Plant secondary compounds can have stimulating effect
on C cycling and change its rate in soils. We examined
how leaves of bay laurel ( Laurus nobilis
and 1,8-cineole (CIN), one of its constituents, affect soil
C mineralization and its rate. Leaves and soil samples of
bay laurel were taken from Cukurova University Campus
(Adana, Turkey) growing naturally under Mediterranean
climate conditions. Leaves and CIN were considered as
the two forms of organic C sources. After determining the
level of 1,8-cineole in leaves by gas chromatography-mass
spectrometry, soils were mixed with powdered leaves and
1,8-cineole based on their C contents at same and half
doses of soil organic C level. Carbon mineralization of all
soils was determined over 54 d (28 °C, 80% field capacity).
While 1,8-cineole was found as a major constituent of
leaves (65% of essential oil), all doses of leaves and CIN
increased soil microbial activity. There were significant
differences for C mineralization rate between control and
all applications (P < 0.05). High C levels of all treatments
decreased C mineralization rate compared to control soils.
In summary, all treatments stimulated C mineralization and
it is possible to conclude that soil microorganisms adapted
to use CIN as an energy source.