Sapwood and heartwood affect differentially bacterial and fungal community structure and successional dynamics duringQuercus petraeadecomposition

Abstract

In forests, bacteria and fungi are key players in wood degradation. Still, studies focusing on bacterial and fungal successions during the decomposition process depending on the wood types (i.e. sapwood and heartwood) remain scarce. This study aimed to understand the effect of wood type on the dynamics of microbial ecological guilds in wood decomposition. Using Illumina metabarcoding, bacterial and fungal communities were monitored every 3 months for 3 years from Quercus petraea wood discs placed on forest soil. Wood density and microbial enzymes involved in biopolymer degradation were measured. We observed rapid changes in the bacterial and fungal communities and microbial ecological guilds associated with wood decomposition throughout the experiment. Bacterial and fungal succession dynamics were very contrasted between sapwood and heartwood. The initial microbial communities were quickly replaced by new bacterial and fungal assemblages in the sapwood. Conversely, some initial functional guilds (i.e. endophytes and yeasts) persisted all along the experiment in heartwood and finally became dominant, possibly limiting the development of saprotrophic fungi. Our data also suggested a significant role of bacteria in nitrogen cycle during wood decomposition.

Acidisoma silvae sp. nov. and Acidisomacellulosilytica sp. nov., Two Acidophilic Bacteria Isolated from Decaying Wood, Hydrolyzing Cellulose and Producing Poly-3-hydroxybutyrate

“…Dominance of bacteria belonging to Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes has been reported considering different wood species [5,[14][15][16][17]. If these phyla are representative of the bacterial communities colonizing deadwood, it is important to note that the related bacterial classes or genera differ according to the tree species, the decay stage, and the type of wood [5,[17][18][19][20]. While bacteria are poorly effective at decomposing dead wood compared to fungi, a few studies have shown that they are primarily involved in the decomposition of cellulose and pectin as well as in N fixation [21][22][23][24].…”

“…Deadwood decomposition plays an essential role in forest ecosystems as it maintains the soil fertility and the physico-chemical balance of the biogeochemical cycles in these ecosystems (e.g., carbon (C) cycle, recycling of nitrogen (N), and micronutrients) [1]. This process is mainly performed by a succession of decomposers including insects, fungi, and bacteria that interact to progressively decompose and recycle the nutrients [2][3][4][5]. It also depends on abiotic environmental factors such as humidity, pH, or temperature that are also known to impact deadwood decomposition rates [6].…”

“…Concerning decaying wood, an important biomass and a broad diversity of bacteria have been reported across the wood decomposition process, suggesting that the involvement of bacteria in this process does not seem negligible [2]. Dominance of bacteria belonging to Proteobacteria, Actinobacteria, Acidobacteria, and Bacteroidetes has been reported considering different wood species [5,[14][15][16][17]. If these phyla are representative of the bacterial communities colonizing deadwood, it is important to note that the related bacterial classes or genera differ according to the tree species, the decay stage, and the type of wood [5,[17][18][19][20].…”

“…These strains have been isolated from acidic environments (Sphagnum peat (pH 4.5) and peat soil (pH 4.2)) and are psychrotolerant, capable of growing at temperature down to 2 °C. Representatives of the Acetobacteraceae family (Alphaproteobacteria) to which they belong, have been commonly identified from acidic terrestrial and aquatic environments such as acid mine drainages, acidic hot springs, and acidic bogs [26][27][28][29][30] as well as in forest soils and decaying wood [5,31,32]. The two species of Acidisoma already described are Gram-negative, non-motile coccobacilli covered with large polysaccharide capsules.…”

Dispersal changes soil bacterial interactions with fungal wood decomposition

“…On the contrary, substrate release and fungal biomass formation during wood decay may affect soil bacterial community through substrate acidification, fungal metabolites or degradable C source, etc. [ 26 – 28 ]. However, there is little documentation on the interactions between soil bacterial community and wood decomposition [ 29 ].…”