Hisatomo Taki’s research while affiliated with Forestry and Forest Products Research Institute and other places

Smallholder agricultural landscapes, which are commonly found in Asian countries, harbor large areas of semi-natural grasslands because of the high density of field margins, which could potentially function as habitats for diverse pollinators. However, its function has not been fully realized owing to intense mowing management in recent years. This study clarified the ecological process by which the set-aside practice in field-margin grasslands enhances buckwheat pollination services. We conducted a field experiment over three years in Japan and investigated insect visitation and seed sets of buckwheat in fields with conventionally mowed and set-aside margins. Insects visiting buckwheat fields were more abundant in fields with set-aside field margins, and seed sets also increased in fields with set-aside margins because of increased insects. This tendency was consistently observed across all years and seasons. Moreover, insects with a broader utilization of wildflowers contributed more to the seed sets. The abundance responses to set-aside practices differed among insect groups. Non-bee insects increased with the set-aside practice, whereas bees did not. Seed sets increased with an increasing abundance of wild bees, hoverflies, and flower chafers, but not with honeybees. Our results indicate a causal link between set-aside grassland field margins and an increase in buckwheat pollination services. In particular, non-bee insects primarily drive the positive effects of set-aside practices on buckwheat pollination. We propose that exploring appropriate management of existing field margins, rather than setting grasslands inside the fields, which can boost pollinators and crop pollination services, is promising in smallholder agricultural landscapes.

Japanese oak wilt (JOW) is an epidemic disease transmitted by an insect vector, the oak platypodid beetle Platypus quercivorus. Splitting a dead tree is one of the best approaches to prevent spreading JOW because this method is not only highly effective in the extermination of the beetles but also in the availability of infested trees for fuel. However, this approach has high costs for on-site work to prepare firewood and is restricted to the Quercus genus available for fuel. Here, we investigated whether the number of newly emerged adults decreased by leaving the split logs of the infested Quercus serrata and Lithocarpus edulis in the forest. The dead trees of both species were brought to the study site, each cut into 30 cm lengths. These logs were split in half and eighth, and intact logs were prepared. We placed these logs into each trap to collect adults and measured the weight of split logs to predict water contents. In Q. serrata, the number of adults in eighth-split logs significantly decreased than those of half-split logs and intact logs. The predicted water contents of eighth-split logs were significantly low compared with those of others. In L. edulis, the number of adults collected from half- and eighth-split logs significantly decreased than those of intact logs, but the predicted water contents were not different between half- and eighth-split logs. Our results indicated effective pest control even if at least eighth-split logs of both tree species were left on the forest floor.

Land use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α‐diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ‐diversity), either due to reduced β‐diversity amplifying diversity loss or increased β‐diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α‐, β‐, and γ‐diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α‐diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α‐diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β‐diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ‐diversity and a 17% decline in phylogenetic γ‐diversity in agricultural habitats, but γ‐diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large‐scale bee diversity due to systematic γ‐diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α‐diversity, their impacts on β‐ or γ‐diversity vary, highlighting the need to study the effects of land use change at multiple scales.

Land use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α-diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ-diversity), either due to reduced β-diversity amplifying diversity loss or increased β-diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α-, β-, and γ-diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α-diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α-diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β-diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ-diversity and a 17% decline in phylogenetic γ-diversity in agricultural habitats, but γ-diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large-scale bee diversity due to systematic γ-diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α-diversity, their impacts on β-or γ-diversity vary, highlighting the need to study the effects of land use change at multiple scales.

Land use change threatens global biodiversity and compromises ecosystem functions, including pollination and food production. Reduced taxonomic α-diversity is often reported under land use change, yet the impacts could be different at larger spatial scales (i.e., γ-diversity), either due to reduced β-diversity amplifying diversity loss or increased β-diversity dampening diversity loss. Additionally, studies often focus on taxonomic diversity, while other important biodiversity components, including phylogenetic diversity, can exhibit differential responses. Here, we evaluated how agricultural and urban land use alters the taxonomic and phylogenetic α-, β-, and γ-diversity of an important pollinator taxon—bees. Using a multicontinental dataset of 3117 bee assemblages from 157 studies, we found that taxonomic α diversity was reduced by 16%–18% in both agricultural and urban habitats relative to natural habitats. Phylogenetic α-diversity was decreased by 11%–12% in agricultural and urban habitats. Compared with natural habitats, taxonomic and phylogenetic β-diversity increased by 11% and 6% in urban habitats, respectively, but exhibited no systematic change in agricultural habitats. We detected a 22% decline in taxonomic γ-diversity and a 17% decline in phylogenetic γ-diversity in agricultural habitats, but γ-diversity of urban habitats was not significantly different from natural habitats. These findings highlight the threat of agricultural expansions to large-scale bee diversity due to systematic γ diversity decline. In addition, while both urbanization and agriculture lead to consistent declines in α-diversity, their impacts on β-or γ-diversity vary, highlighting the need to study the effects of land use change at multiple scales.

