Abstract Temperate forests ecosystems are threatened by declines and diseases worldwide. Causes have been investigated during the last decades allowing, in some cases, to relate such deterioration to climate change or pathogens but, in many cases, causes have not yet been elucidated. In recent decades, a phenomenon of grouped mortality, whose etiology remains unknown, has been observed in the two most distributed Nothofagus species of North Patagonian forests. This study aimed to assess sapwood-inhabiting fungal diversity of N. dombeyi and N. pumilio trees in healthy and affected stands in order to determine whether health condition shape these fungal communities, to characterize such patterns and, to seek for the likely pathogens associated with tree damage. Seven sites in Los Alerces National Park (Chubut, Argentina), were sampled seasonally for two years. Eighty-eight fungal taxa were recovered and identified. Spatial heterogeneity across plant compartments was found, involving community composition and structure, with stem harbouring greater diversity than root. It was found that the sapwood in both Nothofagus species was inhabited by different fungal species, in high richness and showing different patterns according to health condition and plant compartment. Health condition was a stronger driver of N. dombeyi sapwood-inhabiting fungal community than it was for N. pumilio; the latter evidenced plant compartment as a stronger driver of such community. Nothofagus pumilio presented higher frequency of decomposition agents in both affected and healthy trees than it was in N. dombeyi, indicating a greater wood deterioration of its stands. More decomposition agents and potential pathogens have been found in symptomatic stands of N. dombeyi than in healthy stands, although their frequency patterns do not allow the inference of conclusions about the primary fungal agent causing tree mortality. Our findings suggest a secondary role of living-wood-inhabiting mycobiota in tree damage processes as an expression of tree stress caused by climatic factors.

中文翻译：

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巴塔哥尼亚边材栖息的真菌群和 Nothofagus 树死亡率：根据树种、植物区系和健康状况的多样性模式

摘要 温带森林生态系统受到世界范围内衰退和疾病的威胁。在过去的几十年里，人们对原因进行了调查，在某些情况下，可以将这种恶化与气候变化或病原体联系起来，但在许多情况下，原因尚未阐明。近几十年来，在北巴塔哥尼亚森林中分布最广的两种 Nothofagus 物种中观察到了群体死亡现象，其病因尚不清楚。本研究旨在评估健康和受影响林分中居住边材的 N. dombeyi 和 N. pumilio 树的真菌多样性，以确定健康状况是否会影响这些真菌群落，表征此类模式，并寻找与树木损坏。Los Alerces 国家公园（阿根廷丘布特）的七个地点，进行了两年的季节性采样。回收并鉴定了 88 个真菌类群。发现植物隔间的空间异质性，涉及群落组成和结构，茎比根具有更大的多样性。发现两种 Nothofagus 物种的边材都居住着不同的真菌物种，丰富度高，并根据健康状况和植物区室呈现不同的模式。与 N. pumilio 相比，健康状况是 N. dombeyi 边材真菌群落的更强驱动力；后者证明植物隔间是此类社区的更强大驱动力。Nothofagus pumilio 在受影响和健康的树木中表现出比 N. dombeyi 更高的分解剂频率，表明其林分的木材退化程度更高。在冬虫夏草有症状的林分中发现的分解剂和潜在病原体比在健康林分中发现的多，尽管它们的频率模式不允许推断出导致树木死亡的主要真菌剂的结论。我们的研究结果表明，生活木栖真菌群在树木损坏过程中的次要作用是气候因素引起的树木压力的表现。