Agriculture Reference
In-Depth Information
Figure IV.64 presents the C:N ratios of the mound materials of 44 Australian termitaria
built by termites of five trophic groups (Lee and Wood, 1971a, Okello-Oloya
et al.,
1985;
Tayasu
et al.,
1998). In the Australian data set, the C:N ratios of the soil:wood interface
feeders and the wood feeders have markedly higher values than those of the litter, grass
and soil-feeding species, the last of which differ only slightly from those of their
surrounding surface soils. It seems likely that the higher values in mounds of the wood
and soil-wood interface feeders may have been due to the incorporation of undigested
wood in their faeces (Lee and Wood, 1971a).
As Lee and Wood (197la,b) noted, Australian termitaria have higher C:N ratios than
those of equivalent ecological strategies recorded from African environments. For example,
a sample of eleven mound materials of African soil-feeding species had a mean C:N ratio
of 11, less than half that of the seven mounds of the equivalent Australian species
presented in Figure IV.64, The reasons for such differences are unknown.
The entire nests of a number of species and the interiors of the mounds of certain
wood- and grass-feeding termites consist of carton, a relatively soft mixture of excreta,
some inorganic material and fragments of undigested, comminuted plant material.
Organic matter concentrations in carton are high and that in the mounds of
Coptotermes
acinaciformis,
a wood-feeding termite from northern Australia ranged from 83 to 93 %
loss-on-ignition (Lee and Wood, 1971b). Intermediate materials also occur, a mixture of
carton-like material and inorganic matter (5-15 % C) occurs in the mounds of
Microcerotermes nervosus
from northern Australia (Tayasu
et al
., 1998).
Soils closely associated with termitaria are also modified, often by such physical
processes as the erosion of materials from the mounds and diffusion of materials and
elements from the mound into the soils below and adjacent to the mounds. In tropical
Australia, the mounds of litter and grass-feeding termites (
Amitermes
spp.) are surrounded