References

Microorganisms of Biological Crusts on Soil Surfaces 315
Fig. 5. Scheme of
alichen-dominatedsoil
crust, the soil particles
are kept together
by rhizines and rhizohyphae;
not drawn to
scale
Büdel 2001a). Their main constituents are the species Fulgensia fulgens
(Sw.) Elenk., F. bracteata (Hoffmann) Räsenen, Psora decipiens (Hedw.)
Ach., Squamarina lentigera (GH Weber) Poelt, Toninia sedifolia (Scop.)
Timdal, Catapyrenium lachneum (Ach.) R. Sant., Collema tenax (Sw.) Ach.
and often Diploschistes diacapsis (Ach.) Lumbsch.
Common lichens of biological soil crusts in xerothermic habitats worldwide
are Catapyrenium (e.g., C. cinerascens (Nyl.) Breuss, C. squamulosum
(Ach.) Breuss, C. pilosellum Breuss), Collema (e.g., C. cristatum (L.) Wigg.,
C. coccophorum Tuck.), Baeomyces (e.g., B. placophilus Ach., B. rufescens
(Huds.) Rebent.), Dibaeis (e.g., D. baeomyces (L.f.) Rambold et Hertel),
Diploschistes (e.g., D. diacapsis, D. muscorum (Her.) Zahlbr.), Endocarpon
(e.g., E. pusillum Hedwig), Fulgensia (e.g., F. bracteata, F. fulgens),
Heppia (e.g., H. despreauxii (Mont.) Tuck., H. lutosa (Ach.) Nyl., H. solorinoides
(Nyl.) Nyl., Peltula (P. patellata (Bagl.) Swinscow et Krog [Fig. 1k],
P. radicata Nyl. [Fig. 1l], P. richardssii (Herre) Wetm.), Squamarina (e.g.,
S. cartilaginea (With.) P.W. James, S. lentigera, S. concrescens (Müll.Arg.)
Poelt) and Toninia (T. sedifolia, T. toepferi (B. Stein) Navas). The crustose
chlorolichen Lecidella crystallina Vézda et Wirth (Fig. 1i), together with
hypolithic cyanobacteria, forms a soil crust that covers tens of square kilometers
in the Namib Desert (Ullmann and Büdel 2001a). As can be seen
from numerous publications, the state of research concerning the diversity
of lichen species from biological soil crusts seems to be fairly good, but,
considering the scattered investigation pattern of biological soil crusts on
the Earth, further species living in this peculiar association might well be
found.