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A redwood tree whose crown is a forest canopy
Abstract
Ancient redwood trees (Sequoia sempervirens) often have complex crowns consisting of multiple, resprouted trunks. This study focuses on a single redwood tree, which is known as the Redwood Creek Giant, growing in Tall Trees Grove of Redwood National Park, CA. It is the sixteenth tallest (109.8 m) known living tree and the twentieth largest (744.7 m3 wood volume) known living redwood. The main trunk, which is 5.6 m in diameter at the base and still over 3 m in diameter at 65 m, is devoid of branches for 54 m. Above this height, its crown becomes a forest; there are a total of 148 resprouted trunks arising from the main trunk, other trunks, or branches. Five of these trunks exceed 1 m basal diameter, and twelve of them are between 0.5 and 1 m basal diameter. The largest resprouted trunk is 40 m long. Many of the trunks are fused to other trunks and/or branches. The tree's crown, which begins above 50 m, is over 25 m diameter 100 m above the ground. A variety of vascular plant species grow as epiphytes in this tree, including two ferns (Polypodium scouleri and P. glycyrrhiza), a shrub (Vaccinium ovatum), and two trees (Lithocarpus densiflorus and Umbellularia californica). The highest recorded epiphytic tree, an U. californica, grows from a knothole 98.3 m above the ground.
... Apical dominance declines with age, and with the help of stochastic events such as wind, lightning, and mechanical damage, crown structure is reshaped. Codominant trunks are common in older specimens of S. sempervirens, and in some cases can result in reiterated trees high in the canopy (Sillett and Van Pelt 2000a;Shigo 2008). Large lateral branches are also formed, which provide habitat features in the form of deep crotches and platforms, and vegetative sprouting from the tree bole allows for the creation of epicormic branches and root growth into arboreal soils. ...
... These epiphytic communities, in turn, provide habitat for wildlife species such as Aneides vagrans (Wake & Jackman 1998) (wandering salamander), a species that spends in entire life cycle in the forest canopy (Zielinski and Gellman 1999;Enloe et al. 2006;Spickler et al. 2006;Sillett and Van Pelt 2007). Mossy lateral branches provide nesting habitat for endangered avian species including Brachyramphus marmoratus (Gmelin and JF 1789) (marbled murrelet) and Strix occidentalis caurina (Merriam 1898) (northern spotted owl) (LaHaye and Guti´errez 1999; Sillett and Van Pelt 2000a;Baker et al. 2006). Large persistent fire caves, both at the base of trees, and in the canopy, provide habitat for Sitta pygmaea Vigors 1839 (pygmy nuthatches), Tyto alba (Scopoli 1769) (barn owls), nesting Tachycineta thalassina (Swainson 1827) (violet-green swallows), in addition to a variety of species of spiders and bats (Zielinski and Gellman 1999;Willet 2001). ...
Abstract
Old-growth Sequoia sempervirens (D. Don) Endl. (Cupressaceae) forests are commonly assumed to be populated by massive trees, but those growing on nutrient poor soils can be stunted and display unusual growth-forms. We characterized soils, stand structure, growth form, and crown complexity using a combination of random and targeted stratified sampling across an old-growth redwood/pygmy forest ecotone. ANOVA indicated significant variation in stand structure metrics and soil characteristics [pH, cation exchange capacity (CEC), and nutrient availability] among strata, with tree height, basal area, and the relative dominance of redwood-associated species declining under the influence of pygmy forest soils; while shrub cover and the dominance of pygmy associated species increased. Pearson's coefficients indicated positive correlations between tree height and diameter with CEC, P, K, Ca, and Na. Stepwise linear regression suggested that P, K, and CEC were the strongest predictors of tree height and diameter. Growth form and crown structure of S. sempervirens also varied considerably across the ecotone, with stunted multi-stemmed individuals and clusters of small diameter trees observed where pygmy soil conditions were most extreme, and larger, but still stunted ancient redwoods with complex crown structures, resident epiphytes, and large fire hollows, existing on the edge of the pygmy forest. The ancient redwoods sampled within the old-growth/ pygmy ecotone were remarkably small in stature, yet contained many of the same structural characteristics associated with the largest and oldest S. sempervirens.
... Redwoods are the tallest organisms on earth, with individual trees exceeding 112 meters in height, and can live for thousands of years (Sawyer et al. 2000). Large, old redwood trees are also among the most complex on earth, with sprawling crowns consisting of massive limbs, and multiple resprouted trunks called "reiterations" (Sillett 1999;Sillett & Van Pelt 2000). The extreme age, size, and complexity of redwood crowns promotes the interception and accumulation of organic debris (e.g., leaf litter, bark, twigs, and cones) on thick branches and at the bases of reiterated trunks. ...
... Previous research in old-growth redwood forest canopies has been focused on tree crown structure (Sillett 1999;Sillett & Van Pelt 2000), epiphyte distributions (Sillett 1999;Bailey 2000;Sillett & Bailey 2003;Lovelace 2003;Williams 2004), salamander ecology (Spickler 2004), and tree physiology (Jennings 2003;Koch et al. 2004). Due to the ability to store water and nutrients, buffer microclimatic conditions, and serve as habitat for arboreal organisms, canopy soil plays an important role in redwood forests where it is present. ...
... In North America, large trees in old-growth rainforests on the Pacific coast hold a sizeable amount of arboreal soil in their crowns (Enloe et al., 2006;Haristoy et al., 2014), which can support an enormous accumulation of epiphytic biomass (Sillett & Bailey, 2003;Sillett & Van Pelt, 2007). For instance, in northwestern California, more than 150 individuals of about 15 typically terrestrial species were found on just 10 old-growth gymnosperm trees (Gorman et al., 2019;Sillett, 1999;Sillett & Van Pelt, 2000). Further north, Nadkarni (1984a) observed two herbaceous species as accidental epiphytes on Acer macrophyllum trees on the Olympic Peninsula. ...
