Nitrogen deposition suppresses soil respiration by reducing global belowground activity

Area of Science:

• Soil Science
• Ecology
• Biogeochemistry

Background:

• Soil respiration (Rs) is a key indicator of belowground biological activity.
• Increased nitrogen (N) deposition is a global change factor with uncertain impacts on Rs.
• Previous research suggests a negative effect of N deposition on Rs, but mechanisms are unclear.

Purpose of the Study:

• To investigate the global effects of nitrogen addition on soil respiration.
• To elucidate the mechanisms driving the relationship between N addition and Rs.
• To understand how environmental factors modulate N addition's impact on Rs.

Main Methods:

• Utilized a global dataset of 262 N addition experiments.
• Employed structural equation modeling (SEM) to analyze response variations.
• Assessed impacts on soil pH, root biomass, and microbial biomass.

Main Results:

• N addition effects on Rs shifted from positive to negative with increasing rate and duration.
• Decreases in soil pH, root biomass, and microbial biomass were associated with higher N addition.
• Root biomass had the strongest negative influence on Rs, with soil pH mediating effects.
• Lower background soil pH amplified negative impacts, exacerbating Rs decline.

Conclusions:

• Predicting belowground biological activity responses to global change requires understanding complex, multivariate pathways.
• Integrative approaches considering soil properties, plants, and microbes are crucial.
• Nitrogen deposition's impact on soil respiration is complex and context-dependent.