Land use alters bacterial growth dynamics in soil

Area of Science:

• Soil microbiology
• Ecology
• Biogeochemistry

Background:

• Microbial growth and mortality significantly impact soil carbon cycling.
• Land use practices can impose distinct selection pressures on soil microbial communities.
• Understanding bacterial growth dynamics is key to predicting soil ecosystem functions.

Purpose of the Study:

• To measure in situ bacterial growth and mortality dynamics in cropped and successional soils.
• To investigate the influence of land use on bacterial growth characteristics.
• To determine how resource pulses affect bacterial growth and mortality.

Main Methods:

• Estimation of growth and death rates for individual bacterial taxa.
• Measurement of bacterial generation times and lag times.
• Analysis of growth rate distributions and responses to resource amendment.

Main Results:

• Bacterial generation times averaged 5.04 days, with significant variation.
• Lag times were shorter in cultivated soils and decreased with resource amendment.
• A bimodal growth rate distribution was observed, with distinct fast- and slow-growing clusters.
• Both clusters grew faster in successional soils; resource amendment benefited the slow-growing cluster.

Conclusions:

• Land use shapes bacterial life history strategies, leading to distinct growth and mortality patterns.
• Bacterial communities exhibit 'boom-and-bust' dynamics, with high growth correlating with high mortality.
• Copiotrophic bacteria can be subdivided into life history groups with independent responses to environmental changes.
• Competitive dynamics and resource availability modulate bacterial growth rates in situ.