Vascular epiphytes are an important component of many ecosystems and constitute a substantial part of global plant diversity. In this context, accidental epiphytism, i.e. the opportunistic epiphytic growth of typically terrestrial species, deserves special attention as 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 accidental epiphytism was investigated more thoroughly. Therefore, the aim of this article was to provide a comprehensive review of the ecological basis and the evolutionary relevance of this common but largely disregarded phenomenon and to highlight open questions and promising research directions. Our central statement that potentially any species could 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 semi‐arid Mediterranean ones. There are a variety of arboreal microhabitats with environmental conditions conforming 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 primarily limited by dispersal. In an evolutionary context, the conquest of the forest canopy represents an ecological opportunity where accidental epiphytes act as link between the terrestrial and the epiphytic life form. 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 from 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.
... HRSP retains the largest aggregation of remaining tall redwoods. Approximately 80% of trees > 107 m tall are located in HRSP (Van Pelt et al., 2016), likely due to their protection from winter storms by the King Mountain Range which lies between HRSP and the Pacific Ocean (Sillett et al., 2015;Sillett and Van Pelt, 2000;Van Pelt et al., 2016). ...
In forest ecosystems, road expansions and other landcover changes create abrupt artificial boundaries that alter the microclimate along the forest edge, potentially impacting growth and physiology of bordering trees. To understand how previous landcover changes and road installations have affected coast redwoods (Sequoia sempervirens), we used dendroecological methods to contrast tree-ring growth patterns and stable isotopes (Δ 13 C) of redwoods before and after a known disturbance event, the expansion of Highway 101 in the 1950s, that bisected several old-growth stands of Humboldt Redwoods State Park. Increment cores were extracted from redwoods in old-growth stands that bordered the highway and other forest edges (secondary forests and agricultural fields) as well as two control areas. Disturbance detection methods and dendroclimatic modeling were then employed to determine whether the expansion led to growth suppression and elevated water stress. Tree-ring growth data indicated that the construction of Highway 101 disproportionately impacted the growth of trees that were within 30 m of the highway and that these effects were particularly elevated in trees that currently exhibit crown dieback. Similarly, climatic modeling of tree-ring Δ 13 C data indicated that highway adjacent trees also experienced elevated water stress for several decades following the construction of the highway. By analyzing tree-ring data of redwoods within Humboldt Redwoods State Park, here we provide critical insight to the temporal and spatial implications of the habitat fragmentation and road installation that has been nearly ubiquitous in the redwood distribution since Euro-American settlement.
... In the north-temperate zone, epiphytic individuals of accidental epiphytes are almost exclusively restricted to water-buffering substrates such as extensive moss mats or accumulations of dead organic matter and arboreal soil (Sillett and Van Pelt, 2000;Zotz and List, 2003;Hoeber et al., 2019). Undoubtedly, the general scarcity of epiphytic individuals on bare bark of branches at higher latitudes is due to low water availability. ...
Vascular epiphytes are mainly associated with tropical and subtropical forest ecosystems. However, the frequent occurrence of accidental epiphytes in temperate forests proves that epiphytic growth of vascular plants is possible in tree crowns at these latitudes. Comparing the abiotic conditions of epiphytic and terrestrial microhabitats in conjunction with intraspecific differences in functional traits of the inhabiting plants, we identified limitations to vascular epiphytism in the study area in a Central European low mountain range. We determined light availability, winter temperatures, soil moisture, nutrient concentrations, and pH of arboreal soil in crotches of broad-leaved trees and in the immediate vicinity of each tree on the ground. Similarly, we quantified total plant water content, relative foliar chlorophyll content, specific leaf area (SLA), leaf dry matter content (LDMC), root-mass fraction, and aboveground nutrient concentrations of 110 pairs of epiphytic and terrestrial conspecifics. Water and nutrient availability were generally high in crotches filled with arboreal soil, suggesting better growth conditions than on the ground. A trophic advantage of epiphytic individuals over terrestrial conspecifics can be deduced from higher plant nutrient concentrations, higher SLA, and lower LDMC. Advantageous growth conditions might even result in higher growth rates and higher fitness of epiphytic individuals. Our findings highlight that vascular epiphytism in the study area is not necessarily limited by abiotic conditions but at least partly by the availability of old and structurally diverse trees providing suitable microhabitats. Accordingly, management actions in these secondary forest ecosystems should incorporate the preservation of old and large deciduous trees in order to sustain arboreal microhabitats and the associated biota.
... Gentry & Dodson, 1987;Zotz, 2002), there are frequent, albeit mostly anecdotal, accounts of epiphytic individuals of usually terrestrial plant species in the temperate zones (e.g. Guzmán-Marín & Saldaña, 2017;Sharp, 1957;Sillett & Van Pelt, 2000;Stäger, 1908;Zotz & List, 2003). Such terrestrial species with occasional epiphytic occurrence are referred to as accidental epiphytes (cf. ...
Questions
Vascular epiphytes make up about 9 % of all vascular plants globally but are clearly underrepresented in the temperate zones. The accidental epiphytic occurrence of terrestrial species, in contrast, is common at these latitudes and can provide important insights in the evolution of obligate epiphytes. Here we present the results of the first two annual censuses of a planned long‐term study on accidental epiphytes. We particularly aim to identify: (1) the abundance and species richness of accidental epiphytes, (2) the dynamics of accidental epiphytism, (3) occupied substrates and microsites and (4) suitable host tree species.
Location
Harz Mountains, Germany, Central Europe.
Methods
We surveyed more than 1200 trees in a low mountain range in two consecutive years for epiphytic individuals of vascular plants considering host tree species and occupied microsites.
Results
About one quarter of the surveyed trees hosted epiphytic plants, totalling 1450 (2016) and 1350 (2017) individuals, respectively. These belonged to more than 100 species of 39 different families. The majority of epiphytic individuals in 2017 newly emerged, whereas one third persisted since 2016 (or earlier) and a smaller proportion even reproduced in the epiphytic habitat. Accidental epiphytes were mostly restricted to host tree species providing water‐storing substrates such as extensive moss pads or arboreal soil accumulated in crotches. Compared to tropical epiphyte communities, accidental epiphytes in the temperate zones show a higher turnover, as they are less consistent in species abundance and composition in time.
