Cheptsov, Vladimir Sergeevich

Actinomycetes are key functional group of soil microorganisms that play a critical role in organic matter decomposition and the regulation of biogeochemical cycles in tropical ecosystems. This study provides a comprehensive analysis of actinomycete community structure and the physiological traits of cultivable strains in soils and litter from two protected areas in Southern Vietnam: Bidoup and Cat Tien Nature Reserves. We combined culture-based and molecular approaches, including quantification of cultivable actinomycetes, assessment of strain tolerance to abiotic stresses, evaluation of enzymatic activities, and high-throughput 16S rRNA gene sequencing to determine the taxonomic composition of prokaryotic communities. Actinobacteria were found to be dominant across soils, with clear differences between soils and litter. Litter communities were relatively uniform across elevations, whereas soil communities displayed pronounced variation. Cultured Streptomyces strains exhibited broad stress tolerance and high enzymatic activity, underscoring their ecological significance in tropical soil functioning.

The article presents the results of an 18-month field experiment assessing the impact of 11 mulching substrates used in urban soils on a range of physical, chemical, and biological properties. The following substrates were studied: serpentine, marble, volcanic tuff, foam glass, coconut chips, painted and unpainted pine chips, large and small fractions of larch bark, and large and small fractions of pine bark. The substrates used were shown to have no negative impact on pH, total carbon (Corg) content, or its water-soluble forms (Cws), and no effect of the substrates on soil bulk density. The use of mulching substrates on urban soils contributed to an increase in the biological activity of the soil prokaryotic complex and a decrease in the number of sanitary-indicator and potentially pathogenic bacteria (Escherichia coli) in the soil, which reduces potential risks to the health of the urban population. The most favorable soil properties, based on the totality of the studied parameters, are formed under organic mulching substrates consisting of fine-sized particles, coconut chips and larch bark. An increase in the content of microscopic fungi in the upper horizon of urban soil under a 5-cm-thick mulch layer was detected. This may pose potential risks to human health due to the allergenic and potentially pathogenic properties of some soil micromycetes and requires further research. The obtained results allow us to recommend mulching urban soils with organic substrates not only for decorative purposes but also to enhance biological activity and, consequently, improve the biological condition of soils in anthropogenically transformed conditions.