2. History of apothecial growth and substratal decay
A. Growth history and longevity of xerotolerant Orbiliomycetes
Apothecia
of xerotolerant species are more or less perennial due to shorter or longer
periods of dormancy in their life cycle during dry weather. Under temperate
climate apothecia of Orbiliomycetes apparently exist up to roughly a year in
the field (from immature to overmature stages) if not grazed away by animals
(see below images). In the semideserts apothecia undoubtedly persist several
years in the living state (being dry over most of the time). Tests with
herbarium specimens showed that Orbilia apothecia from semideserts
remain alive over max. 2-3 years, thereby not undergoing any maturation
processes. In semideserts, the very rare but often heavy rain permits growth
for a short period of time, thereby probably setting back the “inner clock” so
that single apothecia, at least theoretically, may even survive for several
decades.
The below
experiment shows a population of Orbilia trapeziformis sp. nov.
(Germany, Tübingen, on decorticated, 12-13 mm thick, broken branch of Juglans
regia hanging in 1.5 m above ground in a shrub) being under observation
during a period of four months. Photos were made indoor if the branch was
naturally wetted by rain; then the branch was brought outside at its original
position. Most of the time of observation the branch including the apothecia
was completely dry. Three apothecia survived the whole period of time, thereby
remaining fully alive, whilst many have disappeared, obviously by grazing of
invertebrates (such damage is a well-known problem with herbarium specimens).
|
1 7.IV.2004 |
2 28.V.2004 |
|
3 9.VII.2004 |
4 27.VII.2004 |
B. Decay history of xeric substrate: slowness of decay of dry branches
under temperate climate
Decay of
medium-sized dead branches in temperate areas (natural pruning) lasts over
roughly 10-20 years, strongly depending on the thickness of the branch,
hardness of the wood, and protection against drying wind and sunshine. In
semideserts dead branches obviously persist much longer (about 50-100 years)
until being completely decayed.
The below
experiment shows a ca. 1 m long dead branch of Quercus robur still
attached in 3.5 m above ground (Germany, Tübingen) which was accidentally
documentated in Feb. 1996 and again in Sept. 2003 and Jan. 2009. It had already
lost its bark before 1996, and its sapwood appears strongly decayed on the
foto. During 7.5 years the complete sapwood was broken away by natural decay.
Since this branch was left at its position in order to allow study of its
further decay, it was not examined for fungi so far.
|
II.1996: bark present only at base of branch, decorticated
sapwood already strongly rotten. |
Same branch, IX.2003:
all sapwood removed, surface of heartwood already strongly rotten. |
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