Data from: Ectomycorrhizal fungal community succession and fragmentation across subalpine forest edges nearly 3 decades postharvest

<b>Abstract</b><br/><p>Ectomycorrhizal fungi (EMF) are sensitive to stand-removing disturbances. The re-establishment of diverse EMF communities, including return of the rarer fungi typical of old-growth stands, may take longer than a century. Using smaller cutovers, with their high edge to area ratio, has the potential to accelerate postharvest EMF community recovery by increasing proximity to mature forests. By contrast, forest edges produce a fragmentation effect that could eventually inflict a negative influence on EMF taxa of the remaining forest.</p>
<p>We compared both succession and fragmentation patterns across small openings at 27 years postharvest in a high-elevation coniferous forest. We sampled 90 m transects across forest edges of nine 1-ha openings, using long-read metabarcoding of EMF from mycorrhizal root tips, and Sanger sequencing of epigeous sporocarps to assess EMF community response.</p>
<p>A timber harvesting effect on root tip EMF communities was still evident, with significant differences among species assemblages between the opening, edge and interior forest habitats. Furthermore, EMF richness of root tips in the openings declined by 27%, on average, beginning at 10 m from the forest edge, illustrating how the previously observed influence of overstory trees had not expanded into the openings during this time. An influx of multi-seral taxa into the young stands was instead likely driven by spore dispersal, which may have been facilitated in these small cutovers where regenerating saplings were never more than 50 m from mature trees. While EMF richness on tree roots was maintained in the interior forest, sporocarp fruiting was curtailed within forest edges, alongside some reductions in forest- dependent taxa, likely reflecting fragmentation stress.</p>
<p>Overall, the potential benefits of small openings appeared constrained by environmental factors, such as open canopies and limited rooting density, that delay the re-establishment of late-seral EMF species. The negative effect of edges on EMF reproduction and abundance of some taxa in the forest adjacent to the openings should be considered when designing retention forestry systems as part of sustainable forest management. Our results suggest medium to large patches of retained trees may reduce fragmentation stress and better sustain an array of late-seral forest fungi.</p>

摘要
外生菌根真菌（Ectomycorrhizal fungi, EMF）对林分移除型干扰极为敏感。多样的外生菌根真菌群落重建——包括老龄林典型稀有真菌的回迁——可能需要超过一个世纪的时间。采用高边缘面积比的小型皆伐迹地，有望通过提升与成熟林的邻近度，加速采伐后外生菌根真菌群落的恢复；与之相反，森林边缘产生的破碎化效应，最终可能对剩余林分中的外生菌根真菌类群造成负面影响。
本研究在一处高海拔针叶林中，针对采伐后27年的小型采伐迹地，对比了其群落演替与破碎化格局。我们沿着9处1公顷采伐迹地的林缘设置90米样带，通过对菌根根尖的外生菌根真菌进行长读长元条形码测序（long-read metabarcoding），并对地上子实体进行桑格测序（Sanger sequencing），以此评估外生菌根真菌群落的响应。
采伐活动对根尖外生菌根真菌群落的影响仍较为显著，采伐迹地、林缘与林内生境的物种组成存在显著差异。此外，距林缘10米处的采伐迹地内，根尖外生菌根真菌的丰富度平均下降了27%，这表明此前观测到的上层林木的影响在此期间并未扩散至采伐迹地内部。相反，多演替阶段类群向幼龄林的迁入，可能由孢子扩散驱动；在这些小型皆伐迹地中，更新幼苗与成熟林木的距离从未超过50米，这或促进了孢子传播。尽管林内林木根系的外生菌根真菌丰富度得以维持，但林缘区域的子实体结实受到抑制，依赖森林的类群数量也有所减少，这大概率反映了破碎化胁迫。
总体而言，小型采伐迹地的潜在益处受到冠层开阔、根系密度有限等环境因素的制约，这些因素延缓了晚演替阶段外生菌根真菌物种的重建。在作为可持续森林管理组成部分的保留林业系统设计中，应考虑林缘对毗邻采伐迹地的林分内外生菌根真菌繁殖及部分类群丰度的负面影响。本研究结果表明，保留中等至大面积的林木斑块，或可减轻破碎化胁迫，更好地维持一系列晚演替森林真菌类群。