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The life span of leaves increases with their mass per unit area (LMA). It is unclear why. Here, we show that this empirical generalization (the foundation of the worldwide leaf economics spectrum) is a consequence of natural selection, maximizing average net carbon gain over the leaf life cycle. Analyzing two large leaf trait datasets, we show that evergreen and deciduous species with diverse construction costs (assumed proportional to LMA) are selected by light, temperature, and growing-season length in different, but predictable, ways. We quantitatively explain the observed divergent latitudinal trends in evergreen and deciduous LMA and show how local distributions of LMA arise by selection under different environmental conditions acting on the species pool. These results illustrate how optimality principles can underpin a new theory for plant geography and terrestrial carbon dynamics.

application/pdf, We investigated the leaf demography of a temperate woody liana, Akebia trifoliata, in a temperate forest in Japan, Akebia is semi-evergreen: some leaves are shed before winter, while others remain through the winter. Previous studies of semi-evergreen species found that variation in leaf life span was caused by variation in the timing of leaf emergence, Leaves that appeared just before winter over-wintered, while leaves appearing earlier were shed, However, it is unclear whether leaves of the same cohort (i.e., leaves that appear at the same time within a single site) show variation in life span under the effect of strong seasonality. To separate variation in life span among the leaves in each cohort from variation among cohorts, we propose a new method - the single leaf diagram, which shows the emergence and death of each leaf. Using single leaf diagrams, our study revealed that Akebia leaves within a cohort showed substantial variation in life span, with some over-wintering and some not. In addition, leaves on small ramets in the understory showed great variation in life span, while leaves on large ramets, which typically reach higher positions in the forest canopy, have shorter lives, As a result, small ramets were semi-evergreen, whereas large ramets were deciduous, The longer lives of leaves on small ramets can be interpreted as a shade-adaptive strategy in understory plants.

We review a series of papers based on Kikuzawa’s (1991) cost-benefit model for leaf longevity, including its extension to whole plants and entire communities in seasonal environments. This simple model of net carbon gain over the life of a leaf can explain relationships among key foliar traits such as the positive correlation between leaf longevity (L) and leaf mass per area (LMA) and the negative correlations between photosynthetic rate (A) and both L and LMA. The extension of the model to seasonal environments can explain and reproduce various biogeographical trends including bimodality in the distribution of evergreen species across latitude, increase and decrease in L of evergreen and deciduous species with shortening of the period favorable for photosynthesis (f), modulation of L-LMA relationships with f, and decrease in functional type richness in terms of phenology patterns towards higher latitudes and altitudes. Finally, the model suggests the possibility that the lifetime carbon gain by a single leaf can be extended by analogy to predict the productivity of forest ecosystems.

Two varieties of Aucuba japonica differ in ways that can be considered adaptive to differing geo-climatic conditions in their respective distribution ranges. Irrespective of growth stage, the mean leaf size of A. japonica var. japonica was significantly larger than A. japonica var. borealis. Smaller leaf size and ultimately smaller stature of A. japonica var. borealis are an advantage under the higher snow load and lower temperatures in the forests along the East Sea where the variety grows. Snow load also acted as an important driving force for structural modifications of A. japonica var. borealis from cellular level in leaves to the organization of branch extension growth. Global warming by changing snowfall patterns in Japan may lead to range shifts in the two varieties of A. japonica.

Few studies have been done on the quantification of stand-level leaf herbivory in tropical forests. We evaluated the significance of annual leaf loss due to folivorous insects on the calculation of aboveground net primary production (ANPP) in tropical rain forests along broad climatic and edaphic gradients on Mt. Kinabalu, Borneo. We estimated insect folivory at the stand level as the product of a lifetime leaf loss ratio and annual leaf production in the stand. We defined the lifetime leaf loss ratio as the ratio of litter-leaf mass consumed by folivorous insects to the total litter-leaf mass at the stand level. The lifetime leaf loss ratio ranged from 1.6 to 8.4 %. The annual leaf loss caused by folivorous insects ranged from 0.01 to 0.38 Mg C ha−1 year−1, or from 1.2 to 5.9 % of ANPP in these tropical rain forests. Our method of estimating folivory (1) simultaneously considers all the tree species, canopy layers, and species of folivorous insects, (2) avoids underestimating leaf herbivory due to the resorption of mobile organic and inorganic matter from senescent leaves at the time of leaf abscission, and (3) can readily be applied in forests elsewhere.

Aim At a global scale, the relationship of leaf longevity (LL) to mean annual temperature (MAT) is positive for deciduous species but negative for evergreen species. The aim of this paper is to understand the mechanisms underlying these contrasting patterns of leaf longevity, from a cost–benefit perspective. Location Global. Methods We tested our hypothesis that contrasting LL–MAT relationships in evergreen and deciduous species result from differing adaptations to variation in the length of the annual favourable period. We defined f as the portion of the year when monthly temperature and water availability were favourable. We examined whether the contrasting LL patterns with MAT can be also seen with f. Next, we calculated the optimal LL that maximizes carbon gain per unit time across a range of f. Results The contrasting LL patterns across MAT were also found across f. Our optimization model successfully reproduced the contrasting LL patterns across f for the evergreen (LL longer than 1 year) and deciduous plants. The model shows that longer LL is required to maximize carbon gain for evergreen plants in shorter f, while LL of deciduous plants decreases with decreasing f. Without any a priori trait association, the model reproduced the well-known LL–leaf mass per area (LMA) relationship. The model also reproduced observed shifts in LL–LMA relationships across MAT or f. Evergreen leaves in long f need greater LMA to maintain LL than those in shorter f. Main conclusions Observed contrasting LL–MAT patterns in deciduous and evergreen species can be reproduced via the simple rule of maximizing carbon gain across different lengths of favourable periods. Our model provides a mechanistic explanation for the empirical global patterns of several key leaf traits and their relationships.

