A study on rhizosphere bacterial community succession along a glacier chronosequence. Chronosequence_Svalbard

Rhizosphere is a hotspot of microbial diversity and abundance and the “rhizosphere effect” is known to rule plant-microbe facilitative interactions. Little is known about the role of soil developmental stage in shaping rhizosphere microbiome in deglaciated moraine. We studied a soil chronosequence in the forefront of a receding glacier (Midtre Lovénbreen, Svalbard Island) encompassing 7 sites differentially exposed to primary succession, not isolated by distance but by the age of ecosystem evolution. Focusing on the rhizosphere of the ubiquitous plant Saxifraga oppositifolia, we assessed the diversity of bacterial communities subjected to different environmental factors across the chronosequence. By applying high-throughput sequencing, Phylochip and DNA-based fingerprinting we demonstrated that soil development was the factor shaping bacterial community in the earlier successional stage, while the rhizosphere effect was significant in soils released by the glacier since more than 20 years. Rhizosphere bacterial communities were highly similar after 20 and 100 years of soil development, differentiating at the older successional stages in the mature tundra ecosystem. We demonstrated the presence of bacterial distribution patterns influenced, besides the interaction with the plant, by environmental factors related to pedogenesis and ecosystem evolution stage.