Conclusion
For the majority of the observed species, epiphytism indeed is an accidental phenomenon. Undoubtedly, abiotic conditions limit the occurrence of obligate epiphytes at higher latitudes, but the presence and persistence of numerous epiphytic individuals illustrates that abiotic conditions do not per se preclude epiphytic occurrence of vascular plants in the north‐temperate zone. Besides water shortage, the availability of suitable host trees is a decisive environmental factor that contributes to limit epiphytism of vascular plants in Central Europe.
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... Giant sequoias (Sequoiadendron giganteum) are the world's largest trees, with breast height diameters of up to 8.8 m (29 feet) and total height up to 93.5 m (307 feet). The presence of giant trees enhances terrestrial ecosystems as the large canopies increase biodiversity and biomass parameters (Franklin et al., 2002;Lindenmayer et al., 2012;Sillett, 1999;Sillett et al., 2015;Sillett and Van Pelt, 2000;Van Pelt, 2001). These trees are uniquely important as an in situ genetic resource (Stefenon et al., 2009) and as a source of habitats for fauna and flora (Lindenmayer and Laurance, 2016). ...
Araucaria angustifolia (Bertol.) Kuntze is a native tree species of major importance in southern Brazil. It is a regional symbol due to its iconic shape and stature in the landscape; its wood was once economically important and its seeds are an important source of food for the fauna and are presently used in regional cuisine. Despite its importance and apparent abundance, the species is facing extinction mainly as a result of unregulated exploitation and deforestation. This study catalogued the remaining individuals in order to add to the body of knowledge available on A. angustifolia, a species that has become rare across its historic range. The circumference at breast height (1.30 m), the total height, and the tree volume were measured (3,529 araucarias). We catalogued trees with a large diameter measuring them in loco over three years involving a journey of more than 6,800 km. The volumes of these old trees are very large, ranging from 38.2 m ³ to 106.6 m ³ . The largest A. angustifolia individual is located in the state of Santa Catarina and measures 3.25 m in diameter. The giant araucarias with > 2.00 m in diameter are rare and only 13 individuals could be found in southern Brazil; a priority action at the governmental level is to recognize and preserve these monumental trees and together with a need for a public policy of drawing up specific inventories of large trees.
... The process of reiteration in tree crowns is analogous to the regeneration of trees in a forest stand (Sillett and VanPelt, 2000;Ishii and McDowell, 2002). In large trees, while radial increments at breast-height may decline, increments of wood volume, including the crown, may still be increasing as the crown rejuvenates through reiteration (Van Pelt and Sillett, 2008;Sillett et al., 2010). ...
Large trees are the most prominent structural features of old-growth forests, which are considered to be globally important carbon sinks. Because of their large size, estimates of biomass and growth of large trees are often based on ground-level measurements (e.g., diameter at breast height, DBH) and little is known about growth dynamics within the crown. As trees increase in size, growth of the crown may not be reflected in DBH measurements contributing to inaccuracy of aboveground forest productivity. Here we present data from a 10-yr re-measurement of crown structure and branch/trunk growth of 400-year-old Pseudotsuga menziesii trees in an old-growth forest in western Washington, USA. In six study trees, 40–60% of branches occurred in the upper third of the live crown. Branch mortality over 10 years was highest in the lower third of the crown. Of live-branch mass (including leaf mass), 41–78% occurred in the middle third of the live crown. During the study period, live-branch mass increased in the upper half of the crown and there was little loss due to fragmentation or death. In contrast, increment of live-branch mass was negligible and live-branch mass decreased in the lower half of the crown. On average, 70–99% of the increment of live-branch mass per tree occurred in the upper half of the crown. Core samples taken from various heights indicated that trunks became less tapered with increasing age as a result of greater increments of upper-trunk radius during the most recent 10 years. Increment of live-branch mass contributed 42 and 66% of the whole-tree and upper-crown increments of mass, respectively, and its vertical distribution corresponded to that of leaf mass density. Increments of trunk mass contributed 88% of the lower-crown increment. Growth increments of the crown were not reflected in core samples taken at lower heights. Our estimates of trunk, branch, and leaf mass were consistently smaller than those calculated using empirical allometric equations based on tape-wrap measurements of DBH. Moreover, leaf mass decreased in four trees, whereas allometric equations predicted increases. Our results indicate that large P. menziesii trees can sustain wood mass production, especially in trunk and branches of the upper crown, while leaf mass change can be more dynamic, and that such growth dynamics of the crown are difficult to detect via DBH-based measurements.
... PC has 1760 ha of forest with trees >90 m (the largest single area remaining), which also contains several of the largest known individual trees (Van Pelt, 2001; Sillett et al., 2015a). Both JS and PC's proximity to the coast makes them exposed to winter storms that damage tree crowns, but subsequent growth and recovery of Sequoia creates some of the largest and most complex tree crowns (Sillett and Van Pelt, 2000; Sillett et al., 2015a). Redwood National Park (RNP), which currently occupies 26,700 ha of the lower Redwood Creek drainage, was an area of intense logging during the mid-20th century. ...
