Spatial variation in sapwood area to leaf area ratio and specific leaf area within a crown of silver birch

Spatial variation in sapwood area to leaf area ratio (Huber value, HV) and specific leaf area (SLA) was examined in branches of closed-canopy trees of silver birch (Betula pendula Roth). HV increased basipetally within a crown and decreased with increasing branch order, but exhibited no significant radial trend along a primary branch. HV was primarily determined by branch position in a crown and branch diameter at the sampling point, being independent of the size of the tree and branch. Greater HV in the lower-crown branches is considered a means to mitigate differences in hydraulic transport capacity between the branches located in different canopy layers. Beside branch position and sampling location on a branch, SLA depended significantly on several other variables characterising tree and branch size. SLA increased basipetally within a crown and along a primary branch, but exhibited no significant trend with branch orders. Because height caused leaf area (A_L) to diminish more rapidly than leaf dry weight, A_L primarily determined the vertical variation in SLA.     

Changes in Siberian Fir Crown Architecture under Impaired Homeostasis

The crown of the Siberian fir (Abies sibirica) is characterized by a specific organization, namely, a narrow-pyramidal form, apical dominance, tiering by types of sexualization, and whorled branching. The gravitational vector is clearly manifested at all levels of the organization of the crown, that is, in the architecture (diageotropism of branches), morphostructure (dorsoventrality of tissues and organs of shoots, as well as the location of reproductive organs in the tree crown and on the shoot), and physiological processes. It was shown that the internal state of the tree is a determining factor in graviperception. When Siberian fir trees weaken, the diageotropism of branches is lost, which can serve as a universal biomarker of impairment of homeostasis.

     

Annual and spatial variation in shoot demography associated with masting in Betula grossa: comparison between mature trees and saplings

Backgrounds and Aims

Shoot demography affects the growth of the tree crown and the number of leaves on a tree. Masting may cause inter-annual and spatial variation in shoot demography of mature trees, which may in turn affect the resource budget of the tree. The aim of this study was to evaluate the effect of masting on the temporal and spatial variations in shoot demography of mature Betula grossa.

Methods

The shoot demography was analysed in the upper and lower parts of the tree crown in mature trees and saplings over 7 years. Mature trees and saplings were compared to differentiate the effect of masting from the effect of exogenous environment on shoot demography. The fate of different shoot types (reproductive, vegetative, short, long), shoot length and leaf area were investigated by monitoring and by retrospective survey using morphological markers on branches. The effects of year and branch position on demographic parameters were evaluated.

Key Results

Shoot increase rate, production of long shoots, bud mortality, length of long shoots and leaf area of a branch fluctuated periodically from year to year in mature trees over 7 years, in which two masting events occurred. Branches within a crown showed synchronized annual variation, and the extent of fluctuation was larger in the upper branches than the lower branches. Vegetative shoots varied in their bud differentiation each year and contributed to the dynamic shoot demography as much as did reproductive shoots, suggesting physiological integration in shoot demography through hormonal regulation and resource allocation.

Conclusions

Masting caused periodic annual variation in shoot demography of the mature trees and the effect was spatially variable within a tree crown. Since masting is a common phenomenon among tree species, annual variation in shoot demography and leaf area should be incorporated into resource allocation models of mature masting trees.     

Development of biomass proportions in Norway spruce (Picea abies [L.] Karst.)

This study tests the hypotheses that (1) the above-ground structure of Norway spruce (Picea abies [L] Karst.) is derivable from the functional balance theory, and that (2) crown ratio is a key source of structural variation in trees of different age and social position. Twenty-nine trees were measured in three stands (young, middle-aged, and mature), with three thinning treatments (unthinned, normal, and intensive) in the two older stands. There was a strong linear relationship between the total cross-sectional area of branches and that of stem at crown base. Foliage mass was linearly related with stem basal area at crown base. Also an allometric relationship was found between foliage mass and crown length. The mean length (weighted by basal area) of branches obeyed an exponential function of crown length. The parameters of most of these relationships were independent of slenderness (tree height/breast height diameter) and tree age However, total branch cross-sectional area per stem cross-sectional area in the young trees was greater than in the older trees. The young trees also had slightly shorter branches than predicted by the mean branch length equation. This was probably caused by branch senescence which had not yet started in the young stand. The older trees had a relatively long lower crown segment which was growing slowly and senescing. It was proposed that a segmented crown structure is characteristic of shade tolerant tree species, and that the structural model could be further developed by making the two segments explicit.     

