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Soil Carbon‐13 Natural Abundance under Native and Managed Vegetation in Brazil
Author(s) -
Wilcke Wolfgang,
Lilienfein Juliane
Publication year - 2004
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj2004.8270
Subject(s) - vegetation (pathology) , environmental science , oxisol , topsoil , biomass (ecology) , soil water , organic matter , agronomy , soil organic matter , pasture , soil carbon , forestry , ecology , soil science , biology , geography , medicine , pathology
The conversion of native Cerrado vegetation (a mixed C 3 and C 4 vegetation) to Pinus caribaea Morelet plantations (a pure C 3 vegetation) and to Brachiaria decumbens stapf pastures (a pure C 4 vegetation) likely affects the C cycle. We used the natural abundance of 13 C (δ 13 C) in vegetation and soil to: (i) quantify the contributions of C 3 and C 4 plants to the organic matter input into the soil under Cerrado vegetation and (ii) determine the degree of the replacement of original Cerrado‐derived C by Pinus plantations and pastures. The mean δ 13 C value of the soils (Anionic Acrustoxes) under Cerrado vegetation ranged from −20.5 to −19.7‰, which was dissimilar to the mass‐weighted mean δ 13 C signal of the aboveground biomass (−25.8‰). This was because grasses being C 4 plants contributed 11% to the aboveground biomass but about 50% of the organic matter input to the soil, which was estimated with a simple mixing model of the C 3 and C 4 13 C signals. After 12 and 20 yr, only 30% of the original organic matter in the topsoil was replaced by new organic matter under pasture or Pinus plantation, respectively. This turnover took place without significantly changing the C storage of the top 2 m of the soil (17–19 kg m −2 ). The C replacement under Pinus affected only the top 0.15 m. Our results demonstrate that the C replacement in soils following land‐use change in the Oxisols of this study takes several decades and is considerably slower under Pinus than under pasture.