Forests >80 m tall have the highest biomass, and individual trees in these forests are Earth’s largest with deep crowns emerging above neighboring vegetation, but it is unclear to what degree these maxima depend on the emergent trees themselves or a broader-scale forest structure. Here we advance the concept of _emergent facilitation_, whereby emergent trees benefit co-occurring species. Trees reorganize foliage within crowns to optimize available light and, if long-lived, can reiterate after crown damage to become emergent. The height, depth, and spacing of emergent trees in turn allows for abundant light to pass through the canopy, leading to light-use complementarity as well as elevated biomass, leaf area, and species diversity of the forest as a whole. We chose _Sequoia sempervirens_ to develop this concept and installed eleven 1-ha plots in old-growth forests spanning nearly six degrees of latitude in California. Each plot was based off a 316-m-long centerline where biomass and leaf area of all vegetation were quantified. We employed hierarchical measurements and stratified random sampling spanning the full size range of individuals to generate 180 equations for determining biomass and leaf area of all dominant plant species in these forests. Biomass (5190 Mg ha−1), leaf area (LAI = 19.4), and aboveground carbon (2600 Mg ha−1) are global maxima, occurring in plots with the highest proportion of emergent trees. Decay-resistant _Sequoia_ heartwood contributes the bulk of this mass, ranging from 61.5 to 76.7% of plot totals. Heartwood is a key contributor to the development of trees with emergent crowns, since its durability enables trees to recover leaf area and to re-grow crowns after damage so that they can continue expanding for millennia. By distributing leaf area among fewer trees with deeper crowns, _Sequoia_ maintains very high leaf area itself (LAI up to 14.5) while simultaneously allowing other species to flourish underneath (non-_Sequoia_ LAI up to 8.0). Because _Sequoia_ is not replaced by other species, aboveground biomass, leaf area, and carbon content of these forests are essentially asymptotic over time.
... Many long-lived, latesuccessional species can reiterate architectural units and maintain the crown, in contrast to short-lived early-successional species, which tend to have less ability to reiterate crown components (Millet et al. 1998). Reiteration of various architectural units ranging from shoots and twigs to entire branches and vertical axes (reiterated trunks) has been observed in some large, old trees of long-lived species, including redwoods (Sequoia semprevirens, Sillett and Van Pelt 2000) and Douglas-fir (Ishii and Ford 2001). Understory trees of European beech (Fagus sylvatica), a shade-tolerant, late-successional species, maintain the crown by means of reiteration when growth is suppressed due to limited light conditions (Nicolini et al. 2001). ...
Currently, there are techniques that enable safe and repeated access to the forest canopy to study the 3-D structure of forest ecosystems and ecological processes occurring in the canopy. The 3-D distribution of tree crowns reflects how trees occupy space in the canopy to capture light resources and drives critical ecological processes such as stand productivity and forest community dynamics. However, measurement of forest canopy structure presents a great challenge. Visual observation suggests that the canopy of young stands and plantations are structurally homogeneous and simple compared with that of old-growth stands. This difference has been shown through comparative studies of two-dimensional stand structure. Species composition and tree size distributions become more diverse with increasing stand age, and specific structural elements such as large, old trees and snags characterize older stands. The chapter reviews the canopy processes that drive the development of structural complexity with increasing stand age and present a 3-D canopy perspective of structural development of temperate forest ecosystems. Since trees form the basic framework of canopy structure, dynamics of tree crowns define structural development of the forest canopy.
... For the third method (single-tree method), I conducted single censuses from the crowns of 22 separate trees interspersed throughout the entire study area. I used a crossbow and single-rope technique to climb canopy trees (Sillett and Van Pelt 2000). I selected census trees on the criteria that they were safe to climb, had an open crown structure that allowed views out of the census tree, and were a minimum of 50 m from other census trees. ...
... Surface geology at the site consists of Mesozoic sandstones and shales of the Shimanto group (http:// riodb02.ibase.aist.go.jp/db084/index.html). Temperate coniferous forests containing extremely high biomass have been observed in regions of the Northern Hemisphere that experience high precipitation and relatively warm winters (Franklin and Dyrness 1973;Sillett and van Pelt 2000;Takyu et al. 2005). The combined aboveground and belowground biomass of the study forest is about 800 t/ha (Ando et al. 1977;Ishihara et al. 2011). ...
We investigated the factors determining the distribution and dynamics of tree species in a warm–temperate mature mixed forest of evergreen coniferous and broad-leaved tree species in a steep mountainous area for 13 years in southwest Japan, with particular focus on instability of the ground surface. Among various site conditions, landform unit was the principal factor determining the distribution of tree species, while moisture regime was the second-most important factor within the upper area. The amount of movement of sediment and litter on the ground surface in the lower area was much higher than movement within the upper area, indicating that the lower area was unstable due to mass movement caused by erosion. The effects of instability of the ground surface on mortality and recruitment varied across the dominant tree species. Symplocos prunifolia (SYMPLOCACEAE), which was distributed in the upper area, and Machilus japonica, which was distributed in the lower area, exhibited lower mortality and higher recruitment in the areas where they were mainly distributed. These results suggest that topographic niche differentiation caused habitat segregation for some species. However, for most species, such relationships were not consistently observed, and growth rates did not significantly differ between the upper and lower areas. This study, by using long-term data, demonstrates that variation in sensitivity to stability due to topography contributes to local species richness and co-existence.
... Severe winter storms contribute to the complexity of redwood canopies by snapping tops and branches. This episodic disturbance leads to reiterative growth of new leaders and provides a distinctive habitat for flora and fauna of the redwood forest (Sawyer et al., 2000c;Sillett and Van Pelt, 2000). ...
... m 3 in volume). These trees, on which we have worked extensively (Sillett 1995, Sillett and Van Pelt 2000, Van Pelt and Franklin 2000, Ellyson and Sillett 2003, Van Pelt et al. 2006; R. Van Pelt, S. C. Sillett, and C. B. Williams, unpublished data) have an architectural model similar to Pseudotsuga's and also produce reiterated trunks and limbs in response to crown damage (Fig. 11). Moreover, we have observed many other conifers that commonly produce limbs and reiterated trunks in response to FIG. 11. ...
