Tree Stability in Relation to Cyclic Loading

The mechanical behaviour of the soil-root systems of Sitka sprucetrees growing on a peaty gley was measured under cyclic loading,using a specially designed apparatus. The trees were felledat a height of about 1.5 m above the soil surface before testingso that effects due to the stems and the crowns of the treeswere eliminated. The cyclic loading apparatus repeatedly pulledthe top of a stump by a set amount, between 5 mm and 100 mm,at a frequency of about 0.2 Hz. The force exerted on the stumpand the corresponding vertical displacement of the root platewere measured. During a cyclic loading episode, the peak loadin each cycle was less than the peak load in the previous cycle.The size of this difference became smaller with time and wasnegligible after about 25 cycles. The difference in load betweenthe start and end of each cyclic loading episode tended to increasewith stem displacement. A trench was dug around some trees sothat soil failure could be isolated from other effects and sometrees were tested without cyclic loading. Average maximum overturningmoment for the untrenched trees was 15 kN m. Trenching decreasedthis by an average of 10 kN m. Cyclic loading decreased thesoil resistance component of anchorage from 2.3 kN m to about1.7 kN m. The reduction in peak overturning moment with repeatedloading was associated with progressive failure of the anchorage,whereas the differences in anchorage strength between cyclicand static loading were associated mainly with energy dissipation.     

针叶树立木材积测定方法的研究

日本鸟取大学的井上昭夫与黑川泰亨利用孔兹干曲线式推导出一种计算针叶树立木材积的理论二元材积公式V=1/[2(1-Hb/H)]1.060·π/4D2b·H[1,2]。本研究选取4个地区的1014株人工落叶松和樟子松为样本,以部颁二元材积公式的计算结果为参照,对该式进行适用性验证及评价。     

Movement of Injected Dyes in Gymnosperm Stems in Relation to Tracheid Alignment

The path of upward movement of acid fuchsin dye was traced inpole-size stems of Japanese larch (Larix leptolepis Murr.),European larch (Larix decidua Mill.), Lawson cypress (Chamaecyparislawsoniana (A. Murr. Parl.)), Sitka spruce (Picea sitchensis(Bong. Carr.)), Norway spruce (Picea abies (L.) Karst.), andScots pine (Pinus sylvestris L.). In all of these species amarked, preponderantly clockwise spiral pattern of dye ascentwas observed. In general the upward movement of the dye followedtracheid alignment, except at the sapwood-heartwood boundary.The characteristic patterns of dye movement indicated that spiralgrain was much commoner than was straight grain among the pole-sizegymnosperms investigated. Large differences in spiral grainwere found among species, among trees within species, in differentannual rings within trees, and at different stem heights. Patternsof dye uptake were influenced somewhat by the method of injection.Dye injections through tubes driven into the stem were foundmore suitable for determining tracheid arrangement than wereinjections through individual roots immersed in dye. Factorsinfluencing spiral grain development and applications of thedye injection technique to spiral grain determination are discussed.     

柳桉立木力学分析

以柳桉立木为研究对象,重点分析不同状况下桉树应力和弯矩分布情况。结果表明：柳桉立木随着树高的增加,树干断面积呈指数迅速减少,而树干材积和质量均呈一元二次方程的增加。柳桉立木随着树高的增加,树干各截面的应力呈线性降低,而所受弯矩呈非线性减少。外力载荷下作用点与树干基部间各截面的应力会迅速增加,也使得其间的弯矩（绝对值）急剧增大。外力载荷随着树高上移,相对而言不会增加树高基部的应力,但会显著增加作用力位点截面的应力,也显著提高树干基部的弯矩。柳桉在树高3.9 m以上树干部位,由于惯性矩产生的抗弯矩应力能力趋于减少,而小于弯矩应力,易使树干发生变形导致树干折断。     

3种针叶树种树皮抗火性研究

通过测定和分析云南油杉、云南松、华山松3种针叶树种树皮的厚度、导热系数、外界热辐射作用下的失重过程和树皮内表面温度4个因子，结合3个树种在火烧迹地上的死亡率数据，得出如下结论：树皮的结构、导热系数是决定这3种树种耐火性差异的主要因素，3种针叶树种树皮的抗火性由强到弱的顺序为云南油杉〉云南松〉华山松，与这3个树种的死亡率由小到大的顺序相同。     

Pt菌根剂在榆林风沙区针叶树育苗中的应用

利用4种方法将Pt菌根剂应用于樟子松、油松苗木培育中，试验结果表明，Pt菌根剂在榆林风沙区能够促进樟子松、油松苗木的生长，提高苗木的质量。在芽苗截根菌根化育苗和苗木移植培育中效果更为显著。     

针叶树种体细胞胚胎发生影响因素浅析

本文综述了针叶树体胚发生的影响因素,并提出了展望,以期为今后针叶树体细胞胚胎发生体系研究及应用提供参考.     

