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1.
The stand density of a forest affects the vertical distribution of foliage. Understanding the dynamics of this response is important for the study of crown structure and function, carbon-budget estimation, and forest management. We investigated the effect of tree density on the vertical distribution of foliage, branch, and stem growth, and ratio of biomass increment in aboveground tissues; by monitoring all first-order branches of five trees each from thinned and unthinned control stands of 10-year-old Chamaecyparis obtusa for four consecutive years. In the control stand, the foliage crown shifted upward with height growth but the foliage quantity of the whole crown did not increase. In addition, the vertical distribution of leaf mass shifted from lower-crown skewed to upper-crown skewed. In the thinned stand in contrast, the foliage quantity of individual crowns increased two-fold within 4 years, while the vertical distribution of leaf mass remained lower-crown skewed. The two stands had similar production rates, numbers of first-order branches per unit of tree height, and total lengths of first-order branches. However, the mortality rate of first-order branches and self-pruning within a first-order branch were significantly higher in the control stand than in the thinned stand, which resulted in a higher ratio of biomass increment in branch. Thinning induced a higher ratio of biomass increment in foliage and lower in branch. The increased foliage quantity and variation in ratio of biomass increment after thinning stimulated stem growth of residual trees. These results provide information that will be useful when considering thinning regimes and stand management.  相似文献   

2.
用竞争密度(C—D)效应的倒数式(即t/w=Api B，式中w和pi分别为平均单株材积和密度，A和B为系数)分析了I-72杨林的生长过程。在双对数图上，I-72杨林各生长阶段的平均单株材积和密度的观察值很好地吻合了竞争密度效应曲线，竞争密度效应曲线随时间的推移向上移动。通过分析得出了生物时间τ(逻辑斯蒂生长曲线中生长系数λ(t)的积分)，系数A和B，生长系数λ(t)和最终收获量Y(t)的变化趋势及系数A和B的生物学意义。生物时间τ随着物理时间t的增加而增加。随着τ的增加，系数A急剧增加到最大值后逐渐下降，而系数B呈指数下降，倾向于接近零。随着林分的生长，生长系数λ(t)倾向于下降，而最终收获量Y(t)逐渐增加。以C-D效应为基础，提出了对高密度的7a生I-72杨林进行间伐的建议。  相似文献   

3.
The allometric relationships between mean weights of components, such as stems, branches and leaves and tree weight as well as their time-trajectories, were studied with data of self-thinning Pinus densiflora stands with different densities. The allometric relationships existed between the weights of stems, branches and leaves and the tree weight during the course of self-thinning. The stem weight ratio increased with increasing tree weight because the allometric coefficient in stem was higher than unity, whereas the branch weight ratio and the leaf weight ratio decreased because the allometric coefficients in branches and leaves were less than unity. An allometric power relationship existed between mean component weight and mean tree weight during the course of self-thinning. The time-trajectory of mean component weight (w o) and density (ρ) in the early growth stage was expressed as a mathematical model which incorporates the allometric power relationship into the Tadaki’s model, whereas the model for describing w o-ρ trajectory in the later growth stage was derived by combining the allometric power relationship with 3/2 power law. The two models, Tadaki’s model and 3/2 power law, showed a good fit to data from P. densiflora stands. The time-trajectories of mean tree weight (w)-density (ρ) or w o-ρ initially almost moves nearly vertically in the low-density stand, moves along a steep curve and an inclined curve in the medium- and high-density stands, respectively, and gradually approaches self-thinning line in the early stage of stand development, whereas they reached and moved along the self-thinning line in the later stage of stand development. The self-thinning exponents were determined to be 1.71, 1.19 and 1.13 for the trees, 2.38, 1.33 and 1.20 for the stem, 3.16, 1.55 and 1.46 for the branches, 2.66, 1.39 and 1.35 for the leaves in the low-, medium- and high-density stands, respectively. The 3/2 power law of self-thinning is derived on the basis of simple geometric model of space occupation by growing trees, but allometric growth of tree and components can make the slope of the self-thinning line being different from −3/2. The reasons that the self-thinning exponents of components in the low-density stand were greater than those in the medium- and high-density stands were discussed.  相似文献   

