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46 All diurnal measurements of root and microbial-derived respiration performed in various months of 2007 were plotted together against changes in soil temperature (Fig. 7). Microbial respiration clearly increases with increase in the soil temperature: starting from November, September to June. Out of the general trend are the days of July and August with the low microbial activity under the high values of temperature, this period is however characterized by a low SWC. Root-derived respiration didn’ t show such a clear dependence on seasonal changes in temperature and SWC, with relatively high values also during the driest days of July and August. However, the maximum efflux was observed as for microbial respiration in June. 2.3.2. Seasonal variation of soil respiration of different origin Although we have found that the diurnal variation in soil respiration was not strongly correlated with soil temperature, increasing the time scale to seasonal level changes a picture. We assessed sensitivity of soil CO2 efflux of different origin by fitting exponential function to the data from individual treatments. Rx=aexp bTs where Rx is soil respiration from the source, Ts is a soil temperature ( o C) and a is the intercept of respiration when temperature is 0 o C (basal respiration rate) and b represents temperature sensitivity of soil CO2 efflux. The b values were used to calculate a respiration quotient (Q10), which describes change in fluxes over a 10 o C in soil temperature. As the winter measurements were not possible in 2006-2007, we assumed respiration rate, measured in 2008 under 0 o C soil temperature as a basal respiration and applied this value to all the other years. Q10=exp 10/b During the period with SWC>20% total and microbial-derived soil respiration were quite well correlated with seasonal changes in soil temperature at 5 cm depth (Fig. 8), increasing exponentially with increasing of Ts. The exponential relationship in the absence of the water stress accounted for approximately 82% of flux variability for Rs; 80% for Rh and 60% for Ra (Fig. 8, Table 1). The overall Q10 values for the years 2006-2007-2008 are represented in Table 1. Including in the analyses periods with lower SWC resulted in the significant decrease of the Q10’ s and loss of the correlation with temperature. Root-derived respiration was less sensitive to changes in soil temperature, the correlation was not strong and under temperatures higher than 15 o C and favourable soil humidity (SWC>20%) the shape of the regression curve was reaching a plateau, without a characteristic exponential increase, observed for Rh and Rs (Fig. 8).
CO 2 (µmol m -2 s -1 ) 10 9 8 7 6 5 4 3 2 1 0 10 9 8 7 6 5 4 3 2 1 (a) Rs, SWC>20% Rs, SWC20% Rh, SWC20% Ra, SWC
Page 1: !!"% ( !"+ "!$ (!'! ,' - !"+ "!$ ##
Page 4 and 5: explain diurnal and seasonal change
Page 6 and 7: sull’intensità del flusso respir
Page 8 and 9: 8 3.2.4. Data analyses and definiti
Page 11 and 12: 1. INTRODUCTION AND OVERVIEW 11
Page 13 and 14: times as much carbon as the terrest
Page 15 and 16: Fig. 3 Different soil C pools with
Page 17 and 18: 1.3. Soil respiration sources Soil
Page 19 and 20: conditions, like soil type, plants
Page 21 and 22: For grasslands, the nature, frequen
Page 23 and 24: (a) (b) (c) Fig.7 Amplero (AQ, Ital
Page 25 and 26: magnitude of root respiration and o
Page 27 and 28: efficiency, indicating future posit
Page 29 and 30: approaches for studying of the cont
Page 31 and 32: Houghton R.A., 2003. Revised estima
Page 33: Vleeshouwers L.M., Verhagen A. 2002
Page 36 and 37: 2.1. Introduction 36 Soil respirati
Page 38 and 39: 38 In the year 2005 ten PVC collars
Page 40 and 41: 2.2.4. Biochemical analyses Microbi
Page 42 and 43: 42 Variation of soil respiration fr
Page 44 and 45: CO 2 efflux (mmol m -2 s -1 ) 44 CO
Page 48 and 49: 48 Q10 R 2 p Rs 2.51 0.77 0.000 Ra
Page 50 and 51: the photosynthesis and its followin
Page 52 and 53: 2.3.3. Inter-annual variation of so
Page 54 and 55: 54 RS RHET 8 6 6 4 25 4 2 2 25 20 T
Page 56 and 57: 2.4. Discussion 2.4.1. Partitioning
Page 58 and 59: measurements, the possibility to fi
Page 60 and 61: and Schlesinger, 1992; Moyano et al
Page 62 and 63: Janssens I.A., Pilegaard K., 2003.
Page 64: Xu X., Kuzyakov Y., Wanek W., Richt
Page 67 and 68: 3.1. Introduction Soil respiration
Page 69 and 70: Our experiment was conducted in a m
Page 71 and 72: Lactic acid 13 C 13 CO2 Root-derive
Page 73 and 74: At the end of the process, the subl
Page 75 and 76: where, MAs - the mean age of the co
Page 77 and 78: 13C of respiration ( o / oo ) 155 1
Page 79 and 80: Total Label Recovered (TLR, %) Ra R
Page 81 and 82: GPP (mmol m -2 s -1 ) 25 20 15 10 5
Page 83 and 84: frequent and possibly they missed t
Page 85 and 86: 3.4.3. Destructive vs. Non-destruct
Page 87 and 88: Gavrichkova O., Kuzyakov Y., 2008.
Page 90 and 91: Chapter source: 90 4. THE EFFCT OF
Page 92 and 93: Bardgett et al. (1997) showed that
Page 94 and 95: 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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an annual mowing the measurement wa
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mineral N available to plants and N
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Cambardella C.A., Elliott E.T., (19
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Rice C.W., Moorman T.B., Beare M, 1
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120
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5.1. Introduction 122 Nitrogen (N)
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specie, c) an additional aim was to
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5.2.4. Sampling and analyses 126 Na
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the differences between N and contr
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130 specific root respiration (max
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Fig. 4 a) Intensity of 14 CO2 efflu
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Fig. 6 a) values above zero: root-d
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136 Zea mays: A clear diurnal dynam
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plants. The growth stage could cont
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nitrates. At temperatures of 15 - 2
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experiment could be responsible for
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Horwath W.R., Pretziger K.S., Paul,
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146
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148 6.1 . Introduction In studies o
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Regression analyses technique, whic
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152 The respiratory response with g
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154 100% 80% 60% 40% 20% 0% 85% 13%
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6.3.2. 2008: Mesh- exclusion vs. re
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6.4. Discussion 6.4.1. Mesh-exclusi
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introduction in a small soil sample
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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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