A trait-based understanding of wood decomposition by fungi

雩风三日

A trait-based understanding of wood decomposition by fungi
一种基于特征的对真菌分解木材的理解

     As the primary decomposers of organic material in terrestrial ecosystems, fungi are critical agents of the global carbon cycle. Yet our ability to link fungal community composition to ecosystem functioning is constrained by a limited understanding of the factors accounting for different wood decomposition rates among fungi. Here we examine which traits best explain fungal decomposition ability by combining detailed trait-based assays on 34 saprotrophic fungi from across North America in the laboratory with a 5-y field study comprising 1,582 fungi isolated from 74 decomposing logs. Fungal growth rate (hyphal extension rate) was the strongest single predictor of fungal-mediated wood decomposition rate under laboratory conditions, and accounted for up to 27% of the in situ variation in decomposition in the field. At the individual level, decomposition rate was negatively correlated with moisture niche width (an indicator of drought stress tolerance) and with the production of nutrient-mineralizing extracellular enzymes. Together, these results suggest that decomposition rates strongly align with a dominance-tolerance life-history tradeoff that was previously identified in these isolates, forming a spectrum from slow-growing, stress-tolerant fungi that are poor decomposers to fast-growing, highly competitive fungi with fast decomposition rates. Our study illustrates how an understanding of fungal trait variation could improve our predictive ability of the early and midstages of wood decay, to which our findings are most applicable. By mapping our results onto the biogeographic distribution of the dominance-tolerance trade-off across North America, we approximate broad-scale patterns in intrinsic fungal-mediatedwood decomposition rates.

   真菌作为陆地生态系统中有机质的主要分解者，是全球碳循环的关键因子。然而，我们将真菌群落组成与生态系统功能联系起来的能力受到了对真菌之间不同木材分解速率的因素了解有限的限制。在这里，我们通过在实验室中对来自北美的34种腐养真菌进行详细的基于特征的分析，并结合一项5年的现场研究，研究了哪些性状最能解释真菌分解能力，该研究包括从74块分解木材中分离出的1582种真菌。在实验室条件下，真菌生长速率(菌丝扩展速率)是真菌介导的木材分解速率的最强单一预测因子，在田间分解的原位变异中占27%。在个体水平上，分解速率与水分生态位宽度(干旱胁迫耐受性的指标)和营养矿化胞外酶的产生呈负相关。总之，这些结果表明，分解速率与之前在这些分离菌中发现的优势耐受性生活史权衡一致，形成了一个从生长缓慢、耐胁迫、分解能力差的真菌到快速生长、高度竞争、分解速率快的真菌的光谱。我们的研究说明了对真菌性状变异的理解如何能够提高我们对木材腐烂早期和中期的预测能力，这是我们的发现最适用的。通过将我们的结果映射到北美优势-耐受性平衡的生物地理分布上，我们近似了内在真菌介导的木材分解率的大范围模式。