4.
林分密度对桉树幼龄能源林的影响   总被引：3，自引：0，他引：3  
对0.5年生3种不同密度配置的幼龄尾巨桉优良无性系DH32-29各器官生物量、热值以及灰分进行了调查和测定,结果表明:所选3种密度间树高差异显著,基径差异达到极显著水平,随着密度的增加,树枝、叶片、树干的生物量分别呈现减少趋势,密度与树枝和树干生物量的相关性达到了0.01极显著水平;单株生物量随密度的增大而减小,林分生物量则相反;单株热值无显著差异,仅单株平均灰分含量高密度与中密度存在显著差异。综合分析,高密度0.25 m×2 m林分生物量最大,其灰分含量比低密度的林分低,适合作为能源林培育密度。  相似文献   

5.
An allometric model of the maximum size–density relationship between mean stem surface area and stand density is proposed, and is fitted to data for even-aged pure stands of Japanese cedar (Cryptomeria japonica D. Don) and Japanese cypress (Chamaecyparis obtusa Endl.). To derive the model, the biomass density was defined as the ratio of the mean stem surface area to the side area of an imaginary column, of which radius and height were equal to the radius of the mean area occupied by a tree and mean tree height, respectively. According to the model, the slope of the maximum size–density relationship on logarithmic coordinates can be estimated from the allometric power relationships of mean tree height and biomass density to mean stem surface area. The resulting slope was −1.089 for the cedar and −0.974 for the cypress. The estimated maximum size–density relationship corresponded well with the combinations of mean stem surface area and stand density for the overcrowded stands of cedar and cypress. The steeper slope for cedar was attributed to the allocation of more resources to height growth compared to cypress. The maximum total stem surface area was approximated to be 1.483 ha/ha for cedar and 0.949 ha/ha for cypress stands. The difference in the maximum total stem surface area between the two species was produced by the characteristics related to tree height and stem biomass packing into space already occupied.  相似文献   

6.
不同林分密度楠木人工林生物量初步研究   总被引：3，自引：1，他引：2  
对福建省顺昌埔上国有林场不同林分密度的37年生楠木人工纯林的生物量及分配进行调查和分析,结果表明:低密度林分(1 500~1 650株.hm-2)楠木单株标准木的平均生物量为56.52 kg.株-1,是高密度林分(2200~2400株.hm-2)的1.39倍。单株标准木各器官的平均生物量均随林分密度的增加而减小;楠木人工林乔木层生物量随林分密度的增加而增大,乔木层总平均生物量在干材中的分配基本不受林分密度的影响(低密度的为53.59%,高密度的为53.72%),在根、皮中的分配比例随林分密度的增大略有增大,而在枝与叶中的分配比例则随密度的增加而下降。各器官生物量均存在干材>根>皮>枝>叶这一规律,其中干材生物量占总物量的比例最大,均超过了50%,最大达到61.11%。  相似文献   

7.
采用以空间代时间的径级标准木收获法,研究了从幼林到成熟林的5种不同林龄的林分生物量.结果表明:树木干物质是按一定比例分配到各器官,其比例与径阶大小无关,而与发育阶段有关.林分平均木及林分各器官生物量均随林龄增加而增加,平均木在18 22a生物量年增加速率最大,而林分是在12 18年生.树干生物量所占百分比(占48%以上)随林龄增加而增加,而枝、叶、皮刚好相反,18年生以前,根所占百分比随林龄增加而下降,此后趋于稳定.各器官所占百分比由大到小依次为:干、枝、根、皮、叶.8、12、18、22、30年生的林分乔木层生物量分别为:33.94、89.94、204.51、223.71、234.14t.hm-2,净生产力为:6.24、11.14、15.63、14.07、11.93t.hm-2.a-1.中龄前,生物量按径阶分布的规律与株数按径阶分配规律相似,多呈左偏态,此后呈右偏态,峰值比株数按径阶分布向右移动1 2个径阶.培育纸浆材林,在18年生前利用最佳.  相似文献   

