| 要旨トップ | 目次 | | 日本生態学会第73回全国大会 (2026年3月、京都) 講演要旨 ESJ73 Abstract

一般講演（口頭発表） N01-07 （Oral presentation）

#### Acute impact of wildfire on tree communities in a seasonally dry tropical forest, northwestern Madagascar【E】

*Ando Harilalao RAKOTOMAMONJY（Kyoto University）, Yutaro FUJIMOTO（Forest Products Research Inst.）, Joseph Emile Honour PERCIVAL（University of Hawaii, Hilo）, Hiroki SATO（Kyoto University）, Tojotanjona Patrick RAZANAPARANY（University of Antananarivo）, Kaoru KITAJIMA（Kyoto University）

Background. Recurrent anthropogenic fire threatens the integrity of Madagascar’s seasonally dry tropical forests, particularly nutrient-poor white-sand systems that are structurally fragile and species-rich. Aims. To quantify the short-term effects of first and repeated burns on forest structure, species diversity, and composition. Methods. We compared three adjacent areas in Ankarafantsika National Park with contrasting fire histories: unburned control, once-burned (2021), and twice-burned (2017 & 2021). Each area contained 21 systematically placed 5 m × 5 m plots. All live woody stems with a diameter ≥ 1 cm were identified and measured. Key results. Relative to the control, stem density declined by 83 % (once-burned) and 89 % (twice-burned); maximum stem diameter decreased from 30.8 cm to < 23 cm. Species richness fell from a median of 33 to 8 and 1, and Shannon diversity from 3.12 to 1.91 and 0.64, respectively. Multivariate analyses showed significant compositional divergence, with twice-burned plots exhibiting the greatest heterogeneity. Canopy dominants were lost from twice-burned interiors, replaced by disturbance-tolerant shrubs and lianas. Conclusions. Even a single fire can cause structural and compositional simplification; repeated burns intensify these effects. Implications. Targeted fire prevention and restoration are essential to conserve biodiversity and maintain resilience in fire-sensitive white-sand forests.
Keywords: Anthropogenic fire; Repeated burning; White-sand Forest; Madagascar; Forest structure; Species diversity; Community composition; Importance Value Index

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