Role of Leaf Litter in Above-Ground Wood Decay.

Grant T Kirker,Nathan Bechle,Stan Lebow,Jonathan Palmer,Patricia Lebow,Amy Bishell,Jed Cappellazzi

doi:10.3390/microorganisms8050696

Grant T Kirker, Nathan Bechle + Show 5 more

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https://doi.org/10.3390/microorganisms8050696

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Abstract

The effects of leaf litter on moisture content and fungal decay development in above-ground wood specimens were assessed. Untreated southern pine specimens were exposed with or without leaf litter contact. Two types of leaf litter were evaluated; aged (decomposed) and young (early stages of decomposition). The moisture content of specimens was monitored, and specimens were periodically removed for visual evaluation of decay development. In addition, amplicon-based sequencing analysis of specimens and associated leaf litter was conducted at two time points. Contact with either type of leaf litter resulted in consistently higher moisture contents than those not in contact with leaf litter. Visually, evident decay developed most rapidly in specimens in contact with the aged leaf litter. Analysis of amplicon-based sequencing revealed that leaf litter contributes a significant amount of the available wood decay fungal community with similar communities found in the litter exposed wood and litter itself, but dissimilar community profiles from unexposed wood. Dominant species and guild composition shifted over time, beginning initially with more leaf saprophytes (ascomycetes) and over time shifting to more wood rotting fungi (basidiomycetes). These results highlight the importance of the contributions of leaf litter to fungal colonization and subsequent decay hazard for above-ground wood.

Highlights

Soil contact presents a severe deterioration hazard for wood products, but the greatest volume of wood products used outdoors is not in direct contact with the ground
The purpose of this study was to demonstrate that leaf litter presents a ready source of fungal inoculum for wood above-ground and can negatively impact the performance of untreated wood
The second is that aged litter in contact with wood in above-ground scenarios contributes to increased wood decay over the 41-month exposure

Summary

Introduction

Soil contact presents a severe deterioration hazard for wood products, but the greatest volume of wood products used outdoors is not in direct contact with the ground. There has been increasing interest in using less toxic preservative systems or lower preservative retentions for wood used above-ground These preservative formulations may not be evaluated with ground-contact stake tests, and instead are evaluated using above-ground test methods. There are several standardized above-ground test methods [1], but accelerated evaluation of wood products intended for use above-ground has proven more difficult than ground contact evaluations It remains unclear how well above-ground tests characterize the hazard, or if they accelerate the rate of decay relative to in-service applications. Accumulation and decomposition of leaf litter is commonly observed in wooden structures, and it is possible that the presence of this decomposing organic matter increases the decay hazard to the adjacent wood product

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