This study investigated the effects of rice husk and rice husk biochar on root rot (caused by Cylindrocarpon destructans and Fusarium solani) of ginseng (Panax ginseng) and on soil organisms. The effects were compared between paddy-converted and upland soils characterised by high and low nutrient content, respectively. The prevalence of root rot disease in the upland soil decreased in plots treated with rice husk at 5.2 Mg ha⁻¹ compared to the untreated control. Small differences in soil chemical properties between different treatments suggested the role of biotic factors in the suppression of the disease. In both soils, the lowest hyphal growth of Fusarium solani was observed in soil collected from plots treated with rice husk at 5.2 Mg ha⁻¹. The results suggested that the low incidence of root rot disease was due to the suppressive effect of soil on pathogenic fungi in the treated upland soil. Principal component analysis of phospholipid fatty acid results suggested that changes in microbial community structure contributed to soil suppressiveness in the paddy-converted soil. The highest density of fungivorous nematodes was observed with rice husk at 5.2 Mg ha⁻¹ in the paddy-converted soil, and Aphelenchus sp. collected from the plots were successfully cultured on F. solani and C. destructans. This observation showed that the fungivorous nematodes have potential to suppress pathogenic fungi by feeding on them. It was shown that rice husk can be used in control of root rot disease while promoting the growth of beneficial organisms suppressing pathogenic fungi and that the effect may differ by soil type.

Reducing management intensity according to the topography of pastures can change the dominant plant species from sown forages to weeds. It is unclear how changes in species dominance in plant community drive spatial variation in soil bacterial community characteristics and functions in association with edaphic condition. Analysing separately the effects of both plant communities and soil chemical properties on bacterial community is crucial for understanding the biogeographic process at a small scale. In this paper, we investigated soil bacterial responses in five plant communities (two forage and three weed), where >65% of the coverage was by one or two species. The structure and composition of the bacterial communities in the different microbiome were analysed using sequencing and their characteristics were assessed using the Functional Annotation of Prokaryotic Taxa (FAPROTAX) and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathways. Firmicutes and Planctomycetes responded only to one specific plant community, and each plant community harboured unique operational taxonomic units (OTUs) at the species level. There were a large percentage of uniquely absent OTUs for specific plant communities, suggesting that a negative effect is critical in the relationship between plants and bacteria. Bacterial diversity indices were influenced more by soil chemical properties than by plant communities. Some putative functions related to C and N recycling including nitrogen fixation were correlated with pH, electrical conductivity (EC) and nutrient levels, and this also implied that some biological functions, such as ureolysis and carbon metabolism, may decline when fertilisation intensity is reduced. Taken together, these results suggest that a shift of dominant species in plant community exerts individual effects on the bacterial community composition, which is different from the effect of soil chemical properties.

It is more efficient to select and monitor a few climate-sensitive organisms to assess the impacts of climate change on agroecosystems. In this study, indicator species of climate change in agroecosystem in South Korea were selected through analytical hierarchy process and an expert questionnaire survey. Climate sensitivity, agroecosystem symbolism, survey easiness, identification easiness, and public interest were selected as criteria for indicator species, with weights of 0.38 (±0.15), 0.23 (±0.13), 0.18 (±0.11), 0.14 (±0.09), and 0.07 (±0.06), respectively. According to these criteria, 30 indicator species were finally selected from six taxonomic groups of plants, aquatic invertebrates, bees, terrestrial beetles, butterflies, and spiders as follows. Seven plant species were selected: Taraxacum officinale, Capsella bursa-pastoris, Veronica persica, Hypochaeris radicata, Lamium amplexicaule, Trigonotis peduncularis, and Conyza sumatrensis. Seven aquatic invertebrate species were selected: Pomacea canaliculata, Cybister chinensis, Hydrochara affinis, Sternolophus rufipes, Hydaticus grammicus, Appasus japonicus, and Rhantus suturalis. Five butterfly species were selected: Eurema mandarina, Chilo suppressalis, Pieris rapae, Papilio xuthus, and Colias erate. Three spider species were selected: Argiope bruennichi, Larinioides cornutus, and Neoscona adianta. Four bee species were selected: Vespa velutha nigrithorax, V. simillima simillima, V. mandarinia, and V. simillima xanthoptera. Four species were selected for terrestrial beetles: Pheropsophus javanus, P. jessoensis, Platydracus brevicornis, and Chlaenius micans. The selected species are expected to be used as indicators for assessing the impacts of climate change in agroecosystems in the future.