Climate change and land management decisions have considerably altered fire regimes globally resulting in increased risks of extreme fire seasons. Fire intensity is one characteristic of fire regime which is projected to increase. However, the magnitude and impact of intense fires on plant habitat and life history characteristics (such as the soil environment or seedling recruitment) remain unclear for many species. The widespread 2019–2020 Black Summer fires across Eastern Australia provided the opportunity to examine the impact of these fires on the short-term regeneration of the Endangered Persoonia hirsuta (Proteaceae), an obligate seeding (reliant on regeneration from seed following fire) shrub presently threatened by population decline and dieback (plant death from branch and root tips backwards) of an unknown cause. In this study, we used a combination of metrics to estimate fire severity in the field at 22 plots across three fire-affected populations which we used as a proxy to understand the relative impacts of fire intensity on P. hirsuta regeneration post-fire. We also recorded the recruitment, growth, dieback and mortality of P. hirsuta seedlings at these plots over 21 months following the fires and examined whether the post-fire soil environment (carbon, nitrogen and phosphorus) was related to fire severity and seedling responses. Seedling recruitment and growth were variable across sites and showed no relationship to fire severity. However, seedling dieback and mortality were significantly higher among plots exposed to high severity fires. Additionally, characteristics of the post-fire soil environment varied by fire severity and explained variation in seedling recruitment, growth and dieback. Our work provides important evidence that already vulnerable populations of P. hirsuta may be further threatened by increasing fire severity, highlighting the importance of understanding the effects of fire on habitat and life history characteristics for threatened plants.

中文翻译：

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火灾严重程度和火灾后土壤环境影响受威胁 Persoonia hirsuta (Proteaceae) 的幼苗再生成功

气候变化和土地管理决策极大地改变了全球火灾状况，导致极端火灾季节的风险增加。火灾强度是火灾状态的一个特征，预计会增加。然而，对于许多物种来说，强烈火灾对植物栖息地和生活史特征（如土壤环境或幼苗补充）的程度和影响仍不清楚。2019-2020 年在澳大利亚东部普遍发生的黑色夏季大火为研究这些大火对濒临灭绝的Persoonia hirsuta短期再生的影响提供了机会（Proteaceae），一种专性播种（依赖于火灾后种子再生）灌木，目前受到未知原因的种群下降和枯死（植物从枝和根尖向后死亡）的威胁。在这项研究中，我们使用指标组合来估计三个受火灾影响人群的 22 个地块的火灾严重程度，我们将其用作代理来了解火灾强度对P. hirsuta火灾后再生的相对影响。我们还记录了P. hirsuta的招募、生长、枯死和死亡率在火灾发生后 21 个月内，这些地块上的幼苗，并检查了火灾后的土壤环境（碳、氮和磷）是否与火灾严重程度和幼苗反应有关。幼苗的补充和生长在不同地点之间存在差异，并且与火灾严重程度无关。然而，在遭受严重火灾的地块中，幼苗枯死和死亡率明显更高。此外，火灾后土壤环境的特征因火灾严重程度而异，并解释了幼苗补充、生长和枯萎的变化。我们的工作提供了重要的证据表明已经脆弱的P. hirsuta种群可能会因火灾严重程度的增加而受到进一步威胁，突出了了解火灾对受威胁植物栖息地和生活史特征的影响的重要性。