BOTANICAL AND ECOLOGICAL CHARACTERISTICS
SPECIES: Peltigera aphthosa | Green Dog Lichen 



GENERAL BOTANICAL CHARACTERISTICS : 
Peltigera aphthosa is a foliose lichen with a large thallus, sometimes
over 3 feet (1 m) across.  Individual lobes are up to 4 inches (10 cm)
long and 2.5 inches (6 cm) broad.  The thallus is bright green when
moist and pale smoky green when dry.  The upper surface is covered with
small cephalodia.  Apothecia are large and common [11,16,17,39].  The
mycobiont (Ascomycete) comprises the bulk of the thallus; the algal
component constitutes only 3 to 5 percent of the volume of the
structure.  Peltigera aphthosa has two photosynthetic members:  a green
alga in the genus Coccomyxa, and a blue-green cyanobacteria in the genus
Nostoc.  Both are capable of fixing carbon dioxide photosynthetically,
which may be of competitive advantage in habitats of low annual
insolation where P.  aphthosa characteristically occurs.  The Nostoc
member is contained in the cephalodia and is capable of nitrogen
fixation [1,9,14,32,37].


RAUNKIAER LIFE FORM : 
NO-ENTRY


REGENERATION PROCESSES : 
Lichen reproduction mainly occurs by means of thallus fragmentation or
the dispersal of isidia and soredia.  Wind, water, or animals play an
important role in the dispersal of these vegetative propagules [1,16].
Peltigera aphthosa also produces many large apothecia [17,39].


SITE CHARACTERISTICS : 
Lichens, including P. aphthosa, are very dependent on high relative
humidity, and their abundance is generally in direct relation to the
relative humidity.  They are better adapted to cold climates than any
other life form.  Lichens grow best in direct sun.  Since P. aphthosa is
able to take up moisture from the air, the underlying soil is not as
important a source of moisture as it is to vascular plants.  Peltigera
aphthosa can grow on shallow, sterile soils [2].  It occurs in
submontane to alpine zones on sites with subxeric to subhydric moisture
regimes [5,19,22].  Peltigera aphthosa can endure more shade than most
lichens [26].  It most commonly occurs on soil, rock, humus, moss, or
fallen log substrates in moist forests [6,11,16,32,39].  It more rarely
inhabits dry woodlands [2].


SUCCESSIONAL STATUS : 
Facultative Seral Species

Lichens in general decline in productivity and quality in older stands
[21].  Ahti [2] suggests that lichens may be pioneer plants on some
sites because they are dependent on air moisture rather than soil
moisture, and can tolerate shallow substratums.  They persist in
environments too harsh for higher plants, provided relative humidity is
sufficiently high for lichen growth and temperature is sufficiently low
to inhibit competitors.  Northern boreal forests offer climatically
optimal conditions for lichen growth because of slow rates of plant
succession and little competition from other plant forms.

Peltigera aphthosa is found in stable, mature forest ecosystems in
west-central Alberta, including climax Engelmann spruce (Picea
engelmannii)-subalpine fir (Abies lasiocarpa) habitats [5,29].  It
occurs in both old-growth (300 years) and second-growth (70 years) grand
fir (Abies grandis) habitats in the Swan Valley, Montana, but is more
abundant in the old-growth communities [25].  In Alaska, P. aphthosa is
generally not found in frequently flooded areas [30].


SEASONAL DEVELOPMENT : 
NO-ENTRY

Related categories for Species: Peltigera aphthosa | Green Dog Lichen