effective and a less costly regeneration method, aerial seeding has been
applied with several tree species. As early as 1956, Chinese people engaged in aerial seeding and stands with a total of 2.97×107 hm2 have been developed up to 2004. Our study tested whether the growth of planted Chinese pine (Pinus tabulaeformis Carr.) seedlings and its undergrowth development in northwest aspects differ from that of aerially sown seedlings on the
northern and northwestern aspects of slopes. In 2007, we collected data such as height, diameter at breast height (DBH), clear
bole height and canopy widths of trees, abundance, coverage, and frequency of shrubs and herbs from 21-year-old planted Chinese
pine stands on a northwestern aspect (PNW), aerially sown stands in a northwest aspect (ANW) and aerially sown stands in a
northern aspect (AN). Results showed that the relation of crown area and mean DBH was best fitted by a double inverse model
for the ANW and AN forests and by a quadratic model for the PNW forest. There was no difference in the growth between ANW
and AN forests, while growth was significantly higher in the PNW forest than in the ANW and AN forests. That was consistent
with the Sorenson diversity indices in the shrub and herb layers, indicating that there was a large number of the same species
in both aerially seeded stands, although their locations were different. Both the number of species in the undergrowth and
the Shannon-Wiener index in the shrub layer were higher in the PNW stands than in the ANW and AN stands. Dominant families
for all three stands were Rosaceae and Compositae in the shrub and herb layer, respectively. The dominant species for all
three stands was Spiraea pubescens in the shrub layer, while the dominant species was different from each other in the three stands. The discrepancy in diversity
and composition of species in the herb layer show that herbs are sensitive to shrubs in the three forests. High mortality
and skewed diameter distributions reflect severe competition and too high a density in the aerially seeded forests. Thus,
aerial seeding is a viable and effective regeneration technique, but management practices, such as thinning, should be applied
to these forests. 相似文献
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Muhamed Adem Adefires Worku Mulugeta Lemenih Wubalem Tadesse Jürgen Pretzsch 《林业研究》2014,25(2):319-328
South Omo Administrative Zone in Ethiopia is home to 18 indigenous ethnic groups whose livelihood is vulnerable due to recurrent drought and degradation. Despite the preliminary observation showing the rich dry-forest resource base that, if sustainably managed could enhance livelihoods and biodiversity conservation, there is lack of empirical data on its current status. We conducted a study aiming at quantifying the population status of gum- and resin-bearing species in two randomly selected districts, Hamer and Bena-Tsemay. Seventy-five quadrats(35 at Hamer and 40 at Bena-Tsemay) each measuring 400 m2 were established along line transects to assess species diversity and equitability, density, frequency, dominance, importance value and population structure. We recorded a total of 27 woody species of 12 families and 14 genera. Fifteen species(9 at Hamer and 14 at Bena-Tsemay) of the genera Acacia, Boswellia, Commiphora and Sterculia, were identified as either major sources of commercial gums and resins or their adulterants. Gum- and resin-bearing species comprised 56% and 57% of species richness, 48% and 50% of total density per ha, 95% and 98% of basal area, and 64% and 56% of importance values at Hamer and Bena-Tsemay, respectively. Diversity of the entire woody species assemblage and of the gum- and resin-bearing species was slightly higher at Bena-Tsemay(H= 2.61, 1.4) than at Hamer(H′= 2.48, 1.28), respectively. The diversity and abundance of the resource base suggest potential for development of value-added commercialization of gum and resins to enhance livelihoods and encourage sustainable management of the forest at these study areas. We recorded, however, declining natural regeneration of most gum- and resin-bearing species, and this calls for integrated and participatory species management and landscape rehabilitation. 相似文献
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PtLFY, a LEAFY (LFY) gene, was cloned from Populus tomentosa (LM50) by PCR. Sequencing analysis indicated that PtLFY was 2 629 bp long, composed of three exons and two introns and encoded 378 amino acids. The splice donor sites and the splice
acceptor sites were in identical positions to the LFY and its homologues. The amino acid sequence inferred was 68%-99% homologous to those of LFY and its homologues by blast analysis in GenBank. The Southern blot analysis indicated that there was a single copy of the
PtLFY gene in genomic DNA of male and female P. tomentosa (LM50 and 5082). The pBI121-Ptalfy (reverse)-intron-Ptlfy-GUS-nos was constructed using RNA interference (RNAi) technique
and verified by PCR and digestion identification and transformed into tobacco. Some transgenic tobacco plants were obtained
by PCR and PCR-Southern identification. The growth was generally repressed in transgenic tobacco plants compared with wild-type
ones and some phenotypic differences were observed.
[Supported by the National Natural Science Foundation of China (Grant No. 30371175) and Postdoctoral Foundation of China (Grant
No. 2002032041)] 相似文献