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Podocarps Phyllocladus hypophyllus in Papua New Guinea (top) and Podocarpus dispermis in tropical northern Australia (bottom). Both compete successfully with broad-leaf angiosperms in the understories of tropical rain forests, and both have divergent mechanisms for leaf and shoot flattening that lead to the production of broad photosynthetic structures reminiscent of angiosperm leaves.
Source publication
Angiosperm radiation in the Cretaceous is thought to have profoundly diminished the success of the conifers, the other major woody plant group present at the time. However, today the conifers persist and often thrive despite their supposed inferiority in vegetative and reproductive function. By exploring this apparent conflict for global tree domin...
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Context 1
... most striking contrast between Pinaceae and Podo- carpaceae emerges in the tropics, where podocarp diversity reaches a maximum and can occur anywhere from sea level up to the tree line. Their abundance in tropical regions means that podocarps compete directly with angiosperms in tropical rain forests ( fig. 2), and there is strong evidence that a history of competition with broad-leaf angiosperms has had a major impact on the adaptive morphology and function of podo- carps. Reconstructions of the morphological evolution of podocarp shoots show that, coincident with the angiosperm radiation of the Late Cretaceous-Early Cenozoic period, there ...
Context 2
... with the development of water-conducting tracheids lying outside the midrib xylem that provide radial water transport from the midrib to the leaf margin (Griffith 1957;Brodribb and Holbrook 2005). This efficient alterna- tive to the angiosperm reticulate-vein leaf enables single- veined podocarp ''needles'' to achieve widths of >30 mm ( fig. 2), which greatly enhances the efficiency of light harvest- ing and shade tolerance in these topical podocarps . During angiosperm diversification, the rate of speciation of imbricate podocarp species with lower light- use efficiency declined ( Biffin et al. 2012), and this supports the idea that shoot flattening in podocarps was a ...
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Citations
... Review of Palaeobotany and Palynology xxx (xxxx) 105142 transition to significant colder winters with a still high CO 2atm setting might have increased the competitiveness and favored the expansion of conifers in South America. In addition, vegetation changes towards less dense canopy physiognomies due to climate stresses could have also benefited the slow growing podocarps (i.e., Podocarpidites and Dacrydiumites) in the competition for light (Brodribb et al., 2012). From the Eocene to the Oligocene, a decreasing trend in annual precipitation of ca. ...
... Therefore, the gap with the embolism vulnerability between branches and roots will gradually widen, thus resulting in the increase of P 50 root-branch along environmental aridity gradients. Under water-limited conditions, tolerating drought stress while maintaining hydraulic function requires modification of hydraulic architecture, including the increased number of narrow conduits (Brodribb et al. 2012;Yao et al. 2021). However, plants in humid habitats tend to grow taller, which requires more water transporting to the top of crowns to sustain transpiration and photosynthesis (Koch et al. 2004;Chin et al. 2022). ...
The vulnerability of plant xylem to embolism can be described as the water potential at which xylem conductivity is lost by 50% (P50). According to the traditional hypothesis of hydraulic vulnerability segmentation, the difference in vulnerability to embolism between branches and roots is positive (P50 root−branch > 0). It is not clear whether this occurs broadly across species or how segmentation might vary across aridity gradients. We compiled hydraulic and anatomical datasets from branches and roots across 104 woody species (including new measurements from 10 species) in four biomes to investigate the relationships between P50 root–branch and environmental factors associated with aridity. We found a positive P50 root–branch relationship across species, and evidence that P50 root–branch increases with aridity. Branch xylem hydraulic conductivity transitioned from more efficient (e.g., wider conduit, higher hydraulic conductivity) to safer (e.g., narrower conduit, more negative P50) in response to the increase of aridity, while root xylem hydraulic conductivity remained unchanged across aridity gradients. Our results demonstrate that the hydraulic vulnerability difference between branches and roots is more positive in species from arid regions, largely driven by modifications to branch traits.
