The effect of aboveground long-term low-dose ionizing radiation on soil microbial diversity and structure

Abstract

Studies investigating the diversity and structure of soil microbial systems in response to ionizing radiation are scarce. In particular, effects of long-term low-dose radiation is rarely studied because of its unique conditions. In this study, an area in Chengdu, China, which has been irradiated by the radionuclide thorium-232 for more than 10 years was investigated. Four groups of samples with absorbed dose rates ranging from 192.906 ± 5.05 to 910.964 ± 41.09 nGy/h were collected to analyze the compositional and functional changes of the soil microbial systems in the region. The diversity and structure of the soil microbial systems were determined using high-throughput sequencing. Our results showed that long-term low-dose ionizing radiation had no significant effect on soil bacterial diversity, but had a great impact on fungal diversity. Long-term ionizing radiation strongly affected soil microbial community structure. Long-term low-dose ionizing radiation was shown to have a promoting effect on iron-oxidizing bacteria and ectomycorrhizal fungi and have an inhibiting effect on predatory or parasitic fungi, further affecting the soil C/N ratio. This study is of great reference significance for future research on the impact of long-term low-dose ionizing radiation on soil ecosystems.

Plant–microorganism–soil interaction under long-term low-dose ionizing radiation

“…Moreover, the abundance of Ectomycorrhizal fungi in the high group is 6 times that of the medium group, 13 times that of the low group, and 0 in the blank group. This indicates that under long-term ionizing radiation stress, plants transfer the main task of absorbing nutrients to symbiotic microorganisms mainly composed of Ectomycorrhizal fungi, resulting in significantly longer specific root length than that of the blank group, while the proportion of root dry matter is significantly lower than that of the blank group ( Li et al, 2022 ; Cheng et al, 2023 ).…”

“…In general, plants usually enhance their resistance by stimulating root-driven microbial communities when facing environmental stress and the same is true when subjected to nuclear radiation stress ( Guesmi et al, 2022 ). Recent studies also indicated that under LLR conditions, plants tend to reduce aboveground biomass and invest more organic matter underground, thereby promoting the nutrient acquisition of the root-microbial system and improving the ecosystem’s adaptability to long-term nuclear radiation ( Li et al, 2022 ; Cheng et al, 2023 ). According to previous studies, there are mainly two ways for plants to promote the nutrient acquisition of the root-microbial system, namely the “nitrogen mineralization effect” and the “symbiotic microbial effect,” which will lead to changes in soil carbon and nitrogen cycling and enzyme activity.…”

Soil Microbes and Plant-Associated Microbes in Response to Radioactive Pollution May Indirectly Affect Plants and Insect Herbivores: Evidence for Indirect Field Effects from Chernobyl and Fukushima

“…Here, another example of a radioactively exposed field is given. Chengdu in China was contaminated by low-dose 232 Th for more than 10 years, and Cheng et al (2023) [ 104 ] investigated the diversity and composition of microbes in 20 soil samples of which soil type, moisture, and pH did not differ. They found that fungal diversity was significantly reduced in irradiated soil groups (absorption dose rate of γ-rays: 630 nGy/h and 840 nGy/h) but not in bacterial diversity and that the compositions of both fungal and bacterial communities were affected.…”

“…Bacteria could be more adaptive than fungi in general. In fact, proteobacteria exhibiting strong adaptability predominate in soil exposed to radiation and maintain the stability of the bacterial community [ 104 ]. These findings suggest that differences in radioadaptability could drive imbalances at any taxonomic level from domain to species in the soil ecosystem.…”

“…On the other hand, based on the LC–MS analysis of Oxalis leaves in Fukushima, the abundance of Streptomyces sp., which produces antibiotics, did not always decrease [ 125 ]. In Cheng et al (2023) [ 104 ], ectomycorrhizal fungi in soil irradiated by low-dose 232 Th for more than 10 years were positively correlated with radiation intensity. The hyphae of these fungi wrap around plant root cells and form a biomembrane that not only protects plants from pathogens, chemical pollutants [ 136 , 137 ], and radiation but also helps plants absorb soil nutrients, including nitrogen and phosphorus [ 138 ].…”