adaptations for water storage, and in their ability to
absorb and retain airborne nutrients through rain,
mist, and dust. Wet neotropical montane forests, such
as the MCFP, harbor more vascular epiphyte species
and a greater abundance of epiphytes than any other
forest type (Gentry and Dodson 1987; Fig, 3.1). More
than 250 vascular epiphyte species were found in 4
ha of Monteverde Js lower montane wet forest (Ingram
et al. 1996), and many more occur in the Monteverde
area (Haber 1991; Appendix 1).
Epiphyte biomass can exceed the foliar biomass of
terrestrial herbs and shrubs in Monteverde (Nadkarni
1984). Within trees, epiphytic vegetation is most
abundant among the inner canopy branches. Of the
total amount (dry weight) of epiphytic matter held by
inner canopy branches, 50-60% consists of dead or-
ganic matter (Ingram and Nadkarni 1993). The balance
of the epiphytic matter is composed of 30-35% liv-
ing angiosperms and their roots, 5-8% ferns, and 5-
20% bryophytes (with bryophytes relatively more
abundant on smaller, younger branches of the inner
canopy). The living vegetation and associated or-
ganic matter are approximately four times more
abundant on horizontal than vertical branches, and
more abundant (per unit surface area) on larger than
smaller branches. Although small epiphytes may
grow on large branches and tree trunks, a positive
correlation exists between epiphyte size and branch
circumference. Large epiphytes on small branches do
not persist as long as they would on larger, sturdier
branches. Large bromeliads on twigs and small outer
branches frequently fall from the canopy.
True or "obligate" epiphytes (sensu Benzing 1990)
spend their entire lives perched on trees. Many ex-
hibit adaptations in growth form and habit that en-
able them to thrive in tree canopies. For example,
Anthurium scandens and Encyclia pseudopygmaea,
which have creeping growth habits and the ability to
root at leaf nodes, are common and widespread epi-
phytes in Monteverde. Orchids and bromeliads,
among the most diverse and abundant epiphyte fami-
lies, are predominantly obligate epiphytes. Faculta-

tive epiphytes, such as many Ericaceae, Araliaceae,

Alzatea verticillata (Alzateaceae), and Oerstedella

exasperata (Orchidaceae), are more adaptable and

typically grow on trees, but they may also grow along

roadcuts or in well-drained forest soil. In elfin forest

habitats, the distinction between plants growing ter-

restrially and epiphytically is least clear. Species that

grow epiphytically in the lower montane wet forest

of the Pacific slope (e.g., Schefflera rodrigueziana)

occur as free-standing trees in the elfin forest.

"Accidental" epiphytes are plants that normally

grow rooted in terrestrial soil but may occasionally

invade the arboreal soil of canopy branches and

crotches of tree trunks. In Monteverde, examples of

accidental epiphytes include Dioscorea lepida and

M/einmannia pinnata (see Putz, "Trees on Trees," p. 70).

Hemiepiphytes, or "half" epiphytes, spend part of

their life cycle rooted on trees and part rooted in the

ground. "Primary" hemiepiphytic trees and shrubs

germinate in tree crowns, grow leaves and branches

in the canopy, and eventually grow roots down to tap

nutrients in the forest soil. Strangler figs (Ficus spp.)

have numerous roots that coalesce, eventually form-

ing a "trunk" around the host tree, and finally over-

growing and killing it (see Titus, "Why Strangler Figs,"

pp. 71-72). "Secondary" hemiepiphytes (e.g., some

individuals of some species of Araceae, Cyclanthaceae,

Marcgraviaceae) start out rooted in the ground, climb

tree trunks, and later lose contact with terrestrial soil

(Lawton and Williams-Linera 1996).

The Monteverde epiphyte flora is composed of 27

angiosperm families and 13 pteridophyte (fern) fami-

lies—as many angiosperm families with epiphyte spe-

cies as are found in all of Mexico (Aguirre-Leon 1992).

Species of Orchidaceae, Pteridophyta, Bromeliaceae,

Ericaceae, Araceae, Piperaceae, and Gesneriaceae (in

decreasing order of species richness) comprise ap-

proximately 80% of the epiphyte flora (Ingram et al.

1996). Families with at least four epiphytic species

at Monteverde include (but are not restricted to) Arali-

aceae, Asteraceae, Begoniaceae, Clusiaceae, Mela-

stomataceae, and Rubiaceae (Appendix 2).

BROMELIADS

Harry E. Luther

he Bromeliaceae is a mostly neotropical,

largely epiphytic plant family with about 2750

species (Luther and Sieff 1996). The family

was last monographed as part of the Flora Neotropica

series (Smith and Downs 1974) and more recently

treated for the Central American taxa with keys and

descriptions in Spanish by Utley in Flora Meso-

americana (Davidse et al. 1994). Nearly 200 species

are recorded from Costa Rica (Luther 1995), which

includes Mexican, Central American, Andean, and

73 Plants and Vegetation

T