Arsenate phytoextraction abilities of one-year-old tree species and its effects on the nutritional element content in plant organs

Abstract

The aim of the study was to evaluate the As phytoextraction potential of four tree species: Acer pseudoplatanus L., Betula pendula Roth., Quercus robur L., and Ulmus laevis Pall. in light of their prospective use in the phytoremediation of arsenate [As(V)] contaminated soils. The content of nutritional elements: B, Ca, K, Mg, Na, Si, P, and S was also analyzed. The trees were grown for 1?month in hydroponic cultures (Knop medium) supplemented with As(V), (1?mM). The results showed that the highest As accumulation efficiency was characterized by B. pendula (BCF = 0.87) and Q. robur (BCF = 0.5). Betula pendula accumulated about 80% of As in its roots (TF = 0.22) whereas Q. robur accumulated more than 60% of As in its shoots (TF = 1.60). The other tree species accumulated significantly lower amounts of As, more than 60% of which collected in their shoots. As(V) phytoextraction led to a significantly lower level of P and S in the roots of all tested tree species. Betula pendula seems promising for phytostabilisation and Q. robur for phytoextraction of As(V) from contaminated soils. The obtained results confirm the accumulation and translocation of As(V), as well as the acquisition of nutritional elements by the selected tree species.     

Short shoots of Betula pendula Roth. as bioindicators of urban environmental pollution in Wrocław (Poland)

Concentrations of the elements Ca, Cd, Co, Cr, Cu, Fe, K, Mg, Mn, N, Ni, P, Pb and Zn were measured in leaves of Betula pendula from the polluted areas of Wrocław, Poland and from a control site, relatively free from pollution. From the same sampled trees, lengths of vegetative short shoots were measured to investigate the influence of environmental pollution. Length of the vegetative short shoots of B. pendula was positively influenced by the traffic intensity and by the concentration of Co, Cu, Fe, Ni and Pb in leaves of this species. Vegetative short shoots of B. pendula from polluted sites in Wrocław were significantly longer than that of the trees growing in a clean area. Thus, this feature may be used as a pollution bioindicator.     

Structural crown properties of Norway spruce (Picea abies [L.] Karst.) and European beech (Fagus sylvatica [L.]) in mixed versus pure stands revealed by terrestrial laser scanning

How tree morphology develops in mixed-species stands is essential for understanding and modelling mixed-stand dynamics. However, research so far focused on the morphological variation between tree species and neglected the variation within a species depending on intra- and interspecific competition. Our study, in contrast, addresses crown properties of nine mature Norway spruces (Picea abies [L.] Karst.) of a pure stand and compares them with ten spruces growing in mixture with European beech (Fagus sylvatica [L.]). The same was done with 11 pure stand beeches and 12 beeches growing in mixture with spruce. Through application of a terrestrial laser scanner and a new skeletonization approach, we deal with both species’-specific morphological traits such as branch angle, branch length, branch bending, crown volume and space occupation of branches within the crown, some of which were hardly accessible so far. Special attention is paid to distinct differences between trees growing in mixed and pure stands: for spruce, our study reveals significantly longer branches and greater crown volumes in the mixed stand when compared to the pure stand. In case of European beech, individuals growing in mixture show flatter branch angles, more distinct ramification, greater crown volumes and a lower share of a single branch’s space occupation in the total crown volume. The results show that the presented methods yield detailed information on the morphological traits analyzed in this study and that interspecific competition on its own may have a significant impact on crown structures. Implications for production ecology and stand dynamics of mixed-species forests are discussed.     

Within-tree and among-tree variation in growth of Epirrita autumnata on mountain birch leaves

Abstract.

