Biology Reference
In-Depth Information
of North America (Sollins
et al
., 1980). Old-growth forests are considered to be important natural
havens for many epiphytic macrolichen communities. The biomass of old-growth associated lichens
increases slowly in the old-growth conifer forests of Pacifi c North West of North America where
the cyanolichens can exceed 1 T ha
-1
of biomass (McCune, 1993; Sillett, 1995; Neitlich and McCune,
1997). Besides fi xing nitrogen, the cyanolichens also adsorb nitrogen from the atmosphere and
ultimately release it into their immediate environment. Thus they are considered to contribute
signifi cantly to the nitrogen budgets of some ecosystems in different geographical areas such as
Sweden (Kallio, 1974; Huss-Danell, 1977), North Carolina (Becker
et al
., 1977; Becker, 1980), Columbia
(Forman, 1975), Chile (Godoy
et al
., 2001) and British Columbia (Campbell and Fredeen, 2004).
Epiphytic cyanolichens probably make signifi cant contribution specially in some coniferous forests
where nitrogen is limiting (Rhoades, 1995; Nash, 1996). Goward and Arsenault (2000a) identifi ed
31 epiphytic (tree-dwelling) cyanolichens colonizing conifers in the intermontane forests of British
Columbia. Of these, at least 12 species are considered to be rare. Maximum diversity of cyanolichens
was encountered in lowland old-growth rain forests specially the wettest subzones of the Interior
Ceder-Hemlock zone. A signifi cant component of lichen diversity in the humid coastal forests of
Nova Scotia is represented by the cyanolichens (Casselman and Hill, 1995; Seaward
et al.
, 1997).
Most common species represented are those of
Lobaria
as well as
Collema subfl accidum
,
Leptogium
cyanescens
and
Parmeliella triptophylla
. The rare species are represented by
Coccocarpia palmicola
,
Degelia
plumbea
,
Erioderma pedicellatum
,
Leptogium corticola
,
L
.
laceroides
,
L
.
saturinum
,
Nephroma
laevigatum
,
N
.
helveticum
,
Pannaria conoplea
,
Pseudocyphellaria perpetua
and
Sticta fuliginosa
. Studies on total
epiphyte cover, spatial distribution and succession of epiphytes of
Tsuga heterophylla
(western
hemlock) in an old-growth Douglas-fi r forest brought to light that foliose macrolichens
Lobaria
,
Pseudocyphellaria
and
Sticta
were most abundant in the lower and mid canopy regions (Lyons
et al
.,
2000). The abundance of
Lobaria pulmonaria
in the Interior Cedar-Hemlock forests of east-central
British Columbia correlated very well as an indicator species to assess the diversity with stand
age and the functional role of dominant species in the ecosystem. The increase in the density of
L
.
pulmonaria
populations along with other cyanolichens is expected to play a predominant role in
maintaining the nitrogen budget where atmospheric nitrogen deposition is relatively low in this
region (Campbell and Fredeen, 2004).
Cyanolichens are late colonists in the sequence of stand development and they are found on
the relatively older lower branches and inner branch regions. This is supported by the total biomass
that is greatest in the mid canopy where large branches are present. Canopy lichen abundance of
regenerating hemlock forests (
Tsuga heterophylla
) in wet temperate rain forests of central-interior
British Columbia has been surveyed. Cyanolichen taxa such as
Nephroma helveticum
,
Sticta fulginosa
and
Pseudocyphellaria anomala
reached their abundance at mid-canopy (12-24 m) positions. The
abundance of smaller cyanolichen thalli in regenerating hemlock forests casts doubt as to whether
these represent cyanolichen thalli facing severe growth constraints or were simply thalli that
experienced greater fragmentation. It is concluded that the 120-140 year old hemlock forests have
not yet attained suffi cient old-growth characteristics to support the growth of cyanolichens (Radies
and Coxson, 2004).
One of the world's tallest and most massive forests containing as many as 20 conifer species
exceeding in 60 m in height are situated in the west coast of North America (Van Pelt, 2001). These
constitute the temperate rain forests that at one time extended from Alaska to California. A number
of workers have explored lichen biogeography in the region of California forests covering wilderness
areas, national and state parks, watersheds and broader geographic regions. One of the tallest rain
forest species is
Sequoia sempervirens
(coast redwood) besides
Picea sitchensis
(Sitka spruce) that support
