Changes in spatial distribution during the life history of a tropical tree,Scaphium macropodum (Sterculiaceae) in borneo

We studied the spatial distribution of fruits and plants, mortality and growth rates ofScaphium macropodum (Sterculiaceae) in four 1-ha plots in a tropical rain forest in West Kalimantan, Indonesia. The species is a large deciduous tree and produces wind-dispersed fruits on defoliated twigs. The density of dispersed fruits on the ground decreased with increasing distance from a parent tree. The area under the parent's crown had the highest density of the fruits and the highest mortality of the seedlings immediately after germination. Consequently, the density of the established seedlings peaked 14 m from the tree which is outside its crown. Thick litter mainly from the parent tree seemed to physically prevent the seedlings' root from reaching the soil surface and caused the high mortality. Juvenile and mature trees distributed exclusively, suggesting that regeneration is the most successful outside of the crown of mature trees. Saplings under canopy shade did not grow well.Scaphium macropodum is hypothesized to require a gap for seedling growth and successful regeneration, whereas it can germinate and last under closed canopies as suppressed seedlings or saplings.     

Local and geographical distributions for a tropical tree genus,Scaphium (Sterculiaceae) in the Far East

Tropical rain forests have an amazingly large number of closely related, sympatric species. How the sympatric species coexist is central to understanding the maintenance of high biodiversity in tropical rain forests. We compared local and geographical distributions among trees in Scaphium (Sterculiaceae), a tropical canopy tree genus. Scaphium is endemic to the Far Eastern tropics and comprises six species. Scaphium scaphigerum is distributed in drier regions than the other species' geographical distribution ranges. Scaphium longiflorum is distributed swamp forests, whereas the others were distributed in lowland and hill tropical rain forests on undulating land. Scaphium borneense, S. longipetiolatum, and S. macropodum co-occurred in a 52-ha plot in Lambir, Sarawak and clearly showed an allopathic pattern of distribution related to elevation in it. In the plot, the elevational difference was correlated with soil variation. Consequently, the difference in edaphic condition promoted the habitat segregation of the species. Thus these five Scaphium species have divergent habitats at various spatial scales and coexist because they reduce direct competition by habitat niche differentiation. Although the non-equilibrium hypothesis for the coexistence of Scaphium species cannot be rejected categorically due to the lack of enough information about S. linearicarpum, the equilibrium force may play the predominant role which permits their coexistence.     

Habitat-related variation in tree leaf form in four tropical forest types on Pulau Ubin,Singapore

Abstract. Sun leaves from 37 species of tree and shrub were collected in four forest types on Pulau Ubin, Singapore. Evidence of habitat-related variation in the form of leaves is presented. The species were from the habitats: mangrove, beach forest, adinandra belukar (secondary forest on degraded soils) and secondary forest on undegraded soils. The mangrove forest species sampled had thicker leaves with a lower specific leaf area than the beach forest species. Leaves of species from the adinandra belukar were thicker and smaller, with more dry weight per unit area, than those of pioneers from undegraded sites. This is interpreted as oligotrophic xeromorphy in adinandra belukar.     

Scaling of Petiole Dimensions with Respect to Leaf Size for a Tropical Tree, Scaphium macropodum (Sterculiaceae), in Borneo

Scaphium macropodum (Miq.) Beumee ex Heyne (Sterculiaceae) in a tropical rain forest in West Kalimantan (Indonesia) was analyzed from the viewpoint of statics. The petiole diameter must increase with increasing leaf size to retain enough mechanical stability and a sufficient amount of conductive vessels. The petiole's cross-sectional area at its base was found to be proportional to the leaf blade's dry mass, which indicates that Shinozaki's pipe model is applicable to leaves with different sizes. Although larger leaves produce greater bending moments on the petiole's cross-section as a result of their greater weights, the bending stresses at the petiole's base caused by the leaf's weight were constant at ca. 76,900 g cm⁻² regardless of leaf size. Thicker petioles increase the leaf's mechanical stability, but require sizable energy investments for their construction. It is hypothesized that the constant value for petiolar stress indicates an optimal balance between energy economy and the mechanical stability of S. macropodum leaves. To keep bending stress constant, the leaf blade's center of gravity shifts to a more proximal position and the cross-sectional area of the petiole increases. Received 8 December 1997/ Accepted in revised form 1 December 1998     

