Soil carbon dynamics during the first years following pseudo-steppe afforestation by Eucalyptus robusta trees on tropical highlands

Ramanandraibe Iaviantsoa, Bordron Bruno, Bouillet Jean-Pierre, Razafindrakoto Fenitra, Epron Daniel, Razafimbelo Tantely. 2024. Soil carbon dynamics during the first years following pseudo-steppe afforestation by Eucalyptus robusta trees on tropical highlands. In : IUFRO 2024 World Congress: Forests and Society Towards 2050. Book of abstracts. IUFRO, Swedish University of Agricultural Sciences. Uppsala : IUFRO, Résumé, p. 440. IUFRO 2024 World Congress: Forests and Society Towards 2050. 26, Stockholm, Suède, 23 Juin 2024/29 Juin 2024.

Résumé : Afforestation is known as an efficient climate change mitigation option by the ability of forests to store carbon in tree biomass and soil. However, data on soil carbon storage, sequestration capacity and dynamics in planted forests are scarce in Sub-Saharan African countries, particularly in highlands. This work aims to assess the potential of eucalyptus plantations (EP) on soil carbon sequestration during the first years following the afforestation of grassland. EP are the primary fuelwood source in Madagascar where one of the main drivers of deforestation is the need for fuelwood. Our hypotheses were: i) soil carbon stocks increase with tree biomass ii) mineral fertilizer improves biomass production and so soil carbon sequestration iii) soil carbon contents vary spatially depending on the distance from the tree. The study was conducted in Anjozorobe in the Central Highlands of Madagascar with average annual rainfall and temperature of 1295 mm and 18.7°C respectively. The soils are Ferralsols. Natural vegetation is characterized by a pseudo-steppe dominated by Aristida sp grasses. A four-age chronosequence (2, 4, 5 and 6 years old) of Eucalyptus robusta plantation with and without mineral fertilization was selected with two controls as the initial (pseudo-steppe) and final (more than 60 years old EP) state of land use change from grassland to planted forest. These ten treatments have three replicates. In each inner plot, soil samples were collected at six depths (0 - 5 cm, 5-10 cm, 10-20 cm, 20-30 cm, 30-50 cm and 50-100 cm) at three different distances from a tree. Determination of soil carbon content and bulk density calculation will permit the estimation of soil carbon stocks in different soil layers according to the spatial position at the plot level and the fertilization application. Aboveground tree biomass was estimated by measuring circumferences at breast height and height of each tree and sampling destructively eight trees per treatment. Allometric equations were established to estimate the biomass of all aboveground tree compartments and the relation between soil carbon storage and tree biomass will be deducted. The results will give insights into the capacity of EP on tropical highlands to improve soil carbon sequestration.

Auteurs et affiliations

• Ramanandraibe Iaviantsoa, CIRAD-PERSYST-UMR Eco&Sols (FRA)
• Bordron Bruno, CIRAD-PERSYST-UMR Eco&Sols (MDG) ORCID: 0000-0002-6290-1010
• Bouillet Jean-Pierre, CIRAD-PERSYST-UMR Eco&Sols (MDG)
• Razafindrakoto Fenitra, Université d'Antananarivo (MDG)
• Epron Daniel, Kyoto University (JPN)
• Razafimbelo Tantely, Université d'Antananarivo (MDG)

Source : Cirad-Agritrop (https://agritrop.cirad.fr/612669/)

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