Ancient landscapes and the relationship with microbial nitrification

Area of Science:

• Soil microbiology
• Biogeochemistry
• Environmental science

Background:

• Ammonia oxidizing archaea (AOA) and ammonia oxidizing bacteria (AOB) are key drivers of soil nitrification.
• Their population dynamics significantly influence the global nitrogen cycle.
• Understanding factors controlling AOA and AOB distribution is crucial, as AOB increasingly contribute to nitrification in some environments.

Purpose of the Study:

• To investigate the distribution of AOA and AOB in Australian agricultural soils.
• To determine the influence of parent material geology and landscape age on AOA and AOB abundance.
• To explore potential reasons for the observed differentiation in AOA and AOB populations.

Main Methods:

• Quantification of AOA and AOB using amoA gene abundance.
• Sampling across 135 agricultural sites in Australia with diverse parent materials and geologic landscapes.
• Analysis of soil properties including pH and copper content.

Main Results:

• AOA and AOB abundances showed distinct separation correlated with the geologic age of parent rocks.
• AOB were more abundant in older, weathered, semi-arid soils of Western Australia.
• AOA dominated younger, higher pH soils of Eastern Australia, irrespective of land management.
• Western Australian soils, derived from weathered archaean laterite, were acidic and copper-deficient.

Conclusions:

• Soil parent material geology and age are significant factors structuring AOA and AOB communities in Australia.
• Copper deficiency in older Western Australian soils may limit AOA populations, explaining their lower abundance.
• These findings have implications for understanding global nitrification patterns and soil microbial diversity.