Starting from an axiom that sunlight is the fundamental energy source for green plants, we derived some theorems in plant ecology. We began by reviewing the Monsi-Saeki model, which was the first to relate the structure of canopy and productivity. Optimum leaf area (and thus leaf biomass) were predicted from the Monsi-Saeki model, which also introduced the concept of constant final yield per unit land area. A relationship between total biomass (y) and plant number (n) per unit land area was derived by combining the principles of constant final yield and logistic plant growth, which is based upon the diminishing return of total individual photosynthesis due to self-shading, An analogous equation was obtained in the analysis of cumulative plant biomass (Y) against cumulative plant number (N) within a stand. Mass-number relationships among stands (y-n) and within a stand (Y-N) were revealed to be the same under one-sided competition for light. The self-thinning line is the point where individual plant’s growth becomes zero on the translocation of a Y-N relationship through time. Self-thinning is expected to occur due to the death of the smallest plants shaded by larger plants. The Monsi-Saeki modeling framework was reoriented considering leaf longevity, which is the optimal timing to replace individual leaves to maximize carbon gain of the plant. Under canopy ergodic hypothesis, which supposes space-time equivalence in the performance of leaves, leaf longevity can be used to circumvent the difficulties in the scaling from leaf to canopy. Gross primary production then can be estimated using functional leaf longevity together with the mean labor time of a leaf, two measures of the time during the leaf span when it can be photosynthetically active. Finally, if leaf longevity is used in a species-specific normalization constant, plant productivity can be described as an allometric function of plant mass. In that case, the relative growth rate of plants can be shown to have an inverse relationship to leaf longevity.

To explain why the composition of evergreen and deciduous forests changes along air temperature gradients, we measured several traits of single leaves from temperate deciduous and evergreen broadleaf trees with simultaneous and successive leaf emergence growing at different altitudes in the field. The parameters included seasonal net photosynthetic rate, longevity, mass per area, nitrogen content, and photosynthetic nitrogen-use efficiency. With decreasing altitude, the leaf longevity of deciduous broadleaf trees increased, whereas the maximum net photosynthetic rate decreased. In contrast, leaf longevity of evergreen broadleaf trees decreased, whereas the minimum net photosynthetic rate in winter increased. Along the air temperature gradient, the annual production of deciduous trees with simultaneous leaf emergence may be constant, because the integrated lifetime net photosynthetic rate (ILNPR) of a single leaf changed little. In comparison, deciduous trees with successive leaf emergence may show enhanced annual production with increasing air temperature, by increasing the total leaf number per branch and tree under an extended growing season. Temperate evergreen broadleaf tree species may also show increased annual production with increasing air temperature by sufficiently raising the number of the first-year leaves to the total leaves of branch and tree, which is accelerated by raising the integrated first-year net photosynthetic rate of the single leaf, despite little change in the ILNPR. With increasing air temperature from cool-temperate to warm-temperate zones, evergreen broadleaf tree species gain an advantage of the annual production over deciduous broadleaf tree species with simultaneous leaf emergence.

We analyzed crown development in Aucuba japonica Thunb. var. japonica resulting from the responses of phytoelements to habitat light conditions over a long period of time. Over the years, the degree of extension unit (EU) dimorphism and the degree of anisophylly were higher under shaded conditions than in brighter conditions. An overall temporally increasing pattern in the degree of EU dimorphism was found while no clear-cut trend was found in the case of anisophylly. EU length and number of leaves per EU co-varied in a spatio-temporal context. The number of terminal buds and their sizes acted as the key initiators of morphological differences of phytoelements which were further amplified following bud break. Leaf area density was displayed mostly in the apex peripheral layer of the crown and the apex layer received most of the incident light. There was a tradeoff between annual leaf production and mean leaf size. Depending on the heterogeneity of irradiance level within a crown, correlative growth inhibition caused higher EU mortality at brighter sites. Due to high mortality, shorter EUs had a mere role in the construction of structural framework of the crown except for the formation of some gaps. There was a strong convergence of EU dimorphism, anisophylly, EU extension growth and variations in leaf size towards formation of functional crown to reduce potential self-shading. Depending on the irradiance level, Aucuba japonica Thunb. var. japonica showed two different modes of crown expansion. At the brighter sites, individual crown expansion was progressive while at the darker sites, individual crown expanded in a diminishing manner and maintained a stable size. A plant’s “growth diminishing phase” appeared earlier at shaded sites than brighter sites.

Pre-dispersal seed predation by granivorous birds has potential to limit fruit removal and subsequent seed dispersal by legitimate avian seed dispersers in bird-dispersed plants, especially when the birds form flocks. We monitored pre-dispersal seed predation by the Japanese grosbeak, Eophona personata, of two bird-dispersed hackberry species (Cannabaceae), Celtis biondii (four trees) and Celtis sinensis (10 trees), for 3 years (2005, 2007 and 2008) in a fragmented forest in temperate Japan. Throughout the 3 years, predation was more intense on C. biondii, which, as a consequence, lost a larger part of its fruit crop. Grosbeaks preferred C. biondii seeds that had a comparatively lower energy content and lower hardness than C. sinensis, suggesting an association between seed hardness and selective foraging by grosbeaks. In C. biondii, intensive predation markedly reduced fruit duration and strongly limited fruit removal by seed dispersers, especially in 2007 and 2008. In C. sinensis, seed dispersers consumed fruits throughout the fruiting seasons in all 3 years. In C. biondii, variation in the timing of grosbeak migration among years was associated with annual variation in this bird's effects on fruit removal. Our results demonstrate that seed predation by flocks of granivorous birds can dramatically disrupt seed dispersal in fleshy-fruited plants and suggest the importance of understanding their flocking behaviour.

application/pdf, We investigated an effect of canopy position and a number of days after rainfall on reduction of photosynthetic rate in a Fagus crenata forest in summer 2008, during days when midday depression was not apparent. We compared in situ photosynthetic rate and photosynthetic rate that was calculated by photosynthetic light response curves measured in the morning. The ratio, in situ photosynthesis divided by the curve-estimated value, declined towards the end of each day for the upper leaves, but not for the lower leaves. Total photosynthesis was reduced only for the upper leaves by 12% during 5 days after the rainfall.

