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subdivision between family and genus) Espe-
letiinae (family Asteraceae), commonly known
as frailejóns, which includes eight genera and
nearly 140 named species (Diazgranados 2009).
They are highly endemic; many species are
found only in a single páramo locale along the
Andes in Colombia, Venezuela and, to a lesser
extent, Ecuador. Frailejón grande (
Coespeletia
moritziana
) and frailejón pequeño (
Espeletia
schultzii
) are typical in the Venezuelan páramo
(Ruiz 1992). Frailejóns are peculiar plants with
thick, woody stems and leaf rosettes at the top.
They display diverse growth habits, and in some
locations they comprise more than 40% of the
vegetation cover (Fig. 17-7). Frailejóns have
great ecological importance for the páramo, as
they regulate the hydrologic cycle, produce the
most biomass, prevent soil erosion, and are
associated with more than 125 animal species
(Diazgranados 2009).
Climatic l uctuations associated with Pleis-
tocene glacial-interglacial cycles resulted in ver-
tical shifts of vegetation zones, particularly
marked by the forest-páramo boundary. For
example, on the high plain of Bogotá, Colombia
(
2600 m), forest and páramo alternated some
15-20 times during the past one million years
(Luteyn 2011). During the last glacial maximum
(late Pleistocene), alpine glaciers advanced
downslope even into forested zones, and then
between 21,000 and 14,000 years ago glaciers
receded and climate became quite cold and dry
with mean annual temperature 6-7 °C lower
than today (Luteyn 2011). During this interval
the páramo was continuous over long distances
above 2000 m. The end of the Pleistocene
brought warming and further recession of gla-
ciers, continuing into the middle Holocene,
when the forest-páramo boundary rose about
300-400 m higher than today. Late Holocene
cooling caused the forest-páramo boundary to
descend to its current position, resulting in
many disjunct (isolated) páramo locales.
Much of the modern páramo is heavily inl u-
enced by human activity, particularly during
the past three centuries (Luteyn 2011). The
greatest alteration is at the forest-páramo
boundary, where logging has reduced the forest.
The páramo is used primarily for cattle and is
maintained by cutting, periodic burning, and
grazing (see Fig. 1-5). The alpine water resources
are diverted from streams and carried in pipe-
lines to lower valleys (Fig. 17-8), where the
water is used for human consumption, hydro-
power and irrigation. The tropical climate allows
continuous grazing and multiple yearly harvests
of potatoes, carrots, and other crops.
∼
A
B
17.3 Southern Colorado, United States
The Rocky Mountain region in southern Colo-
rado includes several distinct mountain ranges
and intervening valleys (Fig. 17-9), in which
elevations range from around 7500 feet (2300 m)
to
Figure 17-7.
Frailejón alpine vegetation in the
Venezuelan Andes Mountains. A. Frailejón plants cover
the steep slope in the foreground, vicinity of Pico Águila.
Photo by J.S. Aber. B. Close-up view of frailejón plants,
Páramo de Piedras Blancas. Modii ed from original
photo by P.M. Vásconez; obtained from Wikimedia
Commons
<
http://commons.wikimedia.org/
>
.
14,000 feet (4260 m). Following long-lasting
tectonic activity during the early and middle
Cenozoic, the present elevation and relief of the
region was brought about by vertical uplift of
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