• 1 We studied among-tree and within-tree variation in the growth of larvae of a geometrid, Epirrita autumnata, on mountain birch (Betula pubescens ssp. tortuosa) leaves at different hierarchical levels: among trees (genets), among ramets within trees, among branches within ramets, among shoots within branches and among leaves within shoots. We used only short shoot leaves, which burst simultaneously in spring.
• 2 Trees accounted for most of the variation in larval growth rate, but there was substantial variation also among ramets within trees, among branches within ramets, and among short shoots within branches. Variation among leaves within short shoots was negligible. When the probabilities from different experiments were combined, the differences were statistically significant at the tree, ramet and branch levels, and approached significance at the shoot level.
• 3 In different experiments, larval growth was from 9% to 54% lower on the worst tree than on the best tree of the experiment. On average, larval growth rate was in different experiments from 11% to 32% lower on the worst ramet than on the best ramet within tree, from 8% to 18% lower on the worst than on the best branch within ramet, and from 12% to 30% lower on the worst than on the best shoot within branch.
• 4 The amount of among-and within-tree variation shown by our results may have ecological and evolutionary implications: among-tree variation should select for discrimination by ovipositing females and dispersing larvae, within-tree variation should select also for optimal foraging behaviour of larvae.

     

Primary ecological succession in vascular epiphytes: The species accumulation model

Epiphytes are integral to tropical forests yet little is understood about how succession proceeds in these communities. As trees increase in size they create microhabitats for late‐colonizing species in both small and large branches while maintaining small tree microhabitats for early colonizing species in the small and young branches. Thus, epiphyte succession may follow different models depending on the scale: at the scale of the entire tree, epiphytes may follow a species accumulation model where species are continuously added to the tree as trees increase in size but at the scale of one zone on a branch (e.g., inner crown: 0–2 m from the trunk), they may follow the replacement model of succession seen in terrestrial ecosystems. Assuming tree size as an indicator of tree age, I surveyed 61 Virola koschnyi trees of varying size (2.5–103.3 cm diameter at breast height) in lowland wet tropical forest in Costa Rica to examine how epiphyte communities change through succession. Epiphyte communities in small trees were nested subsets of those in large trees and epiphyte communities became more similar to the largest trees as trees increased in size. Furthermore, epiphyte species in small trees were replaced by mid‐ and late‐successional species in the oldest parts of the tree crown but dispersed toward the younger branches as trees increased in size. Thus, epiphyte succession followed a replacement model in particular zones within treecrowns but a species accumulation model at the scale of the entire tree crown.     

Nurse Trees as a Forest Restoration Tool for Mixed Plantations: Effects on Competing Vegetation and Performance in Target Tree Species

Multi‐species mixed plantations can be designed to meet social, economic, and environmental objectives during forest restoration. This paper reports results from an experiment in southern Sweden concerning the influence of three different fast growing nurse tree species on the cover of herbaceous vegetation and on the performance of several target tree species. After 10 years, the nurse trees had reduced the competing herbaceous vegetation but the effect was weak and it may take more than a decade to achieve effective vegetation control. The nurse tree species Betula pendula and Larix x eurolepis did improve stem form in some target tree species, but had a minor effect on survival and growth. The open conditions before crown closure of nurse trees strongly influence seedling performance and so delayed planting of target tree species may provide a means to avoid those conditions. Survival and growth differed greatly among the tree species. Besides the two nurse tree species mentioned above, high survival was found in Picea abies and Quercus robur and intermediate survival in Fagus sylvatica, Tilia cordata, and in the N‐fixing nurse tree Alnus glutinosa. Survival was low in the target tree species Fraxinus excelsior L. and Prunus avium. For restoration practitioners, our results illustrate the potential of using nurse trees for rapidly building a new forest structure and simultaneously increase productivity, which might be a cost‐effective strategy for forest restoration.     