The life span of resource-acquiring organs (leaves, shoots, fine roots) is closely associated with species successional position and environmental resource availability. We examined to what extent leaf life span is related to inter- and intraspecific variation in seedling relative growth rate (RGR). We examined relationships between relative growth rate in mass (RGRM) or height (RGRH) and leaf life span, together with classical RGRM components [net assimilation rate (NAR), specific leaf area (SLA), leaf weight ratio (LWR), and leaf area ratio (LAR)] for seedlings of five hardwood species of different successional position across a wide range of environmental resource availability, including the presence or absence of leaf litter in shaded forest understory, small canopy gaps, and large canopy gaps. Both SLA and LAR were negatively correlated with RGRM along the environmental gradient for all species. However, positive correlations were observed among species within microsites, indicating that these two components cannot consistently explain the variation in RGRM. Both NAR and LWR affect interspecific, but not intraspecific, variation in RGRM. Leaf life span was negatively correlated with either RGRM or RGRH in both inter- and intraspecific comparisons. Species with short-lived, physiologically active leaves have high growth rates, particularly in resource-rich environments. Consequently, leaf life span is a good predictor of seedling RGR. Leaf life span affects plant performance and has a strong and consistent effect on tree seedling growth, even among contrasting environments.

application/pdf, It has been well established that leaf longevity is linked to the carbon economy of plants. We used this relationship to predict leaf lifetime carbon gains from leaf lifespan, and estimated the gross primary production (GPP) of a young deciduous forest of Japanese beech (Fagus crenata) located in central Japan. The light-saturated photosynthetic rates of the leaves were measured repeatedly during the growing season. We used the leaf lifespan to calculate the conversion coefficient from the light-saturated photosynthetic rate into the realized leaf lifetime carbon gain under field conditions. The leaf turnover rate was estimated using litter traps. GPP was estimated as the product of lifetime carbon gain per unit of leaf mass, and the annual leaf turnover rate. The GPP of the forest in 2007 was estimated to be , which was within the range of previously reported GPP values of beech forests in Japan, and was close to the GPP of a European beech forest, as estimated by eddy flux measurements.

application/pdf, Light absorption and use efficiency (LAUE mol mol−1, daily gross photosynthesis per daily incident light) of each leaf depends on several factors, including the degree of light saturation. It is often discussed that upper canopy leaves exposed to direct sunlight are fully light-saturated. However, we found that upper leaves of three temperate species, a heliophytic perennial herb Helianthus tuberosus, a pioneer tree Alnus japonica, and a late-successional tree Fagus crenata, were not fully light-saturated even under full sunlight. Geometrical analysis of the photosynthetic light response curves revealed that all the curves of the leaves from different canopy positions, as well as from the different species, can be considered as different parts of a single non-rectangular hyperbola. The analysis consistently explained how those leaves were not fully light-saturated. Light use optimization models, called big leaf models, predicted that the degree of light saturation and LAUE are both independent of light environment. From these, we hypothesized that the upper leaves should not be fully light-saturated even under direct sunlight, but instead should share the light limitation with the shaded lower-canopy leaves, so as to utilize strong sunlight efficiently. Supporting this prediction, within a canopy of H. tuberosus, both the degree of light saturation and LAUE were independent of light environment within a canopy, resulting in proportionality between the daily photosynthesis and the daily incident light among the leaves.

Pre-dispersal seed predation by a granivorous bird, the masked grosbeak (Eophona personata, Fringillidae), was investigated in two bird-dispersed trees, Celtis sinensis and Aphananthe aspera (Ulmaceae). The objectives of this study were to 1) measure direct damage of predation by grosbeaks on plant crops, 2) reveal the temporal pattern of predation within each tree species and its causal factors, and 3) test whether foraging grosbeaks hinder foraging of frugivorous birds, thereby indirectly impacting the reproduction of both tree species. A substantial amount of fruit and seed crop was consumed by grosbeaks (24.3% in Celtis; 55.5% in Aphananthe), and only 17.7% (Celtis) and 16.7% (Aphananthe) were removed by frugivorous birds. At the study site, the grosbeak population size fluctuated greatly during the fruiting seasons of both plant species. As for Celtis, predated seed density also fluctuated temporally, and the local population size of grosbeaks was responsible for predated seed density. In Aphananthe, predation was not fully explained by grosbeak populations or plant phenology, but its peak coincided with that of grosbeak population. These results suggest that pre-dispersal seed predation by granivorous birds can have large negative impacts on the bird-dispersed plants. Changes in local population size of granivorous birds can influence predatation and can affect reproductive success of the bird-dispersed plants available to the birds.

We examined the interactions between bird-dispersed plants and fruit-consuming birds with various feeding strategies, by reviewing the plant species consumed by 14 bird species in Japan with four feeding types: gulpers (five species), grinders (four species), crushers (four species), and peckers (one species). Our literature review provided information on the plant species consumed by the birds in Japan and the morphological traits of the fruits: fruit volume, seed mass and number, pulp type (fleshy, dry, or arillate), and plant height (tall, medium, or small). Using these data, we examined the diversity of plant species consumed by each bird and the fruit morphological traits that affected fruit selection. The five gulpers consumed fruits from the largest number of plants, followed by the four grinders, the four crushers, and the one pecker. The gulpers and grinders consumed a wider variety of fruits than were consumed by the crushers and the pecker. Logistic regression analysis revealed that some crushers and the pecker preferred plants with dry or arillate pulp around the seeds. Our results suggest that a frugivorous bird’s feeding strategies, and particularly its fruit-handling behaviors and the fruit parts it ingests, influence the diversity of plants it consumes. The crushers and the pecker, which feed exclusively on seeds, require more effort and time to consume this type of food, and this might cause a strong preference for specific fruit traits and thus, consumption of a lower diversity of plant species.

application/pdf, Allometric scalings and a logistic equation assume that whole-plant photosynthetic rate under resource-unlimited conditions is proportional to leaf area. We tested this proportionality for the herb Helianthus tuberosus. During growth, we repeatedly measured the percentage of leaves with high, medium, and low photosynthetic capacity to estimate the whole-plant sum of photosynthetic capacity. We found that the whole-plant sum of the light-saturated photosynthetic rate of leaves is proportional to the whole-plant leaf area, disregarding the dynamics of the leaf population. We also found that the daily photosynthesis of each leaf appeared as a linear function of the light-saturated photosynthetic rate of that leaf, as predicted by the optimization theory. Using those results, we expressed whole-plant photosynthetic rate as a product of the light-saturated whole-plant photosynthetic rate and an efficiency index that reflects resource limitation as in the logistic equation. This efficiency decreased with increasing leaf area, reflecting light limitation. Therefore, realized whole-plant photosynthetic rate is not proportional to leaf area. These "diminishing returns" are well explained by a simple saturating curve, such as the logistic equation.