8.
Forest floor characteristics influence nutrient cycling and energy flow properties of forest ecosystems, and determine quality of habitat for many forest plants and animals. Differential crown recession and crown development among stands of differing density suggest that an opportunity may exist to control the input of fine woody litter into the system by manipulating stand density. The objective was to measure the rate of branch mortality among stands of differing density and to estimate the range in total per hectare necromass inputs. Although litter traps are reliable for estimating per hectare rates of litterfall, branch mortality dating on sectioned stems uniquely allows assessment of several other litterfall components: (1) individual tree contributions to total litterfall; (2) the amount of branch material released by mortality, regardless of whether the branches are shed to the forest floor; (3) the distribution of basal diameters characterizing the litterfall from a given tree and stand. Twenty-four trees were felled and sectioned on permanent plots that were part of a silvicultural study of stand density regimes in Douglas-fir (Pseudotsuga menziesii (Mirbel) Franco.). Whorl branches were dissected out of bole sections to determine the dates of mortality, and a branch biomass equation was applied to estimate potential rate of litterfall. Periodic annual rates were expressed in four ways: (1) number of branches per tree; (2) mass of branches per tree; (3) mass of branches per unit of crown projection area; (4) mass of branches per hectare. For the growth periods investigated, larger trees and trees growing on denser plots tended to release a greater necromass through branch mortality. Average branch basal diameter generally decreased with increasing stand density. Annual branch mortality ranged from 33 to 430 g m−2 crown projection area for individual trees, and from 236 to 1035 kg ha−1 for individual plots. These rates approached the low end of the range of previously published fine litterfall rates for Douglas-fir. Rates on these plots were relatively low owing to the temporary delay in crown recession imposed by artificial thinning. A conceptual model of branch litter dynamics is presented to depict consistencies with crown development among stands managed under different density regimes.  相似文献   

9.
Growth and yield models were developed for individual tress and stands based on336 temporary plots with 405 stem analysis trees of dahurian larch(Larix gmelinii(Rupr.)Rupr.)plantations throughout Daxing’anling mountains.Several equations were selected using nonlinearregression analysis.Results showed that the Richards equation was the best model for estimatingtree height,stand mean helght and stand dominant height from age; The Power equation was thebest model for prediction tree volume from DBH and tree height; The logarithmic stand volumeequation was good for predicting stand volume from age,mean height,basal area and other standvariables.These models can be used to construct the volume table, the site index table and other for-estry tables for dahurian larch plantations.  相似文献   

10.
Both stem and crown mass affect tree resistance to uprooting   总被引：1，自引：0，他引：1  
To examine the hypothesis that both stem and crown mass affect the resistance of a tree to uprooting and that tree resistance increases with increasing crown mass, we conducted tree-pulling experiments on three Picea glehnii plantations (stands A, B, and C: 27–32 years old) that differed in tree density and slenderness ratio. Allometries between crown and stem masses and between the critical uprooting moment and stem mass differed significantly among the three stands, with the crown mass and critical moment significantly larger in stand C than in stands A or B, despite the same stem mass. These results quantitatively verified our hypothesis. Allometries between crown and stem masses and between critical uprooting moment and stem mass were highly significant in each stand but were stand specific. Therefore, these allometries can be used to estimate tree resistance to uprooting in a given stand but not for data compiled from stands of various conditions and tree shapes. The allometry between critical moment and aboveground mass did not differ among the three Picea stands; thus, it is not stand specific and is generally appropriate to use for estimating tree resistance. To increase tree resistance to uprooting, we recommend light management for Picea glehnii plantations and probably other coniferous plantations as well.  相似文献   

11.
We quantified structural features and the aboveground biomass of the deciduous conifer, Metasequoia glyptostroboides (Hu and Cheng) in six plantations in central Japan. In order to derive biomass estimates we dissected 14 M. glyptostroboides trees into three structural components (stem wood, branch wood and foliage) to develop allometric equations relating the mass of these components and of the whole tree to diameter at breast height (DBH). We found robust relationships at the branch and whole tree level that allow accurate prediction of component and whole tree biomass. Dominant tree height was similar within five older (>40 years) plantations (27–33 m) and shorter in a 20-year-old plantation (18 m). Average stem diameter varied from 12.8 cm in the youngest stand to greater than 35 cm in the oldest stand.