Distribution of vessel size,vessel density and xylem conducting efficiency within a crown of silver birch (<Emphasis Type="Italic">Betula pendula</Emphasis>)

Spatial patterns in vessel diameter, vessel density and xylem conducting efficiency within a crown were examined in closed-canopy trees of silver birch (Betula pendula). The variation in anatomical and hydraulic characteristics of branches was considered from three perspectives: vertically within a crown (lower, middle and upper crown), radially along main branches (proximal, middle and distal part), and with respect to branch orders (first-, second- and third-order branches). Hydraulically weighted mean diameter of vessels (D _h) and theoretical specific conductivity of the xylem (k _t) exhibited no vertical trend within the tree crown, whereas leaf-specific conductivity of the xylem (LSC_t) decreased acropetally. Variation in LSC_t was governed by sapwood area to leaf area ratio (Huber value) rather than by changes in xylem anatomy. The acropetal increase in soil-to-leaf conductance (G _T) within the birch canopy is attributable to longer path length within the lower-crown branches and higher hydraulic resistance of the shade leaves. D _h, k _t and LSC_t decreased, while vessel density (VD) and relative area of vessel lumina (VA) increased distally along main branches. A strong negative relationship between vessel diameter and VD implies a trade-off between hydraulic efficiency and mechanical stability of xylem. D _h and VD combined explained 85.4% of the total variation of k _t in the regression model applied to the whole data set. Xylem in fast-growing branches (primary branches) had greater area of vessel lumina per unit cross-sectional area of sapwood, resulting in a positive relationship between branch radial growth rate and k _t. D _h, k _t and LSC_t decreased, whereas VD increased with increasing branch order. This pattern promotes the hydraulic dominance of primary branches over the secondary branches and their dominance over tertiary branches. In this way crown architecture contributes to preferential water flow along the main axes, potentially providing better water supply for the branch apical bud and foliage located in the outer, better-insolated part of the crown.     

Crown Spread Patterns for Five Deciduous Broad-leaved Woody Species: Ecological Significance of the Retention Patterns of Larger Branches

Patterns of crown spread and branch retention of two shade-intolerantspecies (Betula platyphyllaandB. maximowicziana) were comparedwith three more tolerant species (Quercus mongolica,Acer sieboldianumandMagnoliaobovata). Branching height (height of the lowest living branch)rose more rapidly with age for the twoBetulaspecies than forthe shade tolerant species. Branching heights ofA. sieboldianumandM.obovatawere similar, irrespective of tree height and age, andlarger trees tended to produce wider crowns than theBetulaspecieswhen trees of similar height were compared. In all species,the branch basal area (cross-sectional area of a branch at itsbase) and the leaf area per branch generally increased as thebranch position on a stem became lower. Therefore, retaininglarger branches contributed significantly to the support ofa larger leaf area per tree. The number of larger branches (branchbasal area >80 cm²) for bothBetulaspecies was significantlysmaller than that of the shade tolerant species. The branchretention pattern ofBetulaspecies was probably a consequenceof intolerance of the leaves to shade. The decline ofBetulaspecieswith forest succession is likely to occur through their inabilityto retain branches with a large base area in closed forests.Copyright1997 Annals of Botany Company Shade tolerance; crown spread; branch retention; branch size; broad-leaved woody species; leaf area index per tree     

Crown hollowing as a consequence of early shedding of leaves and shoots

Leafing pattern has long been considered as an important element characterizing the growth strategy of tree species; however, the consequences of leafing pattern for tree-crown formation have not been fully understood. To address this issue, the dynamic events (growth, birth, and death) of current-year shoots and leaves were investigated together with their location in saplings of a pioneer tree, Alnus sieboldiana. The leafing pattern was characterized by successive emergence and shedding of short-lived leaves. The combination of successive leafing and within-crown variation in leaf production brought about characteristic outcomes in crown morphology. In the outer crown, because of continuous leaf production, the shoots achieved great extension and enormous daughter shoot production, resulting in rapid expansion of the crown. In contrast, in the inner crown, due to early termination of leaf production, the shoots completely lost their leaves early in the growing season and consequently themselves died and were shed within the season. Such quick shedding of shoots caused “crown hollowing”, i.e., the interior crown consisted of primary branches with little secondary development or foliage. These dynamic features are an effective adaptive strategy in early succession but also may be a disadvantage to maintaining foliage for longer period. Crown maintenance associated with the longevity of structural components is thought to play an important role in survival strategy of tree species.     

