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A 5-m-tall Weinmannia racemosa sapling which established epiphytically on the trunk of a Dicksonia squarrosa tree fern in an alluvial forest in southern New Zealand. Mature trees of this species are often observed to have a tree fern trunk buried in their trunks, indicating their epiphytic origins
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Seedling regeneration on forest floors is often impaired by competition with established plants. In some lowland temperate rain forests, tree fern trunks provide safe sites on which tree species establish, and grow large enough to take root in the ground and persist. Here we explore the competitive and facilitative effects of two tree fern species,...
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Context 1
... on tree fern trunks. It seems that tree ferns facilitate regen- eration of certain species as many seedlings are observed to establish as epiphytes on tree fern trunks, and then grow large enough to take root and persist independently of the tree fern (Pope 1926;Wardle 1963;Veblen and Stewart 1980;Newton and Healey 1989;Coomes et al. 2005; Fig. ...
Context 2
... (Takahashi 1997). Here we show the facilitative role that tree fern trunks play in the establishment of seedlings in nutrient-rich forests. On the Xoor of temperate rain forests establishment sites are scarce, and standing tree fern trunks provide important opportunities for establishment (Wardle 1963;Veblen and Stewart 1980;Coomes et al. 2005; Fig. 1). Epiphytic regeneration on tree fern trunks has been described in many forests, in Australia (Ashton 2000), Jamaica ( Newton and Healey 1989), and New Zealand (Pope 1926; Coomes et al. 2005), but this is the Wrst study to examine epiphytic regeneration in terms of facilitation. Recent papers have emphasized the importance of seed size ...
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Citations
... The advantage of suckering may be more apparent after periodic dieback of bamboos increases light availability, when carbon subsidies from parental trees give suckers advantages in growth and survival over newly-recruited seedlings (González et al., 2002). The dearth of regeneration in Chusquea thickets thus contrasts with the frequent epiphytic establishment of small-seeded tree and shrub species in New Zealand tree-fern groves (Beveridge, 1973;Gaxiola et al., 2008). Persistent bamboo thickets have also been reported to suppress tree regeneration in many tropical and subtropical forests (Royo and Carson, 2006). ...
... Some other tree fern species retain senescent leaves, forming a "skirt" that surrounds the main stem (e.g., Alsophila smithii [Hook.fil.] R. M. Tryon), a trait suggested to either protect against colonization by epiphytes (Gaxiola et al., 2008;Page & Brownsey, 1986) or against frost damage in southern temperate taxa (Brock & Burns, 2021). However, no other tree ferns have been reported to produce adventitious roots from leaf vascular bundles. ...
... Tree fern communities are of great importance in the structure and composition of the forest [26], in which they are frequently a dominant component, with a distribution along wide ranges of elevation within which they contribute an extraordinary diversity and a considerable level of endemism [27]. In addition, tree ferns are ecologically important because their role in nutrient cycling, control of ground-level irradiance and early succession as pioneer species capable of occupying forest gaps or edges [28,29], especially during forest regeneration events as a result of canopy disturbance phenomena [29,30], also facilitating epiphytic regeneration of tree species that inhabit their trunks [30,31]. ...
Knowing how species and communities respond to environmental change is fundamental in the context of climate change. The search for patterns of abundance and phenotypic variation along altitudinal gradients can provide evidence on adaptive limits. We evaluated the species abundance and the variation in morphometric and stomatal characters in five tree ferns species ( Cyathea fulva , C . divergens , C . myosuroides , Alsophila firma and Gymnosphaera salvinii ) distributed along an elevation gradient in a well-preserved Mexican cloud forest. Variation at the community and species level was assessed using exploratory and multivariate data analysis methods. We wanted to explore if the species abundance is environmentally determined, to determine the degree of variation along the elevation gradient, to test for differences between zones and associations with elevation, humidity and soil nutrients, and to assess contribution of the intra- and interspecific variation to the community response to elevation and soil nutrients. The studied fern community showed strong species turnover along the elevation gradient, with some influence of soil nutrient concentration, supporting environmental determinism. All measured characters displayed variation along the gradient. Stomatal characters (size and density) had significantly less variation than morphometric characters (trunk diameter, stipe length and blade length), but stomatal density also shows interesting intraspecific patterns. In general, patterns within the fern community suggest a strong influence of species identity, especially of species inhabiting the lower edge of the cloud forest, which showed the clearest morphometric and stomatal patterns, associated to contrasting environments rather than to changes in elevation. The coincidence between morphometric and stomatal patterns in this area suggest hydraulic adjustments in response to contrasting environments. Our results provide evidence that tree ferns species respond to environmental changes through adjustments of morphometric plasticity and stomatal density, which is relevant to predict possible responses to variation in environmental conditions resulting from climate change.
