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Diversité des écosystèmes terrestres de La Grande Comores et invasion par les plantes introduites : état des lieux, régénération sur coulées de lave et comparaison avec les îles du Sud-Ouest de l'océan Indien

Abstract : As many volcanic islands, the native forests of the Comoros archipelago are exposed to a number of threats, including biological invasions that cause severe impacts to biodiversity. To limit the ongoing decline of forest cover in the Comoros, it is urgent to establish management priorities, but baseline data about invaders and the invasion level in the archipelago are mostly anecdotal. In this study, we focus on the island of Grande Comore and specifically address the following questions: (i) which alien plant species are the most invasive in terms of cover and frequency? (ii) what is the invasion level measured in terms of total cover by alien species at habitat scale and how does is vary across habitat types? (iii) Do elevation and land-use at transect and section scale have an effect on invasion level among habitat types? This study has been conducted on alien woody plants. Surveys targeted lowland to submountain forests (from 24 to 1100 m a.s.l.), using 44 line transects of 150 - 300 m long and 8 - 10 m wide, including all individuals ≥ 1 m high. The major alien plant species in both native and disturbed forests were Psidium cattleyanum, Clidemia hirta and Rubus rosifolius. Lowland forests (100 - 700 m a.s.l.) have been cleared and replaced by plantations of exotic alien woody plants of socio-economic interest (e.g. Cocos nucifera, Mangifera indica, Syzygium aromaticum, etc). Submontain forests (700 - 1100 m) dominated by native species of the genera Nuxia, Ocotea, Tambourissa and Weinmannia still persist but were generally moderately invaded in the understory and uninvaded in the canopy. This is, to our knowledge, the first quantitative assessment of invasion level of the major natural and human-disturbed habitats at island scale in the Comoros. By increasing knowledge on the level of threats by plant invasion in the region, our results can support ongoing management of important ecosystems for conservation of biodiversity and ecosystem services.
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Submitted on : Tuesday, October 12, 2021 - 8:45:10 AM
Last modification on : Tuesday, October 19, 2021 - 5:56:41 PM

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  • HAL Id : tel-03374273, version 1

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Anziz Ahmed Abdou. Diversité des écosystèmes terrestres de La Grande Comores et invasion par les plantes introduites : état des lieux, régénération sur coulées de lave et comparaison avec les îles du Sud-Ouest de l'océan Indien. Biologie végétale. Université de la Réunion, 2021. Français. ⟨NNT : 2021LARE0019⟩. ⟨tel-03374273⟩

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