Fine partitioning of epiphyte habitat within Johansson zones in tropical Australian rainforest trees

For over three decades, the Johansson zones have been widely used in epiphyte studies as a way of stratifying the host tree into habitat zones, however, the usefulness of this system has been questioned. We test the effectiveness of the Johansson zones by grouping epiphyte species by the substrate and microclimatic attributes of their individual occurrences and assessing the fidelity of these groups to the Johansson zones. Habitat characteristics were recorded for every individual epiphyte on 30 trees in the lower montane rainforests of north-eastern Australia. Twenty-four epiphyte species were agglomerated into four groups using Ward’s method. Group 4 was highly distinct and included shade loving species and nomadic vines from the lower zones of the host trees. Group 3 contained species from the most exposed habitats. Group 1 had higher light levels and lower substrate thickness than Group 2, yet both groups had close to identical distributions over the Johansson zones. This suggests t...三十余年来，约翰松生境分区（Johansson zones）作为将宿主树木划分为不同生境分区的方法，被广泛应用于附生生物（epiphyte）研究领域，但该分类系统的实用价值一直备受质疑。本研究通过根据附生生物个体出现位置的基质（substrate）与微气候（microclimatic）属性对其进行聚类，并评估这些聚类群与约翰松生境分区的契合度，以此检验约翰松生境分区的有效性。研究人员对澳大利亚东北部低山雨林内30棵宿主树木上的所有附生生物个体的生境特征进行了记录。本研究采用沃德聚类法（Ward's method）将24种附生生物聚为4个类群：第4类群特征极为鲜明，涵盖耐阴物种以及源自宿主树木下部生境的游走附生藤本；第3类群的物种均来自光照暴露程度最高的生境；第1类群的光照水平高于第2类群，但其基质厚度更低；不过两类群在约翰松生境分区中的分布模式几乎完全一致。这表明……