Shoot growth patterns in saplings of Cleyera japonica in relation to light and architectural position

To gain further insight into crown development, the influences of shoot architectural position (branch order) and light environment on patterns of shoot growth of Cleyera japonica Thunberg (Theaceae) were investigated. Annual shoot length and light environment were positively correlated within same-order branches. Shoot length differed significantly among branch orders: shoot length was greater for the lower-order branches when light environments were comparable. Lower-order branches lengthened to a certain extent even if light availability was relatively low, whereas higher-order branches did not grow vigorously even when light availability was relatively high. Within same-order branches, branching was independent of the light environment of the shoot. Sylleptic shoot production differed significantly among branch orders, with most sylleptic shoots being produced on second-order branches. It is concluded that both light condition and architectural position of shoots must be considered when examining the mechanisms underlying crown development.     

长沙地区3种优良观赏竹发笋及幼竹高生长规律

为给长沙地区观赏竹的引种培育和科学经营管理提供参考,研究了湖南省森林植物园中黄秆乌哺鸡竹、花秆早竹和花毛竹这3种竹的出笋、退笋及幼竹高生长规律。结果表明:黄秆乌哺鸡竹发笋期在4月初,花秆早竹和花毛竹在3月中下旬,历期均为20~25 d,明显分为初期、盛期和末期3个阶段;同一竹种不同发笋时期的发笋数间存在显著性差异(P0.05),其中黄秆乌哺鸡竹、花秆早竹和花毛竹的平均每株母株发笋数分别为1.09、1.85和1.16株;造成3种观赏竹退笋的原因有很多,其中在初期萌发笋退笋原因主要是人为机械损伤,盛期萌发笋退笋原因为机械损伤和营养缺乏等,而末期萌发笋的退笋原因主要是营养供应不足;3种观赏竹3个不同时期萌发笋幼竹高生长过程均呈"S"型生长曲线,符合"慢-快-慢"生长规律,相应的Logistic方程均较好地拟合了各个时期萌发笋幼竹的平均高生长过程;在幼竹高生长历期和株高方面,3种观赏竹初期和盛期萌发笋均优于末期,留笋养竹时选择初期和盛期萌发笋为宜;3种观赏竹幼竹昼夜生长均呈现一定节律,且夜间增长量均高于白天增长量。     

Seasonal shoot and needle growth of loblolly pine responds to thinning, fertilization, and crown position

The impacts of thinning, fertilization and crown position on seasonal growth of current-year shoots and foliage were studied in a 13-year-old loblolly pine (Pinus taeda L.) plantation in the sixth post-treatment year (1994). Length of new flushes, and their needle length, leaf area, and oven-dry weight were measured in the upper and lower crown from March through November. Total shoot length was the cumulative length of all flushes on a given shoot and total leaf area per shoot was the sum of leaf areas of the flushes.

By the end of June, first-flush foliage reached 70% of the November needle length (14.3 cm) and 65% of the final leaf area (15.0 cm²). Cumulative shoot length of first- and second-flush shoots achieved 95% of the annual length (30.3 cm), whereas total leaf area per shoot was 55% of the final value (75.3 dm²). Fertilization consistently stimulated fascicle needle length, dry weight, and leaf area in the upper crown. Mean leaf area of upper-crown shoots was increased by 64% six years after fertilization. A significant thinning effect was found to decrease mean leaf area per shoot in the crown. For most of the growing season, the thinned-fertilized trees produced substantially more leaf area per shoot throughout the crown than the thinned-nonfertilized trees. These thinned-fertilized trees also had greater needle length and dry weight, longer first flush shoots, and more leaf area per flush than trees in the thinned-nonfertilized plots. Needle length and leaf area of first flush shoots between April and July were linearly related to previous-month canopy air temperature (T_a). Total shoot length strongly depended on vertical light gradient (PPFD) within the canopy, whereas shoot leaf area was a function of both PPFD and T_a. Thus, trees produced larger and heavier fascicles, more and longer flush shoots, and more leaf area per shoot in the upper crown than the lower crown. We conclude that thinning, fertilization, and crown position regulate annual leaf area production of current-year shoots largely by affecting the expansion of first flush shoots and their foliage during the first half of the growing season.     