Seventy trees from seven stands 50-650 years old were selected for this investigation of crown structural development in Pseudotsuga menziesuii All branches, limbs, and trunks were nondestructively measured for size, structure, and location while climbing the trees with ropes. These data were used to generate a computer model of each tree's crown that was error-checked trigonometrically. Leaves, bark, cambium, and wood were quantified by using limited destructive sampling to develop predictive equations that were applied to the complete inventory of structures in each tree's crown. Summations of these values yielded whole-tree estimates of several structural variables. A second set of equations was then developed to predict these whole-tree parameters from simple, ground-based measurements. Principal components analysis of 24 tree-level variables revealed two orthogonal dimensions of structure that accounted for 71.3% and 12.4% of total variation in the 70 trees. The first dimension represented a gradient of overall tree size and structural complexity that was positively correlated with tree age (R2 = 0.89). The second dimension represented a gradient of incremental growth potential that was positively correlated with measured growth of main trunks at breast height during the five-year period after trees were mapped (R2 = 0.39). The strongest determinant of incremental growth potential was the ratio of a tree's total cambium surface area to projected leaf area. A tree's incremental growth potential may thus be unrelated to either size or structural complexity and depend instead on factors related to whole-tree carbon balance (e.g., how much the tree invests in fighting and feeding fungi). Our intensive analyses of Pseudotsuga menziesii and extensive observations of other species were used to develop a conceptual model of crown development in tall conifers. Trees respond to disturbances by growth of replacement structures whose form depends on disturbance intensity and age. Young trees rebuild damaged crowns through epicormic shoot production on original branches, whereas older trees also recover by producing new, epicormic branches. Damage to main trunks and top dieback stimulate production of reiterated trunks. Repeated damage leads to multiple hierarchical levels of trunk reiteration as well as to limb formation and increasing tree individuality.
... Millet et al. (1998a) observed similar processes of dieback and regrowth within the crown of late-seral tree species in the temperate deciduous forests of southwestern Quebec. Sillett and Van Pelt (2000) also documented detailed crown structure and reiteration of several branches and vertical axes in an old redwood (Sequoia sempervirens (D. Don) Endl.) tree in northern California. ...
Impacts of human activity on forest ecosystems are most pronounced in the temperate region. Simplification of stand structure has resulted in diminished ecosystem function and biodiversity decline, raising much debate over future management policies. Ecosystem functions and biodiversity may be enhanced by managing forests for increased structural complexity. However, processes that determine relationships among structural complexity, ecosystem functions, and biodiversity of forest ecosystems remain unclear. In this review, we present examples of studies conducted at two canopy research facilities located in different types of temperate forest to illustrate that structural complexity of forest canopies enhances stand productivity and biodiversity: (1) development of structurally complex canopies comprising various tree species enhances stand productivity by promoting complementary resource utilization among species through spatial, physiological, and temporal differentiation; and (2) development of complex canopy structure enhances biodiversity of canopy-dwelling organisms by creating a resource-rich habitat. These ecological observations stress the importance of including three-dimensional structural attributes of forest canopies in management plans and silvicultural prescriptions that aim to maintain ecosystem functions and biodiversity. FOR. SCI. 50(3):342355.
... For the third method (single-tree method), I conducted single censuses from the crowns of 22 separate trees interspersed throughout the entire study area. I used a crossbow and single-rope technique to climb canopy trees (Sillett and Van Pelt 2000). I selected census trees on the criteria that they were safe to climb, had an open crown structure that allowed views out of the census tree, and were a minimum of 50 m from other census trees. ...
Birds of the forest canopy are important components of tropical forest ecosystems, but difficulty of access or viewing into the canopy complicates their study. If ground methods are biased against canopy birds, as has been suggested, this bias could affect our understanding of forest ecology as well as biological monitoring and conservation practices. This study is the first to quantitatively compare results from ground- and canopy-based methods of censusing canopy birds. I used three methods to assess differences in ground-based and canopy-based methods for detecting forest birds in a 100-ha plot of lowland forest in northern Honduras: (1) point counts from the ground, (2) 22 repeat censuses from two canopy trees, and (3) single censuses from 22 canopy trees. I counted birds for a full annual cycle from April 2006 to April 2007 and recorded 157 species in over 4000 individual detections. Ground methods significantly underestimated species and familial richness as well as abundance of individuals in the canopy stratum. On the basis of these results, I predict that the use of ground methods alone misses 25 to 50% of the species richness for some migrant and resident families and underestimates the density of some species by as much as 25%. These findings highlight the risk of relying on ground-based methods for bird studies in structurally complex tropical forests; reliance on ground-based methods may negatively affect long-term biological monitoring and the setting of conservation priorities for tropical forests.
... ). With increasing size and age, single trees may become as complex as the whole forest canopy, comprising reiterated stems and branches of various sizes that interact with each other as the tree continues to grow (Sillett and Van Pelt 2000). Ground-level measurements may indicate decreasing growth of the lower trunk with increasing size and age, but the crown may comprise vigorously growing young branches and reiterated trunks. ...
With increasing height within the crowns of tall trees, leaves tend to become smaller and thicker and shoots shorter. In tall
trees, the vertical variation in leaf/shoot morphology is largely driven by water status. Morphological changes associated
with increasing height in the crown present static constraints on photosynthesis, such as decreasing light intercepting area
relative to leaf mass and decreasing CO2 diffusion rate inside the leaf. Despite high light availability, leaf-area-based photosynthetic rates at the tops of tall
trees tend to be low and this may limit height growth. However, the observed changes in leaf/shoot morphology as well as xylem/leaf
anatomy, and crown architecture may compensate for various physiological constraints associated with increasing tree height.
Continuous renewal of branches and foliage through epicormic shoot production and the change from hierarchic to polyarchic
crown architecture may allow large trees to maintain physiological function and continue to grow.
... Severe winter storms contribute to the complexity of redwood canopies by snapping tops and branches. This episodic disturbance leads to reiterative growth of new leaders and provides a distinctive habitat for flora and fauna of the redwood forest (Sawyer et al., 2000c;Sillett and Van Pelt, 2000). ...
