Interactive effects of wood decomposer fungal activities and bryophytes on spruce seedling regeneration on coarse woody debris

Abstract

Decaying logs are important seedbeds in boreal and subalpine forests. However, biotic and abiotic factors and their interactions related to seedling colonization patterns on logs remain unclear. In the present study, we evaluated the influence of bryophyte communities, wood decay type (white‐, brown‐, and soft‐rot) owing to decomposer fungal activities, and environmental abiotic factors on seedling establishment in an old‐growth subalpine coniferous forest in Japan. Among the tree species recorded on the conifer logs, Picea jezoensis var. hondoensis was the most dominant. Log surfaces were covered with distinctive patches of liverwort Scapania bolanderi and moss Pleurozium schreberi (approximately 33% cover for each). Redundancy analysis showed that brown‐rot in sapwood significantly affects the bryophyte and seedling community on the logs. Generalized linear models suggested that the total bryophyte cover, Scapania cover, and white‐rot in heartwood positively associate with Picea seedling density, whereas Pleurozium cover and basal area of adjacent Picea adults negatively associate with Picea seedling density. Results of structural equation modeling suggested that the brown‐rot of sapwood positively associates with Scapania cover that has a positive effect on Picea seedling density. Furthermore, brown‐rot of sapwood inhibited the Pleurozium cover, thus contributing to the Scapania dominance on the logs. These results suggest that fungal wood decomposer activities affect colonization of Picea seedlings in an indirect way via structuring bryophyte community on the logs.

Ecological impacts of fungal wood decay types: A review of current knowledge and future research directions

“…Substrate pH is an important factor in the development of bryophyte communities (Gabriel & Bates, 2005), as it affects aspects of the performance of bryophyte species, such as spore germination (Wiklund & Rydin, 2004). Ando et al (2017) also reported that a liverwort, Scapania bolanderi, frequently dominated on brown-rotted P. jezoensis var. hondoensis logs, while a moss, Pleurozium schreberi, occurred on white-rotted spruce logs in subalpine coniferous forest.…”

Plant–plant interactions change during succession on nurse logs in a northern temperate rainforest

“…Rodents and slugs have been found to disperse lichen and bryophyte propagules (Asplund et al., 2010; Barbé et al., 2016; Kimmerer, 1994; Kimmerer & Young, 1995), and mammals use fallen logs as trails through the forest, so it could be a combination of differences in propagule dispersal ability, germination requirements, and biotic interactions that determine these changes. Alternatively, different decomposer fungi could influence bryophyte community structure on nurse logs as found in alpine forests in Japan (Ando et al., 2017; Fukasawa et al., 2019). Thus, the influence of bryophytes on tree seedlings could be mediated by other biotic interactions through a trophic cascade.…”

Plant-plant interactions change during succession on nurse logs in a northern temperate rainforest

“…Rodents and slugs have been found to disperse lichen and bryophyte propagules (Asplund, Larsson, Vatne, & Gauslaa, 2010;Barbé et al, 2016;Kimmerer, 1994;Kimmerer & Young, 1995), and mammals use fallen logs as trails through the forest, so it could be a combination of differences in propagule dispersal ability, germination requirements, and biotic interactions that determine these changes. Alternatively, different decomposer fungi could influence bryophyte community structure on nurse logs as found in alpine forests in Japan (Ando, Fukasawa, & Oishi, 2017). Thus, the influence of bryophytes on tree seedlings could be mediated by other biotic interactions through a trophic cascade.…”