Simulating the dynamic behavior of Douglas-fir trees under applied loads by the finite element method

The finite element method of structural analysis was used to model the dynamic behavior of three 20-year-old Douglas-fir (Pseudotsuga menziesii (Mirb.) Franco) trees subjected to applied loading. Detailed measurements of stem and branch geometry were made for each tree, enabling the first-order branches of each tree to be represented as individual cantilever beams attached to the stem. Three values for branch modulus of elasticity (E) were assumed: 4, 5 and 6 GPa. For two trees with relatively large crown masses (175 and 250 kg), significantly improved estimates of natural frequency were obtained when the branches were modeled as separate cantilever beams rather than as a series of discrete masses attached to the stem. Closest agreement with the results from field sway tests was found when branch E was 4 GPa. Oscillations of individual branches contributed to the damping of tree oscillations--a phenomenon known as structural damping--with the contribution increasing as branch E decreased. When branch E was 4 GPa, the phase difference between the oscillation of the stem and that of some branches was almost 180 degrees. We applied a series of forces separately to the stem and branches of each tree and determined the mechanical transfer function for each loading case. These transfer functions were similar to the theoretical transfer function for a damped harmonic oscillator, but showed a smaller tree response at higher loading frequencies, particularly when branch E was 4 GPa. Branch structural properties, particularly modulus of elasticity, appear to be important in defining overall tree behavior under applied loading.     

Estimating the equilibrium position by measuring growth stress in weeping branches ofPrunus spachiana Kitamura f.spachiana cv.Plenarosea

The equilibrium position of a current-year branch of the weeping Japanese cherry,Prunus spachiana Kitamura f.spachiana cv.Plenarosea, was estimated by measuring the released strains of growth stresses. In current-year branches that were supported with wires to prevent weeping as soon as the branches first budded, tensile growth stresses on the upper side were smaller than those of the control branches. Gelatinous fibers were rarely found on the upper part of the cross section of the supported branches, whereas the control branches had many gelatinous fibers on the upper part. The upright orientation of the supported branches was closer to the equilibrium position than the weeping orientation of the control branches. The equilibrium position of the branches was thought to be in the initial bud direction, above the horizontal plane; and the weeping style of branch was not the preferred angular orientation forP. spachiana.     

Utilisation of wood biomass residues from fruit tree branches,evergreen hardwood shrubs and Greek fir wood as raw materials for particleboard production. Part A. Mechanical properties

This paper investigates the potential of utilising wood biomass from fruit tree branches and evergreen hardwood shrubs as raw materials in the production of particleboards when mixed with Greek fir wood particles. The main mechanical properties of the boards made therefrom were determined and compared with those made of typical industrial wood (IW) particles. The highest modulus of rupture and elasticity (30.0 N/mm² and 4330 N/mm², respectively) in bending and screw withdrawal (SW) resistance (127.8 N/mm) were reported for boards made of Greek fir and were downgraded when the fruit tree branches or evergreen hardwood shrub particles also participated. The participation of fruit tree branch particles in proportions higher than 50% improved the internal bond (IB) of fir produced boards, while the highest IB strength (0.95 N/mm²) was reported for boards made of fruit tree branches. Particleboards made of evergreen hardwood shrubs showed inferior mechanical properties compared with those made of IW particles. The latter also showed superior bending strength but inferior SW resistance compared with boards made of fruit tree branches. Hygroscopic and other properties are under determination and will be presented and discussed in the second part of the work.     

