Relationships between root density of the African grass Hyparrhenia diplandra and nitrification at the decimetric scale: an inhibition-stimulation balance hypothesis
Jc. Lata et al., Relationships between root density of the African grass Hyparrhenia diplandra and nitrification at the decimetric scale: an inhibition-stimulation balance hypothesis, P ROY SOC B, 267(1443), 2000, pp. 595-600
Citations number
24
Categorie Soggetti
Experimental Biology
Journal title
PROCEEDINGS OF THE ROYAL SOCIETY OF LONDON SERIES B-BIOLOGICAL SCIENCES
Previous studies have shown that Lamto savannah exhibits two different type
s of nitrogen cycle with high and low nitrification sites and suggested tha
t the perennial grass Hyparrhenia diplandra is responsible for this duality
at a subpopulation level, with one ecotype being thought to be able to inh
ibit nitrification. The present work aimed to investigate the relationships
between nitrification and the roots of H. diplandra at two scales. (i) Sit
e-scale experiments gave new insight into the hypothesized control of nitri
fication by H. diplandra tussocks: the two ecotypes exhibited opposite infl
uences, inhibition in a low nitrification site (A) and stimulation in a hig
h nitrification site (B). (ii) Decimetric-scale experiments demonstrated cl
ose negative or positive relationships (in sites A or B, respectively) betw
een the roots and nitrification (in the 0-10 cm soil layer), showing an une
xpectedly high sensitivity of the nitrification process to root density. In
both soils, the correlation between the roots and nitrification decreased
with depth and practically disappeared in the 20-30 cm soil layer (where th
e nitrification potential was found to be very low). Therefore, the impact
of H. diplandra on nitrification may be viewed as an inhibition-stimulation
balance.