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The input and fate of new C in two forest soils under elevated CO 2
Author(s) -
HAGEDORN FRANK,
SPINNLER DIETER,
BUNDT MAYA,
BLASER PETER,
SIEGWOLF ROLF
Publication year - 2003
Publication title -
global change biology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 4.146
H-Index - 255
eISSN - 1365-2486
pISSN - 1354-1013
DOI - 10.1046/j.1365-2486.2003.00638.x
Subject(s) - calcareous , soil water , loam , incubation , leaching (pedology) , environmental science , soil classification , environmental chemistry , soil type , soil science , fractionation , chemistry , agronomy , botany , biology , biochemistry , organic chemistry
The aim of this study was to estimate (i) the influence of different soil types on the net input of new C into soils under CO 2 enrichment and (ii) the stability and fate of these new C inputs in soils. We exposed young beech–spruce model ecosystems on an acidic loam and calcareous sand for 4 years to elevated CO 2 . The added CO 2 was depleted in 13 C, allowing to trace new C inputs in the plant–soil system. We measured CO 2 ‐derived new C in soil C pools fractionated into particle sizes and monitored respiration as well as leaching of this new C during incubation for 1 year. Soil type played a crucial role in the partitioning of C. The net input of new C into soils under elevated CO 2 was about 75% greater in the acidic loam than in the calcareous sand, despite a 100% and a 45% greater above‐ and below‐ground biomass on the calcareous sand. This was most likely caused by a higher turnover of C in the calcareous sand as indicated by 30% higher losses of new C from the calcareous sand than from the acidic loam during incubation. Therefore, soil properties determining stabilization of soil C were apparently more important for the accumulation of C in soils than tree productivity. Soil fractionation revealed that about 60% of the CO 2 ‐derived new soil C was incorporated into sand fractions. Low natural 13 C abundance and wide C/N ratios show that sand fractions comprise little decomposed organic matter. Consistently, incubation indicated that new soil C was preferentially respired as CO 2 . During the first month, evolved CO 2 consisted to 40–55% of new C, whereas the fraction of new C in bulk soil C was 15–23% only. Leaching of DOC accounted for 8–23% of the total losses of new soil C. The overall effects of CO 2 enrichment on soil C were small in both soils, although tree growth increased significantly on the calcareous sand. Our results suggest that the potential of soils for C sequestration is limited, because only a small fraction of new C inputs into soils will become long‐term soil C.