PNNL

Abstract

While significant progress has been made in understanding global carbon (C) cycling, the mechanisms regulating belowground C fluxes and storage are still uncertain. New molecular technologies have the power to elucidate these processes, yet we have no widespread standardized implementation of molecular techniques. To help address this gap, we have developed a crowdsourced soil core research program for analyzing molecular and microstructural data that describe soil structure, soil organic matter (SOM) chemistry, and soil microbiology. Known as the 1,000 Soils Pilot and based at the Environmental Molecular Sciences Laboratory (EMSL), we use Fourier-transform ion cyclotron resonance- (FTICR) and liquid chromatography- (LC) mass spectrometry (MS); X-ray Computed Tomography (XCT), water retention curves; metagenomic sequencing; and standard biogeochemical measurements to enable new insights into soil C cycles. To emphasize cross-site comparability, we provide standardized sampling materials and protocols, and all data are generated on dedicated instruments with optimized settings. Data and analytic workflows from the 1000 Soils Pilot will populate a unique continental-scale database of soil molecular properties, as part of the EMSL Molecular Observation Network (MONet) User Program. Here, we describe the sampling and data processing approach developed in the 1000 Soils Pilot and present an early use case describing differences in SOM chemistry, soil structure, and chemical and biological properties across forest soils exposed to differing wildfire regimes. We observed decreases in soil respiration, microbial biomass, and enzymatic activity in soils with high frequency moderate severity burns. Additionally, we observed increases in SOM nominal oxidation state of carbon (NOSC) with burn frequency in the top 10 cm and NOSC increases with burn history in the 20-30 cm depth for soil from moderate severity burns.