Coast redwood (Sequoia sempervirens), a western North American conifer of ancient lineage, has a paradoxical combination of late-successional characteristics and strong adaptations to disturbance. Despite its shade tolerance and heavy dominance of the canopy on many sites, redwood saplings are uncommon in upland old-growth stands. Information needed to ensure the conservation of old-growth redwood forests has been limited. In this review paper, we integrate evidence on redwood biology with data on the historic and modern disturbance regimes to help clarify the degree to which key attributes of redwood forests may have been dependent upon periodic disturbance. Available evidence suggests that episodes of fire, flooding, and slope failure prior to European settlement were frequent but predominantly of low to moderate severity and extent, resulting in broadly uneven-aged forests. The majority of fires prior to European settlement were apparently of human origin. Frequency and severity of the major disturbance agents have been radically changed in modern times. Fires have been largely excluded, and flooding has been altered in ways that have often been detrimental to old-growth redwoods on alluvial terraces. However, because of the apparent anthropogenic origin of most presettlement fires, the long-term evolutionary role of fire for coast redwood is ecologically ambiguous. With fire exclusion, redwood possibly could be displaced to some extent on upland sites by increasing abundance of fire-sensitive competitors. Alternatively, redwood may be able to maintain dominance by vegetative sprouting and new seedling establishment on root-wad mounds, fallen logs, and on soil exposed by slope failure. Future research priorities are suggested that will help resolve some of the current ambiguities.
We used rope techniques to access epiphyte communities on nine large and structurally complex redwoods (Sequoia sempervirens) occupying old-growth forest reserves of northwestern California. All species of epiphytic lichens, bryophytes and vascular plants were recorded, biomass of dominant vascular epiphytes (Polypodium scouleri and Vaccinium ovatum) was quantified, and tree crowns were mapped to estimate substrate surface areas. We employed a flexible, plot-based sampling regime defined by available microhabitats within height strata to search for epiphytes. All substrates were examined, including tree surfaces, canopy soils and perennially exposed surfaces of epiphytic vascular plants as well as forest floor vegetation, woody debris and terrestrial soils beneath the redwood crowns. Combined arboreal and terrestrial search efforts revealed 282 species, including 183 lichens, 50 bryophytes and 49 vascular plants. Beta diversities for plots aggregated by floristic group, stratum and substrate type were generally high, indicating a large proportion of infrequent species. Indirect ordination analysis suggested that an environmental gradient from exposed to sheltered habitats was the strongest factor controlling epiphyte community structure. Floristic groups, strata and substrates were highly segregated along the dominant compositional gradient. Chlorolichens, upper crown strata and redwood foliage occupied one end, while vascular plants, forest floor strata and terrestrial woody debris occupied the other end of the gradient. Indicator Species Analyses revealed that many species expressed affinities for particular substrates, including live vs. dead foliage, bark of small vs. large branches and limbs, bark of upper vs. lower surfaces of large limbs, bark of large trunks, bare wood, bryophyte mats, soils, non-redwood stems and terrestrial woody debris. Cluster Analysis identified seven groups of species with similar patterns of distribution across height strata and substrate types. Correlations between tree structure and species distribution suggested that structural complexity promoted epiphyte diversity within height strata. Surface areas of small live trunks, limbs and dead trunks were the best predictors of lichen species richness, Polypodium scouleri biomass and Vaccinium ovatum biomass, respectively. At least one new species (Calicium sp. nov.) was discovered, and two species (Buxbaumia piperi, Icmadophila ericetorum) normally restricted to terrestrial habitats were found as canopy epiphytes for the first time.
We measured the radial growth response of large (>2 m dbh) giant sequoia (Sequoiadendron giganteum) trees to a wide variety of mechanical treatments. Treatments varied widely in the amount of neighboring competition that was removed. A relatively low-intensity treatment removed surrounding small neighboring trees, a moderate-intensity treatment removed neighboring codominant canopy trees on one side via gap creation, and a high-intensity treatment removed trees from large areas completely surrounding individual large giant sequoias. The majority of study trees ranged in age between 500 and 1,500 years old. The high-intensity treatment that removed all surrounding trees resulted in the strongest and most persistent growth release compared with that of control trees. Surprisingly, the low-intensity treatment, which removed only trees Keywords: competition removal; giant sequoia; mechanical treatments; mixed conifer forest; release Document Type: Research Article DOI: http://dx.doi.org/10.5849/forsci.14-029 Publication date: October 28, 2015 More about this publication? Membership Information ingentaconnect is not responsible for the content or availability of external websites $(document).ready(function() { var shortdescription = $(".originaldescription").text().replace(/\\&/g, '&').replace(/\\, '<').replace(/\\>/g, '>').replace(/\\t/g, ' ').replace(/\\n/g, ''); if (shortdescription.length > 350) { shortdescription = "" + shortdescription.substring(0,250) + "... more"; } $(".descriptionitem").prepend(shortdescription); $(".shortdescription a").click(function(e) { e.preventDefault(); $(".shortdescription").hide(); $(".originaldescription").slideDown(); }); }); saf/fs/2015/00000061/00000005/art00015 dcterms_title,dcterms_description,pub_keyword 6 5 20 40 5 GA_googleFillSlot("Horizontal_banner_bottom");
Many aspects of tree physiology, epiphyte ecology, and stand-level forest dynamics can greatly benefit from whole-tree estimates of surface area, wood volume, and biomass. Surface area estimates are needed to determine carbon production for trees with photosynthetic bark and to estimate epiphyte habitat with tree crowns. Although most conifers carry much of their volume within a single stem, others-along with most angiosperm trees-contain much of their wood volume in branches within the crown. To assess these accurately requires knowing branch diameters within the tree, an extremely difficult task from the ground or even from the gondola of a crane. Biomass estimates in forests require quantification of components such as trunks, branches, and foliage. In tall-stature forests, this has been accomplished by felling one to many trees for samples. While the crowns of large trees are destroyed in the felling process, a small proportion of branches may be relatively undamaged. These can often be sufficient to develop regression equations for various components with the crown, but not for whole-tree estimates. Forest ecologists need a comprehensive, nondestructive sampling regime to obtain accurate whole-tree estimates of 3-D structure for any forest type. The chapter proposes a three-tiered approach to obtain 3-D structural information in forests.
