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38 In the year 2005 ten PVC collars for total soil respiration measurements were established in the soil of Amplero inside the main footprint of the eddy covariance station. To avoid root severing, PVC soil collars of 11 cm in diameter were inserted only 2.5 cm into the soil and stabilized with two iron legs to prevent its moving when the chamber was placed on it. In April 2006 five complete partitioning plots were added, aiming for estimation of contribution of autotrophic and heterotrophic soil respiration to the total CO2 efflux. In April of 2007 the next group of partitioning plots was added to the old one, so that the total amount of old and new added partitioning plots were 10 (Fig. 1). Soil CO2 measurements were performed twice a month during the growing seasons from April to November and monthly during the winter months. No data were taken during the winter 2006-2007 as the soil was under the snow cover. Diurnal measurements were performed once a month during the whole growing season 2007 and 3 times during the year 2008. The number of measurements per day differed from month to month and were dependant on the battery status of the instrument, weather conditions etc. Soil temperature was measured near each collar at 5 cm depth using either LI-COR 6400 or EGM temperature probes. Soil water content (m 3 m -3 ) at depth of 5 cm was measured with a portable system (ThetaProbe ML2x, Delta-T devices Ltd, Cambridge, UK) at three point around each control collar and once inside each partitioning plot. Fig.1 Schematic description of the modified root-exclusion technique. One complete partitioning plot is represented. A root exclusion technique was modified after Leake et al. (2004) and Moyano et al. (2007, 2008), making it more adaptable for the particularities of grassland ecosystems. • Soil cores, 20 cm in diameter and 30 cm deep were sampled; the soil was sieved through 4 mm mesh and all the roots were carefully removed from the soil. • Half of the sampled soil was placed to the nylon meshes with 1µm pore size and returned to the study site. The CO2 measured from these meshes was considered as respiration associated with microbial decomposition of SOM – microbial-derived respiration (Rh) after disturbance. 1µm pore mesh Rh 1 cm pore mesh Ra+Rh control
• Another half of the sampled and sieved soil was placed back without any barriers for the roots growing (bags with 1.0 cm pore size). The CO2 efflux, coming from these bags is a sum of microbial and root-derived respiration (Rh+Ra). • Root-derived respiration was calculated as a difference between these two treatments: ((Rh+Ra)-Rh). • Total soil respiration (Rs) measured from the undisturbed soil was used as a control and in Summarizing: combination with root-derived respiration was used to calculate the real microbial-derived respiration: (Rs – Ra). 1µm = microbial-derived respiration (Rh), after disturbing 1 cm = sum of microbial and root-derived respiration (Rh+Ra) 1cm - 1µm = root-derived respiration (Ra) No mesh = control for total respiration (Rs) Control - Ra = microbial derived respiration (Rh), excluding the effect of soil sieving 2.2.3. Eddy covariance data Ecosystem net carbon and water vapour fluxes have been measured at Amplero continuously since 2002. The eddy covariance system integrates a sonic anemometer (Solent R3, Gill Instruments, Lymington, UK) and a LI 7500 open path infrared gas analyzer (LiCor, Lincoln, NE, USA). The flux data were calculated for 30 min intervals by means of the post-processing program Eddyflux. GPP was calculated from the difference between NEE and TER (Reichstein et al., 2005), where functional dependencies of total ecosystem respiration (TER) with temperatures were determined with CO2 fluxes measured at night (fluxes measured during low mixed periods were discarded, Aubinet et al., 2000). These functions were then applied to daytime data to derive GPP. GPP was estimated for the year 2006 and 2007, data of 2008 are still under elaboration. 39
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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
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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
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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 46 and 47: 46 All diurnal measurements of root
Page 48 and 49: 48 Q10 R 2 p Rs 2.51 0.77 0.000 Ra
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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
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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
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Page 87 and 88: 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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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
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Kucera C.L., Kirkham D.R., 1971. So
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Acknowledgements This work was poss
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