Agriculture Reference
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by erosional pediments which have carbon concentrations similar to those of the mound
materials, or intermediate between these and soils distant from the mounds (Okello-
Oloya
et al
., 1985).
There have been few detailed studies of the chemical characteristics of the organic
matter of termite mounds. Lee and Wood (1971b) presented information on the concen-
trations of organic matter and selected organic and inorganic components of mound
materials and the carton of a number of Australian wood-, grass- and litter-feeding ter-
mites. Carton from the Australian mounds studied was shown to be high in lignin and
humic acids, with higher lignin, total carbohydrate and C:N ratios but lower nitrogen
concentrations in the wood-feeding than in the grass-feeding species. Other studies have
concentrated on the mounds of the Macrotermitinae. Arshad
et al.
(1988) studied organic
matter from the mounds of two African Macrotermitinae (
Macrotermes michaelseni,
M. herus
). Generally, humic acids from soils were shown to have higher molecular
weights and less aromatic material than those from the mounds. In the mounds of
Macrotermes
spp., the concentrations of groups increased while those of carbo-
hydrates and other O-substituted compounds decreased in the order: outer wall, nursery,
royal chamber. Some inter-site variation in the composition of the organic matter of
the
Macrotermes
mounds was also noted.
The fungus comb of
M. michaelseni
was studied by Arshad and Schnitzer (1987) and
Arshad
et al.
(1988) who found it to contain approximately 14 % of inorganic material.
The organic matter contained 40 % carbohydrate (all of which was present as polysac-
charides which, on hydrolysis, were shown to be dominated by glucose), 10 % proteina-
ceous material (all as peptides or longer-chain structures). Appreciable concentrations of
aliphatic and aromatic plus phenolic materials were also noted. Using fractionation
techniques commonly used for soil materials, the base-insoluble humin (40 % by mass
of organic matter) was found to be mostly carbohydrate while the humic acid (40 %) and
the fulvic acid (20 %) components contained most of the aromatic material.
As discussed in Chapter III.4.3.2.1, termite whole-body values are closely related
to those of their diet (Figure III.52). The values of termite-mound organic materials
are also related to those of the termite diet (Figure IV.65) (Spain and Reddell, 1996)
because of the incorporation of faeces and secretions of limited ranges into the
mound materials during construction, as gallery linings and as infilling materials in voids
of all types. Mound organic matter may therefore lie in the C3 range, the C4 range or
somewhere in between, depending on the diet of the termite building the mound and
the proportion and value of the incorporated soil (Spain and Reddell, 1996).
In savanna environments, the organic materials included in the mounds of the pre-
dominantly-earthen, grass-harvesting termites are largely of C4 origin and raise the
values of the mound materials above those of the mound interspace soils. In contrast,
the inclusion of materials of C3 origin depresses the values of the mounds of
the wood-feeding termites below those of the surrounding soils. The diet of the litter-
feeding species may include a mixture of C3 and C4 materials; the values of
organic matter in their mounds depends on that of the predominant materials incorpo-
rated and this may alter with time and location. However, mounds in C3-dominated
rainforest situations have similar values to those of the adjacent surface soil. In the high
termitaria built by fungus-cultivating termites in African savannas, the C3 vegetation
