共查询到20条相似文献,搜索用时 15 毫秒
1.
Rodrigo S. P. de Skowronski Paula F. Gheller Sandra Bromberg Carlos J. David Mônica A. V. Petti Thaïs N. Corbisier 《Polar Biology》2009,32(6):839-851
The spatial and temporal variation of microphytobenthic biomass in the nearshore zone of Martel Inlet (King George Island,
Antarctica) was estimated at several sites and depths (10–60 m), during three summer periods (1996/1997, 1997/1998, 2004/2005).
The mean values were inversely related to the bathymetric gradient: higher ones at 10–20 m depth (136.2 ± 112.5 mg Chl a m−2, 261.7 ± 455.9 mg Phaeo m−2), intermediate at 20–30 m (55.6 ± 39.5 mg Chl a m−2, 108.8 ± 73.0 mg Phaeo m−2) and lower ones at 40–60 m (22.7 ± 23.7 mg Chl a m−2, 58.3 ± 38.9 mg Phaeo m−2). There was also a reduction in the Chl a/Phaeo ratio with depth, from 3.2 ± 3.2 (10–20 m) to 0.7 ± 1.0 (40–60 m), showing a higher contribution of senescent phytoplankton
and/or macroalgae debris at the deeper sites and the limited light flux reaching the bottom. Horizontal differences found
in the biomass throughout the inlet could not be clearly related to hydrodynamics or proximity to glaciers, but with sediment
characteristics. An inter-summer variation was observed: the first summer presented the highest microphytobenthic biomass
apparently related to more hydrodynamic conditions, which causes the deposition of allochthonous material. 相似文献
2.
Mads S. Thomsen Thomas Wernberg Peter A. Stæhr Morten F. Pedersen 《Helgoland Marine Research》2006,60(1):50-58
Sargassum muticum was first observed in Scandinavia in Limfjorden (Denmark) in 1984, where it is now the most abundant and conspicuous macroalga.
Despite the ecological importance of Sargassum, few studies have described seasonal patterns within Scandinavian Sargassum beds. We quantified the dynamics of macroalgae among years and seasons along a depth transect through a typical Sargassum bed in Limfjorden. The annual investigations (summer transects 1989–1999) showed a gradual increase in the dominance of Sargassum, especially at the 2–4-m depth interval. Significant seasonal dynamics in macroalgal abundance and assemblage structure were
observed in this depth interval; the mean cover of Sargassum varied from ca. 5% (autumn and winter) to 25% (mid-summer). In comparison, encrusting algae had high and relatively stable
covers throughout the year (ca. 20%). Other perennial macroalgae had low mean covers (<2%) characterized by a few patches
of higher abundances. Except from a spring bloom, filamentous algae had low covers throughout the year. Within this relatively
uniform bed, Sargassum abundance was positively related to boulders >10 cm in diameter and species richness was negatively correlated to depth and
stones <10 cm in diameter, and non-correlated to other algal form-groups or grazer densities. Thus, in Limfjorden, the distribution
of Sargassum is determined by large- (>6 m) and small-scale (<1 m) depth differences where low light limits Sargassum at depth, physical disturbance and sediment stress limits Sargasum in shallow waters, and the presence of stable boulder substratum facilitate Sargassum. Competition for space from other macroalgae and herbivory are probably of minor importance. 相似文献
3.
Emma L. Johnston Sean D. Connell Andrew D. Irving Adele J. Pile Bronwyn M. Gillanders 《Polar Biology》2007,30(6):781-788
Studies of east Antarctic marine assemblages on hard substrata are rare. In relation to sea-ice breakout, we assessed benthic
patterns of habitat and inhabitants between islands and bays at each of two depths (6 and 12 m) across the Windmill Islands
coast. Island sites experience sea-ice breakout in the austral spring, while bay sites typically retain sea-ice cover into
the summer and in some places the cover is virtually permanent. Composition of assemblages differed between sheltered bays
and exposed islands. Islands were dominated by macroalgae, which also varied with depth. Immediately below the ice–foot zone
at 6 m, substratum space were monopolised by foliose red (Palmaria
decipiens) and foliose brown (Desmarestia sp.) algae, whereas at 12 m large canopies of Himantothallus
grandifolius was abundant. The understorey consisted of a mixture of turfs and encrusting red algae at 6 m, and coralline algae at 12 m.