We studied flowering and fruiting seasonality of understory shrubs of genus Medinilla (Melastomataceae) in the lower montane forest on Mount Kinabalu, Borneo, in relation to seasonal change in air temperature, rainfall, and solar radiation. Eight sympatric species showed either annual or biannual patterns. The number of species bearing f lower buds and flowers increased biannually, indicating that two seasons were favorable for flower budding and flowering of Medinilla species. Individuals of most species started flower budding during Januar y–March, showing strongly negative correlations with seasonal patterns of mean or minimum air temperature in previous a few weeks. The number of fruiting species peaked during May-August and increased when air temperature and solar radiation were high. These findings suggested that flowering activity of most Medinilla species may be regulated by seasonality of air temperature through floral initiation stimulated by low temperature. In addition, the high fruiting activity during period with high temperature and insolation indicated that such climatic conditions may facil i tate the development of fruits and seeds of understor y plants growing in cool and poor-light conditions, because photosynthesis and other physiological reactions are activated to produce compounds necessary for the development of fruits and seeds.

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.

While leaves typically emerge near shoot apices around the outer surface of a plant canopy, their relative position “moves” deeper into the canopy as additional leaves emerge. The photosynthetic capacity (A max) of a given leaf can be expected to decline over time as its relative position (P r) in the canopy becomes progressively deeper; this can be observed as a spatial gradient with the A max of leaves declining distally from the shoot apex. As a consequence, we propose that the photosynthetic capacity averaged over a single leaf’s lifespan is equivalent to the average photosynthetic capacity of the entire plant canopy at a given time; in other words, there is an ergodic time to space averaging in the organization and development of plant canopies. We tested this “canopy ergodic hypothesis” in two woody (Alnus sieboldiana and Mallotus japonica) and two herbaceous (Polygonum sachalinensis and Helianthus tuberosus) species by following the photosynthetic capacity in 100 individual leaves from the time of their emergence until their death. We compared the average photosynthetic capacity of individual leaves through time (time-average) to the average photosynthetic capacity of all the leaves along a shoot at the time of emergence of the focal leaf (space-average). We found that A max and P r were positively correlated and that the time-averages of three plant species (Alnus, Mallotus, and Helianthus) were not significantly different from the corresponding space-averages, although the averages differed among individual plants. Polygonum, however, did show significant differences between time and space averages. Ergodicity appears to apply to the leaf–canopy relationship, at least approximately—the average photosynthetic capacity of a single leaf through time (time-average) can represent the average photosynthetic capacity of the entire canopy.

We investigated the sapling leaf display in the shade among trees of various leaf lifespans co-occurring under the canopy of a warm-temperate conifer plantation. We measured leaf-area ratio (aLAR) and morphological traits of saplings of evergreen broadleaved tree species and a deciduous tree species. Although we found large interspecific and intraspecific differences in aLAR even among saplings of similar size in the homogeneous light environment, we did not find a consistent trend in aLAR with leaf lifespan among the species. While deciduous trees annually produced a large leaf area, some evergreen broadleaved trees retained their leaves across years and had aLAR values as high as those of deciduous trees. Among leaf-level, shoot-level, and individual-level morphological traits, aLAR was positively correlated with current-year shoots mass per aboveground biomass in deciduous trees, and with the area of old leaves per aboveground mass in evergreen broadleaved trees. Thus, tree-to-tree variation in the degrees of annual shoot production and the accumulation of old leaves were responsible for the interspecific and intraspecific variations in aLAR.

Tree growth, especially diameter growth of tree stems, is an important issue for understanding the productivity and dynamics of forest stands. Metabolic scaling theory predicted that the 2/3 power of stem diameter at a certain time is a linear function of the 2/3 power of the initial diameter and that the diameter growth rate scales to the 1/3 power of the initial diameter. We tested these predictions of the metabolic scaling theory for 11 Japanese secondary forests at various growth stages. The predictions were not supported by the data, especially in younger stands. Alternatively, we proposed a new theoretical model for stem diameter growth on the basis of six assumptions. All these assumptions were supported by the data. The model produced a nearly linear to curvilinear relationship between the 2/3 power of stem diameters at two different times. It also fitted well to the curvilinear relationship between diameter growth rate and the initial diameter. Our model fitted better than the metabolic scaling theory, suggesting the importance of asymmetric competition among trees, which has not been incorporated in the metabolic scaling theory.

Yan-Shih Lin [et al.].- Received 16 August 2014, Accepted 16 January 2015, Published online 02 March 2015, Stomatal conductance (gs) is a key land-surface attribute as it links transpiration, the dominant component of global land evapotranspiration, and photosynthesis, the driving force of the global carbon cycle. Despite the pivotal role of gs in predictions of global water and carbon cycle changes, a global-scale database and an associated globally applicable model of gs that allow predictions of stomatal behaviour are lacking. Here, we present a database of globally distributed gs obtained in the field for a wide range of plant functional types (PFTs) and biomes. We find that stomatal behaviour differs among PFTs according to their marginal carbon cost of water use, as predicted by the theory underpinning the optimal stomatal model1 and the leaf and wood economics spectrum2, 3. We also demonstrate a global relationship with climate. These findings provide a robust theoretical framework for understanding and predicting the behaviour of gs across biomes and across PFTs that can be applied to regional, continental and global-scale modelling of ecosystem productivity, energy balance and ecohydrological processes in a future changing climate.

