Search

From 1994 to 2003, bark and ambrosia beetles were captured from April to November at 12 sites in the University of Tokyo Chichibu Forest, central Japan, using flight-barrier traps with alpha-pinene...

One long-standing, unresolved issue in forest management is how to achieve high levels of biodiversity conservation and commercial forestry for timber production. Retaining fallen logs on the forest floor is effective in preserving the habitats essential for many wood-dwelling organisms. However, the contributions of fallen logs toward the plant species diversity of forest understories are less clear, even though the importance of fallen logs on the emergence and survival of coniferous seedlings and saplings is well known, especially in boreal forests. This study aimed to clarify the roles of fallen logs in the maintenance of species diversity of understory vascular plants in forests. We investigated species richness and the composition of vascular plants on 319 fallen logs and in 128 forest-floor quadrats (2 × 2 m) in a 4-ha plot in a mixed coniferous and broad-leaved forest in Hokkaido, northern Japan. We also measured canopy openness in summer, surface area, wood resistance, and moss cover of fallen logs, and soil thickness in forest-floor quadrats. Additive partitioning and permutational multivariate analysis of variance (PERMANOVA) were used to examine differences in composition between quadrats and fallen logs. Generalized linear model (GLM) and canonical correspondence analysis (CCA) were also applied to test the determinants of species richness and composition in quadrats and fallen logs. In total, 83 vascular plant species were identified. For woody and herbaceous plants, several species occurred predominantly on fallen logs in comparison with quadrats. Species richness of woody plants on fallen logs was positively affected by surface area and moss cover, and negatively by wood resistance; although in quadrats it was not significantly associated with any environmental factors. Herbaceous species richness on fallen logs was also negatively influenced by wood resistance. In contrast, herbaceous species richness in quadrats was positively associated with canopy openness. These results suggest that fallen logs promote plant species diversity, including herbaceous plants, by creating habitat conditions favored in forest understory environments. This study implies that leaving fallen logs on the forest floor at logging sites contributes toward plant diversity conservation.

Serpula himantioides is a wood-decaying fungal pathogen which is widespread and causes potentially serious butt rot in living trees of numerous coniferous plantation species. This study aimed to quantify S. himantioides in the wood of Sawara cypress (Chamaecyparis pisifera) with butt rot using real-time polymerase chain reaction (real-time PCR). Species–specific primers were designed for the internal transcribed spacer 2 (ITS2) regions of ribosomal DNA (rDNA) of S. himantioides. The specificity of the designed primer set was tested by end-point PCR and amplicon sequencing. End-point PCR assays were positive for S. himantioides and negative for S. lacrymans, which belongs to the same genus as S. himantioides, Coniophora puteana of the same family as S. himantioides, and other wood decay fungi. Taxonomy assignment based on amplicon sequencing detected only Serpula spp., and most of them were identified as S. himantioides. The linearity of the calibration curve for absolute quantification by real-time PCR assays was confirmed in the range from 101 to 108 copies. This molecular assay method using real-time PCR could detect trace amounts of S. himantioides in decayed wood, showing the applicability for early diagnostics of butt rot emergence in forests.

The classical “low latitude–high defense” hypothesis is seldom supported by empirical evidence. In this context, we tested latitudinal patterns in the leaf defense traits of deciduous broadleaved (DB) and evergreen broadleaved (EGB) tree species, which are expected to affect herbivore diversity. We examined the co-occurrence of leaf defense traits (tannin and phenol content, leaf mechanical strength, leaf dry matter content, leaf mass per area, and leaf thickness) in 741 broadleaved tree species and their correlations with species geographical range in East Asian island flora. We discovered contrasting latitudinal defense strategy gradients in DB and EGB tree species. DB species employed chemical defenses (increasing tannin and phenol content) at higher latitudes and physical defenses (softer and thinner leaves) at lower latitudes, whereas EGB tree species exhibited opposite latitudinal defense patterns. The “low latitude high defense” hypothesis included a paradoxical aspect in chemical and physical defense traits across broadleaved tree species. To reconcile paradoxical defense strategies along the latitudinal gradient, we conclude that interactive correlations among leaf traits are controlled by leaf longevity, which differs between DB and EGB tree species.

