Using Real-Time PCR Data on Ammonia Oxidizers in the Soil to Study the Sensitivity of an Ecosystem Level Model
Abstract
The microbial processes regulating the nitrogen cycle in soil are complex and ecosystem scale model representation of these processes make several untested simplifying assumptions. One such assumption is that microbial populations are static throughout the year. Particular microbial guilds may also be neglected entirely in the simulation of particular nutrient cycles. One such population is the recently discovered complete ammonia oxidizers (comammox Nitrospira ) which can directly oxidize ammonia (NH3) to nitrate (NO3-) by curtailing the traditional two-step nitrification process into a single step. Due to the relative novelty of this organism, many traditional models simulating nitrogen cycles do not represent this one-step nitrification process, which may result in incorrect forecasts of nitrogen cycling. Here we tested the suitability of some of these assumptions, by combining work in a mechanistic ecosystem-scale model ecosys with real-time PCR (qPCR) data. We drove ecosys with meteorological data, soil physical property data, and soil chemistry data for a small forested catchment within the Huntington Wildlife Forest, NY (43°58'23.0"N, 74°13'23.9"W; Elevation 497m). Ecosys simulates microbial communities using modified Monod kinetics and allows for dynamic representation of microbial populations. By default, ecosys explicitly simulates nitrification, denitrification and nitrogen fixation processes. We compared the simulated microbial population sizes to the measured qPCR data on nitrifying bacterial communities. The qPCR data measures the number of copies of ammonia monooxygenase (amoA) genes of ammonia oxidizers (ammonia oxidizing bacteria (AOB), ammonia oxidizing archaea (AOA), complete ammonia oxidizers) in different soil horizons. We tested sensitivity of the ammonium (NH4+) substrate availability on different ammonia oxidizers (AOA, AOB, comammox). The model results suggest AOA and comammox populations dominate over AOB at low ammonium concentration. We also investigated the suitability of the model response of ammonia oxidizers for different soil ammonia (NH3) concentrations and tested the response of neglecting comammox as a microbial pathway.
- Publication:
-
AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB113.0005A
- Keywords:
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- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0439 Ecosystems;
- structure and dynamics;
- BIOGEOSCIENCES;
- 0465 Microbiology: ecology;
- physiology and genomics;
- BIOGEOSCIENCES;
- 1615 Biogeochemical cycles;
- processes;
- and modeling;
- GLOBAL CHANGE