Pedon 23 - Physical Land Resources - Universiteit Gent

PROJECT PROFILES
IMPACT OF TERMITES ON THE
MINERAL, TEXTURAL AND MOLECULAR
ORGANIC COMPOSITION OF TROPICAL
SOILS
2010-2014
Funded by: FWO (Research Foundation Flanders)
Promoters: E. Van Ranst, P. Boeckx, F. Vanhaecke, G. Baert, F. Mees
Doctorandi: B.B. Mujinya, H. Erens
Deep core sampling under large termite mounds of
Katanga, DRC
The Miombo woodlands of South Katanga (DRC) are
characterized by 3 to 5 of these large conic mounds ha -1
built by Macrotermes falciger. With an average height and
diameter exceeding 5 and 18 m respectively, these are
some of the largest biogenic structures in the world.
Mound soil properties differ considerably from those of the
surrounding Ferralsols. Most notably, mound soil exhibits
a finer texture, higher CEC and exchangeable basic cation
content, lower SOM content, and the build-up of
carbonates. However, these soil properties were found to
be far from uniform in the 250 m³ that constitute an
average mound. Unlike many other mound-building termite
species, the mounds of Macrotermes falciger are largely
fossil, the result of continuous erosion and recolonization
of existing mounds. The termites’ nesting and foraging
activity, combined with other pedological processes
generates a wide range of physical, chemical, and
biological conditions in different parts of the mound.
Besides mapping the resulting variability of soil properties
within large termite mounds, the Ph.D. studies of my
colleague Basile Mujinya (M.Sc. PLR, 2006) and myself
also contemplate the origin and possible applications of
this variability.
The drilling equipment was positioned as close to the centre as possible
Detailed sampling in the heart of an active colony
A continuous core sample was obtained, from the centre of the mounds
into the parent rock
To elucidate these processes and their implications, many
large termite mounds were cut open and sampled in detail.
Part of the explanation, however, is to be found in the
origin of the building material the termites use for their
construction. The greatest challenge remained to obtain
undisturbed soil samples from the subsoil, the saprolite and
the parent rock. Luckily, during the fieldwork campaigns,
we established good contacts with the geology department
of a local mining company. As such, our friends there
agreed to do three deep core drillings for us underneath the
termite mounds we were investigating. This way, we
obtained three continuous soil cores up to 40 m deep, each
time well into the parent rock. As such, we are now the
first to have a complete and undisturbed vertical sequence
of soil from the top of a termite mound into the underlying
rock. Micromorphological, mineralogical and physicochemical
analyses will be carried out on these samples the
coming months to trace the impact of the termites in this
continuum, and to confirm standing hypotheses on
carbonate formation in mounds, stoneline formation, and
clay and nutrient cycling by termite activity.
Hans Erens
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