74
WALLACE H. FULLER
of all organic life and therefore prominent dwellers in desert soils. (Fuller
et al., 1961). Many algae species are found in desert soils (Cameron, 1961). The greatest number belong to the blue-green and green
groups. Coccoid green forms and filamentous blue-greens dominated the
extremely dry desert soils examined in California. The green alga, most
abundant, was Protococcus grevillei and the blue-greens were Microcoleus
vaginatus, M. chthonoplastes, Schizothrix calcicola, Plectonema nostocorum, Scytonema hofmannii, or Nostoc muscorum. The latter are also
the algae that are found associated with fungi to form lichens (Shields,
1957).
Algae are commonly identified with the crusts of takyrs, Solonetz, and
other desert soils of Central Asia (Bolyshev, 1964). The algae may form
crust on all the desert soils of the world, being most prominent wherever
bare soil is exposed. These crusts or desert chips are high in nitrogen and
other plant nutrients (Fuller et al., 1961; Sims and Dregne, 1962; Mayland
et al., 1966). The nitrogen is primarily contained in the algal tissues in
organic forms since ammonium and nitrite and nitrate nitrogen are rarely
found in algal crusts (Mayland et al, 1966; Shields et al., 1957). Algae
may adversely affect the moisture economy of irrigated crop land by inhibiting water penetration while favoring the nutritional economy by fixing
atmospheric nitrogen and carbon as a source of organic matter and nitrogen. Algal crusts on virgin desert lands have been cited as. improving water
infiltration, reducing soil erosion, and aiding in plant seedling establishment. The intense wetting and drying of the native desert as compared
with the necessity of more moist conditions for crop production explains
the apparent discrepancy in the soil-algal-water relationships described.
Diatoms are found in soils of Central Asia (Lobova, 1960), the Great
Salt Lake area of Utah and many other lake-bed areas. Their siliceous
skeletons have accumulated in large quantities in old lake beds under many
climatic conditions. However diatoms develop most rapidly under warm
temperature conditions. As diatomaceous earth, these siliceous skeletal
residues are now mined for numerous industrial and home uses.
Blue-green algae (Cyanophyta) are present universally in desert soils
where water accumulates. They have the capacity of rapid development
as warm rains wet them. The author has observed a doubling in the weight
of algal crusts in the deserts of Arizona in as short a period as 2 hours
after a warm rain. Phormidium is a common species (Lobova, 1960) to
many deserts. Soil algae appear to be the most abundant microbial mass
in harsh, barren deserts of North and South America, whereas microaerophillic bacteria are most prominent along the edge of the harshest
deserts near the vegetation and in soils of greater development (Cameron,
1966).
WALLACE H. FULLER
of all organic life and therefore prominent dwellers in desert soils. (Fuller
et al., 1961). Many algae species are found in desert soils (Cameron, 1961). The greatest number belong to the blue-green and green
groups. Coccoid green forms and filamentous blue-greens dominated the
extremely dry desert soils examined in California. The green alga, most
abundant, was Protococcus grevillei and the blue-greens were Microcoleus
vaginatus, M. chthonoplastes, Schizothrix calcicola, Plectonema nostocorum, Scytonema hofmannii, or Nostoc muscorum. The latter are also
the algae that are found associated with fungi to form lichens (Shields,
1957).
Algae are commonly identified with the crusts of takyrs, Solonetz, and
other desert soils of Central Asia (Bolyshev, 1964). The algae may form
crust on all the desert soils of the world, being most prominent wherever
bare soil is exposed. These crusts or desert chips are high in nitrogen and
other plant nutrients (Fuller et al., 1961; Sims and Dregne, 1962; Mayland
et al., 1966). The nitrogen is primarily contained in the algal tissues in
organic forms since ammonium and nitrite and nitrate nitrogen are rarely
found in algal crusts (Mayland et al, 1966; Shields et al., 1957). Algae
may adversely affect the moisture economy of irrigated crop land by inhibiting water penetration while favoring the nutritional economy by fixing
atmospheric nitrogen and carbon as a source of organic matter and nitrogen. Algal crusts on virgin desert lands have been cited as. improving water
infiltration, reducing soil erosion, and aiding in plant seedling establishment. The intense wetting and drying of the native desert as compared
with the necessity of more moist conditions for crop production explains
the apparent discrepancy in the soil-algal-water relationships described.
Diatoms are found in soils of Central Asia (Lobova, 1960), the Great
Salt Lake area of Utah and many other lake-bed areas. Their siliceous
skeletons have accumulated in large quantities in old lake beds under many
climatic conditions. However diatoms develop most rapidly under warm
temperature conditions. As diatomaceous earth, these siliceous skeletal
residues are now mined for numerous industrial and home uses.
Blue-green algae (Cyanophyta) are present universally in desert soils
where water accumulates. They have the capacity of rapid development
as warm rains wet them. The author has observed a doubling in the weight
of algal crusts in the deserts of Arizona in as short a period as 2 hours
after a warm rain. Phormidium is a common species (Lobova, 1960) to
many deserts. Soil algae appear to be the most abundant microbial mass
in harsh, barren deserts of North and South America, whereas microaerophillic bacteria are most prominent along the edge of the harshest
deserts near the vegetation and in soils of greater development (Cameron,
1966).