Sheltered bays had large areas of sediment/algal complex and no canopy-forming macroalgae. We found more sponges and hydroids
in bays, and more brittle stars around islands. Experiments testing factors that covary with exposure and depth in Antarctica,
such as light, sedimentation and ice scour are necessary to determine processes that maintain these striking patterns. 相似文献
4.
Dr. R. Pamela Reid Dr. Ian G. Macintyre Dr. Kathleen M. Browne Dr. Robert S. Steneck Dr. Timothy Miller 《Facies》1995,33(1):1-17
Summary Modern stromatolites in open marine environments, unknown until recently, are common throughout the Exuma Cays, Bahamas. They
occur in three distinct settings: subtidal tidal passes, subtidal sandy embayments and intertidal beaches. These stromatolites
have a relief of up to 2.5 m and occur in water depths ranging from intertidal to 10 m. Surfaces near the sediment-water interface
are typically colonized by cyanobacterial mats, whereas high relief surfaces are commonly colonized by algal turf and other
macroalgae such asBatophora, Acetabularia, andSargassum. The internal structure of the stromatolites is characterized by millimeter-scale lamination defined by differential lithification
of agglutinated sediment. In thin section, the lithified laminae appear as micritic horizons with distinct microstructures:
they consist of thin micritic crusts (20–40 μm thick) overlying layers of micritized sediment grains (200–1000 μm thick);
the micritized grains are cemented at point-contacts and are trucated along a surface of intense microboring. The Exuma stromatolites
are built by cyanobacterial-dominated communities. These laminated prokaryotic structures grade to unlayered thrombolites
built by eukaryotic algae. The variety of sites, settings and shapes of stromatolites in the Exuma Cays present excellent
opportunities for future studies of stromatolite morphogenesis. 相似文献
5.
Benthic algal communities can play an important role in matter and energy flux of shallow lakes. Their contribution to total
primary production of lakes has been largely unexplored. The aim of this study was to estimate the primary production of the
epipsammic algal communities at different water depths in Lake Balaton (Hungary) with photosynthetic measurements performed
in laboratory. The photosynthesis of the benthic algae of different origin was studied at nine different irradiance levels,
in three replicates. The maximum photosynthetic rate (P
max) was always higher in samples from the shallow parts than those from the deeper regions of the lake. Along the west–east
longitudinal axis of the lake P
max decreased in the southern part and increased in the middle of the lake as a consequence of differences in the chlorophyll-a concentrations. Knowing P
max, I
k, global radiation and extinction coefficient, the primary production (mg C m−2 day−1) of the epipsammic algal community was calculated at different water depths. In the shallow regions at 0.5 and 1 m water
depth 75–95% and 60–85% of the production was attributable to the epipsammon. The percentage contribution of epipsammon was
at 2 m water depth 20–65%. In the deeper pelagic region (>3 m) more than 85% of the primary production originated from the
phytoplankton. 相似文献
6.
Impact of chronic and pulse dilution disturbances on metabolism and trophic structure in a saline Mediterranean stream 总被引:1,自引:0,他引:1
Cayetano Gutiérrez-Cánovas Juan Hernández Andrés Millán Josefa Velasco 《Hydrobiologia》2012,684(1):225-239
Non-diatom benthic algae from 104 streams in southern California were studied. We present a novel method for quantification
of non-diatom algae that seeks to improve upon two important aspects of existing methods: separate processing of macroalgae
and microalgae to avoid sample blending and consequent loss of macroalgal integrity, and for better viewing, counting a well-mixed
microalgal subsample on a standard microscope slide instead of using a counting chamber. Our method provided high-quality
taxonomic and quantitative data with low uncertainty. A total of 260 algal taxa were recorded, 180 of which were identified
to species level. The median total algal biovolume per site was 22.7 mm3 cm−2 (range: <0.001–836.9 mm3 cm−2), the median species number was 11 (range: 2–43). Total algal biovolume and species number correlated with canopy cover (negative)
and water temperature (positive), but not with measured water chemistry constituents. The proportion of heterocystous cyanobacteria
and Zygnemataceae were strongly negatively correlated with nitrate concentrations and TN. The proportion of red algae was
negatively correlated with TP. Species optima calculations combined with indicator species analysis identified >40 algal species
as potential indicators of nutrient conditions. Proposed here is a practical tool for non-diatom algal quantification that
enhances its application to stream bioassessment. 相似文献
7.
