Figure 2 - uploaded by Peter Fransson
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The whole tree is described by the quantities: sapwood area below the main branches A s , stem height H s . Heartwood area at ground level A HW is determined by the accumulated A s and H s growth. The tree crown height H b is determined by A s .
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For trees in forests, striving for light is matter of life and death, either by growing taller towards brighter conditions or by expanding the crown to capture more of the available light. Here we present a mechanistic model for the development path of stem height and crown size, accounting for light capture and growth, as well as mortality risk. W...
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... crown height is assumed to relate to sapwood area (sapwood crosssectional area) through a power law relation ( Mäkelä 1997, Valentine andMäkelä 2005), and Sievänen (1992) found a power law relation as a result from an optimization study of height growth in open-growth trees. With these assumptions, all the biomass pools can be expressed in terms of two quantities: the crown size and the stem height (H s ; Figure 2). Because the crown size is determined by A s , we will use A s as a proxy for crown size. ...
Citations
... To address longer term effects and forest growth, the model can be extended with the capacity to predict carbon allocation to the different plant organs, such as branches, fine root, stem, and leaves. To this end, our model could be coupled with allocation models based on similar EEO principles (e.g., Franklin et al., 2012 andFransson et al., 2021). ...
Forest growth is strongly affected by climate and soil conditions and reliable modelling these responses are needed to project forest growth for future climate scenarios. Although the separate effects of water and nitrogen limitations are well known, understanding how trees manage their combined requirements remains a challenge. Here we address this challenge based on a new eco-physiological model that accounts for plasticity in stomatal conductance and leaf nitrogen concentration.
Based on an optimality principle, our model determines stomatal conductance and leaf nitrogen concentration by balancing C uptake maximization, hydraulic risk and cost of maintaining photosynthetic capacity.
We demonstrate the accuracy of the model predictions compared to weekly GPP estimates from eddy flux measurements and canopy transpiration in long-term fertilized and unfertilized Pinus sylvestris forest in northern Sweden. The model also explains the response to increased soil N availability as a consequence of reduced carbon cost of N uptake and reduced hydraulic conductance per leaf area (linked to increased leaf area per sapwood area).
The results suggest that leaves optimally coordinate N concentration and stomatal conductance both on short (weekly) time scales in response to weather conditions and on longer time scales in response to water and N availability in the soil.
... Once forest gaps are created through thinning, the seedlings and saplings of hardwood tree species rapidly develop [110][111][112]. Additionally, in the present work, a significant increase in forest stock volume after harvesting was observed, as harvesting reduces competition within the stand, opens space, and provides nutrients for forest growth [113][114][115][116][117]. ...
Researchers build growth models to predict the growth of forest stands and propose management measures to improve the overall quality of these stands. In this study, data collected from 91 sample plots from the eighth (2010) and ninth (2015) Chinese National Forest Inventories in Jiangxi Province were used to establish a transition-matrix growth model. Then, 12 potential equilibrium curves were set to guide forest management, and a transition-matrix growth model was used to predict stand growth in Jiangxi Province. In each 10-year management period, trees with diameters that exceeded the equilibrium curve were cut down. The results show that species diversity (H1), size diversity (H2), and basal area (B) have statistically significant influences on growth, mortality, and recruitment. Moreover, the high accuracy of the transition-matrix growth model is demonstrated. According to the simulation results, B = 35 m2/ha, the maximum diameter of retained trees Dmax = 45 cm and the adjacent diameter ratio q = 1.7 constitute the optimal equilibrium curve to guide forest management. The diameter distribution guided by the equilibrium curve is reverse J-shaped and is associated with significant increases in the hardwood stock volume and current annual growth. Under the guidance of the equilibrium curve, the forests in Jiangxi Province can be reasonably managed, produce more high-economic-value timber, and achieve a more stable species composition. This study will help maximize the ecological and economic benefits of forests and provide a reference for the realization of the sustainable development of forestry. Furthermore, the results can be used to improve the facility and accuracy of natural forest harvesting.