... The stress tradeoff hypothesis states that interspecific differences in competitiveness and climatic stress tolerance play a major role in maintaining species distributions across regions and continents (Louthan et al. 2015). This hypothesis has been invoked to explain how functional differences among species, especially in wood anatomy, generate biogeographic patterns in deciduous angiosperms and evergreen conifers (Bond 1989, Brodribb et al. 2012. Whereas conifer xylem consists of a homogeneous matrix of tracheids (slim water-conducting cells), angiosperm wood contains evolutionarily younger vessels (wider water-conducting conduits). ...
Basic ecological theory suggests that a tradeoff between competitiveness and stress tolerance dictates species range limits at regional extents. However, empirical support for this key theory remains deficient because the necessary spatial and temporal coverage and scalability of field observations has rarely been achieved. We harnessed an extensive dendroecological network (> 22 000 tree‐ring samples from 816 forest inventory plots) to disentangle competition‐limited from climate‐limited growth in both overstory and understory trees. Growth synchrony among trees thereby served as an integral metric of climate sensitivity, an approach that we justify in supplementary analyses of growth responses to temperature, precipitation, and the standardized precipitation‐evapotranspiration index. Sampling plots were arranged along elevational climate and vegetation gradients throughout the Carpathian Mountains, ranging from mixed‐species lowland forests to coniferous forests at high elevations. With mixed‐effect modelling, we also identified non‐climatic factors (stand characteristics, species diversity, and disturbance history) that modulate spatial patterns in the growth rate and synchrony of European beech Fagus sylvatica and Norway spruce Picea abies. Beech exhibited reduced growth and increased climate sensitivity towards higher elevations but performed better when species diversity was higher. The growth of spruce increased towards its lower range boundary, but understory cohorts grew poorly under interspecific competition. Overall, climate sensitivity was lower in more productive stands with benign climatic conditions and in recently disturbed sites with reduced stand density. These contrasting performances at mid‐elevations where the two species overlap (900–1300 m a.s.l.) reflect their evolutionary history, which enables them to be competitive (beech) or cold‐stress tolerant (spruce). This history will affect interactions between the two species under climate warming and shape macroecological patterns in the Carpathian ecoregion and likely other parts of Europe. Our findings point to a growing advantage of competitively stronger species in montane and subalpine vegetation zones.
... between species richness and total abundance can vary between taxonomic or functional groups (e.g. Bock et al., 2007), our specimen-, or abundance-, based results do seem to complement the fact that there are far fewer BR species than WR (Gilbertson, 1980;Gilbertson & Ryvarden, 1986;Ryvarden & Gilbertson, 1993) and fewer conifer species than hardwood (Brodribb et al., 2012). Note that specimen-based BR proportion estimates, calculated here, should provide a more accurate assessment of global significance compared with species-based proportion estimates (6%; Gilbertson, 1980), and the greater values found for specimen-based proportions suggest that BR may play a greater role in global wood decay than once thought. ...
... The tree data from these regions with limited fungal data, which are predominantly tropical, show hardwood domination and because these areas represent a large portion of the world's forested land area, it is likely that our analysis overestimated the global average for BR proportion, assuming the correlation we found between decay mode and tree type holds true for the tropics; however, the vast boreal forests in Russia, and to some extent those in Canada and Alaska as well, were largely unrepresented in our dataset and may counteract, at least partially, any overestimation due to missing tropical data. Note that this missing boreal data may also explain why calculated conifer proportions did not exceed 52%, despite the well-known dominance of conifers in boreal zones (Brodribb et al., 2012). ...
Unlike ‘white rot’ (WR) wood‐decomposing fungi that remove lignin to access cellulosic sugars, ‘brown rot’ (BR) fungi selectively extract sugars and leave lignin behind. The relative frequency and distribution of these fungal types (decay modes) have not been thoroughly assessed at a global scale; thus, the fate of one‐third of Earth's aboveground carbon, wood lignin, remains unclear.
Using c. 1.5 million fungal sporocarp and c. 30 million tree records from publicly accessible databases, we mapped and compared decay mode and tree type (conifer vs angiosperm) distributions. Additionally, we mined fungal record metadata to assess substrate specificity per decay mode.