Shoot development and dieback in progenies of Nothofagus obliqua

Shoot growth and dieback were compared among progenies of nursery-grown seedlings of Nothofagus obliqua belonging to seven progenies of the same provenance (Quila-Quina, Argentina). First-year shoots consisted of one growth unit (GU) and second-year shoots of one or two GUs. The probability of development of two GU was similar for all progenies. Progenies were different in terms of shoot size, terminal bud abscission, the extent of shoot dieback after shoot extension and the node of origin of the relay shoot on the first shoot. Plants with a second-year shoot consisting of two GUs had a thicker stem and more nodes than those with single-GU shoots. The selection of N. obliqua seed trees based on architectural traits suitable for forestry development at specific sites must contemplate variability among progenies and their probabilities of successful development under different conditions.     

The effect of canopy position on growth and mortality in mixed sapling communities during self-thinning

This research investigates how species in the sapling phase differ in growth and survival depending on light availability (as estimated by canopy position) by means of tree-ring analysis and modelling mortality. We harvested 120 live and 158 dead saplings in self-thinning communities consisting of Silver birch (Betula pendula Roth.), Scots pine (Pinus sylvestris L.), Japanese larch (Larix kaempferi Carr.) and Douglas fir (Pseudotsuga menziesii Mirb. Franco) in the Netherlands. Results are evaluated within the framework of a trade-off between high-light growth and low-growth survival. Radial growth, measured at ground level, generally declined over time. In addition, a decreasing light availability further reduced growth in all species except Douglas fir. Trees died when radial growth was reduced to about 0.5 mm year⁻¹. Mortality in all species except Scots pine was significantly related to recent growth, but mortality curves were not different. The light-demanding Silver birch and Japanese larch differed from the shade-tolerant Douglas fir in both high-light growth and low-growth mortality, in line with a growth-survival trade-off. The light-demanding Scots pine did not fit this pattern as it was unable to transfer high radial growth into height gain, leaving it in suppressed canopy positions. This indicates the importance of height growth in the growth-survival trade-off. Differences in mortality probabilities affect the potential for coexistence, however, in all species also fast-growing individuals died suggesting additional factors causing mortality during self-thinning, other than direct competition for light.     

Leaf traits in relation to crown development, light interception and growth of elite families of loblolly and slash pine

Crown architecture and size influence leaf area distribution within tree crowns and have large effects on the light environment in forest canopies. The use of selected genotypes in combination with silvicultural treatments that optimize site conditions in forest plantations provide both a challenge and an opportunity to study the biological and environmental determinants of forest growth. We investigated tree growth, crown development and leaf traits of two elite families of loblolly pine (Pinus taeda L.) and one family of slash pine (P. elliottii Mill.) at canopy closure. Two contrasting silvicultural treatments -- repeated fertilization and control of competing vegetation (MI treatment), and a single fertilization and control of competing vegetation treatment (C treatment) -- were applied at two experimental sites in the West Gulf Coastal Plain in Texas and Louisiana. At a common tree size (diameter at breast height), loblolly pine trees had longer and wider crowns, and at the plot-level, intercepted a greater fraction of photosynthetic photon flux than slash pine trees. Leaf-level, light-saturated assimilation rates (A(max)) and both mass- and area-based leaf nitrogen (N) decreased, and specific leaf area (SLA) increased with increasing canopy depth. Leaf-trait gradients were steeper in crowns of loblolly pine trees than of slash pine trees for SLA and leaf N, but not for A(max). There were no species differences in A(max), except in mass-based photosynthesis in upper crowns, but the effect of silvicultural treatment on A(max) differed between sites. Across all crown positions, A(max) was correlated with leaf N, but the relationship differed between sites and treatments. Observed patterns of variation in leaf properties within crowns reflected acclimation to developing light gradients in stands with closing canopies. Tree growth was not directly related to A(max), but there was a strong correlation between tree growth and plot-level light interception in both species. Growth efficiency was unaffected by silvicultural treatment. Thus, when coupled with leaf area and light interception at the crown and canopy levels, A(max) provides insight into family and silvicultural effects on tree growth.     

