Contrasted allometries between stem diameter,crown area,and tree height in five tropical biogeographic areas

Key message

Across five biogeographic areas, DBH-CA allometry was characterized by inter-site homogeneity and intra-site heterogeneity, whereas the reverse was observed for DBH-H allometry.

Abstract

Tree crowns play a central role in stand dynamics. Remotely sensed canopy images have been shown to allow inferring stand structure and biomass which suggests that allometric scaling between stems and crowns may be tight, although insufficiently investigated to date. Here, we report the first broad-scale assessment of stem vs. crown scaling exponents using measurements of bole diameter (DBH), total height (H), and crown area (CA) made on 4148 trees belonging to 538 species in five biogeographic areas across the wet tropics. Allometries were fitted with power functions using ordinary least-squares regressions on log-transformed data. The inter-site variability and intra-site (sub-canopy vs. canopy trees) variability of the allometries were evaluated by comparing the scaling exponents. Our results indicated that, in contrast to both DBH-H and H-CA allometries, DBH-CA allometry shows no significant inter-site variation. This fairly invariant scaling calls for increased effort in documenting crown sizes as part of tree morphology. Stability in DBH-CA allometry, indeed, suggests that some universal constraints are sufficiently pervasive to restrict the exponent variation to a narrow range. In addition, our results point to inverse changes in the scaling exponent of the DBH-CA vs. DBH-H allometries when shifting from sub-canopy to canopy trees, suggesting a change in carbon allocation when a tree reaches direct light. These results pave the way for further advances in our understanding of niche partitioning in tree species, tropical forest dynamics, and to estimate AGB in tropical forests from remotely sensed images.

     

Nonlinear mixed-effects branch diameter and length models for natural Dahurian larch (<Emphasis Type="Italic">Larix gmelini</Emphasis>) forest in northeast China

Key message

We developed the generalized branch diameter and length models using the multi-level nonlinear mixed-effects techniques for the natural Dahurian larch ( Larix gmelini ) forest in northeast China.

Abstract

Dahurian larch (Larix gmelini) is the most commercially cultivated timber species in northeastern China due to its ecological prevalence and its superior wood attribute. However, its timber quality was largely driven by the crown architecture, i.e., the number, size and distribution of branches. The majority of branch-level models in the literature are focused on planted forests, which have substantially different crown architecture than that grown in natural mixed forests. Therefore, the goal of this investigation was to develop branch diameter and length models for Dahurian larch that are grown in natural mixed forests. A multi-level nonlinear mixed-effects model technique, including the fixed-effects, random-effects, variance functions and correlation structures, was employed to develop the branch growth models. The results suggested that the cumulative branch diameter and length were both increased with the increases of branch depth into the crown. Diameter at breast height (DBH) had significant positive influences on the branch size; however, tree height (HT) produced negative influences on the branch size, i.e., larger DBH and smaller HT could lead to larger branch size. Model fitting and validation results confirmed that we should avoid developing over-complex models from the perspective of application. As for the branch diameter and length models in our study, addressing the stand and tree level effects as random component were quite reliable and accurate for predicting the branch growth process of Dahurian larch in northeastern China.

     

Allometric biomass,nutrient and carbon stock models for <Emphasis Type="Italic">Kandelia candel</Emphasis> of the Sundarbans,Bangladesh

Key message

Present study recommends DBH as independent variable of the derived allometric models and Biomass = a + b DBH ² has been selected for total above-ground biomass, nutrients and carbon stock.