The light environment and growth traits of the pioneer tree species Litsea citriodora in a recently clear-cut plantation were investigated in order to reveal the establishment process and growth of this species under annual weeding after clear-cutting. We investigated the light environments and the morphology, physiology and aboveground architecture of L. citriodora saplings in a plot that included both clear-cut open areas and forest floor under a conifer canopy. Dense populations of L. citriodora saplings were found in the open sites but few were observed on the forest floor. Saplings that originated from old stumps (sprout-saplings) were tall in height and dense, but seedlings were sparse and lower in height than the competitive tall herbaceous species Solidago altissima. Saplings of L. citriodora showed a higher leaf area per aboveground mass and greater area-based photosynthetic capacity than saplings of the co-occurring pioneer tree species Mallotus japonicus and Clerodendron trichotomum. Moreover, the L. citriodora saplings had a main stem with a larger length per mass ratio and more efficiently elongated per unit aboveground mass than M. japonicus and C. trichotomum. Sprout-saplings of L. citriodora attained rapid vertical elongation with rapid biomass acquisition as a result of their aboveground shoot architecture, allowing competition with S. altissima. Clear-cutting and subsequent weeding not only created open sites favorable for this pioneer tree, but also promoted the formation of sprouts, allowing sprout-saplings with rapid vertical growth to successfully establish in the clear-cut zone by inhibiting complete coverage by other pioneer trees.

The assimilation of carbon by plant communities (gross primary production [GPP]) is a central concern in plant ecology as well as for our understanding of global climate change. As an alternative to traditional methods involving destructive harvests or time-consuming measurements, we present a simple, general model for GPP as the product of the lifetime carbon gain by a single leaf, the daily leaf production rate, and the length of the favorable period for photosynthesis. To test the model, we estimated leaf lifetime carbon gain for 26 species using the concept of mean labor time for leaves (the part of each day the leaf functions to full capacity), average potential photosynthetic capacity over the leaf lifetime, and functional leaf longevity (leaf longevity discounted for periods within a year wholly unfavorable for photosynthesis). We found that the lifetime carbon gain of leaves was rather constant across species. Moreover, when foliar biomass was regressed against functional leaf longevity, aseasonal and seasonal forests fell on a single line, suggesting that the leaf production rate during favorable periods is not substantially different among forests in the world. The gross production of forest ecosystems then can be predicted to a first approximation simply by the annual duration of the period favorable for photosynthetic activity in any given region.

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.

We have investigated stem turnover strategy for Lindera umbellata, an understory shrub that sprouts from its rootstock under natural conditions to replace constituent stems, on the basis of the hypothesis that the multiple-stemmed form of woody species is an adaptation enabling efficient reproduction in high-stress environments. We tested the hypothesis that the timing of stem replacement maximizes sexual reproduction for the shrub. We developed a model for the time of optimum replacement of a stem by a daughter stem which maximizes the sexual reproduction of a shrub and tested the model using L. umbellata growing in the field. From the model, the optimum time of replacement of a stem with a daughter stem is when cumulative sexual reproduction per unit time for the stem is maximum. In practice, this will be the last age (t opt) at which annual sexual reproduction in a stem can potentially exceed cumulative sexual reproduction per unit time for the stem. Half of the stems died at almost t opt and had sexually mature daughter stems at that time. Other stems, however, died at times more remote from t opt when daughter stems were sexually immature. It is thought that normal replacement of the latter stems was prevented by accidents such as breakage. We conclude that clumps of L. umbellata achieve efficient sexual reproduction by stem replacement at the optimum time, although accidents can, to some extent, determine when the stem actually dies.

The physiological basis of photosynthesis during winter was investigated in saplings of five evergreen broad-leaved species (Camellia japonica L., Cleyera japonica Thunb., Photinia glabra (Thunb.) Maxim., Castanopsis cuspidata (Thunb.) Schottky and Quercus glauca Thunb.) co-occurring under deciduous canopy trees in a temperate forest. We focused on temperature dependence of photosynthetic rate and capacity as important physiological parameters that determine light-saturated rates of net photosynthesis at low temperatures during winter. Under controlled temperature conditions, maximum rates of ribulose bisphosphate carboxylation and electron transport (V cmax and J max , respectively) increased exponentially with increasing leaf temperature. The temperature dependence of photosynthetic rate did not differ among species. In the field, photosynthetic capacity, determined as V cmax and J max at a common temperature of 25 °C (V cmax (25) and J max (25) ), increased until autumn and then decreased in species-specific patterns. Values of V cmax (25) and J max (25) differed among species during winter. There was a positive correlation of V cmax (25) with area-based nitrogen concentration among leaves during winter in Camellia and Photinia. Interspecific differences in V cmax (25) were responsible for interspecific differences in light-saturated rates of net photosynthesis during winter.

Photosynthetic traits of the evergreen broadleafed species Camellia japonica L. and Quercus glauca Thunb. were continuously investigated during autumn and winter using saplings that grew in different light environments (gap, deciduous canopy understory, and evergreen canopy understory) in a temperate forest. Light-saturated rates of net photosynthesis in midwinter and spring were lower than those in autumn. Photosynthetic capacity, scaled to a common leaf temperature of 25 °C, increased or remained stable after autumn and then decreased in spring in most leaves. Photosynthetic traits per unit leaf area were different among leaves in different light environments of both Camellia and Quercus during most periods. However, photosynthetic traits per unit leaf mass did not differ among leaves in different light environments, suggesting that differences in photosynthetic traits were mainly due to different leaf mass per area among leaves. Photosynthetic rates under light availability typical in the environment were lower in winter than in autumn in leaves in the sun in a gap but were not different in leaves in the shade under evergreen canopy trees. Thus, the importance of winter carbon gain for annual carbon gain is small in leaves in a gap but is large in leaves under evergreen canopy trees.