The effect of crown form and plagiotrophy on the growth of Picea abies f. pendula cuttings

Seven‐year old cuttings of pendula spruce were taller and had larger diameters than seedlings or cuttings of Norway spruce of normal crown type. Pendulous cuttings still had plagiotropic growth at age 7 years and the rate of change to orthotropic growth form was weaker than in cuttings with normal crown type. In pendulous cuttings the effect of the origin of ortet and clone on the crown symmetry was significant at age 5 years but not at age 7 years. The effect of clone on the growth form was evident at ages 5 and 7 years, but the effect of the origin of ortet was significant only in 7‐year‐old cuttings. There were no differences in plagiotrophy between clones from 4‐ and 7‐year‐old ortets. For pendulous cuttings the average height and diameter growth decreased in 5‐ and 6‐ year‐old cuttings with less pendulous crown form and with more plagiotropic growth form but this decrease had almost disappeared in 7‐year‐old cuttings.     

Thinning,fertilization, and crown position interact to control physiological responses of loblolly pine

To examine physiological responses to thinning, fertilization, and crown position, we measured net photosynthesis (P(n)), transpiration (E), vapor pressure difference (VPD), stomatal conductance (g(s)), and xylem pressure potential (Psi(1)) between 0930 and 1130 h under ambient conditions in the upper and lower crowns of a 13-year-old loblolly pine (Pinus taeda L.) plantation six years (1994) after the treatments were applied. Photosynthetic photon flux density (PPFD) and air temperature (T(a)) within the canopy were also recorded. Needle P(n) of thinned trees was significantly enhanced by 22-54% in the lower crown, because canopy PPFD increased by 28-52%. Lower crown foliage of thinned plots also had higher E and g(s) than foliage of unthinned plots, but thinning had no effect on needle Psi(1) and predawn xylem pressure potential (0430-0530 h; Psi(pd)). Tree water status did not limit P(n), E and g(s) during the late-morning measurements. Fertilization significantly decreased within-canopy PPFD and T(a). Needle Psi(1) was increased in fertilized stands, whereas P(n), E and g(s) were not significantly altered. Upper crown foliage had significantly greater PPFD, P(n), VPD, g(s), E, and more negative Psi(1) than lower crown foliage. In both crown positions, needle P(n) was closely related to g(s), PPFD and T(a) (R(2) = 0.77 for the upper crown and 0.82 for the lower crown). We conclude that (1) silvicultural manipulation causes microclimate changes within the crowns of large trees, and (2) needle physiology adjusts to the within-crown environmental conditions.     

Shoot structure and growth along a vertical profile within a Populus-Tilia canopy

We investigated shoot growth patterns and their relationship to the canopy radiation environment and the distribution of leaf photosynthetic production in a 27-m-tall stand of light-demanding Populus tremula L. and shade-tolerant Tilia cordata Mill. The species formed two distinct layers in the leaf canopy and showed different responses in branch architecture to the canopy light gradient. In P. tremula, shoot bifurcation decreased rapidly with decreasing light, and leaf display allowed capture of multidirectional light. In contrast, leaf display in T. cordata was limited to efficient interception of unidirectional light, and shoot growth and branching pattern facilitated relatively rapid expansion into potentially unoccupied space even in the low light of the lower canopy. At the canopy level, T. cordata had higher photosynthetic light-use efficiency than P. tremula, whereas P. tremula had higher nitrogen-use efficiency than T. cordata. However, at the individual leaf level, both species had similar efficiencies under comparable light conditions. Production of new leaf area in the canopy followed the pattern of photosynthetic production. However, the species differed substantially in extension growth and space-filling strategy. Light-demanding P. tremula expanded into new space with a few long shoots, with shoot length strongly dependent on photosynthetic photon flux density (PPFD). Production of new leaf area and extension growth were largely uncoupled in this species because short shoots, which do not contribute to extension growth, produced many new leaves. Thus, in P. tremula, the growth pattern was strongly directed toward the top of the canopy. In contrast, in shade-tolerant T. cordata, shoot growth was weakly related to PPFD and more was invested in long shoot growth on a leaf area basis compared with P. tremula. However, this extension growth was not directed and may serve as a passive means of avoiding self-shading. This study supports the hypothesis that, for a particular species, allocation patterns and crown architecture contribute as much to shade tolerance as leaf-level photosynthetic acclimation.     

