Trees in agroforestry systems provide multiple ecological and economic functions. Smallholder vanilla agroforests include shade trees common across agroforestry systems, and small-statured support trees carrying the vanilla vine. Support trees have received little scientific attention so far. The objectives of our study were to assess the diversity, composition and geographic origin of support trees in vanilla agroforestry systems of north-eastern Madagascar. The region is a global biodiversity hotspot, has been undergoing a rapid land-use change and produces a large share of the globally traded vanilla spice. The studied vanilla agroforests differed in land-use history: established either directly inside forest (forest-derived) or on land previously used for slash-and-burn agriculture (fallow-derived). Among the support trees, we found 122 species of which 25% were endemic to Madagascar. The species richness per plot was four times higher in forest-derived than in fallow-derived vanilla agroforests. The species distribution was particularly uneven in fallow-derived vanilla agroforests with one species (Jatropha curcas) comprising 52% of all individuals. In forest-derived vanilla agroforests, 44% of all trees were native or endemic to Madagascar, whereas in fallow-derived vanilla agroforests only 11% were native or endemic. We conclude that there is a considerable diversity among support trees in Malagasy vanilla agroforestry. The support tree diversity is strongly affected by land-use history. Fallow-derived vanilla agroforests currently have a comparatively low species richness, yet they can play an important role in land rehabilitation, and more emphasis on growing native and endemic tree species would contribute to aligning production with conservation goals.

农林业系统中的树木提供多种生态和经济功能。小农香草农林包括农林业系统中常见的遮荫树，以及携带香草藤的小型支撑树。到目前为止，支持树几乎没有受到科学的关注。我们研究的目的是评估马达加斯加东北部香草农林业系统中支持树的多样性、组成和地理起源。该地区是全球生物多样性热点地区，土地利用变化迅速，在全球贸易香草香料中占有很大份额。所研究的香草农林在土地利用历史上有所不同：要么直接建立在森林内部（森林衍生），要么建立在以前用于刀耕火种农业的土地上（休耕衍生）。在支撑树中，我们发现了 122 种，其中 25% 是马达加斯加特有的。森林衍生的每块地块的物种丰富度是休耕香草农林的四倍。在有一个物种的休耕香草农林中物种分布特别不均匀（麻疯树）占所有个体的 52%。在源自森林的香草农林中，44% 的树木是马达加斯加本土的或特有的，而在休耕的香草农林中，只有 11% 是本地的或特有的。我们得出结论，马达加斯加香草农林业中的支持树木存在相当大的差异。支持树的多样性受到土地利用历史的强烈影响。休耕香草农林目前的物种丰富度相对较低，但它们可以在土地恢复中发挥重要作用，并且更加重视种植本地和特有树种将有助于使生产与保护目标保持一致。