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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 [...]

Hondo spruce (Picea jezoensis var. hondoensis (Mayr) Rehder)) is separately distributed among several mountainous regions in central Japan as remnant populations of the last glacial period. To identify factors that affect Hondo spruce seedling regeneration on decaying logs, we investigated the relationships between climatic conditions, log properties, including decay type by fungi, and Hondo spruce seedling density on logs using data from seven subalpine Hondo spruce forests in central Japan. The results showed that the presence of soft rot was associated with higher seedling density, and the effect of brown rot in sapwood and white rot in heartwood on the predicted number of spruce seedlings on logs switched from positive to negative with increasing temperature and precipitation. Because soft rot occurs under humid conditions, the use of forest management techniques that increase the number of logs with soft rot in sapwood (e.g., by keeping the forest floor moist) are recommended for the sustainable regeneration of Hondo spruce. However, the relationships between wood decay type and seedling regeneration can also be affected by climate condition and thus are more complex than previously thought. Key words: coarse woody material, decay type, forest regeneration, precipitation, subalpine forest. Des populations reliques isolees d'epicea de Hondo (Picea jezoensis var. hondoensis (Mayr) Rehder), vestiges de la derniere periode glaciaire, subsistent dans plusieurs regions montagneuses du centre du Japon. Dans le but d'identifier les facteurs qui influencent la regeneration de semis d'epicea de Hondo sur les billes en decomposition, nous avons etudie les relations entre les conditions climatiques, les caracteristiques des billes incluant le type de carie causee par les champignons, ainsi que la densite des semis d'epicea de Hondo sur les billes, a l'aide de donnees provenant de sept forets subalpines d'epicea situees dans le centre du Japon. Les resultats montrent que la presence de champignons de la pourriture molle est associee a une plus forte densite de semis et que l'effet de la carie brune dans le bois d'aubier et de la carie blanche dans le bois de creur sur le nombre predit de semis d'epicea sur les billes est passe de positif a negatif a la suite d'une augmentation de la temperature et des precipitations. Etant donne que la pourriture molle se developpe en presence d'humidite, on recommande d'avoir recours a des techniques d'amenagement qui augmentent le nombre de billes avec de la pourriture molle dans le bois d'aubier (p. ex. en gardant la couverture morte humide) pour favoriser la regeneration soutenue de l'epicea de Hondo. Cependant, les relations entre le type de carie du bois et la regeneration des semis peuvent aussi etre influencees par les conditions climatiques et sont donc plus complexes qu'on le croyait. [Traduit par la Redaction] Mots-cles: materiau ligneux grossier, type de carie, regeneration forestiere, precipitation, foret subalpine., Introduction Subalpine coniferous forests dominated by Hondo spruce (Picea jezoensis var. hondoensis (Mayr) Rehder; hereafter simply 'spruce') are distributed separately among several mountainous regions in central Japan as remnant populations [...]

Context: Forest management practices that conserve biodiversity and maximize carbon sequestration under climate change are needed. Although post-windthrow salvage logging and scarification can reduce carbon dioxide (CO2) emissions within ecosystems by removing downed logs, they can greatly affect species composition. Additionally, salvage logging may increase CO2 emissions based on a cradle-to-grave analysis of salvaged wood. Objectives: We aimed to assess the effects of changes in climate, windthrow regimes and post-windthrow management on aboveground biomass, species composition, and carbon balance in the forest sector by combining forest landscape simulations and life cycle assessment (LCA). Methods: The study landscape is a 12,169 ha hemiboreal forest located in northern Japan. We simulated 115 years (2015–2130) of forest dynamics in 36 scenarios based on features of the climate, windthrow regime, and management using the LANDIS-II forest landscape model. CO2 emissions related to management and salvaged wood were estimated by LCA. Results: Increases in the windthrow area, which was more vulnerable to climate warming, caused a shift to temperate broadleaved forests and a decrease in aboveground biomass. These were accelerated by the removal of advanced seedlings and dead wood, which greatly reduced the recruitment of Picea species. The 115-year cumulative net CO2 absorption of the forest sector, including carbon balance within ecosystems and CO2 emissions estimated by LCA, greatly decreased due to salvage logging (maximum 81%) and scarification (maximum 114%). Conclusions: Leaving downed logs and advanced seedlings is recommended to conserve boreal conifers and carbon sinks and maximize net CO2 absorption under climate change. [ABSTRACT FROM AUTHOR]

The contribution of sapling banks to the coexistence of species with different shade tolerance under the "wave regeneration" regime has not been researched extensively. This study first assessed spatial and temporal variations in the relative dominance of two Abies species, Abies veitchii and Abies mariesii, with different shade tolerance in a wave‐regenerated forest. Second, we present the age structure and its spatial variation in young Abies stands (sapling stage) to exhibit the prevalence and variability of regeneration from sapling banks (defined as trees established 10 years before canopy opening). The relative dominance of A. mariesii, the more shade‐tolerant species, compared to that of A. veitchii, did not change over a period of 10 years, irrespective of stand developmental stages, indicating the importance of initial dominance in determining the local species composition. The tree ages at the sapling stage were significantly higher for A. mariesii than for A. veitchii. Approximately, 30% of all trees were likely to arise from a sapling bank, and 86% of them were A. mariesii. Age structure significantly varied between 5 × 5 m quadrats; some quadrats were dominated by A. mariesii originating from sapling banks, while others were dominated by A. veitchii that were established at the time of canopy opening. These results indicate that regeneration from sapling banks contributes to the dominance of A. mariesii and that the spatial variation in the abundance of trees originating from sapling banks is essential for the coexistence of A. mariesii with A. veitchii. [ABSTRACT FROM AUTHOR]

Although successional changes in the functional diversity (FD) of plant communities have been reported in earlier studies, the processes driving these changes remain unclear. Based on the datasets of a long-term tree census conducted during a secondary succession, we comprehensively investigated the FD and its rate of change during a secondary succession in cool, temperate secondary forests in Chichibu, Central Japan. Data from more than 30-years of observations in plots of secondary forest stands with a wide range of stand ages were used to test changes in species diversity, community-weighted means (CWMs) of each trait, FD, and their change rates. Although species diversity decreased constantly with stand age, the FD (Rao's Q) of all traits decreased significantly at the mid-successional stage, corresponding to the stem-exclusion stage. Changes in CWMs of traits indicated the directional shifts of species composition from resource-acquisitive to resource-conservative along succession, especially at the stem exclusion stage. Although the FD of each trait changed differently with succession, that of several resource-conserving traits decreased significantly at the stem exclusion stage. Based on long-term multiple chronosequence resampling, we found that stem exclusion significantly decreased the FD along a secondary succession in cool temperate forests. This sheds light on the critical role of the stem exclusion stage in shaping plant community traits, indicating the importance of this stage in forest management strategies. • We used long-term tree census data from secondary forest succession. • Analyzing functional diversity change over time using long-term and multiple chronosequence resampling techniques. • Finding the decrease in functional diversity as forests advance through the stem exclusion stage. • Highlights the crucial role of stem exclusion phase in shaping plant trait diversity. [ABSTRACT FROM AUTHOR]