板栗低干矮冠多主枝开心形树体结构评价

为探讨低干矮冠多主枝开心树形对板栗产质性能的影响,以10年生‘金丰’板栗为试材,采用将整树冠层分层的方法,研究了低干矮冠多主枝开心树形的树体结构参数及不同冠层间板栗总苞的分布特征。结果表明:在垂直方向上,结果枝和总苞的分布主要集中在树体的中上部,下部有少量分布,其中结果枝和总苞均在1.0~1.5 m层间最多,而每果枝总苞数量在冠层两端最多。在水平方向上,发育枝、结果枝和总苞数量随冠层外移逐渐增多,集中分布于0.5~2.5 m的冠层范围,分别占总量的87.9%、89.9%和88.2%,其中结果枝和总苞在1.5~2.0 m的层间数量最多,体现了该树形立体结果的效果。该树形在保证坚果品质的同时,产量较自然开心形和自然圆头形提高30%以上。     

攀枝花市麻疯树老树特征的初步研究

本文初步研究了攀枝花市不同年龄与生境的麻疯树老树,分析了老树特征与衰老的环境诱导结构限制现象。结果表明：（1）麻疯树衰老树体相对地径（16 cm～62 cm）、树龄（15 a～41 a）、冠幅（3 m×3 m～8.5 m×8.5m）、高度（2 m～6.96 m）较大,一级枝较大,有一定比例的枯死枝;（2）新梢小（枝径0.7 cm～1.12 cm;长度7 cm～28 cm之间）,生长量低,萌生枝稀少,生殖枝比例偏低（趋近于30%以下）;（3）单枝坐果量低（0～3个）,干果重量1.65 g,千粒重490 g,壳比例30%,适合度偏低;（4）生境肥沃时树龄偏大,衰老程度弱,而生境瘠薄时树龄小,衰老程度强烈;（5）不考虑环境异质性,则衰老为树体结构限制的结果,新梢大小小于分支阈值,丧失了树体发育的能力而成为限制生长的因素。综合分析,麻疯树老树指标是分支率,在分支率为1时衰老启动;形态上衰老为环境诱导结构限制的产物,而结构限制可能是衰老的主观因素。     

Tree water storage and its diurnal dynamics related to sap flow and changes in stem volume in old-growth Douglas-fir trees

Diurnal and seasonal tree water storage was studied in three large Douglas-fir (Pseudotsuga menziesii [Mirb.] Franco) trees at the Wind River Canopy Crane Research site. Changes in water storage were based on measurements of sap flow and changes in stem volume and tissue water content at different heights in the stem and branches. We measured sap flow by two variants of the heat balance method (with internal heating in stems and external heating in branches), stem volume with electronic dendrometers, and tissue water content gravimetrically. Water storage was calculated from the differences in diurnal courses of sap flow at different heights and their integration. Old-growth Douglas-fir trees contained large amounts of free water: stem sapwood was the most important storage site, followed by stem phloem, branch sapwood, branch phloem and needles. There were significant time shifts (minutes to hours) between sap flow measured at different positions within the transport system (i.e., stem base to shoot tip), suggesting a highly elastic transport system. On selected fine days between late July and early October, when daily transpiration ranged from 150 to 300 liters, the quantity of stored water used daily ranged from 25 to 55 liters, i.e., about 20% of daily total sap flow. The greatest amount of this stored water came from the lower stem; however, proportionally more water was removed from the upper parts of the tree relative to their water storage capacity. In addition to lags in sap flow from one point in the hydrolic pathway to another, the withdrawal and replacement of stored water was reflected in changes in stem volume. When point-to-point lags in sap flow (minutes to hours near the top and stem base, respectively) were considered, there was a strong linear relationship between stem volume changes and transpiration. Volume changes of the whole tree were small (equivalent to 14% of the total daily use of stored water) indicating that most stored water came from the stem and from its inelastic (sapwood) tissues. Whole tree transpiration can be maintained with stored water for about a week, but it can be maintained with stored water from the upper crown alone for no more than a few hours.     