Understanding how the community structures and functions of soil microbes respond to environmental changes is essential for predicting the dynamics of ecosystem functions. Elevational gradients are an ideal setting for “natural experiments” on the relationships between soil microbes and environmental factors. However, little is known about elevational patterns of soil microbial functions and their interactions with aboveground vegetation. We examined community structures and nitrogen cycling gene abundance of soil bacteria in 20 vegetation survey quadrats in cool-temperate and sub-alpine forests along an elevational gradient (1050–2000 m above sea level) in central Japan. The diversity of soil bacterial communities was investigated based on terminal restriction fragment length polymorphisms (T-RFLP) in the 16S rRNA gene. The abundance of soil bacteria and key functional groups involved in nitrogen cycling was determined by quantifying the 16S rRNA and bacterial genes related to nitrogen fixation (nifH), ammonia oxidation (amoA), and denitrification (nosZ). The terminal restriction fragment (T-RF) richness of soil bacteria showed no relationship with elevation, but was negatively associated with soil nitrate-nitrogen and the species richness of understory vegetation. The abundance of all bacteria and nitrogen functional groups showed hump-shaped relationships with elevation, and was positively associated with soil water content and understory stem density. These results highlight that community structures and nitrogen cycling gene abundance of soil microbes along the elevational gradient can be explained by soil properties associated with understory vegetation. This suggests that vegetation decline caused by environmental changes, such as climate warming, land use change, and increased herbivore density, may deteriorate soil ecosystem functions through aboveground–belowground interactions.

Elevational diversity gradients (EDGs) of vegetation are shaped by the evolutionary histories of plants as well as by ecological factors. However, few studies of EDGs have focused on the roles of phylogenetic constraints and the effects of complicated interactions among environmental factors. Here, we examine the direct and indirect effects of environmental factors in forming EDGs of forest understory vegetation. The study plots were selected along elevational gradients in cool-temperate and sub-alpine forests in the University of Tokyo Chichibu Forest of central Japan. Tree seedlings and herbs were identified, and environmental factors (elevation, soil temperature, soil pH, soil CN ratio, forest type, basal area, canopy openness, and slope) were measured in these plots. Structural equation modeling (SEM) including taxonomic and phylogenetic diversity was used to consider the causal relationships between environmental conditions and the diversity of understory vegetation. In addition, phylogenetic signals in habitat requirements were tested. The taxonomic and phylogenetic diversities of tree seedlings increased monotonically with elevation, and the same pattern was found for the taxonomic diversity of herbs. The SEM indicated that both the taxonomic and phylogenetic diversity of tree seedlings were most affected by soil properties, although the phylogenetic diversity of herbs was determined by light conditions. These results highlight the importance of environmental filtering by soil properties in shaping EDGs of tree seedlings. This study implies that phylogenetic constraints in the adaptation to soil properties should be considered when predicting changes in EDGs under environmental fluctuations.

Betula chichibuensis is a critically endangered limestone birch confined to the Chichibu and Kitakami mountains in central and northeastern Japan, respectively. In this study, we assembled and char...

Increasing evidence suggests that elevational gradients of soil fungal richness are highly variable, but few studies have examined how diversity components of each guild contribute to overall fungal diversity. Here, we aimed to disentangle the relationships between total, saprotrophic, and ectomycorrhizal fungal richness, and environmental factors across elevational gradients in cool-temperate montane forests. We observed that total and saprotrophic richness decreased but ectomycorrhizal richness increased with increase in elevation. Elevational range size and nestedness analyses illustrated that saprotrophic and ectomycorrhizal source communities were located at lower and higher elevations, respectively. The observed total and saprotrophic richness were directly influenced by soil properties and indirectly influenced by climate and plant communities. Ectomycorrhizal fungal richness was affected by climate and the dominance of ectomycorrhizal trees. We highlight that two directional source–sink dynamics lead to opposite elevational patterns between saprotrophic and ectomycorrhizal fungal richness, shaping the variation in elevational richness gradients.

