A COMMUNITY-LEVEL PHYSIOLOGICAL PROFILING APPROACH TO EVALUATING IN SITU SOIL CARBON SUBSTRATE UTILIZATION AND ITS INTERACTION WITH BIOAVAILABLE NITROGEN

LEHMAN, R. MICHAEL; GARLAND, JAY L.; ZABALOY, MARÍA CELINA; MACKOWIAK, CHERYL; FREY, SERITA

Burlington, VT

Conferencia; Soil Ecology Society Conference; 2009

Soil Ecology Society of America

We used microtiter plates loaded with an oxygen-sensitive fluorophore to assay respiration of endogenous carbon and added organic substrates by soil microbial communities. The respiration of soil slurries was measured at low substrate concentrations (0.5 mg substrate per g soil) with and without added inorganic nitrogen over a short (< 7 h) incubation period in the lab. Soil samples collected from field plots that were manipulated to receive amendments of organic substrates and/or nitrogen were examined with the method. We found that the measured community respiratory response to added nitrogen in the microplate assay was significantly correlated with the analytical determinations of inorganic nitrogen in the field plots. Soils from field plots amended with non-nitrogen-containing substrates (i.e., glucose) exhibited increased respiration in the assay to nitrogen-containing substrates (i.e., amino acids). In contrast, soils from field plots amended with amino acids exhibited increased respiration of both sugars and amino acids. When no nitrogen is added during the laboratory assay, little growth occurs within the microplate wells during the incubation period based on quantitative PCR of bacterial and fungal ribosomal genes. When nitrogen is added, moderate growth (e.g., doubling) may be observed. Previous work has shown minimal effect of soil disruption during the performance of this assay and inclusion of fungal activities in the measured responses. This assay significantly advances the ability to examine in situ relations between carbon and nitrogen utilization in soils and generate ecologically-relevant community-level physiological profiles.