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Fungal decay mode distributions can be explained by tree type and, more importantly, tree species distributions, which our data suggest is due to strong substrate specificities.
... Thus, gymnosperms as a group of plants have probably been subjected to more intense phenomena of recent convergent and divergent evolution diminishing the signal of long-time evolution (phylogenetic signal) in explaining wood density variation among species. Therefore, gymnosperms could compete with success in situ whereas angiosperms are unable to realize their maximum growth potential because of environmental limitations on photosynthesis and growth (Bond, 1989;Brodribb et al., 2012). ...
The effect of evolutionary history on wood density variation may play an important role in shaping variation in wood density, but this has largely not been tested. Using a comprehensive global dataset including 27,297 measurements of wood density from 2621 tree species worldwide, we test the hypothesis that the legacy of evolutionary history plays an important role in driving the variation of wood density among tree species. We assessed phylogenetic signal in different taxonomic (e.g., angiosperms and gymnosperms) and ecological (e.g., tropical, temperate, and boreal) groups of tree species, explored the biogeographical and phylogenetic patterns of wood density, and quantified the relative importance of current environmental factors (e.g., climatic and soil variables) and evolutionary history (i.e., phylogenetic relatedness among species and lineages) in driving global wood density variation. We found that wood density displayed a significant phylogenetic signal. Wood density differed among different biomes and climatic zones, with higher mean values of wood density in relatively drier regions (highest in subtropical desert). Our study revealed that at a global scale, for angiosperms and gymnosperms combined, phylogeny and species (representing the variance explained by taxonomy and not direct explained by long-term evolution process) explained 84.3% and 7.7% of total wood density variation, respectively, whereas current environment explained 2.7% of total wood density variation when phylogeny and species were taken into account. When angiosperms and gymnosperms were considered separately, the three proportions of explained variation are, respectively, 84.2%, 7.5% and 6.7% for angiosperms, and 45.7%, 21.3% and 18.6% for gymnosperms. Our study shows that evolutionary history outpaced current environmental factors in shaping global variation in wood density.
... During their long-life times, they are exposed to different biotic and abiotic stresses. Their capacity has been attributed to decay resistance in the wood and the presence of resin canals, which protects them against severe conditions (Brodribb et al., 2012). ...
... Cupressaceae has generated a fascinating comparison with two other families because it reveals a panglobal distribution. Further, it can also survive in very dry areas, where the efficient capacity of water uptake in angiosperms is restricted by ordinary exposure to intense water stress (Brodribb et al., 2012). ...
Juniper species contain abundant compounds that are used in the medicine, cosmetic, and wood industry. Furthermore, these components protect the genus against herbivores, pathogens and detrimental abiotic conditions. Stains and specific reagents can be used individually or simultaneously to mark cell shape, arrangement and the material they are made from. Microchemical analyses using specific reagents and stains under light microscopy are helpful for the characterization of chemical compounds present in plant tissues. The autofluorescence of endogenous fluorophores is used to enable their localization in plant cells and tissues. This paper aims to investigate the cytochemical and histochemical traits of the shoots (leaves and stems) and female cones (berries) of Juniperus seravschanica . Light and florescent microscopy techniques were used to analyze the cytology and localization of different compounds for the first time. Microscopy‐based histochemical analyses revealed various products in terms of composition and distribution among the shoots and female cones. These specific compounds contained lignin, tannins, polysaccharides, starch, phenolic compounds, chlorophyll, terpenoids, neutral lipids, and proteins. However, the anatomical position of each metabolite and its concentration was different among leaf, stem, and female cone. Phenolic cells of young cones were differentiated into sclereid cells during development. The density of phenolic cells, sclereid cells, and resin glans was higher in female cones than leaves and stems. The high levels of various components can be related to high resistance of the species against biotic and abiotic stresses, confirm its industrial, pharmaceutical and agricultural applications and is useful for identification of diagnostic taxonomic traits.