Seasonal Variation in the Chemical Composition of Tropical Australian Marine Macroalgae 总被引:1,自引:0,他引:1
The proximate chemical composition (ash, soluble carbohydrate, lipid and protein) was determined in 30 common species of tropical Australian marine macroalgae from Darwin Harbour (12∘26′S, 130∘51′E), in summer (hot and wet) and winter (cool and dry). There was a wide diversity of species in both seasons (19 species in summer and 20 species in winter). In most species, the major component was soluble carbohydrate (chlorophytes range 2.5–25.8% dry weight (dw), phaeophytes range 8.4–22.2% dw, rhodophytes range 18.7–39.2% dw) with significantly higher (p < 0.05) percentages only in winter season rhodophytes. Highest percentages of protein were found in rhodophytes collected in the summer (range 4.8–12.8% dw), with significantly lower percentages (p < 0.05) during winter. All species had lipid contents within the range 1.3–7.8% dw, with highest percentages in summer phaeophytes, but no significant differences between species or season. Most species had moderate to high ash contents (24.2–89.7% dw), with the highest percentages during summer. Compared with summer samples, macroalgae collected in winter had higher energy value and slightly lower percentages of inorganic matter. The variation of algal groups and chemical composition may influence the availability of the food source for the majority of herbivores, which in turn is likely to effect their ecology and community structure. 相似文献
8.
Gianluca Piovesan Emanuele Presutti Saba Franco Biondi Alfredo Alessandrini Alfredo Di Filippo Bartolomeo Schirone 《Plant Ecology》2009,205(1):23-46
Understanding the ecological mechanisms that allow a species to transition from an occasional understory component to the
dominant type in the forest canopy is essential for predicting future shifts in the distribution of species. We investigated
this issue with regard to yew, also because mature yew trees have been reported to inhibit self-regeneration and seedling
survival, prompting concerns for the long-term preservation of the species. Our objectives were (a) to quantify spatial patterns
of yew (Taxus baccata L.) populations near the southern limit of the species’ ecological distribution, (b) to determine the relationships between
yew presence and topographic gradients, and (c) to answer the question of how yew regeneration is affected by such patterns
and relationships. We analyzed three extensive yew populations (90–165 ha, including 3–12 thousand established individuals)
that mostly occupy the understory of beech forests located in protected areas of the central Apennines (Italy). Overall, the
realized niche of yew (either as established trees, saplings, or seedlings) followed the expected bell-shaped curve of a species
response to an environmental gradient. Yew was mainly found at 1,000–1,600 m elevation on mesic exposures (north and west)
and intermediate slopes (30–60%). Geostatistical analysis revealed that yew occurred in patches, as shown by variogram ranges
of 40–110 m for yew tree basal area and regeneration abundance. Yew regeneration over the landscape was directly related to
basal area of yew trees. At local scales (~10 m), presence of established trees favored regeneration in relatively less developed
stands, whereas high density of mature yews suppressed regeneration. Healthy yew populations in beech forests had a minimum
size of 0.5–3 ha. As yew density increased within these patches, regeneration dropped, so that yew conservation cannot be
limited to presently occurring populations, despite the longevity and potential for vegetative reproduction of the species.
Disturbance from grazing and wildfire was also found to impact yew survival. Long-term existence of yew in the Italian Apennines
depends on maintaining and expanding old-growth beech forests that incorporate yew patches, and have a minimum continuous
cover equivalent to a relatively undisturbed regime (10–50 ha). 相似文献
9.
F. Riget E. Jeppesen F. Landkildehus T. L. Lauridsen P. Geertz-Hansen K. Christoffersen H. Sparholt 《Polar Biology》2000,23(8):550-558
Landlocked Arctic charr (Salvelinus alpinus) populations in sub-Arctic and Arctic Greenland lakes were sampled with multi-mesh-sized survey gillnets. The study covered
a range of small shallow lakes (0.01 km2, maximum depth <3.3 m) to large deep lakes (43 km2, maximum depth >200 m). Arctic charr were found in one to three different forms in lakes with maximum depths >3 m. A dwarf
form occurred in all lakes inhabited by Arctic charr and was the only form in lakes with maximum depths <8 m. In deeper lakes
with maximum depths >20 m and a surface area <0.5 km2, larger charr were found, although in low numbers, the length-frequency distribution being unimodal with a tail towards large
sizes. In lakes with a maximum depth >20 m, large-sized charr were more abundant, and the length-frequency distribution of
the population was bimodal, with a first mode around 10–12 cm and a second mode around 26–37 cm. In a single large and deep
lake, a distinct medium-sized pelagic zooplankton-eating charr form occurred. Maximum size of individual charr was significantly
positively correlated with lake maximum depth and volume, and the mean size of large-sized charr was significantly positively
correlated with lake volume. Our study indicates that the charr population structure became more complex with increasing lake
size. Moreover, the population structure seemed to be influenced by lake-water transparency and the presence or absence of
three-spined stickleback (Gasterosteus aculeatus).