Abstract

Kandelia candel (L.) Druce is a shrub to small tree of the Sundarbans mangrove forest of Bangladesh. The aim of the study was to derive the allometric models for estimating above-ground biomass, nutrient and carbon stock in K. candel. A total of eight linear models with 64 regression equations were tested to derive the allometric models for biomass of each part of plant; and nutrients and carbon stock in total above-ground biomass. The best fitted allometric models were selected by considering the values of R ², CV, R _mse, MS_error, S _a, S _b, F value, AICc and Furnival Index. The selected allometric models were Biomass = 0.014 DBH² + 0.03; √Biomass = 0.29 DBH ? 0.21; √Biomass = 0.66 √DBH ? 0.57; √Biomass = 1.19 √DBH ? 1.02; Biomass = 0.21 DBH² + 0.12 for leaves, branches, bark, stem without bark and total above-ground biomass, respectively. The selected allometric models for Nitrogen, Phosphorous, Potassium and Carbon stock in total above-ground biomass were N = 0.39 DBH² + 0.49, P = 0.77 DBH² + 0.14, K = 0.87 DBH² + 0.07 and C = 0.09 DBH² + 0.05, respectively. The derived allometric models have included DBH as a single independent variable, which may give quick and accurate estimation of the above-ground biomass, nutrient and carbon stock in this species. This information may also contribute to a broader study of nutrient cycling, nutrient budgeting and carbon sequestration of the studied forest.

     

Climate variability,tree increment patterns and ENSO-related carbon sequestration reduction of the tropical dry forest species <Emphasis Type="Italic">Loxopterygium huasango</Emphasis> of Southern Ecuador

Key message

Striking hydro-climatic differences of 2 years (wet; dry) dramatically control the increment pattern of L. huasango in varying extent, even causing a “growth collapse” during the La Niña drought 2010/2011.

Abstract

We present the first multi-year long time series of local climate data in the seasonally dry tropical forest in Southern Ecuador and related growth dynamics of Loxopterygium huasango, a deciduous tree species. Local climate was investigated by installing an automatically weather station in 2007 and the daily tree growth variability was measured with high-resolution point dendrometers. The climatic impact on growth behaviour was evaluated. Hydro-climatic variables, like precipitation and relative humidity, were the most important factors for controlling tree growth. Changes in rainwater input affected radial increment rates and daily amplitudes of stem diameter variations within the study period from 2009 to 2013. El Niño Southern Oscillation (ENSO) related variations of tropical Pacific Ocean sea surface temperatures influenced the trees’ increment rates. Average radial increments showed high inter-annual (up to 7.89 mm) and inter-individual (up to 3.88 mm) variations. Daily amplitudes of stem diameter variations differed strongly between the two extreme years 2009 (wet) and 2011 (dry). Contrary to 2009, the La Niña drought in 2011 caused a rapid reduction of the daily amplitudes, indicating a total cessation (‘growth collapse’) of stem increment under ENSO-related drought conditions and demonstrating the high impact of climatic extreme events on carbon sequestration of the dry tropical forest ecosystem.

     

Differential competitive ability between sexes in the dioecious Antennaria dioica (Asteraceae)

Background and Aims

Differences in competitive ability between the sexes of dioecious plants are expected as a result of allocation trade-offs associated with sex-differential reproductive costs. However, the available data on competitive ability in dioecious plants are scarce and contradictory. In this study sexual competition was evaluated using the dioecious plant Antennaria dioica in a common garden transplantation experiment.

Methods

Male and female plants were grown for 3 years either in isolation, or in competition with a plant of the same sex or the opposite sex. Flowering phenology, sexual and asexual reproduction, plant growth, nutrient content and arbuscular mycorrhizal colonization in the roots were assessed.

Key Results

Our results showed little evidence of sexual differences in competitive ability. Both sexes suffered similarly from competition, and competitive effects were manifested in some traits related to fitness but not in others. Survival was unaffected by competition, but competing plants reduced their vegetative growth and reproductive investment compared with non-competing plants. In addition, differences in sexual competitive ability were observed in relation to flowering frequency, an important life history trait not reported in previous studies.

Conclusions

The findings indicate that female and male A. dioica plants possess similar intersexual competitive abilities which may be related to the similar costs of reproduction between sexes in this species. Nevertheless, intrasexual competition is higher in females, giving support for asymmetric niche segregation between the sexes.     