Tree form in a mixed dipterocarp forest in Indonesian Borneo

The form of tropical trees was studied with reference to the production structure of the component individuals of a tropical rain forest stand in Sebulu, East Kalimantan in Indonesian Borneo, since the production structure as a physical or bio-economical basis of tree form still remains obscure in tropical rain forests. The pipe model theory successfully explained the crown shapes of different trees, and its parameter, designated as specific pipe length, suggested an increase in the cost of leaf mass growth with an increase in crown size. A mathematical model consisting of exponential functions of aboveground height was applied for describing stem form, and its properties were examined through changes in its coefficients and by adopting an assumption of the geometrical similarity of individual stem form as a criterion for comparing differences in stem form among individual trees. Furthermore, the cost of buttersses was discussed using the relation between bole- and buttress weight calculated from the mathematical model.     

Light,leaf age,and leaf nitrogen concentration in a tropical vine

Summary Tropical vines in the Araceae family commonly exhibit alternating periods of upward and downward growth, decoupling the usual relationship between decreasing light environment with increasing age among the leaves on a shoot. In this study I examined patterns of light, leaf specific mass, and leaf nitrogen concentration in relation to leaf position, a measure of developmental age, in field collected shoots of Syngonium podophyllum. These data were analyzed to test the hypothesis that nitrogen allocation parallels within-shoot gradients of light availability, regardless of the relationship between light and leaf age. I found that leaf nitrogen concentration, on a mass basis, was weakly correlated with leaf level light environment. However, leaf specific mass, and consequently nitrogen per unit leaf area, were positively correlated with gradients of light within the shoot, and either increased or decreased with leaf age, providing support for the hypothesis that nitrogen allocation parallels gradients of light availability.     

Comparison of the physiology, morphology, and leaf demography of tropical saplings with different crown shapes

Branch architecture, leaf photosynthetic traits, and leaf demography were investigated in saplings of two woody species, Homolanthus caloneurus and Macaranga rostulata, co-occurring in the understory of a tropical mountain forest. M. rostulata saplings have cylindrical crowns, whereas H. caloneurus saplings have flat crowns. Saplings of the two species were found not to differ in area-based photosynthetic traits and in average light conditions in the understory of the studied site, but they do differ in internode length, leaf emergence rate, leaf lifespan, and total leaf area. Displayed leaf area of H. caloneurus saplings, which have the more rapid leaf emergence, was smaller than that of M. rostulata saplings, which have a longer leaf lifespan and larger total leaf area, although M. rostulata saplings showed a higher degree of leaf overlap. Short leaf lifespan and consequent small total leaf area would be linked to leaf overlap avoidance in the densely packed flat H. caloneurus crown. In contrast, M. rostulata saplings maintained a large total leaf area by producing leaves with a long leaf lifespan. In these understory saplings with a different crown architecture, we observed two contrasting adaptation strategies to shade which are achieved by adjusting a suite of morphological and leaf demographic characters. Each understory species has a suite of morphological traits and leaf demography specific to its architecture, thus attaining leaf overlap avoidance or large total leaf area.     

Leaf water relations and anatomy of a tropical rainforest tree species vary with crown position