北票地区3种针叶树容器苗雨季造林技术研究

在北票半干旱地区开展了油松、樟子松和桧柏3种针叶树雨季容器苗造林试验,分别以春季裸根苗造林为对照,结果表明：在北票干旱和瘠薄立地条件下采用容器苗雨季造林,造林成活率超过95%,春季裸根苗造林,成活率仅为65.4%～74.6%。3个针叶树种容器苗雨季造林比对照能够明显提高苗高生长量、主根长、侧根多,与对照相比,油松苗高生长量提高38.97%,地径提高29.9%,主根长提高40.78%,侧根长提高40.76%;樟子松苗高生长量提高37.59%,地径提高31.69%,主根长提高16.89%,侧根长提高20.90%;桧柏苗高生长量提高27.49%,地径提高34.56%,主根长提高18.90%,侧根长提高35.71%。效果十分显著。     

Tolerance of some Broadleaved and Coniferous Forestry Tree Species to Herbicides with Potential for Bracken Control

The tolerance of two broadleaved and two coniferous forestrytree species to overall sprays of three sulfonylurea herbicides,with the potential for bracken control were tested in comparisonwith asulam on outdoor pot experiments, applied at three differentdates. Thifensulfuron-methyl and tribenuron-methyl caused littledamage, however, date of application of these herbicides canaffect the tolerance of some of the tree species. Asulam, usedoutside the recommended time for bracken control, and metsulfuron-methylcaused damage to cherry, oak, Douglas fir and Japanese larch. The tolerance of Sitka spruce to thifensulfuron-methyl and tribenuron-methyl,and a mixture of them applied at six different dates was alsotested. Sitka spruce was not affected at any treatment dateor by mixtures of the two sulfonylurea herbicides.     

Pine Weevil Population Density and Damage to Coniferous Seedlings in a Regeneration Area With and Without Shelterwood

Damage to planted conifer seedlings by the pine weevil, Hylobius abietis (L.), is considered to be less severe in shelterwoods than in clear-cuttings. To evaluate possible reasons for this reduction, this study investigated the relationship between seedling damage and pine weevil population density in the presence and absence of shelter trees. Assessments of seedling damage throughout a full growth season and absolute population density estimates were made at a fresh clear-cutting and an adjacent shelterwood (1 ha each). A grid of 100 pitfall traps was placed over each area, and population estimates were made using the mark–recapture technique. Pine weevil damage to seedlings was about twice as high in the clear-cutting, whereas pine weevil density was estimated to be higher in the shelterwood or about the same in the two treatments (～14?000 weevils ha^?1). Existing differences in microclimate between the shelterwood and clear-cutting did not seem to be the cause of the differences in damage levels. Thus, the hypothesis that seedling damage is reduced in shelterwoods because of increased availability of alternative food remains a candidate for further testing.     

太行山农林复合生态系统中针阔叶树种的选择

应用软系统归纳集成法,确定了太行山主要针阔叶树种生态功能的评价指标体系与权重,其中一级评价指标5个,二级评价指标9个。利用大体一致的200多块样地的调查资料,对太行山广泛分布的针阔叶树种的生态功能进行了分类评价、优劣排序和聚类分析,将评定等级为优良的9种阔叶树和5种针叶树,作为农林复合生态系统建设中可广泛应用的树种,最后从海拔、坡向、年均降水量、气温、土壤等方面总结了优良针阔叶树种的适宜立地条件。     

雨雪冰冻灾害对仙居县林木的危害情况调查

2008年3～4月,在仙居县4个乡镇2个国有林场设置了44块标准地对林木受雨雪冰冻灾害情况进行调查,结果认为：在海拔500m以上,雨雪冰冻造成林木腰折、翻蔸与海拔高程无显著相关,杉类、松类、阔叶类各树种间出现腰折、翻蔸有显著差异;腰折、翻蔸木胸高断面积损失率为松木〉阔叶树〉杉木,断梢木胸高断面积受害率为杉木〉阔叶树〉松木,折枝木胸高断面积受害率为阔叶树〉松木〉杉木,正常林木胸高断面积保存率为杉木〉松木及阔叶树．土层浅薄处林木多出现翻蔸,土层深厚处林木多出现腰折．雨雪冰冻对不同坡向、坡位的林木危害无显著差异,但由于微地形条件,不同地块的林木受害程度差异较大．     

秦岭林区冰雪灾害成因分析与措施

通过对2008年秦岭林区宁东林业局雨雪冰冻灾害分布规律调查,提出林业生产设计的指导性意见,使森林资源在今后的雨雪冰冻灾害中损失最小化。     

The Soil and Roots as Factors in Tree Stability

The paper describes a method of studying the factors affectingtree stability by measuring the forces required to pull treesover. It indicates that Fomes annosus root rot may reduce atree's resistance to overturning by about 30 per cent, and thatdrainage in shallow peat soils can increase resistance by some25 per cent.     