In trees, leaf life span is closely related to successional status. Although leaves are attached to shoots, shoot life span has been insufficiently studied in the context of ecological systems. Interspecific variation in shoot survivorship was investigated over 27 months in 15 temperate hardwood tree species. Relationships between shoot architecture and shoot survival were also investigated. Shoot life span was shortest in early successional species, and longest in late successional species, in each of the families Betulaceae and Fagaceae. In Salicaceae, all of which were early successional species, shoot life span was longer in mountainous than in riparian species. Early successional or riparian species distributed longer shoots densely, even in proximal positions on mother shoots, resulting in mutual shading and consequent early and massive shoot shedding. By contrast, late successional or mountainous species concentrated shoots in distal positions, allowing shoots to receive equally favorable light, resulting in a longer life span. These results reveal close relationships between shoot life span and environmental resource availability or successional status and suggest a causal relationship between shoot shedding and shoot architecture.

Anisophylly, having leaves different in size and/or shape, was quantified in adult Aucuba japonica and simulations were carried out to evaluate the effects of anisophylly on the extent of self-shading at the single-shoot level as well as at the whole-canopy level. Clear anisophylly was observed in the individual after switching from the single-stemmed juvenile stage to the multi-stemmed adult stage. In such plants, leaf area in the canopy abruptly increased. The effective display of adult foliage involved a variety of morphological changes in addition to anisophylly, most prominently reduction in leaf size compared to juveniles. The simulation results indicate that diversity of leaf size and shape is an effective means of minimizing self-shading as well as allowing the efficient exploitation of a larger canopy volume in adult plants. Anisophylly also increased the biomass use efficiency of individual plants at maturity. Taken together, having diverse leaf forms is superior to having a single leaf form for maximizing area acquisition and for efficiently filling the acquired area. We therefore conclude that the anisophylly expressed in A. japonica is adaptive.

In order to clarify the recovery process of the subtropical forest on Okinawa Island, southern Japan, biomass accumulation and the successional trend of species diversity with time were investigated by comparing plots of old-growth and clear logged secondary forests. Self-thinning was an important factor in the development of young secondary forests, and the small variance in tree size within a stand was related to the stand not being fully stratified after clear-cutting. A large variance of size structure in old secondary and old-growth forests implies re-initiation of the understorey. Additionally, the trajectory of stand development indicated that the subtropical forest quickly recovered aboveground biomass, which reached its upper limit at about 50 years after disturbance. However, there was a large distinction in species diversity between the secondary forests and old-growth forests. The diversity of forest floor plants did not recover well after being clear-cut. This indicates that management of the subtropical forest should not only take timber-oriented tree species into account, but also the biodiversity in ground flora. The secondary forests were characterized by Castanopsis sieboldii and Schima wallichii, and the monopolization of C. sieboldii through secondary succession had a negative influence on species diversity. Distylium racemosum dominated at the late development stage and was considered a long-lived competing species that reduced the dominance of C. sieboldii and facilitated the co-occurrence of understorey species. Light-demanding pioneer tree species such as S. wallichii that regenerated after logging should be replaced by competitive effects of climax species, and thus relayed floristic change might increase species diversity along secondary succession.

In dioecious clonal plants, the reproductive effort required to set seeds will be responsible for the larger investment in sexual reproduction by females. If there will be a trade-off in resource allocation between sexual and clonal reproduction, this differential sexual reproduction will lead to sexual differentiation in the relative amount of clonal reproduction. To test this prediction, we studied differences between the sexes in their phenologies and investments in sexual and vegetative reproduction (clonal reproduction by means of bulbils) with respect to ramet size in a dioecious clonal plant, Dioscorea japonica Thunb. The period of bulbil production overlapped the period during which infructescences developed. Females flowered later, produced heavier inflorescences, and fewer flowers per inflorescence than did males. Regression analysis using the size of the individual plants demonstrated that large females made smaller investments in inflorescences and larger investments in sexual reproduction than did large males. In contrast, females invested fewer resources in vegetative reproduction than did males. However, the total investments in sexual and vegetative reproduction did not differ between the sexes. These results supported our hypothesis on the sexual differentiation in sexual and clonal reproduction.

Anisophylly in Aucuba japonica Thunb. occurs exclusively in axillary buds on shoots of individuals that have reached reproductive maturity; juvenile plants or sprouts and shoots from terminal vegetative buds on adult plants are isophyllous. The initially smaller leaf primordium in each anisophyllous leaf pair gives rise to the larger final leaf size. Immediately before bud break, the size of the initially smaller primordium is already almost twice as large as the initially larger primordium, and the size differential is further amplified following bud break. The degree of aniso phylly, however, varies among the nodes of a shoot, depending on leaf pair orientation (tangential or parallel to the inflorescence axis) and nodal position. Paired leaves approach isophylly when they originate tangential to an inflorescence but become anisophyllous when originating parallel to an inflorescence. The degree of anisophylly depends on crown light conditions through effects on terminal bud size and foliage distribution on the shoot, but ultimately appears to arise from space limitations and crowding between the leaf primordia and the developing inflorescence in terminal reproductive buds.Key words: Aucuba, anisophylly, bud internal morphology, developmental anatomy, developmental constraints.

* Here we investigated photosynthetic traits of evergreen species under a deciduous canopy in a temperate forest and revealed the importance of CO2 assimilation during winter for annual CO2 assimilation. * Saplings were shaded by the canopy trees from spring through to autumn, but were less shaded during the winter months. Photosynthetic rates at light saturation (Aarea) were lower during winter than during the growing season. Aarea was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus during the winter, but differed little during summer and autumn. * Estimated daily CO2 assimilation (Aday) was higher during the winter than during the growing season in Camellia, Ilex and Photinia but was higher than that during the growing season only at the beginning and end of winter in Castanopsis, Cleyera and Quercus. Aday was higher in Camellia, Ilex and Photinia than in Castanopsis, Cleyera and Quercus but differed little among them during the growing season. * These results reveal the importance of winter CO2 assimilation for the growth of Camellia, Ilex and Photinia. Furthermore, differences in annual CO2 assimilation among species are strongly modified by species-specific photosynthetic traits during the winter under deciduous canopy trees.

