title: Conversion of lowland tropical forests to tree cash crop plantations loses up to one-half of stored soil organic carbon.
abstract: Tropical deforestation for the establishment of tree cash crop plantations causes significant alterations to soil organic carbon (SOC) dynamics. Despite this recognition, the current Intergovernmental Panel on Climate Change (IPCC) tier 1 method has a SOC change factor of 1 (no SOC loss) for conversion of forests to perennial tree crops, because of scarcity of SOC data. In this pantropic study, conducted in active deforestation regions of Indonesia, Cameroon, and Peru, we quantified the impact of forest conversion to oil palm (Elaeis guineensis), rubber (Hevea brasiliensis), and cacao (Theobroma cacao) agroforestry plantations on SOC stocks within 3-m depth in deeply weathered mineral soils. We also investigated the underlying biophysical controls regulating SOC stock changes. Using a space-for-time substitution approach, we compared SOC stocks from paired forests (n = 32) and adjacent plantations (n = 54). Our study showed that deforestation for tree plantations decreased SOC stocks by up to 50%. The key variable that predicted SOC changes across plantations was the amount of SOC present in the forest before conversion--the higher the initial SOC, the higher the loss. Decreases in SOC stocks were most pronounced in the topsoil, although older plantations showed considerable SOC losses below 1-m depth. Our results suggest that (i) the IPCC tier 1 method should be revised from its current SOC change factor of 1 to 0.6 ± 0.1 for oil palm and cacao agroforestry plantations and 0.8 ± 0.3 for rubber plantations in the humid tropics; and (ii) land use management policies should protect natural forests on carbon-rich mineral soils to minimize SOC losses.
authors.affiliation: Buesgen Institute, Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Goettingen, 37077 Goettingen, Germany;
authors.forename: Oliver
authors.initials: O
authors.lastname: van Straaten
authors.affiliation: Buesgen Institute, Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Goettingen, 37077 Goettingen, Germany;
authors.forename: Marife D
authors.initials: MD
authors.lastname: Corre
authors.affiliation: Buesgen Institute, Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Goettingen, 37077 Goettingen, Germany;
authors.forename: Katrin
authors.initials: K
authors.lastname: Wolf
authors.affiliation: Institut de Recherche Agricole pour le Développement, Nkolbisson, Yaoundé, Cameroon;
authors.forename: Martin
authors.initials: M
authors.lastname: Tchienkoua
authors.affiliation: Instituto Nacional de Investigación Agraria, La Molina, Lima 12, Peru;
authors.forename: Eloy
authors.initials: E
authors.lastname: Cuellar
authors.affiliation: The James Hutton Institute, Craigiebuckler, Aberdeen AB15 8QH, Scotland, United Kingdom.
authors.forename: Robin B
authors.initials: RB
authors.lastname: Matthews
authors.affiliation: Buesgen Institute, Soil Science of Tropical and Subtropical Ecosystems, Georg-August University of Goettingen, 37077 Goettingen, Germany; eveldka@gwdg.de.
authors.forename: Edzo
authors.initials: E
authors.lastname: Veldkamp
mesh_terms: D018533:Biomass; D002244:Carbon / Q000032:analysis*; D018556:Crops, Agricultural / Q000737:chemistry*; D017753:Ecosystem; D065928:Forests; D005843:Geography; D009584:Nitrogen / Q000032:analysis; D009930:Organic Chemicals / Q000032:analysis*; D012987:Soil / Q000737:chemistry*; D018709:Statistics, Nonparametric; D014197:Trees / Q000737:chemistry; D014329:Tropical Climate
chemical_list: D009930:Organic Chemicals; D012987:Soil; D002244:Carbon; D009584:Nitrogen
keywords: cacao; land-use change; oil palm; rubber; soil carbon