速生丰产林的产业地位和建设--以福建省光泽县饶坪经营所为例

以福建省光泽县饶坪经营所为例，阐述建设速生丰产林的重要性，提出速生丰产林建设中应注意的几个问题，并总结了经营所在速丰林建设中取得的经验和教训，为速生丰产林建设提供参考。     

The effect of nitrogen supply on root growth and development in sycamore and Sitka spruce trees

Sycamore (Acer pseudoplatanus L.) and Sitka spruce (Picea sitchensis(Bong.) Carr.) were grown in sand culture in glasshouses withtwo levels of N supplied with irrigation 1.0 (deficient) and6.0 (sufficient) molNm^–3, all as NH₄NO₃. Providing trees with a sufficient N supply increased both theirabove ground growth and N content compared with the N deficientplants. Provision of the generous N supply also altered thedistribution of growth between leaves and roots, with the N-deficientplants having a higher root:leaf or root:needle ratio than thewell fertilized trees. Provision of a generous N supply stimulatedroot growth, especially at the later harvests, which was reflectedmainly in growth of the tap root in sycamore. There was an increasein both root mass and root diameter with N supply. When thegrowth of white roots was monitored using a borescope, it wasshown that there were significantly more new roots producedby the well-fertilized trees. The borescope data also showeddetail of the bimodal seasonal pattern of root growth underhigh N in Sitka spruce which related to trends in nitrogen uptake.     

Cloning by cuttings in Nordmann fir,Abies nordmanniana: hormonal characteristics in relation crown position,rooting competence,and orthotropism as ramets

New Forests - Conifer tree species belonging to Abies are notoriously difficult to propagate vegetatively due to aging of material, slow rooting, and persistent plagiotropism in rooted cuttings. We...     

Vegetative propagation of Dalbergia sissoo: effect of growth regulators, length, position of shoot and type of cuttings on rooting potential in stem cuttings

The effect of auxins (IAA or IBA at 100,200,500 mg L 1) on rooting and sprouting parameters differed significantly (p < 0.05).Rooting and sprouting percentages were higher in some treatments while other parameters were significantly higher in other treatments.The results of the present study revealed that rooting was significantly (p < 0.05) affected by the length of cuttings,as well as the position of shoots and type of cuttings.On average,86.0 per cent rooting was observed in the 30-cm long cuttings compared to the other two lengths of cuttings,i.e.,20 and 25 cm,irrespective of any auxin treatment.In a control set,without any auxin treatment,a maximum of 60.0% rooting was recorded in the 30-cm long cuttings and a minimum of 40.0% of the cuttings rooted in the 20-cm long cuttings.Similarly,cuttings collected from the lower and upper portions of shoots resulted in 72.5 and 52.5 per cent rooting respectively,irrespective of auxin treatments.Maximum rooting was observed in the lower portion (40.0%) of cutting compared to the upper portion (30.0%) in the control set without auxin treatment.Leafless branches produced maximum (72.0%) rooting compared to the leafy cuttings (35.0%),irrespective of the auxin treatment.The leafy cuttings produces a minimum of 15.0% sprouting and rooting in the control set.     

毛竹笋用林挖掘鞭笋对春笋的影响

自2001年开始开展毛竹笋用林生产鞭笋试验,结果表明:通过保持良好的立竹结构、增施肥料、清除老弱鞭等措施,挖掘鞭笋不会对春笋产量和出笋时间造成影响,影响出笋时间的主要因子是出笋前1个月平均气温和降雨量。合理挖掘鞭笋可使毛竹笋用林的经济效益显著提高。     

毛竹鞭笋与冬笋、春笋的内在特征分析

为开展鞭笋高产技术研究,提高竹林总产值,对毛竹鞭笋与冬笋、春笋的笋芽萌发数量、竹笋个体质量和竹笋生长方向等因子进行对比分析。结果表明:与冬笋和春笋相比,鞭笋笋芽萌发数量少、笋个体质量小,竹鞭平均直径比立竹平均胸径小4倍,且被挖出利用的鞭笋只占鞭笋总量的40.3%。分析表明,单位面积鞭笋产量低于冬笋和春笋的原因是由毛竹自身的内在特性所致。为提高鞭笋产量,应及时采挖鞭笋,促使岔鞭多发,并适时施肥,促进支鞭萌发生长。     

Influence of crown thinning on radial growth pattern of Pinus taeda in southern Brazil

New Forests - Loblolly pine is widely planted in southern Brazil. Despite its major relevance for the forestry sector, knowledge about its radial growth at different height levels is...     

