Grasses are all herbaceous, except for the bamboo group, and they are partic-
ularly well adapted to withstand grazing pressure since they have growing
meristems at nodes rather than at the tip, and produce stems above these nodes.
They frequently dominate in places with intense grazing pressure, and those
that have meristems below the soil surface can withstand fire.Climbers, epiphytes and stranglers all require the presence of other plants,
normally trees, for their growth and all are much more abundant in tropical
rainforests than elsewhere. Climbers occur throughout woodland habitats with
many woody climbers (lianas) in tropical forests. Many fewer occur outside
tropical rainforests but most temperate woodlands have some, e.g. Clematisspp.
Herbaceous climbers can be small and occur throughout the world, some
persisting in grasslands. In tropical rainforests, some of the tallest climbers do
not produce woody stems, or only a little secondary thickening, e.g. members of
the arum family, Araceae.
Epiphytes are dependent on a high rainfall since they only get water from it
and run-off along branches. They are abundant in tropical forests. Many ferns
and members of certain families, notably the orchids, Orchidaceae, and
bromeliads, Bromeliaceae, are specialist epiphytes but many other families are
represented. Tropical mountains have a particularly abundant epiphyte flora.
Epiphytes are common in parts of the seasonal tropics but become much rarer
and less diverse in drier climates. In temperate regions epiphytic flowering
plants only occasionally occur, although there are a few ferns. Bryophytes are
abundant epiphytes in the wet tropics, even occurring on the leaves of rainforest
trees. They are the only common epiphytes in temperate woodlands, along with
lichens. In tropical rainforests some epiphytes are shrubby, producing woody
stems and some of these develop roots which reach the ground to become
independent. The figs (Ficusspp.), are the most prominent of these stranglers
and can become self-supporting, killing the tree on which they started life.
The mistletoes (two families, Loranthaceae and Viscaceae) and a few other
plants are epiphytic in growth form but are partial parasites, penetrating their
hosts and extracting nutrients and sugars. They are considered with other
heterotrophic plants in Topic M6.Mechanically
dependent
plants
K3 – Ecology of different growth forms 173