drivers of soil respiration of root and microbial ... - Unitus DSpace
drivers of soil respiration of root and microbial ... - Unitus DSpace
drivers of soil respiration of root and microbial ... - Unitus DSpace
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2.2.4. Biochemical analyses<br />
Microbial Biomass C<br />
40<br />
Soil sampling was performed twice in the year 2006: in the middle <strong>of</strong> the growing season, in<br />
June <strong>and</strong> in the end <strong>of</strong> the growing season, in October. For each sampling date 8 <strong>soil</strong> cores were<br />
collected.<br />
For MBC determination the Fumigation Extraction method (Vance et al., 1987) was used. In<br />
brief, two portions <strong>of</strong> moist <strong>soil</strong> (20 g oven-dry <strong>soil</strong>) were weighed, the first one (non fumigated)<br />
was immediately extracted with 80 ml <strong>of</strong> 0.5M K 2 SO 4 for 30 min by oscillating shaking at 200 rpm<br />
<strong>and</strong> filtered with filter paper (Whatman n. 42); the second one was fumigated for 24h at 25 °C with<br />
ethanol-free CHCl3 <strong>and</strong> then extracted as described above. Organic C in the fumigated <strong>and</strong> non<br />
fumigated extracts was determined after oxidation with 0.4 N K 2 Cr 2 O 7 at 100°C for 30 min.<br />
Microbial C was calculated as a difference between C content in fumigated <strong>and</strong> non fumigated<br />
extracts divided by a conversion factor (KEC: 0.38).<br />
2.2.5. Statistics<br />
Each measurement plot <strong>of</strong> <strong>soil</strong> <strong>respiration</strong> was considered as experimental unit, the replicate<br />
measurements were averaged for further analyses, so that <strong>soil</strong> CO2 efflux for each date represents<br />
the average <strong>of</strong> all the plots. St<strong>and</strong>ard error (SE) <strong>of</strong> mean was calculated to provide a measure <strong>of</strong> the<br />
variance for aboveground <strong>and</strong> belowground biomass <strong>and</strong> <strong>soil</strong> <strong>respiration</strong> flux measurements.<br />
Multiple linear regression analysis was used to evaluate the contribution <strong>of</strong> GPP <strong>of</strong> various times<br />
after the measurements to <strong>soil</strong> CO2 efflux from <strong>soil</strong>. Nonlinear regression analyses were performed<br />
to estimate the effect <strong>of</strong> temperature <strong>and</strong> <strong>soil</strong> water content on <strong>soil</strong> <strong>respiration</strong> <strong>of</strong> different origin.<br />
The significant <strong>of</strong> all the regression coefficients were tested using STATISTICA (Stat S<strong>of</strong>t).