Shoot biomass growth is related to the vertical leaf nitrogen gradient in Salix canopies

Plant canopy optimization models predict that leaf nitrogen (N) distribution in the canopy will parallel the vertical light gradient, and numerous studies with many species have confirmed this prediction. Further, it is predicted that for a given canopy leaf area, a low vertical light extinction coefficient will promote rapid growth. Therefore, the ideal canopy of fast-growing plants should combine high leaf area index with a low light extinction coefficient; the latter being reflected in a flat vertical leaf N gradient throughout the canopy. Based on data from an experimental Salix stand (six varieties) grown on agricultural land in central Sweden, we tested the hypothesis that shoot growth is correlated with vertical leaf N gradient in canopies of hybrid willows bred for biomass production, which could have implications for Salix breeding. Tree improvement research requires screening of growth-related traits in large numbers of plants, but assessment of canopy leaf N gradients by chemical analysis is expensive, time-consuming and destructive. An alternative to analytical methods is to estimate leaf N gradients nondestructively with an optical chlorophyll meter (SPAD method). Here we provide a specific calibration for interpreting SPAD data measured in hybrid willows grown in biomass plantations on fertile agricultural land. Based on SPAD measurements, a significant and inverse relationship (r(2) = 0.88) was found between shoot biomass growth and vertical leaf N gradient across canopies of six Salix varieties.     

Shoot development,chlorophyll, gas exchange and carbohydrates in lychee seedlings (Litchi chinensis)

Shoot growth, chlorophyll concentrations, gas exchange and starch concentrations were studied in lychee (Litchi chinensis Sonn.) seedlings of cultivar "Wai Chee" grown in a heated greenhouse at Nambour in subtropical Australia (27 degrees S). We also examined the effects of shoot defoliation and root pruning on leaf expansion. Shoot growth showed a rhythmic cycle under constant greenhouse conditions, with a mean duration of flushing of 20 days and an interval of 10 days over three cycles. Shoots and leaves expanded in a sigmoidal pattern to about 80 mm and 500 cm(2), respectively, for each flush. Starch concentrations of the lower stem and roots decreased as the young red leaves expanded, and increased as the fully expanded leaves turned dark green. Chlorophyll concentrations and net CO(2) assimilation rate were highest in the fully expanded dark green leaves. Removing 50% of the area of each fully expanded leaf had little effect on the expansion of younger leaves, but total biomass of defoliated plants was only 60% of that of controls. In contrast, removing half the roots just before bud swelling reduced final leaf area by 80%. We conclude that the young shoot has relatively low rates of photoassimilation until the leaves are fully expanded and dark green, and depends on assimilates from elsewhere in the plant. During leaf expansion, translocation of assimilates to the shoot occurred at the expense of the roots.     

Shoot growth responses to light microenvironment and correlative inhibition in tree seedlings under a forest canopy

To examine the mechanisms underlying crown development, I investigated the dependence of shoot behavior on light microenvironment in saplings of the evergreen broad-leaved tree species, Litsea acuminata (Bl.) Kurata, growing on a forest floor. The local light environment of individual shoots (shoot irradiance) and plants (plant irradiance, defined as the shoot irradiance of the most sunlit shoot of a plant) were analyzed as factors affecting shoot behavior. Daughter shoots that developed under partially sunlit conditions were longer and less leafy than daughter shoots developed under shaded conditions. Shoot production increased with increasing shoot irradiance. Terminal shoots receiving 5% or less of full sunlight produced 0.67 daughter shoots on average, whereas shoots receiving 10% or more of full sunlight produced 1.72 daughter shoots. In terminal shoots receiving 5% or less of full sunlight, the probability of producing no daughter shoots was about 63% when other shoots on the plant received 10% or more of full sunlight, but was < 35% where the rest of the plant was also shaded. Shoot death was observed only in shoots receiving 5% or less of full sunlight. The mortality of shaded shoots was higher in plants growing in high irradiance than in plants growing in low irradiance. The ecological significance of correlative inhibition (the enhanced mortality and reduced production of new shaded shoots in the presence of partially-sunlit shoots) is discussed.