Land-use change impact on mycorrhizal symbiosis in female and male plants of wild <Emphasis Type="Italic">Carica papaya</Emphasis> (Caricaceae)

It has been acknowledged that land-use change has negative effects on genetic diversity and sex ratio in dioecious species, but less attention has been paid on the influence that land-use change has on the biotic interactions, especially between dioecious species and arbuscular mycorrhizal (AM) fungi. AM mutualism involves reciprocal transfer of carbohydrates and mineral nutrients between the host plant’s roots and these fungi. Here, we report spatial and temporal variation in AM colonization in dioecious wild Carica papaya plants growing in sites with different land use intensity. We tagged, recorded the basal stem circumference and collected roots of reproductive female and male Carica papaya plants in three wild sites during dry and rainy seasons of western Mexico. We also collected soil samples in each site to conduct soil chemical analyses. The sexes of C. papaya did not show significant differences in the frequency (percentage of root colonized by intraradical fungal structures) and abundance (length of intraradical hyphae) of AM fungi but the higher AM colonization was observed during the dry season, and in the site with the lowest disturbance. There was no relationship between soil chemistry and AM colonization. Overall, our findings suggest that land-use intensity has a negative effect on AM colonization and we discuss the consequences of habitat loss for the reproductive female and male plants, the implications of decreasing AM colonization for wild Carica papaya plants an important species that provides a source of genetic variation for the C. papaya varieties.     

Growth partitioning within beech trees (<Emphasis Type="Italic">Fagus sylvatica</Emphasis> L.) varies in response to summer heat waves and related droughts

Key message

Beech growth variability and climate sensitivity are much higher in the crown top than in the bole. The most notable bole–crown discrepancies occurred in response to extreme climate conditions.

Abstract

To characterize growth partitioning within the tree and its responses to climate, we studied eight dominant beech trees (Fagus sylvatica L.) of a pure, even-aged 98-year-old stand in Belgium. We sampled ten disks along the stem from breast height to treetop and examined the inter-annual patterns of, and discrepancies between, ring-area and volume increments by performing detailed stem analysis and dendroecological investigations. Although the common inter-annual variation among all increment series was high, we observed increasing growth variability and climate sensitivity with height, leading to notable bole–crown discrepancies. Both the common inter-annual variation and bole–crown discrepancies were mainly driven by summer heat waves and related droughts of the previous year, and spring droughts of the current year. Despite these discrepancies, the radial growth at breast height can be considered a good estimate of the tree volume increment but not for the purpose of focusing on climatic effects of isolated years. Extreme climatic conditions increase the risk of inaccurate estimations. The results of the present study are discussed in relation to tree ecophysiology hypotheses.

     

Common allometric response of open-grown leader shoots to tree height in co-occurring deciduous broadleaved trees

Background and Aims

Morphology of crown shoots changes with tree height. The height of forest trees is usually correlated with the light environment and this makes it difficult to separate the effects of tree size and of light conditions on the morphological plasticity of crown shoots. This paper addresses the tree-height dependence of shoot traits under full-light conditions where a tree crown is not shaded by other crowns.

Methods

Focus is given to relationships between tree height and top-shoot traits, which include the shoot''s leaf-blades and non-leafy mass, its total leaf-blade area and the length and basal diameter of the shoot''s stem. We examine the allometric characteristics of open-grown current-year leader shoots at the tops of forest tree crowns up to 24 m high and quantify their responses to tree height in 13 co-occurring deciduous hardwood species in a cool-temperate forest in northern Japan.

Key Results

Dry mass allocated to leaf blades in a leader shoot increased with tree height in all 13 species. Specific leaf area decreased with tree height. Stem basal area was almost proportional to total leaf area in a leader shoot, where the proportionality constant did not depend on tree height, irrespective of species. Stem length for a given stem diameter decreased with tree height.

Conclusions

In the 13 species observed, height-dependent changes in allometry of leader shoots were convergent. This finding suggests that there is a common functional constraint in tree-height development. Under full-light conditions, leader shoots of tall trees naturally experience more severe water stress than those of short trees. We hypothesize that the height dependence of shoot allometry detected reflects an integrated response to height-associated water stress, which contributes to successful crown expansion and height gain.     

Understanding changes in black (Picea mariana) and white spruce (Picea glauca) foliage biomass and leaf area characteristics

Key message

Growth conditions related to inter-tree competition greatly influence black and white spruce foliage biomass and projected leaf area characteristics.