We tested whether the difference in shoot production patterns of reproductive and vegetative shoots is only due to resource or meristem availability or also due to species-specific factors. Rates of shoot production by four shoot types (reproductive long shoots, vegetative long shoots, reproductive short shoots, and vegetative short shoots) in Betula platyphylla Sukatchev var. japonica (Miq.) Hara, Betula davurica Pall., Betula ermanii Cham., Betula grossa Sieb. et Zucc., and Betula maximowicziana Regel were compared. In the first three species, each shoot type produced all four shoot types. However, in the latter species, limited shoot production pathways were found both in reproductive shoots and in vegetative shoots, which do not carry any costs associated with reproduction. Furthermore, shoot production by reproductive shoots was not always diminished, but rather was enhanced compared with that by vegetative shoots in B. maximowicziana. These results suggest the importance of species-specific patterns in shoot production, in addition to previously suggested explanations involving resource or meristem limitation.Key words: species specificity, cost of reproduction, Betula, reproductive shoots, vegetative shoots.

The mean labor time of a leaf (hour/day−1) is defined as the ratio of mean daily photosynthetic rate of a leaf (Da; mol m−2 day−1) to the mean value of potential hourly photosynthetic rate (60 ⋅ 60Amax mol m−2 h−1) of the leaf. A model was proposed to estimate mean labor time of leaves. Mean labor time was obtained as the product of 24 (hours/day−1) and the four effects, each of which reduces production of a leaf: diel change in light (Diel Effect), reduction in light during cloudy and rainy days (Cloudy Effect), shading on the focal leaves (Shading Effect), and midday and afternoon depression in photosynthesis (Depression Effect). These four effects were estimated for open grown saplings of alder (Alnus sieboldiana), by measuring instantaneous photosynthetic rate and photon flux density above each leaf. The potential daily photosynthetic rate calculated from diel light condition in a clear day was 46.5% of hypothetical daily photosynthetic rate where maximum instantaneous photosynthetic rate was assumed to last throughout the life of the leaf (Diel Effect). The average of the daily photosynthetic rate considering clear, cloudy and rainy days was 79.7% of the clear day (Cloudy Effect). The photosynthetic rate estimated from light condition on the leaf was 85.6% of that in the open site (Shading Effect). Midday depression reduced the daily photosynthetic rate to 72.1% of the potential daily photosynthetic rate (Depression Effect). The product of the four effects multiplied by 24 h gave the estimate of mean labor time of leaves to be approximately 5.5 (h/day−1).

Summary • Here we propose a new method for classifying aerial stems of woody plants by developmental stage, using the logarithmic reciprocal of relative growth rate (LRR) as an indicator of developmental stage. • Stem analyses were conducted on naturally dead aerial stems of Lindera umbellata to clarify the changes in LRR over a lifetime. LRR, number of current-year shoots, and the recruitment and mortality rates of shoots of living stems were investigated. • LRR was at a minimum value at age 1 yr and at a maximum just before each stem died. There was little difference between the ranges of stem LRR. The recruitment and mortality rates of shoots depended on LRR. • LRR satisfied the necessary and sufficient condition for a variable as an indicator of stage better than either age or size. The LRR-structured model accurately demonstrates the real demographic processes in shoot populations over a lifetime of aerial stems. This result supports the utility of LRR as an indicator of stage. The method using LRR can be applied to analyses for other growth processes.

Phenological responses of leaves and roots were studied in the tropical montane forests of Mount Kinabalu, Borneo. Soil nutrient supply, in addition to the supply of light and water, is a potential abiotic factor influencing plant phenology in the tropics. The main objective of this study was to evaluate the contribution of soil nutrient supply to plant productive phenology. Fertilization experiments, including controls, nitrogen fertilized and nitrogen and phosphorus fertilized treatments, were conducted on three vegetation types in different moisture environments. Responses of leaves and roots were compared among treatments and among vegetation types. Leaf flushing was induced by nitrogen fertilization in the upper montane forest, where extremely wet moisture conditions are associated with cloud cover. This induction of leaf flushing by fertilization was not observed in the other forests. Root growth was suppressed by fertilization when leaf flushing was not induced by fertilization. These results indicate that soil pulsed nutrient release could be a cue for leaf flushing in a tropical wet environment, and that leaf phenology could be regulated by external abiotic factors and root phenology could be regulated by internal plant demands.

Overproduction of flowers increases the attractiveness of a plant to pollinators, but results in increased geitonogamy. In general, flower abscission has been considered to be an event subsequent to the overproduction of flowers. We observed pollinator behavior in Tilia, a self-incompatible, insect-pollinated tree. We found that pollinators sequentially visited inflorescences within a tree; however, when they met with flower abortion by abscission, they were apt to move long distances and leave the tree. We propose that plants may utilize flower abscission as a method for regulating the movements of pollinators by disturbing them in order to prevent geitonogamy.

Summary 1 Leaf emergence, leaf longevity, light regime and photosynthetic rates were investigated in order to clarify the morphological and phenological adaptations to light conditions by avoiding self-shading in two herbaceous (Polygonatum odoratum and Polygonum sachalinensis) and two woody (Fagus crenata and Alnus sieboldiana) plants in artificially created open habitats in Japan. 2 Fagus and Polygonatum open their leaves simultaneously as a flush during a short period at the start of the growing season (simultaneous foliar phenology), while Alnus and Polygonum open their leaves one by one successively for a longer period (successive foliar phenology). 3 Light conditions at the level of single leaves, defined as photon flux density relative to that above the plant, were essentially the same throughout a growing season for simultaneous species. On the other hand, light conditions for the two successive species degraded with time. There were gradients of light from the distal to basal part of a shoot only in successive species. 4 Reflecting the abrupt decrease in irradiance with time, photosynthetic rates of individual leaves decreased quickly with time in successive species (Alnus and Polygonum), while those of simultaneous species (Fagus and Polygonatum) decreased slowly. Photosynthetic rates of the canopy as a whole, however, were maintained constant over the season in successive species by replacing leaves frequently. Canopy-level photosynthesis decreased slowly with time in the two simultaneous species. 5 Successive leaf emergence is adaptive in open habitats such as flood plains and canopy gaps, while simultaneous leafing is adaptive in light-limited habitats such as the forest understorey.

