engleski

Effect of Biogeochemical Interface Formation on the Microbial Abundance and Diversity in Matured Soil‐Like Systems and Natural Soil During the Plant Litter Degradation

Multitude of microhabitats and biogeochemical interfaces (BGIs) make soil one the most heterogeneous and complex ecosystems that microorganisms can inhabit. The formation of BGIs depends on the mineral composition of soil and the presence of easily available nutrients, which in turn strongly influences the establishment and development of microbial communities. In this experiment, we studied the effect of plant litter addition on the microbial abundance and diversity in well‐defined soil‐like systems and one natural Luvisol, which had been under agricultural use. Soil‐like systems were matured for over two years to allow BGI formation. Four “artificial soils” that consisted of quartz sand and silt and varied in presence of montmorillonite, illite, charcoal and ferrihydrite, were inoculated with microorganisms extracted from an agricultural soil together with sterile manure. Manure was reapplied after 562 days to maintain microbial activities. The matured artificial soils as well as the natural Luvisol were incubated with 15N and 13C labelled potato and maize litter and incubated in the dark at 14°C and 60 % of the respective water holding capacity. Total nucleic acids were extracted from soil samples taken at 0, 7, 21 and 63 days after the plant litter addition. Abundance of bacteria and fungi as well as the respective community structure was assessed based on amplified ribosomal genes. The gene copy numbers for bacteria and fungi were comparable in all soils. Despite the plant litter addition no significant increase in bacterial and fungal abundance was observed over the time. rRNA (“transcripts”) values were higher in artificial soils treated with plant litter when compared to the control soils. The increase in active community abundance in artificial soils was observed directly after the litter addition, whereas in natural Luvisol possibly due to the nutrient reaction with pre‐existing complex BGIs, the increase was delayed. Molecular DNA‐fingerprinting suggests that both the bacterial and fungal community structure depends on soil composition as well as on litter addition and time. 16S rRNA profiles showed no significant differences in “active” bacterial communities among artificial soils. These results suggest that the soil composition influences the overall microbial structure whereas the plant litter addition conceals said effect on active bacterial community.

Biogeochemical interfaces ; soil mineral composition, litter degradation ; microbial communities

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