Geoscience Reference
In-Depth Information
Figure 2-21.
Linnusaare (bird island) Bog, part of the
Endla mire complex in east-central Estonia. A sparse
pine forest grows on peat hummocks. Pine is the only
tree that can tolerate the acid water and lack of
nutrients that are typical in mature, raised bogs. This
bog is given the highest level of protection in order that
a natural environment may continue to exist without
human disturbance. Photo courtesy of J.W. Aber.
from mineral wetlands (Charman 2002). The
term peatland (American) or mire (European)
denotes those wetlands in which substantial
peat accumulation
-
at least one foot (30 cm)
-
has taken place, which is typical in bogs, fens,
and swamps. The peatland substrate is in reality
an organic structure built by biological activity.
This gives peatland depth
-
a temporal dimen-
sion that contains a record of changing environ-
ments and past climatic conditions.
In fact, bogs have been called “monuments
of nature” (Masing 1997). Natural monuments
contain in their l ora, fauna, rocks, sediments,
fossils, and landforms unique records of envi-
ronmental conditions and physical processes
that have shaped the Earth. Bogs may be con-
sidered as repositories of environmental and
climatic data through the surrogate of plant
remains, namely peat, which contains both mac-
rofossils (Fig. 2-22) and microfossils (pollen).
Indeed much of what we know about climate
and environment of the Holocene Epoch (past
10,000 years) has been gleaned from intensive
investigations of bogs.
Peat is intrinsic to many wetlands around the
world. Peat is partly decomposed plant remains
Figure 2-19.
Niobrara River in north-central Nebraska,
United States. The river channel has a sand bed, in
which bars and banks are visible through the clear
water. Photo by J.S. Aber.
Figure 2-20.
Lake Tahoe occupies a tectonic basin
formed between faults in the Sierra Nevada Mountains,
United States. The lake is over 500 m deep and covers
nearly 500 km
2
in area. Seen from Emerald Bay,
California, looking northeast toward Nevada on the
opposite side; photo by J.S. Aber.