Frequent fires alter tree architecture and impair reproduction of a common fire‐tolerant savanna tree

• Several Cerrado tree species have traits and structures that protect from fires. The effectiveness of a trait depends on the fire regime, especially the frequency. We used Vochysia elliptica, a common Cerrado tree, as a model to test whether different fire frequencies alter crown architecture and flower, fruit and seed production.
• We analysed the effect of fire on the production of inflorescences, fruits and seeds, as well as seed germination and tree architecture of 20 trees in each of three plots of a long‐term ecological experiment managed with different fire regimes: burned every 2 years (B), burned every 4 years (Q) in mid‐dry season and an area protected from fire (C).
• We found a large negative effect of fire frequency on crown architecture and on flower and fruit production. Trees in C and Q had significantly more main branches and a larger crown area than trees in B. At its peak, a tree in C was expected to produce 2.4 times more inflorescences than Q, and 15.5 times more than B, with similar magnitudes for fruits. Sixty per cent of trees in B and 10% in Q produced no fruits.
• The differences in architecture might explain the reduction in sexual reproduction due to a smaller physical space to produce flowers at the branch apices. Resource limitation due to plant investment to replace burned vegetative parts may also decrease sexual reproduction. Our results indicate potentially severe consequences of high fire frequencies for population dynamics and species persistence in Cerrado communities.

     

L-system-based model of growth of dark coniferous tree species

On the basis of L-systems a mathematical model was designed to describe the growth of a dark coniferous tree. The software models a virtual timber stand composed of single trees and its further development. To eliminate branch crossing of growing trees, the rule forbidding shoot growth into the space already occupied was applied to the model. The model parameters were defined for two dark coniferous species of the southern Sikhote-Alin’ — Jezo spruce (Picea jezoensis) and Khingam fir (Abies nephrolepis). The model describes various modifications of tree crown under the influence of neighbouring trees, height uncertainty of crown starting point, variation of taper and shape of a trunk depending on plantation density, and recovery of normal tree growth after singling. Comparison of the modelled results and empirical observations show that the model succeeds in describing the growth both of single trees and of mixed plantations.     

两种亚热带榕属乔木植冠损伤后的位置依赖性枝发生

三峡库区需要大量植株用于三峡工程所涉及的诸多建设(如铁路、公路、建筑)之后的植被恢复和绿化.由于具有优美树冠和耐瘠薄土壤的能力,榕(Ficus microcarpa L.)和黄桷树(Fvirens Ait.var.sublanceolata(Miq.)Cornor) 在三峡库区作为绿化和行道树木大量栽植.在三峡库区,这两种树种苗木的培育主要通过切枝扦插的方式进行.大量切枝损伤植株植冠并且使叶组织数量减少,对植株生长有很大影响.植株生长与植株的枝发生格局有很大关系,为明确植冠损伤对植株生长的可能影响,对榕和黄桷树植冠损伤后的枝发生进行了研究.实验发现,切枝造成的植冠损伤对榕和黄桷树植株侧枝上的枝发生没有影响,不同损伤强度之间和不同损伤发生时间之间都不存在明显的差异.但是,植冠损伤后,榕和黄桷树植株主茎上的枝发生是位置依赖性的.植冠损伤不影响榕和黄桷树植株损伤处理后新生主茎段和具侧枝主茎段上的枝发生,却促进了损伤处理后裸露主茎段上的枝发生,并且裸露主茎段上枝发生的数量和密度随植冠损伤强度的升高而增大.此外,实验结果表明,秋季植冠损伤植株裸露主茎段上的枝发生要高于春季植冠损伤植株裸露主茎段上的枝发生;在榕和黄桷树的枝发生中,仅有裸露主茎段上增强的枝发生会促进植冠损伤植株对叶组织的生物量投资并有利于受损植株的恢复和生长.     

A study of a population of birches in Glen Gairn

Summary

A small population of birches was studied with a view to measuring the rangeof morphological variation in Betula pendula Roth, and B. pubescens Ehrh. The general morphological features of crown and bark of trees in the area indicated that both species were present. A more detailed study was made of leaf and fruit characters, accepted by other investigators as being useful in discriminating between the species. It was shown that such characters varied continuously throughout the population and no tree was wholly pubescens- like or pendula-like in all characters.

The implications of these results are discussed in relation to the situation in Glen Gairn and to the general taxonomic situation of the British birches.     

