Baden-Württemberg - Lichens of Wales

Many lichen species are fairly substrate specific
to the extent that they are limited for the most
part on bark or wood or silicate rock or limestone
or soil and scarcely ever change over to other
substrates. A further substrate related
specialization is caused by pH conditions,
nutrient supply, water capacity (water storage
capacity) and other chemical and physical
properties of the substrate. A few examples:
Many bark lichens are limited to acid and
nutrient poor bark and therefore are found
predominately on conifer trees, others are
specialized on base-rich bark, certain rock
lichens live only on heavy-metal rich silicate
rocks, others prefer fine granular, relatively
porous calcareous rock. Very rotted wood is
floristically distinct from tough and hard wood.
pH Value
Soil- as well as bark- and rock-dwelling lichens
at times show pH characterized dependence. For
example certain lichen species occur only upon
calcareous and base rich soils, others only on
very acid.
The evidence for the critical point pHvalue
of sites colonized by the species is
supported by extensive pH-measurements with
a portable pH-meter with a flat membrane
electrode (see WIRTH 1972); they were for the
most part accomplished on site on rain moistened
or distilled water moistened substrates. The pH
conditions were described as follows:
Substrate Plants
extremely acid - pH 3.3 extreme.
acidophytic
very acid pH 3.4-4.0 very acidophytic
rather acid pH 4.1-4.8 rthr acidophytic
moderately acid pH 4.9-5.6 mod acidophytic
sub neutral pH 5.7-7.0 sub neutrophic
neutral pH 7 neutrophic
moderately basic pH 7.1-8.5 mod basic
basic over pH 7 basic
embracing a wide pH range euryion
The non eutrophic and substantially unaltered by
air pollution bark of conifers and birch is mostly
very acid (stem); of spruce and black alder rather
acid; of pear rather (-moderately) acid; of beech,
ash, apple, and basswood moderately acid; while
most poplars, Norway maples, sycamore, and
elm, moderately acid to sub neutral; and black
elder usually sub neutral.
The buffering capacity in size and range nearly
parallels the pH value: the higher the pH value
the higher the buffering capacity. The buffering
capacity attains a great significance, above all
through the onset of wide distribution of acid air
pollution, which acidifies the tree bark. A
relatively high buffer capacity possessed by the
bark of the ash, which often bears a flora, which
is typical for trees with higher pH values. The
sycamore is unchanged. Here a relatively small
buffer capacity in the case of a relatively higher
pH goes along with an often narrow acidophilic
lichen flora.
Mineral Content, Nutrient Content, and
Eutrophication
Only little is known today about mineral content
and above all about the nutrient content ( in a
narrower sense, foremost nitrogen and
phosphorus compounds) of lichen inhabited
substrates. Justifiable are statements about the
extent of eutrophication of the habitat by animal
manuring (e.g. bird roosts), by dust films (tree
bark, rocks, walls, etc.) and by mineral fertilizer
(vineyard walls). For the ecological characterization
of the lichens of this kind of habitat one
can use the relatively appropriate and neutral
expression “coniophytic” (in the case of dust
impregnation) and “coprophytic” (in the case of
animal manuring). Here is employed a known but
without doubt truly problematic term based on
the nitrogen content: “nitrophytic”; here it makes
use of, the quantity of nutrient supply to
illustrate.
Substrate: Plant:
not eutrophic anitrophytic
moderately eutrophic m. nitrophytic
(m. nutrient-rich)
rather eutrophic rthr. Nitrophytic
( rather-nutrient rich)
very eutrophic v. nitrophytic
(strongly nutrient-rich)
extremely eutrophic ext. nitrophytic
(extremely nutrient-rich)
Perhaps tree bark on the interior of extensive
forests are not eutrophic, bark of field and
avenue trees rather eutrophic, extremely etrophic
are very nitrogen-rich habitats as well as very
strongly dunged tops of bird roosts, the dog urine
impregnated base of walls, and the surfaces near
manure piles. Rock habitats naturally nutrientpoor
are not eutrophic, but not counting others in
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