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152 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;
the respiration response of microbes was increasing sharply and stabilized only 2.5 hours after the treatment. Fig. 3 a) Root- and microbial-derived respiration obtained by root-exclusion technique. b) Contribution of root CO 2 ( mol m -2 s -1 ) 4.5 4.0 3.5 3.0 2.5 2.0 1.5 1.0 0.5 0.0 CO 2 (µmol m -2 s -1 ) 9 8 7 6 5 4 3 2 1 0 -1 100% 80% 60% 40% 20% 0% 26-apr 72% 16-mag and microbial respiration to total CO2 efflux from soil. Control Water Glucose R mic 28% 5-giu 25-giu 15-lug 4-ago before adding 30 min 1h 30min 2h 30min 3h 30 min 4h 30 min Fig. 4 Example of the effect of glucose (3 mg g -1 soil ) and water addition on total and microbial respiration in June. 24-ago 13-set 3-ott 23-ott Rh Ra 12-nov 2-dic 153
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explain diurnal and seasonal change
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sull’intensità del flusso respir
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8 3.2.4. Data analyses and definiti
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1. INTRODUCTION AND OVERVIEW 11
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times as much carbon as the terrest
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Fig. 3 Different soil C pools with
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1.3. Soil respiration sources Soil
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conditions, like soil type, plants
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For grasslands, the nature, frequen
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(a) (b) (c) Fig.7 Amplero (AQ, Ital
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magnitude of root respiration and o
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efficiency, indicating future posit
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approaches for studying of the cont
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Houghton R.A., 2003. Revised estima
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Vleeshouwers L.M., Verhagen A. 2002
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2.1. Introduction 36 Soil respirati
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38 In the year 2005 ten PVC collars
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2.2.4. Biochemical analyses Microbi
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42 Variation of soil respiration fr
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CO 2 efflux (mmol m -2 s -1 ) 44 CO
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46 All diurnal measurements of root
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48 Q10 R 2 p Rs 2.51 0.77 0.000 Ra
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the photosynthesis and its followin
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2.3.3. Inter-annual variation of so
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54 RS RHET 8 6 6 4 25 4 2 2 25 20 T
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2.4. Discussion 2.4.1. Partitioning
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measurements, the possibility to fi
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and Schlesinger, 1992; Moyano et al
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Janssens I.A., Pilegaard K., 2003.
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Xu X., Kuzyakov Y., Wanek W., Richt
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3.1. Introduction Soil respiration
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Our experiment was conducted in a m
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Lactic acid 13 C 13 CO2 Root-derive
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At the end of the process, the subl
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where, MAs - the mean age of the co
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13C of respiration ( o / oo ) 155 1
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Total Label Recovered (TLR, %) Ra R
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GPP (mmol m -2 s -1 ) 25 20 15 10 5
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frequent and possibly they missed t
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3.4.3. Destructive vs. Non-destruct
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Gavrichkova O., Kuzyakov Y., 2008.
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Chapter source: 90 4. THE EFFCT OF
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Bardgett et al. (1997) showed that
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94 Partitioning plots were installe
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Microbial C was calculated as a dif
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taken from 1 µg N-NO2 ml -1 soluti
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ates between clipped and unclipped
Page 102 and 103: Fig. 7 Total (Rs), root (Ra)- and m
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Page 106 and 107: Fig. 11 Cumulative microbial respir
Page 108 and 109: 108 After the calculation of synthe
Page 110 and 111: Fig. 16: a) Relationship between sy
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Page 114 and 115: mineral N available to plants and N
Page 116 and 117: Cambardella C.A., Elliott E.T., (19
Page 118 and 119: Rice C.W., Moorman T.B., Beare M, 1
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Page 122 and 123: 5.1. Introduction 122 Nitrogen (N)
Page 124 and 125: specie, c) an additional aim was to
Page 126 and 127: 5.2.4. Sampling and analyses 126 Na
Page 128 and 129: the differences between N and contr
Page 130 and 131: 130 specific root respiration (max
Page 132 and 133: Fig. 4 a) Intensity of 14 CO2 efflu
Page 134 and 135: Fig. 6 a) values above zero: root-d
Page 136 and 137: 136 Zea mays: A clear diurnal dynam
Page 138 and 139: plants. The growth stage could cont
Page 140 and 141: nitrates. At temperatures of 15 - 2
Page 142 and 143: experiment could be responsible for
Page 144 and 145: Horwath W.R., Pretziger K.S., Paul,
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Page 148 and 149: 148 6.1 . Introduction In studies o
Page 150 and 151: Regression analyses technique, whic
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Page 156 and 157: 6.3.2. 2008: Mesh- exclusion vs. re
Page 158 and 159: 6.4. Discussion 6.4.1. Mesh-exclusi
Page 160 and 161: introduction in a small soil sample
Page 162 and 163: component, expressing a total soil
Page 164 and 165: Kucera C.L., Kirkham D.R., 1971. So
Page 166: Acknowledgements This work was poss
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