The extramatrical mycelium of ectomycorrhizal fungi (EMF) is an important source of soil carbon and nitrogen. While the importance of recalcitrant compounds in the fungal cell wall has been explored earlier, the contribution of highly abundant but labile components, like glucans, and the role of their temporal dynamics during decomposition remains unknown. For the first time, we examined how the concentration of three main fungal cell wall components (chitin, melanin, glucans) in EMF necromass are related to necromass decomposition, over a period of 6 weeks. Although the initial concentrations of the three components were not good predictors of necromass loss, we found species–specific trends of chitin and glucans loss over time. The chitin concentration during decomposition was tightly linked to the weekly necromass degradation, with trends of chitin loss being dissimilar across fungal species. Chitin concentration was positively correlated with the mass loss in the first week, but in the remaining 5 weeks, it was found to be weakly negatively correlated with mass loss. The similarity in susceptibility to the decomposition of glucans and chitin likely compensates for the impacts of interspecific differences in their initial concentration, leading to overall similar decomposition patterns. Alternatively, other, non-measured, components (e.g., glycoproteins, N content) may contribute to explaining similar decomposition patterns. Our results indicate that ectomycorrhizal necromass decomposition processes differ from those of plant litter decomposition with, unlike in plants, differences in initial concentrations of major structural carbohydrates (e.g., glucans) being unrelated to differences in decomposition rates. These findings indicate that the decomposition of fungal material cannot be inferred from assumptions based on data provided by studies of plant decomposition.

中文翻译：

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了解主细胞壁多糖对外生菌根真菌坏死物分解的影响

外生菌根真菌 (EMF) 的基质外菌丝体是土壤碳和氮的重要来源。虽然早期已经探索了真菌细胞壁中顽固化合物的重要性，但高度丰富但不稳定的成分（如葡聚糖）的贡献以及它们在分解过程中的时间动力学的作用仍然未知。在 6 周的时间内，我们首次检测了 EMF 坏死团中三种主要真菌细胞壁成分（几丁质、黑色素、葡聚糖）的浓度与坏死团分解的关系。尽管这三种成分的初始浓度并不是坏死物质损失的良好预测指标，但我们发现几丁质和葡聚糖随时间推移的物种特异性趋势。分解过程中的几丁质浓度与每周的坏死团降解密切相关，不同真菌物种的几丁质损失趋势不同。几丁质浓度与第一周的质量损失呈正相关，但在剩余的 5 周内，发现它与质量损失呈弱负相关。对葡聚糖和几丁质分解的敏感性的相似性可能补偿了它们初始浓度的种间差异的影响，从而导致总体上相似的分解模式。或者，其他未测量的成分（例如，糖蛋白、N 含量）可能有助于解释类似的分解模式。我们的结果表明，外生菌根坏死物质分解过程不同于植物凋落物分解过程，与植物不同，主要结构碳水化合物（例如，葡聚糖）与分解率的差异无关。这些发现表明，真菌材料的分解不能从基于植物分解研究提供的数据的假设中推断出来。