... The studies that evaluated the growth of podocarps in different habitats lead to the conclusion that podocarp growth is slow compared to other conifers and to angiosperms (e.g., in lowland cool temperate forest, the growth rate is half that of angiosperms [148], and in subalpine shrublands, podocarps grow more slowly than several angiosperm species [149]. In the nutrient-rich soil of southern New Zealand, even tree ferns grow faster than podocarps [150,151]. ...
Among conifer families, Podocarpaceae is the second largest, with amazing diversity and functional traits, and it is the dominant Southern Hemisphere conifer family. However, comprehensive studies on diversity, distribution, systematic and ecophysiological aspects of the Podocarpaceae are sparse. We aim to outline and evaluate the current and past diversity, distribution, systematics, ecophysiological adaptations, endemism, and conservation status of podocarps. We analyzed data on the diversity and distribution of living and extinct macrofossil taxa and combined it with genetic data to reconstruct an updated phylogeny and understand historical biogeography. Podocarpaceae today contains 20 genera and approximately 219 taxa (201 species, 2 subspecies, 14 varieties and 2 hybrids) placed in three clades, plus a paraphyletic group/grade of four distinct genera. Macrofossil records show the presence of more than 100 podocarp taxa globally, dominantly from the Eocene–Miocene. Australasia (New Caledonia, Tasmania, New Zealand, and Malesia) is the hotspot of living podocarps diversity. Podocarps also show remarkable adaptations from broad to scale leaves, fleshy seed cones, animal dispersal, shrubs to large trees, from lowland to alpine regions and rheophyte to a parasite (including the only parasitic gymnosperm—Parasitaxus) and a complex pattern of seed and leaf functional trait evolution.
... Hemiepiphytes are plants that germinate epiphytically but establish root contact with the ground in a later ontogenetic stage (for a complete terminology of structurally dependent plants, see Zotz [2016]). Terrestrial shrub and tree species that occasionally show such growth are thus accidental or facultative hemiepiphytes (Coomes et al., 2005;Corrêa & Fischer, 2017;Dawes & Burns, 2020;Gaxiola et al., 2008;Newton & Healey, 1989;Winoto-Lewin & Kirkpatrick, 2020). ...
... Therefore, cavities or crotches with arboreal soil are another commonly occupied microhabitat in tree crowns (Figure 5d,f,h) (Alvim et al., 2021;Sillett & Bailey, 2003;Sillett & Van Pelt, 2007), representing small ecosystems with trophic networks and internal nutrient cycles, where vascular and nonvascular plants build up biomass that is decomposed later on by a diverse macro-, meso-, and microfauna. In contrast, twigs, branches, and stems with bare bark are only rarely occupied by accidental epiphytes, most likely because the majority of the ground-inhabiting species of moderately moist forests do not tolerate the abiotic conditions in these microhabitats and because it is probably more difficult to attach and establish on these surfaces (Gaxiola et al., 2008;Hoeber et al., 2019). However, in rather dry and open habitats, drought-tolerant terrestrial species might also occupy canopy sites without abundant bryophytes or arboreal soil (Holmboe, 1914;Mai et al., 2019). ...
... These illustrative cases are comparable to accidental epiphytism in the evolutionary scenario of Tietze (1906) and Pittendrigh (1948) discussed in what follows. Apart from structurally distinct trees with secondary growth and complex crowns, accidental epiphytes can also be frequently observed in the leaf sheaths of palms ( Figure 5a) (Alguacil et al., 2019;Gonçalves et al., 2020) or on tree ferns (Gaxiola et al., 2008;Winoto-Lewin & Kirkpatrick, 2020). Even though suitable epiphytic microhabitats are diverse, their availability is controlled by three main factors, namely, climatic conditions, host tree age, and host species identity, which we will discuss in what follows. ...