The forest canopy is now considered a structurally complex and ecologically critical subsystem of the forest, and is defined as "the combination of all foliage, twigs, fine branches, their attending flora and fauna, the interstices (air), and their environment." For many critical canopy functions, all plants contribute. Similarly, the forest environment changes continuously from top to bottom, so the gradients cannot be subdivided objectively. In mixed-species, multi-aged stands, the upper layers alone do not represent canopy structure and all its microhabitats, microclimates, and exchange processes. Thus, researchers now recognize that the forest canopy is part of the forest ecosystem as a whole. Non-forest vegetation also supports canopies, such as kelp "forests," algal mats on a river bed, beds of sea grasses, orchards, lawns, wheat fields, and stromatolite aggregates. The chapter restricts the discussion to canopies associated with tall, woody plants; that is, terrestrial forests. In this context, the term canopy denotes forest community architecture as well as species composition, nutrient cycling, energy transfer, and plant-animal interactions from the ground to the forest-atmosphere interface. It also discusses the development of canopy studies and summarizes the general features of canopy composition, structure, and distribution. It identifies ways that humans and forest canopies have been linked through history and in the present, and then discusses the dependence of our species on forest canopies for fiber, fuel, food, medicines, and spirituality. It describes the involvement of forest canopies in pressing issues for anthropogenic change, such as biodiversity declines, carbon storage, and landscape management.
The availability of reliable information on tree climbing methods is critical for the development of canopy science and for the safety of workers accessing the forest canopy.
To assess the breadth and quality of information contained in published climbing information, we performed searches in Web of Science and Google Scholar and evaluated 54 published sources on 10 predetermined criteria related to safety.
We found a high incidence of unsafe recommendations that, if followed, could result in serious injury or death. Common errors included recommendations for equipment not suitable for tree climbing, advocating methods suitable for rock climbing but that can result in falls and trauma in tree climbing, and outdated information that no longer reflects best practices.
We conclude by providing safety recommendations and a short review of tree climbing methods. This article thus serves as a guide for finding and interpreting best sources of methods for canopy access.
Vascular epiphytes typically are associated with tropical rain forests, whereas their occurrence in temperate forests is little appreciated. This bibliography lists nearly 200 citations dealing with the biology of this group at latitudes beyond the tropics of Cancer and Capricorn. Papers on ecology, physiology, anatomy, morphology, and natural history are included, while purely taxonomic accounts are excluded. The bibliography also is available electronically (request to be sent to the author). Epífitas vasculares son típicamente asociados con los tropicos, menos apreciado es su presencia en los bosques templados. Esa bibliografía presenta casi 200 citas relacionadas con la biología de este grupo. Se incluye artículos sobre ecología, fisiología, anatomía, morfología y historia natural, pero en general se excluyó publicaciones puramente taxonómicas o florísticas. Esta bibliografía es disponible en forma electrónica (pedidos al autor).
Fitzroya cupressoides, or alerce, a massive conifer that occurs in southern Chile and southwestern Argentina, is known for exceptional longevity—a 3622-year crossdated chronology established the alerce as the second longest-living tree after California's Pinus longaeva. Despite the critical ecological significance and endangered status of the alerce, remarkably little is known about the crown habitat in these trees, including their plant and insect communities. In a preliminary assessment of alerce crown structure and plant and arthropod diversity, seven alerce individuals were climbed and surveyed in January 1998. The trunk and crown structure of each tree were measured and lianas, epiphytes, and arthropods were sampled in a series of height-stratified plots. Filmy ferns were the dominant vascular epiphytes while bryophytes, lichens, and three species of lianas were also abundant in well-developed communities. Several trees and shrubs were also discovered growing epiphytically in the alerce crowns. Arthropod diversity and abundance were very low, even compared with conifers from climatically similar habitats in the United States Pacific Northwest. Herbivory was negligible—less than 1% in all foliage samples.
Sequoia sempervirens (redwood) is a long-lived, shade-tolerant tree capable of regeneration without disturbances and thus often present in all sizes within a single forest. In order to evaluate functional linkages among structures, plant distribution, and biodiversity in the canopy, we quantified all vascular plants from ground level to the treetops in an old-growth redwood forest (Prairie Creek Redwoods State Park, California, USA). This involved mapping terrestrial and epiphytic trees, shrubs, and ferns as well as climbing 27 trees up to 101 m tall within a 1-ha plot. We monitored canopy microclimates using sensor arrays that collected hourly data for up to 30 months. The plot held 4283 Mg/ha of aboveground dry mass in living plants, 95.4% of which was contributed by redwood. A high degree of structural complexity and individuality was evident in the crowns of the 14 largest trees in the form of reiterated trunks arising from main trunks, other trunks, and limbs. Thirteen species of vascular plants occurred as epiphytes in the plot, and all but one of these were restricted to the 14 largest trees. The evergreen shrub Vaccinium ovatum had the highest biomass of any epiphyte (212 kg/ha) followed by the evergreen fern Polypodium scouleri (196 kg/ha). The spatial aggregation of reiterated trunks was highly coincident with epiphyte masses, explaining 92% of the variation in fern and 75% of the variation in woody plant distribution along the vertical gradient. In addition to epiphyte biomass, there were 2366 kg/ha of soil in the canopy. Soils in crotches held 2-4 times as much water as soils on branches or limbs, and deeper layers held more water than shallower layers. During two years of monitoring, the volume of water stored in dead wood and soils in the canopy fluctuated between 24.7 m3 and 53.4 m3/ha. The vast majority of the plot's structure and arboreal habitats was held in the crowns of the 14 largest trees. Reiterated trunks and limbs on a small number of trees have important ecological functions in old-growth redwood forests, and it may be feasible to accelerate the development of structural complexity and biodiversity in maturing redwood stands.
