Fire regimes are shifting in ponderosa pine (Pinus ponderosa Lawson & C. Lawson)-dominated forests, raising concern regarding future vegetation patterns and forest resilience, particularly within high-severity burn patches. The southwestern US has recently experienced a marked increase in large fires that produce large, high-severity patch interiors, with few surviving trees. These areas could be more susceptible for forest loss and conversions to alternative vegetation types than areas closer to the forest edge with more available seed sources. To better understand forest recovery, we surveyed ponderosa pine regeneration within edge and core areas (>200 m from edge) of high-severity patches in ten fires that burned between 1996 to 2008 across Arizona and New Mexico, USA. Specifically, we compared regeneration density, height, and canopy cover in patch edge and core areas and used generalized linear models to investigate the abiotic and biotic factors that contribute to ponderosa pine seedling establishment and density. High-severity burn-patch edge and core plots were not significantly different in seedling density, height, or canopy cover across fires. Seedling establishment was more likely at higher-elevation mesic sites and less likely when Gambel oak (Quercus gambelii Nutt.) was more abundant. Seedling density was negatively impacted by shrub, grass, and Gambel oak cover. Regeneration density varied among fires but analysis of regeneration in aggregated edge and core plots showed that abundance of seed availability was not the sole factor that limited ponderosa pine regeneration, probably because of surviving tree refugia within high-severity burn patches. Furthermore, our findings emphasize that ponderosa pine regeneration in our study area was significantly impacted by xeric topographic environments and vegetation competition. Continued warm and dry conditions and increased wildfire activity may delay the natural recovery of ponderosa pine forests, underscoring the importance of restoration efforts in large, high-severity burn patches.

中文翻译：

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水分和植被覆盖限制了美国西南部高烈度烧伤斑块中的美国黄松的再生

在以美国黄松为主的森林中，火势正在发生变化，这引起了人们对未来植被格局和森林复原力的担忧，特别是在高烈度烧伤斑块内。美国西南部最近经历了大火的明显增加，大火产生了大型，高强度的斑块内饰，几乎没有幸存的树木。与距离森林边缘更近，种子来源更多的地区相比，这些地区更容易遭受森林的破坏和向其他植被类型的转化。为了更好地了解森林恢复，我们调查了1996年至2008年之间在亚利桑那州和美国新墨西哥州发生的10次大火中高强度斑块的边缘和核心区域（距边缘> 200 m）内的美国黄松再生。具体来说，我们比较了再生密度，高度，以及斑块边缘和核心区域的树冠覆盖，并使用广义线性模型来研究有助于黄松松树苗建立和密度的非生物和生物因素。高强度烧伤斑块边缘和核心地块在整个大火中的幼苗密度，高度或冠层覆盖率均无显着差异。在高海拔的内陆地区，幼苗定植的可能性更大，而当甘贝栎（Quercus gambelii Nutt。）更丰富时，定植的可能性就较小。灌木，草和Gambel橡树覆盖物对幼苗密度产生负面影响。火灾之间的再生密度各不相同，但对聚集的边缘和核心地块的再生分析表明，丰富的种子可利用性不是限制黄松松树再生的唯一因素，这可能是由于在高强度烧伤斑块中尚存的树木fu虫所致。此外，我们的研究结果强调，我们研究区的黄松树的再生受到干旱地形环境和植被竞争的显着影响。持续的温暖和干燥条件以及增加的野火活动可能会延迟黄松松树林的自然恢复，从而强调了在高强度高强度大块烧伤中进行恢复工作的重要性。