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UV-B–induced forest sterility: Implications of ozone shield failure in Earth’s largest extinction

机译：UV-B引起的森林不育：臭氧屏蔽层破坏对地球最大灭绝的影响

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Although Siberian Trap volcanism is considered a primary driver of the largest extinction in Earth history, the end-Permian crisis, the relationship between these events remains unclear. However, malformations in fossilized gymnosperm pollen from the extinction interval suggest biological stress coinciding with pulsed forest decline. These grains are hypothesized to have been caused by enhanced ultraviolet-B (UV-B) irradiation from volcanism-induced ozone shield deterioration. We tested this proposed mechanism by observing the effects of inferred end-Permian UV-B regimes on pollen development and reproductive success in living conifers. We find that pollen malformation frequencies increase fivefold under high UV-B intensities. Surprisingly, all trees survived but were sterilized under enhanced UV-B. These results support the hypothesis that heightened UV-B stress could have contributed not only to pollen malformation production but also to deforestation during Permian-Triassic crisis intervals. By reducing the fertility of several widespread gymnosperm lineages, pulsed ozone shield weakening could have induced repeated terrestrial biosphere destabilization and food web collapse without exerting a direct “kill” mechanism on land plants or animals. These findings challenge the paradigm that mass extinctions require kill mechanisms and suggest that modern conifer forests may be considerably more vulnerable to anthropogenic ozone layer depletion than expected.
机译：尽管西伯利亚圈套火山活动被认为是地球历史上最大灭绝，二叠纪末期危机的主要原因，但这些事件之间的关系仍不清楚。然而，从灭绝间隔来看，裸子植物花粉化石的畸形表明生物胁迫与森林的脉冲状衰退同时发生。据推测，这些晶粒是由火山引起的臭氧屏蔽层退化引起的紫外线B（UV-B）辐射增强引起的。我们通过观察推断的最终二叠纪UV-B方案对活针叶树花粉发育和繁殖成功的影响，测试了该提议的机制。我们发现在高UV-B强度下，花粉畸形频率增加了五倍。出乎意料的是，所有树木都可以幸存，但是在增强的UV-B下进行了灭菌。这些结果支持以下假设：UV-B胁迫加剧不仅可能导致花粉畸形的产生，而且还可能导致二叠纪-三叠纪危机期间的森林砍伐。通过降低几种普遍存在的裸子植物谱系的繁殖力，脉冲式臭氧层防护层的削弱可能会引起陆地生物圈的反复失稳和食物网的崩溃，而不会对陆地植物或动物施加直接的“杀灭”机制。这些发现挑战了灭绝需要杀死机制的范式，并表明现代针叶林可能比预期的更容易受到人为破坏臭氧层的影响。

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