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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The influence <strong>of</strong> moisture on <strong>soil</strong> <strong>respiration</strong> was more complex than temperature. In order<br />
to remove the temperature effect <strong>and</strong> examine the single moisture effect on <strong>soil</strong> CO2 efflux, <strong>soil</strong><br />
<strong>respiration</strong> was normalized by <strong>soil</strong> temperature at a reference value 15 o C:<br />
Rx15= RxQ10 (15-T)/10<br />
where Rx15 is the normalized <strong>respiration</strong> flux, Rx is the measured <strong>respiration</strong>, T is the measured<br />
<strong>soil</strong> <strong>respiration</strong>.<br />
normalized CO 2 (µmol m -2 s -1 )<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
10 15 20 25 30 35 40 45<br />
-2<br />
Rs<br />
Rh<br />
Ra<br />
SWC (%)<br />
Fig. 10 Normalized total, <strong>root</strong>- <strong>and</strong> <strong>microbial</strong>-derived <strong>soil</strong> <strong>respiration</strong> vs. <strong>soil</strong> moisture measured in 2006-2007-<br />
2008.<br />
From figure 10 is clear that <strong>soil</strong> moisture had two opposite effects on total <strong>and</strong> <strong>microbial</strong> <strong>soil</strong><br />
<strong>respiration</strong>. When <strong>soil</strong> moisture was below critical value (below 25%), <strong>soil</strong> <strong>respiration</strong> increased<br />
with moisture, but it decreased when the <strong>soil</strong> moisture was greater than 35%. The negative<br />
correlation at high levels <strong>of</strong> SWC is probably associated with a decrease in <strong>soil</strong> air porosity <strong>and</strong><br />
oxygen availability in <strong>soil</strong>s which influence negatively <strong>microbial</strong> decomposition activity. No<br />
negative effect <strong>of</strong> high SWC was observed on <strong>root</strong>-derived <strong>respiration</strong>.<br />
To verify the effect photosynthetic C supply on <strong>soil</strong> CO2 efflux <strong>of</strong> different origin the data<br />
from the partitioning experiment were plotted vs. GPP from the eddy covariance. Pearson<br />
correlations were performed between the means <strong>of</strong> normalized <strong>and</strong> non normalized values <strong>of</strong> <strong>root</strong>-<br />
derived <strong>respiration</strong> fluxes <strong>and</strong> the mean values <strong>of</strong> GPP 0–7 days prior to each <strong>respiration</strong><br />
measurement date. Linear regressions analyses were performed for the days where Pearson<br />
correlations showed peak values. Significant correlations between GPP <strong>and</strong> <strong>root</strong>-derived <strong>respiration</strong><br />
were observed. Peaks in correlation strength correspond to time shifts between the C uptake through<br />
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