In recent years, Japanese oak wilt causing mass mortality of oak trees has exhibited a significant geographical expansion. Understanding the formation history of current local populations of Platypus quercivorus Murayama, a vector of Japanese oak wilt, is important foundational knowledge for effectively preventing forest damage. In this study, we used genome-wide single nucleotide polymorphism data to infer the population genetic structure and historical demography of P. quercivorus populations in eastern Japan, where Japanese oak wilt is rapidly expanding. We found at least 3 distinct genetic groups, each of which caused Japanese oak wilt in different areas. The supported scenario suggests that 1 of 2 genetic groups in the northeast first diverged from the ancestral population, then the other group diverged from the southwestern population, followed by gene flow between the 2 groups. Recent admixtures of the 2 northeastern groups were identified at certain sites. The geographic genetic structure of the populations suggested that each genetic group experienced recent range expansion. Although genetically independent populations had caused oak tree mass mortality in their original distribution range, our results support the hypothesis that the recent geographic expansion of Japanese oak wilt outbreaks is attributed to the range expansion of these P. quercivorus groups.

Changes in tree species composition have important effects on the overall rate of litter decomposition at a community level because litter decomposability varies among species and between leaf and wood litter. To understand how changes in tree species composition affect litter dynamics and carbon sequestration at the ecosystem level, it is important to clarify interspecific variations in leaf and wood litter decomposability, and the traits driving the variation. Using field data, field experiments, and laboratory experiments, we explored rates of leaf and wood litter decomposition and their relationships to traits of ten deciduous hardwood species in a temperate forest in Japan. Rates of leaf and wood litter decomposition at the community level were also estimated by considering species‐specific litter inputs and decomposition rates. Rates of leaf and wood litter decomposition were not correlated under either field or controlled laboratory conditions. This is probably because the traits that affect decomposition rate differ between leaf and wood litter. Interspecific variation in litter decomposability of leaves and wood was generally consistent between field conditions and laboratory experiments using a single fungus, suggesting that the decomposing fungi set the species‐specific decomposition rates. Moreover, the leaf and wood traits that affected decomposition by their specific fungi were different. The aboveground input of wood litter was less than half that of leaf litter, but its half‐life was > 3 times longer, suggesting that wood and leaves make similar contributions to litter accumulation. Focusing on either leaf or wood litter alone may produce misleading estimates of how species composition changes affect litter dynamics at the community level. Our results provide insight into predicting the response of carbon dynamics to future climate change.

Trunk injection is a relatively new, environmentally friendly method to apply insecticides to trees which does not cause insecticide drift and environmental runoff. However, little is known about the effect of insecticide trunk injection on non-target arboreal ants (Hymenoptera: Formicidae) which can act as biological control agents of target tree pests. This study evaluated the effect of trunk injections on arboreal ants found on cherry trees treated with neonicotinoids (dinotefuran and thiamethoxam) for controlling the invasive longhorn beetle Aromia bungii (Faldermann) (Coleoptera: Cerambycidae). Arboreal ants represented by Crematogaster matsumurai Forel can prey on A. bungii eggs. Results of visual sampling 1 and 3 months after injections showed that injections did not reduce the number of ant species occurring on tree trunks. Additionally, injections did not eliminate 3 of 4 most abundant species on tree trunks or extrafloral nectaries including C. matsumurai. However, a decline of Lasius japonicus Santschi was observed on injected trees. Our preliminary short-term survey suggests the possibility that chemical control by trunk injection and biological control by arboreal ants are compatible in A. bungii management. However, further research is needed to clarify the mechanism of L. japonicus decline and long-term consequences of trunk injection on arboreal ant composition.

Animal-mediated pollination is an essential ecosystem service for the production of many fruit trees. To reveal the community composition of flower-visiting wild insects which potentially contribute to fruit production and to examine the effects of geographic location, local meteorological conditions and locally introduced domesticated pollinators on them, we investigated the community composition of insects visiting the flowers (hereafter, “visitors”) of apple, Japanese pear and Oriental persimmon for 1‒3 years at 20 sites around Japan. While most of the variation (82%) of the community composition was explained by tree species with a slight contribution by geographic distance (2%), maximum temperature and tree species contributed 62% and 41% of the variation in total abundance of the visitors, respectively. Though the dominant families of the visitors varied spatiotemporally, the community composition of the visitors of apple and Japanese pear clearly differed from that of Oriental persimmon. While Andrenidae and Syrphidae together accounted for 46%‒64% of the visitors of apple and Japanese pear, Apidae represented 57% of the visitors of Oriental persimmon. The taxonomic richness, diversity and evenness of the visitors were best predicted by locally introduced domesticated pollinators and local meteorological conditions of wind speed and maximum temperature. Amongst these selected factors, locally introduced domesticated pollinators could have the largest impact. It seemed to be strongly related to the reduction of taxonomic richness, diversity and evenness of the visitors, accounting for 41‒89% of the variation. Results suggested that the community composition and total abundance of potential pollinators were predominantly determined by tree species and temperature, but locally introduced domesticated pollinators could have a determinantal pressure on the taxonomic diversity of the community.

A series of monitoring of insects visiting crop flowers was conducted on several crop species around Japan. The project, which ran from 2017 to 2021, was led by NARO and funded by the Japanese Ministry of Agriculture, Forestry and Fisheries (MAFF) to determine the abundance and diversity of wild insects that could potentially contribute to crop production across Japan. Flower-visiting wild insects were captured using plastic vials during the blooming season at multiple sites for one to several years. Domesticated pollinators, Apis mellifera and Osmia cornifrons were also captured in 2017. This data includes more than 6,500 individuals of flying insects from 18 families of Hymenoptera, 33 families of Diptera, 17 families of Coleoptera, Hemiptera, Lepidoptera, Psocodea, and Neuroptera captured in 20 fields of apple (Malus pumila Mill.), Japanese pear (Pyrus pyrifolia (Burm.f.) Nakai), and Oriental persimmon (Diospyros kaki Thunb.) as of August 2023.