When branch autonomy fails: Milton's Law of resource availability and allocation

The branch autonomy principle states that the critical characteristics of a branch's carbohydrate economy (photosynthesis, respiration, growth, etc.) are largely independent of the tree to which the branch is attached, as long as light is the primary factor limiting photosynthesis and growth. However, this may not be generally true because in the spring, photosynthates are translocated from a tree stem into branches, and the amount of photosynthate available for translocation should be a function of the tree's canopy status. And the correlative inhibition principle states that a branch's priority for allocation of carbon and other resources is controlled not only by its own environment, but also by its position relative to other branches on the same tree. A study of the lower limit of branch growth and survival in trees of different sizes shows that the latter principle is more important: even though dominant trees have more resources to allocate, branches on suppressed trees are able to grow and produce new foliage at solar irradiances where branches on dominant trees die. Thus branches are sufficiently interdependent that a positive carbon budget by itself does not ensure branch survival; branch position relative to other branches on the same tree is also important. Other findings indicate that this result is quite general: regardless of the stress involved, a stressed branch on a tree where all other branches are also stressed does better than a similarly stressed branch on a tree where some branches are relatively unstressed. Although branch autonomy is an important and useful principle, it is not an absolute rule governing branch growth.     

Support costs of different branch designs: effects of position, number, angle and deflection of laterals

The structural theory for cantilever beams was used to calculate the dry weight of wood that a branch of Picea sitchensis (Bong.) Carr. must produce to support its own weight plus that of laterals in different positions and numbers, and with different angles and deflections. The endpoint of the branch was maintained at 2% of its length, and constant values or functions (measured on real branches) were assumed for Young's modulus, taper and self weights of wood and foliage. Support costs (branch wood dry weights) were minimized when laterals were positioned so that the center of gravity was close to the base of the branch, and when the branch was angled upward from the horizontal. Small savings in support costs also resulted when laterals were not forward pointing, were angled upward and had endpoint deflections of at least 20% of their length.     

树冠结构对主干生长量垂直分配的影响

1985—1986年用定位测量方法研究了Ⅰ-69杨(Populus deltoides Bartr.cv.“Lux”ex.Ⅰ-69/55)树冠结构对主干生长量垂直分配的影响和主干、侧枝生长量分配的关系。结果表明,空旷地与人工林树干生长量分配趋势不同,前者树冠以下主干生长量较大,而后者的大生长量集中在冠部;人工林树干直径增量以地径处最大,向上逐渐变小,从枝下高处又开始增大,直到冠部。冠部树干直径增量一般都大于枝下干部,且呈波动式起伏;断面积与材积增量的分配,以树干基部较大,向上逐渐减小,随着修枝高度的上移,上部材积分配比额增大;侧枝生长影响主干上下生长量的分配,侧枝断面积增加1cm~2,可使分枝部位上下断面积的差值扩大0.7cm~2左右。修枝对调节树干的直径材积生长量分配有显著作用。可以促进树干上部直径材积生长。     

栎木应力木生长偏向性分析

该实验的目的是观察栎木枝条的年轮偏向性和应拉木的显微及化学特性。结果表明,栎木枝桠木髓心偏向上侧,即下侧的生长比上侧迅速。双染色法和SEM的观察发现,胶质层同时发生于枝桠木上下侧的纤维细胞,但上侧的应拉程度比下侧稍显严重。化学分析结果显示,枝桠上下侧的a-纤维素含量仅比正常木高2%~3%,木质素含量仅比正常木低2%~4%。该实验的结论是,栎木枝桠木中反应木同时发生在上下两侧,只是应拉程度有差异,而枝桠木下侧生长迅速造成髓心偏向上侧。     

2种Y形整形方式对‘中梨1号’生长结果的影响

为了解Y形架不同整形方式对梨树生长结果的影响,研究了龙干式和二主枝2种Y形架整形方式下‘中梨1号’梨品种幼树树干直径、主枝直径、早期结果性能、果实品质等方面的差异。结果表明,龙干式整形的‘中梨1号’树干直径、主枝直径、40%以上节位结果枝条数、单株平均结果数等均显著高于二主枝整形的‘中梨1号’,表现出良好的幼树早期丰产性。但龙干式整形的树势相对中庸,果实平均单果质量略小于二主枝整形的‘中梨1号’。除了龙干式的果心占比稍大于二主枝‘中梨1号’,2种整形方式的‘中梨1号’果实在果形指数、果肉硬度和可溶性固形物含量等品质指标上并无显著差异。总体上,龙干式较二主枝式更容易整形,树势更中庸,幼树早期丰产性强,但需要强化水肥管理。     