Research Highlights
Microscopical and histochemical analyses showed various compounds in J. seravschanica
The phenolic cells differentiated to sclereid cells during development
High levels of idioblasts and various compounds show its high resistance and medicinal role
... Conifers have xylem composed entirely of tracheids, while angiosperms have both tracheids and wide vessels. Although the presence of wide vessels allows for higher water transport capacity in angiosperms, it also results in a smaller safety margin when it comes to xylem pressures [88]. The probable reason for the lack of response to waterlogging stress is that the total precipitation in the third year in C was 1565 mm, which was higher than that in the first and second years; therefore, C was under mild waterlogging conditions [53]. ...
Waterlogging induces oxidative damage by accumulation of reactive oxygen species due to stomatal closure. Plants alter their physiological and molecular mechanisms to reduce and adapt to oxidative stress. This mechanism of adaptation to stress, known as hardening, can support future stress tolerance. Pinus densiflora seedlings were grown under waterlogging treatment for three years and then transplanted to another site to identify the waterlogging hardening effect on transplanting. Transcriptome analysis was conducted before and after transplanting, and physiological factors were measured after transplanting. After transplanting, wounding stress is the main cause of transplant stress, and 13 genes related to phenylpropanoid were upregulated for the recovery of wounded roots in waterlogged hardened seedlings. The leaf starch and soluble sugar content of the waterlogged hardened seedlings were 50.3% and 40.5% lower due to the formation of cell walls. However, auxin-related genes were downregulated in waterlogging hardened seedlings, resulting in a lower tendency for height growth in hardened waterlogged seedlings. Waterlogging hardening mitigated transplant stress by wounding more than non-hardening, whereas waterlogging hardening may negatively affect seedling height. Our study provides evidence for the hardening effect of long-term waterlogging on transplanted P. densiflora seedlings.
... Leaf life span influences photosynthesis and defensive traits (Matsuki and Koike 2006), leaf traits vary in response to variation in resource availability (Zhang et al. 2020), and leaf life span and photosynthesis parameters are linked (Vasfilov 2016). There are evidences to indicate that competition between conifers and angiosperm trees is affected by leaf characters (Brodribb et al. 2012), and adaptive significance of evergreen vs deciduous leaves (Givnish 2002) is related to several other plant traits and habitat condition. Leaf traits are associated with several ecosystem characters (Luo et al. 2005). ...
The topographic heterogeneity of the Himalayas leads to a mosaic of growing conditions which limits the utility of traditional systems of forest classification. A leaf phenology based classification is suggested as an alternate to help understand patterns of Himalayan forests. Leaf traits such as longevity, time of new flush and shedding and type of leaf, are linked with ecosystem processes and show more consistent patterns across Himalayan landscapes. While low temperatures and a short growing season limit growth at extremely high altitudes and near the timberline, drought stress is the variable that most influences forest structure in the majority of Himalayan forests. Precipitation occurs through two major weather systems: the monsoon which is the dominant climate system for much of the Himalayas, and the westerlies, which are active in the Western part and northern fringes of the Himalayas. The pre-monsoon dry season is the most important in determining forest type and leaf phenology. Based on these differing weather systems and rainfall deficits, the Himalayas can be broadly divided into five categories based on type of leaf and when it is shed. Trees which leaf out in the pre-monsoon period, with approximately one year leaf life span and almost simultaneous leaf fall (e1 type), can best benefit from the monsoonal climate. This type lies on a continuum between pre-monsoon deciduous (dp) and evergreen species with multiple leaf flush (e2). At higher altitudes and dryer sites conifers (e3 type) dominate while winter deciduous (dw) are most abundant near the treeline. The Himalayas lie at the confluence of the Palearctic and Indo-malayan biogeographic zones and the influence of these different vegetation types is evident. Despite the presence of a floristic base and diversity of deciduous species Himalayan forests are largely evergreen as climatic conditions favour this evergreen strategy.
... During their long-life times, they are exposed to different biotic and abiotic stresses. Their capacity has been attributed to decay resistance in the wood and the presence of resin canals, which protects them against severe conditions (Brodribb et al., 2012). ...