Accepted: 31 January 2000 相似文献
10.
We describe endorhizal fungi associated with Equisetum species collected from Ellesmere Island (82°N), Axel Heiberg Island (80°N), and from sites in Yukon Territory and the Prairie
Provinces (51–67°N). Fungal colonization was assessed using a multiple quantitation microintersect method for lactofuchsin-stained
roots examined with wide-field and confocal epifluorescence microscopy. Equisetum roots host abundant and diverse endorhizal fungal associates. For 85 specimens from 14 sites, total colonization averaged
30 ± 3%, range 0–97%. Colonization rates for wide aseptate hyphae characteristic of arbuscular mycorrhizae (5 ± 1%) was significantly
less than for fine endophytes (20 ± 3%) or septate endophytes (17 ± 2%). Equisetum spp. are abundant in tundra and an important understory plant in boreal forests, where they are particularly common on burned
or disturbed sites. Endorhizal fungi associated with Equisetum may have broad ecological relevance. 相似文献
11.
Karibu Fukuzawa Hideaki Shibata Kentaro Takagi Fuyuki Satoh Takayoshi Koike Kaichiro Sasa 《Ecological Research》2007,22(3):485-495
We measured the vertical distribution and seasonal patterns of fine-root production and mortality using minirhizotrons in
a cool–temperate forest in northern Japan mainly dominated by Mongolian oak (Quercus crispula) and covered with a dense understory of dwarf bamboo (Sasa senanensis). We also investigated the vertical distribution of the fine-root biomass using soil coring. We also measured environmental
factors such as air and soil temperature, soil moisture and leaf area indices (LAI) of trees and the understory Sasa canopy for comparison with the fine-root dynamics. Fine-root biomass to a depth of 60 cm in September 2003 totaled 774 g m−2, of which 71% was accounted for by Sasa and 60% was concentrated in the surface soil layer (0–15 cm), indicating that understory Sasa was an important component of the fine-root biomass in this ecosystem. Fine-root production increased in late summer (August)
when soil temperatures were high, suggesting that temperature partially controls the seasonality of fine-root production.
In addition, monthly fine-root production was significantly related to Sasa LAI (P<0.001), suggesting that fine-root production was also affected by the specific phenology of Sasa. Fine-root mortality was relatively constant throughout the year. Fine-root production, mortality, and turnover rates were
highest in the surface soil (0–15 cm) and decreased with increasing soil depth. Turnover rates of production and mortality
in the surface soil were 1.7 year−1 and 1.1 year−1, respectively. 相似文献
12.
Our objective was to evaluate the relative importance of gradients in light intensity and the isotopic composition of atmospheric
CO2 for variation in leaf carbon isotope ratios within a Pinus resinosa forest. In addition, we measured photosynthetic gas exchange and leaf carbon isotope ratios on four understory species (Dryopteris carthusiana, Epipactus helleborine, Hieracium floribundum, Rhamnus frangula), in order to estimate the consequence of the variation in the understory light microclimate for carbon gain in these plants.
During midday, CO2 concentration was relatively constant at vertical positions ranging from 15 m to 3 m above ground. Only at positions below
3 m was CO2 concentration significantly elevated above that measured at 15 m. Based on the strong linear relationship between changes
in CO2 concentration and δ13C values for air samples collected during a diurnal cycle, we calculated the expected vertical profile for the carbon isotope
ratio of atmospheric CO2 within the forest. These calculations indicated that leaves at 3 m height and above were exposed to CO2 of approximately the same isotopic composition during daylight periods. There was no significant difference between the daily
mean δ13C values at 15 m (–7.77‰) and 3 m (–7.89‰), but atmospheric CO2 was significantly depleted in 13C closer to the ground surface, with daily average δ13C values of –8.85‰ at 5 cm above ground. The light intensity gradient in the forest was substantial, with average photosynthetically
active radiation (PAR) on the forest floor approximately 6% of that received at the top of the canopy. In contrast, there
were only minor changes in air temperature, and so it is likely that the leaf-air vapour pressure difference was relatively
constant from the top of the canopy to the forest floor. For red pine and elm tree samples, there was a significant correlation
between leaf δ13C value and the height at which the leaf sample was collected. Leaf tissue sampled near the forest floor, on average, had
lower δ13C values than samples collected near the top of the canopy. We suggest that the average light intensity gradient through the
canopy was the major factor influencing vertical changes in tree leaf δ13C values. In addition, there was a wide range of variation (greater than 4‰) among the four understory plant species for average
leaf δ13C values. Measurements of leaf gas exchange, under natural light conditions and with supplemental light, were used to estimate
the influence of the light microclimate on the observed variation in leaf carbon isotope ratios in the understory plants.