长白落叶松人工林树冠形状的模拟

以长白山地区 2 6a生长白落叶松人工林为研究对象 ,采用枝解析的方法 ,测定了 2 5株林木 (直径 10 5～2 4 9cm)的树冠变量 ,并建立了预测树冠外侧形状的冠形模型。基于枝条着枝深度 (DINC)和林木变量所建立的树冠形状模型包括 :基径、枝长、着枝角度和弦长等预估模型。对于大小相同树木的主要枝条来讲 ,这些树冠变量是随着DINC的增加而增大 ;而林木的胸径 (DBH)和树高 (HT)变量很好地反映了不同大小树木的冠形变化。冠形预测模型预测效果良好 ,充分体现了树冠结构的变化趋势 :树冠形状在树冠的中上部呈抛物线体 ,而在树冠的下部则为近圆柱体。文中所建模型 ,可以合理地描述长白落叶松人工林的树冠形状及其变化规律。     

银杏树冠结构对主干直径和干形的影响

以19年生实生银杏为研究对象,每木检尺,研究了银杏树冠的结构因子一级侧枝的层性、数量和基径对主干直径和干形的影响,主要结果如下:(1)银杏主干上一级侧枝分布的层性和不均衡,导致了主干不同部位生长量分配的差异,表现为随着树冠高度的增加,一级枝数量在树冠垂直方向上呈现“一年小一年大”的波动式变化;一级侧枝层的层间距在0.58~0.82m之间;某层侧枝数量少时,该层上方的层间距较大,反之亦然。(2)树冠上不同层次的一级侧枝及其数量和基径的差异引起主干直径与材积的不均匀分布,导致树干形质发生变化,表现为一级侧枝的基径随着树冠的高度增加呈现“升高-降低”的变化趋势,且树冠中部的一级侧枝的基径较大;每一轮的侧枝使该层侧枝上部的主干不同程度地变细。随着一级侧枝层的上移,侧枝层使胸高形率呈现缩小的变化趋势。一级侧枝直径生长影响着主干上下部直径增量的分配。     

Analysis of the morphology and structure of crowns in a young sugi (Cryptomeria japonica) stand

Crown form, vertical changes in branch inclination and vertical distribution of foliage density in a young sugi (Crytomeria japonica D. Don) stand were analyzed using allometric equations. Tall trees had deeper crowns than short trees, whereas the crown diameters of both tall and short trees were similar. Apical roundness was more pronounced in the lower-story trees, which were characterized by umbrella-shaped crowns. The vertical distribution of foliage density was approximated by a nearly symmetrical curve. Tall trees had higher spatial densities of foliage than short trees. Branch inclination also varied significantly with tree height. The middle-story trees had the largest branch inclinations and the lower-story trees had the smallest branch inclinations. Even in young uniform stands, crown morphology and structure were modified in response to the light environment.     

A model for the relationship between branch number and biomass in Pinus sylvestris crowns and the effect of crown shape and stand density on branch and stem biomass

The branch biomass of young Scots pines (Pinus sylvestris L.) was inversely related to the branch number per projected crown area giving greater branch density and smaller branch biomass for narrow crowns than for broad crowns. In particular, in dense stands the small share of branches from the total biomass of narrow‐crowned trees was emphasized. The productivity of narrow crowned trees was, however, smaller than that of trees with broad crowns. The concept of the tree ideotype has been discussed on the basis of theoretical calculations.     

