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26 Nitrate affected negatively the carbohydrate metabolism and energy economy of two plant species: in respect to ammonium, nitrate nutrition increased root-derived CO2 efflux up to 50%; Carbon costs of nitrate reduction were higher for plant species which locate the nitrate reduction site preferably in roots. Root contribution to the whole plant nitrate reduction process is not stable during a plant ontogenesis and could be more important during the early phases of plant growth, following by a decrease in nitrate reduction in roots with time. These, consequently reduces C costs associated with nitrate reduction for more mature plants. The speed of C cycling through a single plant changes with growing stage. The earlier evolution of CO2 from the soil corresponded to the later growing stage of corn and lupine, meaning that growth stage could control the metabolic orientation of plants, influencing source (photosynthetically active leaves, which supply a new C) - sink (developing organs of plants, which compete for the new C) interactions, by this accelerating or slowing down the speed of C translocation to roots. All these should be taken into account while modelling and interpreting the data of CO2 efflux from soil, particularly separating estimation of individual CO2 sources which contribute to the total soil CO2 efflux. Effect of defoliation management practices on root respiration and microbial activity (Chapter 4) To study the effect of mowing and grazing on soil respiration of different origin 5 fence areas, which prevent the inclosed plots from mowing and grazing, were installed in Amplero in 2002. Plots for partitioning of soil respiration were established in managed and unmanaged soil with further bimonthly measurements of respiration fluxes during the year 2006 and 2007. In 2006 two soil sampling for further chemical and biochemical analyses were performed: just after the mowing and four months after the mowing. Grassland management, based on plant defoliation appears to be a suitable management practice, influencing positively the below-ground food-web, and thus SOM transformation and nutrient cycling through increasing the quantity of easily available C substrates, shifting to more efficient microbial community with enhanced C use
efficiency, indicating future positive trends of SOM accumulation. The main results of the experiment are: Defoliation practices decreased all components of soil respiration in confront with non managed plots under common temperature and soil water content; Dependence of root respiration on C supply from shoots is evident from the absence of correlation with soil temperature in managed plots, where the biomass increment under favourable temperatures and SWC was controlled by mowing and grazing. In unmanaged plots root-derived respiration was following temperature patterns, which masks usually the effect of photosynthetic C supply. An observed decrease in microbial-derived respiration was confirmed by laboratory measurements of potential microbial respiration rates. Defoliation practices resulted in the increase of the quantity of easily available C substrates through enhanced root rhizodeposition process, which lead to general microbial relax in terms of C gaining and C mineralization rates. Enhancement of N mineralization with positive feedbacks for plant uptake, leaf tissue N content and further benefits for grazers was observed. Two methods applied for estimation of the C mineralization activity under different management practices: in situ measurements of microbial-derived respiration and potential microbial respiration, measured in laboratory after 28 days of soil incubation, showed comparable trends after accounting for differences in soil temperature and humidity between managed and unmanaged soils. Contribution of individual soil respiration sources to total CO2 efflux by different in situ partitioning techniques (Chapter 6) Were chosen three widely used and perspective partitioning techniques: 1) mesh exclusion technique, a modification of widely used root exclusion method, which was chosen as a reference method in 2007-2008; 2) Combined method: soil induced respiration (SIR) and component integration, applied in 2007; 3) Regression analyses technique, applied in 2008. The estimates of root/microbial contribution to soil respiration obtained by partitioning methods were compared. The main results are the following: 27
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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
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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 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 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
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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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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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