Light and water have only been discussed in the leaf phenology studies of low latitude tropics, though soil nutrients were also included as potential contributive factors. We investigated the relationship between these environmental factors and leaf phenology in the tropical montane forests of Mount Kinabalu, Borneo. Three montane forests of different vegetation were compared during the 1998 El Nino drought in order to differentiate the effect of each environmental factor. As a result, the relationship between soil pulsed nutrient release and leaf flushing was denoted in the forests with an affluent water supply, while water stress suppressed leaf flushing in all vegetation. However, the contribution of light could not be determined. This study is the first to indicate the contribution of soil nutrients to leaf phenology in the tropics.

An altitudinal survey of correspondences between fruiting phenologies of fleshy-fruited tree species and seasonal dynamics of frugivorous birds on Mt. Kinabalu in Borneo was carried out for 50 weeks across four vegetation types: a hill forest (800 m asl), a lower montane forest (1700 m), an upper montane forest (2000-3000 m) and a subalpine forest (3000-3500 m). In the hill forest, a large fruiting peak following the general flowering phenomenon was observed during October-November in 1996 and a fruitless period was observed during February-April in 1997. During the fruitless period, the number of resident frugivorous birds decreased. A bimodal fruiting pattern was observed in the lower montane forest. A large number of frugivorous temperate migrants were observed when the fruiting peak occurred. The number of resident frugivorous birds increased and several lowland bird species were observed, when the number of resident birds decreased in the hill forest. In the upper montane forest and the subalpine forest, more continuous and irregular fruiting patterns without outstanding peaks were observed and the number of resident frugivorous birds was more stable throughout the year. These suggested (1) there was a strong relationship between fruiting seasonality and seasonal dynamics of temperate migrants in the lower montane forest; (2) seasonal altitudinal movements of lowland bird species to montane vegetation might occur during the fruitless period in the lowland forest; and (3) the continuous fruiting pattern in the higher vegetation zones might be related to the scarcity of available frugivorous birds. The hypothesis that the influx of temperate migrants into the montane vegetation of Mt. Kinabalu is affected by density and habits of resident frugivorous birds is supported. Montane vegetation in Borneo plays an important role as temporal refugia for temperate and altitudinal migrants by supplying fruit resources.

The sex expression of Tilia japonica is functional andromonoecy (an andromonoecious system with abortion of perfect flowers). Some of protandrous flowers are aborted after shedding pollen grains and thus are functionally male flowers (FMF). When both male and female organs are retained in a flower, the plants can more flexibly regulate sex allocation, or resource allocation to male and female functions than true andromonoecious plants, which is considered as an adaptive significance of functional andromonoecy. However, the plants have to pay some costs of female organ in FMF. For functional andromonoecious plants, there is a conflict between flexibility and cost in determining the timing of flower abortion, or arrest investing in female functions in a flower. We clarified that (i) differentiation of the timing of flower abortion caused two types of FMF: short-style (SS) and normal-style (NS) flowers; (ii) SS can be produced at a lower cost than NS, and (iii) plants having NS can flexibly regulate sex allocation following a sudden change in conditions. Hence, we concluded that differentiation of the timing of flower abortion makes a compromise of the conflict. We also found that NS is more frequent than SS, and we discuss the adaptive significance of keeping potential fertility.

Two empirical laws, formulated independently, are known to be well satisfied in even-aged plant monocultures. One relates yield to plant density in different plant populations, and the other relates cumulative plant mass to cumulative plant number from the largest individual within a population. In this paper, we construct a mathematical model of plant growth under asymmetric competition between individuals in a population, where large individuals grow larger than small individuals because they pre-empt resources, especially light. The model categorizes influences on the growth of a plant into those from individuals larger than itself, and those from all individuals in the population. We derive the two laws from our model. Thus, individual growth, determined by asymmetric interaction between individuals in a population, can explain the two different laws relating to plant populations.

International audience; Growth of individual trees, population dynamics of first-order branches within individuals, and growth and mortality of first-order branches were followed for two years in an plantation of Betula platyphylla in central Hokkaido, northern Japan. The data were analyzed by stepwise regressions. The relative growth rate in terms of above-ground biomass of individuals was negatively correlated with a log-transformed competition index (ln(CI)), which was calculated for each individual from the size and distance of its neighbours. The change in branch number within an individual was also correlated with ln(CI). The growth and mortality of branches was correlated with the size of branches, size of individuals, growth of individuals, relative height of branches, and ln(CI). Generally, the patterns revealed by the regressions were consistent with what was expected and can be used as references against which the behavior of more detailed process-based models can be checked.; Modèles de croissance individuelle, dynamique de développement des branches et croissance et mortalité des branches du Betula Platyphylla. La croissance des arbres individuels, la dynamique de développement des branches de premier ordre sur les arbres individuels ainsi que la croissance et la mortalité des branches de premier ordre ont été étudiées pendant deux ans dans une pépinière de Betula Platyphylla de la région centrale du Hokkaido dans le nord du Japon. Les modèles de croissance individuelle, la dynamique de développement des branches et la croissance et la mortalité des branches ont été analysées selon leur régression progressive. Le taux de croissance relatif en termes de biomasse aérienne des arbres individuels s'est avéré en rapport inverse à l'index de concurrence des grumes (ln(CI)), après calcul pour chaque individu d'après la taille et l'éloignement de ses voisins. Le changement du nombre de branches sur un même individu est également en rapport avec ln(CI). La croissance et la mortalité des branches s'est avérée en rapport avec la taille des branches, la taille des individus, la croissance des individus, la hauteur relative des branches et ln(CI). En général, les modèles mis en évidence par les régressions sont conformes aux hypothèses avancées et peuvent servir de référence pour le contrôle d'autres modèles plus détaillés.