IV. DESERT ALGAE, LICHENS, AND FUNGI
173
darker, reddish, blackish, or brownish. Some algal crusts show a fuzzy
growth due to the presence of filamentous blue-green algae. (3) Lichen
soil crusts are usually more conspicuous than raincrusts or algal soil crust,
their structure is dense and they may attain 2-5 cm thickness. Their color
is dark brownish, blackish, or, after rains, greenish, retaining moisture for
a longer period than algal soil crusts. Lichen soil crusts often become
folded and reticulate, extending above the soil surface and separating from
the substrate. According to Cameron and Blank (1966), the algal components are most frequently Schizothrix calcicola (Ag.) Gom., Microcoleus chtonoplastes (Mert.) Zanard., and Microcoleus vaginatus (Vauch.)
Gom. They also point out that "most of the algae in Southwestern United
States desert soil crusts tend to become parasitized, eventually developing
into distinctive crustose soil lichens." This however does not seem to be
the case in more arid deserts, such as the Sahara (Killian, 1953) or in
the Negev. In the Negev, Friedmann et al. (1967), Friedmann and
Ocampo-Paus (1965, 1966), Ocampo-Paus and Friedmann (1966), and
R. Ocampo (unpublished) found the following species in thin evanescent nonlichenized algal crusts: Bracteacoccus minor (Chodat) Petrovâ
var. desertorum Friedmann et Ocampo-Paus, Chlorosarcinopsis eremi
Chantanachat et Bold, Chlorosarcinopsis negevensis fa. negevensis Friedmann et Ocampo-Paus, Chlorosarcinopsis negevensis fa. ferruguinea
Friedmann et Ocampo-Paus, Protosiphon botryiodes, (Kütz.) Klebs, Radiosphaera negevensis fa. negevensis Ocampo-Paus et Friedmann, Radiosphaera negevensis fa. minor Ocampo-Paus et Friedmann, Oscillatoria sp.,
and Botrydium granulatum (L.) Grev.
In the South African desert, Vogel (1955) describes two distinctive
types of epedaphic algal growth. In the Knervslakte (Fig. 3), the algal
crust is covered by a dust layer less than 1 mm thick. Below this a Schizothrix species forms a zone about 1-1.5 mm thick, followed by a 1.5-5.0
mm thick layer of fungus hyphae. In the Little Karroo (Fig. 4), an
epedaphic growth of blue-green algae is formed on the soil surface by
Chrococcus westii Boye Petersen, Gloeocapsa dermochroa Näg., and Tolypothrix byssoidea (Berkeley) Kirchner (the latter associated with a
fungus).
Takyrs (in Turkic languages, "place without plants") cover large areas
of the desert and semidesert regions of Central Asia. Bolyshev (1955)
describes takyr as a flat area characteristically devoid of higher vegetation
and covered by a thin, brownish, elastic, somewhat lustrous, and velvety
algal crust. The surface of the crust is fragmented into polygonal aréoles
of approximately uniform size (5-25 cm). Takyr crusts are formed primarily by filamentous blue-green algae of the family Oscillatoriaceae which
cement the soil particles into a firm layer. The most common species is
173
darker, reddish, blackish, or brownish. Some algal crusts show a fuzzy
growth due to the presence of filamentous blue-green algae. (3) Lichen
soil crusts are usually more conspicuous than raincrusts or algal soil crust,
their structure is dense and they may attain 2-5 cm thickness. Their color
is dark brownish, blackish, or, after rains, greenish, retaining moisture for
a longer period than algal soil crusts. Lichen soil crusts often become
folded and reticulate, extending above the soil surface and separating from
the substrate. According to Cameron and Blank (1966), the algal components are most frequently Schizothrix calcicola (Ag.) Gom., Microcoleus chtonoplastes (Mert.) Zanard., and Microcoleus vaginatus (Vauch.)
Gom. They also point out that "most of the algae in Southwestern United
States desert soil crusts tend to become parasitized, eventually developing
into distinctive crustose soil lichens." This however does not seem to be
the case in more arid deserts, such as the Sahara (Killian, 1953) or in
the Negev. In the Negev, Friedmann et al. (1967), Friedmann and
Ocampo-Paus (1965, 1966), Ocampo-Paus and Friedmann (1966), and
R. Ocampo (unpublished) found the following species in thin evanescent nonlichenized algal crusts: Bracteacoccus minor (Chodat) Petrovâ
var. desertorum Friedmann et Ocampo-Paus, Chlorosarcinopsis eremi
Chantanachat et Bold, Chlorosarcinopsis negevensis fa. negevensis Friedmann et Ocampo-Paus, Chlorosarcinopsis negevensis fa. ferruguinea
Friedmann et Ocampo-Paus, Protosiphon botryiodes, (Kütz.) Klebs, Radiosphaera negevensis fa. negevensis Ocampo-Paus et Friedmann, Radiosphaera negevensis fa. minor Ocampo-Paus et Friedmann, Oscillatoria sp.,
and Botrydium granulatum (L.) Grev.
In the South African desert, Vogel (1955) describes two distinctive
types of epedaphic algal growth. In the Knervslakte (Fig. 3), the algal
crust is covered by a dust layer less than 1 mm thick. Below this a Schizothrix species forms a zone about 1-1.5 mm thick, followed by a 1.5-5.0
mm thick layer of fungus hyphae. In the Little Karroo (Fig. 4), an
epedaphic growth of blue-green algae is formed on the soil surface by
Chrococcus westii Boye Petersen, Gloeocapsa dermochroa Näg., and Tolypothrix byssoidea (Berkeley) Kirchner (the latter associated with a
fungus).
Takyrs (in Turkic languages, "place without plants") cover large areas
of the desert and semidesert regions of Central Asia. Bolyshev (1955)
describes takyr as a flat area characteristically devoid of higher vegetation
and covered by a thin, brownish, elastic, somewhat lustrous, and velvety
algal crust. The surface of the crust is fragmented into polygonal aréoles
of approximately uniform size (5-25 cm). Takyr crusts are formed primarily by filamentous blue-green algae of the family Oscillatoriaceae which
cement the soil particles into a firm layer. The most common species is