Relative importance of climate, vegetation, and spatial factors in the community and functional composition of wood-inhabiting fungi in discontinuously distributed subalpine spruce forests

Wood-inhabiting fungi are critically important for the decomposition of coarse woody debris (CWD). To evaluate the relative importance of climate, vegetation, and spatial factors in the functional composition of fungal communities that inhabit CWD in discontinuously distributed subalpine Hondo spruce (Picea jezoensis (Sieb. & Zucc.) Carr. var. hondoensis (Mayr) Rehder) forests, a metabarcoding analysis was conducted on spruce deadwood samples obtained from six subalpine forests in central Japan using a high-throughput DNA sequencing technique. We detected 454 fungal operational taxonomic units (OTUs) from 67 spruce CWDs and determined that spatial factors explained a larger fraction of community variation than environmental (climate and vegetation) factors at all six study sites. However, environmental factors explained a larger fraction than spatial factors if we excluded data from one site that is geographically distant from other study sites. The OTU number and the occurrence of brown-rot fungi were positively associated with mean annual temperature and negatively associated with mean annual precipitation. Similarly, the principal component of forest vegetation significantly affected the OTU number and occurrence of brown-rot fungi. Precipitation seasonality was positively associated with the OTU number of undefined saprotrophs. These results suggest that fungal OTUs belonging to different functional groups respond differently to environmental variables. Key words: brown-rot fungi, climate, coarse woody debris, functional group, fungal metabarcoding. Les champignons xylophages sont particulierement importants pour la decomposition des debris ligneux grossiers (DLG). Dans le but d'evaluer l'importance relative du climat, de la vegetation et des facteurs spatiaux dans la composition fonctionnelle des communautes fongiques qu'on retrouve dans les DLG des forets subalpines d'epicea du Japon (Picea jezoensis (Sieb. & Zucc.) Carr. var. hondoensis (Mayr) Rehder) reparties de facon discontinue, une analyse de metabarcoding a ete realisee sur des echantillons de bois mort d'epicea, preleves dans six forets subalpines du centre du Japon, a l'aide d'une technique de sequencage d'ADN a haut debit. Nous avons detecte 454 unites taxonomiques operationnelles (UTO) fongiques provenant de 67 DLG d'epicea. Nous avons determine que les facteurs spatiaux expliquaient une plus grande proportion de la variation des communautes que les facteurs environnementaux (climat et vegetation) dans l'ensemble des six sites etudies. Cependant, les facteurs environnementaux expliquaient une plus grande proportion que les facteurs spatiaux si nous excluons les donnees provenant d'un site geographiquement distant des autres sites a l'etude. Le nombre d'UTO et l'occurrence des champignons de carie brune etaient positivement associes a la temperature moyenne annuelle et negativement associes a la precipitation moyenne annuelle. De la meme facon, la composante principale de la vegetation forestiere avait une influence significative sur le nombre d'UTO et l'occurrence des champignons de carie brune. La saisonnalite de la precipitation etait positivement associee au nombre d'UTO de saprophytes non identifies. Ces resultats indiquent que les UTO fongiques appartenant a differents groupes fonctionnels reagissent differemment aux variables environnementales. Mots-cles: champignons de carie brune, climat, debris ligneux grossiers, groupe fonctionnel, metabarcoding.
Introduction Coarse woody debris (CWD) constitutes an important part of forest ecosystems and is a large sink of carbon and nutrients as well as a habitat for a variety of [...]