forest high (Pocs 1980). They serve as a substrate for
the establishment of vascular epiphytes and offer
shelter to many invertebrates and microorganisms.
Most of the bryophytes in cloud forests are epi-
phytes. Trees, treelets, shrubs, saplings, and woody
lianas are colonized by these epiphytes and epiphylls
(see Morales, "Plants Growing on Living Leaves,"
p. 80). Subtle differences in water supply, nutrients,
light, and inclination of the substrate affect the abil-
ity of bryophytes to establish themselves, so tree bases,
trunks, ascending branches, and twigs often support
different species (Richards 1984). Some occur exclu-
sively in the moist, shaded understory of the forest
("shade epiphytes"), while others are only found in
the forest canopy high above the ground ("canopy
epiphytes"). Some species have wide vertical distri-
butions in the forest and occur throughout the under-
story and the canopy ("generalists").
In forests below 1000 m, bryophyte cover is low
and mostly restricted to the canopy. Hepatics of the
family Lejeuneaceae are the most important bryo-
phytes of the lowland rain forest; about 30% of the
species are members of this family. In montane wet
forests, growth of epiphytic bryophytes is much more
luxuriant, and the forest floor may be covered with
dense bryophyte carpets. The lower temperatures
and higher light levels in the montane forests, and
the availability of plentiful water due to frequent
clouds and fog, favor the accumulation of dead or-
ganic material on the ground and the abundant
growth of bryophytes. Tree trunks and branches may
be covered with a dense fur of bryophytes up to 20
cm thick and made up of different growth forms,
including "pendents." Such taxa thrive only in per-
humid environments and are entirely absent from the
lowland rain forest.
Little work has been done on the bryophytes of
Monteverde. Reed and Robinson (1971) published a
list of 164 species (90 mosses, 73 hepatics, 1 hornwort)
based on random collecting in the forests and in pas-
ture areas. Additional species were reported by
Gradstein et al. (1994) and Sillett et al. (1995). The
latter study analyzed the epiphytic bryophyte flora in
the canopy of six Ficus tuerckheimii trees, three in the
dense forest and three isolated ones in adjacent pas-
ture land, and demonstrated that the two sets of trees
had very different species assemblages.
We conducted an inventory of bryophytes in No-
vember 1992 and January 1994 within a 4-ha study
site within the MCFP (ca. 1550m elevation; Nadkarni
1986, Nadkarni and Matelson 1992, Ingram and Nad-
karni 1993; see Ingram, "Epiphytes," pp. 72-73). Our
inventory yielded 190 bryophyte species: 133 hepat-
ics, 56 mosses, and 1 hornwort (Megaceros vincen-
tianus). The mean number of species per hectare was- In comparison, a very detailed analysis of the
canopy by Sillett et al. (1995) found 109 bryophyte
species on three Ficus tuerckheimii trees in the MCFP.
Species-area curves showed that one plot yielded 45%
of total diversity, and two plots yielded 75%. In com-
parison, when bryophyte diversity on trees only is stud-
ied (excluding shrubs, logs, etc.), the 75% level is usu-
ally obtained by analysis of only four trees (Wolf 1993).
The absolute dominance of hepatics over mosses
at the study site in terms of species number is char-
acteristic of neotropical moist forests. In paleotropical
forests, mosses tend to be more abundant (Gradstein
and Pocs 1989). Plagiochila was by far the most spe-
ciose genus (18 spp.), followed by the hepatic general
Lejeunea and Bazzania (7 spp. each), and Frullania
and Radula (6 spp.). Among the mosses, Lepidopilum
and Macromitrium (4 spp.) were the most speciose
genera, the former mainly in the understory, the lat-
ter in the canopy.
Thick branches of the lower canopy were by far the
richest habitat for bryophytes and yielded about 100
species. Trunk bases, shrubs, lianas, saplings and liv-
ing leaves were also rich in species, harboring 35-45
species. The lowest number of species (16) was found
on rotten logs; however, half of these were exclusive
to rotten logs and not found elsewhere. A similar fig-
ure was obtained for epiphylls: about half of these
species (23) were only found on living leaves; others
occurred on other substrates. Species richness in the
canopy compared to the understory was 117 versus
121, respectively. Of these, 48 (25%) occurred both
in the canopy and the understory, 38% were exclu-
sive to the understory, and 36% to the canopy. From
a conservation standpoint, the shade epiphytes of the
forest are of particular interest. They are more seri-
ously affected by forest disturbance than are sun epi-
phytes due to their lower drought tolerance and are
the first to disappear when the forest canopy is opened
up (Gradstein 1992).
Acknowledgments We thank Rodrigo Solano for
logistical support; Riclef Grolle, Andrea Lucking, Jiri
Vana, and K. Yamada for help with identifications;
and Gregorio Dauphin, who helped with the inven-
tory of the epiphylls. Fieldwork in Costa Rica by the
first author was supported by the Netherlands Foun-
dation for Tropical Research (WOTRO) and the Na-
tional Geographic Society Committee on Research
and Exploration.79 Plants and Vegetation