Abstract

Foliage characteristics such as biomass and area are important among other reasons because they can be related to tree growth. Despite their economic and ecologic importance, equations to characterize foliage biomass and projected area of black (Picea mariana (Miller) BSP) and white (Picea glauca (Moench) Voss) spruces are sparse. Total foliage biomass and projected leaf area, foliage biomass and leaf area density, and relative vertical distribution of black and white spruces foliage biomass and leaf area were modelled with linear and nonlinear mixed effect models. A total of 65 white spruces and 57 black spruces were destructively sampled at four different locations in Alberta, Québec, and Ontario, Canada. Our results show that for each species, total tree foliage biomass and projected leaf area is proportional to stem diameter, total height, and crown length. The addition of crown length in the equations improved the precision of the predictions of total foliage biomass for both species and diminishes greatly the site level random effect. An increase in DBH for black spruce and in the DBH to total height ratio for white spruce skewed the relative vertical foliage biomass distribution toward the base of the living crown. According to our results, growth conditions or tree development stage influence both foliage biomass and leaf area characteristics of black and white spruces. Our results emphasize the importance of inter-tree competition on foliage biomass characteristics.     

Deciduous and evergreen trees differ in juvenile biomass allometries because of differences in allocation to root storage

Background and Aims

Biomass partitioning for resource conservation might affect plant allometry, accounting for a substantial amount of unexplained variation in existing plant allometry models. One means of resource conservation is through direct allocation to storage in particular organs. In this study, storage allocation and biomass allometry of deciduous and evergreen tree species from seasonal environments were considered. It was expected that deciduous species would have greater allocation to storage in roots to support leaf regrowth in subsequent growing seasons, and consequently have lower scaling exponents for leaf to root and stem to root partitioning, than evergreen species. It was further expected that changes to root carbohydrate storage and biomass allometry under different soil nutrient supply conditions would be greater for deciduous species than for evergreen species.

Methods

Root carbohydrate storage and organ biomass allometries were compared for juveniles of 20 savanna tree species of different leaf habit (nine evergreen, 11 deciduous) grown in two nutrient treatments for periods of 5 and 20 weeks (total dry mass of individual plants ranged from 0·003 to 258·724 g).

Key Results

Deciduous species had greater root non-structural carbohydrate than evergreen species, and lower scaling exponents for leaf to root and stem to root partitioning than evergreen species. Across species, leaf to stem scaling was positively related, and stem to root scaling was negatively related to root carbohydrate concentration. Under lower nutrient supply, trees displayed increased partitioning to non-structural carbohydrate, and to roots and leaves over stems with increasing plant size, but this change did not differ between leaf habits.

Conclusions

Substantial unexplained variation in biomass allometry of woody species may be related to selection for resource conservation against environmental stresses, such as resource seasonality. Further differences in plant allometry could arise due to selection for different types of biomass allocation in response to different environmental stressors (e.g. fire vs. herbivory).     

Biomechanical constraints on tree architecture

Key message

Mechanical properties of wood constrain most conifers to an excurrent form and limit the width of tree crowns. Development of support tissue alters allometric relations during ontogeny.

Abstract

Biomechanical constraints on tree architecture are explored. Torque on a tree branch is a multiplicative function of mass and moment arm. As such, the need for support rises faster than branch length, which leads to increased taper as branch size increases. This violates assumptions of models, such as the pipe-model theory, for large trees and causes changing allometry with tree size or exposure. Thus, assumptions about optimal design for light capture, self-similarity, or optimal hydraulic architecture need to be modified to account for mechanical constraints and costs. In particular, it is argued that mechanical limitations of compression wood in conifers prevent members of this taxon from developing large branches. With decurrent form ruled out (for larger species), only a conical or excurrent form can develop. Wind is shown to be a major mortality risk for trees. Adaptations for wind include dynamic responses of wood properties and height. It is argued that an adaptation to wind could be the development of an open crown in larger trees to let the wind penetrate, thereby reducing wind-throw risk. It is thus argued that crown shape and branching may result not just from optimal light capture considerations but also from adaptation to and response to wind as well as from mechanical constraints. Results have implications for allometric theory, life history theory, and simulations of tree architecture.

