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

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The respiratory response with glucose treatment was determined three times during the year
2007: in June, July and September. Measurements of soil respiration by root-exclusion technique
were done in the same days, simultaneously with combined technique.
6.2.3. Regression analyses technique
Regression approach was firstly suggested by Kucera and Kirkham (1971) and is based on
the assumed linear relationship between root biomass and amount of CO2 respired by roots and
rhizosphere microorganisms. The amount of CO2 derived from SOM decomposition correspond to
the y-intercept of the regression line between root biomass (independent variable) and total CO2
efflux from soil (dependant variable).
Rs = x BGb +kh; Rh = kh and Ra = Rs - Rh (eqn. 3)
where Rs-total soil respiration; BGb – belowground biomass, kh – y-intercept, which is assumed to
be a measure of SOM-derived respiration.
The method is comparatively simple and was applied in numerous studies mostly on forest
ecosystems (Gupta and Singh, 1981; Behera et al., 1990; Hill et al., 2004; Rodeghiero and Cescatti
2006; Wang et al., 2007).
The measurement procedure was the following: in the beginning of 2008 twelve pairs of soil
collars were installed into the soil not far from the partitioning plots of root-exclusion technique.
Soil respiration was measured on bimonthly bases from all the collars. In the beginning of June,
during the peak of root biomass (from the data of 2007), twelve collars were removed and soil
cores of 8cm diameter and 30 cm depth were sampled under the soil respiration measurement plots
for further analyses on the belowground biomass. The rest of the collars were leaved in soil and the
measurements of soil respiration were continued.
6.3. Results
6.3.1. 2007: Mesh- exclusion vs. combined SIR
The results of partitioning of soil respiration by mesh-exclusion technique are shown in Fig.
3. The contribution of root-derived respiration to total CO2 efflux from soil varied in the range of
2% - 79%, with an average value of 28%.
Once a month, in June, July and September simultaneously with measurements by mesh-
exclusion technique but on the separate plots the application of the glucose solution and water was
performed. An example of the response of total and microbial respiration to the addition of glucose
and water, and the final results of the partitioning are shown in figure.4. Effect of moistening on
total CO2 efflux from soil was pronounced during the first hour after the treatment, after that the
respiration level decreased to the initial value. The effect of the glucose solution was more evident;