Soil Bacterial Community Along an Altitudinal Gradient in the Sumaco, a Stratovolcano in the Amazon Region

Abstract

Our study is a pioneering exploration of the microbiome in the soil of the Sumaco stratovolcano and an assessment of the effects of an elevational gradient and related physicochemical soil parameters on richness and community structure. The Sumaco, as an isolated Amazonian stratovolcano, may be among one of the least studied ecosystems in Ecuador and perhaps the Amazon region. Universal patterns remain unresolved or available information inconclusive to establish a supported consensus on general governing processes by which elevation and its associated environmental gradients may determine the microbial richness and community structure. We tested a recent proposal on how microbial diversity responds to montane gradients, placing a central role in soils as potentially independent of altitude along an elevational gradient. Correlations and effects among soil physicochemical parameters and altitude were contrasted against richness and community structure through quantitative ecology. The most informative physicochemical parameter in our assessment of bacterial community structure was neither pH nor altitude, but sulfur, which was mostly independent of the other tested parameters. We established a positive effect of richness by parameters associated with metallic cations such as Mn2+, and CEC, which were negatively correlated to altitude and pH. The possible relation between the significant role of sulfur on bacterial community structure with the unique geological origin of the Sumaco stratovolcano should be examined in the context of specialized sulfur metabolisms and additional information on community structure and environmental constraints. Our study establishes an initial baseline for further explorations of microbial diversity in this unexplored tropical stratovolcano.

The microbiome of the ice-capped Cayambe Volcanic Complex in Ecuador

“…Correlations between elevation and diversity in microbial ecology can mask several underlying ecological and physicochemical parameters (Lanzén et al, 2016). Previous studies have found environmental parameters that were significantly independent of elevation, and where the latter factor was secondary to other parameters in explaining the structure of bacterial communities (Fierer et al, 2011;Díaz et al, 2022). Although we acknowledge the possibility of confounding or unaccounted factors that could be underlying elevation as a significant component for bacterial diversity, such as soil moisture, soil nutrient status, substrate availability, and substrate quality, (Meier et al, 2010;Nottingham et al, 2015), we have also included as part of our assessment a set of 18 physicochemical parameters, whose correlations with the observed community diversity and structure are discussed in the next paragraphs.…”

“…Increments in biodiversity at lower glacial altitudes have been reported not only at the prokaryotic scale but also for macroinvertebrates and other groups of multicellular organisms (Milner et al, 2001;Jacobsen and Dangles, 2012;Cauvy-Fraunié and Dangles, 2019). A recent synthesis on the effect of altitude on soil bacteria diversity can be found in Díaz et al (2022), which shows that the issue is currently not fully understood and lacks universal consensus.…”