... Others have reported crown width models using diameter at breast height, crown base height, and height as predictor variables [4][5][6]. There have also been studies involving height and diameter models [7,8], tree size variables (diameter at breast height, height, basal area, and stem volume) as a function of age [9], and forest carbon accumulation [10]. Bivariate analysis investigates the relationship between a paired dataset of an individual tree or stand variable measurements, for example, the height-diameter relationships [11,12], the height and basal area models [13,14], and others [15,16]. ...
In forestry, growth functions form the basis of research and are widely used for the mathematical modeling of stand variables, e.g., tree or stand basal area, stand height, stand volume, site index, and many more. In this study, to estimate five-dimensional dependencies between tree diameter at breast height, potentially available area, height, crown area and crown base height, we used a normal copula approach whereby the growths of individual variables are described using a stochastic differential equation with mixed-effect parameters. The normal copula combines the marginal distributions of tree diameter at breast height, potentially available area, height, crown area, and crown base height into a joint multivariate probability distribution. Copula models have the advantage of being able to use collected longitudinal, multivariate, and discrete data for which the number of measurements of individual variables does not match. This study introduced a normalized multivariate interaction information measure based on differential entropy to assess the causality between tree size variables. In order to accurately and quantitatively assess the stochastic processes of the tree size variables’ growth and to provide a scientific basis for the formalization of models, an analysis method of the synergetic theory of information entropy has been proposed. Theoretical findings are illustrated using an uneven-aged, mixed-species empirical dataset of permanent experimental plots in Lithuania.
... Although individuals of C. candelabra in the rainforest and open maquis share the same AU, our results show that tree height, diameter and self-pruning intensity are significantly higher in the rainforest. It is widely known that trees growing in dense stands reach greater heights and diameters than in open areas due to the selective pressure for crown exposure to light (Horn, 1971;Iwasa, Cohen & Leon, 1985;Franklin et al., 2012;Fransson, Brännström & Franklin, 2021). Plasticity in plant architecture allows species to cope with environmental heterogeneity and to specialize for a given ecological niche (Delagrange et al., 2004;Chambel et al., 2005;Valladares, Sanchez-Gomez & Zavala, 2006;Gratani, 2014). ...
Plant architecture strongly influences plant growth habits, as it determines the arrangement, function and fate of meristems. How architecture could be involved in the monocarpic life history, i.e. dying after flowering, remains poorly investigated. Monocarpy is evident in some species since they are annual or because their single stem flowers apically. However, monocarpy in long-lived branched trees is rare and remains poorly understood. We aim to highlight the architectural features involved in the monocarpic strategy of Cerberiopsis candelabra, a rainforest tree endemic to New Caledonia. We conducted a comparative analysis of the genus, which comprises three species with different growth habits. Twenty plants of each species were studied at different ontogenic stages. We compared their developmental sequence and analysed their processes of growth, branching, flowering and reiteration. We identified a combination of traits that distinguish the species, and we found a syndrome of two architectural features that support the monocarpic strategy in C. candelabra: the synchronous flowering of all terminal meristems and the absence of delayed branching. Flowering in C. candelabra preferentially occurs when the complete architectural sequence is developed, but the plant never shows signs of senescence, suggesting that environmental stresses, such as wind disturbance, could be the main trigger for flowering. The architecture of C. candelabra is suggested to be the most derived in the genus.
... These kinds of gaps are important for forest regeneration and the sapling growth of light-demanding species [44,49]. It is difficult to measure the gaps formed higher up in the canopy, but these gaps are important for the higher growth of larger trees [26,44,67]. ...
The interest to assess the relationship between forest gap characteristics and topography features has been growing in the last decades. However, such an approach has not been studied in undisturbed mixed sessile oak-beech old-growth forests. Therefore, the present study carried out in one of the best-preserved sessile oak-beech old-growth forests in Europe, aims to assess the influence of topographic features (slope, altitude and aspect) on (i) some characteristics of canopies and expanded gaps (surface, diameter and perimeter) and (ii) the proportion of beech and sessile oak as bordering trees, gap fillers and gap makers. Through a complete gap survey on an area of 32 ha, 321 gaps were identified and mapped. The largest gaps and also the highest gap frequency (140) was found in the slope class (15.1-20°), while the gap frequency increased with altitude, with 99 gaps being recorded at 601-650 m a.s.l. The size and perimeter of the canopy and expanded gaps, as well as the number of gap makers, were negatively related to the slope and altitude. The expanded gap to canopy gap size ratio decreased with the slope and was positively related to the altitude, while a significant negative decrease in gap filler density with altitude was encountered. The sessile oak participation ratio as bordering trees forming the gap increased not only with the altitude but also with the slope. The topography plays an important role in the formation of gaps as well as in the characteristics of the future stand. This study provides valuable insights into the relationship between canopy gap characteristics and topography, which is useful information for forest owners that pursue the design of forest management toward nature-based solutions.
