Integration of Metagenomic and Chemical Data to Reveal Impacts of Simulated Climate Change on the Soil Biogeochemical System.

Contemporary ‘omics techniques are providing unique opportunities to peer inside the “black box” of soil microbial processes.  However, these techniques are often used observationally to characterize a soil microbial community; due to the vast quantities of high-dimensional data often generated, it is challenging to discriminate treatment-specific signals from the background noise that characterizes heterogeneous environments like soils.  Thus, robust inferences of direct environmental impacts on soil microbial processes from individual ‘omics technologies have been elusive. Integrating metagenomics analyses with other ‘omics data sets is one means of developing a broader understanding of the soil biogeochemical system. Here we link high-resolution mass spectrometry (Fourier-Transform Ion Cyclotron Resonance, “FTICR”) of soil organic matter with high-throughput metagenome sequencing to identify the impacts of 17 years of simulated climate change on soil microbial processes.

A reciprocal soil transplant experiment was initiated in 1994 in eastern Washington in which soil cores were reciprocally transplanted between two elevations (310 m and 844 m); the lower site is warmer and drier with 0.8% soil carbon, and the upper site is cooler and wetter with 1.8% soil carbon. We resampled these cores in 2013 to characterize the microbial community functional capability (metagenomics), biochemical potential of carbohydrate-active enzymes (assays), and the soil organic matter profile (FTICR).  Rigorous statistical approaches were applied to extract distinctive features from the FTICR profile and to identify metagenomic features that are differentially abundant. We find specific empirical formulae that discriminate soils by treatment, and are developing methods to mine KEGG pathways to link those formulae with the enzyme assay data and metagenomic features. In this way, we can infer relationships between the metagenomic capability, observed enzymatic potential and the soil organic matter to form specific, testable hypotheses of the impact of climate change on the soil biogeochemical system.