Land-use intensification differentially affects bacterial, fungal and protist communities and decreases microbiome network complexity

Background Soil microbial communities are major drivers of cycling of soil nutrients that sustain plant growth and productivity. Yet, a holistic understanding of the impact of land-use intensification on the soil microbiome is still poorly understood. Here, we used a field experiment to investigate the long-term consequences of changes in land-use intensity based on cropping frequency (continuous cropping, alternating cropping with a temporary grassland, perennial grassland) on bacterial, protist and fungal communities as well as on their co-occurrence networks. Results We showed that land use has a major impact on the structure and composition of bacterial, protist and fungal communities. Grassland and arable cropping differed markedly with many taxa differentiating between both land use types. The smallest differences in the microbiome were observed between temporary grassland and continuous cropping, which suggests lasting effects of the cropping system preceding the temporary grasslands. Land-use intensity also affected the bacterial co-occurrence networks with increased complexity in the perennial grassland comparing to the other land-use systems. Similarly, co-occurrence networks within microbial groups showed a higher connectivity in the perennial grasslands. Protists, particularly Rhizaria, dominated in soil microbial associations, as they showed a higher number of connections than bacteria and fungi in all land uses. Conclusions Our findings provide evidence of legacy effects of prior land use on the composition of the soil microbiome. Whatever the land use, network analyses highlighted the importance of protists as a key element of the soil microbiome that should be considered in future work. Altogether, this work provides a holistic perspective of the differential responses of various microbial groups and of their associations to agricultural intensification.

Principal Components and Classification Analysis of Manganese Content in Spring of Perennial Grassland Forage from Microecosystems of Banat Hills

The purpose of this research was to monitor the manganese (Mn) content of forage from perennial grassland microecosystems situated in the west part of Romania. Mineral and organic fertilization, since 2003, influenced the microecosystems conditions. It was used fermented sheep manure as organic fertilizer. Calamagrostis epigejos, Festuca rupicola and Trifolium repens represented mainly the Poaceae and Fabaceae families of grassland floristic matrix. It was determined the spring Mn content in the middle and at the end of May by ContrAA300 High-Resolution Continuum Source spectrometer of Analytik Jena. It was selected a number of 17 variables to compute the PC&CA model. The first three components described around 75% of total variance. The correlation coefficients for spring Mn contents of forage and mineral fertilization data were high, in 0.6 – 0.9 range. The correlation coefficients between fermented sheep manure data and spring Mn contents of forage were negatively.