... Although individuals of C. candelabra in the rainforest and open maquis share the same AU, our results show that tree height, diameter and self-pruning intensity are significantly higher in the rainforest. It is widely known that trees growing in dense stands reach greater heights and diameters than in open areas due to the selective pressure for crown exposure to light (Horn, 1971;Iwasa, Cohen & Leon, 1985;Franklin et al., 2012;Fransson, Brännström & Franklin, 2021). Plasticity in plant architecture allows species to cope with environmental heterogeneity and to specialize for a given ecological niche (Delagrange et al., 2004;Chambel et al., 2005;Valladares, Sanchez-Gomez & Zavala, 2006;Gratani, 2014). ...
The genus Cerberiopsis endemic to New Caledonia includes three species of branched woody plants. C. candelabra is a monocarpic pioneer tree (that flowers only once before dying) emblematic of forests in the south of the main island. Monocarpy in trees is rare worldwide. This intriguing life strategy is known for fewer than thirty tree species. This study aims to compare the growth strategy of Cerberiopsis species through an architectural analysis and understand which life history traits is associated with monocarpy in Cerberiopsis candelabra. The architecture of twenty individuals of each species has been described in different ontogenical stages under various natural conditions.
Our results show that the architectural unit of all the species is based on three categories of axes: the trunk, the branches and the twigs. The construction of the three species varies mainly according to (i) the synchronism of terminal flowering within the axes of the crown, (ii) the ratio of elongation and node production between the trunk and the branches, (iii) the capacity of the twig to continue branch construction after their terminal flowering, leading to the establishment of mixed axes constructed by substitution. C. candelabra is mainly distinguished from sister species by its massive and synchronous flowering which concerns all axes categories, thus preventing the branches to continue their development from the twigs.
In most cases, all three species maintain this architectural unity throughout their lives. Nevertheless, for C. candelabra and C. neriifolia some branches acquire the characteristics of the trunk by immediate total reiteration.
Regardless to its development strategy, which may seem risky, C. candelabra is the most ubiquitous species capable of colonizing both forest and disturbed open environments. This study shows how the variation of simple architectural traits can not only generate phenotypic plasticity but also a diversity of life history strategies.
... The usage of a constant amount of resources as mentioned in Cuny et al. (2014) leads to relatively thinner cell walls on bigger cells and thus a negative effect of tree height on TB 2 . As tree height itself is influenced by various environmental conditions, especially competition, temperature, and water availability (Lines et al., 2012;Fransson et al., 2021), it can be assumed that a large part of the height effects that we found correspond to indirect effects of environmental conditions on xylem anatomical traits related to water transport. Regarding direct environmental effects, more complex patterns were found. ...
Treeline ecosystems are of great scientific interest to study the effects of limiting environmental conditions on tree growth. However, tree growth is multidimensional, with complex interactions between height and radial growth. In this study, we aimed to disentangle effects of height and climate on xylem anatomy of white spruce [Picea glauca (Moench) Voss] at three treeline sites in Alaska; i.e., one warm and drought-limited, and two cold, temperature-limited. To analyze general growth differences between trees from different sites, we used data on annual ring width, diameter at breast height (DBH), and tree height. A representative subset of the samples was used to investigate xylem anatomical traits. We then used linear mixed-effects models to estimate the effects of height and climatic variables on our study traits. Our study showed that xylem anatomical traits in white spruce can be directly and indirectly controlled by environmental conditions: hydraulic-related traits seem to be mainly influenced by tree height, especially in the earlywood. Thus, they are indirectly driven by environmental conditions, through the environment’s effects on tree height. Traits related to mechanical support show a direct response to environmental conditions, mainly temperature, especially in the latewood. These results highlight the importance of assessing tree growth in a multidimensional way by considering both direct and indirect effects of environmental forcing to better understand the complexity of tree growth responses to the environment.
