Root endophytic bacterial and fungal communities in a natural hot desert are differentially regulated in dry and wet seasons by stochastic processes and functional traits

Taniguchi, Takeshi*; Isobe, Kazuo*; Imada, Shogo*; Eltayeb, M. M.*; Akaji, Yasuaki*; Nakayama, Masataka; Allen, M. F.*; Aronson, E. L.*

Science of the Total Environment, 899, p.165524_1 - 165524_13, 2023/11

https://doi.org/10.1016/j.scitotenv.2023.165524

Dryland ecosystems experience seasonal cycles of severe drought and moderate precipitation. Desert plants typically have patchy distributions, and many may develop symbiotic relationships with root endophytic microbes to survive under the repeated wet and extremely dry conditions. Although community coalescence has been found in many systems, the colonization by functional microbes and its relationship to seasonal transitions in arid regions are not well understood. Here we examined root endophytic microbial taxa, and their traits in relation to their root colonization, during the dry and wet seasons in a hot desert of the southwestern United States. We used high-throughput DNA sequencing of 16S rRNA and ITS gene profiling of five desert shrubs, and analyzed the seasonal change in endophytic microbial lineages. In summer, Actinobacteria increased, although this was not genus-specific. For fungi, Glomeraceae selectively increased in summer. In winter, Gram-negative bacterial genera, including those capable of nitrogen fixation and plant growth promotion, increased. Neutral model analysis revealed a strong stochastic influence on endophytic bacteria but a weak effect for fungi, especially in summer. The taxa with higher frequency than that predicted by the neutral model shared environmental adaptability and symbiotic traits, whereas the frequency of pathogenic fungi was at or under the predicted value. These results suggest that community assembly of bacteria and fungi is regulated differently. The bacterial community was affected by stochastic and deterministic processes via the bacterial response to drought (response trait) and beneficial effect on plants (effect trait). For fungi, mycorrhizal fungi were selected by plants in summer. The regulation of beneficial microbes by plants in both dry and wet seasons suggests the presence of plant-soil positive feedback in this natural desert ecosystem.

Shift in the rhizosphere microbial communities between growing- and low-temperature dormant seasons in a northern hardwood forest

Nakayama, Masataka; Tateno, Ryunosuke*

Plant and Soil, 17 Pages, 2023/00

https://doi.org/10.1007/s11104-023-06391-y

Microbial communities within the soil surrounding plant roots (rhizosphere) are distinct from those in the non-rhizosphere soil because of root exudation and symbiosis with plant roots and play important roles in plant growth. However, seasonal variations in these rhizosphere microbial communities are not well known, especially during the plant's dormant season in cool temperate forests. We investigated the rhizosphere microbial communities in a cool-temperate deciduous broad-leaved forest at the growing season (mid-summer) and at the beginning and end of the plant's dormant season (early winter and early spring) using metabarcoding of prokaryotic 16S rRNA genes and fungal ITS region, microbial functional prediction, and co-occurrence network analysis. The rhizosphere dominant prokaryotic subgroup (occupying 19.4 3.2% of relative read counts) had non-significant seasonal fluctuations, and their relative read counts were correlated with physicochemical properties, including pH and water content. In contrast, the relative read count of ectomycorrhizal fungi was 1.4 times higher in the rhizosphere than that in the bulk soil in mid-summer. However, the relative read counts of ectomycorrhizal fungi within rhizospheres in winter and spring (28.5 18.9% and 20.8 13.8%, respectively) were similar to that in bulk soil (25.8 18.7% and 22.4 17.1%, respectively). Ectomycorrhizal fungi reduced their occupancy within the rhizosphere during the plant's dormant seasons, whereas rhizosphere-dominant prokaryotic communities were stable during the seasonal change, implying the importance of prokaryotic rather than ectomycorrhizal fungal communities in the processes occurring within the rhizosphere during dormant seasons.

Rapid measurement of the chloride diffusion coefficient in concrete from combination of non-steady-state migration experiment and EPMA

Ogino, Masataka*; Owaki, Eiji*; Shirase, Mitsuyasu*; Nakayama, Masashi

Konkurito Kogaku Nenji Rombunshu (DVD-ROM), 39(1), p.703 - 708, 2017/07

no abstracts in English

Carbon and nitrogen cycling in forest; Is interdisciplinary collaboration needed?