     

<Emphasis Type="Italic">Microlicia veadeirana</Emphasis> (Melastomataceae,Microlicieae), a new species from the Chapada dos Veadeiros National Park,Brazil

Microlicia veadeirana, a new species found in the Chapada dos Veadeiros National Park, Goiás, is herein described and illustrated. Additionally, its conservation status, environmental preferences, and period of flowering and fruiting are provided. The novel species is morphologically similar to M. isostemon, M. consimilis, and M. cryptandra based on a set of characters such as general appearance of the stem, length of leaves, color of petals, stem orientation, and number of locules in the ovary. However, it is distinguished from these species by a series of characters, including 1-nerved leaves, with the margin not ciliate, a crown of trichomes at the apex of the hypanthium, the length of the connectives of the stamens, and urceolate capsules.     

Mangrove root: adaptations and ecological importance

Key message

This review gives a comprehensive overview of adaptations of mangrove root system to the adverse environmental conditions and summarizes the ecological importance of mangrove root to the ecosystem.

Abstract

In plants, the first line of defense against abiotic stress is in their roots. If the soil surrounding the plant root is healthy and biologically diverse, the plant will have a higher chance to survive in stressful conditions. Different plant species have unique adaptations when exposed to a variety of abiotic stress conditions. None of the responses are identical, even though plants have become adapted to the exact same environment. Mangrove plants have developed complex morphological, anatomical, physiological, and molecular adaptations allowing survival and success in their high-stress habitat. This review briefly depicts adaptive strategies of mangrove roots with respect to anatomy, physiology, biochemistry and also the major advances recently made at the genetic and genomic levels. Results drawn from the different studies on mangrove roots have further indicated that specific patterns of gene expression might contribute to adaptive evolution of mangroves under high salinity. We also review crucial ecological contributions provided by mangrove root communities to the ecosystem including marine fauna.

     

Development of branch,crown, and vertical distribution leaf area models for contrasting hardwood species in Maine,USA

Key message

Branch, crown vertical leaf area distribution models were developed for naturally regenerated hardwood species and planted hybrid poplar clones. Species-specific differences were found at all levels of investigation.

Abstract

Coexistence in mixed-species stands is strongly influenced by species differences in leaf area production and distribution. The majority of leaf area models in the literature are focused on conifer species, which have substantially different crown forms than hardwood species. Therefore, the goal of this investigation was to develop branch, crown, and vertical leaf area distribution models for various hardwood species that accounted for their greater crown complexity. A nonlinear model including branch diameter, branch tip height, and height to the start of the foliage was the best fit for branch leaf area. Branch leaf area ranged from 0.05 to 0.37 m² for Populus grandidentata and Betula populifolia for an averaged sized branch, respectively. The best fit model for crown leaf area was a nonlinear form accounting for stem diameter and crown length. Crown leaf area ranged from 3.26 to 9.85 m² for Populus tremuloides and Betula populifolia for an averaged sized tree, respectively. Vertical leaf area distribution was best fit by a right-truncated Weibull distribution and showed a peak in the middle third of the crown for most of species. In addition, leaf area production varied among four hybrid poplar clones in plantations, suggesting a strong genetic control over crown form. Overall, leaf area varied among species at all levels of investigation, suggesting that coexistence of hardwood saplings in this investigation was strongly influenced both by inherent species-specific leaf area production and vertical distribution.     

Sexual Dimorphism and Length–Weight Relationship of the Hairy Conger Eel <Emphasis Type="Italic">Bassanago albescens</Emphasis> (Anguilliformes: Congridae)

The present study reports the first reference on length-weight relationships (LWR) and sexual dimorphism for Bassanago albecens, caught as bycatch in the commercial fishery in the Argentine continental shelf. A total of 91 conger eels were examined. Female specimens (ranged from 371 to 661 mm total length—TL) have body length larger than males (from 396 to 537 mm TL), but the length-weight relationships allometry coefficient was 3.76 for both sexes. Three out of seven morphometric measurements differed between sexes, in particular head size characteristics. These biometric data and their relationships are relevant to the management and conservation of fish diversity and fisheries.     

Crown responses to neighbor density and species identity in a young mixed deciduous stand

Key message

Density was more important in shaping crown structure than neighbor species identity. Both species showed high crown plasticity at alternative levels, which may explain species coexistence in mixed broadleaved forests with functionally similar species.