Horizontal structure of natural plant communities attracted the attention of researchers for a long time, while the problem of horizontal structure of urban park plantations was not studied sufficiently. Species richness of different tiers of park plantation in the large industrial city of Dnipro (Ukraine) was revealed in this study. Also features of variation in the structure of plant communities at different spatial levels were revealed, the influence of park plantation canopy on the understory and herbaceous layer of the park. There were 30 plant species in the tree layer of the park plantation. The most common species were Robinia pseudoacacia L., Acer platanoides L., A. negundo L., Gleditsia triacanthos L., Aesculus hippocastanum L., Populus carolinensis Moench. The variance-to-mean ratio revealed that 13 tree species were randomly distributed throughout the park, and 14 species were aggregated. The number of occurrences of a given tree species per site and variance-to-mean ratio were positively correlated. The numerous tree species showed a tendency of aggregated distribution within the park. Sixteen plant species were found in the understory. Among them, the most abundant species were Acer platanoides L., A. negundo L., A. pseudoplatanus L., Sambucus nigra L., Robinia pseudoacacia L. Eight species were found to be randomly distributed over the park area, and eight species showed an aggregate distribution. The number of species encountered in the understory and variance-to-mean ratio were positively correlated. In the herbaceous stand, 99 plant species were found, of which Chelidonium majus L., Viola odorata L., Impatiens parviflora DC., Parthenocissus quinquefolia (L.) Planch., Geum urbanum L. predominated. The variance-to-mean ratio of all species was significantly less than unity, indicating regular spatial distribution. The values of alpha- and gamma-diversity of the plant community in separate layers are very different. The highest gamma diversity was found for the herbaceous stand, while the diversity of the tree stand and understory was significantly lower. Alpha biodiversity of the tree stand and the understory did not practically differ. Beta diversity values between the layers are very close, and beta diversity is practically equal for tree stand and herbaceous layer. Thus, we can assume that the mechanisms of species turnover for the plant communities of different layers are determined by the common causes. The spatial broad-scale component was able to explain 8.2% of community variation, the medium-scale component was able to explain 4.2% of community variation, and the fine-scale component was able to explain 0.7% of community variation. The understory is the most sensitive to the environmental factors, the herbaceous stand is somewhat less sensitive, and the tree stand is the least sensitive to the environmental factors. The environmental factors in this study are represented by a set of variables. The spatial variation of the stand is predominantly influenced by the factors of trophicity and moisture of the edaphotope. These same factors also act on the herbaceous stand and understory, but along with them are included the environmental variables, which are determined by the architectonics of the crown space and thus the light regime, which is regulated by the tree stand. It is important to note that the variation of the communities of the different layers of the park plantation is subject to spatial patterns. The herbaceous and understory variation is more spatially structured than the tree stand variation. The spatial patterns can arise as a result of the influence of spatially structured environmental factors and as a result of factors of a neutral nature. The latter aspect of variation is best described by the pure spatial component of community variation.
Sugar, acting as a signal, can regulate the production of some chemical substance during plant defense responses. However, the molecular basis and regulatory mechanisms of sugar in poplar and other forest trees are still unclear. Sorbitol is a sugar-signaling molecule associated with plant defense. In this study, the pathogen-infested status of poplar was alleviated after exogenous feeding of 50 mM sorbitol. We sequenced and analyzed the transcriptome of poplar leaves before and after inoculation. The results showed that the genes PR1, WRKY, ceramide kinases (CERK) and so on responded to sorbitol feeding and pathogen infestation. We screened for genes related to disease resistance such as PsWRKY25 and PsCERK1 and found that significant disease spots occurred on day six of strep throat infestation. Under sorbitol feeding conditions, the appearance of spots was delayed after the pathogen inoculation. Due to the overexpression of PsWRKY25, the overexpression of PsCERK1 triggered the defense response in poplar. This was also confirmed by PsWRKY25 overexpression experiments. These findings present new insights into the influence of sorbitol on Populus simonii Carr. disease resistance. These results emphasize the value of molecular phenotypes in predicting physiological changes.