Metasequoia have relatively compact crowns distributed over the top 30% of the tree although the youngest stand had the deepest crown relative to tree height (up to 38%). At the individual tree level in older stands, 87% of the aboveground biomass was allocated to the stem, 9% to branch wood and 4% to foliage. We found little difference in the relative distribution of above ground biomass among the stands with the exception of lower foliage biomass in larger diameter trees. Total aboveground biomass of the older stands varied twofold, ranging from a maximum of 450 Mg ha−1 in a 42-year-old stand to a minimum of 196 Mg ha−1 in a 48-year-old stand. Total above ground biomass of the 20-year-old stand was 176 Mg ha−1.  相似文献   


12.
Interrelationships between self-thinning, biomass density, and plant form were mathematically modeled in relation to stand development in which self-thinning is either not occurring or is occurring. The relationship between biomass density and mean shoot mass is derived as a simple power function at the stage when self-thinning does not occur. When self-thinning occurs, constant biomass density is attained when the 3/2 power law of self-thinning applies and the allometric coefficient is assumed to be 1/3 in the allometry between mean plant height and aboveground mass. The applicability of this mathematical model and the allometric reformulations of the self-thinning exponent were tested using experimental data for dense populations of Chamaecyparis obtusa seedlings during the first 2 years of growth. On the basis of the results of the present model and experimental data, the dependence on competition of the mean height:diameter ratio, mean stem diameter, and leaf biomass density are discussed. As a result, the mean height:diameter ratio was almost asymptotically constant at the latter growth stage in the second-year seedlings, so that the 3/2 power law of self-thinning was held in the present analysis. However, the value of height:diameter ratio will become smaller in older stands, because tree height is considered to be asymptotic with respect to tree age due to hydraulic and other limits. Therefore, the present modeling implies that one of the reasons why the 3/2 power law from a geometric basis has been recently rejected depends on whether or not the height:diamter ratio is constant in older trees.  相似文献   

13.
In young sugi (Cryptomeria japonica D. Don) stands, crown shape (crown length/crown diameter) ratio, average branch inclination, and spatial density of foliage in the crown increased with stand age. Within crowns, foliage distribution increased from the apex downward and, until crown closure, reached a maximum near the crown base. After crown closure, the maximum occurred near the middle of the crown. In each stand, foliage distribution in the canopy showed almost the same vertical change over time as it did in individual crowns. The vertical distribution of foliage in the canopy moved upward with stand age, accompanied by an increase in canopy depth and leaf mass. The shape of the vertical distribution was almost symmetrical between the upper and lower halves in the closed stands, although slightly skewed downward. The logarithm of average spatial density decreased linearly as cumulative leaf mass increased with distance from the top of the canopy. The total cross-sectional area of the crowns exceeded the stand area from the middle of the canopy downward in the closed stands because of crown overlap. However, partly because of changes in crown morphology and structure, the increase in leaf mass with stand age did not always cause more severe crown competition.  相似文献   

14.
We estimated the aboveground net primary production (ANPP) in five self-thinning jack pine (Pinus banksiana) stands in Wood Buffalo National Park, NWT, Canada. The stands (11 to ca.175 years old) were selected to examine the relationship between stand density and tree size and its effect on carbon dynamics. Aboveground litterfall was collected from each stand from 1997 to 2012. Stand biomass was estimated by measuring tree size every 5 years and estimating the individual mass using allometric relationships. ANPP was then estimated by summing the litterfall mass, dead stem mass increment and stand biomass increment. We determined the proportional contribution of each organ to the total litter and the seasonal pattern of needle litterfall. There was a lower turnover rate of aboveground biomass in older stands than younger stands. The ANPP increased in the youngest stand (<30 years old) showed a decreasing trend in stands >50 years old. The maximum ANPP was estimated to be ca. 500?g m?2 year?1 in dry matter, which was found in 30–50 year-old stands.  相似文献   

