Fjölrit RALA - 15.06.2004, Side 51

Figure 2 Relationships
ofbiomass C-to-soil C
ratio (a) or respiration f
rate-to-soil C ratio (b)
with total porosity. The u
excluded topsoils g
(lozenge symbols) were ^
thosefrom the Faial n
Fulvic Silic Andosol o
and the Icelandic
Pachic Fulvic Silic
Andosol (a) and those
from Tenerife (b).
y = 9,144 x- 5,117 r = 0,985; p < 0,001
y = 1172,46 x - 526,19 r = 0,769; p < 0,0.‘
Using the soils from Mt Etna, we have determined the rates of decomposition of leaf litter in
soils at different stages of development and tested two hypothesis. First, that the
decomposition kinetics that the proportion of C in added plant material that would be
mineralized is greater for soil microbial communities at later stages of development than at
earlier stages. Experimental results indicate that the general applicability of this hypothesis
depends on the source of the litter. Second, the hypothesis that the efficiency of leaf litter
decomposition increases with soil development, was supported because the ratio of C
mineralized from the insoluble fraction of the litter to the C mineralized from the intact litter
was greater for the young soils compared with the more developed soils.
We thank Luciano Lulli and Fabio Terribile (Italy), Jorge Pinheiro and Manuel Madeira
(Azores), Olafur Amalds and Hlynur Oskarsson (Iceland), Marisa Tejedor and Jose
Hemandez-Moreno (Tenerife) and Folkert van Oort and Jean Dejou (France) for the selection
of the COST 622 reference profiles, Toine Jongmans (The Netherlands) and Folkert van Oort
(France) for the soil and site description, Paul Quantin (France) for the WRB soil
classification, Gérard Burtin and Elisabeth Schouller (France) for assistance with the physical
and chemical data, and Eduardo Garcia-Rodeja (Spain) for the oxalate and pyrophosphate
extractable Al, Si and Fe data. We are grateful to Luigi Badalucco, S Marco Meli and
Antonio Ioppolo (Italy) for site section and description in Sicily and Loma English (UK) for
assistance with the microbial assays.
References
Boudot, J.P. 1992. Relative efficiency of complexed aluminium, non-crystalline A1
hydroxide, allophane and imogolite in retarding the biodegradation of citric acid. Geoderma
52: 29-39.
Mazzarino, M.J., L. Szott, and M. Jimenez. 1993. Dynamics of soil total C and N, microbial
biomass, and water-soluble C in tropical agroecosystems. Soil Biol. & Bioch. 25: 205-214.
Murata, T., N. Nagaishi, R. Hamada, K. Sakagami, and T. Kato. 1998. Relationship between
soil sugar composition and the amount of labile soil organic matter in andisol treated with
bark compost of leaf-litter. Biology & Fertility of Soils 27: 342-348.
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