Influence of southern pine beetle on fungal communities of wood and bark decomposition of coarse woody debris in the New Jersey pine barrens

Abstract

Dead coarse woody debris (fungal food resources) on the forest floor is an ignition source for forest fires. The rate of decomposition of the debris is largely influenced by fungi, determining its residence time on the forest floor. We asked if southern pine bark beetle (<i>Dendroctonus frontalis</i>) attack of pitch pine (<i>Pinus rigida</i>) alters the decomposition and fungal community of dead woody resources. Wood and bark from beetle infested and non-beetle infested resources were decomposed in litter bags on the forest floor. Decomposition was measured as mass loss and the fungal community by next-generation (PCR and Illumina metabarcoding) sequencing. Bark decomposed slower than wood and resources colonized by beetles decomposed faster than resources with no beetles. The initial differences in fungal communities colonizing the resources continued throughout the 42 months of decomposition. Fungal diversity was higher in wood than bark in initial decay stages, but significantly lower in wood than bark at the end of the 42 month incubation. In contrast, there were no significant differences in fungal communities between beetle infested and uninfested resources. The rate of decomposition of woody resources on the forest floor has great implications for the longevity of fuel sources for forest fires, however, our results indicate that beetle attacked wood poses no greater fire risk than other dead coarse woody debris regarding the residence time.