Our data suggest that one species, Epipactus helleborine, gained a substantial fraction of carbon during sunflecks.
Received: 21 March 1996 / Accepted: 13 August 1996 相似文献
13.
Seasonal and spatial patterns of light availability were investigated in the understory of a small fragment (approximately
1300 m2) of a riparian deciduous forest of the Kokai River in central Japan dominated byQuercus acutissima Carruth., with the aim to understand the characteristics of microsite light availability forArisaema heterophyllum Blume, a threatened plant species uniquely associated with the riparian habitat. Diffuse site factor, which is the ratio
of PFD (photon flux density, 400–700 nm) at a microsite to the open sky reference under diffuse light condition, was shown
to be a satisfactory index for the evaluation of light availability for the understory plants in the habitat. Diffuse site
factor 1,0 1,000 understory microsites along a 20 m transect from the edge to the interior of the forest, showed conspicuous
seasonal changes in both mean and variation. Light availability decreased with seasonal tree canopy regeneration, with the
highest spatial heterogeneity being recorded during the time of canopy closure. Auto-correlations of microsite light availability
between different seasons were considerably high, suggesting the stability of relative light availability for individual microsites
throughout the growing season ofA. heterophyllum. Fairly high light availability during summer season, which surpassed 20% of the open sky reference in most microsites, would
be important for the growth and persistence of summer herbaceous plants likeA. heterophyllum. 相似文献
14.
The role of roots penetrating various undisturbed soil horizons beneath loose layer in water use and shoot growth of maize
was evaluated in greenhouse experiment. 18 undisturbed soil columns 20 cm in diameter and 20 cm in height were taken from
the depths 30–50 cm and 50–70 cm from a Brown Lowland soil, a Pseudogley and a Brown Andosol (3 columns from each depth and
soil). Initial resistance to penetration in undisturbed soil horizons varied from 2.5 to 8.9 MPa while that in the loose layer
was 0.01 MPa. The undisturbed horizons had a major effect on vertical arrangement of roots. Root length density in loose layer
varied from 96 to 126 km m-3 while in adjacent stronger top layers of undisturbed horizons from 1.6 to 20.0 km m-3 with higher values in upper horizons of each soil. For specific root length, the corresponding ranges were 79.4–107.7 m g-1 (on dry basis) and 38.2–63.7 m g-1, respectively. Ratios of root dry weight per unit volume of soil between loose and adjacent undisturbed layers were much
lower than those of root length density indicating that roots in undisturbed horizons were produced with considerably higher
partition of assimilates. Root size in undisturbed horizons relative to total roots was from 1.1 to 38.1% while water use
from the horizons was from 54.1 to 74.0%. Total water use and shoot growth were positively correlated with root length in
undisturbed soil horizons. There was no correlation between shoot growth and water use from the loose layers. 相似文献
15.
We quantified patterns of vegetation removal and light availability above Atta colombica nests on Barro Colorado Island, Panama. Ants cleared vegetation less than 1 cm in diameter from an area of 77 m2, and up to 3 m above ground level. Overall light availability 1.5 m above ground level was 49 percent greater at ant nest sites than at sites in undisturbed understory. These higher light levels fell within the range known to enhance growth of both shade tolerant and pioneer species. 相似文献
16.
I. K. Rivier 《Inland Water Biology》2012,5(3):274-280
The morphological and biological features of Bythotrephes—a relatively rare crustacean in Lake Pleshcheevo—have been identified on the basis of vast material (several hundreds of individuals) collected in August 2010. The individuals were distinguished by a minimal body size, short caudal appendix, absence of a loop, and very small caudal claws and were identified as Bythotrephes brevimanus Lilljeborg, 1901. The morphology of the crustacean corresponds to the high water mineralization in the lake and the relative stability of the environment. Some peculiarities of molt and growth of the crustacean were distinguished. A chitinous integument of the caudal appendix formed during embryogenesis has a different structure than chitin formed during further molts. In August, the population of B. brevimanus in different areas of the lake was stable and consisted only of juveniles and parthenogenetic females (80%) (4–6 eggs). The largest number of crustaceans (150 ind./m3) was recorded in the periphery of the depression above depths of 6–7 m; 80 ind./m3 were recorded above depths of 11–12 m; and, above the depression, there were less than 30 ind./m3. The small density of crustaceans in the pelagial depends on the intensive grazing of this food object selected by fish in especially transparent water (color 15–20 and transparency 300–600 cm). 相似文献
17.