Summary Leaf water potentials, osmotic properties and structural characteristics were examined in the Australian tropical rainforest tree species, Castanospermum australe. These features were compared for individuals growing in the understorey and canopy of the undisturbed forest and in an open pasture from which the forest had been cleared. Leaf water potentials during the day declined to significantly lower values in the open-grown and canopy trees than in the understorey trees. During most of the day the opengrown tree experienced the lowest water potentials. These differences were paralleled by significant differences in tissue osmotic properties. The tissue osmotic potential at full hydration was lowest in the open-grown tree (-1.80 MPa), intermediate in the canopy trees (-1.38 MPa), and highest in the understorey trees (-0.80 MPa). As a result, the degree to which high and positive turgor pressures were maintained as water potentials declined was highest in the open-grown tree, intermediate in the canopy trees, and lowest in the understorey trees. The differences in tissue osmotic properties between individuals in the three crown positions were paralleled, in turn, by differences in leaf structual characteristics. Relative to leaves of the canopy and open-grown trees, leaves of the understorey trees had significantly larger epidermal cells with thinner cell walls, larger specific leaf areas and turgid weight: dry weight ratios, and a higher proportion of intercellular air space.Abbreviations ₁ Leaf tissue water potential - _min Lowest value of ₁ during the day ( noon) - _{P=0 1} zero turgor - R Relative water content - P Tissue turgor pressure - Tissue osmotic potential - ₀ at full hydration     

Aboveground biomass of tropical rain forest stands in Indonesian Borneo

Aboveground plant biomass was examined in a tall virgin tropical lowland evergreen rain forest dominated by Dipterocarpaceae in Sebulu, East Kalimantan, Indonesia, with special reference to the gap-, building- and mature phases of the forest growth cycle. From the records of dimensions of sample trees examined by the stratified clip technique and DBH inventory data of trees in a study plot, the biomass of larger trees (DBH 4.5 cm) was estimated by the allometric correlation method. The biomass of smaller plants (DBH < 4.5 cm) was estimated by harvesting the plants in small quadrat plots. Although large differences were found between aboveground-biomass-estimates in different patches of different growth stages, the aboveground biomass in a 1.0 ha plot was 509 t/ha, and the one-sided LAI was 7.3 ha/ha. These values seem to result from the tall forest architecture with huge emergent trees (over 70 m high) and a moderate packing of plant mass indicated by the basal area value of 38.8 m²/ha for trees with DBH 4.5 cm.This study was financed through a grant to H. Ogawa from the Overseas Scientific Research Funds of the Ministry of Education, Science, and Culture, Tokyo. Sponsorship from the Lembaga Ilumu Pengetahuan Indonesia (LIPI), Jakarta, the Lembaga Biologi National (LBN), Bogor, and the Herbarium Bogoriense, Bogor is gratefully acknowledged. We are also grateful to Drs Soetiyati, M. Rifai, K. Kartawinata, and the staffs of P. T. Kutai Timber Indonesia for their kind support, Dr K. Ogino for his advice and cooperation in field work, and Dr H. Kataoka for providing us with the geological map of Samarinda Province.     

Adaptive significance of vegetative sprouting for a tropical canopy tree, Scaphium longiflorum (Sterculiaceae), in a peat swamp forest in Central Kalimantan

Scaphium longiflorum Ridley (Sterculiaceae), a common canopy tree in peat swamp forests in the Far East, produces vegetative sprouting in its juvenile stage. We investigated morphological features and allometric properties of the species in a peat swamp forest in Central Kalimantan, Indonesia, to determine under what conditions ramets are produced and discuss the adaptive significance of the vegetative sprouting in a peat swamp environment. Larger juveniles were more toppled, and the toppled ones sprouted vegetatively. Therefore, the vegetative sprouting acts as a countermeasure for a shoots mechanical failure and fall on an unstable peat soil. We propose three hypotheses to explain the reason why larger juveniles are more often toppled in a peat swamp environment.     

Variation in seed and seedling traits in Pithecellobium pedicellare,a tropical rain forest tree

Summary Pithecellobium pedicellare, a mimosoid legume, is a large canopy tree in the tropical rain forests of Costa Rica. We examined the pattern of variation in seed weight, germination date, hypocotyl length (stem), and rachis length (the first leaf) of the seedlings in this species. Seeds collected from widely dispersed individual trees at the La Selva Biological Station, Costa Rica, were randomly planted in blocks, and grown under controlled, indoor conditions for about 2 weeks. There-fore, we were able to quantify the effects of maternal family on mean seed weight and the effects of maternal family and microenvironment on the remaining traits examined. A significant effect of maternal family was detected for all traits. In particular, the maternal effects on germination date and seedling size traits which were consistently significant even after controlling the initial seed weight may indicate that the maternal effects reflect, at least to some extent, maternal genetic control over these traits. Despite overall strong maternal effects, the performance of maternal siblings, such as the rachis length, differed among blocks. The sensitivity of maternal siblings to the local environments may contribute to the maintenance of genetic variability in this highly outcrossing tropical species.     

