Soil Carbon-13 Natural Abundance under Native and Managed Vegetation in Brazil
- Wolfgang Wilcke *a and
- Juliane Lilienfeinb
The conversion of native Cerrado vegetation (a mixed C3 and C4 vegetation) to Pinus caribaea Morelet plantations (a pure C3 vegetation) and to Brachiaria decumbens stapf pastures (a pure C4 vegetation) likely affects the C cycle. We used the natural abundance of 13C (δ13C) in vegetation and soil to: (i) quantify the contributions of C3 and C4 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 δ13C value of the soils (Anionic Acrustoxes) under Cerrado vegetation ranged from −20.5 to −19.7‰, which was dissimilar to the mass-weighted mean δ13C signal of the aboveground biomass (−25.8‰). This was because grasses being C4 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 C3 and C4 13C 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.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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