Relationship between the Decomposition Process of Coarse Woody Debris and Fungal Community Structure as Detected by High-Throughput Sequencing in a Deciduous Broad-Leaved Forest in Japan

<div><p>We examined the relationship between the community structure of wood-decaying fungi, detected by high-throughput sequencing, and the decomposition rate using 13 years of data from a forest dynamics plot. For molecular analysis and wood density measurements, drill dust samples were collected from logs and stumps of <i>Fagus</i> and <i>Quercus</i> in the plot. Regression using a negative exponential model between wood density and time since death revealed that the decomposition rate of <i>Fagus</i> was greater than that of <i>Quercus</i>. The residual between the expected value obtained from the regression curve and the observed wood density was used as a decomposition rate index. Principal component analysis showed that the fungal community compositions of both <i>Fagus</i> and <i>Quercus</i> changed with time since death. Principal component analysis axis scores were used as an index of fungal community composition. A structural equation model for each wood genus was used to assess the effect of fungal community structure traits on the decomposition rate and how the fungal community structure was determined by the traits of coarse woody debris. Results of the structural equation model suggested that the decomposition rate of <i>Fagus</i> was affected by two fungal community composition components: one that was affected by time since death and another that was not affected by the traits of coarse woody debris. In contrast, the decomposition rate of <i>Quercus</i> was not affected by coarse woody debris traits or fungal community structure. These findings suggest that, in the case of <i>Fagus</i> coarse woody debris, the fungal community structure is related to the decomposition process of its host substrate. Because fungal community structure is affected partly by the decay stage and wood density of its substrate, these factors influence each other. Further research on interactive effects is needed to improve our understanding of the relationship between fungal community structure and the woody debris decomposition process.</p></div

Results of the PCA ordination of individual pieces of <i>Fagus</i> CWD and fungal OTUs.

<p>Fungal OTUs are presented by subdivision or class to avoid redundancy.</p

Results of the SEM analysis of the decomposition rate index of <i>Quercus</i> CWD.

<p>See the legend of <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0131510#pone.0131510.g005" target="_blank">Fig 5</a> for an explanation of the values and arrows.</p

SEM analysis results of the decomposition rate index of <i>Fagus</i> CWD.

<p>Numbers beside the arrows represent path coefficients. All paths included in the analysis are presented. Straight single-headed arrows represent causal pathways. Curved, double-headed arrows indicate covarying variables. Thick, straight, black arrows indicate significant causal pathways at the level of <i>p</i> < 0.05. Thick, gray, curved arrows indicate significant covarying relationships at the level of <i>p</i> < 0.05. Dashed, straight, curved arrows indicate non-significance (<i>p</i> > 0.05).</p

Two-way cluster analysis of fungal OTUs and both <i>Fagus</i> and <i>Quercus</i> CWDs.

<p>Each row represents a CWD, and each column represents an OTU. Columns are clustered according to the abundance of OTUs on CWDs, whereas rows are clustered according to the composition of OTUs. Numbers in the heat map show the matrix coding values, which were relative percent abundance within the matrix.</p

Results of the PCA ordination of individual pieces of <i>Quercus</i> CWD and fungal OTUs.

<p>Fungal OTUs are presented by subdivision or class to avoid redundancy.</p

Appendix D. Evaluation of the starvation at the pre-dispersal predation.

Evaluation of the starvation at the pre-dispersal predation

Appendix A. Rank correlation (Kendall's Tau) matrix of annual sound seed production.

Rank correlation (Kendall's Tau) matrix of annual sound seed production

Appendix C. Evaluation of the satiation at the pre-dispersal predation.

Evaluation of the satiation at the pre-dispersal predation

Appendix B. Evaluation of the pollination efficiency.

Evaluation of the pollination efficiency