Katata, Genki*; Fukushima, Keitaro*; Koarashi, Jun; Yamaguchi, Takashi*; Watanabe, Makoto*; Nagano, Hirohiko; Nakayama, Masataka*; Tateno, Ryunosuke*; Kinose, Yoshiyuki*

no journal, , 

no abstracts in English

Moderately elevated nitrogen deposition altering soil carbon dynamics

Nagano, Hirohiko*; Nakayama, Masataka; Katata, Genki*; Fukushima, Keitaro*; Yamaguchi, Takashi*; Watanabe, Makoto*; Atarashi-Andoh, Mariko; Tateno, Ryunosuke*; Hiradate, Shuntaro*; Koarashi, Jun

no journal, , 

Characterizations of formed biofilms and microbial communities on microplastics in coastal rivers of Japan

Battulga, B.; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plastic debris in the aquatic environment has become a growing concern due to their long-term ecological consequences. The current study is focused on microbial community composition on microplastics (MPs; sizes 5 mm) and characteristics of MP-associated biofilms in coastal river environments of Japan in order to understand the impact of MP-associated biofilms on aquatic organic matter cycling. The aims of the current study are i) extraction and characterization of microbial biofilms on MPs and ii) identification of diversity and composition of microbial communities on MP surfaces and in surrounding surface waters and sediments. The samples were collected from two coastal rivers during 2021-2022 on a seasonal basis. In this study, we proposed a new method to extract biofilms from MPs using ultrasound-assisted syringe treatment for isotopic analysis. Morphotypes of MPs and associated specific microbial taxa as well as seasonal differences were also observed.

Nitrogen mineralization in surface and subsurface layers at forest ecosystems having different soil types

Nakayama, Masataka; Abe, Yukiko; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Plants take up nitrogen mainly from surface soil, while under the nutrient competition, they utilize nitrogen from subsurface soil layers. However, nitrogen dynamics in the subsoil layer is unclear. Here, we investigated the soil profiles (0-60 cm depth) of net nitrogen mineralization and nitrification rates at four Japanese broad-leave forest having two different soil types (volcanic ash and non-volcanic ash soil). The results showed that net nitrogen mineralization decreased with increase of soil depth in the sites of volcanic ash soil, but the trend was not observed in the sites of non-volcanic ash soil. When the rates represented per unit soil volume, the vertical differences in nitrogen mineralization were non-significant for these two soil types. Similar to the factors regulating the spatial variations of nitrogen dynamics, the vertical trends were regulated by the soil total carbon and nitrogen contents and microbial biomass. These results suggested that the quantities of soil organic material and microbes regulated both of the horizontal and vertical differences in the nitrogen dynamics, and that the subsurface soil, as well as surface soil, was quantitatively important nitrogen source for plants.

Importance of canopy absorption of atmospheric ammonia in a fragmented deciduous broad-leaved forest in Hokkaido

Katata, Genki*; Yamaguchi, Takashi*; Watanabe, Makoto*; Fukushima, Keitaro*; Nakayama, Masataka; Nagano, Hirohiko*; Koarashi, Jun; Tateno, Ryunosuke*; Kubota, Tomohiro

no journal, , 

no abstracts in English

Priming effects in forest soils with different parent materials

Abe, Yukiko; Nakayama, Masataka; Atarashi-Andoh, Mariko; Koarashi, Jun

no journal, , 

Subsoils contain more than half of the global soil carbon. Decomposition of organic matter accumulated in the subsoil is thought to contribute significantly to heterotrophic respiration, and the supply of new organic matter to the subsoil may accelerate the decomposition of soil organic matter (priming effect). However, the carbon dynamics in the subsoil are unknown. The aim of this study was to evaluate the decomposition response to a new supply of organic matter, focusing on the differences in the interaction between organic matter and minerals in the presence and absence of volcanic ash. The surface and subsoil layers of four study sites with volcanic and non-volcanic ash soils were prepared to 64% of water holding capacity (WHC) and incubated at 20C and 30C after addition of 1% of WHC or a sucrose solution labeled at C. Sucrose addition had a positive priming effect in the lower layers of the volcanic ash soils, but the difference in carbon release after 90 days of incubation was about half of the addition in all soils, with and without sucrose addition. Therefore, sucrose addition to the soil enhanced organic matter decomposition, but it was suggested that some of the sucrose may remain in the soil.

A Measurement method for diffusivity coefficient of concrete by application of EPMA to an electrophoretic test of non-static state

Ogino, Masataka*; Owaki, Eiji*; Shirase, Mitsuyasu*; Nakayama, Masashi

no journal, , 

no abstracts in English