Elevation gradient in Ordesa Monte Perdido Microbial Observatory to study the effect of climate on soil microbial community structure

Mountain elevation gradients are invaluable sites for understanding the effects of climate change on ecosystem function, community structure and distribution. However, relatively little is known about the impact on soil microbial communities, in spite of their importance for the functioning of the soil ecosystem. Previous studies of microbial diversity along elevational gradients were often limited by confounding variables such as vegetation, pH, and nutrients. Here, we utilised an elevational transect established to minimise variation in such parameters, as part of our Ordesa and Monte Perdido Microbial Observatory in the Pyrenees, to examine prokaryotic, fungal, protist and metazoan communities throughout three consecutive years. We aimed to determine the relative influences of climate and environmental parameters on soil microbial community structure; as well as on the relationships between those microbial communities. Further, the functional diversity of heterotrophic bacteria was determined using Biolog EcoplatesTM. Prokaryotic and fungal community structure, but not alpha-diversity, correlated significantly with elevation. However, the carbon-to-nitrogen ratio appeared to affect these communities more strongly, and soil humidity to influence the functional heterotroph diversity. Considerable temporal variation was noted in soil prokaryotic community structure, consistent with a stronger influence from recent (30 d) soil temperatures than climate itself (annual means).