Higher Sensitivity of Microbial Network Than Community Structure under Acid Rain

Area of Science:

• Environmental microbiology
• Soil science
• Biogeochemistry

Background:

• Acid rain (AR) poses a global environmental threat with significant impacts on soil ecosystems.
• The nitrogen (N) cycle is crucial for global N balance and climate stabilization, regulated by soil microorganisms.
• The influence of AR on the structure and complexity of soil N-cycle microbial communities remains largely unknown.

Purpose of the Study:

• To investigate the effects of simulated acid rain on the structure and complexity of soil nitrifying and denitrifying microbial communities.
• To identify changes in microbial network complexity, keystone taxa abundance, and their correlation with soil properties.
• To assess the impact of AR on soil N2O emissions.

Main Methods:

• Intact soil core experiment with simulated acid rain (pH 4.0) versus control (pH 7.5).
• Illumina amplicon sequencing of functional genes (amoA, nirS, nosZ) for nitrifying and denitrifying microorganisms.
• Analysis of microbial network structure, node connectivity, and keystone taxa abundance.
• Measurement of soil properties (pH, available phosphorus) and N2O emissions.

Main Results:

• Acid rain treatment reduced the complexity of ammonia-oxidizing archaea (AOA) and nirS-denitrifier networks but increased the complexity of nosZ-denitrifier networks.
• AR altered the abundance of keystone taxa in AOA, nirS-, and nosZ-denitrifier networks.
• No significant changes were observed in the community structure of AOA, ammonia-oxidizing bacteria (AOB), nirS-, or nosZ-denitrifiers, nor in soil N2O emissions.
• AOB community structure correlated with available phosphorus; nirS- and nosZ-denitrifier communities correlated with soil pH and available phosphorus.

Conclusions:

• Acid rain significantly impacts the complexity and keystone taxa of soil N-cycle microbial networks, with varying effects on different microbial groups.
• Soil properties like pH and available phosphorus are key drivers influencing denitrifier community structure under acid rain conditions.
• While AR alters microbial network dynamics, its direct impact on overall soil N2O emissions and community structure of major N-cycling groups may be limited in the short term.