ISSN 10674136, Russian Journal of Ecology, 2011, Vol. 42, No. 4, pp. 305–314. © Pleiades Publishing, Ltd., 2011.
Since approximately 1950, the savannah of the
Congolese littoral (Fig. 1) has gradually been planted
with Eucalyptus in dense populations harvested on
rotations of seven years (Laclau et al., 2000).
Plantations are sustainable if they meet multiple
sociological, economic and ecological criteria that have
been redefined by the report of Brundtland (World
Commission on Environment and Development,
1987). These Eucalyptus plantations would meet these
criteria of sustainability if an ecosystem similar to the
original the savannah would follow if the planting of
Eucalyptus were stopped; this would prove that climatic
and pedologic local conditions have not been radically
modified by the existence of these plantations. To find
out whether or not this is the case, it is necessary to
make comparative studies of energy, carbon, mineral
and water balances of the two ecosystems namely, the
The article is published in the original.
original savannah ecosystem, and the manmade Euca
lyptus ecosystem that has succeeded it.
The aim of the work described in this paper is to
study the water balance of the two ecosystems and
more particularly their actual evapotranspiration
(transpiration and evaporation). The transpiration is
the “engine” of the waterflux through the plant.
Transpiration from the plant canopy is determined by:
• climatic demand (potential evapotranspiration),
dependent on solar radiation, air temperature, humid
ity deficit and wind speed,
• physiological response mechanisms to environ
mental conditions, dependent on genotype,
• plant canopy structure, particularly leaf area
• availability of soil water to the vegetation roots,
soil water content.
Eucalyptus has been chosen for its rapid growth.
Sustainable Eucalyptus plantations would be planta
tions whose wateruse would not be excessive relative
to the original savannah. This study provides necessary
Water Balance and Sustainability of Eucalyptus Plantations
in the Kouilou Basin (CongoBrazzaville)
J. J. Nizinski, G. Galat, and A. GalatLuong
Institut de Recherche pour le Développement, I.R.D., UMR 211 “BIOEMCO—Biogéochimie et écologie des milieux continentaux—
Interactions biologiques dans les sols”, Centre d’Ile de France, 32 avenue Henri Varagnat, 93143 Bondy cedex, France
Received July 26, 2010
—To appreciate the sustainabilty of these plantations of Eucalyptus, it is necessary to make a com
parative study of energy, carbon, mineral and water balances of two ecosystems, i.e. the original savannah eco
system, and the manmade ecosystem the Eucalyptus plantations that have succeeded it. The aim of this work
is to study the water balance of the two ecosystems and more particularly their actual evapotranspiration.
Throughfall, net interception during the rainy seasons (1996–99) were 867 mm and 112 mm for the Eucalyp
tus plantation and 878 mm and 101 mm for the savannah, respectively. The mean total annual actual evapo
transpiration respectively 1127 mm for a plantation and 821 mm for a savannah. During the year transpira
tion/potential evapotranspiration ratio (
) is related to the soilwater depletion: The
ratio of 0.79
was not reduced from field capacity until 65% of
, and then it decreased quickly to near zero at wilting
point. The drainage out of rooting depths of savannah during the rainy season was of 827 mm, a total over
3 years; while the drainage out of rooting depths of Eucalyptus plantation was of 470 mm, a difference in
drainage between two ecosystems of 357 mm a total over these three years. The Eucalyptus plantation is man
made ecosystem which takes up and transpires every day throughout the year and uses all available water. The
succession of several raindeficient years will reduce the wood production of the plantation but, knowing that
between 1949 and 1998 four successive raindeficient years have only occured once while the length of rota
tion is seven years; this dry episode does not compromise the survival of the plantation, although it reduces
its wood production. The savannah has a cycle of vegetation such that at the end of the dry season the water
remaining in the rooting depths of savannah is sufficient for three successive raindeficient years to have no
impact on its production.
: Sustainability; Plantation; Eucalyptus; Savannah; Soilwater balance; Evapotranspiration.