Mountain Forests - Mountains and Plains: The Ecology of Wyoming Landscapes - page 190

Fig. 11.13. An even-aged stand of 150-year-old lodgepole pine
above centennial in the Medicine Bow Mountains. tree-ring
data suggest that this forest was initiated following a fire. the
forest understory is dominated by dwarf huckleberry. clusters

of small lodgepole pine are developing in openings. the blue
mark on the tree indicates that this tree will soon be cut,
probably for safety reasons. elevation 8,400 feet.

As with ponderosa pine forests, tree density in many
Douglas-fir stands increased during the twentieth cen-
tury as a consequence of fire suppression, grazing, and
climatic conditions favorable for tree establishment. in
some places, especially around meadows with big sage-
brush, one can see the skeletons of sagebrush that died
for lack of sunlight as the Douglas-fir expanded into the
shrubland. Recent fires and insect outbreaks also diver-
sify stand structures.

Unlike the other conifers, lodgepole pine thrives on
nutrient-poor soils (such as those that develop on gran-
ites and rhyolites) and is less common on more fertile
limestone-derived soils. 68
Lodgepole, as it is commonly called, has been viewed
as a pioneer species after fires or other severe distur-
bances, because it generally does not tolerate the forest
understory environment and is often the first tree to
become established after a disturbance, especially where
the soils are relatively dry and infertile. Under such con-
ditions, lodgepole forms what is known as an even-aged
stand of trees. in fact, tree ages may differ by 20 years
or more, but the forest clearly became established after
a widespread disturbance. As the forests age and new
gaps in the canopy are created—by localized windthrow
or other low-severity disturbances—lodgepole seedlings
can become established and grow into the canopy.
in this way, tree establishment becomes episodic and
patchy, resulting in a forest with multiple age classes.
the probability of lodgepole seedling establishment in
the forest understory appears to increase with moisture

Lodgepole Pine Forest

the most common tree in the mountain forests of
northern colorado, Wyoming, and much of the north-
ern Rockies is lodgepole pine (fig. 11.13). it usually grows
at mid-elevations—about 6,000-10,500 feet in north-
ern Wyoming and about 7,000-11,500 feet in southern
Wyoming. 67 this pine is found at higher elevations on
drier sites or in areas that have burned in the past cen-
tury or two. engelmann spruce and subalpine fir may
be co-dominant with lodgepole on relatively moist sites.