Vascular epiphytes are an important component of many ecosystems and constitute a substantial part of global plant diversity. In this context, accidental epiphytism, that is, the opportunistic epiphytic growth of typically terrestrial species, deserves special attention because it provides crucial insights into the global distribution of vascular epiphytes and the initial evolution of epiphytic lineages. Even though accidental epiphytes have been mentioned in the literature for more than a century, they have been neglected in most epiphyte studies. Only recently has accidental epiphytism been investigated more thoroughly. Therefore, the aim of this article is to provide a comprehensive review of the ecological basis and evolutionary relevance of this common but largely neglected phenomenon and to highlight open questions and promising research directions. Our central statement—that any species has the potential to grow epiphytically given the availability of suitable microhabitats and successful dispersal—is backed up by a compilation of observations of accidental epiphytes from numerous ecosystems with diverse climates, even including semiarid Mediterranean ones. A variety of arboreal microhabitats and environmental conditions conform to the ecological niche of typical terrestrial species, with the availability of such microhabitats depending on the interaction of local climate conditions, host tree age, and host species identity. Whenever suitable microhabitats are available in tree crowns, accidental epiphytism is limited primarily by dispersal. In an evolutionary context, the conquest of forest canopy represents an ecological opportunity where accidental epiphytes act as links between terrestrial and epiphytic life forms. We discuss two fundamental scenarios with sympatric speciation, selective pressure, autopolyploidy, and allopatric speciation as underlying mechanisms in the transition from terrestrial to epiphytic growth. In conclusion, we argue that accidental epiphytism is a substrate and dispersal‐dependent phenomenon and that, both from an individual perspective and an evolutionary perspective, epiphytism reflects the occupation of suitable but previously unexploited arboreal microhabitats. Acknowledging the fundamental principles that plant growth is opportunistic and that dispersal is a stochastic process can decisively improve our understanding of species distributions and other ecological patterns, as in the case of accidental epiphytism.
... Tree ferns facilitate regeneration of certain species (Gaxiola et al., 2008); hence they have an important influence on the regeneration niche of potentially dominant tree species through macro-litter fall and shading with effects on nutrient cycling. A number of tree ferns species are recognized as keystone species for their role in casting deep shade on forest floor environment, acting as a differential ecological filter on regeneration processes (Forbes et al., 2016). ...
Introduction:
Tree ferns are significant components of temperate, tropical and subtropical forests, contributing to shape complex forest stand structures.
Objectives:
1) to describe the population structure of Cyathea costaricensis in a remnant cloud forest of West-central Mexico; 2) to characterize and relate the floristic composition and the structure of the most important tree species associated to the C. costaricensis population and; 3) to describe the environment where C. costaricensis occurs.
Methods:
We estimated the Importance Value Index (IVI) to select the most important canopy-dominant species associated to C. costaricensis; we constructed height and Diameter at Breast Height (DBH) frequency distributions for those selected species according to IVI as well as for C. costaricensis population; we computed the asymmetry of the frequency distributions through the coefficient of skewness and the probability density function via the Kernel density estimation. We tested for differences between canopy-dominant tree species and C. costaricensis population structure by the non-parametric Wilcoxon rank sum test.
Results:
C. costaricensis individuals presented the smallest heights and intermediate DBH sizes as compared with the canopy-dominant species, with statistically significant differences for height but not for DBH according to the Wilcoxon test. Most of the tree fern individuals were located in uneven terrains and over the base slope of the terrain; canopy openness and Total Radiation Under the Canopy values were similar to those reported for Cyathea species elsewhere.
Conclusions:
We confirm the hypothesis of comparable structure between the canopy-dominant species and the C. costaricensis population only for DBH; on the contrary, for trunk height, there were statistically significant differences; the small heights of C. costaricensis suggest their coexistence in the understory through sheltering from the taller canopy-dominants. Mostly all individuals of C. costaricensis were confined to local environmental conditions, particularly to physiography.
... Deleterious effects to tree ferns by faunal grazing does not appear to be an issue in Australia (or at least does not get a mention in any literature) but is an issue elsewhere. For example, in New Zealand, exotic species such as the common brushtail possum Trichosurus vulpecula, (imported from Australia), rats, mice and red deer (Gaxiola et al. 2008), graze tree ferns. Possums especially have heavily grazed on several tree fern species, which has resulted in the loss of the largest emergent trees and led to their replacement by smaller diameter stems and tree ferns (Bystriakova et al. 2011). ...
