| 要旨トップ | 本企画の概要 | | 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

シンポジウム S07-5 （Presentation in Symposium）

#### How evergreen trees and lianas adapt to prolonged drought in tropical dry forests: a case study in Ankarafantsika National Park【E】

*Daniel EPRON（Kyoto Univ.）, Yuma SAKAUE（Kyoto Univ.）, Yutaro FUJIMOTO（Kyoto Univ., FFPRI）, Seiya SUNAYAMA（Kyoto Univ.）, Ando Harilalao RAKOTOMAMONJY（Kyoto Univ., Univ. Mahajanga）, Wataru NOYORI（Kyoto Univ.）, Tojotanjona RAZANAPARANY（Univ. Antananarivo）, Zo Lalaina RAZAFIARISON（Univ. Antananarivo）, Hiroki SATO（Kyoto Univ.）, Kaoru KITAJIMA（Kyoto Univ.）

Liana abundance increases with the seasonality of rainfall in tropical forests, and evergreen lianas and trees may compete for water during the dry season. Several studies suggest functional divergence of water use strategies between lianas and trees, with lianas experiencing less water stress and exhibiting growth advantage over trees during the dry season.
Our aim was to test the hypothesis that evergreen lianas are less drought tolerant and more water spending than evergreen trees. If so, we expected that, compared to trees, lianas should have (i) less sclerophyllous leaves, (ii) larger but fewer xylem vessels in their branches, (iii) higher predawn and midday water potentials, (iv) lower water use efficiency, (v) access to deeper water sources.
We tested our hypothesis in a seasonally dry tropical forest on a white-sand hill in Ankarafantsika National Park, north-western Madagascar (MAP, 1600 mm; dry season, April to November). We studied three liana and three tree species in June 2023, early in the dry season and seven liana and eight trees species in September 2024,later in the dry season. We measured leaf mass per area, nitrogen content and δ13C, leaf predawn and midday water potentials, diameter and density of xylem vessels of branches, and δ18O of xylem water.
We found that lianas had lower leaf mass per area, higher leaf predawn water potentials, larger and fewer xylem vessels, and lower δ18O of xylem water than trees. Overall, our results confirm that evergreen trees are more drought tolerant than lianas while evergreen lianas are more water spending than trees but not consistently across families.

日本生態学会