Sélection précoce des espèces forestières et potentiel mycorhizien arbusculaire en vue de la reforestation de la forêt claire dégradée du Haut-Katanga, en République Démocratique du Congo

Authors: Kaumbu, Jean Marc Kyalamakasa
Advisor: Khasa, Phambu; Stefani, Franck
Abstract: In the Katanga province, Democratic Republic of the Congo (DR Congo), the anthropogenic pressure is exerted on the Miombo woodland (MW) with the expansion of the agricultural lands and the increased demand for charcoal, due to the demographic growth. The restorationof agricultural and forest fallows has become essential to reverse this decline and sustainably manage the degraded MW. The main objective of this thesis was to study the development of seedlings and the potential of arbuscular mycorrhizal fungi (AMF) in the MW of UpperKatanga, DRC. Its specific objectives were to: (i) assess the development and mycorrhizalstatus of MW species, with respect to their successional status (early (ES) or late (LS) tree species); (ii) determine the arbuscular mycorrhizal inoculum potential (AMIP) in degradedMW; and (iii) describe the diversity and community structure of AMF associated with amultipurpose forest tree (Pterocarpus tinctorius Welw also named Mninga maji in Swahili,Mukula in Bemba).First, the development of the seedlings was evaluated, for two pioneer tree species(Combretum collinum and P. tinctorius) and six late species (Brachystegia boehmii, B.longifolia, B. spiciformis, B. wangermeana, Julbernardia globiflora and J. paniculata), 1, 2and 4 years after planting. Then, the AMIP was estimated in degraded MW by baitingCrotalaria juncea seedlings. The relationship between AMIP and vegetation indix wase stablished with Generalized Linear Mixed Models (GLMM) and linear regressions. Finally, the diversity and the structure of the AMF community in the roots of P. tinctorius were characterized in the agricultural and forest fallow of three sites, by amplification, cloning of the 28S gene of the large subunit (LSU) of the ribosomal DNA and Sanger sequencing. The results showed that the early successional tree species, ES (Chipya) had early growthand were 3 to 40 times more productive than to LS (tree species characteristic of MW). ESspecies were colonized by AMF, whereas LS species were colonized by ectomycorrhizal fungi. In degraded MW, the density of some trees had a positive influence on AMIP,particularly woody legumes acting synergistically with the abundance of annual grasses.Woody legumes were more colonized and would act as AMF plant refuges. Molecular diversity of 30 operational taxonomic units (UTOs) of AMF was associated with P. tinctorius (one of the mycotrophic woody legumes), in the agricultural and forest fallows of three sites studied. The community richness and structure of the AMF were driven by the density ofwoody species colonized by AMF evenly distributed in plant species. The AMF communitywas dominated by species of the genera Rhizophagus and Sclerocystis, and were strongly associated with some chemical properties of the soil (pH, acidity, total aluminium and totaliron) and the density of some trees. Thus, the results highlight a variability of growth and biomass depending on the successional status (ecological groups). Also, the AMIP and the AMF communities were mainly driven by tree density and soil properties. We suggest there forestation of degraded MW with the native species (P. tinctorius, B. spiciformis and C.collinum) in mono-specific plantations or under agroforestry management with food crops.
Document Type: Thèse de doctorat
Issue Date: 2021
Open Access Date: 26 April 2021
Permalink: http://hdl.handle.net/20.500.11794/68940
Grantor: Université Laval
Collection:Thèses et mémoires

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