Abstract

Understanding crown response to local competition is essential to predicting stand development in mixed stands. We analyzed data from an 8-year-old field experimental plantation mixing two species according to a crossed gradient of density and species proportion to quantify the effect of a broad range of local neighborhood conditions on the development of young trees at multiple crown levels. We used Fagus sylvatica and Acer pseudoplatanus, as two model deciduous species. They are considered functionally equivalent at the young stages, but with contrasting architectural patterns. For both species: (1) changes in density explained more of the variation on crown development than species proportion (2) much of the effect of competition was accounted for by variables at the stem level, while branch and leaf development within crowns were not directly altered by competition. Both species were able to modify their crowns at the stem level to compete with intra- and inter-specific neighbors: Acer and Fagus were taller with a highest proportion of Fagus as neighbors; Fagus displayed a lower crown base when the proportion of Fagus decreased, while Acer had a lower crown base when the proportion of Fagus around it increased. Both species showed common shapes in allometric relationships but contrasting responses at alternative crown levels. Acer exhibited broader intra-specific variation in its height–diameter relationship and in its crown length, while Fagus displayed higher individual variation of branch development and leaf area than Acer. This study demonstrates that differences in crown development strategy of each species in response to changes in local neighborhood conditions are an important factor in maintaining species coexistence in broadleaved forests and designing mixtures that persist over time.     

Food resource partitioning of the <Emphasis Type="Italic">Mustelus lunulatus</Emphasis> and <Emphasis Type="Italic">Mustelus henlei</Emphasis> (Elasmobranchii: Carcharhiniformes)

The feeding habits and trophic ecology of Mustelus lunulatus and Mustelus henlei in the central coast of the Colombian Pacific were evaluated and compared to determine whether there was trophic niche overlap or resource partitioning between these two sympatric shark species. A total of 59 prey items were identified and grouped into 10 taxonomic categories. Mustelus lunulatus fed in large proportion on Stomatopoda and Brachyura, whereas M. henlei fed almost exclusively on Teleostei. Dendrobranchiata, Cephalopoda, Anomura and Polychaeta complemented the diets of both species. There were significant differences in diet between the two species, and there was an ontogenetic diet shift in Mustelus lunulatus, with Stomatopoda being the main prey item of juveniles and Brachyura the main prey item of adults. Dietary overlap (by sex and size) was low between species, but it was high for each species, with significant overlap between juveniles and adults of M. lunulatus and M. henlei, and between males and females of M. henlei. There were differences in the trophic levels of the species, sexes and sizes. This study suggests there is food resource partitioning, and differing ecological function of the two Mustelus species in the food web of the study area.     

Morphological plasticity in mangrove trees: salinity-related changes in the allometry of Avicennia germinans

Key Message

Morphological plasticity helps plants to cope to environmental conditions. Allometric responses of the mangrove Avicennia germinans to increasing salinity are easily detectable when focusing on the top height trees.

Abstract

Several studies show that mangrove trees possess high species- and site-related trait allometry, suggesting large morphological plasticity that might be related to environmental conditions, but the causes of such variation are not clearly understood and systematic quantification is still missing. Both aspects are essential for a mechanistic understanding of the development and functioning of forests. We analyzed the role of salinity in the allometric relations of the mangrove Avicennia germinans, using: (1) the top height trees (trees with the largest diameters at breast height, which reflect forest properties at the maximum use of resources); (2) the slenderness coefficient (which indicates competition and environmental conditions); and (3) the crown to DBH ratio. These standard tools for forest scientists dealing with terrestrial forests are suitable to analyze the plastic responses of mangroves to salinity. First, the top height trees help to recognize structural forest properties that are not detectable when studying the whole stand. Second, we found that at salinities above 55 ‰, trees are less slender and develop wider crowns in relation to DBH than when growing at lower salinities. Our results suggest a significant change in allometric traits in relation to salinity, and reflect the plastic responses of tree traits in response to environmental variation. Understanding the plastic responses of plants to their environment can help to better model, predict, and manage forests in changing environments.