Species diversity, abundance, and vertical size structure of rattans in Borneo and Java

We studied rattan communities in four forest types in Borneo and Java to clarify the pattern of species diversity and vegetation structure. Within six plots of 4.82 ha in total, we found 42 rattan species in six genera with 4,736 stems (≥20 cm long). There was a significant positive correlation between rattans and trees in species diversity, decreasing in the order mixed dipterocarp (for rattans: Shannon–Wiener diversity index, H′ = 2.87–3.34) > alluvial (1.96) > lower montane (1.43) > peat swamp forests (1.34). This pattern coincided with the diversity of the regional flora. The density of rattan stems (ha^–1) decreased in the order lower montane (5,997) > mixed dipterocarp (598–992) > alluvial (592) > peat swamp forests (162). The maximum height of rattans would be determined by the canopy height, rather than by the maximum tree height. The rattan stem volume ranged from 0.25 to 1.88 m³ ha⁻¹ and was not correlated with the stem density. The cool montane climate seemed to decrease the maximum height of rattans, and a few small rattans made denser colonies. Swampy environments apparently suppressed the survival of non-climbing rattans strongly, but that of tall climbing rattans less so.     

Influence of leaf size on tree architecture: first branch height and crown dimensions in tropical rain forest trees

 First branch height is an important attribute of sapling architecture, as it defines the height at which prolonged lateral growth is possible. First branch height, measured on saplings of 70 species in tropical rain forests of Australia, Costa Rica, Panama, and Sabah, Malaysia, was highly correlated with leaf blade and petiole length. The observed relationship, first branch height ∝ blade length × (petiole length)^0.5, implies that the ratio of first branch height to blade length increases somewhat with increasing leaf size, among species with a given ratio of petiole to blade length. Orthotropic species, with more or less radially symmetric arrangements of leaves on ascending axes, had a mean first branch height of 7x that observed for plagiotropic species, with planar leaf arrangements. The greater first branch height of orthotropic species was associated with their larger leaves and longer petioles. Plagiotropic species had wider crowns than orthotropic species in the sapling stage, as assessed at the Costa Rican site. Thus, leaf dimensions influence the dynamics of crown construction (or visa versa), as well as affecting leaf energy balance and gas exchange. Received: 5 September 1997 / Accepted: 3 March 1998     

Modelling foliage characteristics in 3D tree crowns: influence on light interception and leaf irradiance

Because of the difficulty and time involved in making exhaustive measurements of the geometric parameters of large tree crowns, simplifying hypotheses are often used in 3D virtual plant modelling, but the effects on the radiation balance of each approximation are rarely assessed. Three hybrid walnut trees aged 7–9 years were digitized to analyse the effect of the crown geometric variables on light capture. The six studied variables were: (1) leaf area, (2) number of leaves per annual shoot, (3) position of leaves, (4) orientation of leaves, (5) leaflet inclination, and (6) lamina shape. For each variable, a sensitivity analysis compared a reference, based on observed values, with scenarios consisting of simplifying hypotheses. The total incident light intercepted during a bright day and the distributions of leaf irradiance were calculated using the Archimed radiative transfer model. Since some of the crown parameters were generated stochastically, the radiation simulations were repeated until results stabilised. Simplified models can be used to calculate with satisfactory results individual leaf area and number of leaves per shoot. Conversely, differentiating statistical distributions of individual leaf area between short and long shoots is more difficult and may generate errors up to 30%. Leaf clumping is a determining factor and requires correct grouping of leaves around the annual shoots bearing them. The effect of position of leaves along the shoot is less than 2%. Simple statistical distributions are adequate for representing leaf angle. Finally, the effect of specific leaf geometry is very important, but it can be approached using a limited number of representative leaf shapes.     

