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<p>Positive interactions among plants are a key in structuring alpine plant communities, particularly under severe environmental conditions. Cushion plants are widely recognized as important facilitators in alpine ecosystems, but their effects on non-vascular plants remain poorly understood. Here, we evaluated spatial associations of vascular plants and mosses with the cushion plant <i>Bolax gummifera</i> in the alpine zone of Navarino Island (55°S), the southernmost alpine environment of the Southern Hemisphere. We compared species richness, community composition, and species-level associations within and outside cushions on equatorial- and polar-facing slopes characterized by contrasting microclimatic conditions. A total of 52 species were recorded, including 34 mosses and 18 vascular plants, confirming the high importance of bryophytes in subantarctic alpine habitats. Vascular plants showed significantly higher richness within cushions than outside them on both slopes, whereas moss richness did not differ between microhabitats. Relative Interaction Index (RII) values were positive for vascular plants on both slopes, particularly on the equatorial slope, indicating stronger positive associations with cushions under more severe environmental conditions. In contrast, mosses exhibited weak or neutral RII values, suggesting lower dependence on cushion-mediated habitat amelioration at the community level. Nevertheless, several moss species showed significant positive associations with cushions, especially on the polar slope. Ordination analyses revealed that both slope aspect and cushion presence generated distinct species assemblages, highlighting the combined effects of microhabitat filtering and topographic heterogeneity on alpine community structure. Microclimatic analyses showed that the equatorial slope experienced higher thermal amplitude, lower snow persistence, lower vegetation cover, and greater substrate instability than the polar slope, despite being warmer on average. Our results demonstrate that vascular plants and mosses differ in their responses to cushion plants and emphasize the importance of aspect-driven microclimatic heterogeneity in shaping species interactions and community assembly in subantarctic alpine ecosystems.</p>

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Spatial associations of vascular plants and mosses to Bolax gummifera cushions in subantarctic alpine habitats: are they similar?

  • 期刊论文

  • 发表日期：

    2026年6月22日

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  • Manuela Méndez-Herranz,
  • Ricardo Rozzi,
  • Juan Larraín,
  • Lohengrin A. Cavieres

摘要

Positive interactions among plants are a key in structuring alpine plant communities, particularly under severe environmental conditions. Cushion plants are widely recognized as important facilitators in alpine ecosystems, but their effects on non-vascular plants remain poorly understood. Here, we evaluated spatial associations of vascular plants and mosses with the cushion plant Bolax gummifera in the alpine zone of Navarino Island (55°S), the southernmost alpine environment of the Southern Hemisphere. We compared species richness, community composition, and species-level associations within and outside cushions on equatorial- and polar-facing slopes characterized by contrasting microclimatic conditions. A total of 52 species were recorded, including 34 mosses and 18 vascular plants, confirming the high importance of bryophytes in subantarctic alpine habitats. Vascular plants showed significantly higher richness within cushions than outside them on both slopes, whereas moss richness did not differ between microhabitats. Relative Interaction Index (RII) values were positive for vascular plants on both slopes, particularly on the equatorial slope, indicating stronger positive associations with cushions under more severe environmental conditions. In contrast, mosses exhibited weak or neutral RII values, suggesting lower dependence on cushion-mediated habitat amelioration at the community level. Nevertheless, several moss species showed significant positive associations with cushions, especially on the polar slope. Ordination analyses revealed that both slope aspect and cushion presence generated distinct species assemblages, highlighting the combined effects of microhabitat filtering and topographic heterogeneity on alpine community structure. Microclimatic analyses showed that the equatorial slope experienced higher thermal amplitude, lower snow persistence, lower vegetation cover, and greater substrate instability than the polar slope, despite being warmer on average. Our results demonstrate that vascular plants and mosses differ in their responses to cushion plants and emphasize the importance of aspect-driven microclimatic heterogeneity in shaping species interactions and community assembly in subantarctic alpine ecosystems.