drivers of soil respiration of root and microbial ... - Unitus DSpace

154
100%
80%
60%
40%
20%
0%
85% 13%
June July September
Ra
Rmic
95%
Fig. 5 Results of partitioning obtained by combined soil induced respiration method.
The final result showed a significant variation in the contribution of root and microbial
respiration during the growing season. In September the soil CO2 efflux was represented mostly by
microbial respiration, while in July the major part was respired by roots.
The results of two partitioning techniques, performed in 2007 were pooled together (Fig.6).
Soil respiration components showed similar patterns. In June no difference were observed in root
and microbial respiration between two techniques. In July the estimated values of microbial-derived
respiration were equal, but the root component was three-folds higher in Combined SIR method. In
September on the contrary, no difference was observed in the assessment of root-derived respiration
but increased microbial component given by Combined SIR. However, the general seasonal
dynamic of both root- and microbial- derived respiration was quite similar between both techniques.
To check the presence of the lateral flow of C in the root-free soil of the mesh bags, the
surrounding soil was labeled in a 13 CO2 atmosphere. For these purposes a special chambers for
trapping of the respired CO2, which fit the size of the meshes were constructed. The details of the
labeling procedure are described in Chapter 3. The trapping of the CO2 was performed twice: 1 and
4 hours after the label introduction. The results are shown in figure 7. The background signature of
the CO2 respired from the mesh bags was in the magnitude of -20 o /oo, already one hour after the 13 C
signature rose up to -10 o /oo with the following decrease on the fourth hour of the chase period. Its
worth to note that the labeling zone was covering the soil only from one side of the meshes, which
means that the observed values could be underestimated.