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<p>Relict populations of <i>Taxus baccata</i> at their southern range limits are increasingly threatened by climate-induced recruitment failure. Understanding the spatial and functional drivers of establishment in these marginal environments is critical for conservation. We analyzed recruitment dynamics in a Mediterranean <i>Fagus sylvatica</i> forest in Northern Greece, utilizing 30 sampling plots to evaluate how distance from nearest adult trees (possible parental) and proximity to streams dictate recruit survival and vigor. Results reveal a distinct ontogenetic shift in spatial recruitment. Seedlings (&lt; 1.3&#xa0;m height) exhibited a significant non-linear Janzen-Connell distribution, peaking at ~ 2&#xa0;m from the adult tree trunk (Quadratic GLM, <i>p</i> = 0.017). For the sapling stage (≥ 1.3&#xa0;m height), this distribution shifted to a strict negative exponential decay (<i>p</i> &lt; 0.001), identifying the adult tree sub-canopy as a vital microclimatic refuge. At the landscape scale, we identified a “quantity vs. quality” trade-off driven by a “hydraulic switch” at a 30-meter distance from the stream. Within the riparian core (≤ 30&#xa0;m), recruits exhibited vigorous vertical “competitor” architecture (allometric slope <i>β</i> ≈ 0.85). Conversely, in the Upland Zone (&gt; 30&#xa0;m), recruits adopted a “stunted” stress-tolerator form (<i>β</i> ≈ 0.57) which is likely to mitigate hydraulic failure during severe Mediterranean summer droughts (&lt; 7&#xa0;mm precipitation). We propose a two-tiered conservation strategy: a 30-meter “Sanctuary Zone” to protect high-vigor phenotypes and a 100-meter buffer managed via Continuous Cover Forestry. Maintaining continuous canopy cover to provide potential nurse-plant facilitation is likely essential to safeguard the microclimatic stability required for the long-term persistence of this relict population.</p>

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Ontogenetic shifts and architectural plasticity define the regeneration niche of Taxus baccata at its southern dry limit

  • 期刊论文

  • 出版模式：

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  • 发表日期：

    2026年8月4日

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  • N. Oikonomakis,
  • S. Drakouli,
  • P. Ganatsas,
  • M. Tsakaldimi

摘要

Relict populations of Taxus baccata at their southern range limits are increasingly threatened by climate-induced recruitment failure. Understanding the spatial and functional drivers of establishment in these marginal environments is critical for conservation. We analyzed recruitment dynamics in a Mediterranean Fagus sylvatica forest in Northern Greece, utilizing 30 sampling plots to evaluate how distance from nearest adult trees (possible parental) and proximity to streams dictate recruit survival and vigor. Results reveal a distinct ontogenetic shift in spatial recruitment. Seedlings (< 1.3 m height) exhibited a significant non-linear Janzen-Connell distribution, peaking at ~ 2 m from the adult tree trunk (Quadratic GLM, p = 0.017). For the sapling stage (≥ 1.3 m height), this distribution shifted to a strict negative exponential decay (p < 0.001), identifying the adult tree sub-canopy as a vital microclimatic refuge. At the landscape scale, we identified a “quantity vs. quality” trade-off driven by a “hydraulic switch” at a 30-meter distance from the stream. Within the riparian core (≤ 30 m), recruits exhibited vigorous vertical “competitor” architecture (allometric slope β ≈ 0.85). Conversely, in the Upland Zone (> 30 m), recruits adopted a “stunted” stress-tolerator form (β ≈ 0.57) which is likely to mitigate hydraulic failure during severe Mediterranean summer droughts (< 7 mm precipitation). We propose a two-tiered conservation strategy: a 30-meter “Sanctuary Zone” to protect high-vigor phenotypes and a 100-meter buffer managed via Continuous Cover Forestry. Maintaining continuous canopy cover to provide potential nurse-plant facilitation is likely essential to safeguard the microclimatic stability required for the long-term persistence of this relict population.