Collectively, the world's treetops are often referred to as a leafy eighth continent filled with undescribed species and ecological processes. Such phenomena are life's riddles, arranged like nested boxes to lead scientists deeper and deeper into living mystery. Since the pre-access days of canopy ecology, scientists have described many new kinds of plants and animals. Several hundred researchers worldwide have established more than 100 permanent or semi-permanent access sites across the globe to study forest canopy ecology. International expeditions, symposia, conferences, and publications are now important components of a global network for this emerging discipline. On a daily basis, canopy ecologists solve aerial puzzles and communicate this knowledge quickly to colleagues around the world. Presently, there is an urgency to quantify the world's treetops due to rapid species loss and habitat fragmentation. Foundations, universities, research centers, schools and museums, companies, scientists, and laypeople alike are investing millions of dollars into the field. As we move from qualitative to quantitative canopy studies, early signs suggest that we are losing a sense of wonder. It is especially noted in the field's battleground of terminology, the lexicon used to communicate recent discoveries and opportunities in the treetops, where prematurely entrenched viewpoints exclude or, at least, postpone, creativity and wonder.
The lack of recent critiques about terminology has led to the frequent misuse or confusingly varied use of the words that are more or less specific to the field of terrestrial canopy biology, I provide definitions for ca 170 terms and subterms, with translations into four languages. Rather than limit coverage to tree crowns, I define canopy biology as the study of life within any aboveground parts of all plant communities, temperate and tropical. This broadened perspective enables ecologists to consider the entire range of challenges faced by organisms living in aboveground plant life, from just above the rhizosphere to the outer limits of plant growth into the atmosphere. Further, this redefinition may reduce the potential for anthropocentric biases in interpreting life on trees or other plants; encourage the use of alternative ecosystems for hypotheses that may be difficult to address in treetops; and promote more general conceptual thinking about life on vegetation, most notably the importance of scaling in ecology. Among the salient points in terminology: the concept of “stratification” has been criticized in part because strata have been defined many ways, but a flexible application of the word is central to its utility; the source of nutrients is pivotal in distinguishing epiphytes from parasites, rather than the more general issue of an organism's effects on its host; “hemiepiphyte,” as currently used, confounds two radically different life cycle strategies, suggesting a new term, “nomadic vine,” to describe the strategy typical of many aroids; there is a confusion in the literature caused by varied applications of the word “climb;” locomotor terms may have to be modified as more becomes known about forces underlying limb kinematics; and studies of leaping and falling organisms tend to overemphasize arbitrary distinctions between gliding and parachuting to the detriment of the more critical issue of capacity for “controlled descent.”
Vascular epiphytes are typically associated with tropical rainforests, whereas their occurrence in temperate forests is little appreciated. This review summarises the available information on epiphytism in the temperate zones (> 23.5 latitude), which has not been reviewed omprehensively for more than a century, and critically analyses the proposed mechanisms behind the observed biogeographical patterns. Although in the temperate zone epiphytic vascular plants are rarely as impressive as in tropical forests, there are noteworthy exceptions. Temperate rain forests of Chile and New Zealand, or montane forests in the Himalayas are comparable to many tropical forests in terms of epiphyte biomass and diversity, but differ in their taxonomic spectrum temperate epiphyte communities are generally dominated by ferns and fern-allies. Other temperate areas are not, however, necessarily barren of epiphytes, as repeatedly implied. Quite in contrast, local populations of epiphytes in a large number of other non-tropical areas in both the southern and the northern hemisphere can be quite conspicuous. The proposed reasons for the latitudinal gradients in epiphyte abundance and diversity (water scarcity or low tempera-tures). are not fully convincing and, moreover, still await experimental verification. Other factors, both historical (e.g., Pleistocene extinctions) and ecological (e.g., prevalence of conifers in the northern hemisphere), should also be taken into consideration to obtain a comprehensive explanation of the extant global distribution of vascular epiphytes.
Redwood forests contain some of the largest and most structurally complex trees on Earth. The most abundant vascular epiphyte in these forests is the fern Polypodium scouleri (Polypodiaceae). We measured dimensions of all 765 P. scouleri mats on 32 trees (27 Sequoia sempervirens, 5 Picea sitchensis). Eighteen P. scouleri mats from 11 trees were randomly selected for removal and dissection in the laboratory. The total fern mat mass consisted of live fronds (3.3%), dead fronds (2.4%), live rhizomes (4.2%), dead rhizomes (8.9%), roots (34.4%), humus (28.0%), and debris (18.8%). We used multiple regression analysis to develop equations for estimation of fern masses, and we applied these equations to undisturbed fern mats on the 32 trees. Individual trees supported up to 742 kg dry mass of P. scouleri mats. These are the highest whole-tree epiphyte masses ever reported. We also quantified crown structure and counted the number of vascular plant species occurring as epiphytes on each tree. Very large, complex trees had more fern mat mass and higher vascular epiphyte species richness than smaller, simpler trees. Desiccation-sensitive organisms dependent on water stored in fern mats may be unable to survive in managed redwood forests lacking large, complex trees with abundant P. scouleri.
The epiphyte community is the most diverse plant community in neotropical cloud forests and its collective biomass can exceed that of the terrestrial shrubs and herbs. However, little is known about the role of mycorrhizas in this community. We assessed the mycorrhizal status of epiphytic (Araceae, Clusiaceae, Ericaceae, and Piperaceae) and terrestrial (Clusiaceae, Ericaceae) plants in a lower montane cloud forest in Costa Rica. Arbuscular mycorrhizas were observed in taxa from Araceae and Clusiaceae; ericoid mycorrhizas were observed in ericaceous plants. This is the first report of intracellular hyphal coils characteristic of ericoid mycorrhizas in roots of Cavendishia melastomoides, Disterigma humboldtii, and Gaultheria erecta. Ericaceous roots were also covered by an intermittent hyphal mantle that penetrated between epidermal cells. Mantles, observed uniquely on ericaceous roots, were more abundant on terrestrial than on epiphytic roots. Mantle abundance was negatively correlated with gravimetric soil water content for epiphytic samples. Dark septate endophytic (DSE) fungi colonized roots of all four families. For the common epiphyte D. humboldtii, DSE structures were most abundant on samples collected from exposed microsites in the canopy. The presence of mycorrhizas in all epiphytes except Peperomia sp. suggests that inoculum levels and environmental conditions in the canopy of tropical cloud forests are generally conducive to the formation of mycorrhizas. These may impact nutrient and water dynamics in arboreal ecosystems.
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