II. DESERT SOILS
75
D. PROTOZOA
Protozoa are well established in desert soils of the central Asian desert
(Brodskii and Yankovskaya, 1930; Brodskii, 1935, 1937). In fact, all
soils, even the sandy and takyr are purported to be rich in protozoa. They
may be observed to be most prevalent in the humus layer or from 0-20
or 30 cm. Information on protozoa in desert soils is very limited.
Termites should be included here because cellulose-hydrolyzing protozoa are necessary for termite activity as flora of their digestive tracts.
Very little is known about termites and soil development except they are
found readily in deserts, transporting soil into mounds and digging channels to various depths in presumably bone-dry soil. Both termite and ant
activity are prominent in desert soils.
E . ACTINOMYCETES
Actinomycetes and streptomycetes are abundantly present in desert soils
(Lobova, 1960). In one of the harshest areas of the world, the Chilean
Atacama Desert, A Streptomyces sp. appeared to be one of the dominant
organisms in the soils sampled (Cameron et al, 1965). Actinomycetes
are distributed widespread in soils, composts and on plant residues under
natural environments. Ordinarily they grow on resistant carbonaceous material (Norman and Fuller, 1942) and soil organic matter at a low level
of moisture. They are expected, therefore, to be well represented in arid
soils and, indeed, they are. Observations in classroom exercises, including
dilution-plate counting of microorganisms of desert soils, over the last 20
years, has convinced the author that actinomycetes and streptomycetes are
as abundant in number, if not more abundant, than any other single group.
Actinomycetes are unusually high in soil populations associated with alkaline conditions.
In localities such as the Bikini Atoll of the Pacific, actinomycetes accounted for 95% of the microorganisms reported (Johnstone, 1947). During periods of drought in Kenya, for example, actinomycetes became the
dominant group of organisms remaining in the soil, replacing the dominance of the bacteria (Meiklejohn, 1957); algae and lichen presumably
were not enumerated.
F. FUNGI
Numeration data of groups of organisms such as bacteria, fungi, algae,
etc., are not easy to interpret. Studies of soil microbial populations and
distributions (Cameron, 1966; Cameron et al, 1965; Cameron and Blank,
75
D. PROTOZOA
Protozoa are well established in desert soils of the central Asian desert
(Brodskii and Yankovskaya, 1930; Brodskii, 1935, 1937). In fact, all
soils, even the sandy and takyr are purported to be rich in protozoa. They
may be observed to be most prevalent in the humus layer or from 0-20
or 30 cm. Information on protozoa in desert soils is very limited.
Termites should be included here because cellulose-hydrolyzing protozoa are necessary for termite activity as flora of their digestive tracts.
Very little is known about termites and soil development except they are
found readily in deserts, transporting soil into mounds and digging channels to various depths in presumably bone-dry soil. Both termite and ant
activity are prominent in desert soils.
E . ACTINOMYCETES
Actinomycetes and streptomycetes are abundantly present in desert soils
(Lobova, 1960). In one of the harshest areas of the world, the Chilean
Atacama Desert, A Streptomyces sp. appeared to be one of the dominant
organisms in the soils sampled (Cameron et al, 1965). Actinomycetes
are distributed widespread in soils, composts and on plant residues under
natural environments. Ordinarily they grow on resistant carbonaceous material (Norman and Fuller, 1942) and soil organic matter at a low level
of moisture. They are expected, therefore, to be well represented in arid
soils and, indeed, they are. Observations in classroom exercises, including
dilution-plate counting of microorganisms of desert soils, over the last 20
years, has convinced the author that actinomycetes and streptomycetes are
as abundant in number, if not more abundant, than any other single group.
Actinomycetes are unusually high in soil populations associated with alkaline conditions.
In localities such as the Bikini Atoll of the Pacific, actinomycetes accounted for 95% of the microorganisms reported (Johnstone, 1947). During periods of drought in Kenya, for example, actinomycetes became the
dominant group of organisms remaining in the soil, replacing the dominance of the bacteria (Meiklejohn, 1957); algae and lichen presumably
were not enumerated.
F. FUNGI
Numeration data of groups of organisms such as bacteria, fungi, algae,
etc., are not easy to interpret. Studies of soil microbial populations and
distributions (Cameron, 1966; Cameron et al, 1965; Cameron and Blank,