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Background <p>Fire is a key ecological disturbance that can facilitate plant invasions, but the mechanisms driving post-disturbance competitive outcomes, especially the role of pre-existing species abundance, remain poorly understood. We conducted a greenhouse experiment using wetland plant species to test how fire and pre-disturbance dominance influence performance and competitive interactions between a widespread invasive alien grass (Urochloa arrecta)and a resident native grass (Hemarthria altissima). Fire was simulated across a gradient of invasive dominance, including native monoculture (0%), native dominance (25%), invasive dominance (75%), and invasive monoculture(100%), allowing us to assess whether post-fire competitive outcomes depend on initial community composition.</p> Results <p>The competitive advantage of invasive alien plant species (IAPS) was driven by a superior regenerative strategy rather than by consistently greater biomass production. After fire, IAPS sprout production was critically dependent onits initial dominance, more than doubling under high-abundance conditions. Crucially, high IAPS dominance suppressed the number of native plant species (NPS) sprouts and delayed their emergence. In contrast, at low pre-disturbance abundance, the IAPS exhibited reduced regenerative performance.</p> Conclusions <p>Our findings show that post-fire invasion success is density-dependent: only when already dominant does the invasive species gain a regenerative advantage by suppressing native sprout production and delaying the native emergence. These results demonstrate that pre-disturbance dominance and vegetative propagule pressure, particularly from the bud bank and clonal vegetative structures, are key mediators of post-disturbance success. Given the increasing global frequency of both fire disturbances and plant invasions, our study provides a mechanistic explanation for why fire promotes invasion under some dominance contexts but not others.</p>

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Pre-disturbance dominance, not fire alone, determines the success of an invasive alien plant species

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年6月25日

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  • Larissa Carrara,
  • Amanda C. Stuermer,
  • Dieison A. Moi,
  • Roger P. Mormul,
  • Adrián Lázaro-Lobo,
  • Bruno R. S. Figueiredo

摘要

Background

Fire is a key ecological disturbance that can facilitate plant invasions, but the mechanisms driving post-disturbance competitive outcomes, especially the role of pre-existing species abundance, remain poorly understood. We conducted a greenhouse experiment using wetland plant species to test how fire and pre-disturbance dominance influence performance and competitive interactions between a widespread invasive alien grass (Urochloa arrecta)and a resident native grass (Hemarthria altissima). Fire was simulated across a gradient of invasive dominance, including native monoculture (0%), native dominance (25%), invasive dominance (75%), and invasive monoculture(100%), allowing us to assess whether post-fire competitive outcomes depend on initial community composition.

Results

The competitive advantage of invasive alien plant species (IAPS) was driven by a superior regenerative strategy rather than by consistently greater biomass production. After fire, IAPS sprout production was critically dependent onits initial dominance, more than doubling under high-abundance conditions. Crucially, high IAPS dominance suppressed the number of native plant species (NPS) sprouts and delayed their emergence. In contrast, at low pre-disturbance abundance, the IAPS exhibited reduced regenerative performance.

Conclusions

Our findings show that post-fire invasion success is density-dependent: only when already dominant does the invasive species gain a regenerative advantage by suppressing native sprout production and delaying the native emergence. These results demonstrate that pre-disturbance dominance and vegetative propagule pressure, particularly from the bud bank and clonal vegetative structures, are key mediators of post-disturbance success. Given the increasing global frequency of both fire disturbances and plant invasions, our study provides a mechanistic explanation for why fire promotes invasion under some dominance contexts but not others.