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component, expressing a total soil respiration as a sum of root and microbial-derived sources, linearly dependent on root density and soil C content respectively. 6.4.4. General comparison of three partitioning methods 162 After the discussion of all the particularities and shortcoming of the partitioning techniques applied in this study it is possible to compare the results obtained by the methods. The main positive observation is that mesh exclusion and combined SIR techniques, so different in its theoretical and methodological basis, showed quite similar results both in the magnitude of soil respiration fluxes almost for all the measurement days and in its seasonal variation patterns. Actually we expected to observe a higher microbial-derived respiration with combined SIR, as it allows an additional separation of root and rhizomicrobial respiration components. The difference between microbial respirations, obtained from two techniques could be used as an estimate of the rhizomicrobial component of soil respiration. However, having the different sources of the mistake, both methods result in the systematic overestimation of microbial respiration component. The magnitude of this error is uncertain, which limits the reliability of such calculation of rhizomicrobial respiration. The results obtained by mesh exclusion and regression analyses technique in 2008 differed significantly both in the magnitude of the respiration fluxes and in the seasonal patterns of relative contribution of single components to total CO2 efflux. Regression technique, given the most uncertain results, during the whole period of measurements was overestimating the root-derived respiration in confront with mesh exclusion method, sometimes calculating the root contribution as a 100% to total CO2 efflux from soil. To overcome all the uncertainties, which were mainly associated with the particularities of the grassland communities the method requires further development and standardization. Summarizing, the comparison of methodologies in soil CO2 efflux partitioning techniques showed generally good agreement, there are numerous assumptions masked within these results, and we have tried to indicate where potential biases arise and corrections are needed.
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explain diurnal and seasonal change
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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
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Fig. 7 Total (Rs), root (Ra)- and m
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104 Rh, (CO 2 , mmolm -2 s -1 ) 7 6
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Fig. 11 Cumulative microbial respir
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108 After the calculation of synthe
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Fig. 16: a) Relationship between sy
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Page 166: Acknowledgements This work was poss
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