梅木 清

Summary Unraveling the mechanisms of home‐field advantage (HFA) is essential to gain a complete understanding of litter decomposition processes. However, knowledge of the relationships between HFA effects and microbial communities is lacking. To examine HFA effects on litter decomposition, we identified the microbial communities and conducted a reciprocal transplant experiment, including all possible combinations of soil and litter, between sites at two elevations in cool‐temperate forests. Soil origin, rather than HFA, was an important factor in controlling litter decomposition processes. Microbiome‐wide association analyses identified litter fungi and bacteria specific to the source soil, which completely differed at a low taxonomic level between litter types. The relative abundance of these microbes specific to source soil was positively correlated with litter mass loss. The results indicated that the unique relationships between plant litter and soil microbes through plant–soil linkages drive litter decomposition processes. In the short term, soil disturbances resulting from land‐use changes have the potential to disrupt the effect of soil origin and hinder the advancement of litter decomposition. These findings contribute to an understanding of HFA mechanisms and the impacts of land‐use change on decomposition processes in forest ecosystems.

Abstract Interspecific relationships between growth and survival are critical determinants of tree species diversity maintenance in forests. The trade‐offs between growth and survival in co‐occurring tree species are believed to arise along a continuum of life‐history strategies. For example, co‐occurring species range from those that grow slowly and survive well in resource‐poor environments to those that grow quickly but have low survival rates in resource‐rich environments. However, uncertainties remain regarding how growth–survival trade‐offs are related to species traits, tree sizes or environmental conditions. We examined how the relationships between species traits and growth–survival relationships shift in response to changes in stem sizes and across census periods with different climate conditions (frequency of strong winds, drought intensity) across 45 co‐occurring tree species based on 23 years of growth and survival records in a warm temperate rainforest on Yakushima Island, Japan. We developed hierarchical Bayesian models of relative growth and survival rates, including leaf traits, wood density and 95‐percentile maximum stem diameter as explanatory variables. We tested the relationships between estimated trait‐mediated growth–survival relationships and the indices of climate events during five census periods. Each trait's effects on growth–survival relationships differed across the five census periods in response to climate conditions. Interspecific growth–survival relationships affected by a single trait axis for leaves or wood tended to be negative. In contrast, those affected by the maximum stem diameter tended to be positive. Such trends increased with more frequent strong winds or more intense droughts. The single‐trait effects on growth–survival relationships were stronger for smaller sizes than for larger sizes. For all traits combined, we found a significant growth–survival trade‐off only for small‐sized stems in three of five census periods. Synthesis. Our results indicate that the effect of species traits on the growth–survival relationships depended on tree sizes, the census periods or both in response to the frequency or intensity of climate events. We argue the importance of incorporating spatial and temporal variations in environmental conditions into long‐term data from tree census to predict forest dynamics.

Habitat partitioning is a key mechanism that allows coexistence of species, but studies of sympatric mesocarnivore species’ habitat partitioning have mostly been conducted at pre-determined single spatial scales, without considering the spatial scales of habitat selections (SSHS). In this study, we applied a multi-scale occupancy modeling approach to the camera trap data of five sympatric mesocarnivore species in a cool temperate forest in eastern Japan to accurately estimate their habitat preferences and SSHS. We constructed hierarchical Bayesian models with a detection process assumed separately from the occupancy process. This was done to consider inherent detection bias in the camera trap data, due to variations of local environmental variables between camera trap deployment points. In the occupancy model, avoidance of conifer plantations and preference for sloped sites were detected for multiple species, and estimated SSHS for these significant habitat preferences showed both intraspecific and interspecific differentiation for most focal species. These results signify that a mesocarnivore species’ habitat selection occurs simultaneously at multiple spatial scales. Furthermore, they also imply that interspecific differences of habitat selection processes and the spatial scales at which they occur both contribute to the coexistence of sympatric mesocarnivores in their natural habitats. In the detection model, bias in site use was indeed detected, reinforcing the existing argument for the necessity of its consideration in habitat selection modeling of survey data.