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66 3. CONTRIBUTION OF PHOTOSYNTHETIC CARBON INPUTS TO PLANT RESPIRATION USING DESTRUCRIVE AND NON-DESTRUCTIVE TECHNIQUES
3.1. Introduction Soil respiration (Rs) is the largest terrestrial source of CO2. Quantifying the processes that control the dynamic of Rs is thus critical to understand the global carbon (C) cycle. Rs in most related studies is determined primarily by soil temperature (Ts) (Lloyd and Taylor, 1994); soil moisture (SWC) often plays a role at the dry and wet ends of its distribution (Davidson et al., 1998; Palmroth et al., 2005; Tang and Baldocchi, 2005). In addition to well studied effects of Ts and SWC on Rs dynamic, some recent studies have investigated the role of photosynthetic C inputs in determining the magnitude and variability of Rs, suggesting that within-ecosystem, photosynthetic C transport and allocation could be critical for understanding the biosphere-atmosphere exchange of C and for the accurate prediction of terrestrial ecosystem respiration sources (Table 1). The allocation of recently assimilated C to below- vs. aboveground plant components and to storing vs. respiration are key uncertainties in global terrestrial ecosystem C models (Friedlingstein et al., 1999). How plants allocate C determines how long that C may remain in the plant or soil before returning to the atmosphere by respiration. If models of Rs are to incorporate photosynthetic C inputs it is necessary to understand how these two fluxes are coupled. Studies employing stable isotope, radioactive isotope or automated ecosystem flux measurements are perspective for these purposes as they permit to determine the time lag between photosynthesis and C evolution from rooting-system, avoiding disturbance of the soil surface and natural growing conditions of plants. However, the reported time lags between photosynthetic C uptake and its evolution through the rooting systems vary in the order of hours to days. The possible reason is that up to now the most part of the mentioned experiments were performed in the laboratory conditions: in soil solution or in filled with soil narrow pots, which limits the root growth and do not reflect the real plant growing conditions. Studies in situ are still not numerous, covering few plant functional types and ecosystems. The methodology is not unique, destructive and non-destructive techniques with different shortcomings are involved and is not clear if the obtained results could be compared. Additionally, not much is known about the sources of C that support plant metabolism, but there is clear evidence that both new and old stored C sources contribute (Dickson, 1991; Czimczik et al., 2006; Schuur & Trumbore, 2006; Carbone et al., 2007; Carbone and Trumbore, 2007). Three C pools fuelling plant respiration were recognized in grassland and shrubs: the fast pool, composed of the assimilates of the current day, intermediate pool, which integrates assimilates during the growing season and a storage pool, which is mobilized when necessary, such as during initial leaf growing stage in spring, with mean residence time (MRT) from month to years (Carbone & Trumbore, 2007). To be able to detect it, a longer chase period should be chosen after the labeling: 14 C label measured by accelerated mass spectrometer allows to detect a low-level 67
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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
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 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
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 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
Page 96 and 97: Microbial C was calculated as a dif
Page 98 and 99: taken from 1 µg N-NO2 ml -1 soluti
Page 100 and 101: ates between clipped and unclipped
Page 102 and 103: Fig. 7 Total (Rs), root (Ra)- and m
Page 104 and 105: 104 Rh, (CO 2 , mmolm -2 s -1 ) 7 6
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
Page 112 and 113: an annual mowing the measurement wa
Page 114 and 115: 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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