Elevational gradients represent model systems for understanding the relationships between soil microbial communities and environmental factors, but the multiple influences of plant-soil linkages and climate conditions on elevational diversity gradients (EDGs) of soil microbes have never been explored. Here, we examined how climate conditions, plant diversity and soil properties affect EDGs of soil bacteria at different soil depths. Bacterial communities were investigated at four soil depths in 60 vegetation survey plots along elevational gradients in central Japan. In this study, elevational gradients reflected climate conditions, including mean annual temperature and seasonality of temperature and precipitation. Bacterial diversity decreased with elevation in the surface soil, but showed no relationship with elevation in deep soils. The structural equation modeling showed that soil bacterial diversity was directly affected by plant functional diversity, where leaf C:N ratio diversity had stronger effects than soil properties. We found that EDGs of soil bacteria were determined by the degree of indirect effects of climate conditions, via plant functional diversity and soil properties, against the direct effect of climate conditions on bacterial diversity. These findings demonstrate that community assembly of soil microbes is causally linked with climate conditions, plant functional diversity and soil properties, which determine EDGs.

Resprouting is an important functional trait for determining community dynamics and the persistence of individuals and populations. However, community-wide research on resprouting has primarily focused on severely damaged trees. We investigated resprouting from trees in a range of undisturbed natural forests along an elevational gradient in central Japan and analyzed the data at inter- and intraspecific levels. First, we formulated interspecific relationships among resprout production, parent stem growth, multi-stemmedness, and dominance in forest communities using a structural equation model (SEM). Second, we analyzed intraspecific variation in the resprout number per stem for nine resprouting species using a hierarchical Bayesian method. We found that resprout production and parent stem growth were negatively correlated, resprouting resulted in multi-stemmed adult forms, and species with multi-stemmed forms tended to be less dominant in undisturbed forest communities. We observed various intraspecific resprouting responses to parental and environmental factors. For example, soil temperature had generally positive effects for most species, whereas dbh appeared to have only weak effects on a few species. Our SEM summarized well the direct and indirect relationships of species&rsquo, traits, including resprout production, in the undisturbed forests. The observed intraspecific patterns in the resprouting responses can serve as a starting point for understanding species&rsquo, traits within this context.

Aim To examine the roles of geohistorical and ecological factors in the development of butterfly assemblages on continental islands with multiple source pools. Location The Ryukyu Islands, Japan. This arc of continental islands is located between two source islands, Kyushu and Taiwan, and contains two major straits, the Tokara and Kerama gaps. Methods A total of 489 butterfly species were identified on 59 islands, including the two source islands. The influences on species richness and rarity of latitude, area, elevation, and distances from the nearest source and from the nearest larger island were analysed using generalized linear models. The relationships between differences in area, elevation, and distance and dissimilarity between island butterfly faunas were evaluated by multiple regressions on distance matrices. The relationships between area, elevation, and distance from the source and dissimilarity to the source fauna were examined using linear models. The dissimilarity was based on the Sorensen index and its nestedness and turnover components. Results Latitude, area and isolation determined species richness and rarity, whereas differences in elevation and distance regulated species turnover between islands. The gaps between islands were associated with nestedness between island faunas. Area consistently had a negative relationship with the total dissimilarity to source fauna. The overall dissimilarity to Kyushu decreased with the distance from Kyushu, whereas dissimilarity to Taiwan increased with distance from Taiwan. Main conclusions Both environmental filtering and dispersal limitation determine the geographical patterns of butterfly assemblages in the Ryukyus. The present study focuses on the unique pattern wherein migration from Kyushu is facilitated on islands farther from Kyushu, while migration from Taiwan is inhibited on islands farther from Taiwan. The two source islands have contrasting roles that affect butterfly distributions unidirectionally. This study highlights the importance of resolving dissimilarity into nestedness and turnover components to elucidate the formation of island biota.