Yutaka Watanuki Akiko Kato Yasuhiko Naito Graham Robertson Sue Robinson 《Polar Biology》1997,17(4):296-304
The diving and foraging behaviours of Adélie penguins, Pygoscelis adeliae, rearing chiks at Hukuro Cove, Lützow-Holm Bay, where the fast sea-ice remained throughout summer, were compared to those
of penguins at Magnetic Island, Prydz Bay, where the fast sea-ice disappeared in early January. Parent penguins at Hukuro
Cove made shallower (7.1–11.3 m) but longer (90–111 s) dives than those at Magnetic Island (22.9 m and 62 s). Dive duration
correlated with dive depth at both colonies (r
2 = 0.001 ∼ 0.90), but the penguins atg Hukuro Cove made longer dives for a given depth. Parents at Hukuro Cove made shorter
foraging trips (8.1–14.4 h) with proportionally longer walking/swimming (diving < 1 m) travel time (27–40% of trip duration)
and returned with smaller meals (253–293 g) than those at Magnetic Island, which foraged on average for 57.2 h, spent 2% of
time walking/swimming ( < 1 m) travel, and with meals averaging 525 g. Trip duration at both colonies correlated to the total
time spent diving. Trip duration at Hukuro Cove, but not at Magnetic Island, increased as walking/swimming ( < 1 m) travel
time increased. These differences in foraging behaviour between colonies probably reflected differences in sea-ice cover and
the availability of foraging sites.
Received: 3 November 1995/Accepted: 29 May 1996 相似文献
18.
19.
Time-depth recorders were deployed on immature hawksbill turtles at the southwestern reefs of Mona Island, Puerto Rico, to
examine patterns of diving behavior. Diving profiles of 10–12 day duration were obtained from five turtles ranging in carapace
length from 27–52 cm. Turtles exhibited contrasting diurnal and nocturnal diving behaviors. During daylight hours, dives were
made 92% of the time, featured continuous depth variation and were attributed to foraging activity. Foraging dive duration
increased with turtle size; individual mean dive durations ranged from 19–26 min; mean post-dive surface intervals ranged
from 37–64 s; mean depths ranged from 8–10 m. At night, dives were made 86% of the time to constant depths and were interpreted
as resting behavior. Resting dive durations were not dependent on turtle size; individual mean dive durations ranged from
35–47 min; mean post-dive surface intervals ranged from 36–60 s; and mean depths from 7–10 m. Immature hawksbill turtles maintained
short term home ranges several hundred meters in extension.
Accepted: 2 July 1996 相似文献
20.
We studied species richness, composition, and vertical distribution of vascular epiphytes at two sites in the Bolivian Andes.
To account for the epiphyte flora on understory trees, epiphytes on shrubs and small trees were sampled in 20 × 20 m2 subplots around each sampled canopy tree; this understory zone U is introduced as an addition to the well-established five
vertical Johansson tree zones. More than 20% of about 500 species recorded were found only in the understory subplots, including
ca. 40% of aroids, 35%–40% of piperoids, and 25%–30% of ferns. Habitat generalists (occurring in three or more zones) were
most common, contributing about 50% of all species, specialists (occurring only in two zones, or in three continuous ones)
34%–42%, and hemiepiphytes 6%–16%. Canopy epiphytes (occurring > 90% in tree zones Z3–5) were mainly represented by orchids
and ferns, many with special adaptations to drought stress such as pseudobulbs, succulence, and poikilohydry. Trunk epiphytes
( > 90% in understory and tree zones Z1–2) reached highest relative species numbers among piperoids and ferns. Most hemiepiphytes
were also trunk epiphytes, due to their characteristic growth pattern, and included mainly aroids. The vertical distribution
of epiphytes within a tree is determined by several microenvironmental gradients, with light intensity, wind speed, and air
temperature increasing and air humidity decreasing from the ground level to the canopy. 相似文献