15.
The effects of pre-commercial thinning on tree and branch characteristicswere analysed at two experimental sites in northern Sweden,where pre-thinning of Scots pine stands to 600, 1000 and 1800stems per hectares at heights of 1.5, 3, 5 and 7 m had beencombined in a factorial design. A total of 90 trees were cutand branches were measured in whorls sampled at 1-m intervals,starting with the whorl closest to 0.5 m above ground. Effectsof the treatments on tree and branch characteristics were analysedby a fixed-effect analysis of variance model, which was appliedseparately for each experimental site and whorl height. Diameterat breast height (d.b.h.) and living crown to height ratio decreased,while the height/d.b.h. ratio (stem form) increased with increasingstand density, and generally with increased height at thinning.No treatment effect was found on the number of branches perwhorl or branch angle, but branch diameter (BD) was significantlyinfluenced by both stand density after thinning and height atthinning. BD decreased with increases in stand density and decreasedwith increases in height at pre-commercial thinning. Relativebranch size (RBS), defined as the ratio between the sum of thediameters of branches in a whorl and stem perimeter under barkat the location of that whorl, was significantly influencedonly by stand height at the time of treatment. RBS decreasedby 4–6 per cent in whorls located below the current baseof the living crown with each step increase in stand heightat pre-commercial thinning. The results indicate that the numberof stems after pre-commercial thinning has a greater impacton tree size and shape than timing of pre-commercial thinning.Stand density after thinning also has a greater impact on branchsize, in the sense that it will affect branch size further upthe tree than the timing of pre-commercial thinning. However,by delaying the time for pre-commercial thinning it is possibleto reduce the RBS in the lower part of the stem. This mightbe an important measure to improve timber quality later in therotation period, which cannot be done solely by regulating standdensity.  相似文献   

16.
根据标准地和解析木调查资料,以樟子松人工林树冠内活枝为研究对象,探讨同一树木的不同龄阶的枝生长规律,同一林分不同大小树木枝生长的规律,以及不同林分条件下枝生长的规律。结果表明:单株树木枝条长度总生长曲线呈"S"形,连年生长在生长初期达到一最大值后随年龄的增加而逐渐减小;在同一林分中,枝条总生长随着枝龄的增加而持续增长;在不同年龄相同密度林分中,年龄较小的林分枝长连年生长要比年龄较大的树林增长快一些;在相同年龄不同密度林分中,密度较小的林分比密度较大的林分枝长总生长及同期连年生长要快一些。  相似文献   

17.
麻竹枝叶生长对钩梢的响应   总被引：1，自引：0，他引：1       下载免费PDF全文
为了解冠层生物量积累、分配及枝叶大小对麻竹立竹受营林措施干扰(钩梢)后的响应,对不同竹龄全梢、钩梢麻竹地上构件生物量、生物量比、单叶特征、大小枝生物量分配比例及商品竹叶数量进行了调查.结果表明:麻竹立竹地上现存生物量分配格局为秆＞枝＞叶.叶生物量、叶/枝和叶/秆生物量比为2年生＞3年生＞1年生.随着竹龄的增加,枝、秆生物量、地上生物量和枝/秆生物量比总体上呈增加的趋势.2年生和3年生立竹枝、叶生物量分配比例显著高于1年生立竹,秆生物量分配比例显著小于1年生立竹.此外,随着竹龄的增加,立竹减少了对0 ～8 mm枝生物量的分配,增加了对8～16 mm、16 mm以上枝生物量的投入,以提高空间拓展能力,截获更多光资源.钩梢强烈影响了生物量分配格局,显著减小了麻竹立竹枝、叶、秆、地上生物量.钩梢后麻竹立竹增加了枝、叶生物量分配比例,减少了秆生物量的分配比例,同时提高了单叶叶面积和单叶干质量,增加了8～16 mm、16 mm以上枝生物量分配比例,减小0～8 mm枝生物量分配比例,以权衡枝叶的生长,提高立竹对环境的适合度.钩梢后立竹叶/枝、叶/秆、枝/秆生物量比升高,表明生物量分配更多地向叶和枝倾斜.钩梢麻竹商品竹叶数量较全梢麻竹增加29.68％,且发生部位明显降低,钩梢后冠层下部商品竹叶数量增加79.73％,中部商品竹叶数量增加25.81％,降低了采摘高度.在钩梢后的一个生长季内,钩梢影响了麻竹立竹资源利用策略,表现为枝与叶之间关系的变化,但随钩梢年限的增加其变化规律如何尚需进一步研究.  相似文献   

