Fungal community composition and genetic potential regulate fine root decay in northern temperate forests

Abstract

Understanding how genetic differences among soil microorganisms regulate spatial patterns in litter decay remains a persistent challenge in ecology. Despite fine root litter accounting for ~50% of total litter production in forest ecosystems, far less is known about the microbial decay of fine roots relative to aboveground litter. Here, we evaluated whether fine root decay occurred more rapidly where fungal communities have a greater genetic potential for litter decay. Additionally, we tested if linkages between decay and fungal genes can be adequately captured by delineating saprotrophic and ectomycorrhizal fungal functional groups based on whether they have genes encoding certain ligninolytic class II peroxidase enzymes, which oxidize lignin and polyphenolic compounds. To address these ideas, we used a litterbag study paired with fungal DNA barcoding to characterize fine root decay rates and fungal community composition at the landscape scale in northern temperate forests, and we estimated the genetic potential of fungal communities for litter decay using publicly available genomes. Fine root decay occurred more rapidly where fungal communities had a greater genetic potential for decay, especially of cellulose and hemicellulose. Fine root decay was positively correlated with ligninolytic saprotrophic fungi and negatively correlated with ECM fungi with ligninolytic peroxidases, likely because these saprotrophic and ectomycorrhizal functional groups had the highest and lowest genetic potentials for plant cell wall degradation, respectively. These fungal variables overwhelmed direct environmental controls, suggesting fungal community composition and genetic variation are primary controls over fine root decay in temperate forests at regional scales.

Seasonality and longer-term development generate temporal dynamics in the Populus microbiome

“…Furthermore, this ectomycorrhizal response occurred with a concomitant decline in fungal plant pathogens and the fungal genus Mortierella ( Fig. 4 and 6 ), which includes many root-associated species ( 75 ) and saprotrophs that are common in decaying fine root litter and soil ( 83 , 84 ). Thus, the directional change in fungal communities we observed ( Fig.…”

Applying molecular and genetic methods to trees and their fungal communities

“…Dead plant litter is complex and diverse in composition, context-dependent by habitat and plant source. In forests, plant litter comes in large parts from leaves, needles, twigs, bark, wood chips, fine roots, fruits, or also seeds as dying or dead debris of trees with different degrees of lignification, makeup of antimicrobial compounds and water activity (a w ) values (Argiroff et al 2023;Chomel et al 2016;Freschet et al 2013;Lonsdale 1988;Ochoa-Hueso et al 2019). Aboveground litter decomposition and progressive humus generation on the soil surface (Horizon O; Fig.…”

“…It is noteworthy that the mycorrhizal fine roots are relatively shortlived. Combinations of fungal ECM and saprotrophic fungi in the rhizosphere control the speed of decay of senescent absorptive fine roots as a primary source of SOM (Angst et al 2021;Argiroff et al 2023;Jackson et al 2017;Kües et al in prep.). Mycorrhizae mediate resistance and defense reactions against belowground and aboveground biotic and abiotic threats and confer protection against soil pollution.…”

Divergent Decomposition Patterns of Leaf Litter and Fine Roots from an Urban Forest in Mid-Subtropical China

“…The fine root mass loss was positively affected by the F:B ratio in the early phase of decomposition. Argiroff et al [54] found that fine root decay was positively correlated with ligninolytic saprotrophic fungi and negatively correlated with ECM fungi ligninolytic peroxidases. The ligninolytic saprotrophic fungi maybe dominate the soil fungal community.…”