The influence of epiphyte cover on branch temperature in a tropical tree

The air temperature around three branches loaded with epiphytes in a tropical lowland rain forest in French Guiana was measured from mid-June to mid-July 1997. These data represent the first direct measurements of temperature close to epiphyte-loaded branches in a tropical lowland forest. The epiphytic biomass of one of the branches was removed after two weeks of measurements. These differences in stripped versus unstripped branch temperatures were positive during day time. A maximum difference of 4.8 °C was measured on a single sunny day; the maximum of four mid-day hours averaged over all days was 2.3 °C. Maxima were determined at locations close to the branch, representing high accumulations of humus, while nearly no differences were detected 75 cm away from the branch. At night, the temperature was cooler after epiphyte biomass removal; differences were up to –0.5 °C. Close to the branch, evaporation of stored water in humus cools the environment while latent heat transformation on epiphyte surfaces raises temperature. Shading under a branch prevents heating. Epiphytes reduce air circulation, keeping unheated air on branch undersides. At night, auto-heating of humus may occur through increased rates of respiration.     

Leaf attributes and tree growth in a tropical dry forest

Questions: How are leaf attributes and relative growth rate (RGR) of the dominant tree species of tropical deciduous forest (TDF) affected by seasonal changes in soil moisture content (SMC)? What is the relationship of functional attributes with each other? Can leaf attributes singly or in combination predict the growth rate of tree species of TDF? Location: Sonebhadra district of Uttar Pradesh, India. Methods: Eight leaf attributes, specific leaf area (SLA); leaf carbon concentration (LCC); leaf nitrogen concentration (LNC); leaf phosphorus concentration (LPC); chlorophyll concentration (Chl), mass‐based stomatal conductance (Gs_mass); mass based photosynthetic rate (A_mass); intrinsic water use efficiency (WUEi); and relative growth rate (RGR), of six dominant tree species of a dry tropical forest on four sites were analysed for species, site and season effects over a 2‐year period. Step‐wise multiple regression was performed for predicting RGR from mean values of SMC and leaf attributes. Path analysis was used to determine which leaf attributes influence RGR directly and which indirectly. Results: Species differed significantly in terms of all leaf attributes and RGR. The response of species varied across sites and seasons. The attributes were positively interrelated, except for WUEi, which was negatively related to all other attributes. The positive correlation was strongest between Gs_mass and A_mass and the negative correlation was strongest between Gs_mass and WUEi. Differences in RGR due to site were not significant when soil moisture was controlled, but differences due to season remained significant. The attributes showed plasticity across moisture gradients, which differed among attributes and species. Gs_mass was the most plastic attribute. Among the six species, Terminalia tomentosa exhibited the greatest plasticity in six functional attributes. In the step‐wise multiple regression, A_mass, SLA and Chl among leaf attributes and SMC among environmental factors influenced the RGR of tree species. Path analysis indicated the importance of SLA, LNC, Chl and A_mass in determining RGR. Conclusion: A _mass, SMC, SLA and Chl in combination can be used to predict RGR but could explain only three‐quarters of the variability in RGR, indicating that other traits/factors, not studied here, are also important in modulating growth of tropical trees. RGR of tree species in the dry tropical environment is determined by soil moisture, whereas the response of mature trees of different species is modulated by alterations in key functional attributes such as SLA, LNC and Chl.     

Water relations of indigenous versus exotic tree species,growing at the same site in a tropical montane forest in southern Ethiopia