沙松扦插繁殖技术研究

以沙松硬枝和嫩枝插穗为材料进行正交扦插试验,研究穗条母株年龄大小、药品种类、质量浓度、处理时间以及基质不同种类、穗条不同类型与不同着生部位对生根的影响,结果表明:影响硬枝和嫩枝扦插生根的主要因素均为穗条母树年龄大小,年龄越小,生根率越高,最优处理组合均为4~10 a母树穗条,用200 mg·L-1ABT1号生根粉浸泡12 h,生根率分别为21.4%、63.9%;嫩枝扦插生根率高于硬枝扦插,差异达到极显著水平。采用1/2珍珠岩+1/2河沙混合基质生根效果最好。穗条不同类型扦插生根存在差异,一级侧枝截制的穗条生根性状优于二级侧枝穗条和顶芽穗条,下部枝条截制的插穗生根率和根系效果均高于上部枝条。     

Changes in shoot allometry with increasing tree height in a tropical canopy species,Elateriospermum tapos

Allometry of shoot extension units (hereafter termed "current shoots") was analyzed in a Malaysian canopy species, Elateriospermum tapos Bl. (Euphorbiaceae). Changes in current shoot allometry with increasing tree height were related to growth and maintenance of tree crowns. Total biomass, biomass allocation ratio of non-photosynthetic to photosynthetic organs, and wood density of current shoots were unrelated to tree height. However, shoot structure changed with tree height. Compared with short trees, tall trees produced current shoots of the same mass but with thicker and shorter stems. Current shoots with thin and long stems enhanced height growth in short trees, whereas in tall trees, thick and short current shoots may reduce mechanical and hydraulic stresses. Furthermore, compared with short trees, tall trees produced current shoots with more leaves of lower dry mass, smaller area, and smaller specific leaf area (SLA). Short trees adapted to low light flux density by reducing mutual shading with large leaves having a large SLA. In contrast, tall trees reduced mutual shading within a shoot by producing more small leaves in distal than in proximal parts of the shoot stem. The production of a large number of small leaves promoted light penetration into the dense crowns of tall trees. All of these characteristics suggest that the change in current shoot structure with increasing tree height is adaptive in E. tapos, enabling short trees to maximize height growth and tall trees to maximize light capture.     

柏木种子园无性系结实性状遗传变异研究

利用柏木一代无性系种子园中15个无性系75个分株材料，研究无性系结实性状的遗传变异规律。结果发现，不同无性系的结实能力差异巨大，其无性系重复力较高。柏木无性系母树结实主要集中在树冠中上部213的树冠层分枝上，其结实量占全株的86％左右。通过性状相关分析，得出理想的柏木种子园高产无性系母树的主要形态特征为：树高中上，树冠浓密适中，冠高长，结实分枝多，树冠上部分枝较长，但下部分枝相对较短，树体外形呈宝塔形。     

Negative gravitropism and growth stress in GA3-treated branches ofPrunus spachiana Kitamura f.spachiana cv.Plenarosea

One of the roles of growth stress in branch shape formation was investigated using a weeping-type Japanese cherry,Prunus spachiana. Negative released strains, caused by longitudinal tensile growth stresses, were detected in the upper side of gibberellin A₃-treated (GA₃-treated) and control branches. The mean value of the released strain in the upper side of the treated branches was –0.104%, which was larger than the value (–0.067%) observed in the control branches. Both branches formed tension wood in the upper side of the xylem, and the treated branches formed tension wood near the pith as well. This suggested that the treated branches generated larger tensile growth stress from the early growth stages. The successive generation of growth stress from the early growth stages was considered to generate forces large enough to bend the branch upward.     

Apical control of branch movements in white pine: Compression wood action

Summary The movements of branches or control stem girdled white pine (Pinus strobus L.) were analyzed using beam theory. The stresses generated in the compression wood (CW) produced bending moments to counter the added bending moments due to new branch growth. The branches on the treated trees produced additional CW after untreated trees stopped elongation and diameter growth. The intensity of the stresses in this additional CW was greater than in the other CW. Thus, branches on treated trees moved up vertically well beyond their initial orientation due to both more CW and more active CW. The branches on untreated trees all deflected downward as branch weight continued to increase after CW production stopped.