... Cupressaceae has generated a fascinating comparison with two other families because it reveals a panglobal distribution. Further, it can also survive in very dry areas, where the efficient capacity of water uptake in angiosperms is restricted by ordinary exposure to intense water stress (Brodribb et al., 2012). ...
Conifers are long-lived species that cope with multiple abiotic and biotic stresses. To defend themselves, they have evolved a wide array of morphological, anatomical and chemical traits. Morpho-anatomical traits of Juniperus seravschanica, particularly in male and female cones, have not been studied. Thus, in this survey, these structures were studied to investigate the adaptative traits. The species is frost- and drought-tolerant and grows at a 2200-3800 m altitude on normal, chalky, calcareous, rocky, and mountainous outcrops with other species or as pure patches. The seedlings and young plant leaves were small and needle-like, while the main leaves of adult plants were scale-like and overlapping; there was a conspicuous resin gland (duct) in the outer surface of scale-like leaves secreting a white and sticky resinous substance, particularly in damaged leaves. The epidermis was thick with thicker outer walls and sunken stomata; the hypodermis showed 1-3 layers of lignified cells with a narrow lumen. The palisade parenchyma was observed on both sides. Sclereids, phenolic- and starchy cells were observed in leaves, particularly scale-like ones. Male cones were small with overlapping and decussate scales, in which resin glands (ducts) and phenolic cells were also observed. Similarly, female cones had overlapping and decussate scales converting to fleshy, berry-like, and bluish appearance during development. They revealed the presence of several resin glands, a thick epidermis, phenolic cells in young cones, and numerous sclereid cells in mature cones. Tracheids were narrow in leaves and cones. The features such as high sclerophylly, resin glands, phenolic cells, narrow tracheids, sunken stomata, increasing thickness of the epidermis, cuticle, hypodermis, as well as the presence of palisade parenchyma on both sides enable the species to survive in hard conditions.
... Evergreen species compared to deciduous species are able to withstand anthropogenic disturbance of the ecosystem due to some superior plant traits, but they are also able to tolerate low disturbance regimes (Greenwood et al., 2017;Karim et al., 2023). A study on cavity resistance and nutrient-use efficiency of evergreen species suggests that this species is resistant to disturbed habitats (Brodribb et al., 2012) although recent studies show that cavity resistance and nutrient-use efficiency do not represent the whole hydraulic strategy of a plant (Anderegg, 2015;Gleason et al., 2016). On the other hand, deciduous species perform better than evergreen species under ideal resource conditions (Berendse and Scheffer, 2009). ...
The relationship between ecosystem functions and plant functional traits has been well documented and is considered to be one of the most vital topics in ecology. However, the correlation between anthropogenic disturbance and tree functional trait diversity remains largely unclear. The present study investigates the role of anthropogenic disturbance on selected tree functional traits in Ratargul Swamp Forest (RSF) – the only remnant tropical freshwater swamp forest ecosystem in Bangladesh. We established 50 plots and collected six plant traits, i.e., tree height, specific leaf area (SLA), wood density (WD), leaf dry matter content (LDMC), seed mass, and bark thickness. A two-way analysis of variance (ANOVA) was carried out to test the interaction between plant functional traits and anthropogenic disturbance in RSF. Our study found that anthropogenic disturbance has a significant (p< 0.05) influence on deciduous swamp forest tree species’ functional traits but none on evergreen tree species’ functional traits. For deciduous trees, disturbance has a significant positive effect on CWM.SLA (p< 0.05) and CWM.Height (p< 0.05) and a negative impact on CWM.Bark-thickness and CWM.Seed-mass (p< 0.05). There were no significant effects of disturbance on CWM.WD and CWM.LDMC. We believe the present study will contribute toward improving our understanding of the effect of disturbances on tree functional trait diversity in tropical human-dominated landscapes where anthropogenic pressure is increasing at an unprecedented rate. It will also function as an essential conservation for related decision-making of Ratargul Swamp Forest in northeastern Bangladesh and elsewhere in the tropics with a similar context.
