Land use and climatic factors structure regional patterns in soil microbial communities

Area of Science:

• Soil microbiology
• Ecology
• Biogeography

Background:

• Understanding soil microbial community composition and productivity at large spatial scales is limited.
• Emerging patterns exist for macroorganisms, but drivers for soil microbes remain unclear.

Purpose of the Study:

• To identify factors influencing soil microbial community composition and biomass across biogeographical provinces and regions.
• To test the hypothesis that land use and climate are key drivers.

Main Methods:

• Phospholipid fatty acid analysis was used to compare microbial communities.
• Samples were collected across eight land-use types in California, USA (n = 1117).

Main Results:

• Land-use type was the primary driver of microbial composition and biomass, linked to water availability and disturbance.
• Soil moisture influenced microbial groups: dry soils favored Gram-negative bacteria and fungi; wet soils favored Gram-positive, anaerobic, and sulfate-reducing bacteria.
• Microbial biomass was lowest in the wettest and driest soils; disturbed soils showed less fungal and more Gram-positive bacterial biomass.

Conclusions:

• Distinct soil microbial communities are associated with land-use types and disturbance at regional scales.
• Soil water availability is a key determinant of microbial community composition.
• Agricultural management (e.g., flooding, tillage, irrigation) can significantly impact soil microbial communities, potentially more than elevation or precipitation gradients.