Australian forest ecosystems cover almost 16% of Australia’s landmass. As the seventh-largest forested area worldwide, these forest ecosystems have largely evolved in the face of a changing climate and fire regime, drought and human land use practice. Australian tree ferns contribute to both the unique biodiversity of these forests and current forest product markets. We review the Australian tree fern literature including: the importance of tree ferns for other components of biodiversity; their response to disturbance such as fire and silviculture; and the management of tree ferns as a product for the horticultural market. Most studies focused on tree fern response to wildfire and clearfell burn and sow logging following management and horticultural industry changes. Survival and recruitment of tree ferns after a single fire/logging disturbance event found short-lived negative impacts. Studies of tree ferns over time include research on growth, with non-linear growth models found to best describe tree fern age; Cyathea australia grows 2.2 - 4.0 times faster than Dicksonia antarctica on average. Tree ferns perform a keystone function through habitat for epiphytes at the local scale, but it is unknown if this has an impact on biodiversity at the landscape scale. Our review found few studies on survival and recruitment following drought; multiple disturbance events such as repeated logging; and silvicultural techniques other than clearfell burn and sow. No studies had investigated the response of tree ferns to changing climate, invasive species, changes in fire frequency or effect of megafire. We conclude with recommendations for key areas of research including, future impacts due to changing climate, synecology, influence on forests, the impact of silvicultural techniques and the influence of megafires on survival.
... Floyd (1990) states that seedlings of Eucryphia sp. are largely destroyed on the ground in Australian rainforests, particularly by wallabies, while plants establishing in slightly elevated positions on Dicksonia trunks survive. Similarly, introduced deer and possums in New Zealand prevent almost all ground-level regeneration of some facultative epiphytes and hemiepiphytes (Gaxiola et al., 2008;Knightbridge and Ogden, 1998). • Establishment of Clusia uvitana on the forest floor on BCI may be impossible because of pathogen attack on seedlings (Zotz, 2016). ...
Hemiepiphytic plants are defined by their ontogeny. They germinate on a host tree but later establish root contact with the soil. Most hemiepiphytes remain structurally dependent on their host for their entire life, but some, often referred to as stranglers, develop pseudotrunks that allow them to outlive their host. Unfortunately, the terminology used to describe hemiepiphytes and other structurally dependent plants (epiphytes, vines, lianas, nomadic vines, etc.) is highly inconsistent, which causes much ambiguity. Published reports frequently use the term “hemiepiphyte” without providing evidence, and it is often unclear whether conclusions are based on data, observations, or conjecture. Moreover, many hemiepiphytic species are facultatively terrestrial to varying degrees, which further complicates classifying them. In order to address these issues, we performed a thorough, critical review of the literature and provide an in-depth account of current knowledge regarding the morphology, physiology, ecology, and evolution of hemiepiphytes. Based on published works and our substantial field experience, we summarize the taxonomic distribution of hemiepiphytes among vascular plants, which includes c. 800 species in c. 30 families of ferns and angiosperms. We identify numerous, promising avenues of research on this fascinating group of plants, and make a case for adopting an explicit and unambiguous approach to describing hemiepiphytes and to naming life forms in research projects, on voucher specimens, and in the scientific literature.
... Tree fern trunks provide suitable establishment surfaces for epiphytes and hemiepiphytes, and surfaces for climbers to attach to (Pope 1926;Ashton 2000;Rivière et al. 2008;Gianoli 2015). Other than Weinmannia-tree fern communities (Wyse et al. 2018), however, the density of epiphytic establishment on tree ferns in the understorey is low, so damage from woody epiphytes may not be a significant risk for individual tree fern survival (Brock & Burns 2021;Veblen & Stewart 1980;Gaxiola et al. 2008). Furthermore, although some species of epiphyte frequently establish close to the growing crown (e.g. ...
... Furthermore, although some species of epiphyte frequently establish close to the growing crown (e.g. Pseudopanax spp; Dawson 1986), many woody epiphytes regenerate closer to the base of the trunk (Ogden et al. 1986;Bellingham & Richardson 2006;Gaxiola et al. 2008). ...
... Today, they are the secondlargest group of vascular plants, comprising around 10,000 species (PPG I 2016). Ferns play important roles in tropical and temperate ecosystems, where they can act as keystone species Bazzaz 1999a, 1999b;Coomes et al. 2005;Gaxiola et al. 2008;Walker et al. 2010), alter ecosystem nutrient cycling (Russell et al. 1998;Vitousek et al. 2009), and control successional processes (Walker 1994;Walker et al. 2010). Human affairs are also heavily impacted by these plants; invasive ferns like Lygodium spp. ...
