Methanotrophs in Black forest. undefined

Methanotrophic communities in upland forest soils are known to be an important methane sink. However, the variable methane fluxes from these soils suggest that large spatial heterogeneity, methanogenic activity, or association with plants may be important for this finding. To analyze this, we collected soil and rhizosphere samples from Fagus sylvatica and Pinus silvestris in a forest near Hartheim, Germany. DNA and RNA were extracted simultaneously to determine the total and active communities. Quantitative PCR and amplicon sequencing of the functional marker gene pmoA were used to investigate differences in methanotroph abundance and community composition. In addition, the abundance of methanogenic archaea was analyzed by qPCR. The results show that methanotroph abundance did not depend on soil texture or compartment, while methanogens were responsive. In addition, higher abundances of methanogens were found in the cDNA samples than in the DNA samples and tended to be found in the rhizosphere. The mcrA:pmoA copy number ratio in the RNA samples was lowest in bulk soil and rhizosphere samples in silty soils, but highest in sandy soil samples, indicating that sandy soils harbored more active methanogens than methanotrophs. Community composition analysis also showed that methanotrophs did not respond to soil texture and compartment, but differed based on activity. The predominant active methanotrophs belonged to USCɣ. Overall, our results suggest that the relationship between methanogens and methanotrophs likely explains the variable methane fluxes, with the activity of methanogens being more dependent on tree species and soil texture than methanotrophs.