The objective of the study was to compare the water relations of two indigenous [Podocarpus falcatus (Thunb.) Endl., Croton macrostachys Hochst. ex. Del.] and two exotic tree species (Eucalyptus globulus Labille., Cupressus lusitanica Miller) growing in the same location in the montane Munessa State Forest, southern Ethiopia. Stem flow was measured with Granier type thermal dissipation probes. Sap flux, normalized per unit sapwood area, and the total sapwood areas of the particular trees were used to estimate daily transpiration. Maximum daily transpiration values (60 kg water) were recorded for Croton when at full foliage. After shedding most of its leaves in the dry season transpiration was reduced to 8 kg per day. Eucalyptus had the next highest transpiration (55 kg), in this case at the peak of the dry season. It transpired 4–5 times more than Podocarpus and Cupressus trees of similar size. Maximum stem flux density was tree-size dependent only in Croton. Diurnal patterns of stem flux indicated that Croton, Eucalyptus and Podocarpus, in contrast to Cupressus, responded more directly to light than to atmospheric water pressure deficit. At high VPD (>1.0 kPa) stem flux reached a plateau in Croton and Podocarpus indicating stomatal limitation. Per unit leaf area Croton had the highest and Podocarpus and Cupressus the lowest daily transpiration rates. In summary, the pioneer tree Croton had the lowest and Podocarpus the highest water use efficiency. The contribution of the study to the understanding of the role of each tree species in the hydrology of the natural forest and the plantations is discussed.     

Leaf age and the timing of leaf abscission in two tropical dry forest trees

We used experimental defoliations to examine the effect of leaf age on the timing of leaf shedding in two tropical dry forest trees. Trees of the deciduous Bombacopsis quinata (bombacaceae, a.k.a. Pachira quinata) and the brevi-deciduous Astronium graveolens (anacardiaceae) were manually defoliated for three times during the rainy season. All trees started to produce a new crown of leaves 2 weeks after defoliation, and continued expanding leaves throughout the rainy season. At the transition to the dry season, the experimental groups consisted of trees with known differences in maximum leaf age. Defoliations resulted in declines in stem growth but did not affect the mineral content or water relations of the leaves subsequently produced. There was no effect of leaf age on the timing of leaf abscission in B. quinata. In A. graveolens, the initiation of leaf shedding followed in rank order, the maximum leaf age of the four treatments, but there was substantial coherence among treatments in the major period of leaf abscission such that trees completed leaf shedding at the same time. In the two species, leaf water potential (Ψ_L) and stomatal conducantce (g _S) declined with the onset of the dry season, reaching minimum values of –0.9 MPa in P. quinata and <–2.0 MPa in A. graveolens. Within each species, leaves of different age exhibited similar Ψ_L and g _S at the onset of drought, and then decreased at a similar rate as the dry season progressed. Overall, our study suggests that the environmental factors were more important than leaf age in controlling the timing of leaf shedding.     

热带森林乔木种群分布格局及其研究方法的比较

应用样地个体数为基础的方差／均值比率、Ｍｏｒｉｓｉｔａ分散指标,以及以个体距离为基础的最近邻体法、复合个体距离分析法对海南岛吊罗山山地雨林８个主要种群分布格局进行了比较研究．结果表明,８个种群为聚集或随机分布,４种测定方法中以复合个体距离分析法较好．     

Geographical variation and genetic analysis of leaf shape inCrepis tectorum (Asteraceae)

Canonical variate analysis of plants raised in a uniform environment was used to study the pattern of geographical variation in leaf shape ofCrepis tectorum (Asteraceae). The diversity in leaf shape was much greater among populations confined to areas with exposed bedrock in the Baltic region than among weed populations scattered throughout Europe and Canada. A Ward's clustering linked outcrop populations from the archipelago of SW. Finland and the islands of Öland (Sweden) and Saaremaa (Estonia) due to the deeply lobed leaves characterizing these populations, while outcrop populations along the coast of E. Sweden were grouped due to their weakly lobed, narrow and dentate leaves. Most of the weed populations were grouped together but there was no tendency for the variation in this group to be related to habitat or geographical location. A mosaic of variation reflected in sharp (random) differentiation among local populations was superimposed on the large-scale ecogeographical pattern.—Crossing data indicated that most of the variation in degree of leaf dissection is governed by one major gene with deeply lobed leaves dominant over weakly lobed leaves. I suggest that the simple pattern of inheritance may have favoured rapid evolutionary changes in leaf shape, particularly in the Baltic area which emerged relatively late from the sea. Genetic correlations may have constrained the pattern of variation at higher taxonomic levels, since some of the trait associations detected in a segregating F₂ generation were also found at the among-population level.