甘肃太子山国家级自然保护区春夏大雪林木灾情调查分析

2016年4月14日和5月13晚间大雪,造成甘肃太子山国家级自然保护区林木受灾。调查结果表明,中林地受灾面积2 768.7 hm2;活立木弯曲、劈裂、折断和倾倒共计609 820株;受灾程度随树种、林种、林分密度、林地土层厚度、立木感染病虫害情况而异。进而分析了晚春夏初降雪致灾的机制,提出保护区今后工作的建议。     

白皮松茎和针叶的电阻抗参数与抗寒性的相关性

用电阻抗图谱法(EIS)和常规的电导法(EL)测定抗寒锻炼期间不同种源白皮松茎和针叶的抗寒性,比较2种方法的相关性,完善 EIS法测定植物抗寒性技术.抗寒锻炼期间,对北京十三陵苗圃的北京蟒山、甘肃两当和山西孝义3个种源的8年生白皮松茎和针叶的抗寒性进行电阻抗法分析和电导法分析.未经冷冻处理的白皮松茎和针叶的阻抗图谱分别用Double-DCE模型和Model-A模型表示.冷冻处理后的样本,用EIS法和EL法测定其抗寒性.未经冷冻处理样本的弛豫时间τ1,(茎)、胞内电阻率r1(茎和针叶)与抗寒性有较高的相关性(R2=0.79～0.86);冷冻处理后的茎和针叶的胞外电阻率re、针叶细胞膜时间恒量τm与抗寒性显著相关(R2=0.92～0.94);EIS法和EL法测定白皮松茎和针叶抗寒性也具有明显的线性相关,但EIS法较EL法低估抗寒性.EIS法是一种测定植物抗寒性的可行方法,尤其用于估测不经冷冻处理样本的抗寒性.     

Components of Tree Stability in Sitka Spruce on Peaty Gley Soil

The stability of 20 m tall trees was investigated by pullingthem over with a winch. The turning moment at the stem basewas resolved into two components, one due to the applied force,and the other to the horizontally displaced weight of the stemand crown. Vertical displacement of the root-soil system wasmeasured and observations made of the progressive failure ofthe soil around and underneath the root-soil plate. When trees were pulled from the crown region, the soil failedwhen the crown had deflected c. 4 rn horizontally and when theapplied force wasonly about 70% of that required for uprooting.By the time that the maximum turning moment at the stem basedue to the applied force had been reached, many roots had broken,crown deflection was c. 8 m and the deflected weight of thestem and crown made a substantial contribution to the uprootingforces. By repeatedly pulling trees during a sequence of cutting orbreaking the roots and soil, the total resistive turning momentafforded by the anchorage was resolved into the following components:i. soil resistance (the resistance to uprooting afforded bythe soil underneath and at the sides of the root system); ii.the resistance of roots placed under tension on the windwardperimeter; iii. the weight of the root-soil plate; and iv. resistanceto bending at the hinge on the leeside. The importance of these components varied between trees andchanged during the course of uprooting. Soil resistance wasthe largest component in the early stages, but when the turningmoment due to the applied force was maximal, the componentsof anchorage were in the order windward roots < weight <hinge < soil resistance. The major effect of the windwardroots on anchorage in these shallow root systems highlightsthe importance of features which interfere with their lateraldevelopment, such as the furrows produced by spaced ploughing.     

The Development of Flutes or Hollows on Main Stems of Trees and its Relation to Bark Splitting and Strip Necrosis

The general problem is discussed mainly on the basis of observationsmade in the forest. It is suggested that the development offlutes or hollows, the dying of bark roughly in strips, andthe longitudinal cracking of bark are all basically determinedby conditions of water transport and supply within the mainstem as this is influenced by the make-up and efficiency ofthe root system and the demand made by the crown. Flutes thusdevelop as the result of a continued, locally occurring andlongitudinally directed, deficiency which does not become acute.Strip necrosis and splitting of bark or wood occur when suchlocal deficiency becomes acute. The idea that shaded, suppressedbranches live parasitically by drawing supplies from the mainstem is discounted and it is considered that there is no adequateevidence to support this view.