Relationships between tree size, crown shape, gender segregation and sex allocation in Pinus halepensis, a Mediterranean pine tree

Background and Aims

Sex allocation has been studied mainly in small herbaceous plants but much less in monoecious wind-pollinated trees. The aim of this study was to explore changes in gender segregation and sex allocation by Pinus halepensis, a Mediterranean lowland pine tree, within tree crowns and between trees differing in their size or crown shape.

Methods

The production of new male and female cones and sex allocation of biomass, nitrogen and phosphorus were studied. The relationship between branch location, its reproductive status and proxies of branch vigour was also studied.

Key Results

Small trees produced only female cones, but, as trees grew, they produced both male and female cones. Female cones were produced mainly in the upper part of the crown, and male cones in its middle and lower parts. Lateral branch density was correlated with the number of male but not female cones; lateral branches were more dense in large than in small trees and even denser in hemispherical trees. Apical branches grew faster, were thicker and their phosphorus concentration was higher than in lateral shoots. Nitrogen concentration was higher in cone-bearing apical branches than in apical vegetative branches and in lateral branches with or without cones. Allocation to male relative to female function increased with tree size as predicted by sex allocation theory.

Conclusions

The adaptive values of sex allocation and gender segregation patterns in P. halepensis, in relation to its unique life history, are demonstrated and discussed. Small trees produce only female cones that have a higher probability of being pollinated than the probability of male cones pollinating; the female-first strategy enhances population spread. Hemispherical old trees are loaded with serotinous cones that supply enough seeds for post-fire germination; thus, allocation to males is more beneficial than to females.     

Size of the leaf as a marker of birch productivity at a distance from the climatic optimum

Morphometric parameters of mature leaves (area, venation density, and shape coefficient) and trunks (size and biomass) of two edificatory birch species, Betula pendula Roth and B. pubescens Ehrh., were characterized. These species inhabit a 1600-km transect of the Urals, from forest-tundra to forest-steppe. In both species, the highest trunk biomass was observed in the subzone of south taiga. Trunk parameters and leaf sizes of B. pendula varied in a narrower range than in B. pubescens. As distinct from leaf shape, leaf size was correlated with the average multiyear climate characteristics but not with the weather during a given growth season. In B. pubescens, which range extends wide from its climatic optimum, leaf area was positively correlated with trunk biomass. In B. pendula, growing mainly within the area of its climatic optimum, such correlation was not observed. We concluded that such parameter as mature leaf size could be used for prediction of tree productivity growing outside of the zone of their climatic optimum.     

两种亚热带榕属乔木植冠损伤后的位置依赖性枝发生

三峡库区需要大量植株用于三峡工程所涉及的诸多建设(如铁路、公路、建筑)之后的植被恢复和绿化。由于具有优美树冠和耐瘠薄土壤的能力,榕(Ficus microcarpa L.)和黄桷树(F. virens Ait. var. sublanceolata (Miq.) Cornor)在三峡库区作为绿化和行道树木大量栽植。在三峡库区,这两种树种苗木的培育主要通过切枝扦插的方式进行。大量切枝损伤植株植冠并且使叶组织数量减少,对植株生长有很大影响。植株生长与植株的枝发生格局有很大关系,为明确植冠损伤对植株生长的可能影响,对榕和黄桷树植冠损伤后的枝发生进行了研究。实验发现,切枝造成的植冠损伤对榕和黄桷树植株侧枝上的枝发生没有影响,不同损伤强度之间和不同损伤发生时间之间都不存在明显的差异。但是,植冠损伤后,榕和黄桷树植株主茎上的枝发生是位置依赖性的。植冠损伤不影响榕和黄桷树植株损伤处理后新生主茎段和具侧枝主茎段上的枝发生,却促进了损伤处理后裸露主茎段上的枝发生,并且裸露主茎段上枝发生的数量和密度随植冠损伤强度的升高而增大。此外,实验结果表明, 秋季植冠损伤植株裸露主茎段上的枝发生要高于春季植冠损伤植株裸露主茎段上的枝发生; 在榕和黄桷树的枝发生中,仅有裸露主茎段上增强的枝发生会促进植冠损伤植株对叶组织的生物量投