The mass mortality of oak trees has been prevalent in Japan since the late 1980s. The fungus Raffaelea quercivora is transmitted by an ambrosia beetle, Platypus quercivorus, which causes mortality. The beetle is able to bore galleries into the sapwood of most Fagaceae trees in Japan; however, the level of mortality caused by R. quercivora and P. quercivorus differs greatly among tree species. Previous studies by our research group have demonstrated that the virulence of R. quercivora differs among isolates when inoculated into Quercus serrata logs. However, interactions between the virulence of R. quercivora isolates and the susceptibility of other fagaceous species have yet to be elucidated. In this study, we inoculated the fresh logs of 11 fagaceous species with isolates of low and high virulence, and measured the tangential widths of discolored sapwoods 3 weeks after inoculation. Although the discoloration widths of Q. crispula sapwood were similar among all isolates, those of Q. serrata and Q. acutissima tended to increase with the more virulent isolates. Sapwood discoloration in Q. glauca, Q. acuta, Q. salicina, Lethocarpus edulis, and Castanopsis sieboldii was greatly increased by highly virulent isolates. Discoloration in Fagus japonica was not influenced by any of the isolates. The logs of Q. crispula and Q. serrata but not Q. glauca were significantly more discolored by a low-virulence isolate compared with standing trees. The various virulent isolates induced unique sapwood discoloration characteristics in each species, which may explain species-specific differences in mortality rates.

Premise of the study: Microsatellite markers were developed and characterized for the critically endangered birch Betula chichibuensis (Betulaceae) to investigate the genetic structure of this species for conservation purposes. Methods and Results: Sixteen microsatellite markers with di-, tri-, and tetranucleotide repeat motifs were developed and optimized using MiSeq paired-end sequencing. Of these, 14 were polymorphic, with two to five alleles per locus, in 47 individuals from two newly discovered populations of B. chichibuensis in Japan. Observed and unbiased expected heterozygosities per locus ranged from 0.000 to 0.617 and from 0.000 to 0.629, respectively. These markers were tested for cross-species amplification in B. maximowicziana, B. platyphylla var. japonica, and B. schmidtii. Conclusions: This set of microsatellite markers, the first developed for B. chichibuensis, will help elucidate spatial patterns of gene flow and levels of inbreeding in this species to aid its conservation.

Mountain lakes are thought to be sensitive to environmental changes, and bacterioplankton in these lakes may be suitable for monitoring the effects of global climate change. In this chapter, we discuss characteristics of the environmental conditions and bacterioplankton communities in mountain lakes, by integrating the results of our survey conducted in Japanese mountain lakes with the knowledge from previous studies. Mountain lakes have some characteristics, which can affect bacterioplankton communities significantly. There are some taxonomic groups of bacteria dominant in mountain lakes, such as the genus Polynucleobacter. These groups are also abundant in freshwater environments in low altitudes and regarded as cosmopolitans widely distributed in global freshwater environments. For some of these bacteria, their dominance in mountain lakes can be partially explained by their physiological characteristics. In addition to the environmental filtering illustrated by the dominance of these bacteria, community assembly of bacterioplankton in mountain lakes may also be regulated by other processes, including dispersal limitation and evolutionary constraint.

The article “A paradox of latitudinal leaf defense strategies in deciduous and evergreen broadleaved trees”, written by Saihanna Saihanna, Tomoe Tanaka, Yu Okamura, Buntarou Kusumoto, Takayuki Shiono, Toshihide Hirao, Yasuhiro Kubota, and Masashi Murakami, was originally published electronically on the publisher’s internet portal (currently SpringerLink) on 01 June 2018 without open access.

Premise of the study: Microsatellite markers were developed and characterized for the critically endangered birch Betula chichibuensis (Betulaceae) to investigate the genetic structure of this species for conservation purposes. Methods and Results: Sixteen microsatellite markers with di-, tri-, and tetranucleotide repeat motifs were developed and optimized using MiSeq paired-end sequencing. Of these, 14 were polymorphic, with two to five alleles per locus, in 47 individuals from two newly discovered populations of B. chichibuensis in Japan. Observed and unbiased expected heterozygosities per locus ranged from 0.000 to 0.617 and from 0.000 to 0.629, respectively. These markers were tested for cross-species amplification in B. maximowicziana, B. platyphylla var. japonica, and B. schmidtii. Conclusions: This set of microsatellite markers, the first developed for B. chichibuensis, will help elucidate spatial patterns of gene flow and levels of inbreeding in this species to aid its conservation.