18.
This study examined the impact of pre-commercial thinning (PCT) on tree growth, product recovery, stand value and financial return in jack pine stands in Northwestern Ontario. Ten sites composed of both control and PCT stands representing various stand densities (2000–6000 trees/ha) and stand ages (26–36 years old) were selected for this study. Three thousand and eighty-two trees were measured for DBH and total height, and were reconstructed in 3-D using a taper equation for jack pine. The reconstructed virtual trees were then “sawn” using the software package Optitek to obtain optimal lumber value recovery, which was then used to determine total product value per tree and financial return. The quadratic mean DBHs of trees from the PCT stands were significantly larger than those from the control stands for all 10 sites. Six of ten PCT stands had significantly taller trees than did the controls of the same sites. With increasing stand density, tree DBH decreased in the control stands while no consistent pattern could be recognized for the DBH of the PCT stands. The increment in average DBH due to PCT increased with increasing thinning intensity. PCT reduced total tree volume per hectare, benefited merchantable stem volume per hectare, and improved the total lumber volume and value recovery per hectare. On average, the PCT stands produced approximately $2760 and $1770/ha (or 19.6 and 16.1%) more product value per hectare for the dimension mill and stud mill, respectively. PCT also significantly reduced logging and lumber conversion costs. Higher total product values and lower total costs resulted in higher benefit/cost (B/C) ratios in the PCT stands than did in the control stands. The increased financial return due to PCT is associated with the magnitude of difference in quadratic mean DBH resulting from PCT. The B/C ratio difference between control and PCT stands increased with increasing thinning intensity. Overall, this study indicates that PCT appears to be an economically viable silvicultural investment for jack pine stands in Northwestern Ontario.  相似文献   

19.
Long-term declines in rainfall in south-western Australia have resulted in increased interest in the hydraulic characteristics of jarrah (Eucalyptus marginata Donn ex Smith) forest established in the region's drinking water catchments on rehabilitated bauxite mining sites. We hypothesized that in jarrah forest established on rehabilitated mine sites: (1) leaf area index (L) is independent of initial tree spacing; and (2) more densely planted trees have less leaf area for the same leaf mass, or the same sapwood area, and have denser sapwood. Initial stand densities ranged from about 600 to 9000 stems ha(-1), and trees were 18 years old at the time of sampling. Leaf area index was unaffected by initial stand density, except in the most sparsely stocked stands where L was 1.2 compared with 2.0-2.5 in stands at other spacings. The ratio of leaf area to sapwood area (A(l):A(s)) was unaffected by tree spacing or tree size and was 0.2 at 1.3 m height and 0.25 at the crown base. There were small increases in sapwood density and decreases in leaf specific area with increased spacing. Tree diameter or basal area was a better predictor of leaf area than sapwood area. At the stand scale, basal area was a good predictor of L (r(2) = 0.98, n = 15) except in the densest stands. We conclude that the hydraulic attributes of this forest type are largely independent of initial tree spacing, thus simplifying parameterization of stand and catchment water balance models.  相似文献   

20.
太行山刺槐花量与蜜源林经营   总被引：1，自引：0，他引：1  
通过对大量标准地的调查研究表明，单株开花量主要受自身遗传因素的控制，单株在量为0－5．2kg／株，同一单株各年度的开花量也有较大变化。林分花量与林龄、林分平均胸径、林分平均高、林分优势木平均高、每公顷胸高断面积、每公顷蓄积、林分总生物量、林分干量、林分枝量、林分叶量、林分根量等林分因子均具有极显著的相关关系，通过逐步回归分析，筛选出影响林分花量的主要林分因子，并建立了林分花量的多元回归估测模型。林分花量生长动态符合生物增长的Logistic运动规律，其速生点为8a，速生期为4-12a，林分生长后期的花量动态与干、枝、叶、根等其它器官的生长动态存在显著差异，上述结论对蜜源林的经营具有重要意义。  相似文献   

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